NRC BEGINS SPECIAL INSPECTION AT MILLSTONE 3 NUCLEAR POWER PLANT
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The Nuclear Regulatory Commission has initiated a Special Inspection at the Millstone 3 nuclear power plant in response to the recent discovery of a volume of gas trapped in piping for a reactor safety system. The team inspection got under way today.

There are no immediate safety concerns because the issue was identified when the Waterford, Conn., plant was shut down in October for a refueling and maintenance outage and the system was not required to be operable. Dominion Nuclear Connecticut, Inc., the plant’s owner, subsequently installed a valve during the outage and vented the gas, thereby fixing the problem prior to the plant’s restart. The condition was not found at the other operating reactor at the site, Millstone 2.

The gas was found in a section of 24-inch-diameter suction piping between the plant’s refueling water storage tank and its emergency core cooling system pumps. The tank holds hundreds of thousands of gallons of cooling water. During certain accident scenarios, cooling water would be drawn from the tank and sent to the pumps, which in turn would deliver the water to the reactor vessel to keep the nuclear fuel inside covered and cooled. The concern over the gas is that it could be transferred to the pumps during an accident and impact their operability.

“We want to ensure that Dominion is being as thorough as possible in evaluating how this condition developed and in taking steps to prevent a recurrence,” NRC Region I Administrator Samuel J. Collins said. “The inspectors will be tasked with gathering all of the facts necessary for us to gain a full understanding of this matter.”

Specifically, the team of three full-time inspectors will review the company’s determination of the cause of the gas “voiding” condition, including any design deficiencies and/or operating practices that allowed it to exist. In addition, the inspectors will independently verify Dominion’s calculations regarding the condition and its effect on the ability of the
emergency core cooling system pumps to perform their safety function if needed. The inspection was scheduled to begin now in order to allow the company to complete its analysis of the impact of the gas.

The gas was found in the piping as a result of inspections carried out by the company in response to NRC Generic Letter 2008-01, “Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal and Containment Spray Systems.”

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Tuesday, December 16, 2008