International research collaborations on deep geological disposition of nuclear waste are a key aspect of the nation’s strategy to investigate disposal design concepts in geologic settings considered by other countries. This report centers on results obtained on THM simulations, reactive transport model development, and engineered barrier system (EBS) material characterization studies. These activities include modeling of field experiments at the Mont Terri URL, Switzerland, and the Horonobe URL, Japan. Modeling of coupled THM processes in the EBS is part of the international DECOVALEX-2015 project including: 1) HE-E Heater Test – Studies of bentonite/rock interaction to evaluate sealing and clay barrier performance; 2) EBS Experiment –thermo-hydro-mechanical-chemical (THMC) behavior of the EBS under heating conditions and interaction with the clay host rock, at Horonobe URL in Japan. Studies also include modeling reactive / diffusive transport of the DR-A (diffusion and retention) borehole experiment in Opalinus Clay, and cement-clay interactions in Engineered Barrier Systems in Opalinus Clay (CI Experiment) at Mt Terri, Switzerland.