Small Modular Reactor (SMR) Technology
Small Modular Reactors represent the most significant innovation in nuclear power generation since the first commercial reactors of the 1950s and 60s. By reimagining reactor design around factory manufacturing, modularity, and inherent passive safety, SMRs address the primary barriers that have limited large-scale nuclear deployment: cost overruns, construction timelines, and site-specific complexity.
What Is a Small Modular Reactor?
A Small Modular Reactor is a nuclear fission reactor with an output capacity of up to 300 MW per module — compared to 1,000–1,600 MW for conventional large reactors. The defining characteristic is that the reactor, steam generators, pressurizer, and primary coolant pumps are all contained within a single integrated pressure vessel that can be manufactured entirely in a factory and shipped by rail or truck to the installation site.
This factory-manufacturing approach enables standardized quality control, eliminates most on-site construction complexity, and creates economies of scale as more units are produced. Multiple modules can be combined at a single site to achieve larger total output, providing both scalability and redundancy.
SMR vs. Traditional Large Reactor: Key Differences
| Feature | Small Modular Reactor (SMR) | Traditional Large Reactor |
|---|---|---|
| Power Output | 50–300 MW per module | 1,000–1,600 MW per reactor |
| Construction Method | Factory-built, assembled on-site | Predominantly on-site construction |
| Construction Timeline | 3–5 years | 10–15+ years |
| Upfront Capital Cost | $500M–$2B per module | $8B–$15B per plant |
| Levelized Cost of Energy | $50–$100/MWh (projected at scale) | $90–$200/MWh (recent US projects) |
| Site Requirements | Smaller footprint; flexible siting | Large dedicated exclusion zone |
| Staffing Requirements | Fewer operators; remote monitoring possible | Large specialized workforce on-site |
| Safety Systems | Passive; gravity and convection-driven | Active; requires pumps and power |
| Scalability | Add modules incrementally | All-or-nothing investment |
| Load Following | Capable; some designs can vary output | Typically baseload only |
| Fuel | Low-enriched uranium; some advanced designs use HALEU | Low-enriched uranium (2–5%) |
| Cooling Medium | Water, sodium, gas, or molten salt (design-dependent) | Water (light water reactors) |
Leading SMR Developers
NuScale Power (SMR)
Oregon-based NuScale received the first-ever NRC design certification for a light water SMR in 2022. Its 77 MW VOYGR modules use natural circulation cooling with no pumps required. NuScale is targeting utility customers in the US and internationally. Publicly traded as ticker SMR.
TerraPower (Natrium)
Founded by Bill Gates, TerraPower is building the Natrium sodium-cooled fast reactor at Kemmerer, Wyoming — the first US advanced reactor under construction. The 345 MW plant uses molten salt thermal storage for flexible output up to 500 MW. Expected operational around 2030.
Oklo Inc. (OKLO)
Sam Altman-backed Oklo is developing the Aurora microreactor (15 MW), a compact sodium fast reactor that can use recycled nuclear fuel. Oklo has signed letters of intent with multiple data center operators and military facilities. Publicly traded as ticker OKLO.
X-energy
X-energy's Xe-100 is a 80 MW high-temperature gas-cooled pebble bed reactor designed for industrial heat and electricity. TRISO fuel pebbles provide exceptional passive safety. Dow Chemical and Amazon are early customers. Construction planned for Texas and Washington state.
Kairos Power
Kairos is developing a fluoride salt-cooled high-temperature reactor (FHR) using TRISO pebble fuel in a molten salt coolant. Google signed a landmark agreement to purchase 500 MW from multiple Kairos plants starting in 2030. The company is building a demonstration reactor (Hermes) in Tennessee.
Westinghouse AP300
Westinghouse scaled down its proven AP1000 large reactor design to create the 300 MW AP300 SMR. By leveraging the existing AP1000 regulatory approval, NRC review time is expected to be significantly reduced. Czech, Poland, and US utilities have expressed interest.
BWX Technologies (BWXT)
BWXT manufactures nuclear reactor components for both commercial utilities and the US Navy. The company is developing microreactors for remote communities and military bases through its BANR (BWXT Advanced Nuclear Reactor) program. BWXT also supplies fuel and components to multiple SMR developers. Publicly traded as ticker BWXT.
Last Energy
Last Energy is commercializing 20 MW PWR micro-reactors that can be deployed on a modular, standardized basis using existing nuclear codes and standards. The company has signed agreements with multiple European data center operators seeking nuclear-powered campuses.
SMR Deployment Timeline
SMR Safety Features
Modern SMR designs incorporate passive safety systems that represent a fundamental improvement over both early commercial reactors and even many of today's large reactors. Passive safety means the reactor can shut down and remain safe indefinitely without any operator action, external electrical power, or active mechanical systems like pumps and valves.
| Safety Feature | How It Works | Benefit |
|---|---|---|
| Natural circulation cooling | Hot coolant rises, cooler coolant falls, creating continuous flow without pumps | Eliminates pump failure as an accident initiator |
| Integral reactor design | All primary components inside a single pressure vessel | Eliminates large-bore pipe connections that can fail |
| Negative void coefficient | Chain reaction slows automatically as water temperature rises | Physics-based self-limiting shutdown |
| Gravity-fed emergency cooling | Water tanks above reactor release by gravity on demand | No power or pumps required for emergency cooling |
| Underground siting | Reactor vessel placed below grade inside reinforced concrete | Protection from external events; heat sinks naturally into ground |
| TRISO fuel (some designs) | Fuel coated in ceramic layers that contain fission products | Fuel cannot melt even at extreme temperatures |
Economic Outlook for SMRs
The economic case for SMRs rests on several key assumptions: that factory manufacturing will drive down costs through standardization and learning curves; that shorter construction timelines will reduce financing costs; and that the elimination of large dedicated sites will expand the addressable market. Industry analysts project that the levelized cost of energy (LCOE) for SMRs could reach $60–75/MWh by the mid-2030s as production scales, making them cost-competitive with natural gas for always-on applications and dramatically cheaper than diesel or gas turbines for remote or islanded power needs.
The technology company power purchase agreements currently being signed — at prices reportedly in the range of $70–$150/MWh for guaranteed long-term clean power — suggest that the market is willing to pay a premium for the reliability and zero-carbon attributes that SMRs offer, providing a strong commercial foundation for first-of-a-kind deployments.