Influence of corrosion processes on the head loss across ECCS sump strainers
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H. Kryk
Abstract
Corrosion investigations were carried out using hot-dip galvanized steel samples in order to identify the corrosion mechanisms as well as the nature of corrosion products formed. Corrosion of grating treads may exacerbate ECCS strainer clogging problems during LOCA events in LWR. For the related experiments, tailored bench-scale facilities have been constructed. The results of batch experiments as well as of long-time corrosion investigations in the Korr VA test facility suggest that there is a multi-stage corrosion process. The first stage comprises the dissolution of the Zn layer in the coolant forming Zn2+ ions, which can generate crystalline zinc borate in boric acid solutions, if the ion concentration exceeds the saturation concentration. The base material (steel) is cathodically protected as long as the zinc layer is present. During the second stage, the base material dissolves forming insoluble corrosion particles, which can subsequently lead to acceleration of the strainer clogging. The main influences on corrosion were identified as impact of the water onto the corroding surface, water chemistry and Zn surface/coolant volume ratio.
Kurzfassung
Zur Aufklärung von Korrosionsprozessen und deren Auswirkungen auf die Verstopfung von Sumpfansaugsieben bei Kühlmittelverluststörfällen wurden Korrosionsuntersuchungen in speziellen Laboranlagen unter Nutzung von feuerverzinkten Stahlproben durchgeführt. Die Ergebnisse der Batch- sowie der Langzeit-Korrosionsexperimente lassen auf einen mehrstufigen Korrosionsmechanismus schließen. Zunächst erfolgt eine Auflösung der Zinkschicht in der Borsäure-Lösung. Die dabei entstehenden Zn2+-Ionen können, bei Überschreiten der Sättigungskonzentration, zur Kristallisation von Zinkborat führen. Während der zweiten Stufe erfolgt die Auflösung des Basismaterials, welches in weiterer Folge zu unlöslichen Korrosionspartikeln (Rost) reagiert. Diese lagern sich an den mit Isoliermaterial-Fasern belegten Sumpfsieben ab und führen so zu einem weiteren Differenzdruckaufbau. Haupteinflussfaktoren des Gesamtprozesses sind die Aufprallkraft des Leckstrahls auf die Materialoberfläche, die Wasserchemie sowie das Verhältnis der Korrosions-Oberfläche zum Kühlmittel-Volumen.
References
1 Chen, D.; Howe, K. J.; Dallman, J.; Letellier, B. C.; Klasky, M.; Leavitt, J.; Jain, B.: Experimental analysis of the aqueous chemical environment following a loss-of-coolant accident, Nucl. Eng. Des.237 (2007) 2126Search in Google Scholar
2 Knowledge Base for Emergency, Core Cooling System Recirculation Reliability, NEA/CSNI/R (95) 11, February 1996Search in Google Scholar
3 Knowledge Base for the Effect of Debris on Pressurized Water Reactor Emergency Core Cooling Sump Performance, NUREG/CR-6808; LA-UR-03-0880, February 2003Search in Google Scholar
4 Knowledge Base for Strainer Clogging – Modifications Performed in Different Countries Since 1992, NEA/CSNI/R (2002) 6Search in Google Scholar
5 Debris impact on Emergency coolant recirculation, Workshop Albuquerque, NM, USA February 2004, Proceedings OECD 2004 NEA No. 5468Search in Google Scholar
6 Grahn, A.; Krepper, E.; Alt, S.; Kästner, W.: Implementation of a strainer model for calculating the pressure drop across beds of compressible, fibrous materials, Nucl. Eng. Des.238 (2008) 2546Search in Google Scholar
7 Chen, D.; Howe, K. J.; Dallman, J.; Letellier, B. C.: Corrosion of aluminium in the aqueous chemical environment of a loss-of-coolant accident at a nuclear power plant, Corros. Sci., 50 (2008) 1046Search in Google Scholar
8 Integrated Chemical Effects Test Project: Consolidated Data Report, NUREG/CR-6914, LA-UR-06-3673, December 2006Search in Google Scholar
9 Piippo, J.; Laitinen, T.; Sirkiä, P.: Corrosion behaviour of zinc and aluminium in simulated nuclear accident environments, STUK-YTO-TR 123, Helsinki 1997Search in Google Scholar
10 Small-Scale Experiments: Effects of Chemical Reactions on Debris-Bed Head Loss, NUREG/CR-6868, LA-UR-03-6415, March 2005Search in Google Scholar
11 Final Report – Evaluation of Chemical Effects Phenomena in Post-LOCA Coolant, NUREG/CR-6988, March 2009Search in Google Scholar
12 Waas, U.: Untersuchungen zu DWR: Freisetzung des Isoliermaterials, Transport zum Sumpf, Verhalten im Sumpf, Siebbelegung und Langzeiteffekte. Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland, KTG-Fachtagung, Rossendorf, April 3.-4., 2006Search in Google Scholar
13 Ganzmann, I.; Waas, U.: Experiments on the integral test facility “Erlanger Wanne”, KERNTECHNIK76 (1) (2011) 15–19Search in Google Scholar
14 Zhang, X. G.: Corrosion and Electrochemistry of Zinc, Plenum Press, New York199610.1007/978-1-4757-9877-7Search in Google Scholar
© 2011, Carl Hanser Verlag, München
Articles in the same Issue
- Contents/Inhalt
- Contents
- Summaries/Kurzfassungen
- Summaries
- Editorial
- State of the art of controlling loss-of-coolant accidents with release of insulation material
- Technical Contributions/Fachbeiträge
- LOCAs with release of insulation material: generic aspects and international solutions
- Experiments on the integral test facility “Erlanger Wanne”
- Generic experiments at the sump model “Zittauer Strömungswanne” (ZSW) for the behaviour of mineral wool in the sump and the reactor core
- CFD analyses of fibre transport and fibre deposition at plunging jet conditions
- CFD simulation of fibre material transport in a PWR core under loss of coolant conditions
- Influence of corrosion processes on the head loss across ECCS sump strainers
- Analyses and estimation of insulation material release in E.ON-PWR under loss of coolant conditions
- Analyses of loss-of-coolant accidents involving release of insulation material under consideration of the measures taken for PWR from expert's point of view
- Evidence of having control over loss-of-coolant accidents with release of insulation material under consideration of actions taken in German BWR
Articles in the same Issue
- Contents/Inhalt
- Contents
- Summaries/Kurzfassungen
- Summaries
- Editorial
- State of the art of controlling loss-of-coolant accidents with release of insulation material
- Technical Contributions/Fachbeiträge
- LOCAs with release of insulation material: generic aspects and international solutions
- Experiments on the integral test facility “Erlanger Wanne”
- Generic experiments at the sump model “Zittauer Strömungswanne” (ZSW) for the behaviour of mineral wool in the sump and the reactor core
- CFD analyses of fibre transport and fibre deposition at plunging jet conditions
- CFD simulation of fibre material transport in a PWR core under loss of coolant conditions
- Influence of corrosion processes on the head loss across ECCS sump strainers
- Analyses and estimation of insulation material release in E.ON-PWR under loss of coolant conditions
- Analyses of loss-of-coolant accidents involving release of insulation material under consideration of the measures taken for PWR from expert's point of view
- Evidence of having control over loss-of-coolant accidents with release of insulation material under consideration of actions taken in German BWR
