Two Companies Reach Criticality in U.S. Experimental Nuclear Reactor Program

Two companies have reached criticality in the U.S. experimental nuclear reactor program established under President Trump. Antares Nuclear announced it had gone critical on June 4. Valar Atomics followed on June 18 and is now producing tens of kilowatts of heat from its reactor core operating out of a tentlike structure in the Utah desert.

Npr reported that President Trump set the goal of at least three new experimental nuclear reactors by July 4, 2026, the 250th anniversary of the Declaration of Independence. He signed an executive order establishing the target, after which the Department of Energy launched the Reactor Pilot Program. The program has allowed companies to build and test reactors on an accelerated timeline.

Radiant is assembling its reactor inside the DOME building at Idaho National Laboratory. Rita Baranwal, the firm's chief nuclear officer, said the company is tracking to get the reactor into the DOME and initiate testing by July 4. She added that Radiant does not expect the reactor to be critical by the deadline and will not generate electricity at the laboratory this summer.

Radiant's design uses small nuclear fuel balls filled with grains of uranium. Baranwal compared them to gobstoppers and noted they can operate at higher temperatures. The company has broken ground on a factory targeting production of around 50 reactors per year.

Currently 96 reactors operate in the United States. The Energy Department rewrote its safety and security standards for the program this year and exempted the reactors from environmental reviews. Npr reported that the department consulted with the companies but not with the public on the changes.