Changes of the calculation equation for σMUF

The error variance (σMUF2) of the material accountancy for the material balance is used for evaluating the MUF of the conventional material accountancy and the near real time material accountancy (NRTA). The σMUF2 calculated by the error propagation using the material accounting data and the measurement error. The error propagation equation of σMUF2 written on the text of 'The statistical concepts and technique for IAEA safeguards (IAEA/SG/SCT5)'. There are some assumptions in order to simplify the equation. These assumptions are available in the assessment of the facility design. However when the σMUF2 of the actual MUF is calculated, it is necessary to drop some assumptions and modify the adapted equation. Furthermore, because the material balance is more frequently taken for NRTA, the inventory of all times cannot be always re-measured at each time. To be solved the matter, the error propagation equation has to be modified. For a reprocessing plant which has material in solution, the equation has been improved to obtain more exact equation. In this paper we present the changes of the error propagation for σMUF2 and explain the features. (author)