Containment spray cooling is a part of nuclear reactor safety system, which can condense the steam into liquid within the containment structure to realize depressurization and temperature decrease during a reactor accident. In order to investigate the space spray mechanism, which is the heat and mass transfer between falling droplets and surrounding gas, 2-D temperature distribution and velocity field inside a suspended water droplet in upward hot air stream was measured using combined temperature-sens...
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Simultaneous Velocity and Temperature Measurements inside Suspended Droplet in Hot Air Flow using TSPs & PIV

Filter vent model for THALES-2 code was developed and the effect of the filter vent system was evaluated with the code. In Japan, the installation of filter venting system to the BWRs was considered after the accident of Fukushima-daiichi, where the total blackout caused by tsunami resulted in the large amount of fission product (FP) release to the environment. In this study, the effect of filter vent system in such a total blackout sequence was evaluated. The amount of fission product release was sma...
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Effectiveness Evaluation of Filtered Containment Venting System using THALES-2

1.緒言 福島第一原子力発電所廃炉の課題を克服するためには、数多くの視点から課題を捉える必要がある [1]。前報告では俯瞰的視点で捉えた、燃料デブリ取り出し、廃棄物管理、及び遠隔技術の3分野の要求機能について概念を示した[2]。本報告ではこのうち燃料デブリ取り出しに絞って、どのような工法が有効であるか議論を行う。なお、工法アイデアを創出するためのブレーンストーミングは、原子力技術専門家の他、化学プラント、再処理技術、土木・建築技術、粉塵技術などに関する学内外の専門家の意見を反映して実施した。 2.燃料デブ......
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A new method of fuel debris retrieval with geopolymer for Fukushima Dai-ichi NPP

The mission of decommissioning of Fukushima Dai-ichi NPP is the long-term, complicated and difficult task. In this paper, a new method to retrieve fuel debris using geopolymer will be discussed....
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A new method of fuel debris retrieval with geopolymer for Fukushima Dai-ichi NPP (Phase-2)

Abstract In 2011 at Fukushima Daiichi Nuclear Power Plant, which was a boiling water reactor (BWR), core meltdown occurred. There are control rod guide tubes (CRGTs) in lower plenum of pressure vessel of BWR and it is considered that CRGTs influence behavior of jet breakup of corium. In this research, the experiment about difference of behavior of jet breakup with and without pillar, which simulate CRGTs, and mechanism of difference of behavior of jet breakup in [5] was simulated and analyzed by parti...
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Influence of Control Rod Guide Tubes in Lower Plenum for Behavior of Jet Breakup

The mission of decommissioning of Fukushima Dai-ichi NPP is the long-term, complicated and difficult task. In this paper, technical strategies and expected technical challenges will be discussed for its accomplishment. ...
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Systems thinking for Fukushima Dai-ichi Decommissioning

This paper describes technical issues for the seismic safety of nuclear power plant components and also shows preliminary roadmaps for the solution of the issues. After the Chuetsu-oki earthquake of July 2007, research committees were established in JSME and AESJ for the disc ussion of the effect of the earthquake on NPP components. Ten technical issues due to the earthquake are pointed out and the discussion co ncerning the roadmaps has started to solve each issue. The goal of the activity is for the adva...
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Proposal of R&D Roadmaps for Technical Issues of the Seismic Safety of Nuclear Power Plant Components

After Fukushima Daiich Accident, some international organizations have been discussed on importance of defense in depth (DiD), total comprehensive evaluation contained 14 Safety Factors in PSR (IAEA SSG-25) and HOF (Human and Organization Factors). The NRA allowed review by the IAEA Integrated Regulatory Review Service (IRRS) mission team, over the twice of 2008 and 2016. As a few recommendation examples on above these points to NRA, acquisition of human resources as able talented person and personnel...
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Human resource Development Activities lesson learned International standard after Fukushima Daiichi Accident towards a Proactive Nuclear Regulatory

Abstract Online maintenance is a option of advanced maintenance system started on 2009. With the risk for hardware and software, the online maintenance for important system will be considered to be better than that of offline maintenance. The key issue is the improve ment of software system including the human factor and organizing systems on maintenance....
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Online Maintenance

Japan, as a frequent earthquake country, has a responsibility to resolve efficient measures to enhance nuclear safety, to continue utilizing the nuclear power, based on the risks and importance levels in the scientific and rational manner. In his paper describes how to evaluate the risk of faults movement by engineering approach. An open fruitful discussion by experts in the various areas of earthquake, geology, geotechnical, civil, and a seismic design as well as other stakeholders such as academia prof...
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Risk Evaluation Method for Faults by Engineering Approach (1) Nuclear safety for accident scenario and measures for fault movement