S. Zhang

Nuclear Power Institute of China,

China

Abstract. Passive safety concept is extensively used in the design for next generation advanced PWR nuclear power plant. The decay heat of reactor core can be removed through natural circulation flow of coolant following an accident. This not only increases reliability of engineered safety systems and reduces core melt frequency, but also simplifies systems and increases plant economy. Nuclear Power Institute of China (NPIC) has performed preliminary experiment research and relative theoretical analysis for passive characteristics of advanced PWR nuclear power plant AC600/1000. Three tests about natural circulation flow have finished as the following: residual heat removal through SG secondary side, core makeup tank behavior and wind flow of containment. The above mentioned three mechanism tests have verified natural circulation flow concept of AC600/1000. By the end of this year NPIC will finish other two single tests in order to research the following key technology of the passive safety systems: The natural circulation characteristics of tandem system of SG secondary side loop and air flow loop for emergency residual heat removal system (ERHRS) after station blackout accident; The water flow behavior in primary coolant system contained by core makeup tank, pressurizer, accumulator and reactor pressure vessel after small break accident; Computer code development and verification. Meanwhile, NPIC will cooperate with Karlsruhe Technology Center of Germany to research natural circulation characteristics of air in the annular channel between the steel shell and the concrete shell of containment. NPIC plans to build two large integral test facilities. One of which is used to research natural circulation flow and residual heat removal through primary loop, secondary loop and air flow loop from reactor core to ultimate sink —atmosphere after station blackout accident. It is also used to research the passive safety injection features for emergency core cooling system. The second integral test facility will be used to research the comprehensive heat removal behavior of passive containment cooling system. The paper will describe the utilization of natural circulation concept in the passive safety systems, experiment research performed by NPIC and computer codes as well for AC600/1000.