A DEMONSTRATION OF VARIANCE AND COVARIANCE CALCULATIONS USING MAVARIC AND PROFF*

Good decision-making in materials accounting requires a valid calculation of control limits and detection sensitivity for facilities handling special nuclear materials (SNM). A difficult aspect of this calculation is determining the appropriate variance and covariance values for the terms in the materials balance (MB) equation. Computer software such as MAVARIC (Materials Accounting VARIance Calculator) and PROFF (PROcessing and Fuel Facilities calculator) can efficiently select and combine variance terms. These programs determine the variance and covariance of an MB equation by first obtaining relations for the variance and covariance of each term in the MB equation through propagating instrument errors and then substituting the measured quantities and their uncertainties into these relations. MAVARIC is a custom spreadsheet used with the second release of LOTUS 1-2-3.** PROFF is a stand-alone menu-driven program requiring no commercial software. Programs such as MAVARIC and PROFF facilitate the complex calculations required to determine the detection sensitivity of an SNM facility. These programs can also be used to analyze materials accounting systems.