Improvement of the decay heat removal system for VHTR

Improvement of the decay heat removal system for a HTGR. While the typical capacity of the current water-cooled commercial reactors is in the range of 1,000∼1,300 MWe, that of a HTGR is currently only 100-300 MWe such as 117MWe of PBMR and 285MWe of GT-MHR. Increasing the plant capacity of a HTGR is highly desirable to improve the plant economy of a HTGR. For the increase of the capacity in a passive plant, a development of a system concept with improved performance is required. A new creative design concept of the LFDRS has been developed following the objective of the research project, i.e., development of an improved decay heat removal system design concept to improve the plant economy of a HTGR. The developed concept LFDRS enables the capacity of a HTGR to be increased at least by 40% from the current maximum capacity without accounting the reactor vessel size increase from the increased plant capacity by using the LFDRS.Also a comprehensive computer code system to analyze the performance of various types of a decay heat removal system was developed. The developed code system consists of a reference code system which focuses on the calculation accuracy and a fast running system which focuses on the calculation speed and simplicity in handling. Since the developed LFDRS concept is quite creative and totally different from the conventional designs, it has a meaning that it has prepared the starting point of developing our own HTGR design type and elevated in the international society the position of our HTGR system design technology, on which development efforts just started