A British nuclear reprocessing plant cannot account for nearly 66 pounds of plutonium, but authorities believe it's an accounting issue rather than a loss of potential bomb-making material, the U.K. Atomic Energy Authority (search) said Thursday.

The amount of material listed as missing at the Sellafield (search) plant in northwestern England was "within international standards of expected measurement accuracies for closing a nuclear material balance at the type of facility concerned," the authority said.

"There is no evidence to suggest that any of the apparent losses reported were real losses of nuclear material," the authority added.

In 2003, the processing plant reported it could not account for 42 pounds of plutonium (search). The plant said that was consistent with figures published since the 1970s.

Plutonium accounts for 1 percent of the nuclear material handled at Sellafield; the rest is uranium.