Code Development and Steady-state Thermal-hydraulic Analyses for Small Modular Natural Circulation Lead or Lbe Cooled Fast Reactor

Abstract

Small Modular Reactors (SMRs) are attracting widely attention due to its outstanding performance, extensive studies have been carried out for lead or lead bismuth eutectic (LBE) cooled fast reactors (LFRs), and small modular natural circulation LFR is one of the promising candidates for SMRs and LFRs development. One of the challenges for the design small modular natural circulation LFR is to master the natural circulation thermal-hydraulic phenomena in the reactor primary circuit, while the natural circulation characteristics is a coupled thermal-hydraulic problem of the core thermal power, the primary loop layout and the operating state of secondary cooling system etc. Thus, accurate prediction of the natural circulation LFRs thermal-hydraulic features is highly required. In this study, a thermal-hydraulic analysis code is developed for small modular natural circulation LFRs, which is based on several mathematical models for natural circulation originally. A small modular natural circulation LBE cooled fast reactor named as URANUS developed by Korea is chosen to assess the code’s capability. Comparisons are performed to demonstrate the accuracy of the code by the calculation results of MARS, and the key thermal-hydraulic parameters agree fairly well with the MARS’s ones. As a typical application case, the steady-state analyses were conducted to have an assessment of thermal-hydraulic behavior under nominal condition. What’s more, several parameters affecting natural circulation were evaluated. The analyses show that the core thermal power, thermal center difference and flow resistance is the main factors affecting the reactor natural circulation. Improving the core thermal power, increasing the thermal center difference and decreasing the flow resistance can significantly increase the reactor coolant mass flow rate.