SIMULATED AP600 RESPONSE TO SMALL-BREAK LOSS-OF-COOLANT-ACCIDENT AND NON-LOSS-OF-COOLANT-ACCIDENT EVENTS - ANALYSIS OF SPES-2 INTEGRAL TEST-RESULTS

As part of the AP600 design certification program, a series of compone nt separate effects tests and two integral systems tests of the nuclea r steam supply system were performed. These tests were designed to pro vide data necessary to validate Westinghouse safety analysis codes for AP600 applications. In addition, the tests have provided the opportun ity to investigate the thermal-hydraulic phenomena that are expected t o be important in AP600 transients. One series of integral systems tes ts was undertaken on the SPES-2 facility in Italy, a full-height, full -pressure, 1/395th-power and -volume scale simulation of the AP600 nuc lear steam supply system and passive safety features. A series of thir teen design-basis events were simulated at SPES-2 to obtain data for v erification and validation of the computer models used for the safety analysis of the AP600. The modeled initiating events included a series of small-break loss-of-coolant accidents (SBLOCAs), single steam gene rator tube ruptures, and a main steam-line break. The results of the a nalyses of the SPES-2 test data, performed to investigate the performa nce of the safety-related systems are reported. These analyses were al so designed to demonstrate, through mass and energy inventory calculat ions, mass and energy balances, and event timing analyses, the applica bility of the SPES-2 tests for computer model verification and validat ion. The key thermal-hydraulic phenomena simulated in the SPES-2 tests and the performance and interactions of the passive safety-related sy stems that can be investigated through the SPES-2 facility are emphasi zed. The latter includes the impact of accumulator nitrogen and nonsaf ety-related system actuation on the passive safety-related system perf ormance. It is concluded that the key thermal-hydraulic phenomena that characterize the SBLOCA and non-LOCA transients have been successfull y simulated in the SPES-2 facility, and the test results can be used t o validate the AP600 safety analysis computer codes. The SPES-2 tests demonstrate that the AP600 passive safety-related systems successfully combine to provide a continuous removal of core decay heat. The SPES- 2 tests also showed no adverse interactions between the passive safety -related system components or with the nonsafety-related systems. In p articular, it was found that the effect of noncondensable nitrogen on passive safety-related system performance was negligible.