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Confirm excellent and inherent safety characteristics of HTGR during an abnormal control rod withdrawalDec. 15, 2006[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 control rod withdrawal test in the wide range of the reactor power from 30% (9MW) to 80% (24MW) by using the High Temperature engineering Test Reactor (HTTR). [Outline] The JAEA promotes the research and development of the HTGR as a Top-Runner in the world and performed the safety demonstration tests 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. On December 13 in 2006, the control rod withdrawal test which is one of the safety demonstration tests has been completed successfully. 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 in the case of abnormal control rod withdrawal events. The large heat capacity of 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 reactor shutdown is not necessary in the abnormal control rod withdrawal event. The JAEA performed the control rod withdrawal tests with escalating the reactor power step-by-step from 30% (9MW) to confirm above-mentioned characteristics and improve the analysis technology. Up to now, the control rod withdrawal test at the reactor power of 80% (24MW) was completed as the final test, and the excellent and inherent safety characteristics of the HTGR were systematically confirmed in the wide range of the reactor power. Pre-analysis results show good agreement with the experiment results. The JAEA promotes strongly the further improvement of the analysis accuracy by taking into account of the detailed temperature distribution of the reactor, etc. An outcome of this test to attract a considerable attention in the world will be useful to validate and improve the calculation code to analysis the reactor characteristics and the behaviors during the abnormal events for the Very High Temperature Reactor (VHTR) promising as the generation IV reactor system, and will contribute the rationalization of the engineered safety features and the cutback of the construction cost, etc. for the VHTR. |
