SIMULATION OF CORROSION PRODUCT ACTIVITY IN PRESSURIZED-WATER REACTORS UNDER FLOW-RATE TRANSIENTS

Simulation of coolant activation due to corrosion products and impurit ies in a typical pressurized water reactor has been done under flow ra te transients. Employing time dependent production and losses of corro sion products in the primary coolant path an approach has been develop ed to calculate the coolant specific activity. Results for Na-24, Mn-5 6, Fe-59, Co-60 and 99Mo show that the specific activity in primary lo op approaches equilibrium value under normal operating conditions fair ly rapidly. Predominant corrosion product activity is due to Mn-56. Pa rametric studies at full power for various ramp decreases in flow rate show initial decline in the activity and then a gradual rise to relat ively higher saturation values. The minimum value and the time taken t o reach the minima are strong functions of the slope of linear decreas e in flow rate. In the second part flow rate coastdown was allowed to occur at different flow half-times. The reactor scram was initiated at 90% of the normal flow rate. The results show that the specific activ ity decreases and the rate of decrease depends on pump half time and t he reactor scram conditions. (C) 1997 Elsevier Science Ltd.