Nuclear outages
Nuclear Refueling Outage Planning: Duration, Scope and Schedule
US nuclear refueling outages averaged 34 days in 2024 through 31 July and 38 days in 2023 according to the US Energy Information Administration, and are scheduled mostly in spring and fall. Reactors typically refuel every 18 to 24 months. This page shows the figures, a scope framework and why outages run long.
Figures are from US EIA Today in Energy articles dated October 2023 and November 2024. No operator-internal practice is described.
How MaintWiz helps: Outage duration depends on how well scope and schedule are controlled. The MaintWiz shutdown module puts the whole shutdown on a Gantt chart with the critical path, float and baselines, so you can see what moves the finish date. See the module · Get the Gantt template
By Jai Balachandran · Published · Last reviewed
What MaintWiz adds:Gantt with critical path and floatBaselines show what movedFloat flag at your limitOne plan from portfolio to task
Duration
How long is a US nuclear refueling outage?
EIA reports that US nuclear refueling outages averaged 34 days in 2024 through 31 July and 38 days in 2023, with a spread from about 10 days for the refueling itself to 89 days for the longest 2023 outage in its data. 1,2,3
Reporting terms are in the shutdown turnaround glossary; spreadsheets are in the free shutdown templates.
- 34 daysUS average refueling outage, 2024 to 31 July (EIA, Nov 2024)
- 38 daysUS average in 2023 as reported in Nov 2024; 35 days as of 3 Oct 2023 (EIA, Oct 2023)
- 59 daysLongest outage in the 2024 data, Sequoyah Unit 2 (EIA)
- 89 daysA 2023 outage at Millstone, the longest in the Oct 2023 article
| Period | Average | Detail | Source |
|---|---|---|---|
| 2022 | 38 days | As stated in the October 2023 article; the November 2024 article does not give 2022 refueling figures | EIA, October 2023 |
| 2023, to 3 October 2023 | 35 days | Outages starting in April and May averaged 34 days; Millstone (Connecticut) was offline 89 days; Columbia Generating Station began a 44-day outage in early May | EIA, October 2023 |
| 2023, as reported in November 2024 | 38 days | Full-year figure as stated in the later article, which compares 2024 with 2023 | EIA, November 2024 |
| 2024, to 31 July 2024 | 34 days | Longest: Sequoyah Unit 2 at 59 days, then Surry Unit 1 at 58 days; Fermi Unit 1 and South Texas Project Unit 2 at 48 days each | EIA, November 2024 |
EIA says refueling itself can be done in as few as 10 days, though outage periods are typically longer. 3 Averages for part of a year are provisional and change as more outages finish, which is why the 2023 figure differs between the two articles: 35 days as of 3 October 2023, and 38 days in the later article.
The figures are as published by EIA on the dates shown; check the latest EIA Today in Energy and the NRC outage status data for current numbers.
Timing
When are US refueling outages scheduled?
US reactors typically refuel every 18 to 24 months, and operators schedule refueling outages mostly in spring and fall, when electricity demand is lower, and avoid summer and winter peaks. 2,3,1
Seasonal timing for other generators is in power plant outage management.
EIA's 2024 article lists planned outages beginning in September and October and notes that operators usually avoid scheduling them in summer and winter. 1 Seasonal timing also applies to other generators; see power plant outage management and how often a plant should shut down.
Software
Can software support an outage like this?
Software can hold an outage schedule with float, readiness gates, findings and permits together; MaintWiz is an industrial AI platform, and it does not claim any nuclear-specific licensing or regulatory capability.
About MaintWiz. MaintWiz is an industrial AI platform with IoT, SAP integration and predictive maintenance (PdM) capabilities. Its shutdown and turnaround module helps plants plan, schedule, execute and close out shutdown work.
What the shutdown module covers
As described on the MaintWiz shutdown maintenance product page.
- Gantt chart with the critical path and float, and a flag at a float limit you set
- Baselines that show what moved against the plan
- Resource availability by trade and week
- Readiness gates with waivers and sign-offs recorded with a reason, the name and the date
- Findings from the field sent to the planner as requests for added work
- Permits and isolations from ePTW shown on each work order
Proof
What MaintWiz customers report
Figures as published in MaintWiz case studies on maintwiz.com. They come from maintenance management projects, not shutdowns.
Scope
What is in the scope of a refueling outage?
A refueling outage combines refueling with scheduled maintenance, inspections and tests, planned modifications and discovery work; the scope categories below are a planning framework, and each plant's actual scope is set by its license, its maintenance program and its regulator.
A free Excel version is available: Refueling outage scope tracker (.xlsx).
| Category | What it covers | Planning question |
|---|---|---|
| Refueling | Removing, inspecting and reloading fuel | What sets the critical path through the core offload and reload? |
| Scheduled maintenance | Preventive and corrective work on plant systems that can only be done offline | Which jobs need which system out of service? |
| Inspections and testing | Periodic inspections and tests that need the unit shut down | Which are fixed by the regulator or the license? |
| Modifications | Planned plant changes done in the window | Is the design and procurement complete before the freeze? |
| Discovery work | Work found by inspection during the outage | Is there float and crew held for it? |
NERC's generation reporting terms distinguish original scope of work from discovery work for generating units; the same planning logic applies. 5 For scope control see shutdown scope management.
Why outages run long
Why do some refueling outages run long?
EIA reports the spread in outage lengths but does not say why individual outages ran long; in schedule terms, an outage runs long when critical-path activities slip or discovery work is added, as the scheduling guides explain. 1,6
See critical path vs critical chain and shutdown schedule delays for how schedules slip.
EIA's data show a wide range: an average of 34 days in 2024 to date against a longest outage of 59 days, and a longest 2023 outage of 89 days. 1,2 The articles do not attribute the long outages to causes. See critical path and float, shutdown schedule delays and scope management for how schedules slip.
Outage classes
How are refueling outages classed in outage reporting?
In NERC generation reporting a nuclear refueling outage is a typical planned outage, scheduled well in advance with a fixed original scope of work, while damage found during a planned inspection that extends the outage is coded as a forced outage. 5
| Class | What it means | Source |
|---|---|---|
| Planned outage (PO) | Scheduled well in advance, of a predetermined duration, lasting several weeks and occurring once or twice a year; turbine and boiler overhauls, inspections, testing and nuclear refueling are typical planned outages | NERC GADS |
| Maintenance outage (MO) | Can be deferred beyond the end of the next weekend but must happen before the next planned outage; usually much shorter than a planned outage | NERC GADS |
| Forced outage (U1, U2, U3) | Immediate, delayed (removal within six hours) or postponed; damage found during a planned inspection that extends the outage is coded forced | NERC GADS |
NERC GADS covers generating units in North America; check its current reporting instructions. It does not set outage lengths.
Visuals
Save the refueling outage charts
Two charts to share with your planning team. Click either for the full-size image.
FAQ
Frequently asked questions
How long is a US nuclear refueling outage?
EIA reports averages of 34 days for 2024 to 31 July and 38 days for 2023, with the longest 2024 outage at 59 days. 1
How fast can a refueling be done?
EIA says the refueling process can be completed in as few as 10 days, though outage periods are typically longer. 3
When are refueling outages scheduled?
Mostly in spring and fall, when electricity demand is lower. 2,1
What is in the scope of a refueling outage?
Refueling, scheduled maintenance, inspections and tests, planned modifications and discovery work; the plant's license and program set the actual scope.
Why do some outages run long?
EIA does not give causes. In schedule terms, critical-path slips and added discovery work lengthen an outage.
Is the 2023 average 35 or 38 days?
Both appear: 35 days as of 3 October 2023 in one article, and 38 days for 2023 in a later one. 2,1
Does MaintWiz offer nuclear licensing support?
No. This page covers outage planning in general; MaintWiz does not claim nuclear-specific regulatory capability.
Sources
Sources
- US Energy Information Administration, Today in Energy: U.S. summer nuclear outages declined in 2024, returning to 2022 levels (5 November 2024)
- US Energy Information Administration, Today in Energy: U.S. summer nuclear outages rose in 2023, returning to 2021 levels (17 October 2023)
- US Energy Information Administration, Today in Energy on nuclear refueling outages (8 November 2023)
- U.S. Energy Information Administration, Nuclear power plants undergo seasonal scheduled outages (23 May 2011)
- North American Electric Reliability Corporation, Generating Availability Data System (GADS) Data Reporting Instructions, effective 1 January 2026
- US Government Accountability Office, GAO Schedule Assessment Guide: Best Practices for Project Schedules (GAO-16-89G, December 2015)
Put your shutdown schedule in one plan
Book a demo and bring your shutdown schedule. We will show how the module handles the critical path, float and baselines.