Using the Sequential Probability Ratio Test for Nuclear Materials Management

The Y-12 National Security Complex in Oak Ridge, TN, maintains the nation’s stockpile of highly enriched uranium (HEU) for use in nuclear weapons. A proposed system for monitoring the HEU is the Continuous Automated Vault Inventory System (CAVIS), which uses radiation and mass detectors. Since radionuclides decay stochastically and normal electronics and computer failures are inevitable, the system can and does experience spurious alarms. In order to reduce the spurious alarms and their associated costs, CAVIS operators require a system to monitor the monitoring system. This system alerts operators and security personnel in the event of an actual alarm, and it will assist operators in diagnosing and correcting false alarms. The system of choice for this task is an expert system, using a knowledge base to diagnose and remedy system malfunctions. This expert system requires information on which to base its decisions, and thus uses a feature extraction system to provide it the pertinent data. This feature extraction system uses the Sequential Probability Ratio Test (SPRT) to examine the radiation detector data and identify departures from the expected signal characteristics. The SPRT thus proves useful in the management of nuclear material.