Waterford - An Oct. 29 inspection of Millstone Power Station's preparations before Superstorm Sandy revealed there was no gauge in place to determine when floodwaters reached a critical level, the Nuclear Regulatory Commission announced Wednesday.
As a result, Millstone was issued a "green" finding - the lowest of four levels of safety significance - and ordered to take corrective action. It was one of two "green" findings in the latest NRC inspection report, bringing to four the total number of "green" findings at the plant in the last year.
The other finding involved a probe that measures the level of nuclear fission taking place in the reactor as it is in operation, NRC spokesman Neil Sheehan said. The probe was out of service for 31 days, a violation of the company's license requirements that an individual probe be out of service no more than seven days.
Ken Holt, spokesman for Millstone owner Dominion, said repairs have been made and the probe is operating properly. Staff were also retrained about proper procedures, he said.
The violation involving the flood gauge has also been corrected, he said. The correction involved simply painting a "very visible" line on the seawater intake structures at the 19-foot mark. The company's license states that when floodwaters reach 19 feet above mean high tide, the Unit 2 reactor is considered to be in an "unusual event" and must begin taking emergency actions. The level is 19.7 feet for Unit 3.
During Storm Sandy, the highest storm surge at the plant was 8 feet above the normal high tide level.
"We discovered that we didn't have a physical indication of what level the floodwaters were at," Holt said. "It was never considered before."
Sheehan said that being able to measure flood heights at nuclear power plants is becoming increasingly important with the expected increase in frequency of intense storms.