An Electronics System for Transuranic Waste Assays

A slagging pyrolysis incinerator has been proposed to reduce the volume of stored transuranic (TRU) waste material. Reduced volume is achieved by burning combustibles and melting nuclear material along with soil to form a glass-type slag containing the (TRU) waste. Monitoring incoming waste and outgoing slag for TRU material is necessary to prevent the accumulation of a critical mass of fissionable material. This report describes the electronics developed for a fast TRU waste assay system using photon interrogation. The system uses a pulsed electron beam from a linear accelerator to produce a high-energy photon burst, termed the "gamma flash", from a metallic converter. The photons induce fission in the TRU. A high-rate counting system is used to relate the production rate of photon induced neutrons to the amount of fissile material present in the waste. The basic requirements for the system are a high count rate capability and rapid "gamma flash" recovery. We have achieved count rates of 4×105 counts per second with a 20% deadtime correction, and "gamma flash" recovery within 30 microseconds with the accelerator operating at 16 MeV, 500 mA, and a 2 ¿s wide pulse at a 60 Hz rate. Future plans include the addition of hardware and software for automatic, on-line assay analysis.