Valar Goes Critical Outside the Labs

A week after we said the EOs had stopped being a thesis, Valar became the second advanced reactor to go critical under the Pilot Program (and the first ever to do it outside a national lab), Centrus signed the first commercial HALEU supply LOI at gigawatt scale, and Walmart became the first non-hyperscaler Fortune-10 to sign a nuclear PPA.

In context: Brent crude slid below $74 mid-week as oil resumed flowing through the Strait of Hormuz and JPMorgan cut its 2027 Brent forecast to $64. The cheap-hydrocarbon path is back on the table and the reflexive case for new nuclear gets softer with it. What carries the argument now is stacked outputs: criticalities on private sites, signed fuel contracts at commercial scale, and corporate offtake that no longer needs an AI workload behind it.

This week at a glance

NRC finalizes FY 2026 fee schedule with a $154/hr advanced-reactor preapplicant rate

Implements EO 14300's regulatory-cost reform: $337/hr professional rate, $154/hr reduced rate for advanced reactor applicants and preapplicants on qualifying activities. Gives developers a fixed planning number for the first time.
Elementl Power signs BWRX-300 Early Works Agreement with GE Vernova Hitachi for Meigs County, Ohio

New BWRX-300 siting in southeast Ohio under a developer outside the utility cohort. Adds Ohio to the BWRX-300 footprint alongside TVA's Clinch River and Ontario Power's Darlington lead unit.
Aalo Atomics Critical Test Reactor complete at INL, entering Operational Readiness Review

First new reactor built at INL in 50 years. DOE-Idaho cleared Aalo's DSA on April 30; Aalo expects criticality "well before" the July 4 deadline. Would be the third Pilot Program criticality after Antares and Valar.
TerraPower's Natrium reactor enters UK Generic Design Assessment

345 MWe sodium-cooled fast reactor with molten-salt storage moves into the UK's multi-year licensing review. First US Gen IV design in active UK GDA review. Pairs with Holtec-EDF's UK SMR project bid for Cottam this week.

In depth

Reference: new this issue

LOI: Letter of Intent. A non-binding agreement to negotiate a definitive contract. Common in early-stage commercial fuel and offtake deals. Centrus-Oklo signed one this week; the definitive supply agreement follows

ORR: Operational Readiness Review. DOE-Idaho's pre-startup gate for a private advanced reactor on the Pilot Program track. Aalo is in ORR now; Valar cleared ORR before its June 18 criticality

Technology

Valar Ward 250 Goes Critical in Utah: First DOE-Authorized Advanced Reactor Outside a National Lab

Before: Issue 8 reported Antares Mark-0 as the first private advanced reactor to achieve criticality under EO 14301, with Aalo and Valar both queued for July 4 attempts. Every prior DOE-authorized criticality on US soil, including Antares, took place inside a national laboratory. The open question was whether the Pilot Program's authorization track could be exercised on a non-lab site at all.

Now: On June 18 Valar Atomics' Ward 250 reactor achieved criticality at the Utah San Rafael Energy Lab in Orangeville, Utah. Ward 250 is the second of the originally selected pilot projects to clear the criticality bar and the first DOE-authorized advanced reactor built and operated outside the national laboratory system. It is a Gen IV TRISO-fuelled high-temperature gas reactor; the demonstration was zero-power, with DOE's Office of Nuclear Energy confirming the milestone at about 4:30 p.m. MDT. Antares ran at INL. Valar ran at a state energy lab. The geographic constraint just broke, two weeks ahead of the EO deadline.

→ Aalo's Critical Test Reactor at INL (assembly complete, ORR phase, criticality expected before July 4) as the third pilot attempt; Oklo Aurora-INL as the next DSA-cleared candidate behind the lead trio; whether DOE certifies a fourth criticality as “credit” against the EO target; how many of the remaining Pilot Program projects move to private-site operation now that the precedent exists

Deal

Walmart-Constellation PPA at Dresden: The Buyer Side Steps Past Hyperscalers

Before: Every previously announced nuclear corporate PPA carried a hyperscaler on the buyer side: Microsoft at Crane, Amazon at Susquehanna, Google with Kairos, Meta at Clinton. “Nuclear data center” had hardened into its own analyst category. The open question was when offtake demand would broaden past AI infrastructure into other Fortune-50 buyers who need round-the-clock firm power but are not training models.

Now: On June 23 Constellation and Walmart announced a long-term PPA sourced from the Dresden Clean Energy Center in Illinois. The agreement is Walmart's first nuclear contract and the first announced nuclear corporate PPA from a US Fortune-10 buyer outside the hyperscaler cohort. The deal is roughly 176 MW of wholesale supply (including 30 MW of expanded uprate capacity) under two 15-year terms beginning in 2029 and 2030. The electricity will power Walmart's perishable distribution center under development in Belvidere, Illinois. It sits on top of Constellation's December 2025 Dresden license renewal and underwrites planned Dresden uprates.

→ Whether other Fortune-50 retailers and industrials (Costco, Target, Kroger, the big logistics names) follow the Walmart template into PJM nuclear; how uprate-driven incremental MW get priced into long-dated PPAs versus baseline output; whether Constellation publishes a Fortune-50 commercial pipeline alongside its hyperscaler deals

Deal

Centrus-Oklo HALEU Letter of Intent: First Commercial HALEU Customer at Gigawatt Scale

Before: Centrus's HALEU production at the American Centrifuge Plant in Piketon, Ohio has run on DOE task orders since Phase I: a 900 kg Phase II delivery in June 2025, a Phase III contract extension through June 30, 2026, with options to eight years. Every kilogram had a federal customer in front of it. No commercial advanced reactor developer had signed a Centrus offtake LOI at gigawatt scale, which left the fuel pathway from federal demonstration quantities to commercial supply without an anchor tenant.

Now: On June 18 Centrus and Oklo signed a non-binding letter of intent for HALEU supply sufficient to fuel up to five Oklo Aurora powerhouses, as part of Oklo's planned 1.2 GW Aurora clean energy campus in southern Ohio, with deliveries beginning in 2029. Centrus runs the only NRC-licensed HALEU production facility in the US. The LOI contemplates prepayments from Oklo to Centrus to support production capacity ahead of a definitive supply agreement. Oklo and Kiewit Nuclear Solutions signed a parallel MOU for EPC planning on the Aurora campus the same day.

→ Whether the LOI converts to a binding offtake on schedule and what prepayment structure lands; whether General Matter, Urenco USA, or Orano sign parallel LOIs with X-energy, TerraPower, or Kairos; Centrus's Phase IV DOE production decision against the June 30 contract expiry; UF₆ deconversion capacity as the still-missing downstream piece of the domestic HALEU stack

Stat of the week

448,000 tonnes

Heavy metal of used nuclear fuel produced by all the world's nuclear power plants since the 1950s. Three-quarters sits in storage. One-quarter has been reprocessed. From the IAEA's first interactive global mapping tool, published this week.

Source: IAEA, June 2026

Global signal

Sweden: three concurrent moves convert the 2024 political pivot into a buildable permitting regime

The Swedish Parliament approved reclassification of uranium mining to treat permitting in line with other metals and minerals, and passed a government amendment opening additional coastal sites to potential nuclear projects. Two days later Nordic Baseload Power filed the fourth application for Swedish state support for new nuclear, proposing two large-scale reactors at the Barsebäck site where two reactors are currently being decommissioned. For US professionals: Sweden is operationalizing the political reversal from 2024 faster than France or the UK, which makes the Nordic nuclear cluster (Sweden, Finland, Estonia, now adding a parliament-approved nuclear law) the next European procurement target for Western reactor vendors. TerraPower's UK GDA entry this week is one of the moves positioning for it.

Question of the week

Two of three Pilot Program criticalities are in, and Valar just proved private sites work. Where does the operator pool come from when reactors aren't sitting under a utility's existing license? The utility SRO pipeline, the national labs, or something new?

Reply to this email with your take.

Until next Thursday,

Jace Arnold

Know someone in nuclear who'd find this useful? Send it along.

Companion tool: fuel.jrand.net. Live UF₆ conversion capacity, by facility.

All issues →