Plutonium is a key ingredient in nuclear weapons, making it one of the most dangerous materials in existence. At the end of 1998, there were over 1,350 tonnes (metric tons) of plutonium in the world, or enough for more than 170,000 nuclear weapons. Most of this plutonium - about 1,115 tonnes of it - was produced in civil nuclear power programs in 32 countries (excluding the breeder reactor in Kazakhstan). The estimated amounts of civil plutonium at the end of 1997 and 1998, shown in Table 1, indicate an annual increase of 65 tonnes.
The amount of plutonium discharged annually is expected to decrease in coming years as recycled civil plutonium is fabricated into mixed-oxide ("MOX") fuel and irradiated. Enriched uranium fuel is also being irradiated longer, which leads to less plutonium discharged from power reactors.
Civil plutonium is in two basic forms--in spent (irradiated) fuel, or in separated (unirradiated) form. Unirradiated plutonium may be in pure form, in the process of being fabricated into MOX fuel, or in fresh MOX fuel. Once it has been irradiated, however, the plutonium in MOX fuel, like the plutonium produced when uranium fuel is irradiated, is contained in spent fuel. The plutonium in spent fuel is considered more proliferation resistant, because it is difficult to separate the plutonium from the other constituents of spent fuel.
Table 1 shows how much of the world's civil plutonium is contained in spent fuel and how much is in unirradiated forms. The amount of plutonium in both categories is increasing; roughly 80 percent is in spent fuel.
Table 2 shows the amounts of separated plutonium held by 12 key countries at the end of 1996 and 1997. Most of the figures come from the official public declarations those countries made to the International Atomic Energy Agency (IAEA). Several of the entries in the table are estimates, however, because some declarations are incomplete or ambiguous. In addition, India, Italy and the Netherlands have not made similar declarations of their separated plutonium to the IAEA. Most declarations for 1998 are not yet available; ISIS estimates for 1998 are used in Table 1.
Between 20 and 25 tonnes of plutonium are separated from spent fuel each year, and about 10 tonnes of separated plutonium are fabricated into MOX for use as fuel in light-water reactors. But the fabrication of MOX fuel and its use have not kept pace with the rate of plutonium separation, so the amount of separated plutonium continues to grow. This trend is expected to continue for several more years.
Europe's MOX fabrication capacity is growing, as are the number of power reactors licensed to use MOX. As a result, civil stockpiles of separated plutonium are expected to begin decreasing some time in the early 2000s.
The rate of decrease is difficult to predict. However, even if the commercial separation of plutonium decreases in Britain and France, as expected, and even if Britain opens its already completed commercial-size MOX fabrication facility, the amount of separated plutonium could still be about 150 tonnes by 2010-2015. This is a rough estimate, but it shows that disposing of large amounts of plutonium will be time consuming. It might be disposed of more rapidly if it were immobilized with high-level waste, an option the United States is pursuing to dispose of some of its excess military plutonium.
The world's militaries have significantly less plutonium than civil owners do - some 250 tonnes, or about a quarter of the amount in civil inventories. But more than 90 percent of military plutonium is in separated form - and thus more readily usable in weapons. About 100 tonnes of the military plutonium have been declared excess to military needs by Britain, Russia and the United States.
Table A1 shows ISIS estimates of cumulative plutonium production by country at the end of 1998. The figures were calculated using the methodology described in David Albright, Frans Berkhout, and William Walker's book, Plutonium and Highly Enriched Uranium 1996. Breeder reactors are not included in these estimates. ISIS judges that, without detailed knowledge of plutonium discharges at individual reactors, its estimates by country are uncertain by 10-20 percent, a value greater than that assigned in the book. Uncertainty could not be lowered to less than 5 percent unless each country provided more information about the amount of plutonium discharged in spent fuel, or more information about spent fuel discharges and fuel burnup.
The values in Table A1 are known to be overestimates, because they do not account for the increasing use of recycled plutonium fuel or the relatively rapid radioactive decay of plutonium 241, one of the plutonium isotopes found in civil plutonium. (The other principal isotopes are plutonium 239, plutonium 240, and plutonium 242, all of which have considerably longer half lives than plutonium 241.)
Table A2 corrects for these two cases, at least in the total civil
plutonium estimates. Sufficient information is not available to correct
each country's plutonium inventory.