RADIOACTIVE SPECIMENS IN MUSEUM COLLECTIONS (1996)
Marc L. Wilson, Head, Section of Minerals, The Carnegie Museum of Natural History, Pittsburgh, PA
The Carnegie Museum of Natural History (CMNH) recently completed a review and renovations of its radioactive minerals exhibit and storage facilities. Applied Health Physics, Inc. (AHP), of Bethel Park, PA, a licensed health physics consultant, was retained to conduct a radiological safety and compliance audit with the goals of evaluating potential radiological risks and to ensure compliance with regulatory standards and procedures. Presented here are the findings of AHP and remedial actions taken by CMNH. It is stressed that no safety hazards were identified in CMNH, all remedial actions were appropriate as of the date of the audit, and, while satisfied with the results of the project, this report does not represent an endorsement of AHP.
It was the opinion of AHP that USNRC guidelines for materials licensees, as set forth in Title 10 of the Code of Federal Regulations Part 20 [10 CFR 20], were aimed at artificially produced materials and may not be directly applicable to naturally occurring radioactive specimens in collections. However, AHP and CMNH agreed that prudence dictated not only following USNRC guidelines, but seeking to "control radiological risks to levels that are As Low As Reasonably Achievable (ALARA)." For CMNH, ALARA was targeted as 10% of USNRC allowances.
At this point, it is important to understand the distinction between a safety hazard and a regulatory hazard, as they impact a museum. Radiological risks are safety hazards, or health risks, and should be identified and eliminated to provide a safe working and viewing environment. Regulatory hazards are more subtle in that they result from incomplete compliance with applicable state and federal regulations, which may be focused on potential rather than actual health risks. Thus, even though no practical health risk exists, a museum may be in violation of regulations, (a regulatory hazard), and be liable to fines, lawsuits, and bad PR.
The following are quoted from the AHP report. "The rem (roentgen equivalent man) is a special unit of dose equivalent. The dose equivalent in rems is numerically equal to the absorbed dose in rads (radiation absorbed dose) multiplied by the quality factor of the radiation, the distribution factor, and any other necessary modifying factors. The rem is further divided into millirems (mrem; 1 rem = 1,000 mrem) and microrems (μrem; 1 mrem = 1,000 μrems). The SI doseequivalent unit is called the sievert (Sv). One sievert equals one hundred rem (1.0 Sv = 100 rem)." "Title 10 of the Code of Federal Regulations Part 20 [10 CFR 20], both the current and the revised regulation, stipulate (a) 'Each licensee shall conduct operations so that (2) The dose in any unrestricted area from external sources does not exceed 0.002 rem (0.02mSv) in any one hour' [10 CFR 20.1301 (a) and (a)(2)]." And, "Current radiation dose standards for individuals in restricted areas (i.e. radiation workers) limit radiation exposure to the whole body, including the lens of eyes, to 1,250 mrem per calendar quarter. Non-radiation workers (i.e. members of the general public) are allowed to receive one tenth of that exposure or 125 mrem per calendar quarter. In the revised version of Title 10 of the Code of Federal Regulations Part 20 [10 CFR 20], due to become effective on January 1, 1994, this limit has been changed to 'An eye dose equivalent of 15 rems (0.15 Sv) per year' [10 CFR 20.120 (a)(2)(i)]."
Thus, estimates of whole body exposure, as well as point source intensities, should be made if anyone works with, or has potential for exposure to, radioactive materials. If estimated or measured levels are significant enough to be considered questionable, it is highly recommended that a licensed health physics consulting firm be retained to review the situation. This is prudent not only for eliminating potential safety hazards, but as insurance against possible regulatory hazards and their potential legal repercussions. The consultant will be able to evaluate all risks and recommend appropriate actions which may include training in radiation safety, modification of signage, purchase of safety equipment, monitoring via personnel dosimetry (film badges), etc.
The results of the CMNH radioactive audit were fourfold. First, it was determined that the collections contained more radioactive specimens than needed to fulfill the museum's mission. Specimens were evaluated and those with no scientific, historic or economic merit were deaccessioned and disposed of as radioactive waste by AHP.
Second, storage facilities were renovated to restrict access, provide proper shielding, and provide proper signage (a rule of thumb is that if potential for exposure exceeds 2,000 microrems/hr, signage is required). CMNH radioactive specimens are now stored in transparent ziplock bags in a leadlined safe located in a restricted access area. This allows viewing of the specimens by authorized persons without exposing the storage facility to possible specimen dust contamination.
Third, the Hillman Hall of Minerals and Gems exhibits were renovated and radioactive minerals are now displayed only in the Radioactive Minerals exhibit. The radioactive profile within the display case has been lowered and lead glass was installed with the result that no point, front, sides, or back, of the exhibit exceeds regulatory limits.
Fourth, it was determined that adequate ventilation was present in CMNH to minimize potential for radon buildup.
Finally, safety and monitoring equipment were evaluated and upgraded. Equipment recommended for museums with radioactive mineral specimens or fossil bones likely to contain radioactive mineral species are: a good handheld microremcalibrated scintillometer; a respirator with filters for radionuclide dusts; disposable latex gloves; disposable paper coverallsuits (for big, messy jobs); adequate eye protection; and properly labeled disposal bags for all contaminated refuse.
There are three points to remember if you have radioactive specimens in your collections: (1) If you think you have potential for a problem, call a licensed professional. (2) Selfmonitoring is less expensive than hiring an outside service: buy a good scintillometer. (3) Do it before you have to.