Keywords: pressurised water reactors, PWR, ion exchanger, saturation activity, removal rate, filters, simulation, corrosion, purification systems, flow rate perturbations, nuclear energy, nuclear power
Numerical simulations of corrosion product activity in the purification system of a typical PWR under nonlinearly rising corrosion and flow rate perturbations
Numerical simulations of corrosion product activity in the purification system of a Pressurised Water Reactor (PWR) are presented. The computer programme code Corrision Product Activity in Reactors (CPAIR-RC), developed by the authors, has been used to find corrosion product activity in the ion exchanger and filters of PWR under nonlinearly rising corrosion rates and flow rate perturbations. For nonlinearly rising corrosion rates, a typical value of removal rate 750 cm³ s−1 is taken, for which the saturation value of the activity has been found sufficiently low (0.27 µCi cm−3). The simulation results shows that for the constant refuelling and purification process, the activity, due to 59Fe, 99Mo and 56Mn, reaches saturation values within about 1000 h of reactor operation. However, two major contributors to radioactive buildup, 58Co and 60Co, keep on accumulating and do not saturate within this period. When the flow rate is decreased by 10% of the rated flow rate after 500 h of reactor operation, a dip in the activity is seen (which reaches the value of 0.0182 µCi cm−3), then it begins to rise again and reaches a saturation value of 0.271 µCi cm−3. The computed values of corrosion product activity from CPAIR-RC have been compared with some of the experimental data that are available in the literature and a fair agreement between them has been found.