Power reactor noise simulation and analysis by developing Time-Domain neutron noise Simulator: iPWR case study

In nuclear industry, the main challenges of nuclear power plants are to improve safety and reduce maintenance periods which lead to optimized operation costs. These challenges are also present for new-generation power plants especially small modular reactors (SMR). Implementation of online condition monitoring methods such as power reactor noise analysis that investigates symptoms caused by various perturbations in the in-core sensors can be useful to minimize these challenges. In this study, a time-domain power reactor noise analysis simulator will be presented to investigate perturbations in power reactors. The simulator is structured based on the nodal expansion method to discretization of neutron noise equations in two energy groups and three-dimensional rectangular space, whereas the implicit-difference discretization approach is employed to treat the time evolution. The developed steady-state module is verified by evaluating the large-scale and small-scale benchmark problems, and comparing with the PARCS code results. To verify the outcome, a noise analysis is also carried out for both the KWU and SMART cores, and the results are compared against the estimates by the CORE SIM and SDHACNEM frequency-domain power reactor noise simulators. Simulation and analysis have been conducted for perturbations including control rod random vibrating and vibration with combining frequencies. The approach proved superior to the conventional frequency-domain simulators over the advantage of random perturbation simulation without removing part of the in-core sensor response. Furthermore, the results show that the framework is specifically suited for dealing with perturbation sources including random vibrating of the absorbers and absorbers with variable strength.