Contents Issue 2 (2001)

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Tomáš Prošek and Pavel Novák

Irregular Corrosion of Austenitic Stainless Steel under Heat Transfer Conditions

Influence of heat flux and surface temperature on initia-tion and propagation of corrosion and corrosion cracking was studied on austenitic stainless steel. The influence of increasing surface temperature of the heat-exchanging surface is always negative (easier initiation and greater propagation rate of localized corrosion). The influence of heat flux is more complicated. In case of crevice corro-sion and stress corrosion cracking, application of positive heat flux leads to increased extent of attack. Initiation of pitting corrosion is suppressed but depth of attack slightly increases. Heat flux from metal to solution at constant surface temperature promotes the initiation of intergranular attack, but in contrary decreases its propa-gation rate. The influence of heat flux (without boiling) is, except for crevice corrosion, less significant than that of surface temperature, but still not negligible.

PowerPlant Chemistry 2001, 3 (2)

Herbert Prenzel

Development of Ion Chromatography in Power Plant Chemistry

Ion chromatography (IC) has been introduced to power plant laboratory to analyze traces of anions. The changing task fields of IC applications and the orientation toward new tasks of power plant chemistry that have to be tackled and developed are presented. The focus is on DeNOx and DeSOx processes. The IC technique was successfully applied for identifica-tion of sulfur-nitrogen compounds in flue gas desulfuriza-tion process and resulted in a quick implementation of a simple process layout for a two-stage wastewater treat-ment system with gyp-sum recirculation.

PowerPlant Chemistry 2001, 3 (2)

Klaus Knecht, Richard Stark, and Karl Habeck

In-Core Sipping at BWR Plants in Only 16 Hours

Introduction of a new FRAMATOME ANP's fuel sipping system which was first manufactured for Germany's twin-unit plant Gundremmingen. It permits all fuel assemblies in the core to be sipped during a refueling outage. It is a direct follow-on from the sipping hood for eight fuel assemblies already supplied by to various nuclear plants. Depending on the size of the core, the new sipping sys-tem is designed for 16 fuel assemblies to be tested simultaneously. The new technique that uses this hood for 16 fuel assemblies, in which the gases obtained from water samples are scanned on-line for 85Kr and 133Xe provides immediate information on fuel integrity.

PowerPlant Chemistry 2001, 3 (2)

Jayappa Manjanna, Gopala Venkateswaran, Bailure Sheena Sherigara, and Peruduru Vasudeva Nayak

Reductive Dissolution of Chromium Substituted Hematites in V(II)-EDTA formulation

The dissolution characteristics of synthetic Cr-substituted hematites (CSH) Fe2-xCrxO3 (x= 0.1, 0.2, 0.3, and 0.4) in V(II)-EDTA formulation at 353 ± 5 K are reported. The dissolution follows a two-stage process: a first stage in which a fast initial dissolution occurs in the first ten min-utes of dissolution followed by a slow second stage dis-solution extending to a few hours. A preferential dissolu-tion of iron over chromium occurs in all the CSHs employed. The effect of oxidative pretreatment prior to the reductive dissolution, using alkaline permanganate, nitric permanganate, and permanganic acid reagents, is determined and compared. Pretreatment improves the dissolution and HMnO4 is found to be relatively more effective.

PowerPlant Chemistry 2001, 3 (2)

Joachim Wasel-Nielen

The Treatment of Recirculated Cooling Water with Ozone

Ozonation of cooling circuits has been increasingly car-ried out since the late 1970s and is now successfully used in eight systems. Continuous ozonation of cooling water circuits is a more effective microbiocidal treatment than chlorination or addition of other biocides. By using ozone in combination with careful water conditioning, it has been possible to achieve considerable cost savings. Corrosion rates were significantly reduced as a result of the more effective biocidal action, reliable prevention of biological fouling and non-aggressive nature of the treatment. However, without additional dosage of corro-sion inhibitors, corrosion rates < 0.1 mm/year were not achieved under our conditions.

PowerPlant Chemistry 2001, 3 (2)

Hans D. Pflug, Eric V. Maughan, Georg Müller, and Gottfried Betz

Central Control Unit for On-Line Power Plant Chemistry, Part 1

A concept of a comprehensive monitoring and control system for power plant chemistry has been developed which has the following characteristics: data acquisition and processing by statistical algorithms, correction of measured values to reference temperature and to real time (sodium), analytical monitoring of power plant pro-cesses, carrying out supporting physical-chemical cal-culations, trouble identification by diagnostic expert sys-tems, dosage control of chemical agents, etc.
The application of the new Central Control Units (CCU) may gradually be extended to other areas of power plant chemistry. This paper will be continued with PART 2 which describes the functions of the CCU with respect to programmed control of cycle chemistry.

PowerPlant Chemistry 2001, 3 (2)