Overview of Integrated Modular Water Reactor (IMR) Development

The Integrated Modular Water Reactor (IMR) is an integrated primary system reactor being developed by a Japanese consortium. The IMR is primarily designed to supply electric power through a power grid with unit output of 350 MWe. In this paper, the outline of the IMR concept and the current development status is presented. The IMR has been developed to meet four design targets related with its economy and safety. The economical targets are reduction of capital and operation costs to be comparable to those of large-scale reactors. The safety targets are fuel failure free design for design basis events and support free operation during accidents. To realize these design targets, the IMR employs several innovative technologies such as an integrated primary system named Hybrid Heat Transport System (HHTS) and a passive decay heat removal system named Stand-alone Direct Heat Removal System (SDHS). The conceptual design of the reactor system and the safety system has been built in a program funded by the Japanese government from FY 2001 to 2004. The feasibility of the HHTS and SDHS has also been examined and confirmed in this program through various analyses and three series of experiments, which are air-water scale test, high temperaturemore » natural circulation test, and SDHS test. The development consortium of the IMR is going into the second phase study funded by the Japanese government from December 2005 to 2007. In this study, in order to optimize the IMR reactor design, we develop the most suitable evaluation methods for the HHTS, where liquid velocities in the HHTS are much lower than forced circulation systems, through several experiments with innovative technologies for two-phase flow phenomena. (authors)« less