On December 13, 2021, workers at Pilgrim Nuclear Power Station in Plymouth, Massachusetts sealed the last canister of spent nuclear fuel and moved it into dry storage — emptying the reactor building of all fissile material in a feat that set a new world record for decommissioning speed.
The milestone capped a 30-month effort that began the day Pilgrim shut down permanently in May 2019. But the race nearly stalled before the finish line, held up by a single damaged fuel assembly stuck in a reactor rack since the 1970s — one that had resisted every removal attempt for decades.
A record 30 months from shutdown to empty pool
Pilgrim permanently shut down on May 31, 2019, and Holtec’s team moved fast. The defueling operation unfolded across two loading campaigns: 11 HI-STORM 100 cask systems loaded in 2020, then a final campaign starting in June 2021 that concluded December 13 with 34 more casks sealed and transferred to dry storage. Both campaigns together totaled 45 high-capacity systems, each fitted with MPC-68 multi-purpose canisters.
The operation finished below the allotted crew radiation dose — a detail carrying as much weight as the speed record itself. Moving quickly through a nuclear defueling without accumulating excess dose demands careful planning, disciplined execution, and a workforce trained to operate efficiently in radiological environments. Holtec’s team delivered on both counts.
The 30-month timeline also beat Holtec’s own previous record, set at Oyster Creek in New Jersey earlier that same year. Back-to-back records at two separate sites suggests something more than favorable conditions — it reflects a repeatable operational approach.
The damaged fuel assembly that stumped engineers for decades
The record almost didn’t happen. Somewhere in Pilgrim’s spent fuel pool sat a single severely damaged fuel assembly, lodged in a rack cavity since the 1970s, with every prior retrieval attempt having failed. The assembly was fragile enough that a poorly executed extraction could scatter fuel material rather than contain it — a scenario that would have complicated the entire defueling operation and made completing the pool transfer impossible.
Holtec engineers couldn’t adapt an existing tool. They designed and built an entirely new retrieval device from scratch, purpose-built to extract the damaged assembly without causing further breakup or dispersal. That required close coordination between site services teams at Pilgrim and engineers in Holtec’s Nuclear Power Division who understood both the mechanics of damaged fuel and the physical constraints of working inside an active spent fuel pool.
The retrieval succeeded. With that obstacle cleared, the path to an empty pool — and a world record — was open.
A new tool for the entire nuclear industry
What happened at Pilgrim didn’t stay at Pilgrim. The design and manufacturing knowledge developed to extract that legacy assembly is now available to any nuclear plant facing a comparable problem, turning a challenge that once stalled a project for decades into a documented, transferable solution.
That kind of knowledge transfer carries real weight in an industry where decommissioning activity is accelerating. As more reactors reach end of life, the odds of encountering damaged or degraded fuel assemblies — some of them decades old — only grow. Having a proven retrieval method on hand rather than starting from zero each time could meaningfully reduce both cost and schedule risk across future projects.
Holtec Decommissioning International President Kelly Trice credited the outcome to Director of Domestic Site Services Steven Soler and Pilgrim Site VP John Moylan, along with what he described as a “superbly trained team of craftsmen and technicians.” He also singled out the Nuclear Power Division engineers who devised what he called a “brilliant solution” to the damaged assembly problem.
Where Pilgrim’s spent fuel goes from here
All 62 HI-STORM 100 cask systems — the 45 loaded during the defueling campaigns plus casks already in place — now sit at a new Independent Spent Fuel Storage Installation built on the Pilgrim site in 2020. The fuel is secure, dry, and retrievable. It isn’t going anywhere soon.
Under a 1982 federal law, the U.S. government is required to eventually take possession of spent nuclear fuel from commercial reactors. That obligation remains unfulfilled, with no permanent repository yet in operation. Spent fuel from decommissioned plants like Pilgrim stays in on-site dry storage — a safe arrangement, but one that leaves communities and site owners in a prolonged holding pattern.
One potential intermediate step is Holtec’s proposed HI-STORE Consolidated Interim Storage Facility in New Mexico. When Pilgrim’s pool was emptied, the facility was undergoing Nuclear Regulatory Commission licensing, with approval expected in early 2022. HI-STORE is designed to provide centralized, retrievable interim storage for spent fuel from multiple plants while the Department of Energy works toward a permanent disposal solution.
For now, Pilgrim’s fuel rests in Plymouth. The record is set, the pool is empty, and the longer arc of the spent fuel problem — shared by decommissioning sites across the country — continues to unfold.
Carlos is an engineer with strong expertise in technical and industrial topics. He previously worked at international companies such as Siemens and speaks Spanish, German, English, and Italian.
