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

Hamaoka nuclear power plant unit-5 had the sea water intrusion incident in 2011 during the shut-down process. We, Chubu electric power company, have conducted some researches for unit-5 re-start, since we had some concerns about the aftercare of pitting corrosions occurred in the inner surface of RPV. The aftercare includes the determination of whether corrosion pitting might propagate until RPV, determination of whether or not to clean Chloride ions in corrosion pits and the determination of need for weld ...
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Weld repair of sea water induced corrosion pits in inner RPV surface

An inside cladding of RPV in Hamaoka-5 caused pitting damage by sea water intrusion in 2011. For a restart of Hamaoka-5, we need a conservative evaluation such that SCC propagates instead of pitting. Two years ago, we reported metallurgical observation results in advance of SCC tests at AESJ conference. This is the progress report describing SCC test results obtained after the AESJ conference....
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A study on corrosion immunity of RPV inside cladding (2) Stress corrosion cracking test

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)

In May 2011, at Hamaoka-5, the main condenser thin tube was damaged and seawater intruded to the reactor facility. It was purified to a level where corrosion did not occur by replacing the intruding water. However a few years later, the leak occurred from the stainless steel welded joint. It is presumed that the cause is that crevice corrosion was caused by the welded part of stainless steel with high corrosion sensitivity, the inflow of chloride ions, and the crud deposits. And in this study, we aim to elu...
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Elucidating the corrosion of the stainless steel welded joint caused by seawater intrusion at Hamaoka-5

Fact finding survey of actual RPV in decommissioning Hamaoka-1 has been under conducting. All boat samples was already transported to a domestic post irradiation examination facility (NFD). At NFD, irradiated materials were investigated as introduced in the 15th JSM conference. This is the progress report describing new results obtained after the conference....
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Research on reactor pressure vessel in Hamaoka-1 (Part 2) - Material research utilizing decommissioning NPS -

Fact finding survey of actual reactor pressure vessel in decommissioning Hamaoka nuclear power station has been conducted. All boat samples was already transported to a domestic post irradiation examination (PIE) facility. During the PIE, un-irradiated archive materials was also investigated for better understanding of cladding HAZ in base metal, as introduced in the 14th JSM conference. This is the progress report describing some new results obtained after the conference....
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Research on reactor pressure vessel in Hamaoka Unit 1 - Material research utilizing decommissioning NPS -