Fig. 4-2 Conceptual diagram of LSTF The Large-Scale Test Facility (LSTF) is an integral test facility for real-time simulation of thermohydraulic behavior of 1,100 MWe PWRs. LSTF simulates the major components of a 4-loop 1,100 MWe PWR under the same operating pressure and temperature conditions. Elevations and heights of components are full scale while the volumetric scale is 1/48 of 1,100 MWe PWRs.

Fig. 4-3 Comparison between experiments and analyses Illustrated are measured temperatures and predicted temperatures by analysis. The USA evaluation model RELAP5/MOD3 and the JAERI model were used for analysis. Good agreement is obtained with the JAERI model.

The advanced light water reactor, AP600, is a next-generation PWR designed by Westinghouse. A special feature of the AP600 is its heat removal capability under severe accident conditions. The AP600 utilizes safety systems actuated by natural gravitational forces as an alternative to depending on systems that function under artificial conditions. It is believed that there can be no malfunctions of such a safety system. However, it may be possible that the actuating force will be affected by thermohydraulic conditions of the fluid in the circulating loop of the reactor and the systems themselves because of the very weak driving force for injecting water. The Large-scale Test Facility is an integral test facility for real-time, authentic simulation of transient thermohydraulic phenomena evolving in currently operating PWRs under severe accident conditions. To demonstrate the heat removal capability, experiments were conducted with LSTF. In these experiments, the functions of two safety systems of AP600, a Core Makeup Tank (CMT) connected to a cold leg and a two-stage Automatic Depressurization System (ADS) connected to a hot leg and pressurizer, were simulated by existing components of LSTF. Several hundred seconds after the start of the experiment, natural circulation was established in the loop formed by the simulated CMT and the primary system. After natural circulation was established, cold water was discharged steadily from the injection tank.

Reference Y. Anoda, et al., Integral Testing on Thermal-Hydroulic Responces of Advanced Passive-Safety PWR AP600, The 72 period JSME Spring Annual Meeting, Tokyo, 1995.

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