Thermal and Radiolytic Gas Generation in Hanford High-level Waste
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چکیده
Mixed radioactive and chemical wastes stored in tanks across the DOE complex generate hydrogen, ammonia, nitrous oxide, and nitrogen by a complex series of radiolytic and thermolytic reactions. Flammable conditions may result when these gases accumulate in the dome space of the waste tanks. A phenomenological model was developed that successfully predicts gas generation rates for many of Hanford’s tanks as a function of waste composition, temperature, and radiation dose rate, based in large part on the results of laboratory studies using actual waste core samples. That model, along with gas monitoring, is used as a guide for selecting dome space ventilation rates that provide an adequate margin of safety. The basic thermal and radiolytic chemistry has been studied extensively over the last decade using simulated and actual Hanford wastes in an effort to understand and predict gas generation rates from Hanford high-level wastes. Predictive models are based on the basic chemical pathways involved in the thermal and radiolytic gas generation. This paper summarizes 1) chemical and radiolytic pathways to gas generation, 2) models for predicting gas generation, and 3) comparisons of predicted hydrogen generation rates to field-measured values for Hanford wastes.
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Project Title : Studies Related to Chemical Mechanisms of Gas Formation in Hanford High - Level Nuclear Wastes
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