TIMELY DETECTION OF MATERIALS LOSS

Timely detection of materials loss from a nuclear facility is achieved by combining nearreal- time materials accounting principles with sequential statistical testing procedures. This paper compares several sequential procedures using expected time to detect materials loss and the probability of detecting an abrupt loss as measures of performance. Test procedures considered are the sequential probability ratio test, Page's test, and a modified Page's test. All of these tests treat the problem of detecting materials loss as one of testing the hypothesis of no materials loss against the hypothesis that materials loss has occurred. These sequential procedures are appropriate for timely loss detection because they allow a decision as each observation is obtained and have an expected time to detection that is less than fixed-length tests. Simulated materials balance data are used to select the sequential tests that are best against uniform losses and against an abrupt loss.