Conceptual design of high temperature reactors cooled by supercritical light water

Overview of the conceptual design of the high temperature reactors cooled by supercritical water (SCR) is presented. It is being studied for 13 years at the University of Tokyo. The design was taken as the reference of HPLWR (high performance LWR) study of EU. It was selected as a Generation4 reactor. The research and development started worldwide. We studied major elements of reactor conceptual design and safety evaluation by developing computer codes. It includes fuel rod design, core design of thermal and fast reactors, plant heat balance, safety design, accident and transient analysis, LOCA, PSA, plant control, start-up and stability. The big advantage of the SCR concept is that the temperatures of major components such as reactor pressure vessel, control rod drive mechanisms, containments, coolant pumps, main steam piping and turbines are within the temperatures of the components of LW R and supercritical FPP, in spite of the high outlet coolant temperature. The experience of these components of LWR and supercritical fossil fired power plants will be fully utilized for SCR. The potential cost reduction in both reactor and turbines are the characteristics of the SCR. It should be noted that the SCR is the smallest reactor not in power, but in size. Supercritical water contains higher enthalpy than sub-critical water per volume. Once-through coolant cycle is simpler than the re-circulating one. The containment is smaller than that of BWR due to the small coolant enthalpy inside. These are the reasons why the SCR is the smallest in sizes. The high temperature, supercritical-pressure light water reactor is the logical evolution of LWR. It is based on the experiences of LWR design and safety and supercritical fossil-fired power plant technology. It is the reactor version of the once-through boiler. Its development follows the history of boilers.