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Numerical investigation of Fukushima Daiichi-2 SBO scenario
State Nuclear Power Research Institute, United States .
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
2014 (English)In: International Congress on Advances in Nuclear Power Plants, ICAPP 2014, 2014, Vol. 2, 995-1003 p.Conference paper (Refereed)
Abstract [en]

Simulations of the severe accident progression for Fukushima Daiichi NPP Unit 2 (1F2) are performed using the MELCOR code. Detailed modeling of the plant is developed to represent the whole reactor system and its safety systems. The predicted results are compared with the plant data measured during the accident. By applying the main actions taken during the accident and the assumptions into the full plant MELCOR modeling, the major physical phenomena from core uncovery and degradation till reflooding of reactor core by fire pump injection are reproduced in the simulations. The trend of simulation results agree in general with the limited data (e.g., pressures) measured by the plant. The closed RCIC cycle, which involved steam flow and working process, and its interacting with reactor cooling status was modeled by user defined control function in the simulation. The simulations reveal that: The operations of RCIC kept the reactor core flooded to the top for more than 70 hours after the earthquake until the suppression pool water got saturated. Sea water might have flooded into the TORUS room to more extent than as assumed, which kept cooling of suppression pool, and delayed the failure of RCIC. Around 2 hours before the cooling water by fire pump was able to inject water into the reactor, the core damage started at around 76.5hr and got oxidized severely within 2 hours. While no further degradation occurred, the core geometry was maintained, and capable of being cooled by sea water injection.. A leakage has possibly occurred somewhere in RCS steam phase region, to account for pressurization of containment dry well before suppression pool got saturated.

Place, publisher, year, edition, pages
2014. Vol. 2, 995-1003 p.
Keyword [en]
Core degradation, Fukushima accidents, RCS leakage, TORUS r flooding, Accidents, Cooling, Core disruptive accidents, Floods, Lakes, Nuclear energy, Nuclear power plants, Reactor cores, Seawater, Control functions, Detailed modeling, Fukushima daiichi, Numerical investigations, Physical phenomena, Sea water injections, Water injection
National Category
Physical Sciences
URN: urn:nbn:se:kth:diva-167585ScopusID: 2-s2.0-84907082196ISBN: 9781632668264OAI: diva2:815479
International Congress on Advances in Nuclear Power Plants, ICAPP 2014, 6 April 2014 through 9 April 2014, Charlotte, NC

QC 20150601

Available from: 2015-06-01 Created: 2015-05-22 Last updated: 2015-06-01Bibliographically approved

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Chen, YaodongWeimin, Ma
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