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Why the MOX Approach to Plutonium Disposition is Bad for Non-Proliferation and Arms Control

Steven Dolley

Research Director

March 28, 1997

The "MOX" approach to plutonium disposition---combining warhead plutonium with uranium into mixed-oxide (MOX) fuel for irradiation in commercial nuclear power plants---has been touted as turning "swords into plowshares." Indeed, two major nuclear-electric utilities, Commonwealth Edison and Duke Power, have dubbed their commercial MOX proposal "Project PEACE." But utilizing tons of nuclear-bomb material in a nationwide commercial enterprise would pose grave threats to national security and global stability.

Bungling the Books: MOX Fuel Fabrication Makes Accurate Plutonium Measurements Impossible

MOX fuel is made by converting metallic plutonium "pits" into an oxide powder, mixing that powder with uranium oxide, and fabricating the MOX mixture into small pellets that are loaded into metal rods and formed into fuel assemblies for nuclear power plants. This process involves bulk handling of plutonium by the ton. Making accurate measurements of bulk amounts of weapon material in MOX fuel fabrication plants has proven impossible.

There is clear evidence of this problem. In May 1994, the Nuclear Control Institute disclosed that a major plutonium inventory discrepancy had been building up at Japan's pilot MOX fabrication plant since a new automated line began operating in 1988.1 The Japanese government had asserted that this plutonium, amounting to about 70 kilograms, or more than enough for eight nuclear bombs, was not missing because it had been measured as "hold-up" material---that is, as plutonium that stuck to surfaces and got held up in the plant's process equipment. But such measurements were taken indirectly by assaying devices, and were subject to significant uncertainty, perhaps as large as 30 percent in some instances.2

To deal with the uncertainty, the International Atomic Energy Agency (IAEA) asked Japan to cut open the glove boxes and physically produce and measure the heldup plutonium so that inspectors could verify the plant's inventory. At a reported cost of more than $100 million, and after more than two years of clean-out operations, about 10 kilograms of plutonium (more than a bomb's worth) is still not accounted for.3 Japan thus still fails to meet the safeguards criteria required by the IAEA. Plutonium scrap is also a significant source of measurement uncertainty at the MOX fabrication plant, which has generated about 100 to 150 kilograms of such scrap.4

MOX fabrication plants in Europe, which are under consideration for use to produce warhead-plutonium MOX fuel, have not disclosed the design and operating history of their material control and accounting systems to permit any conclusion by the IAEA about the effectiveness of safeguards at these facilities. The Energy Department's Final Arms Control and Non-Proliferation Assessment makes the following assertion about the accuracy of plutonium measurements in European MOX plants:

Recent standards issued by the European Community's nuclear agency (EURATOM), endorsed by the IAEA, indicate that currently achievable measurement accuracy for plutonium oxide is in the range of 99.9% (for systematic errors). Mixing the plutonium oxide with uranium oxide complicates the task of measuring the amount of plutonium somewhat, resulting in an estimated achievable measurement accuracy of 99.8%.5

This claim is highly misleading because it refers only to EURATOM standards, and offers no evidence of what has actually been achieved in practice.6 Even more misleading is the following claim in the DOE report:

Thus, at a facility handling 5 tons per year of plutonium metal and oxide (such as a plutonium pit conversion facility), the systematic measurement error, or MUF, would not be expected to be less than 5 kilograms per year (based only on the throughput, ignoring the facility's inventory), meaning that material accounting alone would not be expected to be able to detect diversions of less than 15 kilograms over a year's time. [emphasis added]7

Thus, the claim of 99 percent accuracy applies only to a plant's input and output measurements and excludes the inventory in the process stream of the plants, where measurements have an uncertainty range of 25 to 30 percent.8

This controversy over the plutonium holdup problem at MOX fuel fabrication plants holds valuable lessons for the warheadplutonium disposition process. MOX disposal schemes have unacceptable uncertainties and risks built into them that will make it impossible to determine whether all warhead plutonium has been accounted for. Such uncertainty could severely limit the trust nations place in an international nuclear armsreductions and nonproliferation regime predicated upon recycling warhead plutonium as fuel for reactors. Thus, the actual ineffectiveness of safeguards at MOX fabrication plants undercuts a primary goal of the disposition process---preventing reversal of the disarmament process---and should be acknowledged, as such. It should also be acknowledged that the use of cameras and seals (so-called "containment and surveillance systems") are far from foolproof and could be defeated by knowledgable insiders who would exploit measurement uncertainties to divert plutonium from a MOX plant.

The safeguards advantages of immobilization are noted by the U.S. National Academy of Sciences in a study of plutonium disposition options. NAS concluded that fabrication of HLW waste logs would

. . . be easier to safeguard than fabrication of MOX fuel bundles. Monitors would have to confirm only the single step of mixing the plutonium with the HLW. Once that step had taken place, the plutonium would be in an intensely radioactive mix and very difficult to divert. There would be no capability within the vitrification facility for reseparating the plutonium from the HLW. MOX fabrication, by contrast, requires many steps involving largescale bulk handling of plutonium, with inherent accounting uncertainties, and at each step of the process the plutonium remains in a form from which it could be readily reseparated.9

MOX Does Not "Burn" or "Destroy" Plutonium: It's Still There

The MOX option would leave modestly less plutonium in final waste than the immobilization option. However, it is misleading to speak of MOX "burning" of weapons plutonium as if all or even most of the plutonium is consumed during irradiation. In fact, irradiated weapons-plutonium MOX fuel would contain only about 30 percent less total plutonium per unit fuel than fresh MOX.10

However, even these reductions are unlikely to be achieved in practice, because they would require reactors to be loaded with full cores of MOX fuel. No light-water reactor anywhere in the world has been operated with a 100 percent MOX core. Realistically, a light-water reactor (LWR) loaded with a conventional one-third core of MOX fuel---the largest MOX core loading presently achievable---would discharge only about one percent less plutonium than was contained in the MOX fuel originally loaded.11

MOX Does Not "Denature" or "Deactivate" Plutonium: It Can Still Be Used In Bombs

Many MOX proponents emphasize the degree to which the isotopic composition of the weapons plutonium would be altered by irradiation in a reactor as if this factor should be decisive in choosing among disposition technologies. This is an inappropriate criterion by which to assess proliferation risks because it perpetuates a dangerous myth that so-called "reactorgrade" plutonium (the plutonium discharged from nuclear power plants) cannot be used to make workable weapons.

The ability to construct a weapon from reactorgrade plutonium was demonstrated decades ago. It is dangerous even to consider it an open question. In 1990, Hans Blix, directorgeneral of the IAEA, informed our Institute that there is "no debate" on this point in the Safeguards Department of the IAEA, and that the agency considers virtually all isotopes of plutonium, including high burnup reactor-grade plutonium, to be usable in nuclear weapons.12 The U.S. government had declassified this information for the IAEA and foreign governments two decades earlier. In June 1994, U.S. Energy Secretary Hazel O'Leary declassified further details of a 1962 test of a nuclear device using reactorgrade plutonium, which successfully produced a nuclear yield.13

For nuclear-weapon states, conversion of plutonium to reactor-grade would not pose an impediment to rearmament. Weapons-design innovations by the United States and Russia have eliminated the risk that "predetonation" caused by excess neutrons from Pu-240 would reduce the yield or reliability of a their nuclear bombs.14 In a future breakout scenario, the United States (or Russia) could draw on its historical nuclear test data and predictive capabilities to reconfigure weapons and reconstitute a large arsenal, even from plutonium isotopically degraded to reactorgrade by irradiation in MOX. Testing of a design using reactor-grade plutonium probably would not be necessary; but in a future rearmament emergency in which the United States or Russia felt compelled to make prompt use of MOX spent fuel as a source of weapons plutonium, even a comprehensive test ban treaty (CTBT) would not prevent testing. Article 9 of the CTBT allows a member state to withdraw from the treaty after six months' notice if its "supreme interests" are at stake.

Thus, isotopic degradation does not pose a substantial barrier to remilitarization of warhead plutonium, and therefore does not constitute a compelling argument in favor of the MOX option. The National Academy of Sciences, in its comparison of the MOX and immobilization options, found that "[t]he plutonium in the spent fuel assembly would be of lower isotopic quality for weapons purposes than the still weapons-grade plutonium in the glass log, but since nuclear weapons could be made even with the spent fuel plutonium this difference is not decisive." [emphasis supplied]15

(For more details, see "Using Warhead Plutonium as Reactor Fuel Does Not Make It Unusable in Nuclear Bombs," NCI Plutonium Disposition Fact Sheet, March 1997.)

MOX Would Open the Door to a U.S. Plutonium Fuel Industry

The overseas plutonium industry, comprised of such government-run corporations as British Nuclear Fuels Ltd. (BNFL) and COGEMA of France, would love to see the U.S. nuclear power market opened up to MOX fuel and, someday, spent fuel reprocessing. The spent fuel of the more than 100 power reactors in the United States is by far the biggest potential market for these conglomerates. Using MOX fuel for warhead plutonium disposition would help open the U.S. market.

Some elements of the U.S. nuclear industry, and their supporters, would like to see the U.S. move to a plutonium fuel cycle as well. Westinghouse floated a proposal in 1995 that large amounts of U.S. civilian nuclear power spent fuel be reprocessed in the canyons at the Savannah River Site in South Carolina. Last year, Republic Senators added a provision to the nuclear waste bill that would have encouraged U.S. reprocessing, withdrawing it only under pressure. But they haven't given up: an aide to Senate Energy Committee Chairman Frank Murkowski (R-Alaska), speaking about the 1997 nuclear waste bill, said:

If this program is successful, the use of MOX fuel to reduce military plutonium stockpiles could go a long way to improve the political acceptance of the use of similar technology to reduce civilian plutonium stockpiles as an alternative to burial.16

U.S. nuclear industry supporters of MOX want the Nuclear Regulatory Commission (NRC) to approve generic revisions of nuclear power plant licenses to permit use of MOX fuel. If such generic approval is given, licensing of MOX fuel use could not be limited to warhead plutonium disposition: any reactor could go ahead and use MOX fuel made from civilian plutonium.

The MOX Disposition Approach Would Encourage Plutonium Use Worldwide

In its 1993 nonproliferation policy statement, the Clinton administration declared that "the United States does not encourage the civil use of plutonium and, accordingly, does not itself engage in plutonium reprocessing for either nuclear power or nuclear explosive purposes."17 Though use of warhead plutonium does not involve further reprocessing, the MOX option clearly would encourage the civil use of plutonium, which in a number of countries includes reprocessing irradiated MOX fuel. The U.S. Government (or its agents) would be engaging in MOX activities for the first time on a commercial scale, legitimizing the use of MOX and further encouraging reprocessing in civil nuclear power programs.

Such a sea change in U.S. policy would confuse and complicate U.S. nonproliferation diplomacy. It would send the wrong signal to Western Europe, Japan, and other nonnuclearweapon state members of the NonProliferation Treaty (NPT). The NAS study conceptualized this issue as the "Fuel Cycle Policy Signal":

[P]olicymakers will have to take into account the fact that choosing to use weapons plutonium in reactors would be perceived by some as representing generalized U.S. approval of separated plutonium fuel cycles, thereby compromising the ability of the U.S. government to oppose such fuel cycles elsewhere. Conversely, choosing to dispose of weapons plutonium without extracting any energy from it could be interpreted as reflecting a generalized U.S. government opposition to plutonium recycle. Either choice could have an impact on fuel cycle debates now underway in Japan, Europe, and Russia.18

The MOX option would clearly encourage the civil use of plutonium, as Arms Control and Disarmament Agency Director John Holum warned in a memorandum to Energy Secretary O'Leary last November:

I recommend strongly that you reject the hybrid option and select immobilization. . . . U.S. decisions on plutonium disposition are inextricably linked with U.S. efforts to reduce stockpiles as well as limit the use of plutonium worldwide. The multi-decade institutionalization of plutonium use in U.S. commercial reactors would set a very damaging precedent for U.S. nonproliferation policy. In contrast, an immobilization-only alternative would have no proliferation downside for either the U.S. or for influencing Russia, and potentially could have important benefits in supporting our continuing efforts with Russia to secure its stockpiles of weapon-usable material. [emphasis in original]19

If the hybrid option is chosen, these countries [Russia, South Korea, and others] would hear only one message for the next 25 years: that plutonium use for generating commercial power is now being blessed by the United States. No matter how much effort we take in reducing these risks ... the overriding message that we will convey is that civil plutonium use is acceptable.20

The MOX option sends the wrong fuel cycle policy signal in three ways. First, the MOX option effectively declares that plutonium has an asset value, and that the energy contained within it should be viewed as a "national asset" (as the U.S. DOE puts it) or even "national treasure" (as the Russians put it).

Second, the MOX option suggests that a plutonium fuel cycle can be effectively safeguarded, and the use of MOX for weapons plutonium disposition would surely be cited by plutonium advocates as a government "seal of approval" on the process.

Third, the MOX option would be portrayed as giving credibility to the claim that plutonium recycle in lightwater reactors is essential to nuclear waste management. Despite the fact that both unaltered spent fuel and highlevel waste derived from reprocessing produce comparable amounts of penetrating radiation and short-term thermal output,21 reprocessing advocates have seized upon the separation and reuse of plutonium as the sine qua non of effective waste management.

Reprocessing proponents would exploit the use of MOX in the disposition process as proof of a new U.S. government policy on plutonium. The MOX fuel used to irradiate weapons plutonium could be reprocessed later on as a source of plutonium for weapons. The civil plutonium industry, particularly in Japan and Germany, could continue to press for reprocessing of MOX fuel as a way to "eliminate" completely plutonium over hundreds of years. The U.S. warhead-plutonium disposition program should not in any way lend credence to such misleading and misguided efforts.

For More Information:

Nuclear Control Institute, 1000 Connecticut Ave. NW, Suite 804, Washington, DC, 20036. Phone: 202-822-8444. Fax: 202-452-0892. E-Mail: nci@access.digex.net. Plutonium Disposition Web site: http://www.nci.org/nci-wpu.htm.

End Notes

1. "'Astounding' Disrepancy of 70 Kilograms of Plutonium Warrants Shutdown of Troubled Nuclear Fuel Plant in Japan," Nuclear Control Institute, May 9, 1994.Back to document

2. Such inaccuracies are documented in T. K. Li et al. (Los Alamos National Laboratory) and H. Ai et al. (Japan Nuclear Fuel Ltd.), "Evaluation and Development Plan of NRTA Measurement Methods for the Rokkasho Reprocessing Plant." Also see Paul Leventhal, "IAEA Safeguards Shortcomings---A Critique," Nuclear Control Institute, September 12, 1994. For further discussion of the limitations of IAEA safeguards on plutonium, see Marvin Miller, "Are IAEA Safeguards on Plutonium Bulk-Handling Facilities Effective?," Nuclear Control Institute, August 1990.Back to document

3. Mark Hibbs, "Rebuild at Japan's PFPF Plant Will Cost Japan $100-million," NuclearFuel, October 9, 1995, pp. 11-12; Mark Hibbs, "PFPF Holdup Pu Inventory Under 10 kg; R&D Work to Focus on Monju Fuel," NuclearFuel, November 4, 1996, pp. 15-16.Back to document

4. Ibid. At a briefing for public-interest groups, a high IAEA official acknowledged that the IAEA cannot yet assess with much accuracy how much plutonium is contained in scrap at MOX fuel fabrication plants.Back to document

5. U.S. Department of Energy, Office of Arms Control and Nonproliferation, Nonproliferation and Arms Control Assessment of Weapons-Usable Fissile Material Storage and Excess Plutonium Disposition Alternatives ["Nonproliferation Assessment"], January 1997, p. 86.Back to document

6. Nuclear Control Institute made this comment on the draft assessment in November 1996, and a DOE official pledged that evidence to prove the claim would be cited in the final assessment or the claim would be withdrawn. No such evidence was cited, but the claim of safeguards effectiveness remained.Back to document

7. Nonproliferation Assessment, p. 78.Back to document

8. Li et al. & Ai et al., "Evaluation and Development Plan," op cit..Back to document

9. U.S. National Academy of Sciences, Management and Disposition of Excess Weapons Plutonium ["NAS 1994"], 1994, p. 192.Back to document

10. U.S. National Academy of Sciences, Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options ["NAS 1995"], 1995, Table 6-5, p. 270, indicates that a fresh weapons-plutonium MOX fuel element would contain 25 kilograms of plutonium. The same element, after irradiation to a burn-up of 40 megawatt-days per kilogram heavy metal, would contain 18 kilograms of plutonium.Back to document

11. Westinghouse Electric Corporation, Plutonium Disposition in Existing Pressurized Water Reactors, DOE/SF/19683--6, June 1, 1994, p. 2.6-3.Back to document

12. Letter from Hans Blix, Director-General of the IAEA, to Paul Leventhal, NCI, November 1, 1990; "Blix Says IAEA Does not Dispute Utility of Reactor-Grade Pu for Weapons," NuclearFuel, November 12, 1990, p. 8. However, Blix made this statement only after the Nuclear Control Institute challenged assertions by IAEA officials earlier that year that reactor-grade plutonium was unsuitable for use in weapons.Back to document

13. U.S. Department of Energy, Office of the Press Secretary, "Additional Information Concerning Nuclear Weapon Test of Reactor-Grade Plutonium," DOE Fact Sheet released as part of the Openness Initiative, June 27, 1994. The fact that the test occurred and produced a nuclear yield was declassified in 1977. Robert Gillette, "Impure Plutonium Used in '62 A-Test," Los Angeles Times, September 16, 1977, part 1, p. 3.Back to document

14. Marvin Miller, MIT, personal communication to the Nuclear Control Institute, November 24, 1996.Back to document

15. NAS 1995, p. 413.Back to document

16. Gregg D. Renkes, staff director, U.S. Senate Committee on Energy and Natural Resources, "U.S. High-level Waste-Management Policy and the Reprocessing Option," November 1996, p. 4.Back to document

17. White House Fact Sheet, "Nonproliferation and Export Control Policy," September 27, 1993, p. 2.Back to document

18. NAS 1994, p. 149.Back to document

19. John Holum, Director, Arms Control and Disarmament Agency, memorandum to Hazel O'Leary, Secretary of Energy, November 1, 1996. See also Peter Passell, "U.S. Set to Allow Reactors to Use Plutonium from Disarmed Bombs," New York Times, November 22, 1996, p. 1.Back to document

20. Ibid.Back to document

21. U.S. Office of Technology Assessment, Managing the Nation's Commercial High-Level Radioactive Waste, March 1985, pp. 68-73.Back to document

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