How to Evaluate SMR Designs: 8 Leading Small Modular Reactors Compared

Step-by-Step Guide

1. 1

   Understand the SMR Concept

   SMRs are designed to solve the key problems of traditional nuclear: high capital cost, long construction times, and large project risk. By building modules in a factory and shipping them to site, SMRs aim to reduce construction to 3 years and capital cost to under $3,000/kW.

2. 2

   Compare Light Water SMRs

   LWR-based SMRs use the same proven technology as current reactors but at smaller scale. NuScale VOYGR (77 MW/module, NRC-certified), GE Hitachi BWRX-300 (300 MW, under NRC review), and Rolls-Royce SMR (470 MW, UK design). These have the lowest technology risk but also the lowest efficiency improvements.

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   Tip: NuScale is the first and only NRC-certified SMR design. This regulatory precedent benefits all subsequent SMR applications.
3. 3

   Evaluate Advanced Reactor SMRs

   Non-LWR SMRs use different coolants for improved safety and efficiency: High-Temperature Gas Reactors (HTGR) — helium-cooled, graphite-moderated, 950°C outlet (X-energy Xe-100). Sodium-Cooled Fast Reactors (SFR) — liquid sodium, no moderator, breeder capable (TerraPower Natrium). Molten Salt Reactors (MSR) — fuel dissolved in molten salt, online refueling (Kairos Hermes).

4. 4

   Analyze Coolant Trade-offs

   Each coolant has advantages: Water — proven, abundant, but limited to ~320°C. Helium — inert, high temperature, but high-pressure system. Sodium — excellent heat transfer, low pressure, but reacts violently with water/air. Molten salt — low pressure, high temperature, but corrosive.

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   Warning: Sodium-cooled reactors require an intermediate sodium loop to prevent sodium-water reactions. This adds cost and complexity.
5. 5

   Understand Fuel Design Differences

   SMR fuels vary significantly: LWR SMRs use standard UO2 pellets in zirconium cladding (5% enrichment). HTGRs use TRISO particles — uranium kernels coated in carbon/silicon carbide layers (15% enrichment). SFRs use metallic or nitride fuel (15-20% enrichment). MSRs dissolve fuel directly in the salt coolant.

   

6. 6

   Evaluate Passive Safety Systems

   SMRs rely on passive safety — no active pumps or power needed for emergency cooling. NuScale uses natural circulation and gravity-driven emergency cooling. TerraPower Natrium uses pool-type sodium with large thermal inertia. X-energy Xe-100 uses TRISO fuel that cannot melt in conceivable accidents and natural convection for decay heat removal.

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   Tip: TRISO fuel is the most robust fuel form — it retains fission products up to 1,600°C without failure, making meltdown physically impossible.
7. 7

   Assess Economics and Deployment

   SMR economics depend on factory learning curves. First-of-a-kind (FOAK) costs are high ($8,000-12,000/kW), but nth-of-a-kind (NOAK) costs target $3,000-4,000/kW. The key challenge: you need to build many units to reach NOAK costs, but the first units are expensive.

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   SMR Cost Projections:
   FOAK (1st unit):  $8,000-12,000/kW
   Module 5-10:      $5,000-7,000/kW
   NOAK (20+):       $3,000-4,000/kW
   Target LCOE:      $40-60/MWh

8. 8

   Review Regulatory Status

   NRC certification status: NuScale VOYGR — certified (2026). GE Hitachi BWRX-300 — under review (decision expected 2027). TerraPower Natrium — construction permit application filed. X-energy Xe-100 — under pre-application review. Oklo Aurora — site permit received, COL under review.

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   Warning: NRC licensing for non-LWR designs takes longer because the review process was designed for light water reactors. The NRC is developing risk-informed pathways for advanced reactors.
9. 9

   Understand the HALEU Supply Challenge

   Most advanced SMRs require HALEU fuel (5-20% enrichment), which is not commercially available in the US. Current US enrichment capacity only produces LEU (up to 5%). The DOE is funding HALEU demonstration production, but a commercial supply chain is 3-5 years away.

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   Tip: The HALEU supply chain is the single biggest bottleneck for advanced reactor deployment. Without domestic HALEU, US SMR companies must rely on foreign suppliers.
10. 10

    Plan Your SMR Evaluation

    When evaluating SMRs for your use case, consider: Technology maturity (TRL level), regulatory status, fuel availability, cost projections, siting requirements, and operational workforce. For near-term deployment (before 2030), LWR-based SMRs are the only realistic option. For 2030+, advanced designs become viable.

11. 11

    Consider Hybrid Energy Systems

    SMRs excel in hybrid configurations — providing baseload power while integrating with renewables and storage. TerraPower Natrium includes integrated molten salt energy storage (500 MWh), enabling load following. SMRs can also provide industrial heat for hydrogen production, desalination, or chemical processing.