# Small Modular Reactors (SMRs)

Canonical URL: https://menfem.com/kb/energy/concepts/small-modular-reactors
Knowledge base topic: [Energy](https://menfem.com/kb/energy)
Frontier status: active
Tags: nuclear, smr, advanced-reactor

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Small Modular Reactors are nuclear reactors with output typically under 300 MWe (vs. 1,000–1,600 MWe for conventional), designed for factory fabrication and modular assembly — in principle allowing faster construction, lower upfront capital, and siting flexibility (including co-location with datacenters). They are the next-generation nuclear bet being made by hyperscalers and governments.

The case is compelling in theory: a 50–300 MW reactor could be purpose-built adjacent to a large datacenter campus, eliminating transmission losses and grid interconnection delays. Factory production (analogous to aircraft manufacturing) could eventually lower costs relative to one-off, on-site construction of large LWRs. And SMRs use diverse fuel cycles and coolant types — some are designed for HALEU (High-Assay Low-Enriched Uranium), enabling higher burnup and potentially lower fuel costs.

In practice, SMRs face significant near-term headwinds. No commercial SMR has operated in the US. The regulatory path (NRC construction permit → operating license) is multi-year. Construction permit decisions for TerraPower (Natrium) and X-energy (Xe-100) are expected in H1 2026 and late 2026, respectively — but first power for these demonstration projects is 2030 at the earliest. NuScale, the only NRC design-approved US SMR developer (77 MWe module), cancelled its first project (UAMPS, Utah) in 2023 due to cost escalation, and is now pursuing a TVA partnership for up to 6 GW.

## Key SMR Approaches

| Company | Technology | Coolant | Output | Status (Jun 2026) |
|---------|------------|---------|--------|--------------------|
| NuScale | LWR (iPWR) | Light water | 77 MWe/module | NRC design approved; TVA MOU |
| TerraPower (Natrium) | SFR + molten salt TES | Sodium | 345 MWe base / 500 MWe peak | Non-nuclear construction at Kemmerer WY; NRC permit expected H1 2026 |
| X-energy (Xe-100) | HTGR | Helium (gas) | 80 MWe/module | NRC safety eval target Nov 2026; Amazon-backed DOE demo |
| Kairos Power (KP-FHR) | FHR | Fluoride salt | 140 MWe | Early construction; Google PPA |
| Oklo (Aurora) | SFR | Sodium | 15 MWe | NRC application; Altman-chaired |
| Rolls-Royce SMR | LWR | Light water | 470 MWe | UK regulatory pre-approval; US entry TBD |
| Last Energy (micro-PWR) | LWR | Light water | 20 MWe | Purpose-built for datacenters; pre-application |

## Key Claims

- **NRC expected to issue first commercial SMR construction permits in 2026** — TerraPower and X-energy are the lead candidates. *Evidence: strong* (American Bar Association, DOE)
- **NuScale remains the only NRC design-approved US SMR**, with a 77 MWe module (uprated from 50 MWe in May 2025), and a 6 GW TVA partnership non-binding agreement. *Evidence: strong* (DOE, NRC)
- **TerraPower's Natrium has begun non-nuclear construction at Kemmerer, WY** (retiring coal plant site); NRC environmental review complete; final safety evaluation December 2025. *Evidence: strong* (Yale Clean Energy Forum)
- **First SMR power in the US is not before 2030** — the regulatory path and construction timeline make sub-2030 commercial operation extremely unlikely. *Evidence: strong* (consensus assessment)
- **Google signed contracts with Kairos Power and X-energy** — the hyperscaler SMR bet is on factory-built, purpose-adjacent units. *Evidence: strong*
- **NuScale is the only SMR with full NRC design certification** (standard design approval granted Jan 2023) — a regulatory moat; its module is 77 MWe, scaling to 924 MWe (12 modules) in a VOYGR plant. *Evidence: moderate* (SEC 8-K, summary-derived, [nuscale-q1-2026-context](../../raw/nuscale-q1-2026-context.md))
- **Oklo targets its first reactor ~2027, ahead of most peers**; NuScale's NRC certification is the reference point against which Oklo and others are measured. *Evidence: moderate* (multi-source synthesis, [hyperscaler-nuclear-procurement](../../raw/hyperscaler-nuclear-procurement.md); [nuscale-q1-2026-context](../../raw/nuscale-q1-2026-context.md))
- **Hyperscaler demand is now underwriting advanced-reactor scale-up: Meta's 6.6 GW deal alone commits 1.2 GW to Oklo (first reactors as early as 2030) and 2.6 GW + 1.2 GW storage to TerraPower (two Natrium units online as soon as 2032).** Neither developer holds an NRC construction permit yet; TerraPower completed its safety evaluation Dec 2025. *Evidence: weak* (single news item, [Latitude Media](../../raw/meta-66gw-nuclear-deal.md))

## Benchmarks & Data

- SMR output range: 15 MWe (Oklo Aurora microreactor) to 470 MWe (Rolls-Royce)
- NuScale 6-module plant: 462 MWe total; full 12-module VOYGR plant scales to 924 MWe ([nuscale-q1-2026-context](../../raw/nuscale-q1-2026-context.md)); cost estimate escalated from $5.3B to ~$9.3B (2023 cancellation driver)
- Natrium: 345 MWe base output, with molten-salt thermal energy storage allowing 500 MWe peak; co-located with Wyoming coal retirement
- HALEU enrichment: <20% U-235 (vs <5% for conventional LWR); only US commercial HALEU enricher is Centrus Energy (LEU)

## Open Questions

- Will factory manufacturing actually reduce costs relative to large LWRs? (NuScale UAMPS cancellation suggests not yet)
- Can SMRs get construction timelines below 5 years? (Current estimates 7-10 years)
- Does the Google/Kairos KP-FHR fleet strategy produce meaningful data on factory-build economics?
- Who supplies HALEU at scale if the US fleet of advanced reactors scales? (Centrus alone is insufficient)
- Will any SMR achieve commercial power before 2030?

## Related Concepts

- [Conventional Nuclear](./conventional-nuclear.md) — existing fleet context
- [Uranium Fuel Cycle](./uranium-fuel-cycle.md) — fuel supply, HALEU challenge
- [Power Purchase Agreements](./power-purchase-agreements.md) — hyperscaler SMR contracts

## Changelog

- **2026-06-15** — Initial compilation from web research (Yale Clean Energy Forum, WWT, ABA, DOE, NRC)
- 2026-06-24 — Compiled new sources (meta-66gw-nuclear-deal, nuscale-q1-2026-context, hyperscaler-nuclear-procurement)

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Cite as: MenFem Knowledge Base — https://menfem.com/kb/energy/concepts/small-modular-reactors