The NSDA's accident doses are calculated for a site boundary 400 m from the reactor, described as 'the nearest point of public access', with the nearest residence at about 800 m and the nearest group at 1,200 m. DOE's categorical exclusion describes USREL as 'a 20.6-acre site', with Ward 250's reactor complex and fuel laboratory inside a security-fenced area of about 2 acres; ETV News (October 2025) reported Valar's allotment at the lab as 11 acres. A circle of 400 m radius covers about 124 acres (pi x 400 m squared = 502,655 square metres), so no point on a 20.6-acre site can be 400 m from every edge of it. The 400 m boundary must therefore run over land outside the lab, and no record read says who controls public access there. The NSDA's own dispersion factors show why it matters: the one it uses at 100 m is 16 times the one at 400 m (4.0e-3 versus 2.5e-4 s/m3), and its worst-case dose at 100 m is under 5 rem. Our check: the 100 m factor meets DOE's prescribed default, but the 400 m factor is 3.1 to 12.3 times lower than standard rural methods give for the paper's stated weather, so its 400 m bounds may be low by that factor (still far below 25 rem). In August 2026 Valar said it was buying about 110 acres north of the lab from Emery County, and later state records describe the land as purchased (mine-018); that could put more nearby land under Valar's control, but it post-dates the October 2025 NSDA and no record read says whether it covers the 400 m circle. No public copy of the approved DSA's site description, which would define the boundary, was found. DOE's categorical exclusion says 'Radiation monitoring and controlled access are maintained during operations', without saying where. No DOE document read sets 400 m as a required exclusion boundary for Ward 250; it is the distance at which Valar's draft paper calculates public doses.

• Ward250 Nuclear Safety Design Agreement, No. 100403, Rev 02 (status: Draft; issued for Public Release) (Valar Atomics, 2025-10) primary company “400m to site boundary, 800m to nearest residence”
• 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 “a 20.6-acre site in a rural area of central Utah”
• What's actually happening at the Utah San Rafael Energy Lab? (ETV News, 2025-10-10) news “Their buildings are currently under construction in their 11-acre allotment.”