In 2019, Davis-Besse Nuclear Power Station, purchased an array of shielding from NPO for their spent fuel storage campaign. This package included a transfer cask shield bell, canister shield ring, and annulus gap shielding. All of these items contributed to greatly reduced dose rates for both gamma and neutron radiation.
Shield bells are a single-pick piece of shielding that rests directly on the transfer cask and out of the way of the welder. They are typically comprised of steel, borated polyethylene, and lead. The shield bell built for Davis-Besse has cutouts for trunnions to fit the NUHOMS EOS TC as well as chamfered edges to maximize shielding around the openings. DB saw an average reduction of 87% gamma and 62% neutron on contact.
On the EOS canister, a 20-piece T-Flex composite shield ring surrounded the welder. Each piece consisted of 2” of borated polyethylene and 1” of T-Flex® Tungsten. With the neutron shielding (borated polyethylene) facing down, Davis-Besse was able to optimize the shielding effectiveness. A high temperature insulative mat was also provided to protect the shielding pieces.
In addition to those two shielding packages, Davis-Besse utilized annulus gap shielding between the canister and transfer cask. These T-Flex® Tungsten shields are covered in high temperature weld blanket material and ensured that there were no gaps or streaming that would expose workers to unnecessary radiation.
With all the NPO shielding in place, Davis-Besse was able to have a very successful spent fuel storage campaign.