09. 2011年10月05日 07:39:01: rjsYJEDWic
Reactors could fail during an earthquake, maker says
By staff and wire reports
Friday, September 30, 2011
Read more: Reactors could fail during an earthquake, maker says - Pittsburgh Tribune-Review http://www.pittsburghlive.com/x/pittsburghtrib/business/s_759421.html#ixzz1Zr5wAeaY
GE Hitachi Nuclear Energy said 35 reactors it built for utilities from New York to Washington may not shut down properly during an earthquake. The likelihood of failure is "low," the company said in an advisory to customers on additional actions to take.
GE Hitachi, which made First Energy Corp.'s Perry, Ohio, plant on Lake Erie, about 120 miles northwest of Pittsburgh, and Exelon Corp.'s Oyster Creek plant in New Jersey, is recommending testing to determine what level of friction would prevent control rods from fully inserting into the reactor core during an earthquake, according to filings with the Nuclear Regulatory Commission.
"There is no discussion of a recall of any control rods at this point," Neil Sheehan, a Philadelphia-based spokesman for the commission, said in an e-mail. "The focus is on testing as evaluations continue on whether any modifications are necessary."
The issue is contained in a series of reports to the federal agency dating to December 2010, Sheehan said. The affected plants don't include Dominion Resources Inc.'s North Anna in Virginia, which remains shut because of a 5.8 magnitude earthquake centered 11 miles away on Aug. 23.
The issue is a "low probability event" that became known to the company several months before the March earthquake and radiation leaks at the Tokyo Electric Power Co.'s Fukushima Daiichi plant in Japan, Michael Tetuan, a spokesman for GE Hitachi in Wilmington, N.C., said in an e-mail.
"We are only aware of a small percentage of plants that have exhibited signs of measureable control-blade-to-channel friction and on a relatively few number of control blades," he said.
FirstEnergy spokeswoman Jennifer Young said the GE Hitachi recommendations do not apply to the Akron, Ohio-based utility's Perry plant because its boiling-water reactor is a newer vintage in which larger size and higher pressures "preclude it from having the same issue." The Perry reactor's control rods would be able to stop nuclear fission in the event of an earthquake, she said.
"If GE Hitachi issues additional guidance, we'll work closely with them and the NRC," said Young.
GE Hitachi's testing program is adequate because it forces owners to replace defective control rods when reactors are shut down for refueling instead of continuing the tests, according to David Lochbaum, director of the Nuclear Safety Project at the Union of Concerned Scientists.
"Lots of things have to line up to produce the bad outcome," he said in an e-mail. "Not all GE control rods have this problem, so owners are replacing them sooner."
The shutdown "capability is expected to be affected due to the added seismic loads at low reactor pressures" in the boiling-water-reactor plants, GE Hitachi said in the filing to the NRC. More testing is needed to determine how much friction is produced by "seismic loads," the filing showed.
Sheehan said the commission is evaluating whether GE Hitachi's emphasis on testing is appropriate and if additional steps are required to ensure plant safety.
"There are still other changes to come in response to the issue," he said. "I don't know off-hand what level of seismic activity could pose a problem."
On a wider level, the NRC plans to issue a letter to all 104 U.S. plants by year's end requesting a response to the agency's new seismic risk modeling and data.
Other plants that may be affected by the control rod issue include Exelon's Clinton, Dresden, LaSalle, and Quad Cities plants in Illinois as well as Limerick and Peach Bottom in Eastern Pennsylvania.
Also on the list are New Orleans-based Entergy Corp.'s FitzPatrick in New York, Vermont Yankee in Vermont, Pilgrim in Massachusetts, Grand Gulf in Mississippi, and the Tennessee Valley Authority's Browns Ferry in Alabama and River Bend in Louisiana.
Elsewhere are Public Service Enterprise Group Inc.'s Hope Creek in New Jersey, Constellation Nuclear Energy Group LLC's Nine Mile Point in New York, and DTE Energy's Fermi 2 in Michigan.
The South includes Progress Energy Inc.'s Brunswick in North Carolina and Southern Co.'s Hatch in Georgia,
Further west are NextEra Energy Inc.'s Duane Arnold in Iowa, Nebraska Public Power District's Cooper in Nebraska, Xcel Energy Inc.'s Monticello in Minnesota and Energy Northwest's Columbia in Washington. Some plants have more than one reactor.