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Senior Fellow, Carnegie Endowment for International Peace
April 15, 2019
IAEA Begins Monitoring of HEU Conversion from U.S. Nuclear Stockpile
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THE INTERNATIONAL Atomic Energy Agency (IAEA) began monitoring the conversion of weapon usable uranium from the U.S. nuclear stockpile on December 1 at the Department of Energy's (DOE's) Portsmouth Gaseous Diffusion Plant in Piketon, Ohio. Although the international monitoring body is safeguarding the downblending of 600 kilograms of Soviet highly enriched uranium (HEU) brought in 1994 to the United States from Kazakhstan in "Operation Sapphire," it has never before overseen the demilitarization of fissile material produced for the U.S. nuclear stockpile. Using video cameras, sealed measurement devices, tamper resistant seals and isotopic scanning devices, as well as random inspections, the agency will verify the conversion of HEU to low enriched uranium (LEU), a form suitable for use in civilian power plants, but which cannot be used to produce a nuclear explosion.

Since 1995, DOE has been monitoring the downblending of Russian HEU that is being purchased for resale by the U.S. government owned (soon to be privatized) United States Enrichment Corporation (USEC) and has been adding verification measures to insure the Russian HEU actually comes from dismantled weapons. The new U.S. IAEA program—started at Washington's initiative—will provide a less intrusive method of verifying the elimination of a small portion of U.S. excess HEU on an international basis, but will not determine the origin of the material.

The HEU conversion at Portsmouth is carried out by blending highly enriched uranium hexaflouride gas with gas of lesser enrichment until a level of 3 to 5 percent uranium 235 is reached. The IAEA's role is first to verify the quantity of weapon grade material that goes into the process and then second to ensure the quality—in terms of enrichment—of what comes out. Once the blending process is completed, agency monitoring of the LEU output ends.

Energy Secretary Federico Peña announced the start of the agency's verification activities on December 1 at the National Press Club in Washington. The IAEA is already monitoring the material balance of 12 tons of excess U.S. weapon usable material at three DOE facilities, and the Clinton administration has declared its intention to eventually place all 226 tons of excess U.S. fissile material (HEU and plutonium) under agency safeguards.


Larger Goals

Energy and IAEA officials hope the program will accomplish more than just diluting a few tons of fissile material. At the program's announcement, Secretary Peña stated the IAEA monitoring will prove to other countries that the United States is adhering to President Clinton's pledge to make the elimination of excess fissile material irreversible, and will complement negotiations underway since September 1996, among Moscow, Washington and the IAEA on a trilateral accord to allow the agency to monitor U.S. and Russian stocks of excess nuclear weapons material.

According to Berhan Andemicael, the IAEA's chief liaison to the UN, the Portsmouth program will enable the agency to try out new techniques and procedures that may be applicable for use in its international safeguards activities, provide new experience in monitoring enrichment plant operations, and offer the agency a foothold in the field of monitoring disarmament in nuclear weapon states.

Some observers have noted that, unlike the U.S. Russian blending arrangement, the U.S. IAEA program provides no way of knowing whether the HEU being converted at Portsmouth comes from nuclear weapons, and cannot prevent the substitution of HEU from reserves or other sources. In response, DOE has argued that all the excess HEU being converted to LEU is from defense stocks and is suitable for use in nuclear weapons, even though not all of it actually comes from dismantled warheads.

Of the total 174 tons of U.S. excess HEU, 161 tons is in the form of metal, oxide or beryllium alloy, and will probably be downblended at commercial facilities other than Portsmouth, pending arrangement of contracts between commercial LEU dealers, USEC and DOE. The IAEA will be invited by Energy to monitor these additional operations, with DOE offering to pick up the agency's costs, as it is doing with the Portsmouth program.