Multi-cycle analysis of OPR1000 using multi-physics coupled codes of RAST-K, CTF and FRAPCON

Abstract

The nodal diffusion reactor core analysis code, RAST-K, which is under development at Ulsan National Institute of Science and Technology (UNIST), has been coupled and integrated with the subchannel thermal hydraulics (TH) code, CTF, and the steady-state fuel performance code, FRAPCON to establish multi-scale, multi-physics reactor core analysis code system. The three codes with different physical phenomena are coupled in a sequential scheme. CTF and FRAPCON obtains the pin power distribution calculated by RAST-K. Then, CTF calculates coolant properties, and returns the coolant temperature/density to RAST-K for cross section feedback, while the coolant bulk temperature/pressure is transferred to FRAPCON for fuel rod boundary condition. FRAPCON performs fuel thermo-mechanical analysis using the power distribution and fuel rod boundary condition and returns the fuel temperature to RAST-K. To improve the multi-physics coupled calculation efficiency, a restart capability has been added to FRAPCON. Furthermore, to maintain a consistent burnup model, a predictor-corrector coupled depletion scheme is introduced in FRAPCON calculation. The multi-physics coupled system is applied to Cycles 1–4 operation of OPR1000 commercial reactor. Comparison of design parameters for cycle 4 calculated by the multi-physics system and RAST-K standalone with simple internal TH solver shows decreased cycle length of 2 days and reduced peaking factor by 0.6% at the beginning of cycle (BOC).