Analysis for the mechanism of accelerated corrosion on low alloy steel in air-solution alternating condition

Otani, Kyohei; Tsukada, Takashi; Ueno, Fumiyoshi

Materials Transactions, 62(6), p.763 - 769, 2021/06

https://doi.org/10.2320/matertrans.C-M2021816

In this study, the iron rust layer formed on the low alloy steel under air-solution alternating conditions was investigated by cross-sectional observation and analysis, and the mechanism of the accelerated corrosion of the steel under alternating conditions was clarified. The observations and analysis showed that the multilayered iron rust layer composed of the red rust layer (FeOOH), rust crust layer (FeO), inner crystal (FeO), and inner rust layer was formed on the low alloy steel. It can be considered that the multilayered iron rust layer accelerated the cathodic reaction rate of dissolved oxygen under alternating conditions. This acceleration is the reason why the corrosion rate of the low alloy steel under alternating conditions was accelerated.

Study of charged particle activation analysis, 2; Determination of boron concentration in human blood samples

Ikebe, Yurie*; Oshima, Masumi*; Bamba, Shigeru*; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Toyoshima, Atsushi*; Bi, C.*; Seto, Hirofumi*; Amano, Hikaru*; et al.

Applied Radiation and Isotopes, 164, p.109106_1 - 109106_7, 2020/10

https://doi.org/10.1016/j.apradiso.2020.109106

Boron Neutron Capture Therapy (BNCT) is a radiotherapy for the treatment of intractable cancer. In BNCT precise determination of B concentration in whole blood sample before neutron irradiation is crucial for control of the neutron irradiation time and the neutron dosimetry. We have applied the Charged Particle Activation Analysis (CPAA) to non-destructive and accurate determination of B concentration in whole blood sample. The experiment was performed at JAEA Tandem Accelerator using an 8 MeV proton beam. The 478 keV ray of Be produced in the B(p,)Be reaction was used to quantify the B, and rays of Co originating from the reaction with Fe in blood was used to normalize the -ray intensity. The results demonstrated that the present CPAA method can be applied to the determination of the B concentration in the blood sample.

Initial oxidation processes of ultrathin hafnium film and hafnium disilicide islands on Si(100)-21 surfaces studied using core-level X-ray photoelectron spectroscopy

Kakiuchi, Takuhiro*; Yamasaki, Hideki*; Tsukada, Chie*; Yoshigoe, Akitaka

Surface Science, 693, p.121551_1 - 121551_8, 2020/03

https://doi.org/10.1016/j.susc.2019.121551

We investigated the initial oxidation of ultrathin hafnium (Hf) film on Si(100)-21 using photoelectron spectroscopy. Metallic Hf rapidly oxidized, transforming into hafnium dioxide (HfO) and its suboxides. The other HfSi component at the interface was nearly unreactive with O molecules. These facts suggest that the metallic Hf component plays a vital role in the initial oxidation of the ultrathin Hf/Si(100) film. After annealing from 873 K to 973 K, the Hf suboxides in low ionic valences progressed into fully oxidized HfO. Once the annealing temperature reached c.a.1073 K, oxygen atoms were entirely removed from the ultrathin HfO/Si(100) film containing SiO at the interface. Simultaneously, ultrathin HfO layers changed into islands of Hf disilicide (-HfSi) on a bare Si(100)-21 surface. The -HfSi component showed slight reactivity with O molecules at 298 K. In contrast to the initial oxidation of clean Si(100)-21 surface, the dangling bonds on bare Si(100)-21 surface among -HfSi oxidized preferentially.

Sensitivity of charged particle activation analysis for long-lived radioactive nuclide determination

Oshima, Masumi*; Yamaguchi, Yurie*; Asai, Masato; Tsukada, Kazuaki; Goto, Jun*; Bamba, Shigeru*; Bi, C.*; Morimoto, Takao*

Journal of Nuclear Science and Technology, 56(9-10), p.866 - 872, 2019/09

https://doi.org/10.1080/00223131.2019.1593892

Sensitivity of charged particle activation analysis with 8 MeV proton beam was studied for determination of 35 long-lived radioactive nuclides. Reaction cross sections for those nuclides were estimated with ALICE-91 code and isomer yield ratios were estimated from those of neighboring isotopes by taking into account their spins and parities. It was found that the proposed charged particle activation analysis should show high sensitivity for the determination of several hardly measurable nuclides with long half-lives such as Cs, Pu, I, Sn, Mo, Pd, U, Cm, and Np.

STM-induced SiO decomposition on Si(110)

Yano, Masahiro; Uozumi, Yuki*; Yasuda, Satoshi; Asaoka, Hidehito; Tsukada, Chie*; Yoshida, Hikaru*; Yoshigoe, Akitaka

e-Journal of Surface Science and Nanotechnology (Internet), 16, p.370 - 374, 2018/08

https://doi.org/10.1380/ejssnt.2018.370

Radiolysis of mixed solutions of Cl and Br and its effect on corrosion of a low-alloy steel

Hata, Kuniki; Inoue, Hiroyuki*; Kojima, Takao*; Kasahara, Shigeki; Hanawa, Satoshi; Ueno, Fumiyoshi; Tsukada, Takashi; Iwase, Akihiro*

Proceedings of Symposium on Water Chemistry and Corrosion in Nuclear Power Plants in Asia 2017 (AWC 2017) (USB Flash Drive), p.304 - 314, 2017/09

A model simulation of radiolysis of mixed solutions of NaCl and NaBr was carried out. The simulation result agreed well with the experimental result, and Br played an important role in determining the amounts of products from water radiolysis. The simulation result also showed that, in highly pure NaCl solutions, the steady-state concentration of a radolytic product, HO, was mainly controlled by three reactions (Cl + OH ClOH, ClOH Cl + OH, and ClOH + H Cl + HO), which indicated that accurate evaluation of the rate constants of these reactions was very important in improving the radiolysis simulation of solutions containing Cl. An immersion test using a low-alloy steel, SQV2A, in the mixed solutions was also carried out under irradiation. The corrosion rate increased or decreased depending on the pH or the concentrations of the halide ions in a similar way to the change in concentration of HO produced from water radiolysis, which is affected by the presence of Cl and Br. However, at high pH values (12), the corrosion rate was almost zero even though the concentration of HO was high. This could be attributed to enhancement of the passivity of test specimens at higher pH values.

Simulation for radiolytic products of seawater; Effects of seawater constituents, dilution rate, and dose rate

Hata, Kuniki; Sato, Tomonori; Motooka, Takafumi; Ueno, Fumiyoshi; Hanawa, Satoshi; Kasahara, Shigeki; Tsukada, Takashi

Journal of Nuclear Science and Technology, 53(8), p.1183 - 1191, 2016/08

https://doi.org/10.1080/00223131.2015.1096218

Production of Nb and Ta for chemical studies of element 105, Db, using the GARIS gas-jet system

Huang, M.*; Haba, Hiromitsu*; Murakami, Masashi*; Asai, Masato; Kaji, Daiya*; Kanaya, Jumpei*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Kikutani, Yuki*; Komori, Yukiko*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 304(2), p.845 - 849, 2015/05

https://doi.org/10.1007/s10967-014-3877-4

A technique to utilize radioisotopes of Nb and Ta was developed for chemical studies of element 105, Db, by coupling a gas-jet transport system to the RIKEN gas-filled recoil ion separator (GARIS). The short-lived Nb and Ta were produced with nuclear reactions using a F beam whose energy was the same as that to produce Db. Then, they were separated with GARIS and extracted to a chemistry laboratory with the gas-jet transport system. By changing only magnetic field of GARIS and inserting an energy degrader and a shutter for recoil ions, we could deliver the Nb and Ta to a chemistry device for Db without changing other experimental conditions.

Effect of radiolysis on pit initiation of Zircaloy-2 in artificial seawater

Motooka, Takafumi; Komatsu, Atsushi; Tsukada, Takashi; Yamamoto, Masahiro

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 18, 2015/03

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2014-050.pdf#page=50

The effect of changes in water by -ray irradiation on the pit initiation of Zircaloy-2 in artificial seawater was investigated. Surface analysis and electrochemical test were conducted. They showed that the hydrogen peroxide produced by irradiation forms a passive film and the passive film is resistant to the pit initiation.

In-situ measurement of corrosion environment in high temperature water without electrolyte utilizing electrochemical impedance spectroscopy

Sato, Tomonori; Yamamoto, Masahiro; Tsukada, Takashi; Kato, Chiaki

Zairyo To Kankyo, 64(3), p.91 - 97, 2015/03

https://doi.org/10.3323/jcorr.64.91

In the boiling water reactors (BWRs), reactor cooling water is maintained in high purity condition by controlling of a deionizing and deaerating apparatus, however HO contains by water radiolysis. In order to determine the corrosive condition in high-temperature pure water containing HO, the electrochemical impedance spectroscopy was performed in this study. To simulate BWR condition precisely, the measurements were performed without any electrolyte. The obtained impedance responses were changed with the HO concentration. The solution resistance and polarization resistance were determined by the equivalent circuit analyses. The conductivity was determined by the obtained solution resistance and the calculation of the current flow between the working electrode and the counter electrode by the 3-demensional finite element method. The value, 4.410 S/cm, was obtained as the conductivity of the pure water at 288C. The reciprocal of the obtained polarization resistance increased in proportion with HO concentration. This indicates that the corrosion current density was determined by the diffusion limiting current density of HO. The diffusion coefficient of HO at 288C was determined using the relationship between the reciprocal of the polarization resistance and HO concentration. The obtained diffusion coefficient was 1.510 cm/s. This is about twice larger than that of the reported value of O.