3rd leak plagues Yankee
"The leak was not related to any structural issues as had been the cause of previous events in the cooling tower," stated Rob Williams, in an e-mail to the media.
When the leak in the east tower's distribution pipe was discovered Tuesday night, it was taken out of service and the plant's power generation ramped down to 57 percent of capacity.
The west tower re-mained in service, saidWilliams, Vermont Yankee spokesman. Repairs should be done soon, he said, and the plant would then return to full power production.
"It appears that the leak of about 60 gallons per minute is related to the packing in an expansion joint and not related to structural issues as had been the cause of previous river water leaks in the cooling tower," stated Williams, in an e-mail to the media. "While packing leaks are not uncommon, plant management took the conservative action to reduce power and remove the cooling tower from service to allow an inspection of adjacent pipe joint packing."
The packing material in the joints is called "Oakum" and is used for caulking in wooden boats and for packing pipe joints. Oakum is usually made of hemp or jute fiber treated with creosote, tar or asphalt.
The news coming from Vermont Yankee raised concerns in the state's Department of Public Service.
"Information today regarding Vermont Yankee's leak in the cooling tower comes as a great disappointment and is unacceptable," said Stephen Wark, spokesman for DPS. "While we recognize this failure is of a non-nuclear component and public safety was not at risk, the down rate nonetheless has a very real impact on consumers."
The cooling towers have been a focus of much attention since August 2007, when one of 11 cooling fan cells in the west cooling tower collapsed, spilling hundreds of thousands of gallons of river water onto the ground.
The failure was attributed to rotten wooden support columns in the cooling tower and was blamed on shortcomings in Yankee's cooling tower inspection and maintenance programs
Some wooden columns in both the east and west towers were replaced with fiberglass support beams, but this past July, a break in a support member holding the supply pipe in one of the cooling towers caused leakage. The break was blamed on the faulty design of the connection between the new fiberglass columns and the brackets supporting the header pipe.
In addition to the broken support in the east tower, cracks were discovered in pipe supports in the west tower, including in the cooling cell that collapsed last August.
The NRC recently sent a team of four inspectors to review the problems with the cooling towers and Yankee's response to those problems. When that report will be released to the public is not known yet, said Neil Sheehan, spokesman for the NRC.
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 the ability to deny continued operation of the plant past 2012.
The state is conducting an audit of the plant to inform its decision.
"Those results and indeed the report on this incident will give us a better understanding of the root cause of the cooling tower failures," said Wark.
On Wednesday afternoon, plant technicians began the replacement of the packing material in the expansion joint, said Williams. During that work, employees discovered three vertical support columns that required replacement ahead of a maintenance schedule that was established after the August 2007 collapse.
"Three vertical support columns were found to be degraded to the extent that replacement is warranted now, concurrent with the pipe joint repacking work."
Bob Audette can be reached at email@example.com or 802-254-2311, ext. 273.
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