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Title: An Investigation of the Mechanism of IGA/SCC of Alloy 600 in Corrosion Accelerating Heated Crevice Environments - Topical Report Phase I 8/18/1999 - 8/31/2000

Abstract

The crevice formed by the tube/tube support plate (T/TSP) intersection in a pressurized water reactor (PWR) steam generator is a concentration site for nonvolatile impurities (referred to as hideout) in the steam generator water. The restricted mass transport in the small crevice volume prevents the species, which concentrate by a thermal/hydraulic mechanism during the generation of steam, from quickly dispersing into the bulk water. The presence of a porous scale corrosion product on the surface of the tube and deposits of corrosion products in the crevice further restrict mass transport. The concentrated solutions and deposits in T/TSP crevices have been correlated with several forms of corrosion on the OD of steam generator tubes including intergranular attack/stress corrosion cracking (IGA/SCC), pitting, and wastage. The rate and type of corrosion are dependent on pH, specific anions, and the electrochemical potential. Careful water chemistry control and other remedial measures have essentially stopped all forms of secondary side corrosion except IGA/SCC. Crevice chemistries in an operating steam generator cannot be measured directly because of their inaccessibility. In practice, computer codes (MULTEQ, Molar Ratio Index, etc.) based upon hypothesized chemical reactions and thermal hydraulic mechanisms are used to predict crevice chemistry. The Rockwell program providesmore » an experimental base to benchmark crevice chemistry models and to benchmark crevice chemistry control measures designed to mitigate IGA/SCC. The objective of this program is to develop an understanding of the corrosion accelerating mechanisms, particularly IGA/SCC, in steam generator crevices. The important variables will be identified, including the relationship between bulk water chemistry and corrosion accelerating chemistries in a crevice. An important result will be the identification of water chemistry control measures needed to mitigate secondary side IGA/SCC in steam generator tubes. The approach uses an instrumented heated crevice, which is a replica of a PWR steam generator T/TSP crevice. While the system is operating at simulated steam generator thermal conditions, measurements can be made of the chemical, electrochemical, and thermal conditions in the crevice. Damage to the tube due to IGA/SCC and other corrosion processes will be monitored using electrochemical noise.« less

Authors:
Publication Date:
Research Org.:
Rockwell Science Center LLC, Thousand Oaks, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
769257
DOE Contract Number:  
FG03-99SF21921
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Nov 2000
Country of Publication:
United States
Language:
English
Subject:
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; ALLOYS; CHEMICAL REACTIONS; CHEMISTRY; COMPUTER CODES; CORROSION; CORROSION PRODUCTS; PWR TYPE REACTORS; STEAM GENERATORS; WATER CHEMISTRY

Citation Formats

Dr. Jesse Lumsden. An Investigation of the Mechanism of IGA/SCC of Alloy 600 in Corrosion Accelerating Heated Crevice Environments - Topical Report Phase I 8/18/1999 - 8/31/2000. United States: N. p., 2000. Web. doi:10.2172/769257.
Dr. Jesse Lumsden. An Investigation of the Mechanism of IGA/SCC of Alloy 600 in Corrosion Accelerating Heated Crevice Environments - Topical Report Phase I 8/18/1999 - 8/31/2000. United States. doi:10.2172/769257.
Dr. Jesse Lumsden. Wed . "An Investigation of the Mechanism of IGA/SCC of Alloy 600 in Corrosion Accelerating Heated Crevice Environments - Topical Report Phase I 8/18/1999 - 8/31/2000". United States. doi:10.2172/769257. https://www.osti.gov/servlets/purl/769257.
@article{osti_769257,
title = {An Investigation of the Mechanism of IGA/SCC of Alloy 600 in Corrosion Accelerating Heated Crevice Environments - Topical Report Phase I 8/18/1999 - 8/31/2000},
author = {Dr. Jesse Lumsden},
abstractNote = {The crevice formed by the tube/tube support plate (T/TSP) intersection in a pressurized water reactor (PWR) steam generator is a concentration site for nonvolatile impurities (referred to as hideout) in the steam generator water. The restricted mass transport in the small crevice volume prevents the species, which concentrate by a thermal/hydraulic mechanism during the generation of steam, from quickly dispersing into the bulk water. The presence of a porous scale corrosion product on the surface of the tube and deposits of corrosion products in the crevice further restrict mass transport. The concentrated solutions and deposits in T/TSP crevices have been correlated with several forms of corrosion on the OD of steam generator tubes including intergranular attack/stress corrosion cracking (IGA/SCC), pitting, and wastage. The rate and type of corrosion are dependent on pH, specific anions, and the electrochemical potential. Careful water chemistry control and other remedial measures have essentially stopped all forms of secondary side corrosion except IGA/SCC. Crevice chemistries in an operating steam generator cannot be measured directly because of their inaccessibility. In practice, computer codes (MULTEQ, Molar Ratio Index, etc.) based upon hypothesized chemical reactions and thermal hydraulic mechanisms are used to predict crevice chemistry. The Rockwell program provides an experimental base to benchmark crevice chemistry models and to benchmark crevice chemistry control measures designed to mitigate IGA/SCC. The objective of this program is to develop an understanding of the corrosion accelerating mechanisms, particularly IGA/SCC, in steam generator crevices. The important variables will be identified, including the relationship between bulk water chemistry and corrosion accelerating chemistries in a crevice. An important result will be the identification of water chemistry control measures needed to mitigate secondary side IGA/SCC in steam generator tubes. The approach uses an instrumented heated crevice, which is a replica of a PWR steam generator T/TSP crevice. While the system is operating at simulated steam generator thermal conditions, measurements can be made of the chemical, electrochemical, and thermal conditions in the crevice. Damage to the tube due to IGA/SCC and other corrosion processes will be monitored using electrochemical noise.},
doi = {10.2172/769257},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2000},
month = {11}
}