Three-dimensional transient analysis for control rods drop into CSR1000 core

Abstract

Transient performance of China supercritical water-cooled reactor (SCWR) with the rated electric power of 1000MWe (CSR1000) core during the control rods (CR) drop into the core is analyzed and evaluated with the coupled three- dimensional neutronics and thermal-hydraulics SCWR transient analysis method. The 3-D CR drop transient analysis shows that while the high worth CR drop into the core, the core power in the initial stage of the CR drop process decreases rapidly. The core power descent rate exceeds the shutdown setting value, which will trigger the protection shutdown. While the low worth CR drop into the core, due to the reactivity feedback of the water density, the core power decreases slowly, and the core power descent rate cannot reach the shutdown setting value, which will not trigger the protection shutdown. In the transient process, the peak value of maximum cladding surface temperature (MCST) remains lower than the transient safety limit of 850 °C, whether it is a high worth CR drop or a low worth CR drop. The safety performance of CSR1000 core can be ensured in the process of CR drop into the core under the salient reactivity feedback of water density and the essential reactor protection system.