manual

PYLON MODEL

600P

PASSIVE LUCAS TYPE CELL DETECTOR MANUAL

MANUAL NUMBER: 7940003

Revision 1 Draft 9

Copyright 2011 Pylon Electronics Inc. (ALL RIGHTS RESERVED)

Registered Trademark Canada and U.S.A.

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Document No.: 7940003 Rev 1 Draft 9

CAUTION 1) DO NOT attempt to thread the Model 600P Lucas type cell onto older Pylon products such

as the AB-5, AB-5R, and AB-4. The threads are incompatible. Forcing the 600P Lucas type cell onto any of these older products will damage the threads on the cell and as well as on the PMT assembly on those products.

2) Do not force the Model 600P Lucas type cell onto the AB6A PMT assembly since this may

damage the cell and / or AB6A PMT assembly threads. A small amount of lubricating grease may be applied to the threads to assist with installation. This may be renewed when necessary.

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IMPORTANT 1) The 600P detectors are designed for use with a number of other devices. Consult the

instruction manuals which accompanied the devices for important operational and safety instructions.

2) If maximum measurement accuracy is required, it is recommended that the 600P detectors be

calibrated with the monitor that it will be used. 3) Many of the terms and abbreviations used in this manual are described in Pylon manual

number 7940018 - Glossary of Selected Pylon Terms. 4) The following symbols may be used throughout this manual:

WARNING The Warning symbol is use to identify notes that are used to warn of potential hazards that could cause injury or death to personnel as well as damage to the equipment.

CAUTION The Caution symbol is use to identify notes that are used to warn of potential hazards that could damage the equipment.

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WARRANTY PYLON ELECTRONICS INC. products are warranted against defects in material and workmanship for a period of one year from the date of shipment. Our warranty obligation is limited to the repair of products or parts thereof which, on our examination, prove to be defective during the warranty period. The warranty shall not apply to any equipment which has been subject to accident, incorrect wiring not of our own or operation not in accordance with manufacturer's written instructions. PYLON ELECTRONICS INC. repairs are warranted against defects in material and workmanship for a period of 90 days from the date of shipment. Our warranty obligation is limited to the repair of the unit returned prepaid, to our factory and which, on our examination, prove to be defective during the warranty period. Equipment which has work performed under Warranty will be returned to the Distributor freight prepaid. The warranty shall not apply to any equipment which has been subject to accident, incorrect wiring not of our own, or operation not in accordance with manufacturer's written instructions. This warranty is given by PYLON in lieu of all other warranties arising in law or otherwise in respect of the goods, and this Company shall not be liable under any circumstances for consequential damage. Note: All product(s) must be returned prepaid, to our factory. All warranty claims shall be addressed to: Pylon Electronics Inc. 147 Colonnade Road, Ottawa, ON K2E 7L9 CANADA Phone: 613-226-7920 Fax: 613-226-8195 Email: [email protected]

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DISCLAIMER Pylon Electronics Inc. has attempted to ensure that this manual is complete and accurate. However, Pylon will not be held responsible for any errors and omissions in this manual including consequential damage due to the information contained herein. Please forward all comments and suggestions for improvements on the product or this manual to: Pylon Electronics Inc. 147 Colonnade Road, Ottawa, ON K2E 7L9 CANADA Phone: (613) 226-7920 Fax: (613) 226-8195 Email: [email protected] For technical support, please contact us at the above address. Please visit us on our website at www.pylonelectronics.com. Click on the Products icon.

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TABLE OF CONTENTS CAUTION .................................................................................................................................................................... 2IMPORTANT .............................................................................................................................................................. 3WARRANTY ................................................................................................................................................................ 4DISCLAIMER .............................................................................................................................................................. 51.0 INTRODUCTION............................................................................................................................................... 8

1.1 PURPOSE ............................................................................................................................................................ 81.2 SCOPE ................................................................................................................................................................ 81.3 GENERAL DESCRIPTION ...................................................................................................................................... 81.4 THEORY OF OPERATION ...................................................................................................................................... 91.5 SPECIFICATIONS ............................................................................................................................................... 111.6 RADON GAS DESCRIPTION ................................................................................................................................ 121.7 THORON GAS DESCRIPTION .............................................................................................................................. 12

2.0 OPERATING PROCEDURES ........................................................................................................................ 132.1 EQUIPMENT REQUIREMENTS ............................................................................................................................. 132.2 CONSTRAINTS .................................................................................................................................................. 142.3 MEASUREMENTS .............................................................................................................................................. 16

2.3.1 Overview ................................................................................................................................................ 162.3.2 Preparation ............................................................................................................................................ 162.3.3 Continuous Sample Measurements .......................................................................................................... 17

2.3.3.1 Initial AB6A Setup ............................................................................................................................................ 172.3.3.2 System Background Determination .................................................................................................................... 182.3.3.3 Continuous Sample Measurements .................................................................................................................... 20

2.3.4 Cell Flushing .......................................................................................................................................... 212.3.4.1 Overview .......................................................................................................................................................... 212.3.4.2 Flushing Procedure ............................................................................................................................................ 21

2.4 CALCULATION AND DATA ANALYSIS ................................................................................................................ 222.4.1 Calculations ............................................................................................................................................ 222.4.2 Data Analysis .......................................................................................................................................... 24

2.5 OTHER MEASUREMENT TECHNIQUES ................................................................................................................ 262.5.1 Overview ................................................................................................................................................ 262.5.2 Multiple Approximate Readings .............................................................................................................. 26

2.6 RADON MEASUREMENTS IN BUILDINGS GUIDELINES ......................................................................................... 282.6.1 Quality Assurance Program Guidelines ................................................................................................... 282.6.2 Building Measurement Guidelines ........................................................................................................... 292.6.3 Information To Be Recorded ................................................................................................................... 292.6.4 Data Analysis .......................................................................................................................................... 30

2.7 THORON GAS MEASUREMENTS ......................................................................................................................... 303.0 CALIBRATION ................................................................................................................................................ 30

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4.0 CELL MAINTENANCE AND REPAIR ......................................................................................................... 305.0 FURTHER INFORMATION ........................................................................................................................... 32

5.1 SUGGESTED READINGS ..................................................................................................................................... 32

LIST OF FIGURES FIGURE 1 - 600P LUCAS TYPE CELL ............................................................................................................................ 8FIGURE 2 - 600P / AB6A INTERNAL PMT CONNECTION .......................................................................................... 18

LIST OF TABLES TABLE 1 - RADIUM DECAY CHAIN ............................................................................................................................. 10TABLE 2 - 600P SPECIFICATIONS ............................................................................................................................... 11TABLE 3 - RADIOTHORIUM DECAY CHAIN ................................................................................................................ 13

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1.0 INTRODUCTION 1.1 Purpose The purpose of this manual is to describe the Pylon Model 600P passive Lucas type cells

and their use. 1.2 Scope This manual covers the description, use, and calibration of the Pylon Model 600P passive

Lucas type cells (hereinafter referred to as the 600P). Although the cells may be used with a variety of radon monitors provided that the

appropriate light-tight connections can be made, this manual concentrates on the use of the cells with the Pylon Model AB6A monitor (hereinafter referred to as the AB6A). A detailed description of the AB6A and its operation is beyond the scope of this manual. Please refer to Pylon manual number 7940010 for more information on the AB6A.

1.3 General Description The 600P are passive scintillation cells detectors which are used to measure radon gas.

Please refer to Figure 1 - 600P Lucas Type Cell. It is considered to be passive because the gas sample passively diffuses into the cell. The open end is threaded to screw directly onto the AB6A PMT mount.

Figure 1 - 600P Lucas Type Cell

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Lucas type Scintillation cells are sensitive to three radioactive isotopes. These are radon

gas (Rn-222), thoron gas (Rn-220), and actinon gas (Rn-219). These gases are the decay products (progeny) of the Uranium 238, Thorium 232, and Uranium 235 series respectively.

This manual primarily considers radon as it is the most commonly encountered of the

three gases. Radon gas is described in more detail in the following paragraphs. Thoron gas is less prevalent than radon gas and, because it has a short half-life, its presence tends to be more unpredictable than radon. Thoron gas is also described in more detail in the following paragraphs. Actinon, because it has a very short half-life (3 to 9 seconds) and an uncommon parent material, is rarely encountered. Therefore, Actinon is not covered in this manual.

Pylon manufactures the 600P through a special process which gives them very high

efficiencies. 1.4 Theory of Operation Pylon passive scintillation cells, such as the 600P, are open, light tight metal cylinders

which allow a gas sample to passively diffuse through a light-proof polyurethane foam barrier into the cell. The foam barrier also prevents airborne alpha particles and radon progeny from entering the 600P. It takes approximately one half-hour for the 600P to achieve the same radon gas level as is present in the surrounding environment. Once inside the cell, radon gas decays into its daughter products (progeny) as shown in Table 1 - Radium Decay Chain. Some of these daughters are alpha particle emitters. Radon gas, RaA, and RaC' emit alpha particles during normal measurement period lengths.

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Isotope Half Life (T1/2) Decay Constant () * Alpha Energy Ra-226 (Radium) 1622 years 0.000427 year-1 4.77 MeV

Rn-222 (Radon Gas) 3.825 days 0.0001258 minute-1 5.48 MeV

Po-218 (RaA) 3.05 minute 0.227 minute-1 6.00 MeV

Pb-214 (RaB) 26.8 minute 0.0259 minute-1 -

Bi-214 (RaC) 19.7 minute 0.0352 minute-1 -

Po-214 (RaC') 1.6 x 10-4 second 4332 second-1 7.69 MeV

Pb-210 (RaD) 22.3 year 0.031 year-1 -

Bi-210 (RaE) 5.0 days 0.139 day-1 -

Po-210 (RaF) 138.4 days 0.005 day-1 5.31 MeV

* 2/12/1

69315.02lnTT

Table 1 - Radium Decay Chain Like all scintillation cells, the 600P has an alpha sensitive scintillator lining the interior

of the cell. This scintillator, which is silver activated zinc sulphide, produces light pulses when it is struck by alpha particles of the appropriate energy levels. When an alpha particle strikes the activated sulphide, the alpha particle becomes a helium atom and the sulphide de-excites by emitting photons (i.e., light pulses).

The 600P is not a stand-alone product. It only produces light pulses in the presence of

alpha particles that are within the appropriate energy level range. It must be used with a monitor that converts and counts the light pulses.

The 600P is designed to screw directly onto the AB6A PMT mount in such a manner that

the open end of the 600P is mounted against the end of the photomultiplier tube (PMT) of the AB6A. The PMT detects the light pulses, converts them to electrical pulses, and amplifies the electrical pulses. The AB6A electronics further amplify the electrical pulses, discriminates noise pulses out, and counts the remaining pulses. The AB6A displays the counts on a touchscreen LCD. The AB6A also stores the data in files which can be accessed on the monitor itself or transferred to a PC for further analysis. In

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addition, the AB6A can perform some automated calculations if the appropriate information is entered into the memory.

Not all the alpha particles result in light pulses nor do all of the light pulses that are

generated reach the PMT. In order to measure radon gas, the measuring system's response to radon gas must be known. There is a direct relationship between the number of light pulses counted by the AB6A and the concentration (or activity) of the radon gas in the cell. The relationship between the counts recorded and the activity of the sample is referred to as sensitivity (S) for continuous sampling. Counting sensitivity must be known before measurements can be made. Please refer to Paragraph 3.0 for information on how to determine these parameters.

1.5 Specifications Table 2 - 600P Specifications below provides the specifications for the 600P. Radiation Detected: Alpha Scintillator: ZnS(Ag) Alpha Energy Ranges: 4.5 to 9 MeV LAD 1 : 48.1 (1.30) Bq/m3 (pCi/l) Sensitivity (S): 0.021 (0.76) cpm/Bq/m3 (cpm/pCi/l) Accuracy 2 : 4 % Active Volume: 272 (5.2) ml (oz (US Liq)) Detector Background: < 1.0 cpm Calibration 3 : Single Point Primary Construction Material: Aluminum Operating Temperature Range: 0 to +50 (+32 to +122) C (F) Storage Temperature Range: -20 to +75 (-4 to +167) C (F) Relative Humidity Range 4 : 0 to 90 % Diameter: 6 (2.38) cm (in) Height: 15.6 (6.13) cm (in) Weight: 167 (0.4) g (lb) 1 Lowest Activity Detectable. 2 At a 1 Confidence Level. 3 Passive cells are provided with a single point calibrations. Custom calibrations are available. Custom

calibrations include multi-point calibrations and calibrations at non standard activity levels. 4 Non-Condensing. 5 All values are nominal. 6 Specifications are based on new units which have been appropriately calibrated.

Table 2 - 600P Specifications

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1.6 Radon Gas Description Radon gas is a colourless, odourless, and chemically inert radioactive gas which occurs at

various concentrations almost everywhere. Like all radioactive substances, radon gas decays into other elements. In the decay process radon gas emits radiation, primarily in the form of alpha particles. The alpha-emitting radon daughter products produced through the decay process can adhere to surfaces, including airborne dust and smoke.

It is now widely believed that radon gas, because of its daughter products, is responsible

for much of the lung cancer risk to the nonsmoking segment of the general public. Radon daughter products breathed into the lungs can result in considerable damage to respiratory cells. When dissolved in water and ingested, radon can affect cells in the stomach wall and may cause further problems. In buildings, radon gas and its progeny can reach concentrations high enough to be a serious health risk. Radon gas can enter buildings as part of the construction materials or through seepage from the surrounding soil or ground water. Researchers have found houses which have radon gas levels greatly exceeding the occupational safety standards for uranium mines.

1.7 Thoron Gas Description Thoron gas (Rn-220) is a short lived isotope of radon. It is part of the thorium (Th-232)

decay series having a half life of 54.5 seconds as shown in Table 3 - Radiothorium Decay Chain. The general information provided in the previous paragraph is also applicable to Thoron gas.

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Isotope Half Life (T1/2) Decay Constant () * Alpha Energy Th-228 (Radiothorium) 698 days 0.000993 day-1 5.41 MeV

Ra-224 (Thorium-X) 3.64 days 0.190 day -1 5.68 MeV

Rn-220 (Thoron gas) 54.5 second 0.763 minute-1 6.28 MeV

Po-216 (ThA) 0.158 second 4.387 second-1 6.775 MeV

Pb-212 (ThB) 638.4 minute 0.001086 minute-1 -

Bi-212 (ThC) 60.5 minute 0.011457 second-1 6.04, 6.08 MeV

Po-212 (ThC') 3 x 10-7 seconds 2.31 x 106 second-1 8.78 MeV

Tl-208 (ThC'') 3.1 minute 0.224 minute-1 -

* 2/12/1

69315.02lnTT

Table 3 - Radiothorium Decay Chain 2.0 OPERATING PROCEDURES 2.1 Equipment Requirements The following lists the necessary equipment 1 required to use the 600P: Item Mfr Model Description Qty 1 Pylon AB6A Radiation Monitor 1 2 - - Compressed Nitrogen Gas, Aged Air, or Filtered

Air 2 A/R

1 Equivalent equipment is permitted. 2 For flushing the cells.

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The following lists the optional equipment 1 that would assist in the use of the 600P: Item Mfr Model Description Qty 1 - - Personal Computer (PC) c/w a Spreadsheet

Program 1

1 Equivalent equipment is permitted.

NOTE The User must be familiar with the operation of the monitor

before the cells can be used. If using an AB6A, please refer to the AB6A Instruction Manual (Manual Number 7940010) for information on the use and operation of the AB6A.

2.2 Constraints A number of factors can affect performance and accuracy when using the 600P. Some of

these factors are described below. Observance of the instructions and recommendations presented in this manual will help the User achieve maximum performance and accuracy.

Monitor Setup: Monitors must be set up in accordance with the manufacturer's instructions to optimize

measurement efficiencies and sensitivities. For the AB6A, this involves setting up the High Voltage (HV) and Discriminator (DISC)

parameters. These settings, which are programmed into the AB6A, determine how the cell's light pulses which are detected by the AB6A will be counted. If the HV is set too high or the DISC is set too low, the AB6A will be overly responsive to low level electrical noise, resulting in counts that contain too much background. If the HV is set too low or the DISC is set too high, the AB6A will not be responsive enough to the alpha decay pulses. The optimal combination of HV and DISC settings is known as the AB6A Operating Point. The operating point will depend on the accessory being used with the AB6A. The method to set the AB6A Operating Point for the 600P is provided in Section 3.0 of this manual.

Humidity: If water condensation forms in the cell, accuracy may be affected. Water condensation

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can also damage the cell. When using a 600P where the relative humidity is condensing, a chamber should be used

for the measurements and a drying column should be used to dry the gas sample before it is drawn into the chamber.

Short-Lived Radon Daughters: RaA, RaB, and RaC remain within the cell even after flushing. The cell must be left for

several hours (preferably overnight) so that most of these short-lived radon daughters will decay away.

Thoron Daughters: If thoron gas was present in the sample, ThB and ThC will plate out on the cell wall.

Thoron daughter activity is regulated by a half-life of 10.6 hours and will remain attached to the cell wall despite being flushed. It may take more than 24 hours for the background count rate to decay to an acceptable level.

Long-Lived Radon Daughters: As shown in Table 1 - Radium Decay Chain, radon gas eventually decays into Pb-210

and Po-210. Very small amounts of these long-lived isotopes accumulate on the inside walls of the cell from each measurement. This results in an unavoidable and gradual buildup in the background count rate, usually over several years. The amount of buildup is proportional to the number of measurements, the length of time that samples are in the cell, and the activity of the samples.

It is possible to minimize the effects of Pb-210 buildup by flushing the cells with

nitrogen, aged air, or filtered air after counting, especially if the sample has a high radon content. (See Section 2.3.4.)

Cells to be used for high and low radon levels can be segregated so that cells which have

developed a high background level can be reserved for samples where high radon levels may be expected to occur (such as for studies of buildings with known high radon levels).

If and when the background level gets too high to take meaningful measurements, the cell

should be replaced or refurbished.

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Radon Gas Absorption: Small traces of radon gas can be absorbed by the scintillator binding material. This is

usually only noticeable when low level measurements follow very high measurements. The radon gas can be removed by flushing the cell. (See Section 2.3.4.)

Other Long-Lived Radioisotopes: Contamination from materials such as Ra-226, Am-241, and Th-230 can occur. This is

more likely to happen with measurements in industrial locations than in residential measurements. This type of contamination is usually associated with visible dirt or dust inside the cell. Such contamination can sometimes be removed by flushing the cell with nitrogen, aged air, or filtered air. (See Section 2.3.4.)

Insufficient Allowance For Ingrowth: When radon gas is removed from a stable environment, it takes 3.5 hours for it to decay

into its daughter products and for the daughter products to ingrow to the level determined by the radioactive process. This decay and ingrowth process is known as reaching equilibrium. For precise measurements, it is advisable to wait until equilibrium is reached before conducting radon measurements.

For continuous monitoring of surrounding air, measurements should begin 3.5 hours after

placing the monitor and 600P in the measurement location. Correction factors are not needed because the diffusion into the cell will keep the concentration constant. Where radon gas levels are constantly changing, a lag will be introduced in the short term response. The average radon level count will only be marginally affected by this lag.

2.3 Measurements 2.3.1 Overview The 600P is designed to primarily perform continuous sample measurements. This

manual describes the most common continuous sample measurement method using the AB6A. Other methods are beyond the scope of this manual.

2.3.2 Preparation The User should be familiar with the operation and use of the AB6A before setting up or

using the equipment.

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Before conducting any type of measurements: Ensure that the cell has been flushed in accordance with Section 2.3.4 after the

last measurement. Ensure that the cell's sensitivity is known. 2.3.3 Continuous Sample Measurements 2.3.3.1 Initial AB6A Setup The following steps should be performed to setup the measurement system (AB6A

monitor and cell): 1) Attach the 600P to the AB6A by removing the protective caps from both the

AB6A PMT mount and the cell and threading the cell onto the AB6A PMT mount.

CAUTION DO NOT FORCE THE CELLS ONTO THE PMT ASSEMBLY

SINCE THIS MAY DAMAGE THE CELL AND / OR PMT ASSEMBLY THREADS. A SMALL AMOUNT OF LUBRICATING GREASE MAY BE APPLIED TO THE THREADS TO ASSIST WITH INSTALLATION. THIS MAY BE RENEWED WHEN NECESSARY.

NOTE

The top cover of the AB6A may be removed to assist with the

handling of the monitor and reduce the footprint of the monitor while in operation.

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Figure 2 - 600P / AB6A Internal PMT Connection

2) Turn on the AB6A.

NOTE If the AB6A will be left on for longer than 4 hours, it is highly

recommended that the AB6A AC battery charger be used to provide the necessary power for the AB6A.

3) Verify that the appropriate and desired cell parameters (Model, serial number,

current sensitivity, etc.) have been entered into the AB6A. Update, as appropriate. 4) Perform a system background determination in accordance with Section 2.3.3.2. 2.3.3.2 System Background Determination NOTE If the System Background (SBg) is not determined and saved

prior to the measurement, the AB6A program will use the SBg value that is stored in memory from the last time that the System Background method was run and the results saved.

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The following steps should be performed to determine the current system background: 1) Program the System Background method in the AB6A for the desired parameters.

The recommended parameter settings are: Interval Length: 2 minutes # of Intervals: 5 # Intervals to Discard: 0



2) Place the measurement system (600P and AB6A) in an environment with low

levels of radon (e.g., Filtered outside air, nitrogen, or aged air.) 3) Allow the measurement system to remain in the low level radon environment for

a minimum of 30 minutes.

NOTE It takes approximately 30 minutes for the interior of the cell to

achieve the same low radon environment as the exterior of the cell.

4) Run the System Background method on the AB6A. Save the results.

NOTE The AB6A can be programmed with a delayed start or to start

at a specific time. If this is set up appropriately, the system can be placed in the low radon environment and the measurement will automatically start at the appropriate time.

NOTE

If manual calculations will be performed, record this value as

SBg.

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CAUTION THE HV IS ONLY APPLIED TO THE AB6A PMT WHEN A

METHOD IS BEING RUN. IT IS IMPERATIVE THAT NO METHOD BE STARTED OR RUN UNLESS THE AB6A PMT IS COVERED WITH THE PROTECTIVE CAP, A DETECTOR, OR A CHECK SOURCE. OTHERWISE AN ACTIVE PMT WILL BE EXPOSED TO LIGHT WHICH CAN CAUSE IRREPARABLE DAMAGE TO THE PMT.

5) Proceed to Section 2.3.3.3. 2.3.3.3 Continuous Sample Measurements The following steps should be performed to perform the continuous sample

measurements: 1) Program the Continuous method in the AB6A for the desired parameters. Typical

parameter settings are: Interval Length: 1 hour # of Intervals: # Intervals to Discard: 0 1 This setting means that the AB6A will count until it is stopped by the User. 2 Of course, the # of intervals can be set to a specific value such as 24 or 72. The run will

automatically stop at the end of the specified interval. 2) Place the measurement system (AB6A monitor and cell) in the location where the

measurements are to be made.



3) Start the method and allow it to run for the desired number of intervals.

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4) Stop the method. 5) Transfer the file from the AB6A to the PC and analyze the data in accordance

with Section 2.4. 6) Remove the cell from the AB6A and flush it in accordance with Section 2.3.4. 2.3.4 Cell Flushing 2.3.4.1 Overview Flushing is the process by which traces of the gas samples obtained during measurement are

removed from the cell after the measurement has been completed. If trace gas samples containing radon and thoron remain inside the cell, the background levels in the cell will increase.

Cells should be flushed after each measurement in order to keep background levels low. Flushing is especially important when higher levels of radon are measured. 2.3.4.2 Flushing Procedure The simplest method of flushing the cell is to: 1) Remove the protective cap from the cell. 2) Place the uncovered cell in a dark environment. 3) Expose the cell to filtered outside air that contains normally low radon levels for a

minimum of 24 hours.

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The preferred method of flushing the cell is to perform the above steps except that the exposure shall be in an aged air or nitrogen environment.

2.4 Calculation and Data Analysis The file produced by the measurement run can be printed on the PC printer or it can be

imported into a spreadsheet program for further data manipulation and analysis. The following points should be noted: 1) If the appropriate cell parameters have been entered and the cell selected for the

measurement run, the radon concentration will be automatically calculated and provided in the file as long as the run is set up to automatically stop. If the run is manually stopped, calculations will not be performed.

2) The radon concentration is calculated by the AB6A as indicated in Section 2.4.1. The

User may manually calculate the radon concentration using the same formulae or set up a spreadsheet to perform the same calculations.

NOTE If the System Background (SBg) was not determined and saved

prior to the measurement, the AB6A program will use the SBg value that is stored in memory from the last time that the System Background method was run and the results saved.

3) It is recommended that the counts and results in the intervals covered by the first 3.5

hours of measurement be ignored to ensure that the gas sample in the cell has reached equilibrium.

NOTE If the radon concentration is changing over the course of the

measurement period, there will be a lag between the actual radon concentration and the measurement results due to the slow diffusion of the gas sample into the cell.

2.4.1 Calculations The following steps provide general instructions for performing the radon concentration

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calculations. Most of the calculations may be performed automatically by the AB6A if the appropriate cell parameters have been entered into the AB6A, the cell has been selected, and the run has been set up to automatically stop.

NOTE The User may automate the calculations by setting up a

spreadsheet with cells to enter the raw data and the formulae. 1) Calculate and record the Total Counts Per Minute for each interval as follows:

TCPM = IntLenTCX

Where: TCPM = Total Counts Per Minute. TCX = Total Counts counted by the monitor for the interval. IntLen = Interval Length converted to minutes. NOTE The counts in the intervals that cover the first 3.5 hours of

measurement should be ignored for these calculations. 2) Calculate and record the Net Counts Per Minute for each interval as follows: NCPM = SBgTCPM Where: NCPM = Net Counts Per Minute TCPM = Total Counts Per Minute calculated in step 1. SBg = System Background determined in Section 2.3.3.2 in

counts per minute. 3) Determine the radon concentration for each interval as follows:

Conc = S

NCPM

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Where: Conc = Radon concentration in Bq/m3 or pCi/l depending on

the Sensitivity Unit of Measure. NCPM = Net Counts Per Minute calculated in step 2. S = Sensitivity of the cell in cpm/Bq/m3 or cpm/pCi/l

depending on the desired Unit of Measure that was determined during calibration.

NOTE The following provides an example of the calculations: Interval Length = 30 minutes SBg = 0.6 cpm Interval Count = 528 Sensitivity = 1.50 cpm/Bq/m3 TCPM = 528 / 30 = 17.6 cpm NCPM = 17.6 - 0.6 = 17 cpm Concentration = 17 / 1.50 = 11.3 Bq/m3 9) If desired, the average radon concentration for a selected period can be calculated as

follows:

ConcAvg = nConcConcConc n ,..., 21

10) Record the value and all calculations. 2.4.2 Data Analysis The data analysis should be performed to determine if the results indicate that there is cause

for concern. The data analysis needs to be tailored to the reason that the measurements were performed.

For example, the radon concentrations for each interval can be plotted on a graph to show

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variations and peaks over the course of time. The average radon concentration over a period of time (See step 9 of Section 2.4.1 above) can be used to provide a single result.

It should be noted that other factors may be required and included in the data analysis.

For example, for very precise work it may be advantageous to take the effect of air pressure on the sample into account due to the attenuation of the alpha energy as it passes through the air in the cell. This is particularly important if samples are taken at different altitudes. The necessary calculations are beyond the scope of this manual.

In general, the higher the concentration of radon gas, the higher the risk to health. For

example, in home measurements, the U.S. Environmental Protection Agency (EPA) provides guidelines for radon gas risk levels and corresponding mitigation action. The following is adapted from "Radon Reduction Techniques for Detached Homes" (EPA document EPA/625/5-87/019 Page 9):

Concentration below 4 pCi/l (148 Bq/m3): At or below EPA guidelines. Reduction efforts discretional. 4 to 20 pCi/l (148 Bq/m3 to 740 Bq/m3): EPA recommends action to reduce level to 4 pCi/l within a few years. Sooner for

levels at the upper end of range. 20 to 200 pCi/l (740 Bq/m3 to 7400 Bq/m3): EPA recommends action to reduce level within a few months. Sooner for levels at

the upper end of range. Above 200 pCi/l (7400 Bq/m3): EPA recommends action to reduce level within a few weeks. In Canada, Health Canada's guidelines are: Remedial measures should be undertaken in a dwelling whenever the average

annual radon concentration exceeds 200 Bq/m (5.4 pCi/l) in the normal occupancy area.

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The higher the radon concentration, the sooner remedial measures should be undertaken.

When remedial action is taken, the radon level should be reduced to a value as

low as practicable. The aim is to remediate and reduce the radon concentration to less than 200 Bq/m (5.4

pCi/l). If the radon concentration is found to be greater than 600 Bq/m (16.2 pCi/l), the

remedial actions are recommended to be completed in less than a year. If the radon concentration is found to be between 200 Bq/m (5.4 pCi/l) and 600

Bq/m (16.2 pCi/l), the remedial actions should be completed in less than two years.

2.5 Other Measurement Techniques 2.5.1 Overview The following measurement technique provides an example of alternative measurement

techniques. Other measurement techniques are also possible. 2.5.2 Multiple Approximate Readings This measurement technique provides a method to obtain multiple radon gas readings in a

small area such as a building. It uses several cells and allows for an approximate representation of the radon gas levels at various spots at a location.

Due to the short counting time, this method is suited only for radon levels above

approximately 1850 Bq/m3 (50 pCi/l). As equilibrium is not reached and no counting efficiency factor is applied, the result is only approximate.

In preparation for the measurement, the AB6A should be programmed as follows: As a minimum, the following cell parameters: Cell model. Cell serial number. Cell sensitivity.

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Cell system background (cpm). As a minimum, the following Continuous method parameters: Interval Length: 1 minute # of Intervals: 12 # Intervals to Discard: 9 At the first measurement location: 1) Remove the protective cap from the cell and allow the cell to sit in the

measurement location for 5 minutes. 2) Turn on the AB6A and after the boot up sequence: Edit the Continuous method Notes tab to indicate the location of the

measurement. Edit the Detector tab to select the cell that is being used for the

measurement. 3) Attach the cell to the AB6A PMT. 4) Allow the cell to recover from the light exposure for 3 minutes. 5) Start the measurement. It will stop automatically after 12 minutes.



6) Repeat steps 1 to 5 for the remaining locations.

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NOTE A "clean" cell (i.e., A cell that has been flushed and that has not

been used in the past 24 hours) should be used for each location. 7) Transfer the files to the PC for analysis. There will be one file for each location. 8) Average the readings within each file to obtain an approximate reading for each

location. For radon levels above approximately 7400 Bq/m3 (200 pCi/l), the procedure can be

shortened by using only the counts in the eleventh and twelfth intervals or by using eight rather than twelve intervals. There will be some decrease in accuracy.

2.6 Radon Measurements in Buildings Guidelines The measurement procedure described in Section 2.3 can be used for measuring radon gas

concentrations in houses and other buildings. The following sections provide guidelines for radon measurements in buildings. 2.6.1 Quality Assurance Program Guidelines It is recommended that the User establish a quality assurance (QA) program to help

ensure that measurement data are scientifically sound and are of known precision and accuracy. The QA plan should provide for controlled calibrations, replicate measurements, background measurements, routine sensitivity checks, and documentation. By introducing regular alignment and calibration of equipment, duplicate sampling, and participation in an intercomparison program, the QA plan can improve measurement validity. Duplicate samples should be collected to determine the precision of the sampling procedures used. Where a large number of samples are being taken, the number of duplicates can be reduced but should be at least 10% of the radon samples collected.

For intercomparison and reproducibility of measurement results, consistent measurement

procedures should be followed. The guidelines recommended by the United States Environmental Protection Agency (EPA) provide useful procedures for measuring radon gas levels in homes.

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2.6.2 Building Measurement Guidelines The following guidelines have been adopted from the "Interim Indoor Radon and Radon

Decay Product Measuring Protocols" issued by the U.S. Environmental Protection Agency in April 1986:

Building measurements should be made with the building closed as much as

possible. Windows and doors should be kept shut for 12 hours before measurement begins and

while measurements are being taken. Opening and closing of windows and external doors should be kept to a minimum. Air exchange systems (other than a furnace) should be switched off. Measurements should not be conducted during severe storms or strong winds. Avoid taking measurements in or near drafts caused by heating, ventilation, or air

conditioning vents, doors, windows, or fireplaces. The measurement location should be well away from outside walls. The cell should be located at least 50 cm (20") above the floor. It is recommended that the sampling period be at least 24 hours, not including the

four hours required for the system to reach equilibrium. The longer the measurement period the better.

2.6.3 Information To Be Recorded The following information should be recorded, as appropriate, when making measurements

in buildings: Sampling: Method information. Interval length and number of intervals. Location of building and of sample location within building. Degree to which closed conditions exist. Date and start/stop times of measurement. Concentration(s) and calculations. Equipment: Monitor model and serial number. Detector (cell) model and serial number. Monitor HV setting. Monitor DISC setting. Monitor date of last calibration.

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Detector date of last calibration. Sensitivity of detector at last calibration. Pre-measurement system background. Post-measurement system background. Additional information: House construction type. Type of heating and cooling system(s). Habits of occupants. E.g., Smoking habits, use of air conditioning, humidifiers, air

filters, heat exchangers, and clothes dryers. 2.6.4 Data Analysis Once the measurement data have been obtained, it is recommended that the user divide them

into time periods (e.g., In windows of, say, 4 hours, 6 hours, etc.) and calculate an average for each window in order to observe trends. This may be performed automatically by the AB6A if the interval lengths are selected to be 4 hours or 6 hours. The User may also take the raw counts and perform the calculations manually or in a spreadsheet in accordance with Section 2.4.1.

In the absence of local risk assessment guidelines, the guidelines that are provided in Section

2.4.2 may be used to determine the health risk to the occupants. 2.7 Thoron Gas Measurement Because thoron decays rapidly and it is difficult to achieve quantitative measurements,

passive cells are not normally used to try to measure thoron. 3.0 CALIBRATION Please refer to Pylon manual 7940015 - 600P Passive Lucas Type Cell Detector

Calibration Instructions for information and instructions to calibrate the 600P cells. 4.0 CELL MAINTENANCE AND REPAIR The cells require little physical maintenance. The following tips should be heeded: 1) Keep the cell threads clear of dust or dirt.

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2) Do not force the cells onto the AB6A PMT assembly since this may damage the cell and / or PMT assembly threads.

NOTE A small amount of lubricating grease may be applied to the

threads to assist with installation. This may be renewed when necessary.

CAUTION DO NOT ATTEMPT TO THREAD THE MODEL 600P

LUCAS TYPE CELL ONTO OLDER PYLON PRODUCTS SUCH AS THE AB-5, AB-5R, AND AB-4. THE THREADS ARE INCOMPATIBLE. FORCING THE 600P LUCAS TYPE CELL ONTO ANY OF THESE OLDER PRODUCTS WILL DAMAGE THE CELL AND PMT ASSEMBLY THREADS ON THOSE PRODUCTS.

3) When in operation, the cell should be positioned to eliminate the possibility of water

entry. 4) Cells should be flushed with filtered outside air, aged air or nitrogen prior to storing

them. 5) When not in use, the mouth of the cell should be covered to protect the scintillation

material from light. 6) When not in use, the cell should be kept in an air-tight bag to reduce the possible

exposure to radon gas. 7) The outside of the cells may be cleaned with a soft cloth with a mild cleanser. Do

not use isopropyl alcohol to clean the cells and do not allow any cleanser, etc. to come in contact with the ZnS coating on the inside of the cell.

8) The cell should be handled with care. 9) The cell should be returned to Pylon for any repairs.

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5.0 FURTHER INFORMATION 5.1 Suggested Readings American National Standards Institute, 1983, "American National Standard for Radiation

Protection in Uranium Mines", ANSI N13.8-1973. Beckman, R.T., "Calibration Procedures for Radon and Radon Daughter Measurement

Equipment", U.S. Department of Interior, Mining Enforcement and Safety Administration Information Report 1005.

U.S. Environmental Protection Agency, 1980, "Interim Guidelines and Specifications for

Preparing Quality Assurance Project Plans", Washington, D.C., QAMS-005/80. U.S. Environmental Protection Agency, 1986, "Interim Indoor Radon and Radon Decay

Product Measurement Protocols", Washington, D.C., EPA 520/1-86-04. George, A.C., 1976, "Scintillation Flasks for Determination of Low Level Concentrations of

Radon", in Proceedings of Ninth Midyear Health Physics Symposium, Denver, Colorado. George, A.C. and Breslin, A.J., 1980, "The Distribution of Ambient Radon and Radon

Daughters in Residential Buildings in the New Jersey-New York Area", Natural Radiation Environment III, Vol. 2, p. 1272, CONF-780442.

George, A.C., 1980, "Radon and Radon Daughter Field Measurements", Paper presented at

the National Bureau of Standards Seminar on Traceability for Ionizing Radiation Measurements", May 8-9, Gaithersburg, Maryland.

Lucas, H.F., 1957, "Improved Low-Level Alpha Scintillation Counter for Radon, Review of

Scientific Instruments", Vol. 28, p. 680. Public Health Service, 1957, "Control of Radon and Daughters in Uranium Mines and

Calculations on Biological Effects", PHS Report 494, U.S. Department of Health Education and Welfare, Washington, D.C., pp. 41-42.

Rosenstein, M. and Goldin, A.S., 1965, "Statistical Techniques for Quality Control of

Environmental Radioassay", Science, volume 2, pp. 93-102.

manual

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