Confirmation of the decommissioned status of a centrifuge uranium enrichment plant

Full text: The IAEA has placed increasing priority on the conduct of comprehensive design information verification (DIV), including verification of the declared closed-down or decommissioned status of a nuclear facility. There is a defined process for the life cycle of a nuclear facility from 'operating' to 'closed-down' and closed-down to 'decommissioned'. The process calls for States to submit revised design information accordingly based on changes of the status of the plant. There is little difficulties in verifying a change of status from operating to closed-down since that is mainly a matter of verifying that the nuclear material has been removed from the facility. It has proven much more difficult, in practice, to verify a change in status from closed-down to decommissioned. To assist the IAEA of making a confirmation of the decommissioned status of a plant, lists of 'essential equipment' have been prepared for major plant types. However, the definition in INFCIRC/540 does not state how much of the essential equipment must be removed or rendered inoperable in order to consider that the facility, as a whole, is decommissioned for purpose of safeguards. Japan Support Programme for Agency Safeguards (JASPAS) wants to assist the IAEA in developing guidelines for several types of facility on how much and which pieces of essential equipment must be removed or rendered inoperable in order to accept a State's declaration that a plant has been decommissioned. The confirmation of the decommissioned status of the gas centrifuge enrichment plant is produced as a second report of this task with reference to Japanese decommissioning experiences. The most plausible proliferation scenario using a gas centrifuge enrichment plant, as being decommissioned, is the undeclared operation of the process. The IAEA should verify the status of the decommissioning processes with step by step activities to assure that the process is in an irreversible condition. At the time that the enrichment process is closed down and nuclear material including feed, product and in process inventories of UF6 are removed, routine inspections will stop. If the nuclear material held in the plant is less than 5ekg, the IAEA can continue to carry out one routine inspection in a year and appropriate verification activities through DIV and complementary accesses to confirm the absence of undeclared activities in a plant. After removal of all nuclear material, the plant is still assigned as a 'facility' until the plant loses the capability of enrichment. The capability to restart the isotope separation process may still exist. The term 'rendered inoperable' for a gas centrifuge enrichment plant is the important point of its status during decommissioning taking into account whether the plant lost the capability for isotope separation. That is the point that especially designed equipment and systems including piping works for the isotope separation processes have been removed. The IAEA retains the right and obligation to carry out DIV and to conduct complementary access for confirmation of the decommissioning status during lifetime of facility. Verification activities should be taken by the IAEA to assure the irreversibility of each step of the decommissioning process with appropriate measures e.g., the application of seals and surveillances. For the confirmation, an appropriate arrangement for submissions and updates of decommissioning status is necessary to agree between the SSAC including plant operator and the IAEA. After losing capability for enrichment, the IAEA continues to carry out complementary accesses to confirm the decommissioned status of the plant. Because especially designed equipment, including parts of rotor and rotor itself has a possibility of second hand use, the tracking of the removed equipment is necessary whether the equipment should be dismantled or destroyed. It may be difficult and not very meaningful to attempt to track dual-use equipment and components such the high power electric supply system and frequency changer or generators as they can be used for other purposes, such as non-nuclear use. Unfortunately, the tracking activities of the equipment are outside scope of the safeguards. It is expected that the activity would be formulated in the non-proliferation regime. (author)