In recent years, the formulation of reasonable methodologies to manage and evaluate the safety and integrity of aging nuclear power facilities is the matter of importance for Japanese power utilities to secure stable power supply i n the next few decades. Among possible concerns about aging problems, stress corrosion cracking (SCC) is the one of critical problems to ensure the integrity of boiling water reactors (BWR) and extensive R&D activities are being co nducted.The seismic reliability of nuclear powe...
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Academic-Industry Partnership in R&D Activities on Aging Management and Seismic Reliability Evaluation of BWRs

It becomes to be recognized that material hardening can enhances the SCC growth rate considerably. In SCC growth evaluation in PLR weld joints of BWR, it is confirmed that the material hardening due to thermal shrinkage during welding affects SCC growth rate. In order to ev aluate the degree of hardening of PLR weld joints, Vickers hardness distributions have been measured on some actual pipe joints. In latest researches, however, another parameters such as yield strength and plastic strain are considered ...

It becomes to be recognized that material hardening can enhances the SCC growth rate considerably. In SCC growth evaluation in PLR weld joints of BWR, it is confirmed that the material hardening due to thermal shrinkage during welding affects SCC growth rate. In order to ev aluate the degree of hardening of PLR weld joints, Vickers hardness distributions have been measured on some actual pipe joints. In latest researches, however, another parameters such as yield strength and plastic strain are considered ...

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)

The alternative method to retrieve fuel debris and MCCI (Molten Core Concrete Interaction) products in Fukushima Daiichi Nuclear Power Plants (1F) is proposed based on the hypothesis driven planning. The whole picture of the decommissioning of 1F was discussed with the experts from different fields, taking the end state of 1F into consideration. Though the discussion, we recognized that stabilization of radioactive materials including fuel debris was one of the most important work steps to ensure the...
英字タイトル:
Proposal for the alternative method of the fuel debris retrieval by the hypothesis driven planning

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

背景および概要近年、国内の沸騰水型原子力発電プラント（BWR）炉心シュラウドや再循環系（PLR）配管等の低炭素ステンレス鋼製機器の溶接部で、多数の応力腐食割れ（Stress Corrosion Cracking: 以下、SCC） が確認された［1］。2003年10月には健全性評価制度が法制化され、SCC 等の欠陥が発生した機器についても、機械学会維持規格［2］に基づく技術的評価により健全性が確認されれば継続運転が可能となった。ただし、PLR配管のSCCに ついては、従来の超音波探傷検査（UT）では十分な精......

Inspection on Kashiwazaki-Kariwa Nuclear Power Station after the Niigataken Chuetsu-oki Earthquake in 2007 observed obvious buckling in some fluid storage vessels, the filtrate tanks and de-ionized Water tanks. All vessels with buckling belong to Seismic class C. Contrary the other vessels such as Diesel tanks showed no damage. Those phenomena presumably are brought ab out by differences in the vessels' condition (Vessels geometries, Fluid weight, etc.,) and the seismic load on each vessel. In this study, ...
英字タイトル:
Study on Vessels' Seismic Buckling

In order to retrieve fuel debris on a large scale, it is effective to use Geopolymer to stabilize the fuel debris. In this study, we proposed a new disposal concept for various radioactive wastes and evaluated the barrier material performance and heat generation as wastes when using Geopolymer. As a result, it was shown that the method using Geopolymer was effective in the process from fuel debris retrieval to waste disposal....
英字タイトル:
Proposal on large- scale fuel debris retrieval considering waste management