Multigroup Transient Calculation Capability in RENUS Nodal Kinetics Code

Various research and code development have been carried out to solve the time-dependent neutron diffusion problems by means of the nodal method from 30 years ago. But there is still the need for faster and yet more accurate multi-group nodal kinetics codes to achieve more readily high-fidelity coupled simulation of neutronic and thermal/hydraulic behaviors in advanced cores. In this regard, a multigroup nodal kinetics code named RENUS is being developed at Seoul National University. Last year, the flux solver of RENUS employing the source expansion nodal method (SENM) within a two-level coarse mesh finite difference (CMFD) formulation was developed and verified for steady-state applications. It was shown that SENM provided accurate and efficient solutions for multigroup problems. This work here is to add a transient calculation capability to the RENUS code retaining the basic flux solution framework. The newly developed capability is tested for a MOX core transient benchmark problem involving multigroup group cross sections and thermal-hydraulic feedback