Radiation Exposure

What the document says

NPR reported on 30 September 2026, citing a proposal from Valar to federal regulators that NPR reviewed, that Valar's 'Project Beehive' near Price would include data centers and "some 456 small nuclear reactors", with a fuel-production facility and waste-storage facilities, on over 9,000 acres of Bureau of Land Management land. NPR describes "Valar's 25-megawatt electric units" and says that in aggregate the reactors would produce "around 9.6 gigawatts of power for the data centers" and more heat for industry, with the first reactors in 2028 and the full site possibly by 2032. The proposal itself was not found in public records. BLM's public case layer lists 'Project Beehive Small Modular Reactor/Data Center' as a pending Valar application. Valar describes its Ward 250 test reactor as a helium-cooled reactor fueled by TRISO particles, but on the pages and papers we read it has published no commercial unit's heat output, fuel form, enrichment, burnup, refueling schedule or spent-fuel plan. At a 29 September 2026 town hall in Price, Valar officials said used fuel from its Carbon County project would first be stored on site in dry, sealed casks under federal licensing, and that no specific long-term disposal site outside the area had been identified (ETV News, 30 September 2026). This note connects NPR's numbers to the used fuel and radiation they imply, with every unknown shown as a range.

Given

• N = 456 reactor units (NPR: 'some 456 small nuclear reactors') (RECORD: NPR, 30 Sept 2026, citing a Valar proposal NPR reviewed; the proposal was not found in public records)
• P_unit = 25 MW of electricity per unit (RECORD: NPR ('Valar's 25-megawatt electric units'))
• P_e = both carried: 9.6 GWe (NPR's aggregate 'for the data centers') and 11.4 GWe (456 x 25 MWe); the 1.8 GW difference is not explained in the article (RECORD: NPR; arithmetic ours)
• Reactor type = helium-cooled, TRISO-fueled high-temperature gas reactor (said of Ward 250); Valar's mission page speaks of 'hundreds of reactors on one Gigasite'; no commercial-unit design figures found in Valar's public documents (RECORD: Valar, 'Ward 250 By the Numbers' and mission page)
• Valar fuel element = Ward 250 block as DOE cleared it for shipment: 49.052 kg, 13.13 in across flats by 11.81 in tall, 170 compacts about 0.5 in by 2 in, at most 234.94 g of U-235 at up to 19.9-20%, so, if both are at their maximums, about 1.18 kg of uranium per block and 6.7 to 7.0 g per compact (the review also prints 1.33 g U-235 per compact, which does not multiply to 234.94 g) (RECORD: DOE Model 9979 safety evaluation report, 20 May 2026 (derived))
• η = heat-to-electricity efficiency 0.33 to 0.45 (central 0.40) (ASSUMPTION, bounded by REFERENCE values: AVR 15/46 MW, Peach Bottom 40/115, Fort St. Vrain 330/842, THTR 300/750 (INL/EXT-10-19329); design targets 45% (Sandia); EIA's 33% example)
• CF = capacity factor 0.80 to 0.95 (central 0.90) (ASSUMPTION; U.S. fleet 90.8% to 93.4% in 2016-2025 (EIA, REFERENCE); past gas-cooled reactors ran far less)
• B = discharge burnup 80 to 170 GWd per metric ton of heavy metal (central 120) (ASSUMPTION within REFERENCE values: pebble-bed benchmark cases 80 to 204 (INL/EXT-20-60236), Xe-100 168 (X-energy report to NRC), prismatic MHTGR about 120 (INL catalog via Sandia; the only archived prismatic value))
• p = core specific power 50 to 130 MW of heat per metric ton (central 100) (ASSUMPTION; pebble-bed references 99 to 128 (derived from INL, ANL, Sandia tables); no archived value for a low-enriched prismatic power plant)
• Pebble = 6 cm pebble: 2.5 cm fuel zone inside a 0.5 cm graphite shell; 5 to 9 g of uranium (central 7); about 202 g whole; loose packing 0.60 to 0.74 (central 0.61) (REFERENCE: INL/EXT-20-60236 Tables 1-3, 8-10; ANL/NSE-22/98 Table 3-1; Sandia Table 3-1 (pebble mass derived))
• Prismatic volume = 8.4 to 24.5 m³ per metric ton of uranium: Fort St. Vrain's thorium-bearing elements to the Ward 250 block as cleared (central: the cleared block) (REFERENCE: NWTRB Fort St. Vrain fact sheet; DOE Model 9979 review (derived))
• y = chain yields per fission, U-235 / Pu-239 (thermal): Cs-137 6.189% / 6.614%; Sr-90 5.782% / 2.104%; also Zr-95, Ru-103, Ru-106, Cs-133 and Ce-144 (REFERENCE: England & Rider, Evaluation and Compilation of Fission Product Yields 1993 (Los Alamos, October 1994), Table 7 (a scanned table))
• Pu share = share of fissions in plutonium, averaged over the fuel's life: 0 to 0.4 (central 0.3) (ASSUMPTION; the one archived inventory implies about 0.3 to 0.4)
• Inventory = at about 120 GWd/t, g per metric ton: Cs-137 4,410; Sr-90 2,100; Cs-134 421; Ru-106 355; Eu-154 73; Sb-125 21.6 (REFERENCE: Sandia SAND2023-08602R Table A-1 (INL fuel cycle catalog, one prismatic design))
• Capture products = Cs-134 matched to that inventory x 0.6 to 1.8; Np-239 0.35 to 0.55 per fission (0.47 derived); Eu-154 x 0.5 to 1.5; Sb-125 x 0.7 to 1.3; Cs-134 gamma 1.50 to 1.60 MeV per decay (ASSUMPTION (one archived inventory; enrichment and table time point unknown))
• T½ = Cs-137 30.08 y; Sr-90 28.9 y; Cs-134 2.0652 y (REFERENCE: Sandia Table A-1 (a secondary DOE-laboratory compilation))
• E_f = 200 MeV per fission (±3% assumed), so 2.70 x 10^21 fissions per MWd (REFERENCE: DOE-HDBK-1019/2-93; ±3% ASSUMPTION)
• Dose engine = pf-007's published calculation, unchanged: gamma lines of 43 fission products, photon attenuation, ICRP 74 front-on conversion; whole body at 50 cm from the near surface; skin at contact (RECORD: pf-007 (its data limits carry over))
• CT = 1 to 10 mSv effective dose for a typical CT scan (REFERENCE: FDA, What are the Radiation Risks from CT?)
• Comparators = large U.S. reactors: median 3,411 MW of heat (middle half 2,797 to 3,630; 94 units), efficiency 0.300 to 0.343, burnup 50 to 60 GWd/t; U.S. spent fuel 2,000 to 2,200 t a year; U.S. nuclear capacity 98,436 MWe (2025) (REFERENCE: NRC NUREG-1350 App. A; ANL; NWTRB; DOE; EIA Table 6.07.B)
• Decay heat = 10 years after discharge: Xe-100 32.2 and reference PWR 40.6 kW per GWe-year, so 12.9 to 13.8 kW per GW-year of heat (REFERENCE: ANL/NSE-22/98 Table E-2 (prepared for DOE))
• Life = 20 and 40 years per unit; units start evenly from 2028 to 2032 (ASSUMPTION (no Valar operating life was found in public records); dates RECORD (NPR))
• Pool = Olympic pool taken as 2,500 m³ (50 m x 25 m x 2 m) (ASSUMPTION (a nominal size))

Working

1. 456 x 25 MWe = 11.4 GWe; NPR's aggregate: about 9.6 GW; 9.6 GW ÷ 456 = 21.05 MWe per unit; gap 1.8 GW = 15.8% of 11.4 GWe
   NPR does not reconcile its two numbers. The 9.6 GW may be the data centers' share (NPR adds 'even more thermal heat' for industry), or the whole fleet at about 21 MWe a unit. Read as heat, it does not fit: 9.6 GW would be 21 MW of heat per unit, less than each unit's rated 25 MW of electricity. Every result carries both electric figures; neither is picked. The proposal was not found in public records.
2. Heat P_th = P_e ÷ η, η = 0.33 to 0.45 9.6 GWe: 21.3 to 29.1 GW of heat (central 24.0); 11.4 GWe: 25.3 to 34.5 (central 28.5); per unit 46.8 to 75.8 MW = 6.25 to 10.1 median large U.S. reactors (3,411 MW of heat); 5.88 to 12.4 across the middle half of U.S. units
   No commercial unit's heat output was found in Valar's public documents, so it follows from the electric figure and an efficiency. Gas-cooled plants have turned 33% (AVR), 35% (Peach Bottom), 39% (Fort St. Vrain) and 40% (THTR) of their heat into electricity; design targets reach 45%. Lower efficiency means more heat, and so more radioactive leftovers, for the same electricity. The fleet would be 9.8% (9.6 GWe) to 11.6% (11.4 GWe) of U.S. nuclear capacity.
3. Heat made per year E = P_th x CF x 365.25 days, CF = 0.80 to 0.95 = 7,890 GWd a year (9.6 GWe basis) and 9,370 GWd a year (11.4 GWe basis); 6,230 to 12,000 GWd a year across both; fissions = E x 2.70 x 10^21 per MWd
   CF is the share of the year at full power. U.S. reactors ran 90.8% to 93.4% of the year in 2016-2025 (EIA); past gas-cooled reactors ran far less, and a lower CF lowers every yearly total in proportion. Every split uranium or plutonium atom leaves two radioactive fragments, so the leftovers follow the heat made, whoever buys the power.
4. Used heavy metal per year = E ÷ B, B = 80 to 170 GWd per metric ton = 66 t (9.6 GWe basis) and 78 t (11.4 GWe basis); 37 to 150 t across both 20 years: 730 to 3,000 t; 40 years: 1,500 to 6,000 t (central 2,600 and 3,100); plus about half a core-load still in the reactors at the end: 82 to 350 t
   Burnup is the heat each metric ton of uranium gives before it is removed. This is 1.7% to 7.5% of the 2,000 to 2,200 t of spent fuel U.S. reactors discharge each year, and 0.29 to 0.75 of what a fleet of large water-cooled reactors making the same heat would discharge at 50 to 60 GWd/t. That lower uranium mass favors Valar's design type.
5. Pebbles = heavy metal ÷ (5 to 9 g); mass = number x 202 g; bulk volume = number x 113.1 cm³ ÷ packing (0.60 to 0.74) per year: 4.1 to 30 million pebbles, 820 to 6,100 t, 620 to 5,600 m³ = 0.25 to 2.3 Olympic pools (central 0.70 and 0.83) 40 years: 10.0 to 90 pools (central 28 and 33)
   A 6 cm pebble holds a few grams of uranium in about 200 g of graphite, which is why this kind of used fuel is light in uranium but bulky. Volumes are loose pebbles only; canisters, casks and spacing would add more.
6. Ward 250 blocks as DOE cleared them: about 1.18 kg uranium (at the maximum U-235 and enrichment), 49.052 kg and 0.0289 m³ each = 24.5 m³ and 41.6 t of block per metric ton of uranium per year: 31 to 130 thousand blocks, 1,500 to 6,200 t, 890 to 3,700 m³ = 0.36 to 1.5 pools; 40 years: 14 to 59 pools (central 26 and 31) denser prismatic fuel (8.4 m³ per metric ton): down to 310 m³ a year
   The block DOE cleared for shipment to Ward 250 is the only Valar fuel element on record; whether a commercial unit would use it, or pebbles, is not known. Valar's draft safety paper lists 250 kg of heavy metal in 76 elements for Ward 250 (3.29 kg each), which DOE's figures do not match. Standard power-plant blocks are larger, but no archived source gives their uranium loading for low-enriched fuel.
7. Cs-137 made = fissions x yield; yield 6.19% (U-235) to 6.61% (Pu-239); Sr-90 5.78% to 2.10% per year: Cs-137 230 to 482 kg = 19.9 to 41.8 million curies (central 305 and 363 kg); Sr-90 105 to 288 kg = 14.5 to 39.6 million curies
   Cesium-137 and strontium-90, with half-lives of about 30 and 29 years, are the main long-lasting radioactive leftovers of the first few centuries. As fuel burns, plutonium made from uranium-238 also splits; it makes slightly more cesium-137 and much less strontium-90. Each year's cesium-137 would be about 5.57% to 12.6% of what all U.S. reactors make, because the fleet's heat is that share of theirs.
8. Each unit runs L years; units start evenly over W = 4 years (2028 to 2032) Cs-137 left when the last unit stops = made x (1 − e^(−λL)) x (1 − e^(−λW)) ÷ (λ² W L), λ = ln 2 ÷ 30.08 y 40 years each: Cs-137 made 9,200 to 19,000 kg; left at the end 5,700 to 12,000 kg (498 to 1,040 million curies); 100 years later about 0.10 of that (570 to 1,200 kg); 300 years later 5.7 to 12 kg
   Cesium-137 decays while more is made, so not all of it is present at the end. Starting every unit at once would leave about 5% more. No Valar operating life was found in public records; per-year figures scale to any other life.
9. Decay heat of one year's used fuel 10 years later = heat made (GW-years) x 12.9 to 13.8 kW per GW-year = 220 to 450 kW (central 280 and 330); 100 years later 43 to 110 kW; per GWe-year 28.6 to 41.8 kW (reference PWR 40.6)
   The ANL/INL study gives 32.2 kW per GWe-year for Xe-100 at 40% efficiency and 40.6 for a reference PWR at 34%; per unit of heat the two differ by about 7%. Per unit of electricity this fleet's used fuel gives off less heat than a PWR's unless its efficiency is at the low end. Decay heat sets how closely used fuel can be packed in storage. At one year it is higher still, but no archived reference value anchors it, so no figure is given.
10. Activity of each fission product in one metric ton after running at specific power p to burnup B (T = B ÷ p) and cooling t: A = y x F x (1 − e^(−λT)) x e^(−λt) (pf-007) added: Pu-239 yields for five chains; Cs-134 from neutron capture on Cs-133, matched to the archived inventory; Eu-154 and Sb-125 tied to the same inventory; Np-239 from U-238 capture
    pf-007's calculation was built for a reactor that ran less than a month; commercial fuel runs for years. Over years, plutonium fissions and neutron capture add cesium-134, which carries about half the dose from a year-old fuel pebble. Without these additions the one-year dose would be 2.3 times too low (4.1 mSv instead of 9.2 at central inputs). Check: at 120 GWd/t and a plutonium share of 0.3, the model gives the archived inventory's Cs-137, Sr-90, Ru-106 and Cs-134 within 1.4% to 3.6%.
11. Five minutes: whole body = effective dose at a point 50 cm from the near surface (ICRP 74 front-on); skin = dose where the piece touches the skin one 6 cm pebble (2.5 cm fuel zone in a 0.5 cm shell); one Ward 250 compact (1.27 x 5.08 cm, 6.7 to 7.0 g uranium) and one whole block (49 kg) as spheres of the same volume
    Same geometry and dose convention as pf-007. The central value counts only photons that leave the piece unscattered, so it is lower than a full count; counting scattered photons raises the whole-body dose about 1.36 times, the top of each range. Beta particles are not counted: a pebble's graphite shell stops most, but for a bare compact they would probably add more than the gamma dose. On the compact's real cylinder the contact dose is about 0.97 of the sphere's.
12. One pebble, whole body, five minutes: 1 day 302 mSv (100 to 760); 30 days 86 mSv (29 to 220); 1 year 9.2 mSv (2.4 to 41); 10 years 1.6 mSv (0.63 to 5.1) skin touching it: 1 day 120,000 mSv (42,000 to 300,000); 1 year 3,800 mSv (980 to 17,000); 10 years 648 mSv (260 to 2,100) main sources: 1 day La-140 28%, I-132 14%, Nb-95 9%; 1 year Cs-134 49%, Cs-137+Ba-137m 17%, Nb-95 13%; 10 years Cs-137+Ba-137m 81%, Cs-134 14%
    Each range covers every combination of the uncertain inputs at their low and high ends (2,048 combinations). Specific power, burnup, uranium per pebble, the cesium-134 factor and scattered photons move it most. Held at 30 cm instead of 50 cm the whole-body dose is 2.6 times higher. For scale, FDA puts a typical CT at 1 to 10 mSv, and U.S. rules allow a radiation worker 500 mSv a year to the skin of the hands. Checked against published Oak Ridge National Laboratory (ORNL) calculations for spent pebbles: a year after removal our source gives 0.9 to 1.4 times ORNL's per-pebble gamma output, with cesium-137 within 4%; about four days after removal ORNL estimated 33.5 R/h at 1 m from one pebble, about half what this calculation gives for the same pebble (ORNL/SPR-2024/3615, ORNL/SPR-2023/2988).
13. Cooling time until five minutes = one 10 mSv CT (whole body): one pebble 0.93 years (0.35 to 5.9); one compact 1.1 years (0.52 to 5.1); 50 cm from a whole Ward 250-type block 81 years (60 to 140) until 1 mSv: pebble 22 years (3.8 to 63); until the skin touching a pebble gets under 500 mSv in five minutes: 15 years (2.6 to 54)
    This favors Valar: about a year after removal, one used fuel pebble held for five minutes gives a whole-body dose inside FDA's CT range. The longest times need every dose-raising choice at once. A whole block, or many pebbles together, takes far longer, and the skin of a hand touching one pebble receives more than a worker's yearly hand limit in those five minutes for years longer.
14. Independent checks at central inputs, one pebble: calculation A 9.0 mSv at 1 year, 0.91 years to one CT; calculation B 10.9 mSv, 1.10 years; this calculation 9.2 mSv, 0.93 years
    Two calculations were made independently from the same input table. With A's choices this calculation reproduces A exactly; with B's choices (half the scattered photons counted, neptunium-239, Eu-154 and Sb-125) it reproduces B within 2%. The differences are stated choices, mainly whether scattered photons count in the central value, not errors.
15. Used-fuel volume vs a same-heat fleet of large water-cooled reactors (0.44 m³ of assemblies per metric ton): pebbles 11 to 64 times (central 25); Ward 250 blocks 16 to 42 times (central 23); denser prismatic fuel from 5.6 times per GWe-year: 4.8 to 14 t of uranium (PWR 21.7); pebbles 81 to 520 m³ (PWR 9.58); the same arithmetic gives ANL's Xe-100 figures: 5.40 t and 118 m³ (ANL: 5.41 and 118)
    Published studies differ mainly by method: ANL/INL found 12.3 times for Xe-100 pebbles packed as tightly as possible; the National Academies cite about 23.5 times (a vendor figure); Wainwright et al. (peer-reviewed) found 25 to 30 times for prismatic blocks, with 40 to 50% less mass and a repository about 30% smaller; Krall et al. (peer-reviewed) found 2 to 30 times for water-, salt- and sodium-cooled designs, analyzed no gas-cooled design, and are disputed by the other two. Graphite reflector blocks could add up to 24.5 m³ per GWe-year (ANL), 190 to 270 m³ a year here, if they stay in the reactor for its whole life; Valar's reflector design was not found in public records.

Results (central value, with the low-to-high range over every uncertain input). Part 1: one used fuel piece, five minutes. Part 2: the 456-unit fleet's used fuel

Whole body = effective dose, the quantity FDA gives for CT, at a point 50 cm from the near surface of the piece. Skin = dose where the piece touches the skin, a different quantity, not comparable with a CT. Central values leave out scattered photons and beta particles, so from about a year after removal they are lower estimates; the one-day and one-month values also assume full power until removal, and could be somewhat high for a pebble that ran its last pass at lower power; the top of each dose range counts scattered photons. Fleet ranges run from the 9.6 GWe basis at its lowest to the 11.4 GWe basis at its highest. Volumes are loose pebbles or whole blocks, before any canisters or casks. No commercial Valar design was found in public records: every design quantity is a stated range.

Result

On NPR's figures (456 units; 9.6 or 11.4 GWe), the fleet would make 21.3 to 34.5 GW of heat. That equals 6.25 to 10.1 median large U.S. reactors, so it would make about the same radioactive leftovers: 230 to 482 kg of cesium-137 and 105 to 288 kg of strontium-90 a year, 5.57% to 12.6% of all U.S. reactors' output. Its used fuel would hold 37 to 150 t of uranium a year, 0.29 to 0.75 times what large reactors making the same heat would leave. Because that uranium sits in graphite, it would fill 0.25 to 2.3 Olympic pools a year as loose fuel pebbles (10.0 to 90 pools over 40 years), or 0.36 to 1.5 pools as Ward 250-type blocks. That is 11 to 64 times (pebbles) or 16 to 42 times (blocks) the volume of same-heat large-reactor fuel, before packaging. One used fuel pebble held for five minutes gives the whole body 302 mSv a day after removal (100 to 760) and 9.2 mSv after a year (2.4 to 41). It falls to one 10 mSv CT after 0.93 years (0.35 to 5.9), while the skin touching it receives 120,000 mSv at one day (42,000 to 300,000) and 3,800 mSv at one year (980 to 17,000). These numbers rest on NPR's account of a proposal not found in public records, and no commercial Valar design was found in public records, so every design quantity is a range.

Sources

• A startup wants to build a massive nuclear-powered data center on public land in Utah (NPR, 2026-09-30) · quotes checked against the article; no copy is archived here
• Valar Atomics hosts town hall on proposed Carbon County site (ETV News, 2026-09-30) · quoted from the article
• BLM National MLRS Land Use Authorizations: Rights-of-Way (query by customer name) (U.S. Bureau of Land Management) · case UTUT106801248, Price Field Office, Pending
• Mission (Valar Atomics) · 'A New Model for Nuclear Power'
• Ward 250 By the Numbers (Valar Atomics, 2026-06-28) · 'What is Ward250?'
• Safety Evaluation Report: Letter Amendment of Certificate of Compliance No. 9979 for the Model 9979 Package (Ward 250 TRISO fuel block) (U.S. Department of Energy, 2026-05-20) · pp. 2-3 and 5 (block mass, 170 compacts, 234.94 g U-235, compact size)
• Ward250 Nuclear Safety Design Agreement, No. 100403, Rev 02 (status: Draft) (Valar Atomics, 2025-10) · p. 52, Table 6 (76 fuel elements, 250 kg heavy metal)
• NEPA Determination DOE-ID-26-005: Valar Ward250 Research Reactor (U.S. Department of Energy, 2026-04-22) · pp. 4-5 (Ward 250 only: one core, dry storage casks to a DOE-approved facility)
• Benchmark for Fuel Shuffling and Depletion for Pebble-Bed Reactors, INL/EXT-20-60236 Rev. 1 (Idaho National Laboratory (U.S. Department of Energy), 2020-09) · Tables 1-3, 6, 8-10, 16 (pebble geometry, loading, packing, burnup, power per particle)
• Nuclear Waste Attributes of SMRs Scheduled for Near-Term Deployment, ANL/NSE-22/98 Rev. 1 (Kim, Boing, Halsey, Dixon) (Argonne and Idaho National Laboratories, for DOE (copy hosted by INL), 2022-11-18) · Tables E-1, E-2, 3-1, 4-2 (a laboratory report, not a journal paper)
• Advanced Reactors Spent Fuel and Waste Streams Disposition Strategies, SAND2023-08602R (Sandia National Laboratories (U.S. Department of Energy), 2023-06-28) · Table 3-1; Appendix A.1 and Table A-1 (inventory and half-lives)
• Evaluation and Compilation of Fission Product Yields 1993 (T. R. England and B. F. Rider) (Los Alamos National Laboratory (scanned copy via OSTI, marked LA-SUB--94-170), 1994-10) · Table 7, printed pp. 19-20, rows 90, 95, 103, 106, 133, 137, 144 (scanned)
• DOE Fundamentals Handbook: Nuclear Physics and Reactor Theory, Vol. 2, DOE-HDBK-1019/2-93 (U.S. Department of Energy, 1993-01) · Module 4, printed p. 33
• High Temperature Gas-Cooled Reactors Lessons Learned Applicable to the Next Generation Nuclear Plant, INL/EXT-10-19329 Rev. 1 (Idaho National Laboratory, 2011-04) · Table 1 and sec. 1.4 (AVR, Peach Bottom, Fort St. Vrain, THTR power and output)
• Xe-100 Topical Report: TRISO-X Pebble Fuel Qualification Methodology, Revision 2 (ML21246A289) (X Energy, LLC (submitted to the NRC), 2021-09-02) · p. 33 table (burnup 168 GWd/MTU; enrichment 15.5%; loading redacted)
• TRISO Particles: The Most Robust Nuclear Fuel on Earth (U.S. Department of Energy, 2019-07-09) · AGR program section
• Electric Power Monthly, Table 6.07.B: Capacity Factors for Utility Scale Generators Primarily Using Non-Fossil Fuels (U.S. Energy Information Administration, 2026-09-24) · annual rows 2016-2025, nuclear column
• What is the efficiency of different types of power plants? (U.S. Energy Information Administration)
• NUREG-1350 Vol. 35, Appendix A: Commercial Nuclear Power Reactors, Operating Reactors (U.S. Nuclear Regulatory Commission, 2025) · Appendix A, licensed thermal power of 94 operating units
• Commercial Spent Nuclear Fuel (fact sheet, Rev. 2) (U.S. Nuclear Waste Technical Review Board) · pp. 2-3
• 5 Fast Facts about Spent Nuclear Fuel (U.S. Department of Energy, 2022-10-03) · fact 2
• Department of Energy-Managed Spent Nuclear Fuel at Fort St. Vrain (fact sheet, Rev. 1) (U.S. Nuclear Waste Technical Review Board) · pp. 2-4 (element size, 1,464 elements, about 15 MTHM, canister count)
• A multidisciplinary framework from reactors to repositories for evaluating spent nuclear fuel from advanced reactors (Wainwright, Christiaen, Atz and others), Scientific Reports 14:26904 (Scientific Reports (Springer Nature); peer-reviewed, 2024-11-06) · Results: SNF mass and volume; decay heat; repository footprint
• Nuclear waste from small modular reactors (Krall, Macfarlane and Ewing) (Proceedings of the National Academy of Sciences (copy in PubMed Central); peer-reviewed, 2022-05-31) · Abstract (no gas-cooled design analyzed; disputed by the ANL/INL study and Wainwright et al.)
• Merits and Viability of Different Nuclear Fuel Cycles and Technology Options and the Waste Aspects of Advanced Nuclear Reactors (National Academies of Sciences, Engineering, and Medicine (copy hosted by Sandia), 2022) · ch. 5, printed p. 168
• Advanced Reactor Spent Fuel Geologic Disposal Technical Issues (Pensado, Parmenter, Stothoff and Livingston) (Center for Nuclear Waste Regulatory Analyses, for the U.S. Nuclear Regulatory Commission, 2025-09) · sec. 2.2 (citing a PNNL study that is not archived here)
• What are the Radiation Risks from CT? (U.S. Food and Drug Administration, 2017-12-05) · Radiation Dose from CT Examinations
• 10 CFR 20.1201: occupational dose limits for adults (Legal Information Institute (Cornell)) · (a)(2)(ii): 500 mSv a year to the skin of any extremity
• NuDat 3: half-lives, gamma-ray energies and intensities (ENSDF) (National Nuclear Data Center, Brookhaven National Laboratory) · gamma lines in pf-007's calculation and for Cs-134, Eu-154 and Sb-125 here; no copy of NNDC's pages is kept here
• ICRP Publication 74: Conversion Coefficients for use in Radiological Protection against External Radiation (International Commission on Radiological Protection, 1996) · Table A.17 (as in pf-007); not openly published, so no copy is archived
• Identify and Assess Technical Challenges in Safeguards Measurements of Spent Advanced Reactor Fuels (ORNL/SPR-2024/3615) (Oak Ridge National Laboratory (via OSTI.gov), 2024) · Table 2, p.8
• Nuclear Material Control and Accounting for Pebble Bed Reactors (ORNL/SPR-2023/2988) (Oak Ridge National Laboratory (via OSTI.gov), 2023-12) · Pebble 6 measurement section

Checked: Two calculations were made independently from the same input table: one built on pf-007's published dose calculation, one written separately with its own nuclear data and shielding code. A third check re-ran both (each gave identical output on a second run), reproduced the first exactly and the second within 2% when given the same choices, and traced every difference to a stated choice, mainly whether scattered photons count in the central value. Every input was re-read in its archived copy; the fission yields come from a scanned table and were read from the scanned pages. The same arithmetic reproduces the ANL/INL study's Xe-100 figures (5.40 t and 118 m3 per GWe-year, against 5.41 and 118). NPR's quotes were checked against the article. Afterward we added pictures, built from the model's numbers and checked against them; reworded some plain-language sentences; now use the engineering word 'pebble' for the fuel spheres throughout; and added one table row (big reactors' used fuel in Olympic pools, worked out with the model's own formula and inputs). Separate reviews checked the pictures' numbers, wording and drawing, and the fixes were checked again. A later check against published Oak Ridge National Laboratory calculations for spent pebbles found the per-pebble figures within a factor of 2 of every usable one, and led to a note that the one-day and one-month values may be somewhat high.