Evaluation of Nuclear Material Balance by Statistical Analysis of the Material Unaccounted For (MUF)

Evaluating the nuclear material balance is an essential tool that can be used to assess the validity of the operator’s declarations of existing quantities of nuclear material from a facility, with an effect on safeguards agreements, where applicable. In summary, evaluating the nuclear material balance and associated safeguards activities enables the national regulatory authority to identify variations that may indicate deviations. A specific strategy used to detect potential deviations from assessing the material balance is known as "diversion into MUF", where MUF refers to the parameter Material Unaccounted For. It represents the difference between the book inventory and the ending physical inventory at the end of the material balance period. This evaluation is conducted through statistical analysis of the standard deviation of the MUF (σMUF) parameter, using an anonymous Brazilian facility as a case study. The ultimate goal is to implement this analysis within Brazil's control and accounting system, known as e-Gamma. This will enable the system to automatically perform such analyses for all facilities nationwide during each accounting period. This statistical study can be a powerful predictor of diversion, utilizing the σMUF parameter as a valuable resource. It is possible to suggest implementing this evaluation in control and accounting systems to increase efficiency in identifying and resolving discrepancies and anomalies, which is of fundamental importance in improving the reliability of a control system within the national scenario. Considering the international scenario, a country that increases its capacity to verify the accounting of nuclear material under its custody will tend to occupy a position of autonomy among its peers.