Time-dependent leakage model for the identification of defective fuel assemblies of VVER-type nuclear reactors. Part 2: Expediting the solution and applications to a nuclear power plant

Abstract

The leakage-free operation is a fundamental requirement for nuclear reactors for the whole duration of each reactor cycle. Although the physical and chemical processes arising from fuel failures generally do not exclude the safe operation of the reactor, they could have significant direct operational and economic impacts. Monitoring the reactor core's leakage-free state is performed by measuring the gamma spectra and, thus, the isotope selective radioactivity of the primary coolant. The burnup and the leakage parameters of the defective fuel elements can be estimated by calculations with relevant leakage models. The time-dependent leakage model developed in the Institute of Nuclear Techniques can mathematically describe the leakage processes for the duration of a complete reactor cycle, taking into account most of the operational parameters of the reactor. A new time-dependent leakage function model, which can numerically approximate the leakage function with higher precision than the previously used analytical estimations was developed and implemented in the time-dependent leakage model. The model is supplemented with a spiking identifier algorithm module that can replace the radioactivity spiking phenomena' identification and characterization algorithm, which was previously performed manually.