The following information was received from the State of
California via email:
UCLA notified RHB on December 5, 2011 that they discovered a single missing Thorium-229 source. Its activity is approximately 4.73 microcuries and is contained in a flame sealed ampoule. The responsible researcher claims that they transferred the source to EH&S for storage, but a search of EH&S records showed it was returned to the researcher in June 2011. A continued search of the Principal Investigator's lab and EH&S storage locations is ongoing.
10 CFR 20 Appendix C for Th-229 = 0.001 uCi, and 10CFR 20. 2201(a) requires reporting losses that exceed 1000 times the Appendix C level. Activity of > 1 microcuries is a reportable quantity.
No serial number was reported to RHB [Radiologic Health Branch]. Potential exposure to individuals is expected to be extremely low.
This investigation is on-going.
CA 5010 Number: 120511
THIS MATERIAL EVENT CONTAINS A "LESS THAN CAT 3" LEVEL OF RADIOACTIVE MATERIAL
Sources that are "Less than IAEA Category 3 sources," are either sources that are very unlikely to cause permanent injury to individuals or contain a very small amount of radioactive material that would not cause any permanent injury. Some of these sources, such as moisture density gauges or thickness gauges that are Category 4, the amount of unshielded radioactive material, if not safely managed or securely protected, could possibly - although it is unlikely - temporarily injure someone who handled it or were otherwise in contact with it, or who were close to it for a period of many weeks. For additional information go to http://www-pub.iaea.org/MTCD/publications/PDF/Pub1227_web.pdf
This source is not amongst those sources or devices identified by the
IAEA Code of Conduct for the Safety & Security of Radioactive Sources to be of concern from a radiological standpoint. Therefore is it being categorized as a less than Category 3 source.