RADIATION EFFECTS IN NUCLEAR WASTE MATERIALS

[摘要] The objective of this research was to develop fundamental understanding and predictive models of radiation effects in glasses and ceramics at the atomic, microscopic, and macroscopic levels, as well as an understanding of the effects of these radiation-induced solid-state changes on dissolution kinetics (i.e., radionuclide release). The research performed during the duration of this project has addressed many of the scientific issues identified in the reports of two DOE panels [1,2], particularly those related to radiation effects on the structure of glasses and ceramics. The research approach taken by this project integrated experimental studies and computer simulations to develop comprehensive fundamental understanding and capabilities for predictive modeling of radiation effects and dissolution kinetics in both glasses and ceramics designed for the stabilization and immobilization of high-level tank waste (HLW), plutonium residues and scraps, surplus weapons plutonium, other actinides, and other highly radioactive waste streams. Such fundamental understanding is necessary in the development of predictive models because all experimental irradiation studies on nuclear waste materials are ''accelerated tests'' that add a great deal of uncertainty to predicted behavior because the damage rates are orders of magnitude higher than the actual damage rates expected in nuclear waste materials. Degradation and dissolution processes will change with damage rate and temperature. Only a fundamental understanding of the kinetics of all the physical and chemical processes induced or affected by radiation will lead to truly predictive models of long-term behavior and performance for nuclear waste materials. Predictive models of performance of nuclear waste materials must be scientifically based and address both radiation effects on structure (i.e., solid-state effects) and the effects of these solid-state structural changes on dissolution kinetics. The ultimate goal of this project is to provide the scientific understanding and rationale for developing improved glass and ceramic waste forms and to develop scientifically-based predictive models of the near-term (<500 years) and long-term performance of nuclear waste forms and stabilized nuclear materials. Studies under this project have focused on the effects of ionization and elastic collisions on defect 3 production, defect interactions, diffusion, solid-state phase transformations, gas accumulation and dissolution kinetics using actinide-containing materials, gamma irradiation, ion-beam irradiation, and electron-beam irradiation to simulate the effects of a-decay and b-decay on relevant nuclear waste materials. This project has exploited both experimental and computer simulation methods to characterize damage production processes, damage recovery processes, defect migration energies, defect interactions, evolution of microstructure, phase transformations, and dissolution mechanisms, all of which ultimately affect the structural integrity and dissolution kinetics of nuclear waste materials. New atomic-level simulation capabilities, which crosscut both spatial and temporal scales, could lead to more sophisticated predictive capabilities in the future.

[发布日期] 2000-12-31 [发布机构] Pacific Northwest National Laboratory (U.S.)

[关键词] 63 Radiation, Thermal, And Other Environmental Pollutant Effects On Living Organisms And Biological Materials;12 Management Of Radioactive Wastes, And Non-Radioactive Wastes From Nuclear Facilities;Irradiation;Waste Forms;Actinides