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Pilgrim addresses deteriorating protective panels

  • Sep 14, 2017
Cape Cod Times

Sept. 14--PLYMOUTH -- Operators of Pilgrim Nuclear Power Station have used geometry to ensure a fire and radioactive release won't occur in the plant's spent fuel pool, despite ongoing deterioration of hundreds of neutron-absorbing panels needed to prevent a nuclear reaction.

The solution was simply to change the configuration of the pool, moving the spent fuel rods away from storage racks where the panels were deteriorating, particularly the rods that were most recently in the reactor since they would be the hottest.

About 1,600 of the nearly 3,000 spent fuel assemblies were shifted, according to Pilgrim spokesman Patrick O'Brien.

The shift took place during the summer and has been assessed by inspectors with the U.S. Nuclear Regulatory Commission.

Entergy Corp., Pilgrim's owner and operator, had evaluated the condition of the Boraflex panels in the fuel pool late last year and estimated 885 were in danger of deteriorating. The panels contain neutron-absorbing boron carbide to stop fission from occurring and are attached to pool racks holding bundles of radioactive fuel.

Heat and radiation have eaten away at the protective compound.

In the spent fuel pool environment, the minimum critical volume necessary to sustain a nuclear chain reaction may be as small as four fuel assemblies, NRC spokesman Neil Sheehan said.

Pilgrim's pool, originally designed to hold 880 spent fuel assemblies, currently holds 2,990 on racks under about 40 feet of water.

Early racks used to hold spent nuclear fuel assemblies were not clad with boron carbide because there was plenty of space between them. Once it became clear that nuclear waste was going to remain on reactor sites indefinitely rather than shipped to a federal repository, the pools were equipped with boron-clad racks so rods could be stored in a much tighter configuration than originally planned without a nuclear reaction occurring.

"There's a long history here," Mary Lampert, director of Pilgrim Watch, said about the deterioration problem with the Boraflex panels, which has been known since the 1980s.

"NRC has kicked the can down the road, and kicked the can down the road, and kicked the can down the road," Lampert said. "And now, they are again allowing industry the cheap way out to deal with potential spent fuel pool criticality resulting from degraded boraflex panels."

"The real fix" would be to replace the deteriorated storage racks, Lampert said.

"That would be expensive and time-consuming," she said. "Instead, they get to play a game of checkers -- leave storage slots empty surrounding the deteriorated panels."

Diane Turco, president of the Cape Downwinders, expressed her dissatisfaction with the solution to the problem.

"Shuffling assemblies in the pool is a dance of danger," Turco said. "What would happen if the (deterioration) rate continued? It seems critical to move the fuel to dry casks now rather than having to answer that question."

Under Phase 2 of Entergy's plan to address panel deterioration, the company will move some fuel assemblies into dry casks, beginning sometime next year.

The plan calls for filling another nine dry casks, adding to the eight currently loaded with 544 spent fuel assemblies and situated on a concrete pad outside the reactor building. Each cask holds 68 assemblies.

The shift to dry casks serves a dual purpose. Without emptying some spent fuel rods out of the pool, there would not be enough room in safe areas to store the hot fuel assemblies that will be removed from the reactor in June 2019, when Pilgrim is shut down permanently, Sheehan said.

The nine new casks will allow for the removal of 612 assemblies, making room for the 580 currently in the nuclear reactor.

David Lochbaum, director of the nuclear safety program for the Union of Concerned Scientists, called the recent rearrangement of the fuel pool "a reasonable way to deal with the situation."

"For their plans, they are only a couple more years of operation," said Lochbaum, referring to Pilgrim's planned 2019 closure. "By moving the fuel in the pool, you're using distance as protection. The measure reduces dependence on boraflex."

When the reactor shuts down, the site will be storing 4,114 radioactive spent fuel assemblies -- with about 1,100 in dry casks and 3,000 in the pool. Currently there is no permanent or interim storage facility available to store the rods away from the Plymouth site.

-- Follow Christine Legere on Twitter: @ChrisLegereCCT.


(c)2017 Cape Cod Times, Hyannis, Mass.

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