Valar Watch · Fact safe-013

Fact safe-013

newrecordconfirmed Worst-case dose at the fence: the safety agreement says under 0.5 rem in one place and under 0.1 rem in another

2025-10 · safe-013 · Valar Atomics

The NSDA's 'Maximum Hypothetical Accident' assumes a large break in the reactor vessel, complete loss of helium coolant pressure, TRISO failures at twice unspecified AGR-1/2 test-program values, no credit for the building, filters or cooling systems, a ground-level release and stable air with a 1 m/s wind. Its results are stated two ways. Pages 11, 14 and 54 say site-boundary doses are below 0.5 rem (500 millirem); page 11 puts the nearest residence below 0.1 rem. Pages 32 and 37-38 say the public dose at the 400 m site boundary is below 1 mSv (100 millirem), a co-located worker at 100 m below 5 rem (the annual worker limit), and the control room below 0.5 rem; I-131 and noble gases dominate. The two boundary figures differ by a factor of five; both are stated as upper bounds, so they do not strictly contradict, but the looser 0.5 rem is the one Appendix C.3 relies on to justify on-site-only emergency planning (safe-016). Both are far below the 25 rem evaluation guideline the NSDA uses for 'Safety Class' equipment; on that basis the NSDA designates no Safety Class equipment and a 'Hazard Category 2' facility 'based on material at risk rather than consequence'. For scale, DOE's categorical exclusion puts natural background radiation in central Utah at about 100-120 millirem a year. The approved DSA's final figures are not public. Our check: the 400 m dispersion factor it uses (2.5e-4 s/m3, p.36) is 3.1 to 12.3 times lower than standard rural methods give for its own stated weather; rescaled, the 0.1 rem bound would be about 0.31 to 1.23 rem, still far below 25 rem. Hazard Category 2 is what DOE's standard assigns any reactor under 20 MW.

In plain termsThe company's worst-case accident, as written, is a big break in the reactor with every safety system assumed to fail except the fuel beads. The document gives two answers for how much radiation someone at the fence would get: under 500 millirem in one place, under 100 millirem in another. 100 millirem is about what a person in central Utah gets from nature in a year; 500 is about four to five years' worth. Both are well below the level at which the document's own rules would require the most stringent safety equipment, but the document gives two different numbers, and the final one is not public.

Ward250 Nuclear Safety Design Agreement, No. 100403, Rev 02 (status: Draft; issued for Public Release) (Valar Atomics, 2025-10) primary company “site boundary doses below 0.5 rem Total Effective Dose Equivalent”
Ward250 Nuclear Safety Design Agreement, No. 100403, Rev 02 (status: Draft; issued for Public Release) (Valar Atomics, 2025-10) primary company “Public dose at site boundary (400m): <1 mSv (100 mrem)”
NEPA Determination DOE-ID-26-005: Valar Ward250 Research Reactor (categorical exclusion B5.26) (U.S. Department of Energy, Office of Nuclear Energy (Idaho), 2026-04-22) primary government “Natural background radiation in central Utah is approximately 100-120 mrem/year.”

verified 2026-09-29: Re-read NSDA pp. 10-14, 32-38 and 54 and CX p. 5 on 2026-09-29. Holds as two upper bounds a factor of five apart. Page references corrected; plain no longer says what the document 'should' do. Correction 2026-09-29 (calculation audit): AGR 'rate' now unspecified AGR-1/2 values; 'still' air now stable air with a 1 m/s wind; added the 400 m dispersion check and the Hazard Category 2 basis.

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