dosimetry system for sit...2 dosimetry system for sit: manual for gafchromic® film 2.2....

Dosimetry System for SIT

Manual for Gafchromic® film

The originating Section of this publication in the IAEA was:

Insect Pest Control Section International Atomic Energy Agency

Wagramer Stasse 5 P.O. Box 100

A-1400 Vienna, Austria

DOSIMETRY SYSTEM FOR SIT: MANUAL FOR GAFCHROMIC ® FILM

© IAEA, 2004

FOREWORD The IAEA, through its Food and Agriculture programme, supports the development of the sterile insect technique (SIT) which utilizes ionising radiation to induce sterility in insectary reared insects that can then be released in the wild to control a pest population. The SIT has been successfully employed in a number of insects over more than 40 years, and is constantly being developed for new pests. Ionising radiation as a means of inducing sterility has a number of advantages over the alternative of chemical sterilization and currently is universally used in operational programmes. An incorrect dose of radiation however will reduce the impact of the released insects. Control of dose is therefore important in all stages from the initial research to operational programmes, and this requires an accurate, reliable dosimetry system. Species targeted by SIT programmes are typically major pests affecting agriculture or human health, so the assurance by standardized dosimetry that insects have been properly irradiated is of crucial importance to agricultural growers, agricultural regulators, public health officials and the public. Examination of the available literature indicates that there is no one dosimetry system in common use for SIT, and indeed dosimetry is often neglected completely. There is a clear need for a dosimetry system that is simple enough to be operated without special laboratory facilities, provides adequate precision and is cheap enough to be used routinely for quality control as well as research. Selection of a suitable dosimetry system depends on several considerations, including dose range of interest, ease of measurement, the expertise available, environmental factors that can be important at the location of use, cost and uncertainty that is consistent with the process. Considering these factors, the Gafchromic® dosimetry system offers SIT practitioners and their clients with a relatively simple, low cost and accurate means of assessing absorbed dose. The dosimeter is a small (1 × 1 cm square), thin (~100 micron) film which changes colour under radiation. This colour change, which depends on the absorbed dose, is then measured by a photometric reader. This manual describes the operation of the Radiachromic ® reader FWT-92, but any photometric reader capable of measuring at 600 nm can be used with appropriate modifications to the procedures. Like almost all dosimetry systems, the performance of the Gafchromic® system is affected by environmental factors, such as temperature and time of analysis. The quality of dosimetry and hence the success of the sterilisation process thus depends on rigorously following this manual. This manual brings together in one document a description of the components of the Gafchromic® dosimetry system, the procedure for its characterisation, and its application to process validation and process control, together with references to the relevant standards, to provide a readily available, citable reference for use by both research workers and production facility managers. Even though this dosimetry system can be used for various types of radiation, including electrons, the procedures described in this manual are limited to gamma radiation emitted by either 60Co or 137Cs. This manual was developed by K. Mehta. The IAEA staff member responsible is A. G. Parker of the Agency’s Laboratories, Seibersdorf.

EDITORIAL NOTE

The use of particular designations of countries or territories does not imply any judgement by the publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and institutions or of the delimitation of their boundaries.

The mention of names of specific companies or products (whether or not indicated as registered) does not imply any intention to infringe proprietary rights, nor should it be construed as an endorsement or recommendation on the part of the IAEA.

CONTENTS

1. Introduction ....................................................................................................................1

2. Dosimetry system ...........................................................................................................1 2.1. General........................................................................................................................1 2.2. Radiachromic® reader................................................................................................2 2.3. Gafchromic® dosimeter film (HD-810).....................................................................5

3. Reliability through traceability.......................................................................................7 3.1. General........................................................................................................................7 3.2. Reference radiation field ............................................................................................9 3.3. Reference irradiation conditions...............................................................................10 3.4. Transfer-standard dosimeter .....................................................................................11 3.5. Dose rate ...................................................................................................................13 3.6. Frequency .................................................................................................................13

4. Characterisation of Gafchromic® dosimetry system ...................................................13 4.1. Calibration ................................................................................................................14 4.2. Lot homogeneity.......................................................................................................19 4.3. Uncertainty ...............................................................................................................19 4.4. Characteristics of the current lot of dosimeters ........................................................20

5. Dose distribution measurement (dose mapping) ..........................................................21 5.1. Objective...................................................................................................................21 5.2. Research application.................................................................................................21 5.3. Commercial application............................................................................................21 5.4. Reference location ....................................................................................................21

6. Process control..............................................................................................................22 6.1. General......................................................................................................................22 6.2. Routine dosimetry ....................................................................................................22 6.3. Process parameter monitoring ..................................................................................22 6.4. Radiation-sensitive indicators...................................................................................22

7. Documentation .............................................................................................................22

References ................................................................................................................................23

Bibliography .............................................................................................................................23

Appendix A – Modifications to the ‘Operations Manual’ of the Radiachromic® reader .......24

Appendix B – Recommended data forms for documentation ..................................................25

Appendix C – Providers of transfer-standard dosimeters.........................................................40

Dosimetry System for SIT: Manual for Gafchromic® film 1

1. INTRODUCTION

This publication is divided into three parts:

- description of the Gafchromic® dosimetry system, - characterization of the dosimetry system and establishing traceability to the

international measurement system, and - use of this dosimetry system for SIT projects.

The first part (consisting of Section 2) describes the two main components of the dosimetry system, namely the Gafchromic® film dosimeters and the Radiachromic® reader. It includes information about handling the film, its optical absorption behaviour and influence quantities (environmental parameters) that affect the performance of these film dosimeters. Also, it describes the procedure for set up and for routine optimal operation of the reader.

The second part (Sections 3 and 4) describes the procedures for characterization of the dosimetry system, and for establishing traceability to the international measurement system. Characterisation includes:

- calibration of the dosimetry system, - determination of the lot homogeneity, and - determination of uncertainty in the measured dose.

The third part (Sections 5 and 6) describes the use of this calibrated dosimetry system for irradiators likely to be used for irradiating insects either for research or commercial purposes. It reviews the procedures for carrying out dose mapping for process validation, as well as process control.

To assist the readers and add to its transparency, this manual also includes:

- all the data forms necessary for the procedures described in this document (in Appendix B),

- some typical data for the characterisation of the dosimetry system (these are based on actual data generated at the IAEA Seibersdorf Laboratory), and

- several figures and photographs of equipment and activities.

There is also an accompanying spreadsheet in Microsoft Excel 95 format available from the IAEA web site, containing all the forms, with formulas to do the necessary calculations automatically (the file contains no macros). Instructions are included in a separate document for the use of the spreadsheet.

This manual may be used by individual facilities to develop their standard operating procedure for dosimetry.

2. DOSIMETRY SYSTEM

2.1. General The dosimetry system consists of Gafchromic® film dosimeters, Radiachromic® reader and accessories.

2 Dosimetry System for SIT: Manual for Gafchromic® film

2.2. Radiachromic® reader1 The Radiachromic® reader FWT-92 is a photometric instrument for the read-out of radiochromic dosimetry films, such as Gafchromic®. It can read the optical density (OD) of the film for two wavelengths, 510 and 600 nm. However, only 600 nm shall be used for Gafchromic® films. The operation of the reader is simple and is described in Section 3 of the ‘Operations Manual’2. However, because the Radiachromic reader manual was developed for FWT films and not for Gafchromic® film dosimeters, there are some statements/procedures in the manual that are not relevant to Gafchromic® dosimetry system. Because of this, the main steps for the operation of the reader that are specific to Gafchromic® dosimetry system are given below.

2.2.1. Set up 1. Locate the reader

- in a clean and dust-free environment, - in a room where the temperature is between 20 and 35°C (preferably even

more uniform) throughout the year (because the OD value is affected by the dosimeter temperature during read-out, also see Section 2.3.5),

- in a location where there is no direct sunlight on it, - so that there is no air draft (such as that due to an air-conditioner or an open

window). 2. Check that the power/voltage supply is consistent with local requirements. 3. Turn the reader on. It takes about 30 minutes to stabilise. Make sure that the

dosimeter holder is in place in the reader. This procedure allows the holder temperature to attain a stable value. The OD value of the Gafchromic® film depends on the temperature during its measurement (see Section 2.3.5).

4. Adjustment of the absorption scale (HI/LO check): a) High end of the scale – Select the wavelength setting at 600 nm. Lift the

dosimeter holder slightly from its well, rotate it through about 45°, and then

1 Supplied by Far West Technology, Inc., California, U.S.A. Radiachromic is a registered trademark. 2 Operators are encouraged to read the entire Operations Manual carefully before using the reader. The recommended changes to the text of this manual, mainly due to the different dosimeter film, are given in Appendix A.

(a) (b) FIG. 1. Two positions of the reader dosimeter holder during the HI/LO check: (a) the holder blocksthe light beam completely thus providing infinite value of OD, notice that the holder is slightly raisedin this position, and (b) the holder lets the beam pass completely unhindered thus providing zero valueof OD.


release it (Fig. 1a). This position of the holder blocks the light path of the analysing beam completely and simulates an infinite OD. Adjust the ‘HI’ knob to just display 9999 (and not 0.999), approaching from low numbers like 3.000 This sets infinite OD or 0% transmission.

b) Low end of the scale – Now lift the holder again from its well slightly and rotate it back to its normal position and then release it (Fig. 1b). Adjust the ‘LO’ knob just to read 0.000, approaching from non-zero numbers. This sets 0 (zero) OD or 100% transmission. If the low value cannot be set, the lamp may be too dim or burnt out and needs replacement.

c) Repeat the above steps until both readings are correct, that is, no further adjustments are needed.

2.2.2. Routine operation for OD measurement 1. Ensure that the reader is set up according to Section 2.2.1. 2. Ensure that the selected wavelength is 600 nm. 3. Before any OD measurements, perform the HI/LO check and repeat it every 30

minutes during the measurement session. 4. Measure OD of the three neutral density (ND) filters3 at least once a day when the

reader is in use, preferably before starting the OD measurements on the dosimeters (Section 2.2.3).

5. Remove the dosimeter holder from its well, place the dosimeter in the holder and replace the holder in the well. For more details on handling the dosimeter, see Section 2.3.6.

6. Wait for about 30 seconds (no longer) and read the OD value. The last digit in the OD value may increase by 3 or 4 in the first 10 seconds. After this, there should not be any change in the OD value. Record the reading when there has been no change for 10 seconds or more. If the reading continues to change after more than 30 seconds the reader temperature has not yet stabilized. Return the holder to the reader (without the dosimeter) and leave for a further 30 minutes for the temperature to stabilize.

7. Remove the dosimeter from the holder. Use forceps to remove the dosimeter from the holder, taking care to grasp it by an edge. Do not grasp the dosimeter near its centre as this could scratch the film and affect the reading. See 2.3.6 Handling.

8. Always place the dosimeter holder in its well in the reader when not in use. This helps maintain the holder at a constant temperature, and also keeps dust out of the well and out of the light path.

2.2.3. Maintenance of the absorption scale

Use the set of three ND filters to check the consistent operation of the reader (absorption scale). This information shall be documented using the prescribed Form-SIT-1 (Appendix B).

1. Initially this should be done during the calibration of the dosimetry system (Section 4.1.2). Place each filter in the well of the reader replacing the dosimeter holder, and measure the OD. The nominal values are: 0.3 (for the filter marked yellow), 0.6 (green) and 1.1 (blue). The actual values will vary slightly from reader to reader.

3 Supplied by Far West Technology, Inc., California, U.S.A.


2. Subsequently, this check shall be carried out at least once a day when the reader is in use, preferably before the OD-measurement session begins. The OD values should be the same (the last digit may change by 1 or 2) as that during calibration of the dosimetry system. Different values indicate a potential problem with the reader. Refer to the Operations Manual of the reader for trouble shooting.

(a)

(b)

FIG. 2. Absorption spectra for Gafchromic® dosimeter material: (a) exposed and unexposed; (b) difference between the two spectra.

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2.3. Gafchromic® dosimeter film (HD-810)4 2.3.1. Description

Table I gives the structure and composition of the film (D. Lewis, I.S.P., personal communication). Table I. Structure and composition of Gafchromic ® HD-810 film.

Material Thickness Density Composition (atom %) (microns) (g/cm3) C H O N polyester film base 97 1.35 45.50 36.40 18.20 0.00 active layer 6.5 1.08 31.50 56.00 5.00 7.50 gelatine 0.75 1.2 23 53 8 16

2.3.2. Absorption spectrum The absorption spectra for the Gafchromic® dosimeter material for the wavelength region of relevance (500 – 800 nm) are given in Figs 2a and 2b (D. Lewis, I.S.P., personal communication). Figure 2a shows the spectrums for unirradiated as well as irradiated film. Figure 2b shows the difference spectrum between these two. The wavelength to be used for the present application is 600 nm.

2.3.3. Response The film is almost colourless and transparent before irradiation, and it turns blue almost instantaneously upon exposure to ionizing radiation. However, the OD of the film increases (the blue colour deepens) slightly with time after exposure; the rate of change decreases with time. After about 24 hours, the OD value becomes relatively stable at a value approximately 15 – 20% over its initial value (measured within a few minutes after exposure). This behaviour is illustrated in Fig. 3 for a dose of about 100 Gy (data from Seibersdorf laboratories). The intensity of the blue colour (OD) is a

4 Supplied by International Specialty Products (ISP), New Jersey, U.S.A. Gafchromic is a registered trade mark

0.0%

2.0%

4.0%

6.0%

8.0%

10.0%

12.0%

14.0%

16.0%

18.0%

0 12 24 36 48 60 72 84 96 108 120 132 144 156Hours since irradiation

% c

hang

e in

O.D

.

FIG. 3. Change of optical density (at 600 nm) with time for Gafchromic® dosimeter film. Approximatedose value was 100 Gy.


function of the radiation dose.

2.3.4. UV light There are no extreme measures to be taken to protect the dosimeter film against UV light. However, do not expose the films to direct sunlight, and keep exposure to room lights (especially fluorescent lights) to the minimum required to handle the films and for the measurements. Store the large film sheet in its envelope in a dark place when not handling it.

2.3.5. Temperature dependence The OD of the irradiated dosimeter film (for the same dose) depends on the temperature of the dosimeter during irradiation as well as while its OD is read. The irradiation temperature coefficient for Gafchromic® dosimeters is 0.73%/°C (Data Sheet - Gafchromic® Dosimetry Medium, I.S.P.); that is, the OD value increases by 0.73% for 1°C increase in the dosimeter temperature during irradiation (for the same dose). Because of this, either the temperature of the dosimeter during irradiation should be controlled or should be measured/estimated and its effect corrected for (more on this later in Section 4.1). The dependence of the OD on the dosimeter temperature during its read-out was determined by Li et al. [1]. However, such effects quite often vary from lot to lot. Some limited experiments carried out in the IAEA Laboratory indicate that the read-out temperature coefficient is about 0.7%/°C for the tested lot of dosimeters in the room-temperature range of 20-25°C. Because of this, it is essential that the ambient room temperature where the reader is located stays fairly constant through out the year.

2.3.6. Handling Handle the film with a pair of tweezers (preferably with fine points) so as not to leave any finger-prints on the film (Fig. 4). Finger-prints, scratches on the film surface, dirt or dust can affect the light absorption of the film. Also, the tweezers tips should touch only the edges of the film, away from the centre portion where the analysing light passes through it. The dosimeter film is purchased as a sheet of about 20 cm x 25 cm. However, the size that the dosimeter holder of the reader can accommodate is about 1 cm x 1 cm. The sheet needs to be cut in this size prior to taking readings. The film may be cut with a paper guillotine or with a sharp utility knife or single-edged razor blade and a plastic ruler. It is convenient to choose the correct size by placing the film

FIG 4. A pair of fine pointed tweezers is being used tohold the dosimeter film along one edge whilst placingit inside the reader dosimeter holder. Notice that thetweezers touch only the edge of the film to avoidscratching the centre of the film where the OD readingwill be taken.


sheet on a grid paper while cutting it. Wear thin polythene or latex (surgical) gloves for this activity to avoid leaving finger-prints on the film (Fig. 5). For ease of inserting the film in the dosimeter holder, cut the film slightly smaller, about 0.9 cm x 0.9 cm. Store the remaining sheet in its envelope when not in use. Do not store it for a long time in the same room with the irradiator. Use a small paper envelope to store each film dosimeter. Place the dosimeter in it and remove it only for OD measurement. It is recommended that you irradiate the dosimeter in the envelope when it is placed in the container with the pupae to keep the dosimeter free of any dust or other contamination. Also, record relevant identification/ information on the envelope, such as dosimeter identification, irradiation location, exposure time, conditions and date of irradiation. Do not write on the envelope with the film inside, as this may mark the film.

2.3.7. Background OD Measure the OD value of the unirradiated film for each lot of dosimeters. Cut 10 dosimeters from the dosimeter sheet. Measure the OD of each dosimeter following the procedure of Section 2.2.2, and record the values on Form-SIT-2 (Appendix B). Estimate the mean and the standard deviation for these 10 values. This mean value, taken as OD(bkgd), shall be applied to all dosimeters of the present lot (see Section 4.1.2). Enter this value and the date of measurement in Form-SIT-9.

If the lot lasts longer than 6 months, this measurement should be repeated and the OD(bkgd) value updated.

3. RELIABILITY THROUGH TRACEABILITY

3.1. General Reliability of dose measurement using the Gafchromic® dosimetry system mainly depends on:

1) consistently following the procedure described in this document, and

2) having the dose-rate measurement at a reference point that is traceable to a nationally or internationally recognised standard

Traceability is an ability to demonstrate by means of an unbroken chain of comparisons, which is known as a traceability chain, that a measurement is in agreement within acceptable limits of uncertainty with comparable nationally or

FIG 5. A sharp utility knife, a plastic ruler and a gridpaper under the film help to cut it conveniently intodesirable lengths. Apply a slight pressure on the rulerwith the other hand to keep the film from movingduring cutting. It is essential that a pair of thinsurgical gloves is used during this activity to avoidfingerprints.


internationally recognised standards. Thus, such traceability for the dose rate at a reference point is achieved by measuring it with a transfer-standard dosimeter that is traceable to these standards. This section describes the procedure for these measurements.

If there is more than one irradiator available, select the one providing the most convenient place for irradiating the dosimeters and where the temperature can be either controlled or measured more easily. The Gafchromic® dosimetry system is then calibrated by irradiating the dosimeters at various dose levels at the reference point.

FIG. 6. Typical dose-rate distribution in the irradiation chamber of a Nordion Gammacell-220. The values are normalised to 100 in the centre of the gamma field. Note that the field is most uniform in the centre. (Grid is at 2 cm intervals from the centre of the chamber). Redrawn from Nordion data.


Once the dosimetry system is calibrated it is ready to be used anywhere with almost any type of irradiator.

3.2. Reference radiation field Basically there are two types of irradiators that are used for SIT, either for research or for commercial irradiation. For both types, it is important that the dose is as uniform as possible at the reference point where the dose rate is to be established, and later where the Gafchromic® dosimeters are irradiated for calibration.

Self-contained irradiators: In this case, the radioactive source pencils or elements are generally arranged around the circumference of a cylinder and the sample to be irradiated is located within this cylindrical volume. For such a case, the sample/dosimeter receives radiation from all directions and thus the radiation field in the centre of this volume is quite uniform. Nordion or Sheppard Gammacell and Husman irradiators fall into this category. Gammacell has several 60Co pencils and thus the radiation field is more symmetrical and uniform compared to that for the Husman irradiator which has source pencils only at three locations around the circumference. Figure 6 shows a typical dose-rate distribution in air in the irradiation chamber of a Nordion Gammacell-220.

Panoramic irradiators: The source generally consists of several radioactive pencils arranged in a plane or as a single rod. For routine irradiation, either the sample is located stationary in front of this source, or it passes by or around the source. For this type of irradiator, the sample receives radiation from one side at a time. The spatial uniformity of dose for a stationary sample may be improved by either

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FIG. 7. Two dosimeter holder designs for use with different types of irradiators. Recommendedmaterial is PMMA. (a) for self-contained irradiators, note hole in the bottom that facilitates naturalair circulation; (b) for panoramic irradiators.


continuously rotating it during irradiation or turning it through 180º after half of the total irradiation time.

3.3. Reference irradiation conditions 3.3.1. Irradiation geometry

The placement of the dosimeters at a fixed reference point should be consistent to achieve reproducible results. This can be achieved by (i) using a specially designed dosimeter holder, and (ii) arranging a set of reference marks in the irradiator sample chamber so that the holder can be placed in exactly the same position each time.

Self-contained irradiators: Figures 7a and 8a show a dosimeter holder designed for this type of irradiator. It is made of PMMA (any polymeric material is acceptable) and is an open cylinder (like a cup) with the inside diameter (~ 26 mm) just large enough to accommodate three dosimeters, each being about 12 mm in diameter. The wall thickness (4 mm) of the holder is selected to provide the optimum amount of material for achieving electron equilibrium for 60Co gamma rays. This standard design is recommended for use in all Gammacell-220 irradiators. Such a holder can also be used for Husman irradiators containing 137Cs by modifying the design of the base to fit within the irradiation chamber. For both types of irradiators, the dosimeter holder should be located in the irradiation chamber so that the dosimeters are at the centre of the radiation field, where the dose rate is most uniform (Fig. 6). Also, some method should be available to position this holder reproducibly at the same location in the reference field; Figs. 9 and 10 show a standard support design for the Gammacell-220. For irradiation in a Gammacell-220, place this stand in the irradiation chamber and then place the dosimeter holder (Fig. 8a) securely on top of this. This ensures that the dosimeters placed in the holder are always at the same location in the radiation field, and if the dimensions are correct the centre of the dosimeters is at the centre of the radiation field.

Panoramic irradiators: Even though the sample (pupae container) may be moving past the radiation source for routine irradiation, it may be necessary in some cases that the dosimeters are stationary for the dose-rate measurement and also for calibration irradiations (Section 4.1). Figures 7b and 8b show a dosimeter holder designed for this

FIG. 8. Two types of dosimeter holders to accommodate three dosimeters for simultaneousirradiation: (a) this cylindrical (open cup) type is suitable for irradiation in self-contained irradiators like Gammacell and Husman-type, where the gamma source surrounds the dosimeters where the fieldis isotropic, and (b) this panoramic (flat) type holder is suitable for a plane or a rod source where the gamma field is unidirectional. These holders are made of PMMA.


type of source. It should preferably be located at approximately the same distance from the source as the sample generally is during routine irradiation (to experience similar dose rate). As mentioned above (Section 3.2), the holder should be rotated continuously during irradiation. Alternatively, it should be turned through 180º around the vertical axis after half the irradiation time. In this case, care should be taken to position the holder at the same location after rotation.

3.3.2. Irradiation temperature Because the response of nearly all dosimeters depends on the dosimeter temperature during irradiation, measure or estimate the dosimeter temperature during irradiation. Generally, the temperature should be determined within 2-3°C, and preferably it should be controlled.

3.4. Transfer-standard dosimeter There are several dosimetry laboratories that will issue and analyse traceable transfer-standard dosimeters suitable for the purpose. These are either primary standard dosimetry laboratories or other accredited dosimetry calibration laboratories. Some examples of such laboratories are given in Appendix C.

Generally these are liquid dosimeters contained in 12 mm diameter ampoules. For the procedure in this MANUAL it is assumed that a set of three such dosimeters will be irradiated together for dose-rate measurement. If the transfer dosimeters are of different dimensions, it may be necessary to re-design the dosimeter holders illustrated in Figs 7 and 8.

The irradiation time for these transfer-standard dosimeters should be adjusted for each facility depending on the dose rate, transit dose and the expected temperature rise. The objective would be to make the transit dose negligible (less than 0.5% of the dose given to the transfer dosimeters) without too much (<5°) rise in the temperature of the

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FIG. 9. Typical support design (stand) for dosimeter holder for use in a Gammacell. Recommendedmaterial is PMMA. Note several holes in the vertical tube to facilitate natural air circulation.


dosimeter during irradiation.

Ensure that the timer used for time measurement is calibrated with traceability. See the manufacturer’s documentation on how to check the timer accuracy.

If possible, control the dosimeter temperature during irradiation at 25ºC (or, ask the standards laboratory if it has a preference). Alternatively, measure the dosimeter temperature during irradiation. If an easy method (for example, thermocouples) for measuring the temperature during irradiation is not available, measure the temperature of the dosimeters just before irradiation (minimum temperature) and immediately after irradiation (maximum temperature) by temporarily introducing a standard thermometer inside the dosimeter holder next to the dosimeters. Record both of these temperature values and enter the information in the data sheet to be sent to the standards laboratory along with the irradiated dosimeters. If the dosimeter temperature was measured continuously, attach that information to the data sheet.

Use Form-SIT-3 for recording data for this procedure (Appendix B).

The standards laboratory will analyse the irradiated transfer dosimeters and return the results in form of a certificate containing the dose value as measured by the dosimeters and also information regarding uncertainty in this value. Enter this uncertainty value as udr in Form-SIT-9 (Appendix B).

FIG. 10. A cylindrical dosimeter holder (as shown in Fig. 8a) is firmly placed on a PMMA stand forirradiation in a Gammacell. This stand consists of a circular base plate that just fits in the irradiationchamber of the Gammacell. In the centre of this plate is a tube on which the dosimeter holder isplaced. The height of this tube should be such that, when the device is placed in the Gammacell, thecentre of the dosimeters coincides with the geometric centre of the radiation field. A mark may be placed on the base plate so that it is always placed in the same orientation in the irradiation chamberof the Gammacell. Also, a mark may be placed on the cylindrical dosimeter holder for reproduciblepositioning. A similar device must be used for a Husman irradiator so that the dosimeters (in the cylindrical dosimeter holder) can be consistently placed at the same position in the gamma field.


3.5. Dose rate Each laboratory then should calculate the dose rate from the dose value given in this certificate and the irradiation time (assuming that the transit dose is negligible), as follows:

Dose rate = Dose / Irradiation time; the dose rate may be expressed in kGy/hour,

Gy/min or Gy/s. Record this value of dose rate in Form-SIT-3. This value is valid for the specific

irradiation conditions employed and for the day of irradiation. However, it is independent of the irradiation temperature.

3.6. Frequency

The dose rate should be measured every three years, or sooner if any relevant part of the irradiation system is altered, such as replenishment of the source, or modification to movement mechanism or irradiation set up that can affect the dose rate.

4. CHARACTERISATION OF GAFCHROMIC® DOSIMETRY SYSTEM

Characterisation of a dosimetry system consists of: - calibration of the dosimetry system, - determination of the homogeneity of the dosimeter response for a lot, and - determination of total uncertainty in the measured dose value. Procedure for each of these is described below. Use Form-SIT-9 to list the various characteristics of the current lot of dosimeters.

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FIG.11. (a) Gafchromic® film holder and (b) the arrangement of three such holders in the cylindricaldosimeter holder. Note that all the three films are parallel (tangential) to the curved surface of thedosimeter holder.


4.1. Calibration Calibration of a dosimetry system consists of irradiating several dosimeters at specified dose levels, measuring the OD and determining the response for each dosimeter, and establishing a relationship between response and dose. Each of these steps is discussed below.

4.1.1. Irradiation Irradiate Gafchromic® dosimeters at the same reference point where the dose rate was determined, and with the same irradiation geometry using the same dosimeter holder. Figure 11a shows a standard design of film holder that is compatible with the geometries of dosimeter holders of Figs 7a and 7b. There are three such cylindrical film holders; identify them by writing A, B or C at the bottom (uncut end) of the holders with a felt pen. Cut three film strips (5 cm x 1 cm) and identify them by writing A, B or C at one end of each film with a felt pen. Insert the film strip (holding it with a pair of tweezers at the marked end) in the slot in the PMMA cylindrical film holder. Then insert three such film holders in the dosimeter holder (either Fig. 7a or 7b) for simultaneous irradiation similar to three transfer dosimeters. Arrange these film holders so that each film is parallel to the adjacent wall of the dosimeter holder as shown in Fig. 11b (also see Fig. 12). To keep the film holders from rotating within the dosimeter holder, you may place a small piece(s) of paper between them. For a flat dosimeter holder, the film holders should be placed so that the films are parallel to the largest face of the dosimeter holder.

For most insects, calibration irradiation should be performed at 6 dose levels nominally set at: 40, 80, 120, 160, 200 and 240 Gy. However for F1 sterility where higher doses are required use a larger interval between doses. Calculate the corresponding irradiation times as:

Irradiation time = Dose / Dose rate (of today)

The dose rate to be used here should be calculated from the most recent value measured (Section 3.5) and correcting for radioactive decay from that day till ‘today’. It is calculated as: Dose rate (of today) = Dose rate (Section 3.5) e-λ∆t , where, ∆t = decay time (in days), λ(60Co) = 3.5991x10-4 d-1 and λ(137Cs) = 6.3097x10-5 d-1. These decay constant values are based on half lives of 1925.5 days for 60Co, and 30.07 years for 137Cs.

Record the value of the dose rate (of today) and the irradiation times in Form-SIT-4A (Appendix B).

FIG. 12. Three film holders with Gafchromic®dosimeters are placed in a cylindrical holderfor irradiation in a Gammacell. Note that eachfilm holder is placed so that the film is parallel(tangential) to the curved surface of thedosimeter holder. For a flat dosimeter holder,the film holders should be placed so that thefilms are parallel to the longer face of thedosimeter holder.


Measure the dosimeter temperature throughout irradiation (Fig. 13). If this is not possible, measure the minimum temperature (just before starting irradiation) and the maximum temperature (immediately after irradiation) of the dosimeters (see Section 3.4 for details of how to measure these). Determine the effective dosimeter temperature, T(eff) for each irradiation:

for continuous measurements: T(eff) = average of all measurement values, for before/after measurements: T(eff) = T(minimum) + 2/3 (∆T) ,

where, ∆T = T(maximum) – T(minimum).

If possible, control the temperature so that T(eff) for all irradiations is within 2°C. Calculate the calibration temperature, T(cal) as the average of the six T(eff) values. This information is used later for correcting the measured response value for temperature effect. Record the temperature values in Form-SIT-4A (Appendix B).

4.1.2. Response determination After irradiation, cut three pieces (about 1 cm × 1 cm) from each strip starting from the unmarked end, so that each piece fits into the dosimeter holder of the Radiachromic® reader for OD measurement. Note that about 2 cm of film containing the identification mark is left over which is not used for OD measurement. Place each set (A, B, C), containing three 1 cm x 1 cm films and the left-over piece, in a separate envelope for safeguarding. Since the colour develops over some time, measure the OD of the dosimeters between 24 and 30 hours after irradiation (Section 2.3.3).

Check the high and low absorption scales every thirty minutes during the OD-measurement session, and adjust the ‘HI’ and ‘LO’ knobs if necessary (see Section 2.2.1).

Measure the OD of the three ND filters before starting the read-out of the dosimeters, and repeat after reading all the dosimeters. Record these values in Form-SIT-4B and Form-SIT-1 (Appendix B).

Measure the OD of each dosimeter film following the procedure given in Section 2.2.2. For each dosimeter set (A, B, and C), calculate the mean OD and the standard deviation for the three dosimeters, and record the values in Form-SIT-4B.

FIG. 13. Three dosimeters in a cylindrical dosimeterholder on a stand are prepared for irradiation in aGammacell. Thermocouples are used to measure thetemperature throughout the irradiation, where thethermocouple junction is located inside thedosimeter holder next to the dosimeters. A black tapeis used to hold the wires firm in position. The wiresleave the irradiation chamber through the centralaccess tube to the recording device situated outsidethe Gammacell.


Thus, for each dose level, there are three mean OD values.

Now, calculate the response (R) defined as the OD induced due to radiation:

R = OD(mean) – OD(bkgd)

where, OD(bkgd) is the mean value of the OD of the unirradiated film (Form-SIT-2) which is valid for the entire lot of dosimeters (see Section 2.3.7). Calculate the corrected response value for the temperature effect, R(corr) as:

R(corr) = R (1.0 – 0.0073 ∆T) where, ∆T = T(eff) – T(cal); (note, ∆T may be positive or negative).

For each dose level, calculate R(mean), the mean value of the three corrected response values. Again record these values in Form-SIT-4B.

4.1.3. Transit dose Transit dose is defined as the dose a sample or dosimeter receives while either the source is moving or the sample/dosimeter is moving. Transit time is then defined as:

Transit time = Transit dose / dose rate,

where, dose rate refers to its value at the stationary irradiation position.

Transit time is not the physical transit (or movement) time of the dosimeters (or source), which is to say the actual time the dosimeters take to go up and down. As an approximation, the transit time is one quarter of the actual time the dosimeters take to go up and down. If the transit dose is significant compared to the minimum dose of interest (namely, 40 Gy for SIT), it is essential that this value be added to the nominal dose values (40, 80, … 240 Gy, see Section 4.1.1) before the calibration relation is determined. We will assume here that if the transit time is less that 0.5% of the minimum irradiation time (i.e., 40Gy/dose rate), then the transit time(dose) may be ignored. For Gammacell-220 (Nordion), transit time is approximately 4 s, thus transit time(dose) may be ignored for those irradiators which have dose rate less than about 4 Gy/min. For other cases, a general procedure is given below for the estimation of transit dose (this procedure applies specifically to a Gammacell-type irradiator).

1. Following the procedure of Section 4.1.1, irradiate one set of dosimeters each for four irradiation time periods: T1, T2, T3 and T4 seconds (use Form-SIT-4C). If the transit time calculation is done simultaneously with the calibration (4.1.1.) the times and readings corresponding to 40, 80, 120 and 160 Gy from 4.1.1. may be used.

2. Read the dosimeter sets following the procedure of Section 4.1.2.

3. Plot ‘irradiation time’ on x-axis vs ‘R(mean)’ on y-axis for these four points. Determine the relationship using regression analysis.

4. Following the same procedure, irradiate two more sets of dosimeters. Irradiate the first set for T1 seconds (as before) plus N1 times with zero-time setting (0 seconds) on the timer. Thus, the amount of extra dose this dosimeter set receives compared to the set with irradiation time of T1 seconds is N1 × (transit


dose), which can be attributed to the extra irradiation time of N1 × (transit time). The second set is irradiated in a similar way; however the extra dose it is given is N2 × (transit dose). Typical values of N1 and N2 are 7 and 15. Any value may be used, but the transit dose determination is more accurate if T1+N2 approximates to T2.

5. Measure the response, R(mean) for these two sets of dosimeters following the procedure of Section 4.1.2 (use Form-SIT-4C).

6. For these two R(mean) values, determine the corresponding ‘irradiation time’ using the regression relationship developed in step 3 above. The values correspond to T1 + N1 × (transit time) and T1 + N2 × (transit time).

7. Calculate the value of the transit time by subtracting T1 from each of these two values and dividing the first value by N1 and the second value by N2. These two values should be similar (within a few %). The average of these two values is taken as ‘transit time’ for this irradiator. Enter this value in Form-SIT-4C. The value of the transit time does not change with the radioactive decay of the source. However it should be measured at least once in two years, and sooner if the timer or the movement mechanism is modified.

8. Calculate ‘transit dose’ = ‘transit time’ × dose rate (of today). Enter this value in Form-SIT-4C.

9. Add this value of ‘transit dose’ to each of the 6 nominal dose values (namely, 40, 80, .. 240 Gy), and enter these ‘Actual dose’ values in Form-SIT-4D.

4.1.4. Calibration relationship

First, copy values of ‘R(corr)’ and ‘R(mean)’ from Form-SIT-4B to Form-SIT-4D.

The objective here is to determine the relationship between the dosimeter response and the dose. This can be done graphically or with regression analysis.

For graphical analysis, plot ‘R(mean)’ on the y-axis vs ‘Actual dose’ on the x-axis as given in Form-SIT-4D. Draw a smooth curve through all the six points. This curve may be slightly non-linear.

If regression analysis is employed, use the three ‘R(corr)’ values (as y-parameter) for each ‘Actual dose’ value (x-parameter). The relationship is almost linear, but quadratic fit may be better. The calibration relationships may be described as:

Linear function: Response = a + b (Dose)

Quadratic function: Response = c + d (Dose) + e (Dose)2

The selection between the two can be made by observing the distribution of the percentage residuals for the two cases following the procedure given below (use Form-SIT-4E):

1. Calculate Dcalc for each of the three response values (R(corr)) for all six irradiations (as given in column 3 of Form-SIT-4D):

Linear function: Dcalc = (Response – a) / b


Quadratic function: Dcalc = (1/2e) [– d ± {d2 – 4e (c – Response)}1/2]

Enter these values in Form-SIT-4E, column 2 or 4.

2. Determine the percentage residual for each point as: Residual(%) = 100 × (Dcalc – Dactual) / Dactual

where, Dactual is the actual value of the delivered dose (as given in column 1 of Form-SIT-4E). Note: Residual(%) value may be positive or negative.

3. Record these values of ‘Residual(%)’ in Form-SIT-4E (column 3 or 5). 4. Plot ‘Residual(%)’ (on y axis) vs ‘Actual dose’ (on x axis) for the linear as well as

for the quadratic fit. 5. Select the relationship that yields random distribution of the residual values as a

function of dose. If both show similarly random distribution, select the linear function as the calibration relationship.

This calibration relationship is valid for the specific lot of dosimeters for one year, and for the temperature employed for the irradiations, T(cal). Enter the date of calibration, the calibration irradiation temperature, T(cal) and the calibration relationship in Form-SIT-9. Calculate the root-mean-square residual (ufit) value for the selected calibration relationship, as follows: ufit = {Σ(Residual(%))2 / n}1/2, where, n is the total number of residual values (18 in this case), and the summation to be carried over all these n (=18) values. Record this value in Form-SIT-9. This value represents the uncertainty arising from the fitting procedure and will be used later in Section 4.3.

4.1.5. Frequency The dosimetry system should be calibrated once a year, or sooner if any part of the dosimetry system is changed, such as, new lot of dosimeters or repairs to the reader. (Note: a lamp change in the reader does not require re-calibration).

4.1.6. Use of the calibration relationship

To measure dose at a point, follow the procedure given below. Use Form-SIT-5 for this procedure. Irradiation: 1. Place one 1cm x 1cm dosimeter (or several) from the calibrated lot at each point

of interest. Use an envelope for the dosimeter(s) and write the relevant identification and information on the envelope. More than one dosimeter may be placed in one envelope.

2. Irradiate the sample (with the dosimeters). 3. Estimate the temperature (T(eff)) of the dosimeter during irradiation (Section

4.1.1). OD measurements (Note: These measurements are made 24 to 30 hours after

irradiation):


4. Turn the reader on and wait for at least 30 minutes with the dosimeter holder in place in the reader for its temperature to stabilise.

5. Check the high and low absorption scales and adjust the ‘HI’ and ‘LO’ knobs if necessary; repeat this procedure every thirty minutes during the OD-measurement session (see Section 2.2.1).

6. Measure the OD of the three ND filters at least once a day preferably before starting the measurements with the dosimeter films, and record the values on Form-SIT-5 and Form-SIT-1. Compare these OD values with those measured during the calibration of the dosimetry system. Different values indicate a problem with the reader.

7. Remove the dosimeter(s) from the envelope and measure its OD following the procedure of Section 2.2.2.

8. Determine the response, R = OD(measured) – OD(bkgd). Note: If more than one dosimeter are used at one point, calculate the average value of R.

9. If the temperature during routine measurements is not the same as T(cal) (that is, the value during the calibration procedure), a correction needs to be applied as follows (also see Section 4.1.2): R(corr) = R (1.0 – 0.0073 x ∆T), where, ∆T = temperature of irradiation – T(cal).

10. Determine the dose using the value of ‘R(corr)’ and the calibration relationship determined in Section 4.1.4.

4.2. Lot homogeneity

It is important to determine the degree of homogeneity of response for dosimeters belonging to a lot since it affects the overall precision of the measured dose value. For each lot of dosimeters, this is determined by irradiating several dosimeters selected randomly from the lot to the same dose, following the procedure given below:

1. Cut nine dosimeters from the dosimeter film sheet (current lot). 2. Place these dosimeters in three small envelopes for irradiation (three dosimeters per

envelope). 3. Place these three envelopes together at a location inside a container full of pupae

(or similar material) where the dose is expected to be uniform (for example, at the centre of the container).

4. Irradiate them at about 100 Gy dose. The exact values of dose and irradiation temperature are not important. However, it is very important that they all receive the same dose at the same temperature.

5. Determine the response of each dosimeter following points 4 to 8, Section 4.1.6. Record these values in Form-SIT-6 (Appendix B).

6. Calculate the mean and standard deviation of these nine response values. Determine coefficient of variation:

CV(%) = (standard deviation/mean value) × 100. Record these values in the Form-SIT-6. Record the value of CV(%) as ulot in Form-SIT-9. The lower the CV(%) value the higher (better) the precision of the measured dose value.

4.3. Uncertainty In general, the result of any measurement is only an approximation or estimate of the value of the measurand (for example, absorbed dose), and thus is complete only when accompanied by a statement of the uncertainty of that estimate. Uncertainty (of measurement) may be defined as a parameter, associated with the measurand, that


characterises the distribution of the values that could reasonably be attributed to the measurand. Thus, uncertainty reflects the degree of accuracy in the measured value.

Uncertainty in any measurement is a fact of life and unavoidable. First, the sources of uncertainty should be identified, and their effects minimised as much as possible. And then the remaining sources of uncertainty should be evaluated. This is most easily done by considering in turn each step in the calibration and use of a dosimeter, and assessing what uncertainties are likely to be associated with each step. The uncertainty associated with a dose measurement can then be calculated by combining the individual components together. The philosophy used is to ascribe to each component of uncertainty an effective standard deviation, known as a standard uncertainty, and these standard uncertainties are then combined to produce the total uncertainty.

The total uncertainty in the measured dose value using the Gafchromic dosimetry system consists of several components (all these components are in %): - udr : arising from uncertainty in the dose rate value (from certificate from the

standards laboratory, see Section 3.4), - ufit : arising from uncertainty in the calibration relationship (see Section 4.1.4), - ulot : arising from lot non-homogeneity (= CV(%) value from Form-SIT-6, see

Section 4.2). If n dosimeters are used at one location to measure dose, the uncertainty in the mean value is reduced by √n. Thus, this component of uncertainty for n dosimeters = CV(%)/√n.

- utemp-i : arising from uncertainty in the irradiation temperature during dose measurement. As discussed in Section 4.1.2, the measured dosimeter response is corrected for irradiation temperature if it is different than that during calibration. However, if the irradiation temperature is not known accurately this procedure introduces uncertainty in the correction applied. Assuming that the ‘effective’ dosimeter temperature during irradiation is known to be between Tmin and Tmax, utemp-i = 0.73{(Tmax – Tmin)/2}/√6. The factor of √6 is based on the assumption that the effective temperature has triangular probability distribution within the two limits [2]. Calculate this value and record it in Form-SIT-9.

- utemp-r : arising from uncertainty in the dosimeter temperature during OD read-out procedure. Assuming that the dosimeter temperature during read-out is within ±5°C of the temperature during calibration, utemp-r = 0.7x5/√3 where, 0.7%/°C is the read-out temperature coefficient as estimated in the IAEA Laboratory. The factor of √3 is based on the assumption that the dosimeter temperature has rectangular probability distribution within the two limits [2]. Calculate this value and record it in Form-SIT-9.

The total uncertainty, utotal (%) is then given by adding these components in quadrature:

utotal = (udr2 + ufit

2 + ulot2 + utemp-i

2 + utemp-r2)1/2

All these values of u are for 1 standard deviation (σ). However, to imply a higher level of confidence that the ‘true’ value lies within the reported range, utotal should be multiplied by a factor of 2 (called a ‘coverage factor’). Thus, one can state with about 95% confidence that the ‘true’ dose value lies within Dmeasured ± 2utotal.

4.4. Characteristics of the current lot of dosimeters Enter the values determined above for the following characteristics in Form-SIT-9:


- ID of the lot of dosimeters, - calibration of the dosimetry system, - background response, - uncertainty values.

5. DOSE DISTRIBUTION MEASUREMENT (DOSE MAPPING)

5.1. Objective The primary purpose of performing dose mapping is to verify that the dose variability in the irradiated sample is acceptable for the application on hand. This should be done before useful irradiation is carried out. If the distribution is wider than acceptable, it points out the need for modifying the irradiation procedure or the container size/shape. This activity is generally referred to as ‘Process Qualification’ since it establishes values of all process parameters necessary to achieve the specified dose in the sample. See Section 6.3 and Form-SIT-8B for examples of process parameters.

Use Form-SIT-7 for recording data.

5.2. Research application If pupae are irradiated for research purpose, such as to establish the relationship between dose and its effectiveness, it is inherently essential that the dose is as uniform as possible across the irradiated sample. To measure the dose distribution in the sample, place several dosimeters (or a strip of film) in the sample container. The dosimeters should be protected in paper envelopes against contact with pupae.

5.3. Commercial application For commercial applications, generally larger volumes are irradiated, and thus dose is not as uniform as for small volumes used for research applications. Dose variation is unavoidable, and the main objective of dose mapping is to determine the maximum and minimum dose in the container and the regions where these occur. Carry out detailed dose determination by carefully placing several dosimeters through out the irradiated volume. Place dosimeters in a specific regular grid pattern, however place more dosimeters in regions where extreme doses are expected from previous experience or from theoretical analysis. If some portion of the pupae is receiving dose too high or too low for the application at hand, some changes need to be carried out before large-scale irradiation is done.

5.4. Reference location For process control during routine irradiation, it is necessary to place dosimeters in or on the product (pupae) container (see Section 6.2). They are preferably placed at a point where the dose is expected to be minimum. However, it is not always convenient to do so. Alternatively, a dosimeter(s) may be placed at a reference location on the product container that is convenient. During the dose mapping exercise, select such a reference location and establish the relationship between the dose at this point and the minimum dose in the product. To reduce uncertainty in the process, the dose gradient at this reference location should not be significant.


6. PROCESS CONTROL

6.1. General Carry out routine irradiation as per information gathered during the dose mapping exercise; that is, ensure that the values of all the process parameters are the same as established during process qualification (Section 5.). Thus, it is expected that the dose distribution would be acceptable. On the other hand, it is necessary to have in place some measures of process control to show with a high degree of confidence that the entire process was carried out as specified. This is accomplished through two independent procedures: a) routine dosimetry, and b) monitoring of process parameters. Besides, use of radiation-sensitive indicators assists in streamlining the inventory process. These process control measures should be supported by assays of the level of sterility achieved where appropriate.

6.2. Routine dosimetry For each irradiation batch, place at least three dosimeters (in one envelope) at the location where the dose is expected to be minimum or at the reference location identified during process qualification (Section 5.4). Thus, if the dose value (mean of the three values) measured by these dosimeters is acceptable (as established during process qualification), then it can be concluded that the particular irradiation batch has received the expected dose. Use Form-SIT-8A for recording data (Appendix B). Each laboratory should determine for itself what constitutes an irradiation batch and how many such measurements should be performed per batch.

6.3. Process parameter monitoring Control, monitor and document all process parameters that can affect dose throughout the process (irradiation). Such parameters include: container size, any specific arrangement of the product/pupae within the container, positioning of the container, irradiation time/conveyor speed, rotation of the container (if applicable), and source location. Use Form-SIT-8B for recording data (Appendix B).

6.4. Radiation-sensitive indicators Appropriate radiation-sensitive indicators should be placed on each container before irradiation. Check the state of the indicator before and immediately after irradiation. Use of these indicators assists in keeping irradiated and unirradiated containers apart. However, there should also be administrative procedures in place to identify the irradiated samples/containers. These indicators are not replacement for routine dosimeters. Routine dosimeters are absolutely essential as discussed in Section 6.2.

7. DOCUMENTATION

Document all information collected during the various procedures described above and file it together at an easily accessible location. This is necessary for research applications as well as for commercial applications. Prepare and use appropriate forms to make this consistent, such as those given in Appendix B. Operators should sign and date these forms and file them as an integral part of quality assurance for audit purposes.


REFERENCES

[1] LI, Z., et al., A study of dosimetry characteristics of GAF DM-1260 radiochromic films, Radiat. Phys. Chem. 57 (2000) 103-113.

[2] (ISO) INTERNATIONAL ORGANIZATION FOR STANDARDIZATION, ‘Guide to the Expression of uncertainty in measurement’, ISBN 92-67-10188-9, Switzerland, 1995

BIBLIOGRAPHY

Standards ISO/ASTM 51275 Practice for the Use of a Radiochromic Film Dosimetry System ISO/ASTM 51539 Guide for Use of Radiation-Sensitive Indicators ISO/ASTM 51900 Guide for Dosimetry in Radiation Research on Food and Agricultural

Products ISO/ASTM 51940 Guide for Dosimetry for Sterile Insect Release Programs ISO/ASTM 52116 Practice for Dosimetry for a Self-Contained Dry-Storage Gamma-Ray

Irradiator ASTM E-1026 Practice for Using the Fricke Reference Standard Dosimetry System Other publications INTERNATIONAL ATOMIC ENERGY AGENCY, Dosimetry for food irradiation,

Technical Reports Series no. 409, IAEA, Vienna, Austria (2002). http://www-pub.iaea.org/MTCD/publications/PDF/TRS409_scr.pdf

INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Recommendations of the International Commission on Radiological Protection, ICRP Publication 26, Pergamon Press, New York (1997).


Appendix A – Modifications to the ‘Operations Manual’ of the Radiachromic® reader

A.1 Section 2, Paragraph 2, replace the first 2 sentences by the following: Gafchromic® film has a polyester base of 97 µm(microns), 6.5 µm of active layer and

0.75 µm of gelatine. Thus, the total thickness is about 104 µm (≈ 0.1 mm). A.2 Figure 1 is not representative of Gafchromic® dosimetry system. A.3 Section 3.2, replace the text under the NOTE by the following: There are no extreme measures to be taken to protect the dosimeter film against UV

light. However, do not expose the films to direct sunlight, and keep exposure to room lights (especially fluorescent lights) to the minimum required in order to handle the films and for the measurements. Store the large film sheet(s) in their envelope after each use.

A.4 Section 4, point 4. For Gafchromic® dosimeter, the OD is not divided by its thickness

because the thickness is constant for all the dosimeters.

A.5 Section 5.1, points 1-8. Replace this text by Section 4.1 of this S.O.P.

A.6 Section 5.2. not relevant. A.7 Sections 5.3.2 and 5.3.3. not relevant.


Appendix B – Recommended data forms for documentation B.1 Form-SIT-1 Neutral density filter OD measurements B.2 Form-SIT-2 Background OD for the lot of dosimeters B.3 Form-SIT-3 Dose rate measurement with transfer-standard dosimeters B.4 Form-SIT-4A Gafchromic® dosimetry system calibration: Irradiation

Form-SIT-4B Gafchromic® dosimetry system calibration: Response determination Form-SIT-4C Gafchromic® dosimetry system calibration: Transit dose determination Form-SIT-4D Gafchromic® dosimetry system calibration: Relationship Form-SIT-4E Gafchromic® dosimetry system calibration: Residual behaviour

B.5 Form-SIT-5 Dose determination B.6 Form-SIT-6 Homogeneity for the lot of dosimeters B.7 Form-SIT-7 Dose mapping B.8 Form-SIT-8A Process control: Routine dosimetry Form-SIT-8B Process control: Process parameter monitoring B.9 Form-SIT-9 Characteristics of the current lot of dosimeters


Form-SIT-1 Neutral Density Filter OD Measurements Note: Check and adjust the absorption scale before ND filter measurements (Section 1.2.1).

Date Time Optical Density (OD) Remarks Measured by ND1 ND2 ND3 Yellow Green Blue

Just before dosimetry system calibration

Just after dosimetry system calibration


Form-SIT-2 Background OD for the Lot of Dosimeters Note: Check and adjust the absorption scale before these measurements.

Lot ID : Date : Dose : 0 (zero) Gy Measured by :

Dosimeter OD (600 nm)

1

2

3

4

5

6

7

8

9

10

Mean OD1

Standard Dev

1 OD(bkgd) = Mean OD for the present lot of dosimeters

Note: This value is valid for 6 months only. If the lot lasts longer, these measurements should be repeated.


Form-SIT-3 Dose Rate Measurement with transfer-standard Dosimeters Note: Also attach here copies of the data sheets sent to the standards laboratory

Date : Irradiated by :

Transfer Dosimeter set number

Reference field

Irradiator

Dosimeter holder ID

Holder location

Irradiation temperature (°C)

Controlled? Yes No

Measured value Before = °C ; After = °C ; Other …….

Irradiation time 1, 2

Dose rate 3

1 when and how was the timer calibrated:

2 Is this measurement based on an automatic timer? Yes No If it is done manually, when was the timer started and stopped ? 3 Dose rate = Dose (from standards laboratory certificate, Section 3.5) / Irradiation time Note: It is assumed that transit dose is negligible compared to the dose value

When was the dose rate measured last time: Were the irradiation conditions the same? What was the value then? Any other remarks:


Form-SIT-4A Gafchromic® Dosimetry System Calibration: Irradiation

Date : Reference field and dosimeter holder: (should be the same as those used for the dose rate measurement with transfer dosimeter (Form-SIT-3) Dose rate (of today) (from Section 4.1.1) : Irradiated by :

Nominal Dose

(Gy) Irradiation

Time1,2, 3 Min. Temp.

(°C) Max. Temp.

(°C) T(eff)4

(°C)

40

80

120

160

200

240

1 For example, Irradiation time = 40 Gy/dose rate (of today) 2 when and how was the timer calibrated:

3 Is this measurement based on an automatic timer? Yes No If it is done manually, when was the timer started and stopped ? 4 T(eff) = T(minimum) + 2/3 {T(maximum) – T(minimum)}

T(cal) = average of the six T(eff) values =


Form-SIT-4B Gafchromic® Dosimetry System Calibration: Response Determination Note: - Check and adjust the absorption scale every 30 minutes.

- Measure the OD values for the three ND filters just before and just after the following measurements and enter the values here and in Form-SIT-1.

Date : Analysed by : OD of the three ND filters (before the measurements): , , . OD of the three ND filters (after the measurements) : , , .

OD OD Response1 R(corr)2 R(mean)3Nominal Dose (Gy)

OD 3 values for each strip (mean) (std dev) (R)

A: 40 B: C: A: 80 B: C: A: 120 B: C: A: 160 B: C: A: 200 B: C: A: 240 B: C: 1 Response, R = OD (mean) – OD (bkgd), where OD (bkgd) is from Form-SIT-2 2 R(corr) = R(1.0 – 0.0073 x ∆T), where ∆T = T(eff) – T(cal), where T(eff) and T(cal) are from Form-

SIT-4A. 3 R(mean) = Average of the three R(corr) values in column 6 NOTE: Calculate the coefficient of variation (CV) for each dosimeter set (A, B and C) as: CV (%) = {OD(std dev)/OD(mean)} x 100 This value should be less than 2%.


Form-SIT-4C Gafchromic® Dosimetry System Calibration: Transit Dose Determination Note: - Check and adjust the absorption scale every 30 minutes.



Irrad. Time

OD 3 values for each strip

OD (mean)

OD (std dev)

Response1

(R) R(corr)2 R(mean)3

A: T1 B: C: A: T2 B: C: A: T3 B: C: A: T4 B: C: A: T1 + N1×TT B: C: A: T1 + N2×TT B: C: 1 Response, R = OD (mean) – OD (bkgd), where OD (bkgd) is from Form-SIT-2 2 R(corr) = R(1.0 – 0.0073 x ∆T), where ∆T = T(eff) – T(cal), where T(eff) and T(cal) are determined

for this set of irradiations 3 R(mean) = Average of the three R(corr) values in column 6 NOTE: T1, T2, T3 and T4 are the times set on the automatic timer. If the irradiation chamber is operated manually, the time period is the one during which the chamber is stationary in the irradiation position. Transit time = Transit dose (on date ………………) = Transit time x dose rate (of today) =


Form-SIT-4D Gafchromic® Dosimetry System Calibration: Relationship

Date : Calibration temperature, T(cal) : Analysed by :

Nominal dose (Gy) Actual dose (Gy)1 R(corr) R(mean) A: 40 B: C: A: 80 B: C: A: 120 B: C: A: 160 B: C: A: 200 B: C: A: 240 B: C: 1 Actual dose = Nominal dose + transit dose Graphical Analysis:

Plot ‘Actual dose’ on x-axis and ‘R(mean)’ on y-axis Regression Analysis:

Y-variable = R(corr) (column 3), thus there are three y-values for each x-value. X-variable = Actual dose. Fit the data to linear as well as quadratic relationship.

Attach all the graphs to this Form.


Form-SIT-4E Gafchromic® Dosimetry System Calibration: Residual behaviour For regression analysis

Date : Analysed by :

Actual dose1 Linear Relationship Quadratic Relationship

(Gy) Dcalc 2 Residual(%)4 Dcalc

3 Residual(%)4 A: A: A: A: B: B: B: B: C: C: C: C: A: A: A: A: B: B: B: B: C: C: C: C: A: A: A: A: B: B: B: B: C: C: C: C: A: A: A: A: B: B: B: B: C: C: C: C: A: A: A: A: B: B: B: B: C: C: C: C: A: A: A: A: B: B: B: B: C: C: C: C:

1 Values from column 2, Form-SIT-4D. 2 Dcalc = Calculated dose for the corresponding value of ‘R(corr)’ from Form-SIT-4D, and

using the linear calibration relationship. 3 Dcalc = Calculated dose for the corresponding value of ‘R(corr)’ from Form-SIT-4D, and

using the quadratic calibration relationship. 4 Residual(%) = 100 x (Dcalc – Dactual) / Dactual ,

Note: Residual(%) value may be positive or negative.

Plot ‘Residual(%)’ as y-parameter and ‘Actual dose’ as x-parameter for each relationship.

Select the relationship that yields random distribution of the residual values as a function of dose. If both show similar random distribution, select the linear function as the calibration relationship.



Form-SIT-5 Dose Determination

Date : Lot ID : Calibration relationship : From Section 4.1.4 Operator : OD of the three ND filters (before the measurements): , , . OD of the three ND filters (after the measurements) : , , .

Dosimeter1 Temp(°C)2 OD3 Respo.4 R(corr)5 Dose(Gy)6 Remarks7 1 Identification of the dosimeter. This information should also appear on the small envelope in

which the dosimeter was irradiated and where it is stored. 2 Estimated temperature of the dosimeter during irradiation. 3 Measured OD of the dosimeter. 4 Response = measured OD – OD(bkgd) 5 Corrected Response (for temperature) = Response(column 4) [1.0 – 0.0073 x ∆T] where, ∆T = Temperature (column 2) – T(cal) 6 Dose calculated using R(corr) from column 5 and the calibration relationship (from Section

4.1.4). 7 Enter information re: product run, product batch, location of dosimeter, etc.


Form-SIT-6 Homogeneity for the Lot of Dosimeters Note: Check and adjust the absorption scale before these measurements.

Lot ID : Date : Dose : approximately 100 Gy Analysed by :

Dosimeter Response (600 nm)

1 2 3 4 5 6 7 8 9 Mean Response Standard Deviation Coefficient of Variation (%)1

1 CV(%) = {standard deviation/mean value} × 100

NOTE: This value should be less than 2%.


Form-SIT-7 Dose Mapping

Date : Application : Research Commercial Product : Container : Analysed by : OD of the three ND filters (before the measurements): , , . OD of the three ND filters (after the measurements) : , , .

Dosimeter1 Temp(°C)2 OD3 Respo.4 R(corr)5 Dose(Gy)6 Remarks7 Reference For routine monitor NOTE: This is the same form as Form-SIT-5, except that there should be a dosimeter(s) at a ‘reference’ location which will be later used for routine monitoring (see Section 5.4). 1 Identification of the dosimeter. This information should also appear on the small envelope in

which the dosimeter was irradiated and where it is stored. 2 Estimated temperature of the dosimeter during irradiation. 3 Measured OD of the dosimeter. 4 Response = measured OD – OD(bkgd) 5 Corrected Response (for temperature) = Response(column 4) [1.0 – 0.0073 x ∆T] Where, ∆T = Temperature (column 2) – T(cal) 6 Dose calculated using R(corr) from column 5 and the calibration relationship (from Section

4.1.4). 7 Enter information re: product, location of dosimeter, etc.


Form-SIT-8A Process Control: Routine Dosimetry

Date : Irradiation batch/run ID : Analysed by : OD of the three ND filters (before the measurements): , , . OD of the three ND filters (after the measurements) : , , .

Dosimeter1 Temp(°C)2 OD3 Respo.4 R(corr)5 Dose(Gy)6 Remarks7 Reference location Minimum dose NOTE: This is the same form as Form-SIT-5 and -7. However, the dosimeters are placed either at the location of minimum dose or at the reference location identified during dose mapping (see Section 5.4 and Form-SIT-7) 1 Identification of the dosimeter. This information should also appear on the small envelope in

which the dosimeter was irradiated and where it is stored. 2 Estimated temperature of the dosimeter during irradiation. 3 Measured OD of the dosimeter. 4 Response = measured OD – OD(bkgd) 5 Corrected Response (for temperature) = Response(column 4) [1.0 – 0.0073 x ∆T] Where, ∆T = Temperature (column 2) – T(cal) 6 Dose calculated using R(corr) from column 5 and the calibration relationship (from Section

4.1.4). 7 Enter information re: irradiation batch, product, location of dosimeter, etc.


Form-SIT-8B Process Control: Process Parameter Monitoring

Date : Irradiation batch/run ID : Operator :

Please add any other process parameters that are relevant to your process Parameter Description / Value Species Bulk density of the insects Source location Container size Product arrangement in the container Container location Container rotated ? No Yes Speed = Irradiation duration / Conveyor speed


Form-SIT-9 Characteristics of the Current Lot of Dosimeters Lot ID: Calibration of Gafchromic® dosimetry System (Section 4.1.4) Date of calibration (valid for one year) Calibration temperature, T(cal) Relationship Background Response (Section 2.3.7) Date of measurement (valid for 6 months) OD(bkgd) Uncertainty values (Section 4.3) Arising from dose rate (Section 3.4) udr (%) = date = Arising from calibration (Section 4.1.4) ufit (%) = date = Arising from lot non-homogeneity (4.2) ulot (%) = date = Arising from irradiation temperature (4.3) utemp-i (%) = date = Arising from read-out temperature (4.3) utemp-r (%) = date = Total uncertainty1 utotal (%) =

1 The total uncertainty is the sum in quadrature of the individual uncertainty terms utotal = (udr

2 + ufit2 + ulot

2 + utemp-i2 + utemp-r

2)1/2


Appendix C – Providers of transfer-standard dosimeters

Examples of standards laboratories from where traceable transfer-standard dosimeters can be obtained. This is not an exhaustive list and does not constitute a recommendation by the IAEA. Primary Standard Dosimetry Laboratories

Centre for Ionizing Radiation Metrology National Physical Laboratory Teddington, Middlesex United Kingdom, TW11 0LW Tel: +44 20 8977 3222 Fax: +44 20 8943 6680 E-mail: [email protected] or [email protected] http://www.npl.co.uk/ionrad/services/mail.html

Ionizing Radiation Division

National Institute of Standards and Technology Gaithersburg MD U.S.A. 20899 Stephen M. Seltzer Tel: 301/975–555, E–mail: [email protected] Marc F. Desrosier Tel: 301/975–5639, E-mail: [email protected] James M. Puhl Tel: 301/975–5581, E–mail: [email protected]

Accredited Dosimetry Calibration Laboratories

Risø High Dose Reference Laboratory Risø National Laboratory Building NUK-201 Frederiksborgvej 399, P.O. 49, DK-4000 Roskilde, Denmark Tel: +45 4677 4677, Fax: +45 4677 5688, [email protected] MDS Nordion Ion Technologies Customer Service Department 447 March Road Ottawa, Ontario, K2K 1X8 Canada Tel: +1 613 592 2790 Tel: +1 800 465 3666 (North America Only) Fax: +1 613 592 6937 E-mail: [email protected]

Appendix B - Recommended data forms for documentation B.1 Form-SIT-1 Neutral density filter OD measurements B.2 Form-SIT-2 Background OD for the lot of dosimeters B.3 Form-SIT-3 Dose rate measurement with IDAS alanine dosimeters B.4 Form-SIT-4A Gafchromic® dosimetry system calibration: Irradiation

Form-SIT-4B Gafchromic® dosimetry system calibration: Response determination Form-SIT-4C Gafchromic® dosimetry system calibration: Transit dose determination Form-SIT-4D Gafchromic® dosimetry system calibration: Relationship Form-SIT-4E Gafchromic® dosimetry system calibration: Residual behaviour

B.5 Form-SIT-5 Dose determination B.6 Form-SIT-6 Homogeneity for the lot of dosimeters B.7 Form-SIT-7 Dose mapping B.8 Form-SIT-8A Process control: Routine dosimetry Form-SIT-8B Process control: Process parameter monitoring B.9 Form-SIT-9 Characteristics of the current lot of dosimeters

Form-SIT-1

Neutral Density Filter OD Measurements Note: Check and adjust the absorption scale before ND filter measurements (Section 1.2.1).

Date Time Optical Density (OD) Remarks Measured by ND1

Yellow ND2 Green

ND3 Blue

Just before dosimetry system calibration

Just after dosimetry system calibration

Form-SIT-2

Background OD for the Lot of Dosimeters Note: Check and adjust the absorption scale before these measurements.

Lot ID : Date : Dose : 0 (zero) Gy Measured by :

Dosimeter OD (600 nm)

1

2

3

4

5

6

7

8

9

10

Mean OD1

Standard Dev

1 OD(bkgd) = Mean OD for the present lot of dosimeters

Note: This value is valid for 6 months only. If the lot lasts longer, these measurements should be repeated.

Form-SIT-3

Dose Rate Measurement with IDAS Alanine Dosimeters Note: Also attach here copies of the two IDAS data sheets

Date : Irradiated by :

IDAS Dosimeter set number

Reference field

Irradiator

Dosimeter holder ID

Holder location

Irradiation temperature (°C)

Controlled? Yes No

Measured value Before = °C ; After = °C ; Other …….

Irradiation time 1, 2

Dose rate 3

1 when and how was the timer calibrated:

2 Is this measurement based on an automatic timer? Yes No If it is done manually, when was the timer started and stopped ? 3 Dose rate = Dose (from IDAS certificate, Section 3.5) / Irradiation time Note: It is assumed that transit dose is negligible compared to the dose value

When was the dose rate measured last time: Were the irradiation conditions the same? What was the value then? Any other remarks:

Form-SIT-4A

Gafchromic® Dosimetry System Calibration: Irradiation

Date : Reference field and dosimeter holder: (should be the same as those used for the dose rate measurement with alanine (Form-SIT-3) Dose rate (of today) (from Section 4.1.1) : Irradiated by :

Nominal Dose

(Gy) Irradiation

Time1,2, 3 Min. Temp.

(°C) Max. Temp.

(°C) T(eff)4

(°C) 50 80 120 160 200 240

1 For example, Irradiation time = 50 Gy/dose rate (of today) 2 when and how was the timer calibrated:

3 Is this measurement based on an automatic timer? Yes No If it is done manually, when was the timer started and stopped ? 4 T(eff) = T(minimum) + 2/3 {T(maximum) – T(minimum)}

T(cal) = average of the six T(eff) values =

Form-SIT-4B

Gafchromic® Dosimetry System Calibration: Response Determination Note: - Check and adjust the absorption scale every 30 minutes.



Nominal Dose (Gy)


OD (mean)

OD (std dev)

Response1

(R) R(corr)

2 R(mean)3

A: 50 B: C: A:

80 B: C: A:

120 B: C: A:

160 B: C: A:

200 B: C: A:

240 B: C:

1 Response, R = OD (mean) – OD (bkgd), where OD (bkgd) is from Form-SIT-2 2 R(corr) = R(1.0 – 0.0073 x ∆T), where ∆T = T(eff) – T(cal), where T(eff) and T(cal) are from Form-SIT-

4A. 3 R(mean) = Average of the three R(corr) values in column 6 NOTE: Calculate the coefficient of variation (CV) for each dosimeter set (A, B and C) as: CV (%) = {OD(std dev)/OD(mean)} x 100 This value should be less than 2%.

Form-SIT-4C

Gafchromic® Dosimetry System Calibration: Transit Dose Determination Note: - Check and adjust the absorption scale every 30 minutes.



Irrad. Time


OD (mean)

OD (std dev)

Response1

(R) R(corr)

2 R(mean)3

A: T1 B:

C: A:

T2 B: C: A:

T3 B: C: A:

T4 B: C: A:

T1 + N1•TT B: C: A:

T1 + N2•TT B: C:

1 Response, R = OD (mean) – OD (bkgd), where OD (bkgd) is from Form-SIT-2 2 R(corr) = R(1.0 – 0.0073 x ∆T), where ∆T = T(eff) – T(cal), where T(eff) and T(cal) are determined for this

set of irradiations 3 R(mean) = Average of the three R(corr) values in column 6 NOTE: T1, T2, T3 and T4 are the times set on the automatic timer. If the irradiation chamber is operated manually, the time period is the one during which the chamber is stationary in the irradiation position. Transit time = Transit dose (on date ………………) = Transit time x dose rate (of today) =

Form-SIT-4D

Gafchromic® Dosimetry System Calibration: Relationship

Date : Calibration temperature, T(cal) : Analysed by :

Nominal dose (Gy) Actual dose (Gy)1 R(corr) R(mean)

A:

50 B:

C:

A:

80 B:

C:

A:

120 B:

C:

A:

160 B:

C:

A:

200 B:

C:

A:

240 B:

C: 1 Actual dose = Nominal dose + transit dose Graphical Analysis:

Plot ‘Actual dose’ on x-axis and ‘R(mean)’ on y-axis Regression Analysis:

Y-variable = R(corr) (column 3), thus there are three y-values for each x-value. X-variable = Actual dose. Fit the data to linear as well as quadratic relationship.


Form-SIT-4E

Gafchromic® Dosimetry System Calibration: Residual behaviour For regression analysis

Date : Analysed by :

Actual dose1 Linear Relationship Quadratic Relationship

(Gy) Dcalc 2 Residual(%)4 Dcalc

3 Residual(%)4 A: A: A: A: B: B: B: B: C: C: C: C: A: A: A: A: B: B: B: B: C: C: C: C: A: A: A: A: B: B: B: B: C: C: C: C: A: A: A: A: B: B: B: B: C: C: C: C: A: A: A: A: B: B: B: B: C: C: C: C: A: A: A: A: B: B: B: B: C: C: C: C:

1. Values from column 2, Form-SIT-4D. 2. Dcalc = Calculated dose for the corresponding value of ‘R(corr)’ from Form-SIT-4D, and using the

linear calibration relationship. 3. Dcalc = Calculated dose for the corresponding value of ‘R(corr)’ from Form-SIT-4D, and using the

quadratic calibration relationship. 4. Residual(%) = 100 x (Dcalc – Dactual) / Dactual ,

Note: Residual(%) value may be positive or negative.

Plot ‘Residual(%)’ as y-parameter and ‘Actual dose’ as x-parameter for each relationship. Select the relationship that yields random distribution of the residual values as a function of dose. If both show similar random distribution, select the linear function as the calibration relationship. Attach all the graphs to this Form.

Form-SIT-5

Dose Determination

Date : Lot ID : Calibration relationship : From Section 4.1.4 Operator : OD of the three ND filters (before the measurements): , , . OD of the three ND filters (after the measurements) : , , .

Dosimeter1 Temp(°C)2 OD3 Respo.4 R(corr)5 Dose(Gy)6 Remarks7

1. Identification of the dosimeter. This information should also appear on the small envelope in which the

dosimeter was irradiated and where it is stored. 2. Estimated temperature of the dosimeter during irradiation. 3. Measured OD of the dosimeter. 4. Response = measured OD – OD(bkgd) 5. Corrected Response (for temperature) = Response(column 4) [1.0 – 0.0073 x ∆T]

where, ∆T = Temperature (column 2) – T(cal) 6. Dose calculated using R(corr) from column 5 and the calibration relationship (from Section 4.1.4). 7. Enter information re: product run, product batch, location of dosimeter, etc.

Form-SIT-6

Homogeneity for the Lot of Dosimeters Note: Check and adjust the absorption scale before these measurements.

Lot ID : Date : Dose : approximately 100 Gy Analysed by :

Dosimeter

Response (600 nm)

1

2

3

4

5

6

7

8

9

Mean Response

Standard Deviation

Coefficient of Variation (%)1

1 CV(%) = {standard deviation/mean value} x 100

NOTE: This value should be less than 2%. If it is more, report to the Scientific Secretary of the CRP

Form-SIT-7

Dose Mapping

Date : Application : Research Commercial Product : Container : Analysed by : OD of the three ND filters (before the measurements): , , . OD of the three ND filters (after the measurements) : , , .


Reference For routine monitor

NOTE: This is the same form as Form-SIT-5, except that there should be a dosimeter(s) at a ‘reference’ location which will be later used for routine monitoring (see Section 5.4). 1. Identification of the dosimeter. This information should also appear on the small envelope in which the


Where, ∆T = Temperature (column 2) – T(cal) 6. Dose calculated using R(corr) from column 5 and the calibration relationship (from Section 4.1.4). 7. Enter information re: product, location of dosimeter, etc.

Form-SIT-8A

Process Control: Routine Dosimetry

Date : Irradiation batch/run ID : Analysed by : OD of the three ND filters (before the measurements): , , . OD of the three ND filters (after the measurements) : , , .


Reference location

Minimum dose

NOTE: This is the same form as Form-SIT-5 and -7. However, the dosimeters are placed either at the location of minimum dose or at the reference location identified during dose mapping (see Section 5.4 and Form-SIT-7) 1. Identification of the dosimeter. This information should also appear on the small envelope in which the


Where, ∆T = Temperature (column 2) – T(cal) 6. Dose calculated using R(corr) from column 5 and the calibration relationship (from Section 4.1.4). 7. Enter information re: irradiation batch, product, location of dosimeter, etc.

Form-SIT-8B

Process Control: Process Parameter Monitoring

Date : Irradiation batch/run ID : Operator :

Please add any other process parameters that are relevant to your process

Parameter Description / Value

Species

Bulk density of the insects

Source location

Container size

Product arrangement in the container

Container location

Container rotated ? No Yes Speed =

Irradiation duration / Conveyor speed

Form-SIT-9

Characteristics of the Current Lot of Dosimeters Lot ID: 7726-09 (Gafchromic® dosimeter sheets received from the IAEA) Calibration of Gafchromic® System (Section 4.1.4)

Date of calibration (valid for one year)

Calibration temperature, T(cal)

Relationship

Background Response (Section 2.3.7)

Date of measurement (valid for 6 months)

OD(bkgd)

Uncertainty values (Section 4.3)

Arising from dose rate (Section 3.4) udr (%) = date =

Arising from calibration (Section 4.1.4) ufit (%) = date =

Arising from lot non-homogeneity(4.2) ulot (%) = date =

Gafchromic Dosimetry System for SIT Reporting Form

Form-SIT-1

Neutral Density Filter OD MeasurementsNote: Check and adjust the absorbtion scale before ND filter measurements (Section 1.2.1)

Reader serial number: Filter setting 600 nm

Date Time Optical Density (OD) Remarks OperatorND1 ND2 ND3

Yellow Green BlueJust before dosimetry system calibrationJust after dosimetry system calibration

Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture


Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture

Microsoft Excel Workbook for Dosimetry Calculations

To accompany “Dosimetry System for SIT: Manual for Gafchromic® film”

1.3

1 06/06/19

Contents Contents .............................................................................................................................1 Introduction .......................................................................................................................1 Form SIT 1.........................................................................................................................2 Form SIT 2.........................................................................................................................3 Form SIT 3.........................................................................................................................4 Form SIT 4A......................................................................................................................5 Form SIT 4B......................................................................................................................6 Form SIT 4C......................................................................................................................7 Form SIT 4D......................................................................................................................8 Form SIT 4E ....................................................................................................................10 Form SIT 5.......................................................................................................................11 Form SIT 6.......................................................................................................................12 Form SIT 7.......................................................................................................................13 Form SIT 8A & B ............................................................................................................14 Form SIT 9.......................................................................................................................16

Introduction The spreadsheet file dosimetry_v13.xls provides a simple way to perform all the calculations required in the Dosimetry System for SIT: Manual for Gafchromic® film. The workbook is organised in the same manner and following the sequence of the recommended data forms contained in Appendix B of the manual. All places where entries are required are indicated by cells highlighted with yellow. Either single forms or the complete workbook can be printed to provide a permanent record.

2 06/06/19

Form SIT 1

This form merely provides a convenient format for recording the neutral density filter readings. Record the serial number of the Radiachromic reader you are using at the head of the form. Readings should be taken at the start and finish of each session of taking OD readings.

3 06/06/19

Form SIT 2

This calculates the mean and standard deviation of the background OD measurements. The date must be entered correctly as this is used later to check that this measurement is still valid.

4 06/06/19

Form SIT 3

Use this form to record the irradiation conditions for the transfer standard dosimeters and the subsequent results. Also record the type of source you are using, 60Co or 137Cs using the buttons at the top of the sheet. The half-life will be entered automatically allowing the spreadsheet to calculate the dose rate for any day.

5 06/06/19

Form SIT 4A

Enter the date at the head and the required calibration dosages in column A. The calibration dosages should be adjusted to span the expected operational dose. For fruit flies and tsetse which use 120 Gy the calibration dosages should range from 40 to 240 Gy. For Lepidoptera, which require dosages in the range 250 – 500 Gy depending on species, the calibration dosages should range from 100 to 600 Gy If the calibration data has been entered (Form SIT 3) the sheet will calculate the required irradiation times. These exact times may be used, or convenient times close to these values. Enter the actual times used in column C and the minimum and maximum temperature of the dosimeters during each exposure in columns E and F. The effective temperatures will be used to correct the dosimeter response readings by the appropriate temperature compensation, and the mean of all the temperatures will become the reference temperature for all future readings T(ref). Also record information about the timer at the foot of the sheet.

6 06/06/19

Form SIT 4B

When the calibration dosimeters are read, 24 to 30 hours after exposure, enter the readings for each dosimeter strip as appropriate. The OD(mean), OD(std dev), CV(%), response, corrected response and mean corrected response for each dose will be calculated.

7 06/06/19

Form SIT 4C

For the determination of transit dose, enter the times T1 - T4 in seconds and the constants N1 and N2 appropriate for your irradiator set up in column T. The value of T1 – T4 should match the lowest four doses from SIT4A. The values of N1 and N2 should be chosen such that T1 plus N1 times the estimated transit time is approximately equal to T2, with N2 twice N1. Enter the dosimeter OD values in columns V – X. The actual transit time will be calculated, and the graph of the relationship displayed. If the dose rate of your machine is less than 4 Gy/min the effect of the transit dose will be insignificant. In this case you may choose not to perform the transit dose calculation by clicking on the appropriate button at the top right of this sheet; the transit time will be set to zero and you may proceed with the next step. This button will only work if the dose rate is less than 4 Gy/min.

8 06/06/19

Form SIT 4D

This form is completed automatically, with the actual dose taking into account the transit time. Using the mean corrected response the spreadsheet calculates linear, quadratic and power regression fits, and the residuals for each.

9 06/06/19

Select the fit which gives a random arrangement of the residuals. In this example the power series fit produces a noticeable pattern in the residuals and should not be used. If more than one fit gives a random arrangement for preference select the linear fit.

10 06/06/19

Form SIT 4E

When you have chosen an appropriate fit, select it with the buttons at the top of Form SIT 4E. The rest of this form shows the residuals for the three possible fits. This completes the calibration of the system. At this point the spreadsheets SIT 1, SIT 2, SIT 3 and SIT 4 should be printed and stored as part of the record for quality control audit purposes.

11 06/06/19

Form SIT 5

This form is used for determining the dose actually received during routine treatment. The date and desired dose are entered at the head of the form and the calculated exposure time (allowing for the transit time) is calculated. The routine monitoring dosimeter readings are then entered in column D, with the exposure temperature in C and the actual dose recorded by the dosimeter is indicated in column G.

The spreadsheet will warn you if the background OD measurement (6 months) or system calibration (12 months) are out of date.

12 06/06/19

Form SIT 6

This form is for checking the homogeneity of the dosimeter batch. When the target dose is entered in C9 the approximate exposure time is calculated (C11). The exact time (dose) used however is not critical for the batch homogeneity, but should be close to the normal exposure dose used in routine treatment. After irradiating a set of three dosimeter strips, record the OD values on the form. The Coefficient of variation will be calculated.

13 06/06/19

Form SIT 7

Use this form to record the data from a dose mapping exercise. Unless you have multiple thermocouple thermometers available you will have to estimate a single temperature for all the dosimeters to enter in column B. A warning also appears on this sheet if either calibration is out of date.

14 06/06/19

Form SIT 8A & B

The Form SIT 8A is similar to forms SIT 5 and 7, but records the dosimeter readings either from the reference location, minimum dose point or other location (see Manual section 5.4, page 23). It provides for up to three dosimeters placed together in one location, allowing the readings to be average to give a lower uncertainty.

The spreadsheet will warn you if the background or system calibration is out of date.

15 06/06/19

Form SIT 8B records process parameters. These two sheets together (SIT-8A & SIT-8B) should be complete for each shipment of insects send from the rearing facility and a copy included with the shipment.

16 06/06/19

Form SIT 9

Insert the date when the dosimeter Lot was received at the head of the form. Form SIT 9 brings together information on the calibration of the system and the uncertainty in the dose values arising from various sources. These include dose rate uncertainty (from the transfer dosimeter reading), uncertainty in the Gafchromic® film calibration, and from non-homogeneity in the dosimeters. The main remaining uncertainty arises from determining the temperature of the dosimeter at the time of irradiation. The measured temperature of the dosimeters entered on the forms SIT 5, 6 or 7 are used to compensate for differences in the response of the dosimeter at different temperatures, but if the temperature is not constant during irradiation the response of the dosimeter will be varying during the exposure and this gives rise to additional uncertainty. Measure with a thermocouple thermometer or estimate the likely maximum range of dosimeter temperature during irradiation and enter the maximum and minimum temperature of a typical exposure. This is then used to estimate the uncertainty due to temperature variation. An overall uncertainty Utotal is calculated from these uncertainty terms. Utotal is an estimate of the standard deviation of the dose estimation by your system, and can be used to provide confidence intervals for the point estimate of dose. The 95% confidence interval is approximately ±2 x Utotal.


Form-SIT-1Neutral Density Filter OD MeasurementsNote: Check and adjust the absorbtion scale before ND filter measurements (Section 1.2.1)

Reader serial number: 3312 Filter setting 600 nm

Date Time Optical Density (OD) Remarks OperatorND1 ND2 ND3Yellow Green Blue

2005-10-09 10:15 0.297 0.599 1.103Just before dosimetry system calibration AGP

2003-10-09 11:40 0.297 0.598 1.104Just after dosimetry system calibration AGP

2005-04-12 09:50 0.297 0.599 1.105 Background reading AGP

2005-05-14 10:20 0.297 0.598 1.103 AGP

Joint FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture


Form-SIT-2Background OD for the Batch of DosimetersNote: Check and adjust the absorbtion scale before ND filter measurements (Section 1.2.1)

Lot ID: 7026-09

Date: 2005-04-12

Dose: 0 (zero) Gy

Operator: AGP

Dosimeter OD (600 nm)1 0.0862 0.0873 0.0884 0.0835 0.0856 0.0877 0.0878 0.0869 0.08510 0.085

Mean OD1 0.086Standard Dev 0.001

1 OD(bkgd) = Mean OD for the present batch of dosimetersNote: This value is valid for 6 months only. If the batch last longer, these measurements should be repeated.



Form-SIT-3Dose Rate Measurement with Transfer Standard DosimetersNote: Also attach here copies of the data sheets

Date: 2000-04-05

Operator: AGP Halflife 1925.5 days

Dosimeter type set number IDAS alanine 146-00-66Reference field

Irradiator Gammacell 220Dosimeter holder ID 1Holder location Field centre

Irradiation Temperature (°C)Controlled? Yes No XMeasured Before= 23 After= 23 Other

Irradiation time (secs)1,2 1200Dose from reading certificate 616.0 GyDose rate3 0.513 Gy/secDose rate uncertainty [udr(%)] 1.7 %

1 How and when was the timer calibrated: Not calibrated - quartz2 Is the measurement based on an automatic timer? YesIf it is done manually, when was the time started and stopped?

3 Dose rate = Dose (from reading certificate, Section 2.4)/Irradiation timeNote it is assumed that the transit dose is negligible compared to the dose valueWhen was the last time the dose rate was measured:Same irradiation conditions?What was the value then?Any other remarks:

60Co 137Cs


Gafchromic Dosimetry System for SIT Reporting FormForm-SIT-4A

Gafchromic Dosimetry System Calibration: IrradiationDate: 2003-10-09Reference field and dosimeter holder: Field centre, holder 1(should be the same as those used for the dose rate measurement with alanine (Form-SIT-3))

Dose rate of today (from section 3.1): 0.324Operator: Ouatara

Dose (Gy) Calculated Irrad Actual Irrad. Nominal Min. Temp. Max. Temp Temp(eff)3time (sec) time (sec)1,2 Dose

40 124 125 40.5 21.0 23.0 22.380 247 250 80.9 24.0 23.5 23.7120 371 370 119.7 23.0 23.0 23.0160 494 490 158.6 22.5 22.5 22.5200 618 620 200.6 22.0 22.0 22.0240 742 740 239.5 22.0 22.0 22.0

T(cal)= 22.61 When and how was the timer calibrated Not calibrated

2 Is this measurement based on an automatic timer? Yes

If it is done manually, when was the timer started and stopped? Automatic

3 Temp(eff) = Temp(min) + 2/3{T(max) - T(min)}

Range of Temp(eff) , from the last column = 22.0023.67


Gafchromic Dosimetry System for SIT Reporting FormForm-SIT-4B

Gafchromic Dosimetry System Calibration: Response DeterminationNote: Check and adjust the absorbtion scale every 30 minutes.

Measure the OD values for the three ND filters just before and just after the following measurements and enter the values here and in Form-SIT-1

Date: 2003-10-09Analysed by: OuataraOD of the three ND filters Before the measurements: 0.296 0.590 1.122After the measurements:

Dose OD OD OD CV(%) Resp.1 R(corr)2 R(mean)3(Gy) 3 values for each strip (mean) (std dev) (R)40 A: 0.246 0.250 0.249 0.248 0.0021 0.8% 0.162 0.16340 B: 0.251 0.249 0.250 0.250 0.0010 0.4% 0.164 0.164 0.16440 C: 0.249 0.248 0.250 0.249 0.0010 0.4% 0.163 0.16381 A: 0.408 0.422 0.410 0.413 0.0076 1.8% 0.327 0.32581 B: 0.405 0.410 0.409 0.408 0.0026 0.6% 0.322 0.320 0.32181 C: 0.408 0.403 0.410 0.407 0.0036 0.9% 0.321 0.319120 A: 0.553 0.559 0.556 0.556 0.0030 0.5% 0.470 0.469120 B: 0.541 0.551 0.550 0.547 0.0055 1.0% 0.461 0.460 0.465120 C: 0.554 0.558 0.547 0.553 0.0056 1.0% 0.467 0.466159 A: 0.701 0.706 0.711 0.706 0.0050 0.7% 0.620 0.620159 B: 0.692 0.703 0.710 0.702 0.0091 1.3% 0.616 0.616 0.617159 C: 0.702 0.693 0.704 0.700 0.0059 0.8% 0.614 0.614201 A: 0.849 0.851 0.854 0.851 0.0025 0.3% 0.765 0.769201 B: 0.847 0.851 0.854 0.851 0.0035 0.4% 0.765 0.768 0.772201 C: 0.854 0.870 0.863 0.862 0.0080 0.9% 0.776 0.780239 A: 0.993 0.996 1.012 1.000 0.0102 1.0% 0.914 0.918239 B: 0.996 0.998 1.005 1.000 0.0047 0.5% 0.914 0.918 0.924239 C: 1.020 1.009 1.024 1.018 0.0078 0.8% 0.932 0.936

1 Response = OD(mean) - OD(bkgd), where OD(bkgd) is from FORM-SIT-22 R(corr) = R(1.0 - 0.0073 x ∆T), where ∆T = T(eff) - T(cal), where T(eff) and T(cal)

are from Form-SIT-4A3 R(mean) = Average of the three response values in column 5

NOTECalculate the coefficient of variation (CV) for each dosimeter strip (A, B and C) as:CV(%) = {OD(std dev)/OD(mean)} x 100This value should be less than 2%


Gafchromic Dosimetry System for SIT Reporting FormForm-SIT-4C

Gafchromic Dosimetry System Calibration: Transit Dose DeterminationNote: Check and adjust the absorbtion scale every 30 minutes.

Measure the OD values for the three ND filters just before and just after the following measurements and enter the values here and in Form-SIT-1

Date: 2003-10-09Analysed by: Ouatara

OD of the three ND filters Before the measurements: 0.296 0.590 1.122After the measurements:

Time (sec) OD OD OD Resp.1 R(corr)2 R(mean)3Temp 3 values for each strip (mean) (std dev) (R)

T1 125 A: 0.246 0.250 0.249 0.248 0.0021 0.162 0.163B: 0.251 0.249 0.250 0.250 0.0010 0.164 0.165 0.164

Temp 22.0 C: 0.249 0.248 0.250 0.249 0.0010 0.163 0.164T2 250 A: 0.408 0.422 0.410 0.413 0.0076 0.327 0.325

B: 0.405 0.410 0.409 0.408 0.0026 0.322 0.319 0.321Temp 23.8 C: 0.408 0.403 0.410 0.407 0.0036 0.321 0.318T3 370 A: 0.553 0.559 0.556 0.556 0.0030 0.470 0.469

B: 0.541 0.551 0.550 0.547 0.0055 0.461 0.460 0.465Temp 23.0 C: 0.554 0.558 0.547 0.553 0.0056 0.467 0.466T4 490 A: 0.701 0.706 0.711 0.706 0.0050 0.620 0.620

B: 0.692 0.703 0.710 0.702 0.0091 0.616 0.616 0.617Temp 22.5 C: 0.702 0.693 0.704 0.700 0.0059 0.614 0.614T1 125 A: 0.293 0.294 0.280 0.289 0.0078 0.203 0.203+N1 7 B: 0.289 0.290 0.286 0.288 0.0021 0.202 0.203 0.204Temp 22.3 C: 0.300 0.289 0.288 0.292 0.0067 0.206 0.207T1 125 A: 0.336 0.332 0.330 0.333 0.0031 0.247 0.247+N2 15 B: 0.333 0.322 0.330 0.328 0.0057 0.242 0.243 0.245Temp 22.3 C: 0.329 0.338 0.325 0.331 0.0067 0.245 0.245

1 Response = OD(mean) - OD(bkgd), where OD(bkgd) is from FORM-SIT-22 R(corr) = R(1.0 - 0.0073 x ∆T), where ∆T = T(eff) - T(cal), where T(eff) and T(cal)

are from Form-SIT-4A3 R(mean) = Average of the three response values in column 5

NOTECalculate the coefficient of variation (CV) for each dosimeter strip (A, B and C) as:CV(%) = {OD(std dev)/OD(mean)} x 100This value should be less than 2%

Transit time= 4.5 seconds

Transit dose calculationCalculate transit doseDon't calculate transit dose



Transit time calculation

0.0

0.1

0.2

0.3

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0.7

0 100 200 300 400 500 600Time (Seconds)

O.D.

Calibration pointsRegression fitTransit dose points


Gafchromic Dosimetry System for SIT Reporting FormForm-SIT-4D

Gafchromic Dosimetry System Calibration: RelationshipDate: 2003-10-09Irradiation Temperature: 22.0 23.7

range of Temp(eff) from Form-SIT-4A

Operator: OuataraTransit time: 4.5 secTransit dose: 1.454 Gy

Nominal Dose Actual Dose Corrected R(mean)(Gy) (Gy)1 Response40.5 41.9 A: 0.16340.5 41.9 B: 0.164 0.16440.5 41.9 C: 0.16380.9 82.4 A: 0.32580.9 82.4 B: 0.320 0.32180.9 82.4 C: 0.319119.7 121.2 A: 0.469119.7 121.2 B: 0.460 0.465119.7 121.2 C: 0.466158.6 160.0 A: 0.620158.6 160.0 B: 0.616 0.617158.6 160.0 C: 0.614200.6 202.1 A: 0.769200.6 202.1 B: 0.768 0.772200.6 202.1 C: 0.780239.5 240.9 A: 0.914239.5 240.9 B: 0.914 0.924239.5 240.9 C: 0.932

1 Actual dose = Nominal dose + transit dose

Graphical analysis:Plot 'actual dose' on the x-axis and 'R(mean)' on y-axis

Regression Analysis:X-variable = Actual doseY-variable = Response, thus there are 3 y-values for each x-valueFit the data to linear as well as quadratic relationship

Attach all the graphs to this form



y= a + bx a= 0.006297 b= 0.00380

Linear Dose x Response

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0 50 100 150 200 250 300Dose / Gy

Resp

onse

(OD)

Linear fit Residuals

-2.00

-1.50

-1.00

-0.50

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0 50 100 150 200 250 300

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Resid

ual %



y = a + bx + cx2 a= 0.002582 b= 0.003864c= -0.000000240

Quadratic Dose x Response

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Quadratic fit Residuals

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)



ln(y) = a + b*ln(x) a= -5.49372 b= 0.98652

Power Series fit, Dose X Response

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Power Series fit Residual(%)

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Gafchromic Dosimetry System for SIT Reporting FormForm-SIT-4E

Gafchromic Dosimetry System Calibration: Residual behaviourFor regression analysis

Select FitDate: 2003-10-09Operator: Ouatara

Actual Linear Rel. Quadratic Rel. Power Series Rel.dose1 (Gy) Dcalc

2 Resid.(%)5 Dcalc3 Resid.(%)5 Dcalc

4 Resid.(%)5A: 41.21 A: -1.65 A: 41.56 A: -0.83 A: 41.61 A: -0.70

41.9 B: 41.65 B: -0.60 B: 41.99 B: 0.20 B: 42.04 B: 0.33C: 41.39 C: -1.23 C: 41.73 C: -0.42 C: 41.78 C: -0.29A: 83.92 A: 1.90 A: 83.84 A: 1.81 A: 83.85 A: 1.81

82.4 B: 82.53 B: 0.21 B: 82.46 B: 0.13 B: 82.47 B: 0.13C: 82.27 C: -0.11 C: 82.20 C: -0.19 C: 82.21 C: -0.18A: 121.82 A: 0.52 A: 121.55 A: 0.30 A: 121.58 A: 0.33

121.2 B: 119.54 B: -1.36 B: 119.28 B: -1.58 B: 119.31 B: -1.55C: 121.03 C: -0.13 C: 120.76 C: -0.35 C: 120.80 C: -0.32A: 161.81 A: 1.12 A: 161.54 A: 0.95 A: 161.58 A: 0.98

160.0 B: 160.67 B: 0.40 B: 160.40 B: 0.24 B: 160.44 B: 0.26C: 160.14 C: 0.07 C: 159.87 C: -0.09 C: 159.91 C: -0.07A: 200.86 A: -0.61 A: 200.79 A: -0.64 A: 200.77 A: -0.65

202.1 B: 200.68 B: -0.70 B: 200.61 B: -0.73 B: 200.59 B: -0.74C: 203.77 C: 0.83 C: 203.72 C: 0.81 C: 203.69 C: 0.79A: 239.26 A: -0.69 A: 239.57 A: -0.56 A: 239.40 A: -0.63

240.9 B: 239.08 B: -0.76 B: 239.39 B: -0.64 B: 239.22 B: -0.71C: 243.82 C: 1.20 C: 244.19 C: 1.36 C: 244.00 C: 1.28

Ufit 0.940 0.818 0.810

1 Values from column 2, Form-SIT4D2 Dcalc = Calculated dose for the corresponding value of 'Response'from Form-SIT-4D, and using the linear calibration relationship

3 Dcalc = Calculated dose for the corresponding value of 'Response'from Form-SIT-4D, and using the quadratic calibration relationship

4 Dcalc = Calculated dose for the corresponding value of 'Response'from Form-SIT-4D, and using the power series calibration relationship

5 Residual(%) = 100 x (Dcalc - Dactual)/Dactual

Note: Residual(%) value may be positive or negative.Plot 'Residual(%)' as y-parameter and 'Actual dose' as x-parameter for both the fits.Select the relationship that yields random distribution of the residual values as afunction of dose. If they show similar random distribution, select the linear functionas the calibration relationship.Attach all the graphs to this Form.

LinearQuadraticPower Series


Gafchromic Dosimetry System for SIT Reporting Form Form-SIT-5Dose Determination

Date: 2006-05-14 Dose rate (Gy/sec): 0.230OD(bkgd) Calibration out of dateDosimetry system Calibration out of date

Lot ID: 7026-09 Transit time/sec: 4.5Calibration relationship: Linear Target dose/Gy: 100

From Form-SIT-4CIrradiation time/sec: 430

Operator: AGPOD of the three ND filters

Before the measurements: 0.297 0.598 1.103After the measurements: 0.297 0.597 1.104

Dosimeter1 Temp(oC)2 OD3 Respo.4 Corr Res5 Dose(Gy)6 Remarks71 22.5 0.465 0.379 0.379 982 22.0 0.458 0.372 0.374 973 21.5 0.462 0.376 0.379 98

1 Identification of the dosimeter. This information should appear on the small envelope in which the dosimeter was irradiated and where it is stored.

2 Estimated temperature of the dosimeter during irradiation.3 Measured OD of the dosimeter4 Response = measured OD - OD(bkgd)5 Corrected Response (for temperature) = Response (column 4) x [1.0 - 0.0073 x dT]where dT = Temperature (column 2) - calibration temp (See Section 3.6)

6 Dose calculated using the Corrected Response (column 5) and the calibration relationship(Form-SIT-4C)

7 Enter information re: product run, product batch, location of dosimeter, etc.



Form-SIT-6Homogeneity for the Batch of DosimetersNote: Check and adjust the absorption scale before these measurements.

Lot ID: 7026-09 Dose Rate: 0.320 Gy/sec

Date: 2003-11-05 Transit time: 4.5

Dose/Gy: 100

Time/sec: 308

Operator: AGP

Dosimeter Response(600nm)

1 0.4552 0.4553 0.4524 0.4565 0.4566 0.4597 0.4608 0.4619 0.463

Mean Response 0.457Standard Deviation 0.0035Coefficient of Variation (%)1 0.77

1 CV(%) = {standard deviation/mean value} x 100



Form-SIT-7Dose Mapping

Date: 2004-02-02

Product: G. pallidipes

Container: 1.1

Operator: AGP

OD of the three ND filters Before the measurements: 0.297 0.597 1.102After the measurements: 0.297 0.599 1.105

Dosimeter1 Temp(°C)2 OD3 Respo.4 Corr Res5 Dose(Gy)6 Remarks7

Reference 24.0 0.372 0.286 0.283 73 For routine monitoringTop 1 24.0 0.394 0.308 0.305 79

2 24.0 0.397 0.311 0.308 793 24.0 0.384 0.298 0.295 764 24.0 0.380 0.294 0.291 755 24.0 0.420 0.334 0.331 856 24.0 0.412 0.326 0.323 837 24.0 0.452 0.366 0.362 948 24.0 0.437 0.351 0.347 909 24.0 0.428 0.342 0.339 8810 24.0 0.428 0.342 0.339 8811 24.0 0.426 0.340 0.337 87

Middle 1 24.0 0.421 0.335 0.332 862 24.0 0.431 0.345 0.342 883 24.0 0.448 0.362 0.358 934 24.0 0.456 0.370 0.366 955 24.0 0.454 0.368 0.364 946 24.0 0.460 0.374 0.370 967 24.0 0.569 0.483 0.478 1248 24.0 0.540 0.454 0.449 1179 24.0 0.589 0.503 0.498 13010 24.0 0.573 0.487 0.482 12511 24.0 0.568 0.482 0.477 12412 24.0 0.536 0.450 0.445 116

NOTE: This is the same form as Form-SIT-5, except that there should be a dosimeter "reference" locationwhich will be used later for routine monitoring (see Section 4.4).

1. Identification of thedosimeter. This information should also appear on the small envelope in which the dosimeter was irradiated and where it is stored.2. Estimated temperature of the dosimeter during irradiation.3. Measured OD of the dosimeter4. Response=Measured OD - OD(bkgd)5. Corrected Response (for temperature) = Response (column 4) [1.0-0.0073 x ∆T] Where ∆T = Temperature (column 2) - calibration temp (See Section 3.6)6. Dose calculated using the corrected Response (column 5) and the calibration relationship (Form-SIT-4C)7. Enter information re: product run, product batch, location of dosimeter, etc.


Gafchromic Dosimetry System for SIT Reporting Form Form-SIT-8AProcess Control: Routine Dosimetry

Date: 2004-05-14

Irradiation batch/run ID: G. pallidipes 100Gy

Analysed by: AGP

OD of the three ND filters Before the measurements: 0.297 0.598 1.103After the measurements: 0.297 0.597 1.104

Dosimeter1 Temp(°C)2 OD3 Dose(Gy)6 95% CI7 Mean 95% CI Remarks8

1a Ref 24 0.458 95.4 ± 4.6 Reference location1b 24 0.469 98.2 ± 4.7 96.8 ± 4.51c 24 0.463 96.7 ± 4.62a ± Minimum dose2b ± ±2c ±3a Centre 22.5 0.496 106.5 ± 5.13b 22.5 0.499 107.2 ± 5.1 106.2 ± 4.93c 22.5 0.490 104.9 ± 5.04a ±4b ± ±4c ±

NOTE: This is the same form as Form-SIT-5 and -7. However the dosimeters are placed either at thelocation of minimum dose or at the reference location identified during dose mapping (see Section 4.4 andForm-SIT-7)Up to four sets of 1, 2 or 3 dosimeters placed at a single location can be recorded.The results for each dosimeter are shown together with the average of the three with confidence interval.

1. Identification of the dosimeter. This information should also appear on the small envelope in which the dosimeter was irradiated and where it is stored.2. Estimated temperature of the dosimeter during irradiation.3. Measured OD of the dosimeter4. Response=Measured OD - OD(bkgd)5. Corrected Response (for temperature) = Response (column 4) [1.0-0.0073 x ∆T] Where ∆T = Temperature (column 2) - calibration temp (See Section 3.6)6. Dose calculated using the corrected Response (column 5) and the calibration relationship (Form-SIT-4C)7. 95% confidence interval (= 2 * UTotal)8. Enter information re: product run, product batch, location of dosimeter, etc.



Form-SIT-8BProcess Control: Process Parameter Monitoring

Date: 2005-05-14

Irradiation batch/run ID: Gp100Gy050514

Analysed by: AGP

Please add any other parameters that are relevant to your processParameter Description / ValueSpecies G. pallidipesInsect density (g/cc) 0.48Source (location, activity) (if different than normal) GC220Canister ID 1.1Canister rotated? Speed= RPMCanister location CentreIrradiation duration / Conveyor speed 377

No Yes



Form-SIT-9Characteristics of the Current Lot of Dosimeters

Gafchromic dosimeter Lot ID 7026-09Gafchromic dosimeter sheets received on: 2000-04-01

Calibration of Gafchromic dosimetry systemDate of calibration (valid for only one year) 2003-10-09Irradiation temperature T(cal) 22.6Relationship Linear, O.D. = 0.0063 + 0.0038 * dose

Background responseDate of measurement (valid for 6 months) 2005-04-12OD(bkgd) 0.086

Uncertainty ValuesArising from dose rate udr(%)= 1.7 date= 2000-04-05Arising from calibration ufit(%)= 0.94 date= 2003-10-09Arising from lot non-homogeneity (n = 1) ulot(%)= 0.77 date= 2003-11-05Arising from uncertainty in read-out temperature utemp-r (%)= 1.00Arising from uncertainty in the temperature Tmax(est) 24 Tmin(est) 21of the dosimeter during irradiation utemp-i(%)= 0.63

utotal(%)= 2.40


dosimetry system for sit...2 dosimetry system for sit: manual for gafchromic® film 2.2....

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