PWR-20
About
The PWR-20 is a 20 MWe microreactor with standard–assay LEU fuel. It operates at approximately 300 degrees Celsius and can be used for electricity production or cogeneration, in the form of desalination or district heating.
| Developer | Last Energy |
|---|---|
| Country of Origin | United States |
| Size | Micro |
| Type | Pressurized Water Reactor (PWR) |
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Analysis
4
Deployment Timescale
Score Justification
The U.K. Office for Nuclear Regulation has completed a Preliminary Design Review for the PWR-20, and Last Energy plans to pursue a site license by December 2027. The design emphasizes a high degree of modularity and limits the use of specialized exotic materials, which is intended to support more streamlined construction and deployment.
By indicator
- 2/4 Regulatory Engagement
To what extent has the reactor developer engaged with a recognized nuclear regulatory authority in the licensing process? (30% of total score) - 4/6 Technology Precedent
Has the reactor design, or a sufficiently similar design, been certified anywhere in the world? (10% of total score) - 3/3 Modularity
What share of total reactor systems can be manufactured off-site in controlled factory environments rather than constructed on-site? (15% of total score) - 4/4 Specialization
To what extent do construction activities and components require lengthy qualification processes? (15% of total score) - 5/5 Supply Chain
How mature and available are suppliers for key reactor components and fuel services? (30% of total score)
5
Overnight Cost
Score Justification
The PWR-20’s small unit size, modular construction approach, and limited reliance on exotic components with lengthy qualification processes contribute to a relatively low overnight cost profile.
By indicator
- 4/4 Component Cost
What is the expected cost of the reactor’s major components? (40% of total score) - 6/6 Construction Cost
To what extent does the design reduce construction cost and risk through modular fabrication and limited nuclear-grade specialization? (60% of total score)
5
Operational Cost
Score Justification
Operational Cost for the PWR-20 benefits from the use of conventional LWR fuel and operating practices. The sealed, long-cycle core eliminates routine refueling outages and fuel shuffling, reducing staffing and outage-driven maintenance demands, while the absence of large on-site construction and complex auxiliary systems supports lower maintenance and decommissioning costs relative to traditional large LWRs.
By indicator
- 3/3 Fuel Cost
What is the estimated cost of nuclear fuel per unit of electricity generated, including enrichment, fabrication, and back-end costs? (15% of total score) - 4/4 Maintenance Cost
What is the expected annual maintenance cost for the reactor and balance of plant systems, including consumables? (25% of total score) - 5/5 Staffing Level
How many full-time personnel are required to safely operate and maintain the reactor unit? (40% of total score) - 4/5 Spent Fuel & Radioactive Waste Management Cost
What are the expected operational costs associated with managing spent fuel, including interim storage, transport, disposal, or recycling? (10% of total score) - 5/5 Decommissioning Cost
What are the total lifetime contributions required for decommissioning, regardless of funding mechanism? (10% of total score)
2
Cost Predictability
Score Justification
The PWR-20 incorporates modular construction features intended to support repeatability. The absence of an operating prototype limits near-term confidence in cost estimates, however a prototype is being planned under the U.S. Reactor Pilot Program.
By indicator
- 0/5 Prototype
To what extent has the reactor design been built, demonstrated, or commercially deployed in practice? (75% of total score) - 3/3 Modularity
What share of total reactor systems can be manufactured off-site in controlled factory environments rather than constructed on-site? (25% of total score)
5
Security
Score Justification
As an LWR, the PWR-20 is not optimized to produce weapons-usable nuclear material because it is on a thermal spectrum and has a high burnup rate. The design incorporates security-by-design measures, including a sealed reactor configuration that limits on-site access to nuclear material and reduces opportunities for diversion.
By indicator
- 3/3 Fuel
What is the enrichment level and composition of the reactor fuel? (40% of total score) - 4/4 Nuclear Material Production
What is the potential for the reactor to produce weapons-usable nuclear material? (40% of total score) - 1/1 Security by Design
Has the reactor developer built in security by design? (20% of total score)
3
Safety
Score Justification
The PWR-20 uses conventional UO₂ fuel, which is well understood but is not considered inherently accident tolerant. The reactor operates at high pressure and relies on a single containment structure. Like most reactors, it benefits from negative reactivity feedback and includes an independent active shutdown system with sensor-activated control rods.
By indicator
- 1/2 Safety Case
How mature and publicly established is the reactor’s safety case with the regulator? (40% of total score) - 1/2 Shutdown Mechanism
How diverse, independent, and passive are the reactor’s shutdown systems? (20% of total score) - 0/1 Fuel With Safety Characteristics
Does the reactor use fuel with accident tolerance or inherent safety characteristics? (10% of total score) - 1/4 Pressure & Containment
How well does the reactor’s containment strategy protect from the release of radioactive material? (10% of total score) - 3/3 Passive Heat Removal
How long can the reactor remove core heat without operator intervention? (10% of total score) - 3/4 Coolant Reactivity
How chemically reactive is the reactor coolant? (10% of total score)
4
Spent Fuel & Radioactive Waste Management
Score Justification
The PWR-20 uses standard-assay LEU UO₂ fuel, which has been licensed and qualified for disposal in multiple countries. This familiar spent fuel form can usually be transferred to interim storage within five years. The reactor does not introduce novel waste streams that require separate treatment and handling beyond past practice.
By indicator
- 1/1 Spent Fuel Licensing Precedent
Has the spent fuel form been previously licensed for disposal? (20% of total score) - 4/4 Waste Streams
How many distinct waste streams require separate conditioning or handling pathways? (20% of total score) - 3/3 On-Site Storage
How much on-site area is required for interim spent fuel storage? (10% of total score) - 2/3 Spent Fuel Volume
What volume of spent fuel is produced per unit of electricity generated? (15% of total score) - 1/2 Decay Heat
What is the decay heat output of spent fuel at the 50-year interim storage milestone? (20% of total score) - 2/2 Time to Interim Storage
What is the average time until spent fuel can be transferred to interim storage? (15% of total score)
5
Supply Chain
Score Justification
Because the PWR-20 is based on conventional LWR technology, it can draw on an established global supply chain for fuel, components, and services.
By indicator
- 2/2 Key Component Availability
To what extent are commercial or pilot-scale suppliers available for the reactor’s major components? (60% of total score) - 4/4 Fuel Availability
Are suppliers available for both fuel fabrication and enrichment required by the reactor design? (40% of total score)