Structural Stored Heat Effect on Pressure and Coolant Mass Changes during BWR Small Break Simulation Tests

概要

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Scaling considerations have been made for liquid line small break simulation tests of a BWR affected by the stored heat released from loop structures. Necessary scaling parameters were given from lumped energy and mass balances equations. It was possible to compensate for excess stored heat released in the reduced-scale facility by increasing the coolant discharge flow area A<SUB>D</SUB>. Although this compensation accelerated the blowdown process, actual pressure and coolant mass changes of the reactor system could be obtained by altering the time scale of the test results by the ratio of A<SUB>D</SUB>/V (V: vessel volume) between the test loop and the reactor system. A semi-experimental evaluation of the stored heat release rate in the Two Bundle Loop (TBL) during blowdown after the operation of Auto-matic Depressurization System (ADS) was also presented on the basis of comparison of experimental diathermic and analytical adiabatic blowdown pressure changes. The obtained results were used in the determination of simulated ADS nozzle diameter for small break tests at the TBL.