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Uchida, Shunsuke; Hanawa, Satoshi; Kysela, J.*; Lister, D. H.*
Power Plant Chemistry, 18(1), p.6 - 17, 2016/01
In order to establish reliable NPP operation, each plant requires its own unique optimal water chemistry control based on careful consideration of its system, materials and operational history. Electrochemistry is one of key issues that determine corrosion related problems, e.g., FAC. Based on the relationships among ECP, metal surface conditions and exposure time, a model to evaluate ECP and corrosion rate of steel was developed by coupling an electrochemical model and an oxide layer growth model. Major conclusions are as follows. (1) The effects of water chemistry improvement and mass transfer coefficients due to local flow velocity on FAC wall thinning rate and ECP could be evaluated with the proposed model. (2) The effects of H
O and O concentrations on ECP were evaluated with the model. Exposure time dependent ECPs were also explained as the effects of oxide film growth on the specimens. (3) Decreases in ECP due to neutron exposure were explained by radiation-induced diffusion in the oxide layers.
Uchida, Shunsuke; Hanawa, Satoshi; Nishiyama, Yutaka; Nakamura, Takehiko; Sato, Tomonori; Tsukada, Takashi; Kysela, J.*
Nuclear Technology, 183(1), p.119 - 135, 2013/07
Times Cited Count：5 Percentile：38.62(Nuclear Science & Technology)In-pile loop experiments are one of the key technologies which can provide an understanding of corrosion behaviors of structural materials in nuclear power plants (NPPs). The experiments should be supported not only by reliable measurement tools to confirm corrosive conditions under neutron and 
ray irradiations but also by theoretical models for extrapolating the measured data to predict corrosion behaviors in NPPs. The relationships among electrochemical corrosion potential (ECP), metal surface conditions, exposure time and other environmental conditions have been determined from in situ measurements of corrosion behaviors of stainless steel specimens exposed to HO and O in high temperature water. Based on the relationships, a model to evaluate ECP of stainless steel was developed by coupling an electrochemical model and a double oxide layer model. Major conclusions obtained from the evaluation model are as follows. (1) The difference in ECP behaviors of the specimens exposed to HO and O were mainly from the thickness and developing rate of the inner oxide layers. (2) Calculated ECP behaviors, e.g., the different responses to HO and O and hysteresis and memory effects, agreed with the measured ones. (3) Neutron exposure might decrease ECP due to radiation-induced diffusion in the oxide layer. The ECP evaluation model will be applied to evaluation of corrosive conditions in the JMTR in-pile loop.
Hanawa, Satoshi; Nakamura, Takehiko; Uchida, Shunsuke; Kus, P.*; Vsolak, R.*; Kysela, J.*; Sakai, Masanori*
Nuclear Technology, 183(1), p.136 - 148, 2013/07
Times Cited Count：2 Percentile：18.63(Nuclear Science & Technology)no abstracts in English
ray in in-pile loop and their data evaluation by water radiolysis calculationsHanawa, Satoshi; Nakamura, Takehiko; Uchida, Shunsuke; Kus, P.*; Vsolak, R.*; Kysela, J.*
Proceedings of 2010 Nuclear Plant Chemistry Conference (NPC 2010)/8th International Radiolysis, Electrochemistry & Materials Performance Workshop (CD-ROM), 10 Pages, 2010/10
In order to establish reliable electrochemical corrosion potential (ECP) sensors for applying in reactor core peripherals of power plants, performance tests of sensors under irradiation were carried out in the in-pile loop of the experimental reactor, LVR-15, at the Nuclear Research Institute (NRI) in Czech Republic. Responses of different kinds of sensors under neutron and irradiation conditions have been compared each other. Corrosive conditions along the in-pile loop were calculated by water radiolysis calculation code, WRAC-J and calculated corrosive conditions were compared with the measured results. As a result of the evaluation, it was confirmed that the ECP sensors could be applied to irradiation conditions of reactor peripherals, while the water radiolysis model could be also applied for evaluation of corrosive conditions of reactor peripherals.
Hanawa, Satoshi; Nakamura, Takehiko; Uchida, Shunsuke; Kus, P.*; Vsolak, R.*; Kysela, J.*
Proceedings of 2010 Nuclear Plant Chemistry Conference (NPC 2010)/8th International Radiolysis, Electrochemistry & Materials Performance Workshop (CD-ROM), 10 Pages, 2010/10
In-pile ECP measurements data was evaluated by water radiolysis calculations. The data was obtained by using in-pile loop in an experimental reactor, LVR-15, at the Nuclear Research Institute (NRI) in Czech Republic. Three types of ECP sensors, a Pt electrode, an Ag/AgCl sensor and a zirconia membrane sensor containing Ag/AgO were used at several levels of the irradiation rig at various neutron flux and rates. Concentration of chemical species along the water flow was calculated by a radiolysis code, WRAC-J. The radiolysis calculation results were transferred to an ECP model. In the model, anodic and cathodic current densities were calculated with combination of an electrochemistry model and an oxide film growth model. The measured ECP data were compared with the radiolysis/ECP calculation results, and applicability of radiolysis model was confirmed.
Hanawa, Satoshi; Nakamura, Takehiko; Uchida, Shunsuke; Kysela, J.*
no journal, ,
no abstracts in English
Hanawa, Satoshi; Nakamura, Takehiko; Uchida, Shunsuke; Kysela, J.*
no journal, ,
no abstracts in English
