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Fact safe-010

newrecordconfirmed DOE shipping review: fuel for Ward 250 is HALEU (under 20%), not the 4.95% its safety agreement lists
2026-05-20 · safe-010 · U.S. Department of Energy, Valar Atomics, National Criticality Experiments Research Center

A DOE Safety Evaluation Report, prepared by the manager of DOE's Packaging Certification Program and approved by DOE's Headquarters Certifying Official on 20 May 2026, reviews and recommends an amendment to the certificate of the Model 9979 shipping package to allow 'limited shipments' of high-assay low-enriched uranium (HALEU) TRISO fuel compacts from the National Criticality Experiments Research Center (NCERC) in Nevada to the Valar Ward 250 reactor site in Utah. Each package holds one hexagonal graphite 'WARD250 FUEL BLOCK' (Valar drawing V-002782) with 170 compacts; the U-235 in a block is 234.94 grams 'at less than 20% enrichment', the application describes the uranium in the particles as 'enriched to a maximum of 19.9 wt.% U-235', and the stated condition is 'less than 20 weight percent'. The report says the block's end use is as a fuel element in the Ward 250 microreactor. Valar's NSDA (October 2025, Table 6) lists Ward 250's fuel enrichment as '4.95% U-235' on the basis of 'LEU limits', and says that if the fuel differs from the specification its safety assumptions will be updated in the PDSA. The later PDSA and DSA are not public, so whether DOE's approved safety basis was updated to HALEU cannot be checked. This is the DOE record that disc-001 lacked: it matches the NOVA release's 'HALEU TRISO' wording (orig-008, orig-009) and a Valar speaker's statement that part of the core went critical in Nevada (mine-033), and conflicts with the NSDA's 4.95% figure (orig-034, orig-040). Per element, the NSDA's own figures imply 162.83 g of U-235 in 3.29 kg of heavy metal; DOE's block holds 234.94 g of U-235 in 1.18 kg of uranium. No single enrichment fits both (76 such blocks holding 250 kg would need 7.14%), so Table 6's equal per-element loading does not match the block DOE cleared, unless some of the 76 elements are unfueled or loaded differently, which the paper does not say.

In plain termsUranium fuel is graded by the share of U-235, the kind that splits. Ordinary power-plant fuel is below 5%; HALEU runs from 5% to just under 20% (exp-002). Valar's public safety agreement says Ward 250 burns 4.95% fuel. DOE's own shipping review says the fuel approved for shipment to Ward 250 from Nevada is HALEU, enriched up to 19.9%, which is up to about four times richer. The fuel is the same kind of tiny coated bead (TRISO, exp-001); what differs is how much of the splitting kind of uranium is in each bead. Richer fuel changes the reactor physics, and the safety agreement says fuel-design changes will be carried into the later safety analysis. The only public safety agreement describes different fuel from the fuel DOE reviewed for shipment; the safety analysis DOE approved, which may have been updated, was not found in public records.
verified 2026-09-29: Re-read the SER (all 9 pages) and NSDA Table 6 and pp. 11, 26 on 2026-09-29. Conflict holds. Fixed: the SER reviews and recommends the letter amendment (the amendment letter itself was not read); added the 19.9% maximum the SER gives; plain now says 'approved for shipment' and 'up to about four times', not 'sent' and 'roughly four times'. Correction 2026-09-29 (calculation audit): added the per-element U-235 and heavy-metal comparison with DOE's block. Correction 2026-09-30 (source objectivity review): reworded the plain-language text.

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