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Radiation Surveys

The ORCBS will make independent surveys of all active Class B radioisotope labs at least quarterly, and all Class C laboratories at least biannually. Such things as inventory assessment, contamination control, personnel monitoring, training and waste disposal practices will be addressed during these surveys. (See the survey checklist used by the ORCBS in the Appendix).

Copies of the results of surveys will be forwarded to the principal investigator, and a recheck may be conducted in the event problems have been detected that need corrective action. The MSU Radiation Safety Committee may accompany the ORCBS on surveys as deemed necessary for problem laboratories or for purposes of auditing the radiation safety program.

Surveys are to be conducted by the project investigator or his/her designee in conjunction with the ORCBS surveys. Each lab that is actively using isotopes must conduct radiation surveys weekly, monthly or quarterly, depending on the types and quantities of radioactive materials present in the laboratory. By doing this, the potential for exposures can be evaluated and reduced, if necessary. Records of these surveys must be maintained for review.

When removable radioactivity is found, the area must be decontaminated and then re-surveyed and documented. Detectable levels of removable contamination should be removed, and non-removable contamination should be labeled and shielded whenever possible in order to maintain ALARA limits.

It is understood that certain areas may be routinely contaminated, such as internal parts of equipment and the inside areas of glassware, and that it may not be practical to decontaminate these surfaces. If this occurs, signs must be posted and protective clothing and gloves should be used when in contact with these areas. In some cases, such as ³²P contaminated equipment, shielding is required.

Limits for removable contamination are listed in the table below. Radioactive contamination found at or above these levels must be decontaminated or shielded and labeled. (Therefore, one of the advantages of using disposable lab paper on the benches is that one only has to dispose of the contaminated area of the paper in the radioactive waste, rather than decontaminating or shielding.)

RADIOACTIVE CONTAMINATION LIMITS
AT MICHIGAN STATE UNIVERSITY

Most of the radioisotope use areas on campus are treated as restricted areas, and are characterized as locations with controlled access and have proper radiation safety controls in place. Contamination limits for surveys are the controlled and unrestricted area limits, due to the ALARA programs required of licensees.

Radioisotopes classified as high risk include ⁴⁵Ca, ²²Na, and ⁶⁰Co. Low/moderate risk radioisotopes include ³²P, ³H, ¹⁴C, ³⁵S, ¹²⁵I, ⁵¹Cr and ¹¹¹In. Remember that the ALARA requirement must be adhered to in the above limits, meaning 10% of the limits, where possible. (For some radionuclides, it is impossible to achieve less than the contamination limits, since the instrumentation and normal backgrounds prevent any increased sensitivity. For others, sensitivity may exist where it is realistic to achieve 10% of the contamination limits.)

Routes of Exposure to Radiation

Radiation Safety Manual Table of Contents