Yankee slows for routine maintenance
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By Susan Smallheer STAFF WRITER - Published: November 19, 2009
BRATTLEBORO – The Vermont Yankee nuclear reactor was still at reduced power late Wednesday for what Entergy Nuclear officials said was routine maintenance and testing, timed to coincide with work on the region's transmission network by other firms.
Entergy Nuclear spokesman Larry Smith said Wednesday that transmission-line work by Vermont Electric Power Co. had delayed the plant going back to full power.
On Tuesday, Smith had said he expected the reactor to be back to full power by Wednesday, but according to the regular reactor status report posted daily by the Nuclear Regulatory Commission, Yankee was at 67 percent power Wednesday morning. Smith said later Wednesday the reactor was at 77 percent power.
On Monday, the plant had been reduced to 54 percent power.
Vermont Yankee provides about one-third of all the electricity used in Vermont by customers of Central Vermont Public Service Corp. and Green Mountain Power Co. That represents about half of the plant's power production, with the balance sold by Entergy Nuclear out of state.
Smith said that the company was adjusting the control rods inside the reactor to maximize power production, something the company does quarterly.
"Rod pattern exchange involves change the position of control rods, not fuel rods. The repositioning of the control rods … helps to better redistribute power production throughout the core, based on where the plant is in the fuel cycle," said NRC spokesman Neil Sheehan in an e-mail.
The control rods are inserted between fuel rod assemblies to absorb neutrons, which helps to moderate power production.
In addition, Sheehan said, Entergy is doing some testing of its main steam isolation valve and turbine valve testing, both which much take place at 60 percent power.
The line work by VELCO can only be done at about 60 percent power, he said.
Sheehan also said that some other maintenance that can only be done while the radiation dose is lower has also been completed.
Smith said both VELCO and ISO-New England wanted to do some work on the lines transmitting Yankee's 680 megawatts of power, and he said on Tuesday that the work would be completed by Wednesday.
Smith said by late Wednesday afternoon, the reactor was at 77 percent power. He said the delay was due to VELCO. He said he couldn't say when the plant would be back at full power.
He said the reduction in power had been scheduled in advance with ISO-New England, and he said repositioning the control rods were necessary the closer the plant got to refueling and its regular refueling outage. That outage is slated for April 2010.
susan.smallheer@rutlandherald.com
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