The following information was obtained from the licensee via facsimile (licensee text in quotes):
This notification to the NRC Operations Center is in accordance with 10 CFR 20.2201(a)(ii) regarding the incident described below:
On 3/10/05, we determined that 245 [microCurie] (9.1 MBq) of [Gd-153] (0.5N HCI) in a source vial was missing. The original activity was 1 [milliCurie] (37 MBq) on 4/12/2004, and the missing quantity, corrected for radioactive decay, represented the remaining activity after several labeling experiments.
Following this discovery, the Authorized User interviewed all researchers who had access to her laboratory. None recalled disposing of the vial. In addition, a health physicist contacted a number of the researchers and performed an independent survey of this and adjacent laboratories with a photon-sensitive survey meter. The original lead pig was found in a box where other lead pigs were stored awaiting disposal. However, the source vial was not in the lead pig. In addition to searching the laboratory areas, we checked the records of both radioactive waste pick ups and other monitored waste from the building in which this laboratory is located. There was no indication of [Gd-153] in any of the records or surveys.
At this time, the disposition of the material is unknown. Considering that the exposure rate for an unshielded point source of 245 [microCuries] of [Gd-153] is only 0.04 mR/hr, the missing material would not represent a significant external exposure risk. The approximately 69 nanograms of material missing would not represent a significant toxic hazard either.
Corrective actions have been implemented by suspending the Authorized User's ability to order more radioactive material. With her pending departure from NIH, we do not feel any further actions will be warranted in this situation.