Ending the Production of Fissile Material for Nuclear Weapons: Section VII

VII. Reducing Stockpiles of Military Fissile Material

Making nuclear arms reductions permanent will require that more information is made available about military stocks of fissile material and that steps are taken to reduce these stocks in such a manner that they cannot be easily re-used to assemble nuclear weapons or other explosive devices.

Providing More Information

Making nuclear activities more open to scrutiny by governments and international agencies is an accepted condition in most countries. Making civil nuclear programs more open is a central goal of International Atomic Energy Agency (IAEA) safeguards, where, for example, countries allow international inspectors to verify that stocks of peaceful nuclear material are not diverted to nuclear explosive purposes. The decision by states with large civil plutonium recycle programs to declare information about their stocks under the Guidelines for the Management of Plutonium have increased the transparency of civil stocks of separated plutonium (see table VI.3).

Governments have provided far less information about their military stocks and production programs. To date, the steps that have been taken include unilateral measures by the United States and United Kingdom and proposed bilateral exchanges of information between the United States and Russia.

Britain and the United States have unilaterally declared some information about their military fissile material stocks. For example, in February 1996, the United States released a report providing information about U.S. plutonium stocks, production, acquisition, and use. A detailed, unclassified report on highly enriched uranium (HEU) production is to be released soon.
In 1998, Britain released aggregate totals of its fissile material stocks. Britain also announced that it would compile reports on the historical production, acquisition and use of fissile materials that are to be similar to the U.S. reports.

In addition to these unilateral declarations, several U.S. - Russian bilateral initiatives have been proposed. In particular, the United States and Russia have declared their intent to exchange information about their nuclear weapons and fissile material stocks. For example, in May 1995, U.S. President Bill Clinton and Russian President Boris Yeltsin pledged "to establish as soon as possible concrete arrangements for enhancing transparency and irreversibility." Furthermore, the Presidents affirmed "the desire…to exchange detailed information on the exchange of information about aggregate stockpiles of nuclear warheads [and] stocks of fissile materials…on a regular basis." However, efforts to fulfill these pledges have failed.

In March 1997, Clinton and Yeltsin announced that measures related to strategic warhead inventories would be included in the next Strategic Arms Reduction Treaty (START III) negotiations. As part of a joint statement on the parameters of the START III talks, Clinton and Yeltsin agreed that the treaty would include "measures relating to the transparency of strategic nuclear warhead inventories and the destruction of strategic warheads." Clinton and Yeltsin also "agreed that the two sides will consider the issues related to [the] transparency in nuclear materials" during the negotiations. If fulfilled, these exchanges would mark a significant step forward from past bilateral arms control agreements, which focussed primarily on launchers.

Reducing Military Fissile Material Stocks

As nuclear arms reductions progress, the United States and Russia are finding that they possess far more fissile material than they need to sustain current or planned nuclear force structures.

Declaring and Placing Excess Materials Under International Verification. Both countries have declared some of their military stocks to be excess. The U.S. declaration includes 226 tonnes of fissile material, including 174 tonnes of HEU (of various enrichments) and 52 tonnes of plutonium. The Russian declaration includes "up to" 500 tonnes of HEU and "up to" 50 tonnes of plutonium that "becomes available through the disarmament process."

Britain has also declared some of its military stocks to be excess. In 1998, it declared 4.4 tonnes of plutonium to be excess, but it has not declared any HEU to be excess.

In total, up to 40 percent of the military plutonium and up to one-third of military HEU stocks have been declared excess (see table VI.4).

Some of these excess materials have been placed under international safeguards. Through the end of 1998, the United States has placed 12 tones of fissile material under voluntary IAEA safeguards. An additional 15 tonnes of plutonium and 50 tonnes of HEU have also been offered for some form of international verification at a future date. The excess British material is to be placed under Euratom safeguards. Russia has not placed any materials under international safeguards.

The need to place excess materials under international safeguards or some other form of verification controls must be balanced with the need to protect sensitive information about nuclear weapons design from international inspectors. To strike this balance, the United States, Russia, and the IAEA have begun a "Trilateral Initiative," launched in September 1996, to "define the verification measures that could be applied at Russia’s Mayak fissile material storage facility…and at one or more US facilities," where excess "weapon-origin fissile materials" will be stored. After two years of conceptual development, the three parties are now beginning to test prototype equipment. The parties also need to develop the different verification approaches to be applied at specific facilities where excess materials would be stored.

The parties to the Trilateral Initiative are also seeking to develop a model verification agreement, which would form the basis for future bilateral agreements between the IAEA and each weapon state to verify weapon-origin fissile materials. The proposed model agreement is to be more restrictive than current voluntary offer agreements; once materials are submitted, they would remain under IAEA verification until they are determined to be unusable for the manufacture of nuclear weapons. Options to fund the verification of classified fissile materials are also being considered in the talks.

Disposition of Excess Fissile Material. Excess fissile material must be disposed in a manner that minimizes the risk that it can be reused or stolen. HEU disposition is relatively straightforward; it can be blended down by mixing it with LEU, depleted, or natural uranium until it is no longer suitable for nuclear explosives. Both the United States and Russia are blending down excess HEU in this way. Under a 20-year purchase agreement, Russia is blending down 500 tonnes of weapon-grade HEU to LEU and selling the LEU to the United States. In exchange Russia is receiving both monetary payments and compensation in the form of natural uranium, which it can sell on the world market. Approximately 50 tonnes of weapon-grade uranium had been blended down and transferred to the United States by the end of 1998. In 1998, 24 tonnes were scheduled to be blended down but only 14.5 tonnes were blended. Thirty tonnes per year are planned for 1999 through 2001, when the current schedule expires.

The United States is similarly blending down much of its own excess HEU. By the end of 1998, 13 tonnes of HEU had been "downblended" at the Portsmouth Gaseous Diffusion Plant. Of this quantity, 3.5 tonnes were blended to LEU under IAEA verification. The United States plans to transfer an additional 50 tonnes of HEU to the United States’ Enrichment Corporation (USEC) for downblending by 2003, and it has agreed to transfer 38 additional tonnes to the Tennessee Valley Authority sometime in early in the next decade. While disposition plans for the remaining excess HEU have not be finalized, it is expected that approximately 18 tonnes contained in spent fuel and other impure forms will be processed and disposed of as waste.

Unlike HEU disposition, it is far more difficult to find an acceptable plutonium disposition plan. Plutonium presents a higher risk of radiation exposure then uranium, making it more problematic to store, process, and transport. Plutonium from weapons cannot be blended down to a lesser grade since all grades of plutonium can be used to make nuclear weapons.

The United States and Russia have agreed that plutonium disposition technologies should meet the "spent-fuel standard," which would render the military-origin plutonium as unattractive for use or diversion as the plutonium found in spent commercial nuclear fuel.

Russia has expressed its preference to dispose of its excess plutonium by mixing plutonium oxide with uranium oxide and burning the resulting mixed-oxide (MOX) fuel in both light water power reactors and breeder reactors (see sections II and III). Russia has identified several reactors capable of burning MOX fuel and has suggested building more if necessary. However, Russia lacks a facility for converting plutonium into an oxide form and for fabricating MOX fuel.

The United States and other countries are considering ways to assist Russia to dispose of its excess plutonium. The focus of U.S. efforts has been on the construction of a plutonium conversion facility in Russia. In mid-1998, the U.S. and Russia finalized a five-year deal to engage in small-scale tests and demonstrations, proceeding to pilot-scale projects "as soon as practical." At their September 1998 summit, Presidents Yeltsin and Clinton pledged to negotiate a bilateral agreement that will lay out the concrete steps for plutonium disposition and govern their future cooperation in this area. The U.S. Congress has appropriated $200 million to support the U.S.-Russian initiatives, although the September 1998 summit statement indicates that financing from additional countries will be expected. Germany and France have also discussed providing a MOX fabrication facility to Russia, although many technical and financial details remain unresolved.

Unlike Russia, the United States has adopted a "dual-track" plutonium disposition policy. On one track, the United States would burn much of excess plutonium in MOX fuel in commercial power reactors. On the second track, known as the immobilization option, the United States would seal cans of plutonium ceramic inside large canisters filled with vitrified high-level waste. In December 1998, the United States has proposed to build both a pit conversion plant and a MOX fabrication plant at the Savannah River Site. Immobilization would also take place at Savannah River. Final disposition under both options would involve placing spent MOX fuel or vitrified material in a geologic repository. Neither track is expected to be ready to begin operations before the middle of the next decade.