[en] The computer program ALARM-B2 is a modified version of ALARM-B1 and is a tool to analyse thermo-hydraulic phenomena of BWR during a postulated large break LOCA. The major improvement is to provide one dimensional heat conduction equation, heat transfer correlation package, and point reactor kinetics equation to analyse the heat transfer phenomenon in the core region during a LOCA. Analytical models of the fluid conservation and state equations are the same as in ALARM-B1 code; namely ALARM-B2 solves one-dimensional integral forms of the fluid conservation and state equations under the assumptions common to conventional node-junction type models. The main purpose of this report is to explain the frame-work of ALARM-B2 together with the requirements of input data. The validity of models newly incorporated into the present code is now being examined. (author)