Experimental Investigation on Denting in PWR Steam Generators: Causes and Corrective Actions

[+] Author and Article Information
F. Nordmann

Framatome, Groupe Chimie et Corrosion, Paris La Défense, France

G. Pinard-Legry

CEA, Section de’Etude de la Corrosion Aqueuse, Centre de Fontenay-aux-Roses, France

J. Daret

CEA, Section d’Etude de la Corrosion Aqueuse, Centre de La Hague, France

J. P. Brunet

CEA, Service d’Etude et de Dévelopment de la Technologie des Reácteurs à Eau, Centre de Cadarache, France

J. Eng. Power 105(4), 755-762 (Oct 01, 1983) (8 pages) doi:10.1115/1.3227478 History: Received July 27, 1982; Online September 28, 2009


Denting studies have been undertaken in order to assess the influence of the most important parameters which could initiate corrosion of the carbon steel occurring in the tube-tube support plate crevices of some PWR steam generators. Tests have been carried out in model boilers where feedwater was polluted with sea or river water. Specific effects of chloride or sulfate and influence of oxygen content, magnetite addition and pH value were investigated. In magnetite prepacked crevices, denting is obtained within 1000 hrs for seawater pollution of 0.3 ppm chloride at the blowdown. In neutral chloride or in river water, denting is observed only with oxygen addition. Denting prevention is effective in the case of an on-line addition of phosphate, boric acid, or calcium hydroxide. For denting stopping, boric acid or calcium hydroxide is efficient even with a high seawater pollution. Soaks cannot stop denting if they are not followed by an on-line treatment (boric acid, calcium hydroxide). With quadrifoil holes, denting doesn’t occur. In very severe test conditions, 13 percent Cr steel can be corroded, but the corrosion rate is low and oxide morphology is different from that growing on carbon steel.

Copyright © 1983 by ASME
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