Guide for Performing Radiation Surveys
Introduction:
Routine laboratory surveys are an important part of the radiation safety program and are required to be performed by radiation laboratory personnel following the use or transfer of radioactive material. Surveys provide a direct measure of area radiation levels and detect the presence of radioactive material inadvertently spilled on a person, surface, or piece of equipment. Surveys are therefore an indication of the radiation hazard present either during or after an experiment. It is vital that individuals working with radioactive materials are aware of accepted procedures for performing such surveys. The information which follows is a suggested Guide for performing surveys of laboratory areas. Questions about the mechanics of performing surveys or the interpretation of this Guide may be referred to the DMPRS.
What is a survey?
A survey is an evaluation of work areas, instruments and apparatus, floors, sinks, faucet handles, drawer fronts, doorknobs, telephones, light switches, refrigerators, etc. for the presence of radioactive contamination.
Survey results should be documented but certain actions within the laboratory require that surveys be performed and documented. Required actions prompting a radiation survey are presented below. All survey records should be kept so that all information is readily obtainable by laboratory staff or members of the DMPRS.
How often are surveys to be performed?
Individuals are required to survey themselves and their work areas on an “as used” or “daily basis”. The DMPRS recommends frequent surveys of hands and other skin areas to identify and rectify contamination, thus preventing significant doses and internal exposures. An operating survey meter should be accessible whenever working with radiation.
The Permit Holder of a radiation laboratory is required to have a radiation survey conducted under the following conditions:
1. After each day of radioactive material usage/experimentation.
2. After transfer of radioactive material from stock solutions.
3. After each experimental run if there is a possibility of a change in radiation levels or contamination.
4. After a minor radioactive spill clean-up or emergency.
NOTE: All Radioactive spills or emergencies, unless minor, are to be reported to the DMPRS ASAP!
What Type of Survey Do I Need to Perform?
The type of survey that you perform depends on what type of radioactive material is used. Depending on your work and the isotopes you are working with you may be required to perform:
-Contamination Surveys (i.e. wipe surveys or swipes)
-Area Exposure Survey (exposure readings mR/hr)
What is contamination?
The laboratory must be aware of the two types of radioactive material contamination:
Fixed Contaminationis that which has become bound by chemical or other means to the surface upon which it was deposited. This form of contamination can only be detected by a survey meter through a radiation area survey. Because it is fixed to the surface, a wipe test will indicate little or no activity. A meter survey may indicate that larger quantities are indeed present on the surface.
Removable Contamination is that which may be wiped off a surface or object, similar to dust on a piece of furniture. The presence of removable contamination is determined by wipe tests and in some situations by the use of a survey meter. If contamination is present in large enough quantities and is removable, it also may be detected by a survey meter when a wipe test of the surface is placed near the probe.
What are contamination surveys?
Contamination surveys (also called swipes or wipe surveys) are performed to detect the presence of removable contamination and are necessary when using radioactive liquids, solids, or gases. The section above “How Often are Surveys to be Performed”, instructs users on the requirements for performing these surveys.
How to perform a contamination survey for detection of removal radioactive contamination?
- Obtain a blank survey form (or your laboratory’s survey log book) and decide which areas you wish to test for contamination.
- Record your name and the date and document the areas you plan to analyze on your survey form.
- Find out what material the laboratory uses to perform its wipe test. A Whatman 41 filter or its equivalent is best used for contamination testing purposes.
- Take the wipe paper, and wipe an area equivalent to roughly 100 cm2 in an area of interest.
- Determine the Removable Contamination Limits for which the laboratory must meet. A 100 cm2 area must have removable contamination greater than or equal to the following limits to be considered contaminated:
- Beta/gamma radiation (except tritium) - 500 dpm/100cm2.
- Tritium - 1,000 dpm/100cm2.
- Determine the radiation wipe analysis method suitable for the isotope(s) used:
- High energy beta/gamma source – Open window Geiger Counter (if approved by DMPRS).
- Low energy beta, high energy beta – Liquid scintillation counter, gas flow proportional counter.
- Analyze the sample as appropriate for the analysis method used.
- If the removable contamination limits exceed those detailed above in step 5, contact the Permit Holder. In any case, alert the DMPRS before attempting to handle the contamination. Options for handling contaminated areas include:
- Clean up the contamination until measurable radiation levels fall below the contamination limits.
- Posting the area as a contaminated area.
- Once the contaminated area has been cleaned, perform one last recorded radiation contamination survey to ensure area falls below the contamination limits described above.