Consideration of hold up for material accountancy in pyroprocessing plant

A safeguards material accountancy usually relies on the accounting analysis of physical inventories at the time of annual physical inventory taking. During that period, the operation process is stopped and cleaned-out to minimize the amount of materials impossible to measure, so called residual hold-up. The way to clean-out the process as well as the material hold-up amount have not yet been investigated in detail, mostly due to the lack of integrated operation schemes and dedicated experimental data. Therefore, the clean-out and holdup issue tends to be regarded one of the major challenges in safeguarding a pyro-processing plant. The purpose of this study is to analyze the material hold-up effect on material accountancy and suggest possible clean-out approaches for safeguarding a pyro-process. Experiences from other similar facilities and our own experimental results with estimated accounting uncertainty estimation seems like the practically achievable range of hold-up and MUF evaluation results. It should be, however, noticed that the margin of accounting measurement uncertainty does not always allow as much residual material. In case of protracted diversion cases, however, the effect by hold-up material worsens the accountancy performance. Therefore, process equipment design and operation scheme should carefully take into account the way how to minimize hold-up materials