Sunday, 9 August 2026

Oklo Inc. said its Groves Isotope Test Reactor has reached first criticality, achieving a controlled, self-sustaining nuclear chain reaction at low power, according to Neutron Bytes.

The company, listed on the NYSE under the ticker OKLO, describes itself as an advanced nuclear technology developer.

Neutron Bytes reported that the criticality milestone came less than a year after groundbreaking on the project. The reactor operates under authorization from the U.S. Department of Energy granted through the DOE Reactor Pilot Program.

Groves is the first reactor under that program to achieve criticality on private land, according to Neutron Bytes. It was built from the ground up on a greenfield site.

Centrus Energy has signed a low-enriched uranium and high-assay low-enriched uranium fuel deal with X-energy, according to Neutron Bytes, one of several supply agreements now shaping the fuel chain for advanced reactor developers.

The designs behind those contracts require enrichment levels above the standard commercial grade. Neutron Bytes reports that X-energy's Xe-100 is built around 80 MWe high-temperature gas-cooled reactor modules using TRISO pebble fuel enriched to about 15.5% U235. TerraPower's Natrium design uses a 345 MWe sodium-cooled fast reactor with dense uranium metal fuel enriched to roughly 19.75% U235.

Fabrication capacity is moving in parallel with the contracts. X-energy and its wholly owned subsidiary TRISO-X began construction work on the TX-1 advanced nuclear fuel fabrication facility in Oak Ridge in November 2025, per Neutron Bytes.

The metal fuel route reached its own marker in the same month. Framatome and TerraPower produced successful elements of uranium metal, which Neutron Bytes describes as a key milestone in uranium metallization for advanced reactor fuel commercialization.

Other developers are working the regulatory track rather than the contract track. Newcleo filed a regulatory engagement plan with the NRC for a mixed-oxide fuel manufacturing facility, according to Neutron Bytes. A MOX plant would put recycled fissile material into the same supply picture as fresh enriched uranium.

Supply arrangements are also forming outside the HALEU segment. CCTE announced a nuclear fuel supply agreement with BWXT Canada, Neutron Bytes reported.

Taken together, the agreements pair reactor vendors with fuel suppliers at the point where enrichment specifications diverge sharply between designs. TRISO pebbles at about 15.5% U235 and uranium metal at about 19.75% U235 draw on different fabrication lines and different qualification paths. Both sit above the enrichment level of conventional light-water fuel, and both depend on facilities such as TX-1 reaching operation.

X-energy and Centrus have signed a definitive agreement under which Centrus will supply enrichment services for low-enriched uranium (LEU) and high-assay low-enriched uranium (HALEU), according to a GlobeNewswire release.

Centrus will enrich the HALEU at the American Centrifuge Plant in Piketon, Ohio, and the material will go to X-energy's fuel subsidiary TRISO-X, LLC for fabrication of TRISO-X coated particle fuel at the company's fuel fabrication campus in Oak Ridge, Tennessee.

That fuel is the core of the supply chain the agreement is meant to feed. HALEU enriched to approximately 15.5% uranium-235 is the primary feedstock for TRISO-X coated particle fuel, according to the release.

TRISO-X received a 40-year Special Nuclear Material License from the U.S. Nuclear Regulatory Commission in February 2026, clearing the fabrication side of the chain before the enrichment contract was set.

X-energy said it is advancing more than 11 GW of new nuclear capacity across the United States and the United Kingdom, with commercial Xe-100 projects underway with Dow, Amazon, and Centrica. Those three offtake relationships span industrial heat, data center power demand, and a UK utility partner, and each depends on a fuel route that starts with enriched uranium and ends in coated particle form.

The two ends of that route are now under one commercial arrangement: enrichment in Ohio, fabrication in Tennessee. Domestic HALEU enrichment has been the binding constraint on advanced reactor developers whose designs cannot run on conventional LEU, and the Piketon plant is the point where X-energy's requirement is being placed.