Three-dimensional radiation shielding analysis around the core of BWR plant

Radiation shielding analysis around the core of BWR plant was performed with a three-dimensional Sn code TORT to prepare detailed neutron flux distribution for the recent design needs of a BWR plant such as a life extension and a preventive maintenance. Two-dimensional R-Z, R-θ and three-dimensional R-θ-Z models, and JSSTDL cross section data based on JENDL-3 library were applied to the analysis. Consequently, detailed spatial distribution of neutron flux in the reactor pressure vessel (RPV) was obtained with the energy range of MeV to thermal neutron. The analysis method was validated by comparing the calculated results with the measured data in a surveillance test program. It was found out that both the effects of rectangular shaped geometry of the core and the neutron leakage from the upper core region are considerably high especially in the location near the core such as the shroud. In addition, the effects of the parameters; the order of Pl, the number of Sn quadrature, mesh width and collapsing of cross section data on calculated results were also examined. (author)