The Efficiency of Noble Metals in Reducing the Corrosion Potential in the Primary Coolant Circuits of Boiling Water Reactors Operating under Hydrogen Water Chemistry Operation

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概要

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• In order to promote the effectiveness of hydrogen water chemistry (HWC) and to achieve a more effective reduction in electrochemical corrosion potential (ECP) in the primary coolant circuits of boiling water reactors (BWRs), the technology of noble metal chemical addition (NMCA) was brought into practice about 10 years ago. NMCA aims at enhancing the oxidation of hydrogen on metal surfaces and lowering the concentrations of the oxidants (oxygen and hydrogen peroxide) via recombination with hydrogen on the catalyzed surfaces, and therefore reducing the corrosion potentials of the structural alloys in a BWR primary heat transport circuit. Previous research indicates that the effectiveness of NMCA in combination with a low HWC might be evaluated via model predictions of the hydrogen-to-oxidant molar ratio (MH/O) in the primary coolant circuit. If the MH/O at a certain location is calculated to be greater than 2, it is justified that the NMCA would be effective in reducing the ECP to much below the critical potential for Intergranular Stress Corrosion Cracking (IGSCC), EIGSCC, of −0.23 VSHE. However, this statement is true only when the recombination efficiency of hydrogen with oxygen and/or hydrogen peroxide at the location of interest is 100%. Otherwise, significant amounts of oxidants may still be present, even with a stoichiometric MH/O of greater than 2. With the aid of a computer model DEMACE, we explored the impact of incomplete recombination and found that the ECP might be reduced under given circumstances, but not to a great extent, and might remain well above EIGSCC. Accordingly, considerable caution should be exercised upon using the MH/O as a sole indicator for evaluating the effectiveness of NMCA with low HWC as a means of mitigating IGSCC in a BWR. An important finding of this study is that it is necessary to quantify the recombination efficiencies of hydrogen with oxygen and/or hydrogen peroxide on the noble metal treated stainless steel surfaces in order to qualify the use of MH/O as an indicator for NMCA effectiveness in the primary coolant circuit of a BWR.

• 一般社団法人 日本原子力学会の論文
• 2006-10-25

著者

• Yeh Tsung-kuang

  Nuclear Sci. And Technol. Dev. Center National Tsing-hua Univ.

• Macdonald Digby

  Center For Electrochemical Science And Technology Pennsylvania State University

関連論文

• The Influence of ZrO_2 Treatment on the Electrochemical Behavior of Oxygen and Hydrogen on Type 304 Stainless Steels in High Temperature Water
• Impact of Power Uprate on the Water Chemistry in the Primary Coolant Circuit of a Boiling Water Reactor Operating under a Fixed Core Flow Rate
• The Influence of Various Treating Parameters on the Corrosion of ZrO_2-Treated Type 304 Stainless Steels in High-Temperature Water
• The Influence of Dissolved Hydrogen on the Corrosion of Type 304 Stainless Steels Treated with Inhibitive Chemicals in High Temperature Pure Water
• Intergranular Stress Corrosion Cracking of Type 304 Stainless Steels Treated with Inhibitive Chemicals in Simulated Boiling Water Reactor Environments
• Intergranular Stress Corrosion Cracking of Platinum Treated Type 304 Stainless Steels in High Temperature Water
• Electrochemical Corrosion Potential Modeling in the Primary Heat Transport Circuit of the Chinshan Boiling Water Reactor under the Condition of Hydrogen Water Chemistry with Noble Metal Coating
• The Efficiency of Noble Metals in Reducing the Corrosion Potential in the Primary Coolant Circuits of Boiling Water Reactors Operating under Hydrogen Water Chemistry Operation

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