Chapter 6: Radiation and Contamination Surveys
Prevention of the spread of contamination and excessive radiation exposure is the responsibility of the Authorized User. The Authorized User is also responsible for providing radiation detection equipment to monitor removable contamination and external radiation exposure levels as appropriate. Radiation detection devices, such as liquid scintillation counters, gamma counters, and portable survey instruments, must be available.
During the monthly survey, records-keeping systems and the Radiation Safety Notebook should be reviewed for completeness and orderliness. Waste storage, records and security should be examined also during the monthly survey.
When higher energy beta emitters, such as P-32, or gamma emitters, such as I-125, Na-22, etc. are used in the laboratory, the monthly Authorized User survey must consist of a wipe test and instrument survey using a portable, handheld survey meter. The instrument make, model number, serial number, calibration date, and readings must be recorded on the written survey report. Instrument surveys are specified in the radiation source authorization, if required. When lower energy beta emitters; such as H-3, C-14, or S-35, or small quantities of gamma emitters contained in commercial test kits, are used in the laboratory, only wipe test surveys are required.
During the monthly Authorized User survey, records-keeping systems and the Radiation Safety Notebook should be evaluated for completeness and orderliness. Waste storage, records, security, and the overall laboratory radiation safety program should also be reviewed. If no radioactive material has been used during a month, a statement of that fact may be entered into the Radiation Safety records in lieu of a recorded survey. However, a record of the survey performed after the last use must be on file, showing that all radiation and contamination levels are within the specified guideline limits. For Authorized Users having more than one room authorized on their radiation us license, a statement of “No Use” may be entered for the individual rooms where radioactive materials was neither used nor stored (including waste) for the month. As such, a survey is required only in those rooms where use or storage occurred during the calendar month. The Radiation Safety Office may, according to particular conditions including quantities or types of materials and an Authorized User’s safety record, set radiation safety survey schedules specifically designed for named laboratories or Authorized Users.
- Monitor hands, arms, front of lab coat and other potentially contaminated areas.
- Monitor bench tops, floor areas, equipment, etc.
- Monitor hands and clothing before leaving the laboratory.
Do not use a survey meter that has not been calibrated within the past year for any purpose. Never use a survey meter that indicates “low batteries”. Any meter that is not operating properly or is out of calibration must be tagged or labeled as “Out-Of-Service”. Low batteries should be replaced at once. If an instrument is put in storage, the batteries should be removed. Old or spent batteries are prone to leakage and can ruin an instrument.
When radioactive contamination is found above the action levels, clean and decontaminate the area. Re-survey with wipe tests and record the results to document adequate cleanup.
Areas in which the radiation exposure level exceeds 5 mrem/hr must be designated as a “Radiation Area” and posted with an appropriate sign (available from EHS). When such levels are expected, the RSO will indicate specific procedures to be followed when the “authorization” to use radioactive materials is issued. When such conditions arise that are not covered by the authorization, the RSO must be contacted immediately.
Contamination – EHS records removable contamination levels in terms of disintegrations per minute (DPM) per 100 square centimeters (standard areas to be covered by a “wipe”). Wipe test survey results by Authorized Users must also be recorded in DPM. Counting efficiencies used to convert from CPM to DPM may be stated in the Authorized User’s records in lieu of converting to DPM. Typical liquid scintillation counting efficiencies are 20 percent for H-3 and 50 percent for other radionuclides. Laboratories may use the same counting efficiencies for wipes or use their own established efficiencies.
Actions to be taken as a function of contamination level are:
|Contamination Level, DPM||Action|
|Below 600 DPM||
|600 DPM and Above||
|Special Situations: Interiors of posted hoods, storage cabinets, refrigerators, sinks, etc.||Action|
|Below 2000 DPM||
|2000 DPM and Above||
|Special Situations: Interior of dedicated, posted,
sole user microfuges, speedvacs and centrifuges:
|Below 15000 DPM||
|15000 DPM and Above||