[en] In the Hamaoka Nuclear Power Station, a computer is used principally for reactor core calculations to prepare the nuclear constants etc. data, fuel exchange calculations based thereon and short/long term core characteristics calculations. Features of the computer usage are feasibly for commercial reactor plants with extensive data, high accuracy in burnable poison calculations and automatic data transmission between codes due to input/output simplification. Respective calculations with the computer are described. And also the uses of a computer are briefed in such as radiation control, aseismatic design and diffusion of thermal waste water. (Mori, K.)