Thermal Modeling of the Buffer Around Nuclear Waste Repository

Abstract

The safe and rapid disposal of radioactive is an issue of great importance. The leakage from radioactive wastes should be prevented. In the storage of nuclear wastes (radionuclides), the wastes are regularly placed in a sealed, gas and water-free copper container called a canister. In order to prevent the canister from being damaged by a movement in the bedrock or by dangerous substances that may be present in the groundwater, it is covered with a buffer material. Some countries use multiple barrier systems to isolate the waste. Here comes the bedrock that acts as the primary buffer, followed by the engineered barrier system that surrounds it. While the primary buffer material here is the bedrock itself, the secondarily engineered barrier system is the materials positioned between the canister and the bedrock consisting of bentonite or sand-bentonite mixture. In this study, 10% bentonite-90%sand mixture was chosen and the thermal modeling of sand-bentonite mixture as a buffer material around the nuclear waste landfill was performed using the Code Bright Program. In order to use in the analyses, the thermal conductivity values of the mixture and other necessary thermal parameters were measured. At the end of the analysis with 100-years final interval value, it was determined that the temperature in the canister reached 197.96 ℃, and 111.48 ℃ in a part of the green colored zone where the 10B-90S mixture was used as a buffer.