Waterford — Inadequate documentation of a design weakness in valves that shut off water flow during an emergency at the Unit 3 nuclear reactor at the Millstone Power Station has resulted in a finding of "very low safety significance" by Nuclear Regulatory Commission inspectors.

The finding, coded "green" — the lowest of four levels of safety significance in the NRC's ranking system — was uncovered during a regularly scheduled quarterly NRC inspection of Units 2 and 3 this spring. The NRC announced the finding last week.

Millstone spokesman Ken Holt said today that Millstone staff previously had determined that despite the design weakness, the valves would still work in an emergency. The NRC agreed, but found fault with Millstone's documentation of the weakness and the thoroughness of its assessment that they would still function.

Holt said the valves are scheduled to be replaced when Unit 3 is shut down for refueling next spring.