Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Otani, Kyohei; Kato, Chiaki
no journal, ,
Cooling water is circulated and injected into the containment vessel (PCV) of Fukushima Daiichi Nuclear Power Station (1F) Units 1-3, and nitrogen gas is injected and filled to prevent hydrogen explosion and to control corrosion of steel materials. In order to maintain the integrity of the PCV facilities over a long period of time until the decommissioning of the reactors, it is necessary to predict the corrosion behavior of carbon steel, which is the main structural material, and in particular to study the factors that may accelerate corrosion. From the internal investigation of the PCV, it was confirmed that carbon steel, which is the material inside the PCV, is exposed to an environment in which the gas and liquid environments alternate near the air/solution interface (Air/solution alternating environment). It has been reported that metallic materials are covered with a thin liquid film near the air/solution interface, and that the corrosion rate of steel is accelerated when there is a thin water film on the steel surface compared to that in solutions. In this presentation, the corrosion test of carbon steel was conducted using a rotating corrosion test apparatus to simulate the air/solution alternating environment inside the 1F PCV, and the corrosion rate and corrosion mechanism of carbon steel obtained from the results of mass measurement, observation and analysis will be presented.
and 
rays emitted from radionuclides in fuel debris on water radiolysisHata, Kuniki; Sato, Nobuaki*; Sato, Tomonori; Kato, Chiaki
no journal, ,
To understand the corrosive environment in a PCV after severe reactor accident in detail and prevent any problems relating to corrosion, the effects of radiation on corrosion is needed to be discussed. Especially, the special corrosive environment would be formed near nuclear fuel debris due to and rays emitted from radionuclides. The local high-energy deposition of and rays induces water radiolysis, which would be different from that induced by 
ray. These radiation effects are dependent on the configuration of fuel debris. Thus, in this study, the types of fuel debris were classified as oxide debris, alloy debris, MCCI debris and so on, and some input parameters for radiolysis calculation, such as dose rate distribution, were estimated. Then, the radiolysis simulation was carried out to understand the generation behavior of oxidative species produced by water radiolysis. The result showed that the concentration of hydrogen peroxide, which was an oxidative product from water radiolysis, was homogeneously distributed far beyond the radiation distance of ray.
Soma, Yasutaka; Komatsu, Atsushi; Kato, Chiaki
no journal, ,
Electrochemical environment within a crevice which is referred to as crevice (or crack) water chemistry is an important factor for understanding stress corrosion cracking (SCC) of stainless steels in high temperature water. There have been many studies and well-organized reviews on the crevice water chemistry. However, the measurement of the real-time behavior of crevice water chemistry as a function of potential (electrochemical potential, ECP) remains a major challenge. In this study, the in situ measurement of the electrical conductivity of the solution inside crevices, 
was carried out to analyzed -ECP relationship.