This paper presents a study on the application of the limit-state meth
od for probabilistic multiphase pow modeling. The subsurface multiphas
e flow and heat transport simulator, TOUGH2 (Pruess, 1991), is combine
d with a computer shell for reliability analysis, CALREL (Liu et al.,
1989). As applications of the combined code, the site at Yucca Mountai
n, Nevada for a potential high-level radioactive waste repository is m
odeled under assumed conditions. The probability distributions of vari
ous performance functions (liquid saturation, travel time, and flux) a
re calculated for statistically described infiltration rate and matrix
hydrogeologic parameters. Numerical experiments indicates that the li
mit-state method compares fairly well with, and thus can be used as an
alternative to, the Monte Carlo method for probabilistic multiphase f
low simulations.