Chemical anchor is a glue-type anchor and it has been used to fix components to concrete structures in nuclear power plant. Decrease in adhesive power of glue is supposed to occur due to a construction failure or a long term use under various environments in actual plant. We have begun some internal researches and selected Acoustic Emission method (AE) as a non- destructive inspection tool among some methods. The AE method was selected by a comparison of some methods, and then the methodology was brushed...
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Development of inspection method for chemical anchor

Many anchor bolts have been used for fixing many components in nuclear power plant (NPP), securing safety against seismic ev ents. Some methods have been developed to detect crack-like defects in bolts which may occur after seismic events. On the ot her hand, assuming long term use of NPP, a method to detect bolt thinning was thought to be needed. In this study, by using bolt specimens with an artificially grinded portion, a new method to detect thinning and to measure its depth was developed....
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Development of inspection method for thinned bolts by PA-UT

Anchor bolts have been used to fix components in nuclear power plant to concrete structure. Bolt thinning is supposed to occur under long term operation of nuclear power plant in corrosive environments and requires a development of nondestructive inspection method. We have begun some internal researches since 2009 and developed a unique PA-UT method using delayed echoes. Additional works were conducted recently to show its performance such as a detectable maximum defect length and depth, which are rep...
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Development of inspection method for thinned bolts by PA-UT (2)

An investigation of RPV and concrete structure in Hamaoka unit-1 have been started since 2014. Objective of the investigation is to contribute to the optimization of plant maintenance methodology by development of maintenance technologies such as non-destructive inspection and small specimen technique. This report describes some results obtained at present. ...
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Status of the research using materials in decommissioning Hamaoka NPS Unit 1 (3)

Hamaoka Nuclear Power Station Unit 1 and 2 have already started the plant decommissioning since November, 2009. The decommissioning Stage-1 (preparation stage) had been already finished and now Stage-2 (Dismantling stage of Reactor Zone Peripheral facilities) is in progress. We have begun a research about material degradation by using some pieces of concrete and metal taken from Unit 1. This report describes the project scheme of the research. ...
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Project Status of Decommissioning and Research Hamaoka NPS Unit 1 and 2 (2)

This study aims at proposing a novel magnetic testing method, eddy current magnetic signature method for evaluation of residual strain in carbon steels. This method characterize the eddy current magnetic signatures that is eddy current signals in an impedance plain during magnetization process. In order to discuss the feasibility of this method, eddy current magnetic signatures of a set of tensile test specimens are investigated. The relationship between eddy current signature and plastic deformation is di...
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Nondestructive Evaluation of Residual Strain in Carbon Steels by Eddy Current Magnetic Signature Method

The ductile-brittle transition behavior of neutron-irradiated welded A533B Cl.1 steel has been studied by means of small specimen test technique for discussing the specime n size effects on the impact properties. Standard size, one-third size and 1.5mm size Charpy V-notch specimens were prepared. Neutron irradiation was performed in JMTR wit h fluencies up to 0.75 and 1.3 X 1024 n/m°(E>1 MeV). Normalization of the USE is done by a curve fitting method and the USE of different size of specimens can be expre...
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Evaluation Technique of Neutron-Irradiation Embrittlement in Welded RPV

The degradation of 1-nozzle type Jet Pump (JP) efficiency by crud deposition has been recognized in some BWRs. In order to remove crud, we must clean each o r all of JP inner surface. The increase in cleaning surface area induces the increase in outage period and cost, therefore, in the previous study we looked for the most effective cleaning portion at inner surface for efficiency recovery. In this study, for the 5-nozzle type JP, we evaluated the effect of crud portion on decrease in efficiency of 5-noz...
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Studies on Recovering Method of 5-nozzle type Jet Pump Efficiency