Castellan Defense Systems
Castellan Defense Systems
Senior notes on a transportable gas-cooled microreactor under a defense prototyping contract. Accredited only.
Roughly half of the casualties in recent land campaigns occurred in or around fuel convoys. A three megawatt reactor that fits in shipping containers and runs for five years without refueling removes that convoy. Castellan holds a construction permit under Department of Energy authorization and a prototyping contract with options for eight units.
$24,900,000 committed of $30,000,000
$17,430,000 released · 83% subscribed
- Minimum
- $25,000
- Target coupon
- 7.15%
- Term
- 6 yr
- Investors
- 88
$1,000 per unit
Annual, fixed
Closes November 15, 2026 · 63 days remaining
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TRL assessment
7
Technology readiness level, 1 to 9
Confidence band 6.6 – 7.5
A construction permit is issued under Department of Energy authorization and a prototype is in fabrication, which is a system prototype heading into an operational environment. High-temperature gas reactors with TRISO fuel have the strongest safety evidence base of any advanced design. The commercial risk is single-customer concentration and options that are not orders.
At TRL 7, the ladder permits Senior note and releases up to 70% of committed capital. This offering is structured as a senior note, which is consistent with that band.
Signed and published
- Reviewer
- Dr. Helena Vargas-Mbeki
- Credential
- PE, Nuclear; former NRC senior reactor analyst
- Signed
- June 4, 2026
- Published
- June 5, 2026
- Methodology
- v1.4
- Model
- ci-trl-2026.06
- Generated
- May 30, 2026
Evidence
Every score cites the documents it was derived from, with the weight each carried. An assessment without evidence is an opinion.
| Source | Document | Date | Weight |
|---|---|---|---|
| NRC docket | Construction authorization issued under DOE authority DOE authorization basis approval Authorizes construction and operation of the prototype unit. | Nov 13, 2025 | 32% |
| National lab result | TRISO fuel qualification data, full burnup Advanced test reactor campaign, final report Fission product retention maintained to design burnup with margin. | Jun 30, 2025 | 30% |
| Supplier contract | Defense prototyping contract with unit options Executed contract, options for eight units Options exercisable at government discretion and not committed volume. | Jan 8, 2026 | 24% |
| Independent test report | Transportability and shock qualification Independent test report to defense transport standards Containerised unit met road and air transport shock requirements. | Apr 16, 2026 | 14% |
Score history
A score changes on the day a reviewer signs a new assessment, which is why this is a step line rather than a curve.