US-based Holtec International said on 16 December that three days earlier the last multi-purpose canister containing used fuel at the US Pilgrim NPP had been placed in dry storage, emptying its reactor building of all fissile material and setting a new industry record for the speediest transfer of the plant’s used nuclear fuel to on-site storage.
To achieve this, the Holtec team had to design and build an innovative device to retrieve a severely damaged fuel assembly lodged in a fuel rack cavity since the 1970s, which had thwarted all prior attempts to retrieve and containerise it.
The defuelling of the plant, “conducted with seamless safety and below the allotted crew dose”, was completed two and a half years (30 months) after Pilgrim’s permanent shutdown on 31 May 2019, Holtec said. After the shutdown, the Holtec team loaded a total of 45 high-capacity HI-STORM 100 systems over two loading campaigns, with MPC-68 multi-purpose canisters. The Holtec team loaded 11 casks in the 2020 campaign and loaded an additional 34 casks during the final loading campaign that began in June and wrapped up on 13 December.
“The design and manufacturing know-how developed to extricate the legacy failed fuel assembly at Pilgrim is now available to any nuclear plant facing the problem of retrieving a severely damaged fuel assembly,” Holtec noted.
In total, 62 HI-STORM 100 systems are now safely stored at Pilgrim’s new Independent Spent Fuel Storage Installation (ISFSI). As part of the campaign, all 62 systems were relocated to the new ISFSI built at the plant site in 2020. This new record set by Holtec’s Site Services team at Pilgrim improved upon a similar record-breaking defuelling of one of Holtec’s other shut down plants, Oyster Creek in New Jersey, during this summer.
“We hail the record-breaking defuelling of Pilgrim made possible by the leadership of Steven Soler, our Director of Domestic Site Services and Pilgrim Site VP John Moylan supported by a superbly trained team of craftsmen and technicians,” said Holtec Decommissioning International President Kelly Trice. “We should also thank our inventive professionals in the Nuclear Power Division who devised a brilliant solution to delicately extricate a severely damaged fuel assembly lodged in Pilgrim’s spent fuel rack, creating in the process a new technology to deal with damaged fuel assemblies.”
Pilgrim’s used nuclear fuel will remain safely stored in the HI-STORM 100 dry casks at the onsite ISFSI until the US government takes possession of it (which they are required to do under a 1982 law) or the canisters are transferred to an alternative location, such as Holtec’s proposed HI-STORE Consolidated Interim Storage Facility (CISF) which is undergoing licensing by the Nuclear Regulatory Commission. Final regulatory approval of the HI-STORE CISF is expected in early 2022.
Photo: HI-STORM Overpacks Loaded with Pilgrim Fuel at a Compact On-Site Storage Facility (Photo: Holtec International)