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Confirm inherent safety characteristics of HTGR such that the reactor becomes the stable state spontaneously even if the coolant flow rate reduces down to one third of rated valueFeb. 6, 2007[Point] The Japan Atomic Energy Agency (JAEA) first confirmed excellent and inherent safety characteristics of prismatic typed High Temperature Gas-cooled Reactor (HTGR) in the world through performing the partial loss of coolant flow tests such that the coolant flow rate reduces down to one third of the rated value in the full power (30MW) operation of the High Temperature engineering Test Reactor (HTTR). The excellent and inherent safety characteristics of prismatic typed HTGR such that the reactor becomes the stable state due to spontaneously physical phenomena initiated in the reactor core were confirmed in this test. [Outline] The JAEA performed the partial loss of coolant flow tests as the safety demonstration tests with escalating the reactor power step-by-step to show the excellent and inherent safety characteristics of the HTGR by using the HTTR as the innovative nuclear technology development program entrusted by Ministry of Education, Culture, Sports, Science and Technology. The HTGR has excellent and inherent safety characteristics such as large heat capacity of the reactor core and negative reactivity feedback effect make the reactor the stable state even if an abnormal coolant flow reduction event is initiated. The large heat capacity if the reactor core means the high ability to accumulate the heat and the negative reactivity feedback effect means the characteristics to decrease the fission reaction spontaneously in the case that the temperature of the reactor core increases. It was strongly required to confirm such inherent safety characteristics precisely to make possible the reactor design such that the emergency reactor shutdown is not necessary, the reactor is stopped due to spontaneously physical phenomena initiated in the reactor core and there is no possibility to extend to the significant core damage (that is the severe accident) in the abnormal coolant flow reduction event. The JAEA performed the partial loss of coolant flow tests with escalating the reactor power step-by-step from 30% (9MW) to confirm above-mentioned characteristics and improve the analysis technology. One or two out of three gas circulators to circulate the primary coolant are stopped in this test. Up to now, two gas circulators stop test at the reactor full power operation 30MW was successfully completed as the final test. The JAEA as the Top-runner of the HTGR research and development in the world promotes strongly to perform the test with more severe condition such as the loss of coolant flow etc. and to improve furthermore the analysis accuracy by taking into account of the detailed temperature distribution of the reactor, etc. An outcome obtained from this test to attract a considerable attention in the world will be useful to �the research and development of technological systems for a high temperature gas reactor which can be a high temperature heat source for power generation with excellent economic efficiency and hydrogen production based on it� mentioned in the Framework for Nuclear Energy Policy, and will be useful to the design research for the Very High Temperature Reactor promising as the generation IV reactor system. |
