A Review on the Odscc of Steam Generator Tubes in Korean NPPS

Chung, Han Sub; Kim, Hong-Deok; Oh, Sangjun; Boo, Myung Hwan; Na, Kyung-Hwan; Yun, Eunsup; Kang, Yong-Seok; Kim, Wang-Bae; Lee, Jae Gon; Kim, Dong-Jin; Kim, Hong Pyo

doi:10.5516/net.07.2012.090

Cited by 9 publications

(2 citation statements)

References 4 publications

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“…Solving Equation 39 using Kb1,260=1. However, if crevice-like regions exist between the SG tubes and the tube sheets and support plates, or under SG sludge deposits [50][51][52], then the corrosion scenario could be quite different. In this case, acetate ion could concentrate in the crevice with a factor as high as 10 4 -presence of a crevice could result in the nickel dissolution from SG tubes.…”

Section: Resultsmentioning

confidence: 99%

Nickel-based alloy corrosion in CANDU steam generators: E-pH diagrams of the Ni-NH3-H2O and Ni-CH3COO−-H2O ternary systems

Khollari¹,

Zebardast

Asselin

2023

Preprint

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Nuclear power plant steam generator (SG) tubes contain nickel as the main alloying element and there is concern about their corrosion. We optimized models for calculating the high-temperature and high-pressure thermodynamic properties of common nuclear alloy elements and then, calculated the E-pH diagrams for nickel in different concentrations of ammonia or acetate ion between 100 to 260 ℃ at 4.7 MPa. This information is used to predict the corrosion behaviour for nickel in the secondary circuit conditions of CANDU SGs. Based on the results, nickel ammonia and nickel acetate complexes are not stable at low concentrations of ammonia or acetate ion. However, increasing the ammonia or acetate ion concentration resulted in the predominance of Ni(NH3)n2+ or Ni(Ac)n(2−n) at the expense of Ni2+ and NiO, indicating a higher risk of nickel corrosion. Calculations showed that under normal operating conditions with [NH3]tot=5×10−5 and [CH3COO−]tot=10−8 m at 260 ℃ and 4.7 MPa, nickel will be passivated as NiO, preventing the rapid degradation of nickel-based alloys. However, in the presence of a crevice that allows the acetate ion to concentrate, nickel would dissolve in the form of the Ni2+ ion, endangering safe operation of CANDU SGs.

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Section: Resultsmentioning

confidence: 99%

Nickel-based alloy corrosion in CANDU steam generators: E-pH diagrams of the Ni-NH3-H2O and Ni-CH3COO−-H2O ternary systems

Khollari¹,

Zebardast

Asselin

2023

Preprint

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“…Therefore, the integrity of the steam generator is critical to the safety and economy of the nuclear power plants [1][2]. Water chemistry and fouling are important aspects that affect the steam generator integrity of PWR nuclear power plant [3][4] .…”

Section: Introductionmentioning

confidence: 99%

Fouling and Secondary Water Chemistry of CPR1000 Steam Generators

Chen

Zhao

Peng

et al. 2022

Advances in Transdisciplinary Engineering

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Steam generators (SGs) performance degradation is one of the important concerns of nuclear power plants, which not only affects safety, but also affects the outputs in some power plants. With the large number of CPR1000 nuclear power plants put into commercial operation in China, some plants also experienced the steam pressure loss at the SGs secondary side. Compared with the known empirical laws and phenomena, the duration of the steam generator pressure loss in CRP1000 units is longer, and there are large differences between different units in different fleets. The typical trends in SGs thermal performance includes: a) an early steam pressure loss phase with a penalty of 0–1.6bar, b) a subsequent increase in steam pressure which often, but not always, results in net heat-transfer enhancement, and c) a more gradual long-term decreases with an average rate that depends on the iron transport rate and deposit characteristics. The CPR1000 units basically follow the secondary circuit control process of EDF, using NH3 and N2H4 to control the feedwater pH Value. The control target of pH value is between 9.6–9.8, and each fleet is consistent. This is a significant deviation from the different steam generator thermal performance trends. It can be seen that micro scale has a great impact on the thermal performance, which should be paid more attention, especially in the early stage of steam generator operation. Plants which have experienced a higher ratio of particulate to soluble impurity concentrations in feedwater have tended to experience smaller detrimental, or even beneficial, effects of the developing scale while others with relatively high soluble impurities have exhibited thermal performance decreases. This difference in behaviour is thought to be the result of a fundamental difference in the resulting deposit morphology. Specifically, particulate deposition is believed to enhance the population density of boiling nucleation sites on the tube while precipitating deposits tend to decrease this population density. Higher hydrazine concentrations may result in an elevated distribution of soluble iron that could decrease the population density of boiling nucleation sites. This increase in soluble species not only can form a dense scale layer that would add conductive resistance, but also lead to a decrease in boiling heat transfer coefficient. Both effects result in a performance decrease that reduces steam pressure. However, despite the promise of this line of research, no definitive guidance is yet available.

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Nickel‐based alloy corrosion in CANDU steam generators: E–pH diagrams of the Ni–NH₃–H₂O and Ni–CH₃COO⁻–H₂O ternary systems

Khollari,

Zebardast,

Asselin

2023

Materials & Corrosion

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Nuclear power plant steam generator (SG) tubes contain nickel as the main alloying element and there is concern about their corrosion. We optimized models for calculating the high‐temperature and high‐pressure thermodynamic properties of common nuclear alloy elements. Subsequently, we calculated the E–pH diagrams for nickel in different concentrations of ammonia or acetate ion at temperatures ranging from 100°C to 260°C and a pressure of 4.7 MPa. This information is used to predict the corrosion behavior of nickel in the secondary circuit conditions of Canadian Deuterium Uranium (CANDU) SGs. Increasing the ammonia or acetate ion concentration resulted in the predominance of Ni(NH3)n2+ or Ni(Ac)n(2−n) at the expense of Ni2+ and NiO, indicating a higher risk of nickel corrosion. Calculations showed that under normal operating conditions with [NH3]tot = 5 × 10−5 and [CH3COO−]tot = 10−8 m at 260°C and 4.7 MPa, nickel will be passivated as NiO, preventing the rapid degradation of nickel‐based alloys. However, in the presence of a crevice that allows the acetate ion to concentrate, nickel would dissolve in the form of the Ni2+ ion, endangering safe operation of CANDU SGs.

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A Review on the Odscc of Steam Generator Tubes in Korean NPPS

Cited by 9 publications

References 4 publications

Nickel-based alloy corrosion in CANDU steam generators: E-pH diagrams of the Ni-NH3-H2O and Ni-CH3COO−-H2O ternary systems

Nickel-based alloy corrosion in CANDU steam generators: E-pH diagrams of the Ni-NH3-H2O and Ni-CH3COO−-H2O ternary systems

Fouling and Secondary Water Chemistry of CPR1000 Steam Generators

Nickel‐based alloy corrosion in CANDU steam generators: E–pH diagrams of the Ni–NH₃–H₂O and Ni–CH₃COO⁻–H₂O ternary systems

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A Review on the Odscc of Steam Generator Tubes in Korean NPPS

Cited by 9 publications

References 4 publications

Nickel-based alloy corrosion in CANDU steam generators: E-pH diagrams of the Ni-NH3-H2O and Ni-CH3COO−-H2O ternary systems

Nickel-based alloy corrosion in CANDU steam generators: E-pH diagrams of the Ni-NH3-H2O and Ni-CH3COO−-H2O ternary systems

Fouling and Secondary Water Chemistry of CPR1000 Steam Generators

Nickel‐based alloy corrosion in CANDU steam generators: E–pH diagrams of the Ni–NH3–H2O and Ni–CH3COO−–H2O ternary systems

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Nickel‐based alloy corrosion in CANDU steam generators: E–pH diagrams of the Ni–NH₃–H₂O and Ni–CH₃COO⁻–H₂O ternary systems