Scwr Stability Analysis Using Neutronics/thermal-hydraulics Coupled Axial 1D Model

Supercritical Water-cooled Reactor (SCWR) is the only water-cooled reactor technology selected as one of the Generation-IV reactor candidates. Currently, SCWR related basic studies are receiving considerable publicity in the world, where the stability analysis of SCWR is one of the challenging research topics. It is also the main issue under investigation in the 6th research task of the National Basic Research Program of China ("973 plan").In order to study the potential stability issue of a SCWR core caused by neutronics/ thermal-hydraulics coupling, a simplified axial one-dimensional (1D) single channel model is developed, which consists of fuel, cladding, coolant and moderator. Based on this model, the direct numerical simulation method is employed to investigate the SCWR core stability issue. The axial 1D steady-state analysis model is formulated at first and corresponding numerical code is developed. It contains 1D two-group neutronics model, fuel thermal conductivity model, coolant/moderator heat transfer model and cross section feedback model. In order to verify the code, related results of the United States'SCWR core design given in the literature is taken as the reference. Obtained results are found to be comparable to the reference ones, which lays down a solid basis for the further transient studies of SCWR core. Moreover, the developed steady-state analysis code is also used to analyze the thermal/fast hybrid spectrum SCWR reactor design given by Shanghai Jiao Tong University, suggestions for further improving the design scheme are given based on the obtained axial 1D results.Based on the steady-state analysis code, a transient analysis code is developed. Control rod drop/ejecting, xenon oscillations and load following models are also developed and integrated with the code. Corresponding transient analyses are performed to preliminarily study the transient characteristics of the SCWR reactor core.In the end, by use of the developed transient code, preliminary stability analyses for the U.S. SCWR core design are performed. By introducing a coolant flow rate perturbation at the core inlet and then checking whether the perturbation converges or diverges at the core outlet, we have obtained the stability boundary. The research work has laid down a solid basis for the future in-depth stability analysis of SCWR core.