Overview of total system model used for the 2008 performance assessment for the proposed high-level radioactive waste repository at Yucca Mountain, Nevada

•The models indicated below associated with four scenario classes are described: (i) nominal conditions, (ii) early waste package (WP) and/or early drip shield (DS) failure, (iii) igneous events, and (iv) seismic events.•Models for (i) multi-scale thermal hydrology and engineered barrier system (EBS) thermal-hydrologic environment, (ii) EBS physical and chemical environment, (iii) WP and DS degradation, (iv) drift seepage and drift wall condensation, and (vi) waste form degradation and mobilization.•Models for processes specific to (i) early WP and DS failures, (ii) intrusive and eruptive igneous events, and (iii) seismic ground motion and fault displacement events.•Models for (i) climate analysis, and (ii) land surface infiltration and associated unsaturated zone flow.

A summary is presented for the total system model used to represent physical processes associated with the seven scenario classes (i.e., nominal conditions, early waste package (WP) failure, early drip shield (DS) failure, igneous intrusive events, igneous eruptive events, seismic ground motion events and seismic fault displacement events) considered in the 2008 performance assessment for the proposed repository for high-level radioactive waste at Yucca Mountain, Nevada. The total system model estimates dose to an exposed individual resulting from radionuclide movement through the repository system and biosphere. Components of the total system model described in this presentation include models for (i) climate analysis, (ii) land surface infiltration and associated unsaturated zone flow, (iii) multi-scale thermal hydrology and engineered barrier system (EBS) thermal–hydrologic environment, (iv) EBS physical and chemical environment, (v) WP and DS degradation, (vi) drift seepage and drift wall condensation, (vii) waste form degradation and mobilization, (viii) water and radionuclide movement in the EBS and underlying unsaturated and saturated zones, (ix) radionuclide movement in the biosphere and resultant human exposure, and (x) processes specific to early WP and DS failures, intrusive and eruptive igneous events, and seismic ground motion and fault displacement events.