Mechanisms and Kinetics of Organic Aging in High-Level Nuclear Wastes.

Autrey, S. T. ; Camaioni, D. M.

Technical Information Center Oak Ridge Tennessee

关键词: High-level radioactive wastes;    Reaction kinetics;    Thermal analysis;    Aging;    Organic compounds;   

RP-ID  :  DE2004833262

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

The goal of this project is to develop a fundamental understanding of organic aging and to assemble a model that describes and predicts the thermal and radiolytic aging of organic compounds in high-level wastes (HLW). To reach this goal, we will measure kinetics and elucidate products and mechanisms of organic reactions occurring under conditions of waste storage, retrieval, and processing. Initial emphasis will be placed on studying thermal effects, because organic reaction mechanisms and effects of varying conditions are uncertain, and because we benefit from collaborations with earlier Environmental Management Science Program (EMSP) projects that have worked on radiation effects. Organic complexants are of greatest concern regarding both safety and pretreatment because they have been found to degrade to gases, combust in dry wastes, and interfere with radionuclide separations. Therefore, efforts will focus on studying the reactions of these organic chemicals and associated degradation products. In preliminary work, the authors have used mechanistic kinetic modeling techniques to successfully model the radiolytic degradation of formate to carbonate in HLW simulants. The research will continue development of the model using an iterative process that measures degradation products and kinetics of increasingly complex molecules while adapting the model to reproduce the results each step of the way. Several mechanistic probe experiments have been designed to learn the fundamental mechanisms that operate during thermal degradations so that thermal and radiolytic processes may be integrated within the model. Key kinetic data and thermodynamic properties relating to thermal reactivity will also be acquired so that rate-controlling and product-forming reactions can be predicted. Thermochemical properties of key intermediates will be experimentally and/or theoretically determined to facilitate mechanism verification, structure/reactivity correlation, and prediction of reaction rates. We expect a comprehensive understanding of organic reactivity in HLW will accrue from the work. This understanding will be embodied in organic reaction models capable of predicting distributions of species, including gases, with respect to time, temperature, and radiation history. These models will assist waste management decisions by predicting impacts of organic chemicals on safe storage, waste retrieval, and pretreatment of HLW.