By all accounts, the case of the missing fuel rods at Pacific Gas & Electric?s shuttered Humboldt Bay nuclear power plant is most likely due to a 35-year-old clerical error rather than sabotage or theft. But locating the rods with robotic gear in a crowded spent-fuel pool is an extraordinarily difficult task that may become quite expensive before it is completed. PG&E workers discovered June 23 that three pieces of a used nuclear fuel rod, about four pounds in all, were not shipped as reported to a Midwestern lab in the late 1960s. The discrepancy was discovered as part of an inventory that PG&E began last year to satisfy a Nuclear Regulatory Commission mandate and to move ahead with its own plans to transfer spent fuel to dry cask storage. ?It?s a slow and meticulous process, because you are working underwater,? said PG&E spokesperson Jeff Lewis. Lewis said the company has brought in staff from its Diablo Canyon nuclear plant to assist the Humboldt crew. ?There?s a certain amount of sediment in the bottom of the pool that can make it difficult to see.? The 65 MW plant was shut down in 1976 after a dozen years of operation. According to Lewis, there?s virtually no danger that the radioactive material was transported off site. ?It would have to have been put inside a steel and lead container that would weigh up to a ton,? he said. Nuclear Regulatory Commission spokesperson Victor Dricks agreed. ?Due to the radiological controls and security measures...it?s highly unlikely the material is in an uncontrolled situation,? he said. Dricks added that the spent fuel would be unsuitable for weapons. ?We?re talking about a very small amount of material, far less than would be needed for a nuclear weapon,? he maintained. It is also unlikely that the material could be made into a so-called dirty bomb. ?The rods are in a nondispersible form...Processing the material into a more dispersible form, pulverizing it, would require considerable effort and be extremely hazardous,? said Dricks. Michael Welch, a member of the activist group Redwood Alliance and of PG&E?s Community Advisory Board, took a similar view of the case. ?Anytime that there?s missing spent fuel, it?s a concern, [but] it seems like the most likely scenario is that the fuel is in the spent-fuel pool,? he said. Reports of missing spent fuel at nuclear plants are very rare. According to Dricks and a search of the NRC Web site, two such incidents have occurred since 2000. At Millstone Station in Westford, Connecticut, two fuel rods that showed up missing in a 2000 inventory were never found. NRC agreed with the plant?s original owner, Northeast Nuclear Energy Company, that the material had probably been shipped to a radioactive waste facility before 1992. But even though there was ?no realistic threat? to health and safety, nuclear regulators called the error ?unprecedented and a very significant violation? and fined the plant?s purchaser, Dominion Nuclear Connecticut, Inc., $288,000. In July, engineers at the Vermont Yankee nuclear power plant found two spent-fuel rods that were determined to be missing in April. Employees and contractors spent 9,000 to 10,000 hours during the three-month search, according to the <i>Brattleboro Reformer<\/i>.