Facility demand
Average facility power is average IT load multiplied by PUE. Peak facility demand is entered separately so cooling and other coincident peaks can be represented.
Pfacility,avg = PIT,avg × PUE
What the calculator separates
Reactor nameplate capacity, annual generation and continuity of supply are different questions. The model therefore checks them independently.
1 · Facility loadConvert average IT demand into average and peak facility power.
2 · Normal capacityFind the minimum modules needed to serve peak demand.
3 · One module unavailableTest a trip and a planned refuelling outage with selected support.
4 · Annual energyCompare capacity-factor generation with annual facility demand.
Campus preset
Module preset
1 · Data center demand
average IT load → facility loadAverage power used by servers and IT equipment.
Average total facility power divided by average IT power.
Include cooling, electrical losses and coincident peak margin.
Average facility load: —
2 · Nuclear supply
technology-neutral module assumptionsUse net electrical output delivered at the plant boundary.
Used for annual energy only—not for the N+1 capacity check.
N+1 here means one reactor module unavailable.
3 · External and bridging support
entered capacity is assumed availableImport capacity credited during a module outage.
Non-battery onsite generation available for the event.
Credited only for the short trip check.
Usable energy equals discharge power × duration.
Refuelling rule: battery capacity is not counted as support for a multi-week planned outage. Only remaining reactor modules, firm grid import and firm backup generation are credited.
Recommended screening configuration
N+1 basisRequired modules
—
—
Installed nuclear
—
net electrical capacity
Average facility load
—
IT load × PUE
Peak normal margin
—
all modules available
Annual energy balance
—
—
Planned module outages
—
—
Result: Enter valid inputs.
Power-capacity comparison
MW at facility peaknuclearremaining nucleargrid + backupshort-duration battery
Contingency and energy checks
selected configuration| Capacity-only minimum | — |
|---|---|
| After one-module loss | — |
| Short-trip margin with all support | — |
| Refuelling margin without battery | — |
| Battery bridge check | — |
| Annual facility demand | — |
| Annual nuclear generation | — |
| Annual nuclear coverage | — |
Annual surplus is an arithmetic energy balance. It does not prove that the surplus can be exported or that every hourly load can be met.
How the model works
transparent screening equations
Module count
The capacity-only count is peak load divided by net output per module, rounded up. For N+1, the design must also pass the one-module-unavailable refuelling check.
Ncapacity = ceil(Ppeak / Pmodule)
Annual energy
Annual nuclear generation uses the entered capacity factor. Planned outage inputs describe scheduling frequency but are not deducted again because their effect should already be reflected in capacity factor.
Enuclear = N × Pmodule × 8,760 × CF
Interpretation and limitations
read before using the result
Capacity factor is not a reliability guarantee
Capacity factor measures annual energy production relative to continuous full-power operation. Two projects with the same capacity factor can have different forced-outage rates, maintenance schedules and common-mode risks. This calculator therefore does not use capacity factor in the instantaneous N+1 capacity equation.
What the N+1 check includes
The N+1 case removes one complete reactor module. The short-trip check credits remaining nuclear capacity, firm grid import, firm backup generation and battery discharge power. The planned-refuelling check excludes the battery because a multi-week outage normally exceeds practical battery energy duration.
It does not model simultaneous grid loss, common-cause events, switchgear faults, transformer failures, bus topology, black start, protection or the reliability of the credited support sources.
Why peak demand is entered separately
PUE is normally an annual or operating-period ratio. Multiplying average IT load by average PUE gives average facility demand, not necessarily the coincident peak. Peak cooling, UPS losses, charging, redundancy and ambient conditions can produce a different maximum. The calculator therefore requires an explicit peak facility value and warns when it is lower than the calculated average.
What the annual energy balance does not show
A positive annual balance means calculated nuclear generation exceeds calculated facility consumption over a year. It does not establish hourly matching, export rights, transmission capacity, minimum stable reactor power, load-following capability, curtailment, market value or the availability of another consumer for surplus electricity.
Major project questions outside this model
- Reactor licensing, safeguards, security and emergency planning.
- Fuel availability and refuelling logistics.
- Cooling-water supply, heat rejection and environmental limits.
- Site hazards, grid studies and electrical distribution reliability.
- Capital cost, construction schedule and commercial arrangements.
- Whether a reactor design permits the assumed operating and staffing model.
Frequently asked questions
common sizing questions
How many nuclear reactors does a data center need?
Divide peak facility demand by net reactor-module output and round up for the capacity-only minimum. If one module must be allowed to trip or refuel without interrupting the data center, test the remaining modules together with only the support sources that can actually remain available.
Does nuclear capacity factor prove that the site has reliable power?
No. Capacity factor is an annual energy measure. It does not replace availability, reliability, common-cause failure, electrical distribution or grid studies.
Can a battery cover a nuclear refuelling outage?
A battery can bridge a short event when both its MW and MWh ratings are sufficient. This model does not count battery capacity as multi-week refuelling support. Grid import or firm backup generation is required if the remaining reactor modules cannot serve the selected load.
Is a 300 MWe SMR automatically a good match for a 100 MW data center?
Not necessarily. One module may substantially exceed the campus load, while a nuclear-only N+1 criterion can require a second module. Unless surplus electricity has another use, a smaller module, firm grid connection or shared generation arrangement may fit better.
Technical references
official sources and model context
[1] U.S. Department of Energy — Advantages and Challenges of Nuclear-Powered Data Centers. Discusses data-center power ranges, refuelling, colocation and possible reactor scales. DOE page ↗
[2] International Atomic Energy Agency — What are Small Modular Reactors? Defines SMRs up to 300 MWe and discusses incremental deployment and limited-grid applications. IAEA page ↗
[3] U.S. Energy Information Administration — The Nuclear Fuel Cycle. Notes that typical reactor operators replace part of the core every 12 to 24 months. EIA page ↗
[4] U.S. Energy Information Administration — Electric generator capacity factors. Official definitions and historical capacity-factor tables for generator technologies. EIA table ↗
The module-size buttons are generic comparison presets, not statements that any particular design is licensed, commercially available or suitable for a data-center project.