UPTF EXPERIMENT - FLOW PHENOMENA DURING FULL-SCALE LOOP SEAL CLEARINGOF A PWR

To investigate the flow phenomena in the primary system of a pressuriz ed water reactor (PWR) during a loss-of-coolant accident (LOCA) occurr ing with a small or intermediate break, experiments were performed at the full-scale Upper Plenum Test Facility (UPTF). Within the Transient and Accident Management (TRAM) program integral and separate effect t ests were carried out to study loop seal clearing and to provide data for the further improvement of computer codes concerning the reactor s afety analysis. This paper describes the UPTF tests that focus on the sequence of loop seal clearance in a four-loop operation for two diffe rent cold leg break sizes and the residual water levels, the flow patt erns in, and the pressure drops across a single loop seal during the c learing. The UPTF results obtained from a single-loop seal operation a re compared with experimental data and correlations available in the l iterature. Two correlations are proposed which allow the quantificatio n of residual water levels in the loop seal under PWR conditions. It i s shown that the steam-water test results gained from the full-scale U PTF with realistic PWR loop seal geometry differ from those obtained f rom the full or small-scale test facilities under air-water conditions . The UPTF experiments indicate the substantial need for steam-water t est data from a full-scale facility with realistic PWR geometries in o rder to validate PWR LOCA thermal-hydraulic system codes to predict lo op seal clearing correctly. (C) 1998 Elsevier Science S.A.