NRC says VY temps within limits
BRATTLEBORO -- Anti-nuclear activists were denied a petition by the Nuclear Reactor Commission's Petition Review Board Friday.
In a June 7 letter addressed to William Borchardt, executive director for operations at the U.S. Nuclear Regulatory Commission, consultants for the New England Coalition, Mark Leyse and Ray Shadis, requested that the commission lower the limit of the peak fuel cladding temperature at the Vermont Yankee nuclear power plant in Vernon.
Zirconium alloys used in Vermont Yankee's cladding, which are also commonly used at other nuclear plants across the country, are designed to contain the plant's reactor fuel, consisting of uranium dioxide ceramic pellets, Shadis said.
"Everything about nuclear safety has to do with containing those pellets," he said. "The cladding has to retain its integrity to ensure fission products, like strontium-90, never get into the environment."
The fuel cladding temperature set by the NRC, 2,200 degrees, is far too high to ensure the public safety, according to Leyse and Shadis.
Shadis told the NRC that lowering the temperatures could help ensure an accident similar to the partial core meltdown at Three Mile Island in March 1979, or even worse, won't occur again.
Experiments and studies conducted in Germany have shown that rapid oxidation, an exothermic reaction where the reaction is self sustaining and generates more heat as the process continues, can occur as low as 1,832 degrees.
"Once rapid oxidation begins there's nothing you can do about it," Leyse said. In the experiments, it took only 60 seconds for the temperatures to reach 3,300 degrees because of the runaway oxidation."
Trying to combat it with water would only make it worse, Leyse added, because the process would just drain the oxygen from the water, rising in temperature.
Based upon the nuclear plant's analysis, Vermont Yankee is well within the NRC accepted criteria at 2,060 degrees, Entergy spokesman Larry Smith said.
The NRC agreed, which is why the petition was dismissed.
Leyse said the NRC constantly states its purpose is public safety and that it is overly conservative in those measures.
"To be truly conservative, the temperature limits should be lowered to well below the 1,832," he said.
He estimates that the temperature should be below 1,700 to avoid rapid oxidation.
Leyse said that although the petition was denied, it was passed along to the NRC's rule making branch for further study and analysis and could be considered for the regulations that govern all the U.S. nuclear plants.
Josh Stilts can be reached at email@example.com, or 802-254-2311 ext. 273.
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