Failure Analyse And Technique Amelioration In A State Of Low Load/Low Energy Of The Centrifugal Chiller In QS Ⅱ NPP

The Nuclear Island (NI) chilled water system (for short DEG) supplies cooling water source for NI building in QinShan phase II Nuclear Power Plant (QS II NPP) 1/2 unit. The functional lose of DEG system goes with the one of EVC, EVR, RRM systems etc., which will result in temperature of NI reactor building rise. When the temperature exceeds 60℃,the function of electric control components will be affected because caloric can't be emitted, and the state of the reactor shall move back inevitably. Centrifugal chiller, the main equipment of DEG system, has operated unstably in a state of low load /low energy since 2000, which brought some effects to NI ventilation systems, and was a hidden trouble for Nuclear Power Unit.This paper analyses the failure cause of the centrifugal chiller in the state of low load/low energy, combined with demands of the system operation of QS II NPP, and puts forward technique amelioration for partial structure of the chiller by theoretic calculation and configuration analyse. At one time , the scheme of adding heat-bypass device aiming at the state of low load and Freon pump aiming at the state of low energy is put forward .Performance test in virtue of the same type's sample machine shows that the amelioration scheme is feasible for DEG centrifugal chiller of QS II NPP.