１．はじめに伊方１号機および２号機において、中央制御盤および主要制御盤等の総合デジタル式への更新工事（以下ＣＢＲ（Control Boards Replacement）工事という）を実施した。このような一括更新工事は世界で初めてのものであり、伊方発電所で初めてとなる１,２号機同時定検のもと、平成２１年８月に計画通りに完了した。（図－１）２．工事目的　伊方１号機は昭和５２年９月、伊方２号機は昭和５７年３月から、それぞれ運転を開始して以来、アナログ式の中央制御盤で運転し、これまで装置を部分的に取り替えて機......

Stress corrosion cracking (SCC) behavior of low-carbon stainless steel welds in high temperature water has been discussed with special attention on relation to the characteristics of microstructure. To investigate the effect of .-ferrite on SCC behavior, simulated heat-affected zone (partially melted zone) microstructure, where .-ferrite islands were widely distributed on grain boundary, was made by induction heating up to just below melting point. From the results of constant strain SCC test in high ...
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Effect of .-ferrite on stress corrosion cracking behavior of low-carbon stainless steel weld in high temperature water

Abstract: Crevice corrosion was occurred at the adsorption tower with silver impregnated carbon of Advanced Liquid Processing System (ALPS). The influence of silver impregnated activated carbon on crevice corrosion of 316L stainless steel was investigated by corrosion test and electrochemical measurement. Crevice corrosion was observed on the specimen tested with the activated carbon. On the other hand, no corrosion was observed on that without the activated carbon in both pH7.4 and pH12 solution (art...
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Influence of activated carbon on crevice corrosion in adsorption tower of Advanced Liquid Processing System (ALPS)

SCC behavior near the fusion line of 316L SS welds in high SCC behavior near the fusion line of 316L SS welds in high temperature water has been investigated with special attention on relation to the characteristics of microstructure. Island-type S-ferrite has been distributed on grain boundary, namely along the potential crack path, in partially melted zone of 316L SS weld samples. Most of crack tips have been located on d-ferrite in partially melted zone of both weld samples. Cr2O3 which makes low oxida...
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SCC Retardation Mechanism near Fusion Boundary in 316L SS Welds from Microstructure Point of View

Oxidation behavior and cracking susceptibility of the Ni-Cr alloys (Ni-14Cr, Ni-22Cr and Ni-30Cr) under extremely-low oxygen partial pressure have been investigated by experiments used as plate specimen and Reverse U-Bend (RUB) specimen for 750 hours at 400 °C in two kinds of gas system (inert gas and dry steam) under various oxygen potential (Ni stable, Ni/NiO equilibrium and NiO stable).The Ni-Cr alloys cracked along grain boundary both in inert gas system (with trace O2, without H2O ) and in hydrogenat...
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Oxidation behavior under stress of Ni-Cr alloys in gas phase under extremely-low oxygen potential

Wet polish with fine emery paper is most commonly used for final finish of SCC specimens and corrosion coupons. Although cold w ork introduced by the fine emery finish is slight, a series of experiments have demonstrated that the very slight cold work can ffect oxidation behaviors and apparent SCC susceptibility of Ni base alloys in hydrogenated steam. Oxidation tests and reverse type SCC experiments have been done in hydrogenated steam at 400C for Ni-Cr binary alloys with various Cr content from 14% t o 3...
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Effect of slight cold work introduced with fine emery finish on oxidation and cracking behaviours of Ni base alloys in hydrogenated steam

Corrosion rate of carbon steel SS400 was investigated in test solution (NaClaq, Cl-:200ppm) with a rotating cylinder electrode system. Polarization resistance measurement was used to determine variation of corrosion rate with time and specimens surface were observed after the measurements. Under aerated condition (dissolved oxygen: 7.3ppm), the corrosion rate increased with increasing rotating speed in low rotation speed ranges , but the corrosion rate decreased in high rotating speed ranges. The reas...
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Evaluation of corrosion of cooling system piping of Fukushima Daiichi NPP

It was reported that nitride layer formed on SUS310S heating tubes in the reactor of melamine production plant showed severe spalling susceptibility. After replacement to SUS304heating tubes, spalling and thinning was suppressed. According to previous studies, a crystal structure of the nitrided layers of SUS310S and SUS304 heating tubes mainly consist of γ’ and α’, respectively. The reason why the SUS304 heating tube showed low spalling susceptibility was considered to be a smaller expansion rate of α...
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Wastage mechanism of heating tubes made of austenitic stainless steels in a complex environment of nitriding, oxidizing, and carburizing

In this study, we investigate the effect of oxygen potential on oxide film, intergranular oxidation and cracking susceptibility on nickel base alloy in hydrogenated superheated steam at 400℃. Intergranular cracking occurred at oxygen potential of LOGPO2=-26.32(Ni/NiO equilibrium). In contrast, no cracking occurred at oxygen potential of LOGPO2=-24.09 and LOGPO2=-27.04(near the cracked condition). This result shows that oxygen potential range for cracking susceptibility seemed to be narrow in hydrogenat...
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Effect of oxygen potential on oxide film, intergranular oxidation and cracking susceptibility on nickel base alloy in superheated steam