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

Pipe wall thinning is one of the important degradation phenomena taking place in the nuclear power plant. Major mechanism of the mainly pipe wall thinning is Flow Accelerated Corrosion (FAC), where chemical process plays the primary role. But mechanism of FAC is not yet full y understood. Especially characteristics of oxide film formed in FAC is not well known although oxide film property would be strongly related to thinning rate in FAC. The main objective of this work is finding characteristics of oxide ...
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Relation of Thinning Rate and Characterization of The Oxide Film Formed in Flow Accelerated Corrosion of Carbon Steels

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

In order to proceed the decommissioning of the FuNushima Daiichi Nuclear Power Plant safely, it is important to maintain integrity of cooling system for fuel debris and spent fuels. Most part of the piping systems are made of carbon steel. This study has been done to understand rate-determining processes of carbon steel corrosion under current and future FuNushima Daiichi NPP conditions as functions of flow conditions and dissolved oxygen level by using electrochemical tests with rotating cylindrical ...
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Corrosion behavior of carbon steels under flow and its rate-determining processes 渡邉 豊 YutaNa WATANABE Member

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

The core shroud specimens (316L stainless steel) were used to characterize the surface hardening layer introduced by machining and to evaluate the SCC susceptibility in the simulated BWR coolant environment. Based on the results obtained, the effect of the surface hardening layer on the SCC susceptibility and its mechanism are discussed. It is suggested that the wall part has clearly higher SCC susceptibility than the support ring part when compared between the as-received materials (with surface hardening ...
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Evaluation of SCC susceptibility of austenitic stainless steel with surface hardening layer in high-temperature water

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