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title: "Small Modular Reactors (SMRs)" description: The next generation of nuclear power — factory-built, scalable reactors designed to be safer, faster to deploy, and more economically flexible than conventional plants. summary: The next generation of nuclear power — factory-built, scalable reactors designed to be safer, faster to deploy, and more economically flexible than conventional plants. category: nuclear difficulty: Advanced updated: 2026-02-10 tags: ["nuclear", "SMR", "small modular reactor", "advanced nuclear", "clean energy", "technology"] relatedTools: [] faqs:

• question: What is a small modular reactor? answer: An SMR is a nuclear reactor with electrical output under 300 MW (compared to 1,000+ MW for conventional reactors). The key innovation is factory fabrication — major components are built in a factory and shipped to the site, reducing construction risk, time, and cost compared to building everything on-site.
• question: Are SMRs safer than conventional nuclear plants? answer: SMRs incorporate passive safety systems that rely on natural physical processes (gravity, convection, radiation) rather than pumps and human action. Many designs physically cannot melt down because they self-regulate as temperature increases. However, they still produce nuclear waste and require security and regulatory oversight.
• question: When will SMRs be available? answer: NuScale received NRC design certification in 2023 — the first SMR certified in the U.S. TerraPower's Natrium reactor is under construction in Wyoming. Several more are in NRC review. The first commercial SMR electricity in the U.S. is expected in the late 2020s, with broader deployment in the 2030s.
• question: How much will SMR electricity cost? answer: First-of-a-kind SMR electricity may cost $60-$100/MWh — competitive with gas but above wind and solar. Proponents project costs dropping to $40-$60/MWh with serial production (building multiple identical units). This remains unproven commercially and depends on achieving factory-like manufacturing scale.

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Small Modular Reactors (SMRs)

Small modular reactors represent the most significant new direction in nuclear energy — designed to address the cost overruns, long construction timelines, and inflexibility that have plagued conventional large nuclear plants.

What Makes an SMR

| Feature | Conventional Reactor | Small Modular Reactor | |---------|:-:|:-:| | Electrical output | 1,000-1,400 MW | 20-300 MW | | Construction | On-site ("stick-built") | Factory-fabricated, site-assembled | | Construction time | 7-15+ years | Target: 3-5 years | | Capital cost | $8-$16 billion per unit | Target: $1-$3 billion per unit | | Site area | 1-2 square miles | 10-50 acres | | Cooling | Active cooling systems | Many use passive cooling | | Refueling | Every 18-24 months | Varies: 2-20 years |

The "Modular" Advantage

The key economic thesis: by making reactors small enough to be factory-built, you can:

1. Shift construction to controlled factory environments (better quality, lower labor costs, weather-independent)
2. Build nth-of-a-kind units that benefit from learning curves (each unit cheaper than the last)
3. Scale capacity incrementally by adding modules as demand grows (rather than committing to a massive single unit)
4. Standardize designs to reduce engineering costs and simplify licensing

Leading U.S. SMR Designs

NuScale VOYGR (Light Water)

• Type: Pressurized light water reactor (familiar technology)
• Capacity: 77 MW per module; up to 12 modules per plant (924 MW)
• Status: NRC design certification received January 2023 — first-ever SMR certification in the U.S.
• Key feature: Modules sit in a shared pool; natural circulation cooling eliminates pumps
• Passive safety: Self-cooling for 30+ days without operator action or external power
• Deployment: First U.S. commercial deployment timeline being reassessed after UAMPS project cancellation; international projects advancing

TerraPower Natrium (Sodium-Cooled Fast Reactor)

• Type: Sodium-cooled, fast neutron reactor with molten salt energy storage
• Capacity: 345 MW (can boost to 500 MW for 5.5 hours using thermal storage)
• Status: Under construction in Kemmerer, Wyoming (at a former coal plant site)
• Key feature: Integrated thermal storage allows output flexibility — valuable for grids with variable renewables
• Backed by: Bill Gates (founder of TerraPower); DOE cost-share through ARDP
• Timeline: Target operation by late 2020s

X-energy Xe-100 (High-Temperature Gas Reactor)

• Type: High-temperature gas reactor using TRISO fuel pebbles
• Capacity: 80 MW per module; 4-pack configuration = 320 MW
• Status: Under NRC review; DOW Chemical partnership for industrial heat
• Key feature: TRISO fuel particles are individually enclosed in ceramic shells — they cannot melt even at extreme temperatures
• Applications: Both electricity and industrial process heat (up to 750°C) — useful for chemical manufacturing, desalination, and hydrogen production

GE-Hitachi BWRX-300 (Boiling Water)

• Type: Simplified boiling water reactor
• Capacity: 300 MW
• Status: Under NRC review; TVA selected Clinch River, TN for potential first unit
• Key feature: Simplified design reduces cost and construction time vs. larger BWRs
• International: Ontario Power Generation (Canada) proceeding with deployment

Kairos Power Hermes (Fluoride Salt-Cooled)

• Type: Fluoride salt-cooled reactor with TRISO fuel
• Capacity: Hermes test reactor (35 MW thermal, non-power); Hermes 2 (140 MW power)
• Status: Construction permit received 2023 for test reactor in Oak Ridge, TN
• Key feature: Low-pressure operation (atmospheric vs. 2,250 psi for PWRs) simplifies containment and reduces costs

The Economics Challenge

Cost Projections vs. Reality

| Scenario | Projected LCOE ($/MWh) | |----------|:-:| | First-of-a-kind SMR | $60-$100 | | Nth-of-a-kind (after 10+ units) | $40-$60 | | New utility-scale solar (for comparison) | $25-$50 | | New onshore wind | $25-$55 | | New natural gas CCGT | $40-$75 |

The core question: Can serial production drive costs down to projected levels? Large conventional reactors have historically seen costs increase over time in Western countries (the opposite of the learning curve). SMR proponents argue factory fabrication fundamentally changes this dynamic, but it's unproven at commercial scale.

Federal Support

The Department of Energy is heavily investing in SMR development:

• Advanced Reactor Demonstration Program (ARDP): $3.2 billion for TerraPower Natrium and X-energy Xe-100
• SMR Licensing Technical Support: Cost-shared NRC licensing assistance
• IRA incentives: 45Y PTC and 48E ITC available for all new zero-emission generation, including SMRs
• HALEU availability: DOE working to ensure supply of high-assay low-enriched uranium (HALEU) fuel needed by several advanced designs

Potential Applications Beyond Electricity

Industrial Heat

Many industrial processes require high temperatures that can't be easily electrified:

| Application | Temperature Needed | SMR Potential | |------------|:-:|:-:| | Hydrogen production | 700-900°C | High-temperature gas reactors | | Desalination | 70-120°C | All SMR types | | Chemical processing | 300-600°C | HTGRs, molten salt reactors | | District heating | 80-150°C | All SMR types | | Data center power | N/A (electricity) | All SMR types |

Remote and Off-Grid Power

Micro-reactors (1-20 MW) are being developed for:

• Military installations
• Remote mining operations
• Arctic and island communities
• Space applications

Project Pele (DOE/DoD) is developing a transportable micro-reactor for military use.

Challenges and Concerns

Technical

• First-of-a-kind risk: No commercial SMR has yet generated electricity in the U.S.
• Fuel supply: Several designs require HALEU (5-20% enriched), which is currently scarce and dependent on Russian enrichment capacity
• Waste: SMRs still produce nuclear waste; some designs produce more waste per kWh than conventional reactors due to higher neutron leakage
• Cooling water: Some designs (like NuScale) still require cooling water; others (Xe-100, KP-FHR) need much less

Economic

• Unproven cost at scale: Factory cost reductions remain theoretical until multiple units are built
• Competition: Solar and wind LCOE continue to decline; battery costs are falling 10-15%/year
• Financing: Nuclear projects carry high upfront capital risk that increases cost of capital

Regulatory

• NRC review timeline: Design certification takes 3-7+ years
• Fuel cycle regulation: HALEU handling requires new security and safeguards infrastructure
• Site licensing: Each deployment site requires NRC approval

What SMRs Mean for the Energy System

If SMRs achieve their cost and deployment targets, they could:

1. Provide firm, 24/7 clean power that complements variable wind and solar — reducing the need for seasonal-scale energy storage
2. Replace retiring coal and gas plants at existing sites (with grid connections already in place)
3. Decarbonize industrial heat that can't be electrified
4. Enhance grid resilience with distributed, dispatchable clean generation
5. Support data center growth with on-site reliable power

The next 5-10 years will determine whether SMRs can transition from promising prototypes to commercially competitive energy sources.