Research and developments of guidelines for thermal load modeling

In order to realize reliable and economical plants, Japanese commercialized fast reactors adopt innovative component design such as simplification of a reactor vessel, integration of intermediate heat exchangers with primary pumps, shortening of pipes and reduction of loop numbers. Thermal load, one of the principal loads in fast reactor components, becomes critical in those components. For realistic evaluation and mitigation of thermal loads “Interim Guidelines for Thermal Load Modeling” were developed. These guidelines are referred from “Elevated Temperature Structural Design Guide for Commercialized Fast Reactor (FDS)”.Current guidelines deal with system thermal transient load and thermal striping load. As for system thermal transient load, two kinds of modeling method were provided. Concerning thermal striping load, thermal fatigue evaluation method was developed considering attenuation effects of thermal stress related to frequency of temperature fluctuation.Interpretation documents of the guidelines and exemplars of application problems were also provided to support designers.