By Kathleen Davis, Associate Editor
The U.S. Nuclear Regulatory Commission (NRC) has an idea what happened to two missing spent fuel rods from Millstone Unit 1.
The NRC sent in a special inspection team, which included a licensing project manager and a material control and accounting inspector, last fall to evaluate the investigation conducted by the plant’s previous owner, Northeast Utilities (NU). NU first reported the missing rods to the NRC in December 2000. Company records indicated the rods were last verified to be in the spent fuel pool in 1980. However, there was no documentation of their presence since that date.
The results of the NU investigation were turned over to the NRC last fall by Dominion Nuclear, the current owner of Millstone Units 1, 2 and 3 (Unit 1 is shut down, but 2 and 3 remain in operation.). NU stated that the “exact location” of the rods could not be found, but that it was probably one of four sites: a low-level radioactive waste disposal site in Barnwell, S.C.: another in Hanford, Wash.; the spent fuel pool at a General Electric Co. facility in Vallecitos, Calif.; or still within the Millstone 1 spent fuel pool.
According to NU, there is a low likelihood that the fuel rods are in the spent fuel pool at Millstone 1, as the physical searches were thorough and few inaccessible areas remain; the NRC team agreed with this conclusion. Both teams also considered the Vallecitos Center unlikely, as there was no evidence the rods were shipped there. In the end, both NU’s investigation and that of the NRC led to Barnwell or Hanford as possible final resting places for the missing rods, as there were a number of shipments to both sites which could have contained them.
The teams also agreed on possible root causes of the error: that procedures at the time were not always followed and did not address individual rods, that there was too much reliance on individual performance and that they failed to segregate fuel from non-fuel items, which invited confusion.
The NRC did list a number of potential violations from the incident: failure to adequately account for special nuclear material, failure to complete/submit SNM transfer reports, failure to report missing radioactive material in a timely manner, failure to adequately characterize radwaste for shipment and failure to provide adequate physical protection of irradiated reactor fuel in transit. The agency stated, however, that the rods do not pose any risk of being used for nuclear weapons, as their uranium and plutonium content would be quite low.