IMSR (Integral Molten Salt Reactor)
IMSR (Integral Molten Salt Reactor) is a molten fluoride salt-cooled reactor design rated at 195 MWe. The developer is engaging a regulator but has not submitted an application. It requires HALEU fuel.
Terrestrial Energy would need to file a construction permit application, and a first-of-a-kind molten salt reactor would need to demonstrate that its corrosion and fuel-salt chemistry behave over years, not months. No commercial MSR has ever operated.
Approved topical reports are real regulatory progress and are often reported as if they were approval of the reactor. They are not: they settle methodology questions in advance of an application that has not yet been made.
| Tier | Pre-application |
|---|---|
| Regulator | US NRC and CNSC (Canada) |
| Application type | Topical reports; pre-application |
| Docket / reference | NRC approved IMSR Principal Design Criteria topical report (2025) and Postulated Initiating Event methodology (2026) |
| Application date | - |
| Review phase | Topical reports approved; no licence application submitted |
| Decision expected | not stated |
| Coolant | Molten fluoride salt |
|---|---|
| Reactor family | Molten salt reactor (MSR) |
| Electrical output | 195MWe |
| Thermal output | not disclosed |
| Fuel | Uranium fuel dissolved in salt |
| Enrichment | HALEU |
| First site | none announced |
| Offtakers | none announced |
This design needs HALEU, uranium enriched above 5% and below 20%. That is not the fuel any commercial Western power reactor uses today, and it is the single most common reason an advanced reactor timeline slips. Every Western facility that can make it or turn it into fuel:
| Facility | Capacity | Status |
|---|---|---|
| TRISO-X Fuel Facility (TX-1), Oak Ridge | not disclosed | construction |
| American Centrifuge Plant, Piketon | 900kg HALEU/yr | operating |
| Idaho National Laboratory EBR-II downblending | not disclosed | operating |
| Nuclear Fuel Services, Erwin | not disclosed | operating |
| Savannah River Site HEU downblending | 3,100kg HALEU total | operating |
| BWXT TRISO facility, Gillette | not disclosed | planned |
| General Matter | not disclosed | planned |
| Urenco Capenhurst HALEU line | not disclosed | planned |
Sources
- Terrestrial Energy SEC filings · retrieved 2026-09-06
How these sources are used, including the corrections applied on top of them and what is deliberately left blank · download the underlying data