WIPP (Waste Isolation Pilot Plant) Simulated (Defense High-Level Waste) DHLW Tests: Status and Initial in Situ Backfill Thermal Conductivities

摘要

Several series of waste package performance technology experiments for simulated defense high-level waste (DHLW) packages have been emplaced and put into active operation at the Waste Isolation Pilot Plant (WIPP) facility. These experiments involve 18 full-size DHLW packages emplaced in heavily instrumented vertical boreholes in the salt drift floor. These tests have been in heated operation for over ten months now; the planned test duration is 3 to 7 years. A major purpose of these experiments is to evaluate the in situ materials performance (i.e., degradation or alteration) of various waste package components: metal canisters and overpacks, backfill materials, nonradioactive DHLW glass, and installed instrumentation. These evaluations are being performed under both near-reference and overtest or accelerated-aging repository conditions. This paper describes the current status of the WIPP simulated DHLW experiments, and presents initial thermal conductivity results derived from in situ themocouple (temperature) data. Current in situ backfill thermal conductivities range from 0.28 to 0.43 W/m- deg C for bentonite/sand backfills and 1.12 W/ deg C for crushed salt backfill, depending on maximum waste package system temperature(s). Preliminary modeling calculations of thermal conductivity have also been performed using the SINDA and COYOTE codes. The numerically derived values are generally in good agreement with the experimentally measured values, except for the first several days after experiment (heater) turn on. (ERA citation 11:019249)