Optimisation of the water chemistry regarding stability of the oxide film on alloy 690 during simulated hot functional testing of a pressurised water reactor

I. Betova, M. Bojinov, V. Karastoyanov, Petri Kinnunen, Timo Saario

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

Abstract

In the present paper, an attempt is made to quantify the effect of water chemistry in simulated HFT conditions on the electrical and electrochemical properties, and thus stability and corrosion resistance, of the passive film formed on a PWR steam generator material, namely, Alloy 690. For the purpose, a quantitative procedure to interpret simultaneously electrochemical impedance and surface analytical results is used to obtain first-hand estimates of the interfacial rate constants of oxidation of individual alloy constituents (Ni, Cr and Fe), the diffusion coefficient of oxygen vacancies, as well as field strength in the growing oxide. The main conclusion that can be drawn from both experimental and calculational results is that increasing LiOH concentration in the simulated HFT water leads to higher dissolution rates, higher metal oxidation and transport rates through the oxide, or in other words, the formed oxide is found to be the more defective, the higher the concentration of Li in the electrolyte is. On the other hand, boron added as H3BO3 was found to have a beneficial effect that counter-acts the accelerating influence of Li. On the basis of our experiments and their interpretation, a HFT water chemistry with low to intermediate Li contents and boron addition seems to produce films that exhibit better electrochemical stability and thus corrosion resistance.
Original languageEnglish
Title of host publicationProceedings
Subtitle of host publicationNuclear Plant Chemistry Conference, NPC 2012
Place of PublicationParis, France
Publication statusPublished - 2012
MoE publication typeA4 Article in a conference publication
EventNuclear Plant Chemistry Conference, NPC 2012 - Paris, France
Duration: 23 Sep 201227 Sep 2012

Conference

ConferenceNuclear Plant Chemistry Conference, NPC 2012
Abbreviated titleNPC 2012
CountryFrance
CityParis
Period23/09/1227/09/12

Fingerprint

Pressurized water reactors
Oxides
Oxide films
Boron
Corrosion resistance
Water
Testing
Oxidation
Steam generators
Oxygen vacancies
Electrochemical properties
Electrolytes
Rate constants
Dissolution
Electric properties
Metals
Experiments

Keywords

  • water chemistry
  • pressurised water reactors
  • hot conditioning

Cite this

Betova, I., Bojinov, M., Karastoyanov, V., Kinnunen, P., & Saario, T. (2012). Optimisation of the water chemistry regarding stability of the oxide film on alloy 690 during simulated hot functional testing of a pressurised water reactor. In Proceedings: Nuclear Plant Chemistry Conference, NPC 2012 Paris, France.
Betova, I. ; Bojinov, M. ; Karastoyanov, V. ; Kinnunen, Petri ; Saario, Timo. / Optimisation of the water chemistry regarding stability of the oxide film on alloy 690 during simulated hot functional testing of a pressurised water reactor. Proceedings: Nuclear Plant Chemistry Conference, NPC 2012. Paris, France, 2012.
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abstract = "In the present paper, an attempt is made to quantify the effect of water chemistry in simulated HFT conditions on the electrical and electrochemical properties, and thus stability and corrosion resistance, of the passive film formed on a PWR steam generator material, namely, Alloy 690. For the purpose, a quantitative procedure to interpret simultaneously electrochemical impedance and surface analytical results is used to obtain first-hand estimates of the interfacial rate constants of oxidation of individual alloy constituents (Ni, Cr and Fe), the diffusion coefficient of oxygen vacancies, as well as field strength in the growing oxide. The main conclusion that can be drawn from both experimental and calculational results is that increasing LiOH concentration in the simulated HFT water leads to higher dissolution rates, higher metal oxidation and transport rates through the oxide, or in other words, the formed oxide is found to be the more defective, the higher the concentration of Li in the electrolyte is. On the other hand, boron added as H3BO3 was found to have a beneficial effect that counter-acts the accelerating influence of Li. On the basis of our experiments and their interpretation, a HFT water chemistry with low to intermediate Li contents and boron addition seems to produce films that exhibit better electrochemical stability and thus corrosion resistance.",
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Betova, I, Bojinov, M, Karastoyanov, V, Kinnunen, P & Saario, T 2012, Optimisation of the water chemistry regarding stability of the oxide film on alloy 690 during simulated hot functional testing of a pressurised water reactor. in Proceedings: Nuclear Plant Chemistry Conference, NPC 2012. Paris, France, Nuclear Plant Chemistry Conference, NPC 2012, Paris, France, 23/09/12.

Optimisation of the water chemistry regarding stability of the oxide film on alloy 690 during simulated hot functional testing of a pressurised water reactor. / Betova, I.; Bojinov, M.; Karastoyanov, V.; Kinnunen, Petri; Saario, Timo.

Proceedings: Nuclear Plant Chemistry Conference, NPC 2012. Paris, France, 2012.

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

TY - GEN

T1 - Optimisation of the water chemistry regarding stability of the oxide film on alloy 690 during simulated hot functional testing of a pressurised water reactor

AU - Betova, I.

AU - Bojinov, M.

AU - Karastoyanov, V.

AU - Kinnunen, Petri

AU - Saario, Timo

N1 - Project code: 73813

PY - 2012

Y1 - 2012

N2 - In the present paper, an attempt is made to quantify the effect of water chemistry in simulated HFT conditions on the electrical and electrochemical properties, and thus stability and corrosion resistance, of the passive film formed on a PWR steam generator material, namely, Alloy 690. For the purpose, a quantitative procedure to interpret simultaneously electrochemical impedance and surface analytical results is used to obtain first-hand estimates of the interfacial rate constants of oxidation of individual alloy constituents (Ni, Cr and Fe), the diffusion coefficient of oxygen vacancies, as well as field strength in the growing oxide. The main conclusion that can be drawn from both experimental and calculational results is that increasing LiOH concentration in the simulated HFT water leads to higher dissolution rates, higher metal oxidation and transport rates through the oxide, or in other words, the formed oxide is found to be the more defective, the higher the concentration of Li in the electrolyte is. On the other hand, boron added as H3BO3 was found to have a beneficial effect that counter-acts the accelerating influence of Li. On the basis of our experiments and their interpretation, a HFT water chemistry with low to intermediate Li contents and boron addition seems to produce films that exhibit better electrochemical stability and thus corrosion resistance.

AB - In the present paper, an attempt is made to quantify the effect of water chemistry in simulated HFT conditions on the electrical and electrochemical properties, and thus stability and corrosion resistance, of the passive film formed on a PWR steam generator material, namely, Alloy 690. For the purpose, a quantitative procedure to interpret simultaneously electrochemical impedance and surface analytical results is used to obtain first-hand estimates of the interfacial rate constants of oxidation of individual alloy constituents (Ni, Cr and Fe), the diffusion coefficient of oxygen vacancies, as well as field strength in the growing oxide. The main conclusion that can be drawn from both experimental and calculational results is that increasing LiOH concentration in the simulated HFT water leads to higher dissolution rates, higher metal oxidation and transport rates through the oxide, or in other words, the formed oxide is found to be the more defective, the higher the concentration of Li in the electrolyte is. On the other hand, boron added as H3BO3 was found to have a beneficial effect that counter-acts the accelerating influence of Li. On the basis of our experiments and their interpretation, a HFT water chemistry with low to intermediate Li contents and boron addition seems to produce films that exhibit better electrochemical stability and thus corrosion resistance.

KW - water chemistry

KW - pressurised water reactors

KW - hot conditioning

M3 - Conference article in proceedings

SN - 978-2-9516-1952-4

BT - Proceedings

CY - Paris, France

ER -

Betova I, Bojinov M, Karastoyanov V, Kinnunen P, Saario T. Optimisation of the water chemistry regarding stability of the oxide film on alloy 690 during simulated hot functional testing of a pressurised water reactor. In Proceedings: Nuclear Plant Chemistry Conference, NPC 2012. Paris, France. 2012