NRC team to help probe VY leak
The break might be related to upgrades made after a cell in the west tower collapsed last August, said a spokesman at the nuclear power plant in Vernon.
"It appears that the broken or degraded bracket was not due to decay but appears to be related to stresses in the design of the new interface between the bracket and the previously replaced column in that area," said Rob Williams.
Cracks were also found in supporting members in two of the west cooling tower cells, one of which collapsed last year, stated the NRC.
How repairs to the cooling towers might have led to this latest problem is of concern to the NRC, which announced in the press release it was sending a team of inspectors to Vernon to assist in the investigation.
The inspectors will begin work at the site today.
"Our inspectors will be looking at the changes they made following the cooling tower collapse," said NRC spokeswoman Diane Screnci. "They will also be following Entergy's root cause analysis to insure they are being thorough and comprehensive and are getting to the bottom (of the failure)."
In addition to the inspection team, NRC Chairman Dale Klein sent the NRC's executive director for operations to the plant to consult with the inspectors and plant officials today and report back his findings.
Williams said the NRC's team of inspectors will get everything they need to conduct their investigation.
"We welcome their oversight and input," he said.
The reason for last August's cooling cell collapse was due to a rotten wooden support, which engineers attributed to a failure in the plant's inspection and maintenance protocols related to the towers.
After the August collapse, Entergy Nuclear Vermont Yankee, which owns the plant, promised the Nuclear Regulatory Commission and Vermont's Department of Public Service it would replace some of the wooden members with fiberglass supports and would also update its inspection and maintenance program.
Late Friday afternoon, a spokesman for Vermont's Department of Public Service said the leak called into question Yankee's system maintenance program.
"This is a huge disappointment," said Stephen Wark. "We are concerned that Vermont Yankee is dealing with a problem that was reported to have been resolved."
Both east and west towers were shut down Friday after technicians discovered "broken or degraded" pipe brackets in the saddles supporting the feeder pipes in each tower, said Williams. On Saturday and Sunday, plant maintenance personnel were busy repairing the brackets in five saddles in the west tower, he said.
Yankee technicians hope to have the west tower up and running within the next few days, he said. As far as the east tower is concerned, said Williams, "There is no timetable for repairs," but technicians hope to have it repaired in the next several days.
Power output at Yankee was reduced to less than 50 percent of capacity Friday after the leak was discovered. On Saturday, power had again been reduced, this time down to 25 percent, because of low river flows, said Williams. By Sunday, the plant had powered back up to 40 percent, he said.
Power output fluctuates in situations such as this, he said, "To insure we keep within the limits of the river temperature discharge permit."
Cooling towers are used to remove heat from water used to cool the steam that powers the plant's turbine so that the cooling water can be discharged to a river or recirculated and reused.
The two cooling towers at Vermont Yankee are considered mechanical draft systems, each made up of 11 cooling cells with feeder pipes that run along the top of each tower, spraying water downward into the cells. Fans in each cell pull air across the falling water which drops over slats which break the water into a fine spray.
During colder months and periods when fish are not spawning or migrating, the discharge goes into the river and the use of the cooling towers is not required. During the summer months, the cooling towers are needed to reduce cooling water temperatures before the water is either returned to the river or recirculated in the plant's cooling system.
Entergy Nuclear Vermont Yankee has applied to the NRC to extend its operating license from 2012 to 2032. The NRC has stated it has found no safety or environmental reasons for not issuing the extension. Vermont's Public Service Board and the legislature both have to sign off on the extension as well. Recently, Gov. James Douglas signed a law requiring a state inspection of the plant prior to continued operation.
Bob Audette can be reached at email@example.com or 802-254-2311, ext. 273.
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