Using a Safeguards Performance Model, an advanced instrumentation scenario has been developed for materials accountability in a UREX+1a reprocessing plant. This scenario takes advantage of new technology to both advance the state of the art in materials accountability and reduce plant construction and operational costs. The model was used to determine the overall standard error of the inventory difference, the instrumentation response to misuse scenarios or off-normal plant processes, and which areas of the plant may be better served with advanced instrumentation. Some candidate new instrumentation is suggested along with the expected improvements in overall accountability. The conclusions of this work are as follows: (1) As little as five additional plutonium in-process measurement points will provide enough information to determine the change of in-process inventory with timetrue near real-time accountability of plutonium can drastically shorten the detection time of a protracted diversion by eliminating the need for a plant flush-out. (2) Additional measurement points will require either rapid, low-error mass spectrometry measurements or rapid on-line non-destructive measurements. Emerging technologies that may be best suited include TARIS (Thermal Atomization Resonance Ionization Spectroscopy) and Ultra-High Resolution Spectroscopy. (3) A rapid non-destructive measurement will also be useful for measuring actinides in spent fuel assemblies, a continuing gap in materials accountancy. (4) Uncertainty still exists as to how well the rest of the minor actinides and some of the key fission products need to be measured. Experimental work is needed to determine the measurement precision of these species in mixed solutions.
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