How a US nuclear plant restart works, from licence to grid

Restarting a shut US reactor is a sequence of separate approvals and physical jobs. The owner has to undo the paperwork that ended its right to hold fuel, restore its emergency and security plans, repair and test the plant, train operators, load fuel, and get its grid connection back. Three plants are on this path: Palisades in Michigan, the Crane Clean Energy Center in Pennsylvania, and Duane Arnold in Iowa. Palisades is the furthest along, and its record shows how a single step can pause the rest.

This post is the process view. It walks through each step in the order the Nuclear Regulatory Commission (NRC) and the owners describe it, using NRC licensing records, Department of Energy (DOE) loan pages and company releases. The commercial deals behind the restarts, including the Microsoft and Google contracts, are covered in a related post, Nuclear power for AI data centres: restarts, uprates, new reactors, so they appear here only briefly. Nothing here is investment advice or a forecast.

Key numbers at a glance

• Palisades size: 805 MWe design output for its 204 assembly core (Holtec, 30 August 2026).
• Palisades shutdown: ceased operations 20 May 2022; licence expires 24 March 2031 (NRC facility page, updated 14 October 2026).
• Palisades return to operating basis: NRC approvals issued 24 July 2025; Holtec rescinded its shutdown certifications on 25 August 2025 (NRC facility page, as of 14 October 2026).
• Palisades federal loan: up to 1.52 billion dollars, closed September 2024 (DOE project page, accessed 19 October 2026).
• Palisades fuel loading: began 30 August 2026 (Holtec, 30 August 2026); NRC licence amendment to recover a tilted assembly issued 13 October 2026 (NRC, 14 October 2026).
• Crane size and buyer: about 835 MW, 20 year agreement with Microsoft, originally expected online in 2028 (Constellation, 20 September 2024).
• Crane federal loan: 1 billion dollars, closed November 2025 (DOE project page, accessed 19 October 2026; Constellation, 18 November 2025).
• Crane environmental review: final environmental assessment and finding of no significant impact issued 18 September 2026 (NRC facility page, updated 8 October 2026).
• Crane licence expiry: 19 April 2034 (NRC facility page, as of 8 October 2026).
• Duane Arnold size: 615 MW (DOE, 8 September 2026).
• Duane Arnold federal loan: up to 1.9 billion dollars, closed 8 September 2026 (DOE, 8 September 2026).
• Duane Arnold buyer and target: 25 year agreement with Google, back online in early 2029 (World Nuclear News, 28 October 2025, quoting Google).
• Duane Arnold licence expiry: 21 February 2034 (NRC facility page, updated 14 September 2026).
• Data centre share of US electricity: about 4.4 percent in 2023, projected 6.7 to 12 percent by 2028 (DOE, 20 December 2024).

Why a closed reactor is worth restarting

A closed reactor still has a site, a cooling water source, a transmission connection and, often, a local workforce that knows the plant. Building any of those from nothing takes years. That is the commercial case, and the demand side explains why it has become urgent. DOE reported on 20 December 2024 that data centres used about 4.4 percent of US electricity in 2023, or 176 terawatt hours, and could use 6.7 to 12 percent by 2028, which DOE puts at 325 to 580 terawatt hours. A terawatt hour is one billion kilowatt hours. Data centre buyers want supply that runs day and night, which is what a large reactor provides. For the wider forecast picture, see How much electricity will AI data centres need? Forecasts compared.

None of the three plants closed because the NRC ordered it. Constellation said on 20 September 2024 that Three Mile Island Unit 1, now Crane, was retired in 2019 "due to poor economics". Duane Arnold stopped after an August 2020 derecho damaged non safety parts of the plant, including its cooling towers, according to the NRC. Palisades permanently ceased operations on 20 May 2022, per the NRC facility page. Constellation's release also notes that Three Mile Island Unit 2, the reactor damaged in 1979, is a separate unit being decommissioned by another company and is not part of the restart.

Step 1: Undo the decommissioning paperwork

When a US plant shuts for good, the owner sends the NRC two certifications under the rule at 10 CFR 50.82: that operations have permanently stopped, and that fuel has been permanently removed from the reactor vessel. Once those are on the docket, the licence no longer authorises operation or putting fuel in the reactor. A Constellation licensing presentation filed with the NRC in May 2026 quotes this rule and a 2021 NRC statement that "there is no statute or regulation prohibiting" reauthorising operation, even though the rules do not spell out a mechanism.

That gap is why the restart path is built from existing tools. The NRC's facility pages for all three plants describe the same three requirements. The owner needs NRC approval to restore the plant's licensing basis to operational status, has to return plant components to a condition that supports safe operation, and must make any upgrades the proposed operating basis requires. A licensing basis is the set of documents and commitments that define how a plant is designed, run and kept safe. During decommissioning many of those documents are cut back. The Constellation presentation lists what changes: the safety analysis report becomes a decommissioning version, training shrinks to essentials such as radiation protection, the plant simulator is no longer required, and the security and emergency plans shrink to cover only the spent fuel storage installation.

The NRC sets up a restart panel for each plant to coordinate review, inspection and the decision that the plant is ready. The owner usually opens with a regulatory path letter. Holtec submitted Palisades' path on 1 February 2023, and Constellation's presentation says Crane's letter went in during November 2024.

Step 2: The licensing bundle

The core of the restart is a group of filings that the NRC reviews together. The Constellation presentation describes Crane's version, and the NRC pages for the other two plants list the same pieces:

• An exemption from the 10 CFR 50.82 termination requirements, so the shutdown certifications can be withdrawn.
• A licence amendment to restore the operating licence and technical specifications, the detailed limits the plant must run within.
• A licence amendment to reinstate the full emergency plan.
• A licence amendment to restore the physical security plan for an operating plant. A related post, NRC 73.54 cyber security plans explained, covers one of the security requirements that comes back with operating status.

For Crane, the presentation says these requests were bundled with the exemption, published in the Federal Register in February 2026, and given a single opportunity for a hearing. The NRC's Crane page lists the dates: the exemption request was submitted on 19 November 2024, the licence and technical specification amendment on 31 July 2025, the security plan on 24 October 2025, and the emergency plan on 31 October 2025. No final approval was listed for any of the four as of the page update on 8 October 2026. The latest item shown was an NRC request for additional information dated 25 September 2026 on the licence amendment.

Duane Arnold is earlier. The NRC page lists the exemption request on 23 January 2025, the licence and technical specification amendment on 20 November 2025, the security plan on 17 December 2025 and the emergency plan on 30 January 2026. All four had been accepted for review, with no completion shown as of 14 September 2026.

Palisades shows what the end of this step looks like. The NRC facility page records final documents for the exemption, the revised licence and technical specifications, the reinstated emergency plan and the quality assurance plan on 24 July 2025, along with an order approving the transfer of the licence to the operating company, Palisades Energy. Holtec gave notice of readiness on 1 July 2025 and rescinded its shutdown certifications on 25 August 2025, which the NRC says removed the bar on operation and fuel emplacement. Holtec called the 24 July approval the first time a previously shut down US plant had received approval to return to operations.

Approval of the bundle did not end the paperwork. The Palisades page lists more than a dozen later actions, including steam generator repair approvals in October 2025, relief requests through May 2026 and work hour exemptions for staff through August 2026.

Step 3: Environmental review and state permits

The NRC also has to complete a review under the National Environmental Policy Act. For all three plants it chose an environmental assessment rather than a full environmental impact statement. An assessment is shorter. If it ends in a finding of no significant impact, no impact statement is needed.

For Palisades, the NRC issued the final assessment and finding on 30 May 2025. For Crane, the draft came out on 3 June 2026, the comment period ended on 8 July 2026 and the final version was issued on 18 September 2026. For Duane Arnold, the draft was issued on 30 July 2026, comments closed on 2 September 2026 and the final version was projected for fall 2026, per the NRC page.

State and local approvals run alongside. Constellation's 2024 release said Crane needs permits from state and local agencies. For Duane Arnold, World Nuclear News reported on 8 September 2026 that the Iowa Utilities Commission had issued a certificate in June authorising construction and operation.

Step 4: Inspect, repair and restore programmes

Equipment work happens while the licensing review runs. Constellation's May 2026 presentation describes Crane's condition at that time: most major systems drained and de-energised, no major components removed, the main generator inspected and placed in long term storage condition, and the main power transformers inspected with new transformers to be bought. The steam generators, which pass heat from the reactor coolant to the water that becomes steam for the turbine, were replaced in 2009 and inspected in spring 2024 with no abnormal conditions found.

Holtec's 30 August 2026 release lists what Palisades needed: reinforcing tubes in both steam generators, removing corrosive deposits from them, replacing control rod drive mechanism nozzles, chemically decontaminating the primary system, inspecting the reactor vessel and many equipment upgrades. Holtec said the scope was expanded in several areas. On 10 July 2026 Nuclear Engineering International reported that more than 5,000 individual work activities remained before startup.

Restoration is also about programmes, not just hardware. The Constellation presentation lists in-service inspection and testing, fire protection, aging management, the design change process under 10 CFR 50.59 and fitness for duty work hour rules as programmes that must be brought back to operating standards. Emergency preparedness involves outside agencies. Crane's presentation says the Federal Emergency Management Agency reviews off site response plans and that a joint NRC and FEMA exercise needed for final approval was planned for February 2027.

Step 5: People

A reactor needs licensed operators, and a plant that has been shut for years has lost many of them. Holtec said on 24 July 2025 that the NRC approval let it move licensed reactor operators to on-shift status, and that about 600 full time staff and about 1,000 trades workers and suppliers were working on Palisades. Constellation said on 18 November 2025 that Crane was more than 80 percent staffed with over 500 employees, including licensed operator trainees. Crane's restoration plan also includes recertifying the plant simulator used for operator training, with an NRC inspection of it, according to the Constellation presentation.

Workforce rules continue to matter late in the project. The Palisades NRC page shows several exemptions from work hour limits in 2026. On 13 October 2026 the NRC sent Holtec a letter about a chilled work environment, meaning staff reluctance to raise concerns, in two of its departments. The NRC page says this is not expected to affect the planned restart.

Step 6: Fuel, and what a pause looks like

Fuel can arrive only after the plant is allowed to hold it. World Nuclear News reported on 21 October 2025 that Palisades had received 68 new fuel assemblies, placed them in the fuel pool building after inspection, and at that time targeted restart in the fourth quarter of 2025.

Holtec began loading fuel on 30 August 2026. Its release says this placed the plant in Mode 6, the refuelling mode in its technical specifications, and that the core holds 204 assemblies, a mix of new and partly used fuel. After loading, the plant still has to complete testing, inspections and startup steps.

Loading then stopped. NRC records refer to a tilted assembly in the reactor core. Holtec applied on 30 September 2026 for a one time change to its licensing basis to recover the assembly, identified as DD41, by a different method and path than its safety analysis report describes. Michigan Public reported on 14 October 2026 that Holtec said damage prevented retrieval with the refuelling machine's grapple. The NRC issued Amendment No. 283 on 13 October 2026 under exigent circumstances, a faster process for time critical changes, stating that the amendment was needed to move the assembly out of the reactor cavity so fuel loading could resume. The National reported on 16 October 2026 that the NRC said no radiation was released, and that Holtec had not published a new restart timeline.

Step 7: Money

Restarts are financed with federal loans and long contracts. The DOE pages list all three loans. Palisades has a loan of up to 1.52 billion dollars that closed in September 2024, after a conditional commitment announced in March 2024. A conditional commitment is an offer that becomes a loan only once the borrower meets set conditions. Crane's 1 billion dollar loan closed in November 2025; DOE says it was its first combined conditional commitment and financial close. Duane Arnold's loan of up to 1.9 billion dollars closed on 8 September 2026. Each DOE page makes the restart subject to NRC licensing approvals.

Loans are drawn in tranches, not paid at once. POWER magazine reported on 7 August 2025 that DOE had released a fifth Palisades disbursement of 83.2 million dollars. None of the DOE pages gives a total project cost.

The second funding source is the buyer. A power purchase agreement, or PPA, is a long contract to buy a plant's output. Crane has a 20 year PPA with Microsoft. Duane Arnold has a 25 year PPA with Google, with the Central Iowa Power Cooperative buying the rest on the same terms, per World Nuclear News. Holtec names Wolverine Power Cooperative and Hoosier Energy as its Palisades buyers. Palisades also had state support; World Nuclear News reported in March 2024 that Michigan's 2024 budget included 150 million dollars for the restart. Prices are not public for any of these contracts. A related post, Who pays for AI data centre power, explains PPA structures in general.

Step 8: Get back on the grid

A plant also needs the right to inject power at its connection point, called interconnection rights. When a plant closes, those rights can be reassigned. World Nuclear News reported on 6 August 2025 that NextEra asked the Federal Energy Regulatory Commission (FERC) to restore Duane Arnold's rights, which had been split up to support proposed solar projects. For Crane, a trade summary by Neutron Bytes on 11 August 2026 said FERC approved a waiver in June 2026 transferring 760 MW of capacity interconnection rights. The related post on nuclear deals covers a reported dispute over when the regional grid operator, PJM, could connect Crane. For how FERC handles large connections more generally, see FERC large load interconnection rules explained.

Where the three plants stand

Palisades has its operating basis back, has started fuel loading and is waiting to finish recovery of one assembly. Holtec's first target of the fourth quarter of 2025 has passed.

Crane has filed its whole licensing bundle and finished its environmental review, with final licensing approvals still pending. Constellation's 2024 target was 2028; Neutron Bytes reported in August 2026 a late 2027 target.

Duane Arnold has its bundle under review and its loan closed, with an early 2029 target cited by Google and repeated by World Nuclear News in September 2026.

What is firm and what is uncertain

Firm, from NRC, DOE and company records:

• Palisades returned to an operating licensing basis in 2025 and began fuel loading on 30 August 2026.
• The NRC approved a one time amendment on 13 October 2026 to recover the tilted assembly.
• Crane's environmental assessment is final; its licensing bundle was still under review as of 8 October 2026.
• DOE has closed loans for all three plants: 1.52 billion, 1 billion and up to 1.9 billion dollars.
• Microsoft and Google have long term agreements for Crane and Duane Arnold output.

Uncertain:

• When Palisades will finish fuel loading and start up. No new official date had been published as of 16 October 2026.
• When the NRC will decide on the Crane and Duane Arnold bundles.
• Total restart costs, which none of the DOE pages states.
• Grid timing for Crane, where reports differ.

What to watch next

• Completion of the DD41 recovery at Palisades and the restart of fuel loading.
• NRC decisions on the Crane exemption and licence amendments, and the NRC and FEMA emergency exercise Constellation planned for February 2027.
• The final environmental assessment for Duane Arnold, projected for fall 2026.
• Any change to the 2027, 2028 or 2029 targets in company statements.
• New restart proposals; none beyond these three is covered here.

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Quick check

Sources

• Palisades Nuclear Plant facility page, US Nuclear Regulatory Commission, updated 14 October 2026, accessed 19 October 2026.
• Crane Clean Energy Center facility page, US Nuclear Regulatory Commission, updated 8 October 2026, accessed 19 October 2026.
• Duane Arnold Energy Center facility page, US Nuclear Regulatory Commission, updated 14 September 2026, accessed 19 October 2026.
• NRC approves Palisades license amendment request, S-26-009, US Nuclear Regulatory Commission, 14 October 2026.
• Palisades Nuclear Plant, issuance of Amendment No. 283, US Nuclear Regulatory Commission, 13 October 2026.
• Returning the Crane Clean Energy Center to an operating license basis, Constellation presentation in NRC records, May 2026.
• Palisades project page, US Department of Energy, accessed 19 October 2026.
• Crane restart project page, US Department of Energy, accessed 19 October 2026.
• Energy Department closes 1.9 billion dollar loan to restart Duane Arnold nuclear plant, US Department of Energy, 8 September 2026.
• DOE releases new report evaluating increase in electricity demand from data centers, US Department of Energy, 20 December 2024.
• NRC reauthorizes Palisades operating license, HH 40.15, Holtec International, 24 July 2025.
• Palisades begins the process for loading fuel in its reactor vessel, HH 41.17, Holtec International, 30 August 2026.
• Constellation to launch Crane Clean Energy Center, Constellation, 20 September 2024.
• US government backs Constellation's plan to launch Crane Clean Energy Center, Constellation, 18 November 2025.
• Loan guarantee for Palisades restart, World Nuclear News, 28 March 2024.
• Palisades receives fuel ahead of restart, World Nuclear News, 21 October 2025.
• NextEra seeks to reconnect Duane Arnold to the grid, World Nuclear News, 6 August 2025.
• Duane Arnold restart underpins NextEra Energy and Google collaboration, World Nuclear News, 28 October 2025.
• US Department of Energy closes loan for Duane Arnold restart, World Nuclear News, 8 September 2026.
• DOE approves fifth loan disbursement to Holtec for historic restart of Palisades nuclear plant, POWER, 7 August 2025.
• Palisades restart enters final phase, Nuclear Engineering International, 10 July 2026.
• Regulators approve plan to remove damaged fuel assembly at Palisades, Michigan Public, 14 October 2026.
• The National report on NRC action over the Palisades tipped fuel assembly, The National, 16 October 2026.
• Inside Three Mile Island's quest to clear restart hurdles, Neutron Bytes, 11 August 2026.

Last reviewed: 19 October 2026.