No. I-08-064 

Contact: Diane Screnci, 610/337-5330 

 Neil Sheehan, 610/337-5331 

December 15, 2008

NRC BEGINS SPECIAL INSPECTION AT MILLSTONE 3 NUCLEAR POWER PLANT 

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 

NRC NEWS

U.S. NUCLEAR REGULATORY COMMISSION

Office of Public Affairs, Region I 

475 Allendale Road, King of Prussia, Pa. 19406 

E-mail: opa1@nrc.gov 

Site: http://www.nrc.gov
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.” 

The team is expected to be on-site at least through the end of the week. An inspection 

report detailing the team’s findings will be issued 45 days after the end of the inspection. 

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