Clay Hydration, Drying, and Cracking in Nuclear Waste Repositories

高放废物和乏核燃料地质处置库的设计是核燃料循环中一个尚未完全解决的问题，尽管在过去几十年中取得了重大进展。目前设计的一个关键主题是多屏障概念，即从罐到EBS到低渗透性主岩的几层屏障材料，确保废物的隔离。工程屏障系统（EBS）发挥着重要作用，它必须保持足够的密封能力（即，低水力渗透性、机械完整性），同时暴露于（一）废物释放的热量造成的大的热梯度;（二）由于在废物罐-EBS和EBS-寄主岩石界面处的腐蚀和离子交换反应造成的大的地球化学梯度;以及（iii）由与初始EBS再水化、水蒸发以及随后的通过腐蚀和水解反应在罐-EBS界面处可能产生气体。本项目的目标是开发一种新的多尺度模拟方法，以预测高放废物和SNF地质处置库近场工程粘土屏障的耦合热-水文-机械-化学（THMC）演化。

The design of geologic repositories for high-level waste (HLW) and spent nuclear fuel (SNF) remains an incompletely resolved question in the nuclear fuel cycle despite significant advances over the last several decades. A key theme in current designs is the multibarrier concept, whereby several layers of barrier materials, from canisters to EBS to low-permeability host rock, ensure the isolation of the waste. An important role is played by the Engineered Barrier System (EBS), which must maintain adequate sealing capacity (i.e., low hydraulic permeability, mechanical integrity) around the waste canisters for durations of thousands of years while exposed to (i) large thermal gradients caused by heat released by the waste; (ii) large geochemical gradients due to corrosion and ion-exchange reactions at the canister-EBS and EBS-host rock interfaces; and (iii) large geomechanical gradients driven by capillary stresses associated with the initial EBS rehydration, water evaporation and, later, with the possible generation of gases at the canister-EBS interface through corrosion and hydrolysis reactions. The objective of this project is to develop a new multi-scale simulation approach to predict the coupled thermal-hydrologic-mechanical-chemical (THMC) evolution of an engineered clay barrier in the near field of a geological repository for HLW and SNF.