BWR plants with low shutdown radiation level. Design and construction of plants and current experience with occupational exposure of plants.

Uchida, Shunsuke; Miki, Masayuki; Masuda, Takahisa; Nagao, Hiroyuki; Otoha, Keiichi

doi:10.3327/jnst.24.593

Cited by 10 publications

(7 citation statements)

References 1 publication

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“…11,12) Cobalt-60 is activated by 59 Co released from structure materials and is deposited on the fuel cladding outer surfaces to become the main source of shutdown dose rate. 13,14) This 60 Co is released into the reactor water and deposits onto such pipe surfaces as the primary loop recirculation pipes. Dissolution rate of 60 Co on fuel cladding outer surfaces and deposition rate on the pipe surfaces increase in HWC.…”

Section: Introductionmentioning

confidence: 99%

Hydrazine and Hydrogen Co-injection to Mitigate Stress Corrosion Cracking of Structural Materials in Boiling Water Reactors, (I) Temperature Dependence of Hydrazine Reactions

Ishida

Wada

Tachibana

et al. 2006

Journal of Nuclear Science and Technology

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Hydrazine and hydrogen co-injection into reactor water is considered a new mitigation method of stress corrosion cracking in BWRs. Fundamental data such as the thermal decomposition of hydrazine, the reaction of hydrazine with oxygen and with hydrogen peroxide at temperatures ranging from 150 to 280 C are needed to evaluate suitability of this method. Reactions in bulk water were studied in a polytetrafluoroethylene pipe to separate surface reaction effects. The results were as follows. (1) The orders of the apparent reaction rate of hydrazine with oxygen were 1 and 0.5 for hydrazine and oxygen concentrations, respectively (À . Based on these data, the applicability of hydrazine and hydrogen co-injection into BWRs was considered. Hydrazine introduction to reactor water was confirmed to be accompanied by only 1% decomposition. The concentration of oxygen, which is injected to suppress the flow-assisted corrosion of carbon steel in current BWR operation, would decrease due to the reaction of hydrazine with oxygen. However oxygen concentration in feed water could be maintained at the required level if the concentration of oxygen injected in condensate water was at most doubled compared to the current operating concentration.

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Section: Introductionmentioning

confidence: 99%

Hydrazine and Hydrogen Co-injection to Mitigate Stress Corrosion Cracking of Structural Materials in Boiling Water Reactors, (I) Temperature Dependence of Hydrazine Reactions

Ishida

Wada

Tachibana

et al. 2006

Journal of Nuclear Science and Technology

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“…Ferrous ions in the water are easily oxidized to become oxide particles and fed into the reactor water with cobalt ions to deposit on fuel surface. Iron crud enhances cobalt deposition as cobalt ferrite (CoOFe 2 O 3 ) on the fuel surface and then generation of 60 Co, while too low an amount of iron crud causes cobalt deposition as cobalt mono-oxide (CoO) on the fuel surface, which easily dissolves into the water, and then ionic 60 Co radioactivity increases [31]. To minimize shutdown dose rate, two approaches have been proposed for this competition (Figure 8).…”

Section: Bwrsmentioning

confidence: 99%

“…When it is suppressed as low as possible, ionic 60 Co radioactivity increases but at the same time [Ni] also increases, which causes a lower cobalt deposition rate on the piping inner surface and then 60 Co deposition can be controlled at the minimum level. These different approaches for dose rate reduction with the same final goal are applied for operating power plants [31].…”

Section: Bwrsmentioning

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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“…14) In this paper, we propose one method to reduce the dose rate in HWC operation. As suggested in the previous chapter, the prefilming in NWC operation prior to switching to HWC is quite effective in suppressing the Co-60 deposition on the piping.…”

Section: Countermeasure To Suppress Co-60 Deposition Under Hwc Plantmentioning

confidence: 99%

Effects of Hydrogen Peroxide on Cobalt Deposition Rate on Primary Cooling System of Boiling Water Reactors

Usui

Fuse

Hosokawa

et al. 2008

J. Nucl. Sci. Technol.

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Experimental data of radioactivity deposition rates on stainless steel specimens exposed to high-temperature water including hydrogen peroxide (H 2 O 2 ) and oxygen (O 2 ) were applied to the evaluation of Co-60 accumulation rates in oxide films on the stainless steel piping of a boiling water reactor (BWR) primary cooling system and then an empirical formula of Co-60 deposition rate coefficient was proposed as a function of exposure time. The empirical formula was applied to the evaluation of the amount of Co-60 deposition on the stainless steel piping of BWR primary cooling systems under normal water chemistry (NWC) and hydrogen water chemistry (HWC) conditions. The results are summarized as follows. 1) The Co-60 deposition rate coefficient was almost independent of2) The proposed empirical formula determined on the basis of experiments under H 2 O 2 conditions could give a much better estimation of the Co-60 deposition rate coefficient on stainless steel under NWC conditions of BWR than the previous formula based on the data under simple O 2 conditions.3) The deposition amounts of Co-60 on stainless steel piping under HWC conditions were evaluated using the formula, which suggested that those without any prefilming treatment were several times as high as those under NWC conditions. 4) The increase in Co-60 deposition under HWC conditions was caused by the less protective film in mitigating Co-60 deposition and it could be avoided by several hundred hours of operation under NWC conditions prior to HWC operation. The effect on material integrity is evaluated to be negligible.

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BWR plants with low shutdown radiation level. Design and construction of plants and current experience with occupational exposure of plants.

Cited by 10 publications

References 1 publication

Hydrazine and Hydrogen Co-injection to Mitigate Stress Corrosion Cracking of Structural Materials in Boiling Water Reactors, (I) Temperature Dependence of Hydrazine Reactions

Hydrazine and Hydrogen Co-injection to Mitigate Stress Corrosion Cracking of Structural Materials in Boiling Water Reactors, (I) Temperature Dependence of Hydrazine Reactions

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

Effects of Hydrogen Peroxide on Cobalt Deposition Rate on Primary Cooling System of Boiling Water Reactors

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