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ECCS accumulator performance in scaled PWR experiments

Conference ·
OSTI ID:6609475
Best-estimate models for pressurized water reactor (PWR) loss-of-coolant (LOCA) analysis require a realistic assessment of the thermodynamic behavior of the N/sub 2/ gas in the accumulators of an emergency core cooling system (ECCS). The LOFT and Semiscale reactor safety research facilities, which are scaled to a commercial PWR, have provided experimental information which identifies the thermodynamic behavior of scaled ECCS accumulators. The thermodynamic behavior of PWR accumulators can be identified from the experimental results through the scaling rationale. ECCS accumulators are large tanks partially filled and pressurized with N/sub 2/. The accumulators are isolated from the primary system piping by two check valves. Reduction in system pressure due to a pipe break causes the check valves to open and accumulator flow to begin. The thermodynamic behavior of the N/sub 2/ gas in the accumulator can be characterized quite simply by a polytropic gas constant. RELAP4 calculations on the LOFT system show typical differences of about 15% in accumulator flow rates between polytropic gas constants of 1.0 (isothermal) and 1.4 (isentropic) where the isentropic case corresponds to the lower flow rate.
Research Organization:
EG and G Idaho, Inc., Idaho Falls (USA)
DOE Contract Number:
EY-76-C-07-1570
OSTI ID:
6609475
Report Number(s):
CONF-781105-7
Country of Publication:
United States
Language:
English