HTR-PM
About
The HTR-PM (High‑Temperature Reactor-Pebble‑Bed Module) is the world’s first commercial modular HTGR, having entered commercial operation in December 2023. It uses 8.5% enriched TRISO fuel, helium gas coolant, and a graphite moderator. It puts out 105 MWe per module, for a total of 210 MWe. The HTR-PM operates at 750 degrees Celsius, making it well suited for high process heat applications like hydrogen production, oil refining, desalination, district heating, and food and textile processing, in addition to modular electricity production.
| Developer | China National Nuclear Company (CNNC) |
|---|---|
| Country of Origin | China |
| Size | Small |
| Type | High-Temperature Gas-Cooled Reactor (HTGR) |
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Analysis
4
Deployment Timescale
Score Justification
The HTR-PM benefits from being operational and relatively modular, supporting deployment timelines through learning and repeat construction. Deployment is constrained by specialized supply chains, including TRISO fuel, helium systems, and continuous fuel handling.
By indicator
- 4/4 Regulatory Engagement
To what extent has the reactor developer engaged with a recognized nuclear regulatory authority in the licensing process? (30% of total score) - 6/6 Technology Precedent
Has the reactor design, or a sufficiently similar design, been certified anywhere in the world? (10% of total score) - 2/3 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) - 3/4 Specialization
To what extent do construction activities and components require lengthy qualification processes? (15% of total score) - 2/5 Supply Chain
How mature and available are suppliers for key reactor components and fuel services? (30% of total score)
4
Overnight Cost
Score Justification
As an SMR, the HTR-PM’s component costs are constrained by its smaller footprint though they are still influenced by the need for specialized helium machinery and nuclear graphite. Its construction costs benefit from a largely modular design, yet the plant still requires supporting balance‑of‑plant systems that contribute to overall civil engineering expenditures.
By indicator
- 3/4 Component Cost
What is the expected cost of the reactor’s major components? (40% of total score) - 4/6 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)
3
Operational Cost
Score Justification
The HTR-PM’s operational costs are moderate and include maintenance costs for helium circulators and purifiers. The HTR-PM uses TRISO fuel, which is is more expensive to fabricate than traditional LWR fuel. However, the plant’s staffing and decommissioning costs are lower than large LWRs because it avoids large water and steam systems and uses helium coolant that does not become activated or contaminated.
By indicator
- 1/3 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) - 3/4 Maintenance Cost
What is the expected annual maintenance cost for the reactor and balance of plant systems, including consumables? (25% of total score) - 4/5 Staffing Level
How many full-time personnel are required to safely operate and maintain the reactor unit? (40% of total score) - 3/5 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)
3
Cost Predictability
Score Justification
The HTR-PM’s overnight cost estimates are moderately predictable after the construction of the first-of-a-kind unit. Its modularity helps improve cost predictability, as will the construction and operation of more units.
By indicator
- 3/5 Prototype
To what extent has the reactor design been built, demonstrated, or commercially deployed in practice? (75% of total score) - 2/3 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
The HTR-PM uses LEU fuel. It is not optimized to produce weapons-usable nuclear material because of its thermal spectrum. As the first commercially operational pebble-bed reactor, the HTR-PM set a standard of security by design by ensuring that monitoring systems are embedded in its fuel handling architecture. More research is necessary to account for such a novel online bulk refueling challenge, but CNNC has taken steps to begin the process.
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)
5
Safety
Score Justification
The HTR-PM sets a strong safety standard by incorporating TRISO fuel, chemically inert coolant, and relatively low operating pressure. The reactor has multiple independent shutdown systems, including active control rods, and a gravity-driven absorber ball system. The HTR‑PM can passively remove decay heat indefinitely without operator action or external power because of its reactor cavity cooling system and the inherent safety of TRISO fuel.
By indicator
- 2/2 Safety Case
How mature and publicly established is the reactor’s safety case with the regulator? (40% of total score) - 2/2 Shutdown Mechanism
How diverse, independent, and passive are the reactor’s shutdown systems? (20% of total score) - 1/1 Fuel With Safety Characteristics
Does the reactor use fuel with accident tolerance or inherent safety characteristics? (10% of total score) - 2/4 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) - 4/4 Coolant Reactivity
How chemically reactive is the reactor coolant? (10% of total score)
3
Spent Fuel & Radioactive Waste Management
Score Justification
The HTR-PM’s modular canister system reduces on-site storage requirements, but its graphite moderator creates an extra waste stream to manage. The licensing pathway for the HTR-PM’s TRISO fuel is underway but not complete. TRISO fuel results in higher spent fuel volume per unit of energy than LWRs; however, it retains relatively low volumetric decay heat at long cooling times, which is a significant driver of storage, transportation, and disposal.
By indicator
- 0/1 Spent Fuel Licensing Precedent
Has the spent fuel form been previously licensed for disposal? (20% of total score) - 3/4 Waste Streams
How many distinct waste streams require separate conditioning or handling pathways? (20% of total score) - 2/3 On-Site Storage
How much on-site area is required for interim spent fuel storage? (10% of total score) - 1/3 Spent Fuel Volume
What volume of spent fuel is produced per unit of electricity generated? (15% of total score) - 2/2 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)
2
Supply Chain
Score Justification
The HTR-PM has a single commercial supplier for both its fuel enrichment and fabrication, each of which is domestic and specific to the design. It has multiple commercial suppliers for most of its other major components, although the supply chain for its helium components is not as well-developed.
By indicator
- 1/2 Key Component Availability
To what extent are commercial or pilot-scale suppliers available for the reactor’s major components? (60% of total score) - 3/4 Fuel Availability
Are suppliers available for both fuel fabrication and enrichment required by the reactor design? (40% of total score)