Simulation of leaking fuel rods in a VVER reactor

• The RING code was developed for the estimation of the number of leaking fuel rods.
• Iodine, xenon and krypton coolant activity concentrations are evaluated.
• Iodine spiking during operational transients can be predicted.

A new numerical algorithm has been developed for the simulation of leaking fuel rods under steady state and transient conditions and the specific parameters of the model for a VVER-440 type NPP have been determined. The steady state model can be applied for the calculation of leaking fuel characteristics using measured iodine and noble gas activity concentration data. The transient model is capable of predicting the 131I activity peak during operational transients. The models are included in the RING code that is part of the on-line monitoring system of the Paks NPP in Hungary.