Feasibility of constructing a full-scale radioactive high-level waste disposal cell and characterization of its thermo-hydro-mechanical behavior

Abstract

Within the context of deep geological radioactive waste disposal, the French National Radioactive Waste Management Agency (Andra) is conducting a research program including in-situ experiments at the Meuse/Haute-Marne Underground Research Laboratory (MHM URL), which aims to demonstrate the feasibility of constructing and operating a High Level Waste (HLW) disposal facility in the Callovo-Oxfordian (COx) claystone formation and to improve it. ALC1604 experiment is an in-situ heating test reproducing a full-scale HLW disposal cell. Heating devices were placed in the last 15 m of a 25 m long steel cased micro-tunnel to mimic the heat emitted by the HLW packages. The present experiment allows to study the response of the cell and the surrounding rock under thermal loading. More specifically, this experiment studied the thermo-mechanical (TM) behavior of the steel sleeve, equipped with strain gauges, displacement sensors, temperature sensors, etc., and monitored the evolution of the annular space (the gap between the sleeve and the rock). It also studied the thermo-hydro-mechanical (THM) behavior of the near/far field rock through pore pressure and temperature measurements installed in peripheral boreholes. The TM response of the steel sleeve and the THM response of the surrounding rock are numerically reproduced and the chosen THM parameters are compared with previous small-scale in-situ experiments conducted at the MHM URL in order to improve the reliability of the material parameters of the COx. The lessons learned from this experiment has provided valuable feedback towards implementing new full-scale heating experiments consistent with a new benchmark concept.