f A Light Water Reactor power economy lacks proliferation resistance

A Light Water Reactor power economy lacks proliferation resistance

Comments on Charles Barton: Nuclear power for weapons? Mark Z. Jacobson's proliferation of errors

by Joachim Gruber

Thank you for this resourceful paper! Although I tend to think along the lines of Jacobson's paper, your arguments appear convincing to me (my training is in nuclear physics).

Some technical points:

  1. CANDU reactors have a modular structure such that you can exchange fuel rods without shutting down the entire reactor. This makes it much more easy to breed weapon's grade plutonium with CANDU reactors than with Light Water Reactors, because to breed weapons grade plutonium you need to keep the irradiation time of the fuel small. This means you need to exchange the fuel elements more frequently than when you merely want to generate electricity.
  2. Reactor Plutonium has been used for low yield (below 20 kt) nuclear explosions.

    Rough estimate of annual plutonium production in a 3 GWth (approx. 1 GWe) Light Water Reactor (LWR)

    • plutonium, Pu 239: 190 kg/a,
    • which together with the other fissile Pu isotopes amounts to: > 10 reactor plutonium bombs/a.


    • burn-up: 30 GWth d per tHM
    • Pu 239 inventory after burn-up: 5.2 kg/tHM (Source: p. 48 of R. Gasteiger, Calculation of burn-up data for spent LWR-fuels with respect to the design of spent fuel reprocessing plants, KfK 2373, Institut für Angewandte Systemanalyse, Projekt Wiederaufarbeitung und Abfallbehandlung, Gesellschaft für Kernforschung, November 1976)
    • power generated per year: 3 GWth 365 days, thus
    • maximum recharge per year: 3 GWth 365 days / (30 GWth d / tHM) = 36.5 tHM/a, thus
    • annual Pu 239 discharge: 5.2 kg/tHM 36.5 tHM/a = 189.8 kg/a
    • reactor grade plutonium critical mass: 18 kg (in cache, 2. February 2011). In comparison: critical mass of a bare sphere of pure isotopes.
      National Resources Defense Council estimate of the approximate fissile material requirements for pure fission nuclear weapons, Source: H.D. Sokolski, Assessing the IAEA's Ability to Verify the NPT, Part I of Sokolski (ed.), Falling Behind: International Scrutiny of the Peaceful Atom, Febr. 2008.

    "If nuclear energy becomes a principal part of the response to reducing CO2 emissions 2,000 to 3,000 reactors or more of 1 GWe each would be needed by 2050. This means tens of thousands of nuclear bombs equivalent of plutonium would be created in these reactors each year." Source: Clean Energy Standard Should Not Include Nuclear, Coal: Experts

  3. Low Enriched Uranium as fed into Light Water Reactors can be used to shorten the path to weapons grade uranium. (Victor Gilinsky, Marvin Miller, Harmon Hubbard, A Fresh Examination of the Proliferation Dangers of Light Water Reactors, October 22, 2004, The Nonproliferation Policy Education Center, Washington, DC, USA)
  4. Iran claims to use its enrichment plant for a civilian nuclear (energy) program. If there weren't nuclear power plants, enrichment would clearly be identifiable as having a military application.
  5. For countries with covert or declared enrichment plants, timely detection of weapons grade uranium made from low enriched uranium as used in Light Water Reactors is not possible. (page 30, Fig. 4 of Falling Behind: International Scrutiny of the Peaceful Atom, Henry Sokolski (ed.), The Nonproliferation Policy Education Center, 2008).

  6. When nuclear fuel enrichment and reprocessing is combined with commercial nuclear power generation there is a problem with possible uranium/plutonium clandestine diversion by the state or a subnational group: Henry D. Sokolski (ed.) Falling Behind: International Scrutiny of the Peaceful Atom, Strategic Studies Institute - United States Army War College, February 27, 2008 (in cache, February 3, 2011)

    Chapter 1: Henry D. Sokolski "Assessing the IAEA's Abiity to Verify the NPT"
    A Report of the Nonproliferation Policy Education Center on the International Atomic Energy Agency's Nuclear Safeguards System

    Currently, the IAEA is unable to provide timely warning of diversions from nuclear fuel- making plants (enrichment, reprocessing, and fuel processing plants utilizing nuclear materials directly useable to make bombs). For some of these plants, the agency loses track of many nuclear weapons-worth of material every year. Meanwhile, the IAEA is unable to prevent the overnight conversion of centrifuge enrichment and plutonium reprocessing plants into nuclear bomb-material factories. As the number of these facilities increases, the ability of the agency to fulfill its material accountancy mission dangerously erodes. The IAEA has yet to concede these points by admitting that although it can monitor these dangerous nuclear activities, it cannot actually do so in a manner that can assure timely detection of a possible military diversion - the key to an inspection procedure being a safeguard against military diversions.

    Chapter 5: Edwin S. Lyman "Can Nuclear Fuel Production in Iran and Elsewhere be Safeguarded Against Diversion?"

    [Significant Quantity]

    [Dr. Marvin] Miller [Massachusetts Institute of Technology, in "Are IAEA Safeguards on Bulk-Handling Facilities Effective?", Nuclear Control Institute, Washington, DC, USA, 1990] observed that for large bulk handling facilities, such as the 800 metric ton heavy metal (MTHM)/year Rokkasho Reprocessing Plant (RRP) now undergoing startup testing in Japan, it was not possible with the technologies and practices available at the time to detect the diversion of 8 kilograms of plutonium (1 significant quantity, SQ) - about 0.1 percent of the annual plutonium throughput - with a high degree of confidence. This is because the errors in material accountancy measurements at reprocessing plants were typically on the order of 1 percent -that is, a factor of 10 greater than an SQ. If after taking a physical inventory, the value of plutonium measured was less than expected (on the basis of operator records) by an amount on the order of 1 SQ, it would be difficult to state with high confidence that this shortfall, known as "material unaccounted for" or MUF, was due to an actual diversion and not merely measurement error.

    [Accountancy Verification Goal - Expected Accountancy Capability (E)]
    In the past, the IAEA acknowledged that the 1 SQ detection goal could not be met in practice, and instead adopted a relaxed standard known as the "accountancy verification goal" (AVG), which was "based on a realistic assessment of what then-current measurement techniques applied to a given facility could actually detect." The AVG was based on a quantity defined as the "expected accountancy capability," E, which is defined as the "minimum loss of nuclear material which can be expected to be detected by material accountancy," and is given by the formula

    E = 3.29 sigma A,

    in which sigma is the relative uncertainty in measurements of the plant's inputs and outputs, and A is the facility's plutonium throughput in between periodic physical inventories.

    This formula is derived from a requirement that the alarm threshold for diversion be set at a confidence level of 95 percent and a false alarm rate of 5 percent. Miller estimated that for the RRP, based on an input uncertainty of plus or minus 1 percent (which was the IAEA's value at the time for the international standard for the expected measurement uncertainty at reprocessing plants), the value of E would be 246 kilograms of plutonium, or more than 30 SQs, if physical inventories were carried out on an annual basis, as was (and is) standard practice. This means that a diversion of plutonium would have to exceed this value before one could conclude with 95 percent certainty that a diversion had occurred, and that the measured shortfall was not due to measurement error.

Version: 24 February 2016
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Joachim Gruber