Users' manual of a thermohydraulic computer code; "HAPI-II" for the pressure tube type reactor

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This report is a users' manual of a thermohydraulic computer code 'HAPI-II' for the pressure tube type HWR, FUGEN. The prediction of channel coolant flow distribution is important for the evaluation of thermal design margin (MCPR). This prediction is more important than LWRs, for the pressure tube type reactors like the FUGEN in which inlet and outlet pipes are longer and have more complex shapes. Therefore, a number of hydraulic tests using full scale test facilities have been carried out at PNC O-arai Engineering Center, much valuable data have been obtained for fuel assemblies, pipes, and bends. On the basis of these data, a 'HAPI' code has been developed. It is comfirmed that the 'HAPI-II' code has an accuracy of 4% on the recirculation flow rate and of 7% on the core flow distribution compared with actually measured data in FUGEN reactor for all operating conditions. This program is written in FORTRAN language and its size is 500 Kbyte, computing time is approximately 1 minute for a half core of FUGEN Reactor.