Achieving ALARA When Retrieving Multi-Curie Sources
C. B. Martel
The use of multi-curie gamma emitting radioactive sources has become the standard for conducting nondestructive testing worldwide. Often, these sources are used in industrial settings which involve their remote manipulation from shielded containers to expose radiographic film, then retraction into the shield. For a variety of reasons, events can occur in which a radioactive source assembly cannot be retracted into the shield, resulting in an emergency situation that will require a retrieval operation. Retrieval operations typically require individuals to enter areas with high radiation intensities to implement pre-planned actions intended to return the source to the shield. An informal review of industrial radiography retrieval events was performed, and the data showed that individuals receive an average of 0.02 mSv per 37 GBq (2 mrem per Ci) of the source retrieved, regardless of the isotope. However, an informal review of retrievals conducted by individuals specifically trained in retrieval planning and implementation techniques was performed, and the data showed an average dose to personnel of 0.002 mSv per 37 GBq (0.2 mrem per Ci). Ensuring that dose to the retrieval team members is ALARA (as low as reasonably achievable) is a primary goal of a retrieval operation. This goal can be achieved by carrying out a retrieval operation in the following four phases: Assessment, Planning, Implementation, and Review. Included in these phases are exploring alternate retrieval scenarios with to each individual's role, and estimating the time and anticipated dose to implement the actions for each scenario. The scenario selected should be the one where doses are ALARA, and personnel exposure to other physical hazards is minimized.
This abstract was presented at the 34th Annual Midyear Meeting, "Radiation Safety and ALARA Considerations for the 21st Century", ALARA Session, 2/4/2001 - 2/7/2001, held in Anaheim, CA.