Insights into the formation mechanism of hard sludge on the secondary side of PWR steam generators

Beal, K.; Million-Picallion, L.; Delaunay, Sophie; Berger, G.; Lefèvre, Grégory

doi:10.1016/j.nme.2022.101197

Cited by 4 publications

(4 citation statements)

References 11 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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“…Turner et al [9,10] reported that Zn and Ca could affect deposit consolidation by forming new phases such as willemite (Zn 2 SiO 4 ) and calcium sulfate. Beal et al [15] also showed that Si combined with Al or Al alone could form chemical compounds such as kaolinite (Al 2 Si 2 O 5 (OH) 4 ) or boehmite (AlO(OH)) (an Al oxide), and that these compounds have an important role in the promotion of sludge formation and in the consolidation of hard sludge. Second, metallic impurities like Cu and Pb particles concentrate within the micropores, where they can electrically contact the surface of the SG tube and thus affect the galvanic acceleration of an SG tube because Cu and Pb particles act as cathodes of a galvanic couple [11].…”

Section: Morphologies Of Depositsmentioning

confidence: 99%

“…These efforts have been largely successful in reducing Fe concentrations in feedwater by decreasing the corrosion rate. In particular, many investigations have focused on the effects of water chemistry parameters on the FAC of carbon steel and other structural materials [4,15].…”

Section: Introductionmentioning

confidence: 99%

Effects of Advanced Amines on Magnetite Deposition of Steam Generator Tubes in Secondary System

Lee

Hur

et al. 2021

Coatings

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Ethanolamine (ETA) is widely used to control the pH value in the secondary water of pressurized water reactors. However, it is necessary to consider other advanced amines which can replace ETA due to its serious human hazards and environmental treatment problems. The purpose of this study is to contemplate the effects of three advanced amines (ETA, 3-methoxypropylamine (MPA), and dimethylamine (DMA)) on the magnetite deposition behavior of a thermally treated (TT) Alloy 690 tubes by using a steam generator (SG) tube fouling loop in simulated secondary water. All particles were identified as a magnetite and were polyhedral or spherical in shape. When using ETA, MPA, and DMA, the average porosity of the deposits was about 34.7%, 33.0%, and 24.6%, respectively. The amount of deposits was largest when ETA was added, and it decreased by 41% when adding MPA and 55% when adding DMA. The mechanism of magnetite deposition was discussed in terms of zeta potentials of both the magnetite particles and the Alloy 690TT surface and magnetite solubility depending on the amines. To compare the potential for replacing ETA with other advanced amines, the various factors such as SG integrity, human hazards, and environmental treatment problems were discussed.

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“…On the other hand, corrosion products released due to the flow-accelerated corrosion of iron-based piping materials are transported into the SGs and deposited on the surfaces of the SG materials including tubes, TSPs, and tubesheets. The SG deposits are mainly composed of magnetite (Fe 3 O 4 ) that contains numerous pores [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. As a result, chemical impurities are easily concentrated within the deposits.…”

Section: Introductionmentioning

confidence: 99%

On the Use of NaOH Solution to Simulate the Crevice Conditions of a Nuclear Steam Generator

Hur

Song²,

Han

et al. 2022

Materials

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The corrosion behavior and integrity of steam generator (SG) tube materials have frequently been tested in solutions containing sodium hydroxide (NaOH), assuming that NaOH is a typical contaminant concentrated in the crevices of SGs in a pressurized water reactor. The purpose of this study was to investigate the adequacy of using concentrated NaOH solutions to simulate the crevice environments of SGs. The dissolution behavior of magnetite deposit flakes formed in an operating SG was tested in a 0.4 wt.% NaOH solution at 300 °C, and the thermodynamic stability of magnetite was investigated using the potential-pH diagram for an iron–water system. The magnetite deposits were rapidly dissolved in the test solution, which was supported by the fact that magnetite is thermodynamically unstable under the test condition to dissolve to dihypoferrite ions (HFeO2−). These results indicate that research data obtained from concentrated NaOH solutions are not appropriate to apply to the crevice environments of SGs.

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Insights into the formation mechanism of hard sludge on the secondary side of PWR steam generators

Cited by 4 publications

References 11 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

Effects of Advanced Amines on Magnetite Deposition of Steam Generator Tubes in Secondary System

On the Use of NaOH Solution to Simulate the Crevice Conditions of a Nuclear Steam Generator

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