Water environment improvement (ex. Hydrogen Water Chemistry (HWC)) is carried out for Stress Corrosion Cracking (SCC) mitigation in some of BWR plants. Japan Nuclear Technology Institute (JANTI) has the guideline on the inspection programs based on effectiveness of environmental SCC mitigation technique for BWR core internals. The guideline provides the crack growth rate (CGR) under HWC. Although CGR is defined by ECP (electroch emical corrosion potential), a dealing of evaluation of ECP and the HWC avail...
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The Guideline of evaluating the effectiveness of environmental improvementby Hydrogen Water Chemistry

In this paper, pipe-wall thinning phenomenon behind an orifice in a circular pipe is studied by measuring the mass transfer coefficient along the pipe wall by naphthalene sublimation method. An attention is placed on the asymmetrical pipe-wall thinning phenomenon behind an orifice under the influence of swirling flow and allowable orifice bias. The present measurement indicates that the mass transfer coefficient becomes asymmetric about the pipe axis behind the orifice in certain combinations of swirl...
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Investigation on Pipe-wall Thinning by Flow-accelerated Corrosion (Mass Transfer Phenomenon by Combined Effect of Swirling Flow and Orifice Bias)

We have been engaging tsunami countermeasures including tsunami protection wall at Hamaoka Nuclear Power Station since the Great East Japan Earthquake disaster. In the design of the wall, the innovative structure type integrated L-shaped wall sections of SRC and steel structure on RC underground wall foundations implanted into solid bedrock was developed. This structure gives an extra safety margin to seismic-resistant and tsunami-resistant design. Moreover we achieved to shorten the construction term...
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Design and Construction of "Tsunami Protection Wall" at Hamaoka Nuclear Power Station

In nuclear power plants, stress corrosion cracking has been observed near the weld zone of the primary loop recirculation pipes made of low-carbon austenitic stainless steel Type 316L. Residual stress is important factor in the occurrence and propagation of SCC. The joining process of pipes usually includes surface machining and welding, and both processes induce residual stresses. In this study, FEM was used to estimate residual stress distributions generated by butt welding and surface machining. In addi...
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Evaluation of Residual Stress Distribution due to Welding and Surface Machining and Crack Growth Behavior

This study is considering the effect of clamp conditions on welding deformation and residual st ress distribution. Welding deformation and residual stress becomes initial imperfections, and i t causes structures weak so it must be controled. The result of numerical analysis shows that an appropriate conditions should be chosen by considering welding distortion and residual stress....
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Effect of condition of clamp on deformation and residual stress in welding

This study shows the effect of the low transformation temperature welding material on residual stress listribution and welding deformation. The expansion due to the transformation fr om austenite to martensite nduces the compressive residual stress around welds. While, in the welding structures, it is important to control the welding deformation and residual stre ss so that they may cause the strength decrease. By using he low temperature transformation welding wire, it may be possible to decrease the weld...
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Numerical simulation of mechanical properities at welding and repairing

In this study, a fast simulation technique of Iterative Substructure Method (ISM) was applied for numerical analysis of the distribution of residual stress by J-weld and repair weld of Bottom Mounted Instrument (BMI) nozzle in reactor vessel penetration. The calculated results were compared with the measured values to validate the constructed residual stress analysis model. The effect of BMI mounting angles on distribution of residual stress at J-welds was investigated. Based on the results, similarity and...
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Numerical Analysis of Residual Stress by J-weld and Repair Weld of Bottom Mounted Instrument Nozzles in Reactor Vessel Penetration

高温ガス炉の開発は 1960年代前半に米国、ドイツで始まった。日本では、当時の日本原子力研究所において 1969年に新たな原子力プロジェクトとして、発電のみならず、製鉄や化学工業用の熱源としても利用可能な多目的高温ガス炉の研究開発が開始された。当時は、ドイツのユーリッヒ研究所や米国の原子力規制委員会、エネルギー省等と協力しつつ研究開発を進め、1991年から HTTRの建設が始まった。 HTTRの建設及び運転保守を通して、日本独自の高温ガス炉技術を蓄積し、現在は日本の高温ガス炉技術の国際展開・国際標準化を目指した協力を進めている。本稿では、世界の高温ガス炉開発の現状について紹介し、それらの国と原子力機構が進めている協力について説明する。最後に、これらの協力を通した日本の高温ガス炉技術の国際展開の考えを示す。...

If the wireless communication is feasible in the concrete structure of power plants, it is effective for us to reduce the construction cost, improve the placement of equipment and change facilities easily. In buildings of such a power plant, the reinforced concrete (RC) walls might be more than one meter in thickness, with high rebar density. Therefore, radio wave transmission over this kind of concrete walls was studied to discuss feasibility. Aperture parts of walls, such as doors, whose thickness is ...
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A feasibility study of the transmission radio wave over the reinforced concrete structure in the buildings of power plants for wireless network

This paper studies the effect of initial residual stress on high-precision manufacturing for infrastructure integrity technology. Welding distortion decreases the strength of welded structure. Straightening causes secondary deformation. Althogh welding distortion should be reduced, handling welding distortion is difficult. One of the reason is the dispersion o f cutting and welding distortion. In one of the contributing factor there are an influence of initial residual stress. When the equalization of init...
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Investigation of high-precision manufacturing for infrastructure integrity technology