12 février 2014
Le tremblement de terre du 23 août 2011 (de magnitude 5.8) a décalé les fûts de déchets radioactifs pesant 115 tonnes. Les distances de sécurité entre fûts sont estimées à 14 pieds (4 m 27), et les fûts les plus proches restent à 15 pieds et 2 1/4 de pouce (4,62 m) des fûts voisins : le choix a été fait de ne pas irradier le personnel pour remettre les fûts à leur place...
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Earthquake-shifted nuclear storage casks at North Anna can stay where they are
Quake shifted Dominion storage units, but NRC is OK with current configuration
Posted : Wednesday, February 12, 2014 12:00 am | Updated : 9:41 pm, Wed Feb 12, 2014.
BY PETER BACQUÉ Richmond Times-Dispatch
The large nuclear fuel storage casks at the North Anna Power Station that shifted during the 2011 central Virginia earthquake can stay where they are.
The Nuclear Regulatory Commission staff does not currently plan to require Dominion Virginia Power to move the casks back, according to Jennifer Davis, licensing branch senior storage project manager in the NRC’s Division of Spent Fuel Storage and Transportation.
In their current positions, the casks meet NRC spacing requirements, Davis said. The Richmond-based utility’s analysis indicates that the casks are in a safe configuration.
“The casks moved slightly, but showed no other indications of adverse effects, and no damage,” Dominion Virginia Power told the NRC in a presentation Jan. 28. “Dominion concludes that leaving the casks in their current position makes sense.”
>From center to center, the casks are supposed to be spaced “a nominal 16 feet apart,” according to NRC technical specifications.
The casks’ spacing now varies from 15 feet 2¼ inches to 16 feet 11¼ inches, the company said. “We determined that 14 feet would be the minimal distance,” company spokesman Rick Zuercher said.
“The fuel has been in the casks sitting there cooling for such a long period of time that it’s safe where it is,” Zuercher said. “It’s not impacting anything.”
The earthquake caused 25 of 27 spent-fuel storage casks — each weighing 115 tons — to move on their concrete pad at the company’s nuclear power plant in Louisa County. The most any one cask slid was 4½ inches, the company said.
None of the 16-foot tall metal cylinders was damaged, and no radiation was released, Dominion Virginia Power said.
Moving the casks back would be a big operation, NRC and company officials said, and would likely involve some exposure of workers to radiation.
“It makes no sense to (reposition the casks) and expose the workers to an additional radiation dose for no safety purpose,” Zuercher said.
In the next several months, Dominion Virginia Power will submit a site-specific license amendment request to NRC proposing a clarification of the technical specifications for the cask spacing, the NRC said, and the agency’s headquarters staff will review the company’s proposal.
Dominion Virginia Power is the state’s largest electric company, with nearly 2.4 million customers. Its nuclear power units at North Anna and Surry, located in Surry County, produce about 40 percent of the electricity used by its customers.
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