Simulation of AER-DYN-002 and AER-DYN-003 Control Rod Ejection Benchmarks by RELAP5-3D/PHISICS Coupled Codes

ENEA “Casaccia” Research Center is collaborating with Idaho National Laboratory performing activities devoted to the validation of the Parallel and Highly Innovative Simulation for INL Code System (PHISICS) neutron simulation code. In such framework, the AER-DYN-002 and AER-DYN-003 control rod (CR) ejection benchmarks were used to validate the coupled codes RELAP5-3D/PHISICS. The AER-DYN-002 benchmark provides a test case of a CR ejection accident in a VVER-440 at hot-zero-power and end-of-cycle conditions assuming an adiabatic fuel and taking into account only the fuel temperature feedback. The AER-DYN-003 benchmark is based on the same problem; however, the moderator density feedback and the coolant heat removal are also considered. A RELAP5-3D core channel-bychannel, thermal-hydraulic nodalization was developed and coupled, first with the RELAP5-3D internal neutronic routine NESTLE and then with the PHISICS code. Analysis of the AER-DYN-002 results shows that the steady-state solutions are in good agreement with the other participants’ average solution, while some differences are shown in the transient simulations. In the AER-DYN-003 benchmark, however, both steady-state and transient results are in good agreement with the average solution.