Pilgrim oversight shifts to decommissioning
By Christine LegerePosted Jun 11, 2019
NRC wants evidence that spent fuel pool protections adequate.
PLYMOUTH — The Nuclear Regulatory Commission is looking for additional assurance from the owner of Pilgrim Nuclear Power Station that the large spent fuel pool where 3,000 radioactive assemblies are cooling is adequate to prevent a nuclear reaction.
Pilgrim operators have transferred all 581 radioactive fuel assemblies from the reactor, which permanently shut down May 31, to the spent fuel pool.
The commission acknowledged completion of that task Tuesday in a letter to Entergy Corp., the plant’s owner, saying oversight would now switch from the agency’s operations branch to its decommissioning branch.
The NRC also has asked Entergy to provide additional proof that the protections in the spent fuel pool are adequate.
Spent fuel pools at nuclear power plants store highly radioactive fuel assemblies removed from reactors when they are no longer usable. The assemblies are kept under at least 20 feet of water to prevent any radiation from leaking into the atmosphere.
Boraflex panels were installed in the 1980s when fuel pools at nuclear plants were accommodating more spent fuel than they were originally designed to hold.
The panels contain neutron-absorbing boron carbide and are attached to racks holding bundles of radioactive fuel. They prevent fission, which would cause the spent rods to heat up the same way they do in a nuclear reactor. The heat would cause the water in the pool to boil and evaporate. If exposed, the rods could ignite and result in a radiation release.
Over time, exposure to radiation and constant submersion in water has eaten away at the protective boron carbide shields.
Entergy Corp. had evaluated the condition of the Boraflex panels at Pilgrim in December 2016 and estimated 885 were in danger of deteriorating.
The solution simply was 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 in 2017, and some were transferred to dry casks. NRC inspectors determined those measures were adequate to preserve safety.
The assemblies were shifted again more recently to make room for the hot fuel coming from the reactor, according to Entergy spokesman Patrick O’Brien.
“We have taken a number of actions and had multiple inspections since the issue regarding the Boraflex panels was first identified,” O’Brien said via email. “In addition, we have safely offloaded the core to the spent fuel pool following shutdown of the plant on May 31, and this additional information requested will allow the NRC to complete their safety review.”
NRC spokesman Neil Sheehan confirmed that, saying “the staff is now seeking assurances that subcriticality can be maintained in the pool for the next several years, until all of the spent fuel housed there can be loaded into dry casks.”
Federal regulators have been told the fuel should be out of the pool and stored in heavy dry casks in just under three years.
“Both Entergy and Holtec, in the event the latter is approved to purchase the plant, have said they intend to work on conducting those fuel transfers as a top priority following shutdown,” Sheehan said.
Holtec International is looking to buy the Pilgrim plant, which carries with it a $1.1 billion decommissioning trust fund, and handle dismantling of the buildings, removal and disposal of the reactor and other equipment, managing the spent fuel and cleaning up the site.
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