by Dr. Jeremy J. Whitlock


Disarmament treaties between the USA and Russia have identified a large quantity of weapons-grade plutonium that is, or will soon become, surplus. The existence of this surplus material is widely recognized as a "clear and present danger" to health and security on this planet. The US Department of Energy (DOE) is pursuing a dual-track approach to managing and reducing the proliferation risk of this material. One method involves the immobilization of the plutonium, mixed with radioactive fission products, in glassified "logs"; the other method involves "burning" the plutonium to make electricity in a nuclear power reactor, after first converting it to plutonium-oxide and mixing it with uranium-oxide ("mixed-oxide" or "MOX" form). Both methods will convert the weapons-plutonium to a "spent fuel standard" -- making it as inaccessible as the plutonium contained in spent civilian reactor fuel. The US DOE has included Canadian CANDU reactors as an option for the "burning" of weapons-plutonium MOX, and is financing a study to explore the feasibility of this concept.

In response to well-publicized opposition to the "MOX" option, in both the global and Canadian contexts (see, for example, www.psr.org/abm.htm or www.ccnr.org/plute_hell.html or www.web.net/~nben/envnews/action/99/pressu.htm" or www.ieer.org/comments/pu-disp/stmt2000.html), the following are ten reasons for keeping it as an option for plutonium disposition:

  1. It is the only option that destroys plutonium. A key report by the U.S. National Academy of Sciences (1994) identifies the continued existence of surplus weapons plutonium -- especially within the former U.S.S.R. -- as a "clear and present danger to national and international security". Using Pu-MOX fuel in current CANDU reactors can destroy (net) up to 70% of the fissile plutonium content (Pu239 + Pu241), and about half of the total plutonium content. Advanced fuel designs (Pu-SiC, Pu-Th) can destroy (net) 94% of fissile plutonium content, and about 75% of the total plutonium content. With reprocessing, 100% destruction can be achieved. The immobilization option, favoured by MOX opponents, maintains the original inventory of plutonium indefinitely.

  2. It is the only option that denatures the remaining plutonium, from weapons-grade to reactor-grade. This further reduces the proliferation risk by making the plutonium less attractive for weapons use (see discussion at http://www.nuclearfaq.ca). In fact, the proliferation risk of weapons plutonium after processing in a CANDU reactor is lower than that of conventional reactor-grade plutonium, since the fraction of fissile plutonium isotopes (mainly Pu-239) can be reduced to about 50% using the MOX option (compared to 60-70% in power reactor spent fuel), and less than 25% using inert-matrix or thorium fuels. In comparison, the immobilization option maintains the plutonium at weapons-grade, and therefore suitable for use in conventional-design nuclear weapons indefinitely. This difference was pointed out by Dr. John P. Holdren, chairman of the U.S. National Academy of Sciences committee that recommended the "dual-track" plutonium dispositioning strategy to the U.S. DOE:

    "[...] neither option is free of proliferation liabilities. The immobilization option has the advantage of not sending an unintended signal about the possible value of the routine use, in civilian power generation, of plutonium recycled by reprocessing spent fuel. But it has the disadvantage of not changing the weapon plutonium isotopically, which means that if Russia or the United States should ever choose to recover the plutonium from the glass -- which they could easily do -- they could reuse the plutonium in new nuclear weapons based on existing designs.

    "Russia and the United States could also recover reactor-grade plutonium that emerges from the MOX option with comparable ease. But because the isotopics are different, weapons using this plutonium would have to be redesigned, which would require nuclear tests. That means the path to reuse from spent fuel would be more difficult technically and politically -- as well as easier to detect -- than reusing weapons plutonium extracted from glass."

    [J.P. Holdren, "Work with Russia", Bulletin of the Atomic Scientists, March/April 1997, pp.42-5]

    (Holdren qualifies his views on "routine plutonium recycling" earlier in the same article, by stating that he sees it as a small risk in comparison with the larger proliferation risk of not pursing the MOX option -- see point number 9 below.)

    In 2000 the NAS published a clarification of the "Spent-Fuel Standard", which further establishes the importance of plutonium isotopic content:

    "If it is assumed that proliferators in all categories will ultimately be capable of obtaining reasonably pure plutonium metal starting from the dispositioned forms -- as we believe to be the case -- then the main intrinsic barriers in this category [final utilization] are those associated with deviation of the plutonium's isotopic composition from 'weapons grade.' "

    [The Spent-Fuel Standard for Disposition of Excess Weapon: Application to Current DOE Options, Panel to Review the Spent-Fuel Standard for Disposition of Excess Weapons Plutonium, Committee on International Security and Arms Control (CISAC), National Academy of Sciences (NAS), National Academy Press, Washington, D.C., 2000]

    This report concludes that plutonium isotopic content, while remaining a proliferation barrier of low to moderate importance which should not, by itself, be used to determine the suitability of various disposition options, is the most important inherent barrier to the re-introduction of dipositioned plutonium into nuclear weapons by a "host" state (the U.S. or Russia). In this category the immobilization option performs the worst of all options considered by the NAS, since it retains weapons-plutonium indefinitely within the host state at full isotopic purity.

    The NAS report also concludes that in terms of providing an inherent barrier to proliferation by "proliferant states" such as Iraq, plutonium isotopic content is roughly equal in importance to the so-called "radiation barrier" - itself a central tenet of the weapons-plutonium disposition programme.

  3. While being destroyed, the weapons plutonium generates electricity. Using MOX technology, roughly 4 million kWh of electricity can be extracted from each kilogram of plutonium destroyed -- enough to supply 150 average Canadian homes for a year. That amount of electricity, from one kilogram of weapons plutonium, would avoid the burning of 40 million cubic feet of natural gas, or 1600 tonnes (1.6 million kilograms) of coal. It would also avoid the release of 2400 tonnes of the greenhouse gas carbon-dioxide, if used to displace natural gas, or 4000 tonnes if displacing coal. Generating electricity from former weapons material is very much a "swords to ploughshares" concept.

  4. Since MOX fuel from weapons plutonium would displace uranium fuel, there would be no net increase in waste produced by the CANDU reactors involved. In fact, since weapons-plutonium MOX fuel is more efficient than current CANDU fuel, there would actually be less waste -- potentially 70% less by volume (i.e. over three times as much electricity can be generated per fuel bundle). The nature of the waste would not be significantly different from that which is currently produced. In general the waste produced from a nuclear power reactor is small in volume and easily controlled, relative to other large power-producing technologies. Nuclear waste can be (and is) indefinitely stored in above-ground, passively cooled and shielded containers. A long-term burial technology has been proposed by Atomic Energy of Canada Limited (AECL), which can dispose of nuclear waste to a level of safety such that there is essentially no radioactive signature at the ground surface, and extended societal awareness of the repository is not required. This technology has been found to be technically safe (but lacking in broad public support) by a Federal Environmental Assessment Review Panel (1998).

  5. The transportation risks are not prohibitive. The Canadian proposal is for the MOX fuel to be manufactured from surplus weapons-plutonium in the country of origin (Russia or the U.S.), and shipped across the Canadian border only in the form of CANDU fuel ready for use. The plutonium would be chemically converted to oxide form and diluted to 2% or 3% in uranium-oxide fuel (hence the term, "mixed-oxide", or MOX). Neither the plutonium, nor its radiation, can escape the fuel in this form, unless the fuel is destroyed catastrophically. To prevent this, the fuel will be shipped in containers qualified for every conceivable kind of transportation risk, including collision, fire, and immersion in water. The MOX fuel itself is a high-temperature ceramic material sealed in metal tubes, designed to withstand the immense temperatures, pressures, and water flows of a reactor core. There have been thousands of shipments of nuclear fuel on Canadian highways over the last four decades, with no release of radioactive material. This record includes several shipments of MOX fuel, en route from off-shore manufacturers to AECL's laboratories. The health risk of the MOX shipments would therefore be low, as would the proliferation risk (due to the dilution).

  6. Having two distinct options available (MOX and immobilization) has the advantage of diversity over a one-track approach. This was one reason why the U.S. National Academy of Sciences made its 1994 recommendation of a parallel approach, i.e., pursuing both MOX and immobilization simultaneously, to the U.S. DOE. This is the program currently underway in the U.S.

  7. MOX technology may be the only approach that Russia will take to manage its surplus plutonium stockpile, since Russia does not favour immobilization. Furthermore, there are concerns about Russia's ability to process plutonium at the required rate in its domestic power reactors, in which case Canada would be able to assist by processing Russian plutonium through its CANDU reactors. This has an added political advantage of providing a transparent, third-party process on "neutral" territory (Japan is also considering accepting Russian MOX fuel).

  8. CANDU reactors have been "burning" plutonium, by design, for almost forty years. This plutonium is created "in situ" by the irradiation of uranium, and in fact CANDU reactors generate about half of their energy from this source. While the isotopic mixture (the ratio of Pu-239 to higher isotopes of plutonium) would be different in weapons-grade MOX fuel, the difference is not enough to require design changes to the CANDU reactor, nor affect the safety. One advantage of CANDU over U.S. LWR reactors, in this respect, is its ability to handle a full-core of MOX fuel, and therefore process the weapons plutonium at a faster rate. Regarding the upcoming MOX tests at AECL's Chalk River Laboratories, AECL has over 25 years of experience with MOX fuel (including the transportation thereof), has itself fabricated 3 tonnes of MOX fuel over this time, and is actually conducting test irradiations of some of this MOX fuel in its NRU reactor at this moment.

  9. The potential for widespread adoption of plutonium-based commercial fuel cycles (a "Plutonium Economy") is strongly dependent upon the economics of uranium vs. plutonium fuel cycles. Uranium is a relatively cheap commodity on the world market, and this situation is not expected to change in the forseeable future. Dr. Frank von Hippel, former assistant director for national security in the White House Office of Science and Technology Policy, writes:

    "Spent-fuel reprocessing is totally uneconomic. The price of natural uranium would have to increase about 20 times before the uranium savings from plutonium and uranium recycle would pay for reprocessing.

    "[...] It is expected that uranium could be recovered from ocean water at less than half of this price."

    [F. von Hippel, "Getting Back to Basics: Controlling Fissile Materials", presented at the sixth Nonproliferation Policy Reform Task Force Meeting, September 13, 1999.]

    Canada is the world's largest supplier of uranium, and in addition, CANDU reactors are based upon a natural-uranium (i.e., zero enrichment) fuel cycle, which has the lowest fuelling costs of any current commercial fuel cycle. In comparison, plutonium fuel cycles are expensive, and only approach viability when the processing cost is either absorbed externally (as in the case of CANDU-MOX fuel using surplus weapons-plutonium), or is used to offset the cost of enriched-uranium fuel cycles in countries without large, domestic uranium resources (as in the case of Japan and parts of Europe). In the current and foreseen environment, therefore, it is not credible that a supply of CANDU fuel made from surplus weapons plutonium would touch off a Plutonium Economy. It is equally difficult to envision how a favourable political climate for plutonium fuel cycles could be fostered within Canada, given the overwhelming economic argument against them. Dr. John P. Holdren, chairman of the U.S. National Academy of Sciences committee that recommended both MOX and immobilization to the U.S. DOE, agrees:

    "Recycling plutonium is much more expensive than making equivalent fuel from low enriched uranium and it is likely to remain so for many decades. This -- even more than nonproliferation policy -- will continue to be a powerful deterrent to plutonium recycle in the nuclear-energy sector.

    "The much bigger danger, which the critics underrate, is that by abjuring reactors for weapon-plutonium disposition, the United States may greatly delay any progress at all toward erecting physical barriers against reuse, in weapons, of the huge separated-plutonium stockpiles that already exist."

    [J.P. Holdren, "Work With Russia", Bulletin of the Atomic Scientists, March/April 1997, pp.42-5]

  10. The CANDU weapons-plutonium MOX concept is highly premature, and therefore it is rational to reserve judgment at this time. There is no official proposal from the world community to dispose of weapons plutonium in CANDU reactors. The Government of Canada has indicated its support for the concept since it is consistent with Canadian disarmament and anti-proliferation policy, but a decision has been deferred until the matter is formally raised outside of Canada. Currently the U.S. and Russia have yet to complete analysis of the economic, safety, technical, and non-proliferation aspects of all options; AECL has yet to complete experiments and analysis that will determine the technical viability of the off-shore CANDU-MOX fabrication process; Canada has yet to conduct regulatory and licensing reviews, as well as a full Environmental Assessment Review with public input (all would follow a formal proposal made by the U.S. and Russia).

    It is imperative that this preparatory work proceed immediately; it is needed before rational decisions can be made and relevant public discussions initiated. According to the recommendation of the U.S. National Academy of Sciences:

    "The current-reactor/spent-fuel and vitrification-with-wastes options are the two leading contenders for plutonium disposition to the spent fuel standard. Because it is crucial that at least one of these options succeed, because time is of the essence, and because the costs of pursuing both in parallel are modest in relation to the security stakes, the panel recommends that project-oriented activities be initiated on both options, in parallel, at once."

    [NAS Committee on International Security and Arms Control, in CISAC-2, July 1995, p. 14).

    As a measure of the concept's premature nature, when the Canadian House of Commons' Standing Committee on Foreign Affairs and International Trade (SCFAIT) held hearings in 1998 on Canadian nuclear weapons policy that included MOX discussions, there was no official proponent of the concept to appear before the Committee. Despite this deficiency, and without input from either AECL or Ontario Hydro, the SCFAIT concluded (in December 1998) that the MOX proposal was "totally unfeasible", and recommended its cancellation. The federal government subsequently challenged and withheld support for this recommendation.

    Final decisions on weapons plutonium MOX should wait until the public, the scientists, and the bureaucrats have had their say, and this is years away.

prepared by

Dr. Jeremy Whitlock
Reactor Physicist
The Canadian Nuclear FAQ:   index.html.

1999 May
updated 2001 June

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