한빛5,6호기 격납건물 수소제어계통 개선 연구

Abstract

On March 11, 2011, the Great East Japan Earthquake triggered an extremely severe nuclear accident at the Fukushima Daiichi Nuclear Power Plant. This devastating accident was ultimately declared aLevel 7 (“Severe Accident”) by the International Nuclear Event Scale (INES). Fukushima Daiichi NPS Units 1, 2, 3, and 4 lost both the offsite power and EDGs, resulting in a long-term station blackout (SBO) due to the earthquake and subsequent tsunami. It has been assessed that the reactor cores of Fukushima Daiichi NPS Units 1, 2 and 3 overheated and melted due to loss of reactor cooling, and as a consequence, the reactor pressure vessels were damaged. The pressure of the containments subsequently increased, and hydrogen explosions occurred in the reactor buildings because of the hydrogen generated by the reaction of fuel cladding with water in a sequence of Units 1, 3, 2, and 4. The outer walls of the reactor buildings were damaged in those processes, and as a result, a large amount of radioactive materials was released to the environment, causing environmental radioactivity impact even on the countries near Japan, such as Korea. Due to the severe accidents at Fukushima DAI-ICHI nuclear power plants (NPPs) in Japan, caused by the great earthquake on Mar.11, 2011, public concern about the safety of domestic NPPs has greatly increased. The government convened the 43th Nuclear Safety Committee (NSC) on Mar. 21, 2011, and decided to conduct a comprehensive special safety inspection (SSI), based on the recommendation of the NSC, on the nuclear facilities in Korea. The SSI was performed from Mar. 23 through Apr. 30, 2011 to conform the mitigating capabilities against severe accidents resulting from huge earthquakes and tsunamis that go beyond expectation, such as those occurred in Fukushima, and to derive any items for improvement needed One of the items for improvement goals upon the severe accidents which can be caused by combined events exceeding the design basis is the Installation of passive hydrogen removal equipmen. The SSI has been performed to check the capability of coping with severe accidents at the NPP’s in Korea by assuming the occurrence of a loss of the cooling functions for the reactor due to a combined accident such as the SBO and the loss of ultimate heat sinks. KHNP installed the Passive Autocatalytic Recombiner during the 9'th O/H in Hanbit Unit 5,6. This study analysed PAR perpormence during severe accidents in the containment.