Safeguards-related consideration of the conversion of unirradiated plutonium to metallic form

The process of developing integrated safeguards (IS) involves the re-examination of certain basic safeguards parameters, in particular those associated with timeliness. Initial consideration focussed on timeliness goals for irradiated fuel, but more recently discussion has extended to include these parameters as they relate to unirradiated plutonium, particularly the plutonium contained in fresh mixed oxide (MOX) fuel. In this paper publicly available information has been used: a) in describing the kinds of process which could be used to convert unirradiated plutonium in various forms, in particular fresh MOX fuel assemblies and their components, to plutonium metal suitable for use in a nuclear device (i.e. the processes required to recover and dissolve MOX, to separate plutonium from a mixed plutonium-uranium solution, to purify that plutonium and convert it first to plutonium oxide and then to plutonium in metallic form); b) in assessing the requirements for these various processes, both in terms of the key equipment and non-nuclear materials that would be involved and also operational considerations (e.g. issues of radiation protection and contamination - including the potential release of radioactivity to the environment, and criticality safety); c) in estimating the time that would be required for such processing, the time taken for each individual process step and also, importantly, the time for the process as a whole to be completed successfully; and, d) in identifying possible indicators of undeclared processing of unirradiated plutonium, both in terms of the material, equipment and other resources required as input to such processing and also possible releases (e.g. of radioactive material) from the processing; e) in discussing the feasibility and possible detectability of the process as a whole. The conclusions from this assessment are that: considerable nuclear sophistication would be required to ensure successful operation of the various processes involved, but that none of the individual stages pose technical problems which, given such expertise, would be insurmountable; much of the equipment and (non-nuclear) materials required are now also used outside the nuclear industry and none of these requirements could be described as both an outstanding indicator of and essential to the process; and, although the sum of the various process requirements would not be trivial, the recovery of plutonium metal in a form suitable for use in a nuclear device from a MOX fuel assembly could, at least in theory, take as little as two to four weeks (i.e. very much consistent with current figures for conversion time)