The laboratory conducts research on the technology improvement on safety issues which occurred in the operation, repair, and maintenance of nuclear power plants by means of direct computer calculations and/or the thermo-hydraulic simulation codes. The researchers also simulate virtual severe accidents, so that they can estimate the effects of uncertain physical phenomenon in reactor safety. The researchers are developing the quantitative methods by establishing mathematical models to assess the risk of the nuclear power plants quantitatively using Probabilistic Safety Assessment (PSA). The new methods for management sciences using PSA technology include stochastic models, optimization, accident simulation, decision analysis, and decision theory method.