This paper describes an experimental and theoretical analysis of the near-field thermal performance of a backfilled disposal vault in which the waste containers are emplaced in boreholes and surrounded by a bentonite-sand buffer. Effects of heat and moisture diffusion on the thermal performance of clay-based buffer and backfills were studied by means of laboratory scale experiments. The bentonite-sand buffer exhibited cracking due to desiccation. The impact of such cracking on the perforamnce of buffer as an engineered barrier is being investigated.
An integrated finite difference computer code ‘TRUCHAM’ was written to analyze the transient heat and moisture flow regime in a disposal vault and was validated by a scale model heater experiment. It is hoped that with proper characterization of the material properties ‘TRUCHAM’ can be employed as a useful tool in assessing the thermal response of the prototype disposal vault. Further work is needed to integrate the effects of heat and moisture on the shrinkage and expansion of clay-based buffer and backfills.