Host: The Japan Society of Mechanical Engineers
Name : The 30th International Conference on Nuclear Engineering (ICONE30)
Date : May 21, 2023 - May 26, 2023
The Super LWR is the Japanese representative design concept of the thermal reactor type of the Supercritical Watercooled Reactor (SCWR). The reactor operates at 25 MPa and the coolant undergoes large enthalpy rise as its density decreases to about 1/10 from the core inlet to the outlet. The large water density change indicates possibility of spectral shift operation, in which the neutron spectrum is gradually softened during the operation by increasing the core average water density to gain reactivity and improve utilization of the uranium (U) resources. However, the core is cooled by single-phase flow and the core outlet coolant is directly fed to the turbine in the once-through direct cycle plant system. One of the issues of spectral shifting of such a system is controlling the core average water density without significantly changing the core average coolant outlet temperature. This study proposes two approaches. The first approach is controlling the core inlet coolant temperature and flow rate simultaneously and the second approach is inserting / withdrawing water displacer rods into / out of the core. Hence, this study aims to reveal potential improvements and issues of the Super LWR core with spectral shift operation with the above proposed approaches.
