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Single phase and two phase erosion corrosion in broilers of gas-cooled reactors

Abstract

Erosion-corrosion is a phenomenon causing metal wastage in a variety of locations in water and water-steam circuits throughout the power generation industry. Erosion-corrosion can occur in a number of regions of the once-through boiler designs used in the later Magnox and AGR type of gas cooled nuclear reactor. This paper will consider two cases of erosion-corrosion damage (single and two phase) in once through boilers of gas cooled reactors and will describe the solutions that have been developed. The single phase problem is associated with erosion-corrosion damage of mild steel downstream of a boiler inlet flow control orifice. With metal loss rates of up to 1 mm/year at 150 deg. C and pH in the range 9.0-9.4 it was found that 5 {mu}g/kg oxygen was sufficient to reduce erosion-corrosion rates to less than 0.02 mm/year. A combined oxygen-ammonia-hydrazine feedwater regime was developed and validated to eliminate oxygen carryover and hence give protection from stress corrosion in the austenitic section of the AGR once through boiler whilst still providing erosion-corrosion control. Two phase erosion-corrosion tube failures have occurred in the evaporator of the mild steel once through boilers of the later Magnox reactors operating at pressures in the range 35-40 bar.  More>>
Authors:
Harrison, G S; Fountain, M J [1] 
  1. Operational Engineering Division (Northern Area), Central Electricity Generating Board, Manchester (United Kingdom)
Publication Date:
Jul 01, 1988
Product Type:
Conference
Report Number:
IWGGCR-15
Reference Number:
EDB-01:001762
Resource Relation:
Conference: Specialists' meeting on technology of steam generators for gas-cooled reactors, Winterthur (Switzerland), 9-12 Mar 1987; Other Information: 3 refs, 6 figs, 2 tabs; PBD: 1988; Related Information: In: Technology of steam generators for gas-cooled reactors. Proceedings of a specialists' meeting, 236 pages.
Subject:
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; AGR TYPE REACTORS; AUSTENITIC STEELS; BOILERS; FAILURES; MAGNOX TYPE REACTORS; PRESSURE DEPENDENCE; STEAM GENERATION; STRESS CORROSION; TEMPERATURE DEPENDENCE
OSTI ID:
20113032
Research Organizations:
International Atomic Energy Agency, International Working Group on Gas-Cooled Reactors, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
TRN: XA0056049057150
Availability:
Available from INIS in electronic form
Submitting Site:
INIS
Size:
page(s) 156-163
Announcement Date:

Citation Formats

Harrison, G S, and Fountain, M J. Single phase and two phase erosion corrosion in broilers of gas-cooled reactors. IAEA: N. p., 1988. Web.
Harrison, G S, & Fountain, M J. Single phase and two phase erosion corrosion in broilers of gas-cooled reactors. IAEA.
Harrison, G S, and Fountain, M J. 1988. "Single phase and two phase erosion corrosion in broilers of gas-cooled reactors." IAEA.
@misc{etde_20113032,
title = {Single phase and two phase erosion corrosion in broilers of gas-cooled reactors}
author = {Harrison, G S, and Fountain, M J}
abstractNote = {Erosion-corrosion is a phenomenon causing metal wastage in a variety of locations in water and water-steam circuits throughout the power generation industry. Erosion-corrosion can occur in a number of regions of the once-through boiler designs used in the later Magnox and AGR type of gas cooled nuclear reactor. This paper will consider two cases of erosion-corrosion damage (single and two phase) in once through boilers of gas cooled reactors and will describe the solutions that have been developed. The single phase problem is associated with erosion-corrosion damage of mild steel downstream of a boiler inlet flow control orifice. With metal loss rates of up to 1 mm/year at 150 deg. C and pH in the range 9.0-9.4 it was found that 5 {mu}g/kg oxygen was sufficient to reduce erosion-corrosion rates to less than 0.02 mm/year. A combined oxygen-ammonia-hydrazine feedwater regime was developed and validated to eliminate oxygen carryover and hence give protection from stress corrosion in the austenitic section of the AGR once through boiler whilst still providing erosion-corrosion control. Two phase erosion-corrosion tube failures have occurred in the evaporator of the mild steel once through boilers of the later Magnox reactors operating at pressures in the range 35-40 bar. Rig studies have shown that amines dosed in the feedwater can provide a significant reduction in metal loss rates and a tube lifetime assessment technique has been developed to predict potential tube failure profiles in a fully operational boiler. The solutions identified for both problems have been successfully implemented and the experience obtained following implementation including any problems or other benefits arising from the introduction of the new regimes will be presented. Methods for monitoring and evaluating the efficiency of the solutions have been developed and the results from these exercises will also be discussed. Consideration will also be given to the similarities in the metal loss mechanisms and possible methods of solution that both problems exhibit. Finally the adaption of the new regimes described in the paper to problems in other areas of the power generation industry will be reviewed. (author)}
place = {IAEA}
year = {1988}
month = {Jul}
}