A materials management system is described for safeguarding special nuclear materials in a fuel-reprocessing plant. Recently developed nondestructive-analysis techniques and process-monitoring devices are combined with conventional chemical analyses and process-control instrumentation for improved materials accounting data. Unit-process accounting based on dynamic material balances permits localization of diversion in time and space, and the application of advanced statistical methods supported by decision-analysis theory ensures optimum use of accounting information for detecting diversion. This coordinated safeguards system provides maximum effectiveness consistent with modest cost and minimum process interference. Modeling and simulation techniques are used to evaluate the sensitivity of the system to single and multiple thefts and to compare various safeguards options. The study identifies design criteria that would improve the safeguardability of future plants.