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......
英字タイトル:
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, technical strategies and expected technical challenges will be discussed for its accomplishment. ...
英字タイトル:
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 this study, an alternative method to retrieve fuel debris and MCCI (Molten Corium Concrete Interaction) products in Fukushima Daiichi Nuclear Power Plants is proposed, where geopolymer is used for semi-stabilization of those debris. Facing the realization of this method, the fluidity and the setting time of geopolymer are regarded as one of the problems. Thus, for investigating those properties, slump flow experiment, funnel experiment and viscosity measurement will be done. In addition, the experimen...
英字タイトル:
Study on application of geopolymer to decommissioning of Fukushima Dai-ichi Nuclear Power Plant

1. 緒 言電気事業法の改正により、2003年10月より原子力発電設備の維持基準が導入された。これに伴い発電事業者は法定の「定期事業者検査」を実施すること、また、き裂等の欠陥を発見した場合、当該機器の運転を継続するためには、欠陥の進展を予測し、機器の構造健全性を確認することが義務付けられた［1］。本稿では、近年、国内の沸騰水型原子力発電プラント（以下、BWR）の低炭素ステンレス鋼製炉心シュラウドで多くの事例が確認された応力腐食割れ（以下、SCC）を例に、機械学会維持基準［2］に基づく構造健全性評価の考え方......

L-grade stainless steels such as 316NG, SUS316L and SUS304L are used for the BWR reactor internals and re-circulation pipes. The L-grade stainless steels are known as typical SCC resistant materials because they are hardly thermally sensitized in usual welding process due to its lower carbon contents. However SCC of the L-grade material components were recently reported. This paper summarizes the recent knowledge and reports about the SCC behavior of L-grade stainless steels and its mitigation and ...
英字タイトル:
Stress corrosion cracking of L-grade stainless steel in high temperture water