INVESTIGATIONS OF THERMAL STRIPING IN PRIMARY CIRCUITOF PROTOTYPE FAST BREEDER REACTOR

摘要

Thermal striping is a phenomenon, whichleads to random temperature fluctuations in theinterface between non-isothermal streams arisingout of jet instability. Due to the high heat transfercoefficient associated with liquid metal coolantsuch as sodium, the temperature fluctuations aretransmitted to the adjoining structures withminimal attenuation, which eventually leads tohigh cycle fatigue and crack initiation in thestructures. Detailed thermal hydraulic andstructural mechanics investigations have beencarried out to quantify the amplitude andfrequency of temperature fluctuations in thestructures of primary sodium system of the Indian500 Mwe pool type fast reactor (PFBR), which isunder construction at Kalpakkam. Thermalhydraulic investigation consists of ComputationalFluid Dynamics (CFD) simulations in two levels.In the first level, locations prone to thermalstriping are identified by performing globalconjugate 3-D simulation of hot and cold poolsemploying the standard k-e turbulence model. Inthe 2ndlevel, the transient transport equations aresolved by Direct Numerical Simulation method, topredict detailed flow and temperaturefluctuations, based on far field boundaryconditions obtained from the global study. Thepeak-to-peak values of structural temperaturefluctuations predicted are within the acceptablelimits arrived based on structural mechanicsinvestigation.