Part 330: Radioactive Materials Contamination Surveys
- 330.10 Introduction
- 330.20 Frequency of Surveys
- 330.30 Contamination Survey Methods
- 330.40 Requirements for Decontamination
- 330.50 Personal Surveying
- 330.60 Decontamination Guidelines
Ensuring contamination does not exist during and after the use of radioactive materials is a key component of any radiation safety program. All users of unsealed radioactive materials must conduct contamination surveys as required below. Records of the contamination surveys, regardless of whether or not contamination is found, must be kept in a clear and concise format that can be easily understood by the radiation safety officer or other inspector. All records of personnel and area contamination surveys must be retained by the authorized user for 3 years.
Contamination surveys must be conducted of the immediate area, storage areas, and any other area that has a possibility of contacting radioactive material. The frequency of these surveys will be determined initially by the Radiation Safety Committee when a new application is reviewed and approved.
After an application is approved, survey frequency will be determined by the radiation safety officer every calendar quarter. The survey frequency is based on the amount of radioactive material purchased within the last twelve months averaged over the twelve month period (or the appropriate time period if the user has received authorization within the last twelve months). This survey frequency will then apply for the next calendar quarter.
These survey frequencies will be either daily, weekly, or monthly, depending on the above determinations. A daily survey is defined as conducting a survey within the twenty-four hour period from the time radioactive materials were first used. A weekly survey is defined as conducting a survey within the seven day period from the time radioactive materials were first used. A monthly survey is defined as conducting a survey within the thirty day period from the time radioactive materials were first used.
330.30 Contamination Survey Methods - The method required for determining the presence of contamination is the wipe test and, for certain isotopes, survey by an appropriate radiation detection instrument. The following are the two methods of performing contamination surveys:
- Wipe tests:
- The wipe test shall consist of wiping an area ten centimeters by ten centimeters with a commercially available wipe, swab, filter paper or other suitable medium. There must be a suitable number of wipe tests taken to adequately survey the area of radioactive material use.
- The samples must be counted in a detection device appropriate for the type of radiation emitted. The counting procedures must address the length of time each sample is counted, the energy of the isotope, and the accuracy of the measurement. The counting instrument's sensitivity (or minimum detectable activity) must also be sufficient to detect with confident accuracy the maximum allowable contamination level (see Part 900).
- In addition to the wipe samples, a blank wipe and a standard must also be counted for each survey. For a large number of samples, use one blank for each ten to twenty samples.
- The efficiency of the instrument must be calculated for each isotope, and the survey results must be reported in the units of dpm per 100 cm2. The results of contamination surveys by wipe tests can be recorded on the Contamination Survey Form RSM-3 or the equivalent information can be recorded in a user's log book.
- Allowable levels of contamination are listed in Part 900.
- Survey with radiation detection instruments (or survey meters):
- The use of a survey meter is required for high-energy beta emitting (where Emax is equal to or greater than 200 keV) and gamma or x-ray emitting isotopes (see Part 900).
- All survey meters and detectors must be approved by the radiation safety officer.
- Prior to each survey, the batteries must be tested, and a check standard must be used to establish that the survey meter is operable and properly detecting the radiation field.
- The area surveyed must be large enough to adequately cover the area of radioactive material use. In areas where a radiation field already exists, using a survey meter and detector for contamination surveys will not be possible.
- The results of contamination surveys by survey meter can be recorded on the Contamination Survey Form RSM-3 or the equivalent information can be recorded in a user's log book. Background radiation levels must also be recorded.
- Allowable levels of contamination are listed in Part 900.
- Survey meters and detectors must be calibrated annually. A certificate of calibration will be required as verification that the instrument has been properly calibrated.
- Survey meters and detectors can be calibrated by returning the meter and detector to the manufacturer or other commercial vendor providing calibration services. While a user's meter and detector are being calibrated, a survey meter and detector may be borrowed from the radiation safety officer.
- After calibration, the efficiency of the survey meter will be determined by the radiation safety officer.
- If contamination is detected, the area or item must be cleaned and re-surveyed until contamination levels are below those specified in Part 900.
- If the contamination cannot be removed by appropriate cleaning methods, and if it is contaminated with a short-lived radioisotope (i.e., less than 65 day half-life), the item, instrument or area may be stored or shielded and contamination allowed to decay to an acceptable level. This type of procedure must be approved by the radiation safety officer.
It is recommended that hands, shoes (including the bottoms), and the body be surveyed for contamination prior to leaving the area where radioactive materials are used.
The following are some guidelines for preventing radioactive contamination or for decontaminating a contaminated area:
- Work surfaces should be covered with an absorbent/plastic-backed laboratory paper. For additional protection, trays should also be used when handling radioactive materials. If radioactive materials are spilled, the resulting contamination of the work surfaces or other items will be minimized or eliminated.
- To decontaminate work surfaces or items that have come in contact with radioactive materials, there are many commercially available detergents that are effective in removing radioactive contamination. These are available in ready-to-use formulations, concentrated solutions and in aerosol foams.
- If detergents are not effective in removing contamination, then dilute acid or caustic solutions may be necessary. Please use caution when working with these types of solutions and wear the proper personal protective equipment.
- If contamination cannot be removed, see Part 330.40 and/or contact the radiation safety officer or designee.