Transient multi-scale coupling analysis and its time sensitivity of Xi'an pulsed reactor

Multi-scale thermal-hydraulic coupled calculation is widely applied in the design and safety analysis of reactor. It can provide the thermal-hydraulic results with high-fidelity and high-resolution. According to natural circulation flow requirement of Xi'an pulsed reactor (XAPR), which is a pool-type reactor with natural circulation, a novel multi-scale coupling method of domain overlapping for XAPR is proposed. The system code RELAP5 and subchannel code CTF are coupled. The explicit coupling strategy is applied to the pulsed operation transient condition of XAPR. The results show that the transient coupling strategy is effective, and the results of coupled calculation are closer to the experimental data than those of standalone system code. Meanwhile, the coupled calculation has advantages in obtaining local detailed thermal-hydraulic characteristics. Furthermore, the method is applied to the research of station blackout (SBO) accident of XAPR, and sensitivity analysis of the coupling time-step is carried out. The results indicate that the stability and efficiency are best when the maximum time-step is set as 0.1 s. Meanwhile, in the transient analysis of accident, the multi-scale coupled calculation could provide high-fidelity, high-precision and high-resolution thermal-hydraulic results, which proves the validity and advantage of coupled calculation.