Development of a Suppression Method for Deposition of Radioactive Cobalt after Chemical Decontamination: (I) Effect of the Ferrite Film Coating on Suppression of Cobalt Deposition

Hosokawa, Hideyuki; Nagase, Makoto; Fuse, Motomasa

doi:10.3327/jnst.47.531

Cited by 7 publications

(10 citation statements)

References 8 publications

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“…In our previous studies [4][5][6][7], we confirmed that the Fe 3 O 4 film is effective to suppress 60 Co deposition after chemical decontamination under normal water chemistry condition (NWC) and hydrogen water chemistry condition (HWC). For the Hi-F, laboratory experiments confirmed that the 60 Co deposition reduction effects under NWC and HWC were 1/5 and 1/4, respectively, compared to non-treatment for up to 3100 h, and about 60 μg/cm 2 was a sufficient amount of film formation to get a lower 60 Co deposition.…”

Section: Introductionsupporting

confidence: 59%

“…Therefore, we developed the Hitachi ferrite coating film process (Hi-F) to reduce the recontamination by 60 Co after the chemical decontamination * Corresponding author. Email: tsuyoshi.ito.jw@hitachi.com [4][5][6]. Following the chemical decontamination, a fine Fe 3 O 4 coating film is formed on the stainless steel base metal of the piping.…”

Section: Introductionmentioning

confidence: 99%

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Development of a suppression method for deposition of radioactive cobalt after chemical decontamination: (III) the suppression mechanism with preoxidized ferrite film for deposition of radioactive cobalt

Ito

Hosokawa

Nagase

et al. 2013

Journal of Nuclear Science and Technology

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The Hitachi ferrite coating film process (Hi-F) has been developed to lower recontamination after chemical decontamination. In this process, the chemical decontamination process is carried out, and a fine Fe 3 O 4 coating film is formed on the surface of stainless steel piping in an aqueous solution. In order to improve the suppression of 60 Co deposition further, we combined the original Hi-F with a preoxidation step. We found the deposited amount of 60 Co with preoxidized Hi-F coating film (OHi-FC) was 1/10 of that for non-coated specimens. In this study, we investigated the suppression mechanism of 60 Co for the OHi-FC. The composition of OHi-FC was changed from Fe 3 O 4 to Fe 2 O 3 and then the crystals in the OHi-FC grew three times larger than those of the original Hi-F coating film. Consequently the corrosion amount of the stainless steel base metal was reduced by getting larger grains in the coating film. Because 60 Co was incorporated into the corrosion oxide, the suppression effect of 60 Co deposition by preoxidation was attributed to the suppression of the formation of the corrosion oxide by the OHi-FC.

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Section: Introductionsupporting

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Development of a suppression method for deposition of radioactive cobalt after chemical decontamination: (III) the suppression mechanism with preoxidized ferrite film for deposition of radioactive cobalt

Ito

Hosokawa

Nagase

et al. 2013

Journal of Nuclear Science and Technology

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“…One of the latest achievements for mitigating recontamination is Hi-F Coat, in which a ferrite film coated on the decontaminated surfaces during serial decontamination procedures in plants [63]. The Hi-F Coat technology is a kind of pre-oxidation treatment for mitigating radioactive corrosion product build-up ( Figure 13(b)), which was awarded the 2010 AESJ Technical Progress Award in connection with HOP decontamination.…”

Section: Decontamination Measures and Prevention Ofmentioning

confidence: 99%

Water chemistry technology – one of the key technologies for safe and reliable nuclear power plant operation

Uchida

Katsumura

2013

Journal of Nuclear Science and Technology

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Water chemistry control is one of the key technologies to establish safe and reliable operation of nuclear power plants. Continuous and collaborative efforts of plant manufacturers and plant operator utilities have been focused on optimal water chemistry control, for which, a trio of requirements for water chemistry should be simultaneously satisfied: (1) better reliability of reactor structures and fuel rods; (2) lower occupational exposure and (3) fewer radwaste sources. Various groups in academia have carried out basic research to support the technical bases of water chemistry in plants. The Research Committee on Water Chemistry of the Atomic Energy Society of Japan (AESJ), which has now been reorganized as the Division of Water Chemistry (DWC) of AESJ, has played important roles to promote improvements in water chemistry control, to share knowledge about and experiences with water chemistry control among plant operators and manufacturers and to establish common technological bases for plant water chemistry and then to transfer them to the next generation of plant workers engaged in water chemistry. Furthermore, the DWC has tried and succeeded arranging R&D proposals for further improvement in water chemistry control through roadmap planning. In the paper, major achievements in plant technologies and in basic research studies of water chemistry in Japan are reviewed. The contributions of the DWC to the longterm safe management of the damaged reactors at the Fukushima Daiichi Nuclear Power Plant until their decommissioning are introduced.

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“…We developed a new way to reduce the recontamination after the chemical decontamination to maintain longterm continued decontamination effects without any chemical injections or chemical controls in reactor water during operation. 8,9) In our approach, a fine ferrite film is formed by the Hitachi ferrite coat process after the oxide films formed during the plant operation are removed by the chemical decontamination process. The corrosion rate of the SS piping during plant operation cycles is reduced by this fine coating that blocks both the diffusion of an oxidant in the reactor water to the base metal and that of metal ions in the oxide film to plant water.…”

Section: Introductionmentioning

confidence: 99%

“…We had two reasons for the choice of formic acid. 8) First, because chloride and sulfate ions affect the stress corrosion cracking of SS under power plant conditions, especially nuclear power plant conditions, we chose an organic acid. The second reason is that the amount of film formation for formic acid is larger than those for other organic acids.…”

Section: Introductionmentioning

confidence: 99%

Development of a Suppression Method for Corrosion of Carbon Steel by Double-Layer Ni Metal-Ni Ferrite Film

Ito

Hosokawa

Nagase

et al. 2011

J. Nucl. Sci. Technol.

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Water pH control or dissolved oxygen (DO) in water control is being applied to many thermal and nuclear power plants in order to reduce the corrosion of carbon steel (CS). In the former, a continuous pH adjuster, such as hydrazine, is injected into water during plant operation cycles, and in the latter, oxygen gas is injected into water and is controlled during plant operation. Then, we developed the Hitachi ferrite coating (Hi-F Coat) process to suppress the corrosion of CS in plant operation cycles without pH or DO control. In this process, a fine oxide film is formed on the CS base metal of the piping in solution at 363 K. In this study, we developed a method to form a double-layer Ni metal-Ni ferrite film to suppress the corrosion amount of CS in water. In this process, a double-layer film is formed on the base metal of the piping using four chemical reagents in solutions, Fe(HCOO) 2 , Ni(HCOO) 2 , H 2 O 2 , and N 2 H 4 at 363 K. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy measurements of the film show a close-packed double-layer thin film formed in the amount of 3.6 g/m 2 . The inner layer is mainly Ni metal and the outer layer is Ni 0:7 2þ Fe 0:3 2þ Fe 2 3þ O 4 . After adding the four chemical reagent solutions, Ni 2þ ions were reduced on the CS surface and a Ni metal film was formed on the base metal. Then, a Ni 0:7 Fe 0:3 Fe 2 O 4 film was formed on the CS surface by oxidation of Fe 2þ to Fe 3þ with H 2 O 2 . We confirmed that the respective corrosion amounts were reduced to 1/5 and 1/2 compared with those obtained without and with oxygen injection at 423 K. Furthermore, we analyzed the film after a corrosion test. The double-layer film changed to a Ni 0:7 Fe 0:3 Fe 2 O 4 single-layer film. There is the possibility that the transformation from the double-layer film to the single-layer film reduced the corrosion of CS by preventing the diffusion of Fe ions from base CS to high-temperature water.

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Development of a Suppression Method for Deposition of Radioactive Cobalt after Chemical Decontamination: (I) Effect of the Ferrite Film Coating on Suppression of Cobalt Deposition

Cited by 7 publications

References 8 publications

Development of a suppression method for deposition of radioactive cobalt after chemical decontamination: (III) the suppression mechanism with preoxidized ferrite film for deposition of radioactive cobalt

Development of a suppression method for deposition of radioactive cobalt after chemical decontamination: (III) the suppression mechanism with preoxidized ferrite film for deposition of radioactive cobalt

Water chemistry technology – one of the key technologies for safe and reliable nuclear power plant operation

Development of a Suppression Method for Corrosion of Carbon Steel by Double-Layer Ni Metal-Ni Ferrite Film

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