ROSA AP600 TESTING - FACILITY MODIFICATIONS AND INITIAL TEST-RESULTS/

The Japan Atomic Energy Research Institute (JAERI) and the United Stat es Nuclear Regulatory Commission (USNRC) are jointly conducting confir matory, integral testing on the Westinghouse AP600 reactor transient r esponses by using the ROSA-V Large Scale Test Facility of JAERI. This facility, built originally to simulate conventional 4-loop pressurized water reactors (PWRs), has been modified by adding components specifi c to the AP600 design. The modified LSTF now provides a full-pressure, full-height, 1/30.5 volumetrically-scaled simulation of AP600. Five l oss-of-coolant accident (LOCA) experiments were performed by August 19 94, simulating transients initiated by cold leg breaks, a Pressure Bal ance Line (PBL) break, and inadvertently open Automatic Depressurizati on System (ADS) valves. These experiments indicated adequate core cool ing and decay heat removal performance of the AP600 passive safety com ponents.