national committee for the certification of radiation protection officer safety and work procedures...

National Committee for the Certification of Radiation Protection Officer

SAFETY AND WORK PROCEDURES IN RESEARCH

USING RADIATION


ContentsContents

• Introduction• Types and Characteristic of Radiation Sources• Radiation Hazard• Facility Planning• Classification of Work Areas• Work Procedures for Unsealed Sources• Procedure in Working with Sealed Sources• Safety Equipment• Transportation• Treatment and Disposal of Waste• Monitoring


Radiation in Research

Education IndustryMedicine Agriculture

IntroductionIntroduction


Sources of Radiation in Research

Radionuclide Irradiating Apparatus

X-Ray Machine Linear Accelerator

Nuclear Reactor

IntroductionIntroduction


Types of Radiation SourcesTypes of Radiation Sources

The first step in managing radiation hazards is to identify the types and characteristics of the radiation source

Types and Characteristics of Radiation Sources


Nuclear Reactor

Sealed Radioactive

Sources

Irradiating Apparatus

Unsealed Radioactive

Sources


• There are two types of reactor nuclear: Nuclear power plant Research reactor

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• There are numerous types of irradiating apparatus used in research. Examples: X-rays XRD XRF XPSS ESM machines Linear accelerator etc

• Unlike radionuclide, these radiation sources will only emit radiation when high voltage is applied to it or when it is switched ON. Safety engineering features are built into their design.




• Radionuclides may be categorized into:

Sealed radionuclideso Sealed radionuclide or sealed source is radiation source consisting

of any radioactive material, nuclear material or prescribed substance firmly incorporated in solid and effectively inactive material, or sealed in an inactive container of sufficient strength to prevent, under normal conditions of use, any dispersion of its contents.

o Sealed sources when intact posed an external radiation hazards.

Unsealed radionuclides o These are exposed radionuclides usually in solid, liquid and

gaseous forms. o Unsealed radionuclides posed internal and external radiation

hazards.




Characteristics of RadiationCharacteristics of Radiation

Quality (e.g. types of radiation the sources emit, i.e. alpha, beta, gamma, neutron and heavy charged particles).

Radiation of different quality exerts different Linear Energy Transfer (LET). LET is defined as the amount of energy transferred to the media per unit distance it traverses in the media (keV -1).

Radiation quantity

• source activity (Bq)

• activity concentration (Bq ml-1 or Bq g-1)

• dose it produces (Sv, Gy)




3 categories of radionuclide are used in research3 categories of radionuclide are used in research

Radionuclides with long half-lives Radionuclides

with medium half-lives Radionuclides

with short half-lives




Types of Radiation HazardTypes of Radiation Hazard

Radiation HazardRadiation Hazard

External Radiation Exposure

Internal Radiation Exposure

Contamination


• Radiation hazards may be divided according to:

External radiation exposure

o Hazard is related to high penetrating radiation source outside the body.

o Such radiation (e.g. electromagnetic radiation, high-energy beta and neutron) could penetrate the skin and body to cause harm to the body.

Internal radiation exposure

o Hazard is related to radiation source in the body. o It involves radiation with low penetrating power but usually

with high LET that can cause significant internal damage (e.g. alpha and beta particles).



Contamination

o Contamination involves deposition of radionulide on the outer surface of the body (e.g. skin), or on wall and floor surfaces of building.

o Contamination involves unsealed radionuclides or originally sealed radionuclides that leaks due to a compromise seal.

o Radionuclide contamination is both an internal radiation hazard when it is ingested, inhaled or penetrated the skin and into the body, and an external radiation hazard if the radiation is highly penetrating.



• Selection of locations and arrangements of work areas, radioactive waste storeroom, and office

Facility planning may involve selection of locations and arrangements of work areas (including laboratories), radioactive waste storeroom and office. Such selections depend on:

o Types of radiation used;o Physical properties of radionuclides;o Quantity of radionuclides to be kept; o Methods of using radionuclides; ando Methods of disposing the radionuclides.

Facility PlanningFacility Planning


• Construction consideration

Facility construction is dependent on types of radiation, physical and chemical properties of radionuclide, quantity of radionuclides to be used, stored and disposed.

Consideration must take into account the stage of construction (e.g. whether it is on the plan or during modification).

It is relatively cheaper to make any modification of facility at the planning stage compared to when the building or facility is fully completed.



• Work place design

Work place design depends on:

o Types of radiation;o Radionuclide quantity;o Sealed and unsealed conditions;o Methods of use; ando Storage and disposal of radioactive waste.

Work place is designed to provide for protection and safety in compliance with the applied standards.




Design must meet engineering, performance and functional specifications.

Design must meet quality norms commensurate with the protection and safety significance of components and systems.

Design must incorporate the need for classification of working areas, storerooms to store radiation source and waste.

If radioactive dust or gas is to be used than a proper ventilated room must be considered.




A control barrier must be erected at the entrance of a controlled room used to handle unsealed sources.

Radiation monitoring equipments (e.g. hand and foot monitor, survey meters etc.), and personal protective equipment are placed at the entrance/exit to the working area.

Specially built shielded room must be erected for irradiating apparatus and sealed sources.




Shielded rooms for irradiating apparatus and sealed sources have some general requirements. These include:

o Room is designed and built according to the standards required for its purpose;

o Room must be classified and demarcated appropriately; ando All necessary control measures and procedures in accordance to its

classification must be enforced.

Besides safety, the overall work place design must provide for comfort of work and security of the facility.




Work place design includes storage area. Storage area should at least:

o have adequate shielding for the types of radiation; o allow easy access to stored materials;o be ventilated;o be under locked security (e.g. bomb pit for storing radiation sources

used in NDT);o have appropriate label with warning signage; ando include dedicated delay tanks for temporary storage of liquid waste.

Work place design is not limited to the planning stage. Modification and alteration of work place could come when new work activity is introduced to the facility. Consequently, workplace design comes after construction of the facility.



Radiation Work AreasRadiation Work Areas

Clean Area Supervised Areas

Controlled Area

Classification of Work AreaClassification of Work Area


• Clean area

Area where the expected maximum dose for that area does not exceed the dose limit for a member of the public.

• Supervised area

Work area for which the occupational exposure conditions are kept under review even though specific protective measures and safety provisions are not normally needed.

Classification of Work AreasClassification of Work Areas


• Controlled area

Work area where specific protection measures and safety provisions are or could be required for controlling normal exposures or preventing the spread of contamination during normal working condition, and preventing or limiting the extent of potential exposures.

Area where the expected maximum Permissible Dose Limit is greater than 3/10 (6 mSv y-1).

This area is subject to special rules for the purposes of protection against ionizing radiation and to which access is controlled.

Classification of Work AreasClassification of Work Areas


• One method in developing safe work procedure is through Job Safety Analysis.

• Safe work procedure must be:

Written in a language that is concise, precise and easy to understand by the intended user; and

Must include not only the method of carrying out the task but also the elements of safety and emergency actions to be taken when the needs arises.

Work Procedures for Unsealed Sources



• All safe work procedures must be tested before use and reviewed periodically to ensure their relevancy and appropriateness for the intended purposes.

• All safe work procedures need to be explained to users. While most procedures require briefing and explanation some require prior training, while others need to be further complemented with supervision.

• All safe work procedures must be developed following radiation risk assessment.




• Handling techniques

The objectives of handling techniques in works related to radiation source are to reduce exposure and to prevent contamination.

Handling techniques involve:o The use of shielded room for work with very high radioactivity;o The use of remote control apparatus (e.g. tongs) to handle sources;o Procedure to transfer liquid sample (e.g. should never pipette with

the mouth);o The use of suitable waste bin for different radionuclides, and

physical properties of waste (e.g. liquid, solid or gaseous waste); and

o The use of correct personal protective equipment when handling unsealed radionuclides. E.g. the use of rubber gloves and laboratory coats while handling unsealed sources.




• Separation of activity and dilution of concentration

The safest way to work with radiation source is to use the optimum amount or quantity. Radionuclides are not cheap and a posed radiation risk when used in excess.

Lower activity means lower doses. If spillage and contamination occur, then the cleaning up process will only involve low activity and concentration.

It is important to follow the recommendations of supplier on the need to separate and dilute the radionuclides.




• Radioactive gases

Radioactive gases can cause internal radiation exposure. The use of proper ventilation system with continuous monitoring of discharge must be installed in facility using radioactive gases.

Vertical laminar flow may be considered for use in handling radioactive gases but care must be taken to prevent air turbulence in the hood.

All exhaust system related to possible discharge of radionulide outside the working must be strictly monitored and controlled. No release of radioactive materials for disposal, recycling or reuse is allowed without prior written approval of the appropriate authority.




• Handling low activity sources

This is normally related to handling environmental materials containing low activity naturally occurring radioactive sources. Although the source activity is low, care must always be taken to ensure unnecessary exposure to the radiation.

Care must also be taken to ensure that the level of activity remains below the permissible level (e.g. ALI and DAC) approved by the authority.

Area monitoring of work area and storage room must be carried out continuously.

The concept of ALARA must always be used during handling of low activity sources to ensure the lowest achievable dose exposure.




• Time, shielding and distance

Time, shielding and distance are three principles of methods of control that can be incorporated into engineering as well as management controls of radiation hazard.

Longer exposure times means higher dose of exposure and vice versa.

Thickness, density as well as types of materials (Z number) determine the effectiveness of shield against a particular radiation quality. Generally thicker material increases the attenuation of radiation intensity. High Z materials (e.g. Pb) are effective in attenuating electromagnetic radiation (e.g. gamma and x-rays). Low Z materials (e.g. H) are effective in attenuating neutron sources.

Inverse square law is used to reduce dose through distance.

Procedure in Working with Sealed Sources



• Leak test

A radiation leak is divided into two:

o Design leak or allowed leakage by the manufacturer on a particular apparatus; and

o Defect of sealed sources, apparatus or machine.

Leak test is a physical test conducted on sealed sources to ensure the integrity of the source capsule. Leak test is also done on irradiation machine (e.g. X-ray machine).




• Leak test

Level of radiation leakage is determined based on the deviation of measured dose from the dose of design leak.

Purpose of leak test is to confirm the classification of sealed sources and performance of irradiation machine is maintained at all times during its use.

Leaks due to defect of sealed sources, apparatus or machine must be assessed periodically (interval is prescribed by the authority) or whenever damage of the source (if radiation source, it is the capsule or seal) is suspected, or when there is a presence of contamination (allowable leaked activity = 185 Bq).




• Methods used in leak test

Test methods used in detecting and measuring leaks from sealed sources may be divided into two:

• Radioactive methodso Example of radioactive methods include:

» Wipe (smear) test» Cellulose tape test» Scrub test» Soaked-I test» Soaked-II test





Test methods used in detecting and measuring leaks from sealed sources may be divided into two:

• Non-radioactive methods o Examples of non-radioactive methods include:

» Vacuum bubble test» Hot liquid bubble» Gas pressurization bubble test» Helium test» Helium pressurization test» Water pressurization test





Counting equipment is used in leak tests.

Counting equipment used in leak tests are similar to that used to detect the types of radionuclide, radiation as well as to measure the activity of the leak source.

Liquid scintillation counters may be used for beta emitters while gamma counters may be used to measure gamma emitters.




• Storage equipment

Storage equipment include portable radioactive waste container for temporary storage of waste emitting different types of radiation emitters. (e.g. lead pot).

• Transport equipment

Transport equipment may be divided into on-site and off-site equipment.

On-site transport equipment is usually designed for transporting low activity sources.

Sources are carried in transport container with secondary shielding by trained personnel.

Safety EquipmentSafety Equipment


• Laboratory equipment

Containers are used to temporarily store radioactive materials. Containers to store gamma emitters must be lead lined. Containers may be made of disposable materials (e.g. plastic bags) that may be disposed after used.

Disposable tools include disposable pipettes, and dishes. Disposable tools are used with unsealed sources.

Remote arm (or tongs) may be used to handle radiation sources at a distance.

Shields are another example of laboratory equipment. Shield may be portable or permanently fixed. Example of portable shields for beta particles is Perspex.



• Personal Protective Equipment (PPE)

PPE are used to reduce the likelihood of exposure and/or contamination, and their radiological impact should exposure or contamination do occur. Examples of PPE include overalls, aprons, rubber gloves, footwear, safety goggles and visors, and even respirators and breathing apparatus.

PPE such as lead apron and lead glasses are used to reduce exposure to penetrating ionizing radiation (e.g. x-ray and gamma-ray).

PPE should always be the last choice of radiation risk control after all other risk control measures have been considered and preferably implemented. Preference should be given to engineering control followed by administrative control in controlling radiological risk.



• Movement of radioactive material within and off-site of the premise shall be carried out according to Radiation Protection (Transport) Regulations 1989.

• Get an approval from AELB 14 days before transportation.

TransportationTransportation


• Research facility produces radioactive wastes through the use of unsealed sources. These wastes could be the element itself or the radionuclides tagged to a non-radioactive compound.

• Problem of disposing the radioactive waste is now complicated by the presence of chemical compounds, which by itself could be toxic to the ecosystem.

Treatment and Disposal of WasteTreatment and Disposal of Waste


• Radioactive wastes mix with other toxic chemical compounds must be treated before disposal. Treated radioactive wastes may be disposed either through delay and decay, dilute and disperse or concentrate and contain.

Long-lived radionuclides or radionuclides with long half-life (e.g. U-238 and Th-232) require them to be kept in a proper container and stored in a safe place.

Radionuclides with short half-life (e.g. P-32) may require that it be temporarily stored to facilitate the radionuclides to decay to its stable form before being treated in a non-radioactive procedure or discharged into the environment.

Radionuclide may be diluted and dispersed if they are naturally found in the environment and is at a concentration similar to that in the environment (e.g. H-3 and C-14).



• Treatment process for radioactive waste does not differ from other non-radioactive waste except for the needs to provide for shielding against ionizing radiation.

• General procedure of waste management involves: classification of the waste pre-treatment treatment conditioning storage disposal



• Classification of waste

Is done based on its half-live and activity. IAEA proposed that radioactive waste be classified according to:

o Exempted waste (EW): its disposal results in an exposure of less than 0.01 mSv to the public;

o Low and intermediate level waste with short half-lives (LILW-SL);o Low and intermediate level waste with long half-lives (LILW-LL): A

30 years half-life is used to differentiate between short and long half-lives; and

o High level waste (HLW).

Waste may also classified according to the physical properties of the waste, i.e. solid, liquid or gaseous wastes. Except for research reactor facility, most research facility does not produce high-level waste.



• Pretreatment At this stage the waste is categorized and separated according

to its physical state or stabilizing it with specific materials. Pretreatment helps to reduce the volume of the waste.

• Treatment The main purpose of treatment is to reduce the waste volume. At

this stage the principles of delay and decay, and concentrate and contain is applied where practicable. Treatment may also increase the volume (e.g. in dilute and disperse).

• Conditioning At this stage, binding matrix is added to liquid or solid waste to

become homogenous solid monolith with low leach ability.



• Storage

With some costs research facility may send their waste to MINT for storage. Otherwise some research facility stores their own waste. Delay tank should be used for temporary storage of short half-lives radionuclides before disposal into the environment or treated as non-radioactive waste.

• Disposal

Upon treatment radioactive waste will eventually be disposed off into appropriate repository. MINT does provide repository for organization that are unable to dispose of their waste. Wastes from sealed sources are disposed according to the procedures approved by the appropriate authority.



• Objectives of monitoring are to obtain an estimate on the doses received by radiation workers in the controlled and supervised areas.

• Two types of monitoring that need to be done in a research facility: area monitoring, and personnel monitoring.

• In the case of personnel monitoring, monitoring is carried out on exposures from internal and external radiation. One example of internal radiation monitoring is the use of whole body counter.

MonitoringMonitoring

X-Ray


• Monitoring starts before operation, continues during operation and after operation ceases. Such monitoring practice is pertinent for facility that uses unsealed radionuclide sources.

• Radiation monitoring is carried out using specialized equipment that includes:

Dosimeters (pocket dosimeters, film and TLD badge) are used to measure accumulated dose received by radiation workers over the preset time; and

Geiger Mueller survey meters may be used to monitor external radiation including detecting and measuring surface contamination.

MonitoringMonitoring

Alpha

Beta and Gamma


Summary


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national committee for the certification of radiation protection officer safety and work procedures...

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