Inside Michigan’s Palisades reactor vessel, fuel assembly DD41 tipped to a 30 degree lean on August 30, and regulators approved a custom tool built to lift it out
At the bottom of a water filled steel vessel in Covert, Michigan, a single bundle of nuclear fuel rods leans against its neighbors instead of standing straight.
It has rested that way since late August.
Above it, engineers spent six weeks building a tool that exists for one job only.
The filing noted plainly that the tilt was not an intended outcome of core loading, so the need for an amendment could not have been foreseen beforehand.
The vessel belongs to the Palisades nuclear plant, closed in 2022 and now fighting to return to service after decommissioning.
That comeback stalled the moment one fuel assembly refused to sit flat.
So what actually went wrong inside the core?
What made the fuel assembly tip over in the first place
A fuel assembly is a long rectangular bundle of thin metal tubes packed with uranium pellets, lowered into the reactor core one at a time by a remote controlled refueling machine. The machine grips each bundle from above, guides it down a narrow channel and releases it once seated on the core plate below.
On August 30, that release did not go as planned. According to the license amendment request filed with regulators, the assembly identified as DD41 was placed in core location H1, but it tilted after being released, settling at a 30 degree angle from the core plate.
The lower tie plate stayed in its core location, while the upper tie plate ended up leaning against the core shroud on the far side of the core. Inspectors found the fuel rods had maintained their integrity, and none of the other assemblies were impacted.
Even so, the upper tie plate, the frame the refueling machine normally grips to lift an assembly out, had been damaged in the fall.
A reactor that was never supposed to need this fix
Palisades sits on the shore of Lake Michigan, an 805 MWe pressurized water reactor that generated power for more than 50 years before its operator shut it down in 2022. The current owner bought the site soon after, originally to dismantle it, then reversed course and began preparing to restart it instead.
By late August 2026, the plant had cleared years of inspections and reached the moment that mattered most. Loading of the 204 assembly core, which includes some partially used fuel from the plant’s final operating cycles, began on August 30, the same day the tilt occurred, and the incident froze that process almost immediately.
Regulators moved quickly to confirm there was no radiological release and that no workers or members of the public were affected, though the operator paused loading while it addressed the stuck assembly. That pause left one leaning bundle standing between Palisades and the history it was built to make.
How investigators and engineers worked the problem
A request for a one time license amendment went in on September 30, asking for approval within two days, a compressed timeline justified by the argument that the stalled assembly was blocking the broader restart. The public comment window closed October 8, and the commission issued its decision on October 13, a turnaround regulators described as exigent, meaning handled under urgent circumstances.
The fix approved was a piece of custom hardware, not a change to the fuel itself. Engineers had built a custom recovery tool and a fuel transfer canister to support and enclose the assembly during transit from the vessel to the spent fuel pool, since the standard grapple could no longer grip the bent tie plate.
Regulators were explicit that this was a one time fix, granting permission to remove the assembly using an alternative method, with the review confirming the work can be carried out safely under existing requirements.
Why one tilted bundle carries so much weight
Palisades is not an ordinary restart. If it reaches full power, it becomes the first reactor to return from a declared decommissioning status, a reversal the industry has never managed before, and that precedent is part of why a single stuck fuel bundle drew national attention rather than a routine maintenance note.
The operator has framed the episode as a solvable complication rather than a structural setback. Other restart work at the site, including generator and turbine refurbishment, continued through the pause.
The filing noted plainly that the tilt was not an intended outcome of core loading, so the need for an amendment could not have been foreseen beforehand. Federal loan support also backs two other shuttered reactors working toward similar comebacks on different timelines and under different regulatory histories, part of a wider effort to return dormant nuclear capacity to the grid as electricity demand climbs. The regulator’s own account of the approval confirms the review found the recovery method safe and compliant.
What happens once the bundle finally lifts free
With the amendment in hand, workers can lower the custom canister into the vessel, slide it around the leaning assembly without dragging the damaged tie plate across the core shroud, and carry the bundle through a different travel path than the one in the plant’s original safety filings. Every step of that transit is choreographed and timed.
Once DD41 is seated safely in the spent fuel pool, loading of the remaining assemblies can resume, moving the plant toward the testing phase that precedes any return to the grid.
No firm restart date has been set publicly since the incident, though prior guidance pointed toward the plant reaching operation sometime in 2026 before the tilt intervened. For a reactor built to prove that decommissioned need not mean permanent, the fix for one 30 degree lean may end up as a footnote, a reminder that even a plant with federal backing and decades of operating history still answers to the smallest tolerances in its own core.
Hugo is an engineer with strong technical expertise. Multilingual from an early age, his writing combines technical clarity with a strong interest in science and energy.
