Invited Presentation in Spent Fuel Waste Storage Technology Annual Meeting, Las Vegas 5/24/2017

Computational thermo-hydro-mechanics of crystalline rock salt for nuclear waste disposal

SeonHong Na, WaiChing Sun

Abstract

Rock salt is one of the major materials used for nuclear waste disposal. The desired characteristics of rock salt, i.e. the high thermal conductivity, low permeability and self-healing is highly related to the crystalline microstructure. Conventionally, this microstructural effect is often incorporated phenomenologically in macroscopic models. Nevertheless, Rock salt is a crystalline material of which the thermo-mechanical behavior is dictated by the nature of crystal lattice and mcriomechanics the slip system. This paper present a model proposed to examine these fundamental mechanisms at the grain scale level. We employ the single-crystal plasticity framework on salt and idealized it as an FCC crystal lattice with a pair of Na+ and Cl- ions as basis. Utilizing an viso-elasto-plastic framework, we capture the existence of elastic region in the stress space and the sequence of slip system activation of salt under different temperature ranges. To capture the intragranular fracture, we introduce an anisotropic phase-field based model to capture the anisotropy of critical energy release rate of a single crystal. Numerical examples demonstrated that the proposed model is able to capture the brittle-ductile transition under various of loading rate, temperature and confining pressure.