The Multi-Detector Analysis System

The Multi Detector Analysis System (MDAS) is being developed at the Idaho National Engineering and Environmental Laboratory for characterization of spent nuclear fuel, transuranic waste, and other fissile material. The system is designed to measure fissile material quantities, radiation source term, and fissile isotopic inventories without foreknowledge of the waste type or packaging matrix. MDAS uses a large array of detectors to measure the time signature and energies of both neutrons and gamma rays emitted from the prompt fission process of an active assay. Detection uses fast, nanosecond coincidence timing methods to enhance the detection probability of prompt radiation from the fission process over the high radiation background from long-lived decay products in the waste. The spectroscopic analysis of these prompt fragments, along with proton and mass conservation rules, allows direct measurement of the fissile isotopics without need for model-dependent calculations. New to the MDAS development is the acquisition of a linac neutron generator that supplies up 1010 neutrons per second as the active assay source. Also, a central shield ring used for waste handling and shielding has seen the addition of a graphite reflector to maximize the neutron interaction time. Various other modifications to the electronics and data acquisition system will be presented. In addition to new components, much progress has been made in the basic research of the prompt fission process in transuranics of interest for waste disposition. New results will be presented showing the fission product yields and how these are used in conjunction with the MDAS to characterize unknown waste.