SAN FRANCISCO - Pacific Gas and Electric Company has updated the Nuclear Regulatory Commission (NRC) on the status of the investigation into the location of segments of a used nuclear fuel rod at its Humboldt Bay Power Plant near Eureka in northern California. Plant personnel have completed the physical search of the most likely locations and all easily accessible spaces in the plant's used fuel storage pool, but the segments have not yet been found. Further, the review of plant records, nuclear material shipping records, and interviews with former plant personnel have not definitively identified the location of the fuel segments.

Based on the results of the investigation to-date, and the administrative, radiological, and security barriers in place at the plant, PG&E continues to believe that the segments are either safely stored in the used fuel pool, or were shipped to a facility licensed to accept radioactive material, no more recently than 1986.

The company initially reported to the NRC on June 29, 2004, that there was conflicting documentation regarding the used fuel segments. The plant's records indicate that the segments were either stored in the used fuel pool in 1968, or had been shipped offsite in 1969. Since notifying the NRC, plant personnel began an investigation consisting of: 1) a meticulous review of the records associated with the used fuel pool as well as with shipments of used fuel and other significant radioactive materials; 2) interviews of former plant personnel and contractors; and 3) a physical search of the pool. All three efforts are continuing.

Possible Locations

Because the fuel segments have not yet been found in the used fuel pool, three possible scenarios exist. The highest probability is that the fuel segments are in an area of the pool that is not readily accessible, and will be located during a more detailed search of these locations. The second highest probability is that the fuel segments were shipped offsite to one of three appropriately controlled and restricted facilities licensed for analysis, storage or reprocessing of spent nuclear fuel. The third and most remote possibility is that the fuel segments were unintentionally included in a shipment to one of three licensed, monitored, and restricted, radioactive waste disposal facilities.

"Based on all the information we have collected so far, we believe the only possible locations for these fuel segments are the used fuel storage pool at Humboldt Bay Power Plant, or one of the few licensed, restricted and monitored facilities to which we previously shipped radioactive materials two to three decades ago," said Greg Rueger, senior vice president for generation and Chief Nuclear Officer for the utility.

The three facilities to which the plant shipped used fuel (between 1968, when this fuel was removed from its assembly, and 1974, when the last shipment of used fuel occurred) are:

• Nuclear Fuel Services Inc in West Valley, New York - Plant records show the fuel assembly which originally housed the rod in question was shipped to West Valley for reprocessing in 1969 with no mention of it missing a fuel rod. It is possible that the segments were reinserted into the canister containing the fuel assembly, prior to its shipment to West Valley; if so, the segments were likely reprocessed. Unfortunately, West Valley has informed PG&E that all shipping receipt records from that time period have been destroyed, so it will be difficult if not impossible to investigate this possibility further.
• GE's Vallecitos Nuclear Center in Livermore, California - During the 1960s and 1970s, fuel rods were periodically removed from fuel assemblies, and sent to GE to gather data used to improve fuel design. Plant records indicate that 66 fuel rods were shipped to GE in 11 shipments; it is possible, although not likely, that the fuel segments were included in one of those shipments. PG&E has asked GE to review their records to determine if they received other fuel rod segments, and report back to the plant as soon as that review is completed.
• Battelle Memorial Institute in Columbus, Ohio - Plant records indicate that PG&E cancelled the original 1968 shipment of fuel segments to the Battelle lab, and their records from the period support this. Based on this information, it appears very unlikely that the segments were sent to Batelle.

There is no evidence that the used fuel segments were shipped to a radioactive waste disposal site, however, in an effort to exhaust all scenarios, plant staff are investigating this as a remote possibility. Between 1968 and 1986 (when the last shipment of any material from the pool occurred), the Humboldt plant shipped radioactive material to such waste facilities in Beatty Nevada, Richland Washington, and Barnwell South Carolina. If the fuel segments were inadvertently included in a shipment to one of these locations, they would have been placed in a licensed shipping container and properly transported. Such a shipment would not pose any health or safety risk for facility workers or the public. These radioactive waste disposal sites are licensed, restricted, and monitored, and while not authorized to receive used fuel, they are permitted to receive other types of nuclear waste of even higher radiation levels than the fuel segments in question.

While it appeared that the remnants of the fuel rod from which the three segments were cut had been located in the used fuel pool in July, forensic analysis of those fuel fragments performed in early August indicated that they were not likely to have come from the cut fuel rod. Based on the discovery and review of the procedures used when the fuel was cut, it is now believed that when the cut pieces were removed, the remnants were left in place in the fuel assembly, where they remained when the entire assembly was shipped offsite for reprocessing in 1969.

Low Potential for Theft or Diversion

No evidence has been uncovered to support the possibility of theft or diversion of the three fuel segments. Since plant start-up, HBPP has been equipped with a system of radiation monitors for the refueling building (where the used fuel pool is located) with alarms designed to alert plant personnel of the movement of highly radioactive material, including used fuel. Due to the high radioactivity of this used fuel, to be handled safely the segments would have to be encased in a heavy, shielded container that would have to be moved with special handling equipment designed for this purpose, precluding an abrupt loss. This could not have occurred casually without plant staff or security personnel observing the movement.

Next Steps

Although comprehensive, the physical search of the pool has not ruled out the possibility that the fuel segments are in the used fuel pool. As a result, PG&E is continuing in its efforts to search other, less accessible locations in the pool, as expeditiously as it is practical and safe to do. However, it is possible that a complete search may not be concluded until the 390 used fuel assemblies, along with other components, are removed from the pool, as part of the plant decommissioning process currently set for 2009.

Efforts also continue to research historical documentation regarding shipments of radioactive material for information that could lead to a conclusive resolution of the issue. In addition, interviews of personnel who worked at the plant in the past are continuing. Research is also ongoing into the records of the licensed facilities listed above as possible locations for the fuel segments.

PG&E will continue to communicate fully with the Nuclear Regulatory Commission and other interested regulatory and governmental agencies, and thoroughly document the investigation. The utility will also continue to provide regular updates to the public, as appropriate and as developments occur. This investigation is expected to take at least an additional three months.