Ward 250 (HTGR Demonstration Reactor) by Valar Atomics: status and timeline

Ward 250 (HTGR Demonstration Reactor)

Ward 250 is a demonstration high-temperature gas reactor that reached criticality in June 2026. It uses TRISO fuel and helium cooling to achieve temperatures above 700°C for industrial heat and power.

PilotStage 3 of 5

Reached zero-power criticality June 2026. In power ascension testing in Utah.

Updated 18 Jun 2026Checked 10 Oct0 updates this week

Milestones

Next · Power ascension testing

Reactor delivered to Utah siteFeb 2026Complete.
Zero-power criticality achievedJun 2026Complete.
Power ascension testingTarget Q4 2026Current milestone.
Full operational thermal testingTarget 2027Not yet reached.

Most important updates

Upcoming

Q4 2026Power ascension testing (next)
2027Full operational thermal testing
2027Industrial heat demonstration with customer

Current obstacles

TRISO fuel qualificationTRISO fuel irradiation testing is ongoing to fully qualify the fuel for commercial deployments. Burnup and performance data are still being gathered.
Helium production and containmentHelium supplies are limited and expensive; long-term cost and supply security must be demonstrated for commercial viability.

Physics limits

Material limits at high temperatureMetallic structures in the reactor degrade at very high temperatures. Ceramic and refractory materials are necessary but more brittle and harder to fabricate.
Industrial heat market depthThe addressable market for heat above 700°C is smaller than for electricity. Growth depends on expanding hydrogen production and advanced chemical processes.

How it works

2 parts

Core

TRISO fuel in graphite

The core is graphite embedded with TRISO fuel particles. Each particle survives temperatures above 1200°C.

Heat transfer

Helium circulation

Helium heated to 750°C flows to industrial processes. High temperature enables hydrogen production and chemical processing.

Spec sheet

Spec	Ward 250 (HTGR Demonstration Reactor)
Outlet temperature	750°C+^R (reported)
Fuel type	TRISO (tristructural isotropic)^R (reported)
Coolant	Helium gas^R (reported)

^R reported by the company

Update log

2 updates

Thu 18 Jun

Major: Valar Atomics Ward 250 achieves zero-power criticality, becoming second DOE reactor pilot to reach the milestonePressTest

Sun 15 Feb

Major: US military airlifts Valar Atomics Ward 250 reactor to Utah in historic first nuclear transportPressHardware

About Valar Atomics

The team behind Ward 250 (HTGR Demonstration Reactor)

Valar Atomics

High-temperature gas reactor, industrial heat, HTGR, TRISO fuel

Valar Atomics develops high-temperature gas reactors (HTGR) designed for industrial heat and power applications. The company is building Ward 250, a demonstration reactor using TRISO fuel and helium cooling, as part of the DOE's advanced reactor pilot program.

Valar Atomics reached zero-power criticality with Ward 250 in June 2026, one of four companies in the DOE pilot program.
The HTGR design uses TRISO fuel (tristructural isotropic) and helium cooling, enabling higher temperatures and industrial heat applications.
Ward 250 is located in Utah and is part of a national initiative to demonstrate next-generation nuclear technology.

valaratomics.com (opens valaratomics.com)Company profile →

Headquarters: United States
Status: Private
Valuation: private
Works in: EnergyFission
Coverage: 1 program · 2 updateslatest 18 Jun 2026checked 10 Oct
Partners: U.S. Department of EnergyState of UtahUtah San Rafael Energy Lab

Spec

Ward 250 (HTGR Demonstration Reactor)

Outlet temperature

750°C+^R (reported)

Fuel type

TRISO (tristructural isotropic)^R (reported)

Coolant

Helium gas^R (reported)