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Sampling and Monitoring – The Daily Routine, Which Is Anything but Trivial or Simple

Michael Rziha

This article highlights some crucial and essential topics related to sampling and monitoring and how to obtain correct and representative samples and useful results.

Some classic mistakes; still experienced today in numerous plants; are highlighted as well.

Hints are given on how to avoid such mistakes and how to minimize the bias of samples. This article focuses on the most important basic rules for correct and representative sampling; but also draws attention to the most common mistakes being made.

PPCHEM® 2022, 24(3), 96–103

Tribute to Ken Galt

It is our sad duty to inform you that Ken Galt passed away on May 1, 2022. He had been a member of the International Advisory Board (IAB) of the PPCHEM journal since the summer of 2020. Ken Galt was an outstanding scientist in the field of power plant chemistry, contributing a wealth of valuable research findings, notably studies on many topics.

PPCHEM® 2022, 24(3), 108

HINTS FROM THE EXPERTS

Making Control Loops Smarter

For some applications in power plants; it is not a good option to wait until control loops reach the setpoint based solely on the reaction to the control deviation over time; as this may cause activation of warning signals or; in the worst case; may even trigger protection commands due to a delay in reaching the required setpoint. Some control loops are additionally susceptible to undesired oscillations. Hence; these affected control loops should be made smarter; so they behave more stably and react faster.

How this can be easily achieved is explained here with various examples.

PPCHEM® 2022, 24(3), 118–119

Foundation of the German-Swiss Association for the Properties of Water and Steam (GSAPWS) on April 1, 2022, in Potsdam, Germany

On 1 April 2022; 13 delegates met in Potsdam; Germany; for the founding meeting of the German Swiss Association for the Properties of Water and Steam. This meeting was also the first in-person meeting of the German and the Swiss National Committees since the start of the Covid-19 pandemic.

PPCHEM® 2022, 24(3), 120–121

Press Release: Last Regular Meeting of the VGB Working Group LWR-Chemistry at the NPP Emsland

Dr. Timo Stoll & Jörg Fandrich

On May 3–4; 2022; the last regular meeting of the VGB Working Group Light Water Reactor (LWR)-Chemistry took place at the nuclear power plant (NPP) Emsland; Germany. In addition to the technical experts of most of the German nuclear power plants; experts from all the Swiss nuclear power plants; the Netherlands; Spain and Belgium as well as from Framatome GmbH as consulting plant manufacturer participated.

PPCHEM® 2022, 24(3), 122–123

Conductivity Limits for Direct Water-Cooled Generators

Robert Svoboda and Wolf-Dietrich Blecken

For normal operation, a conductivity limit of ≤ 0.2 μS · cm^–1 is an indirect indicator of correct pH and restricts undue corrosion. With protective additives, e.g., NaOH for alkaline treatment, a higher limit corresponding to the objective of the treatment is appropriate.

With too high conductivity the water inside the insulating hoses of high-voltage stator windings will warm up and if it boils there is a risk of electric flashover inside the insulating hose with damaging consequences. Therefore, a short-term action limit in the order of 10 μS · cm^–1 has been set by the industry in the past.

With correct water flow, conductivity inside the insulating hoses at these values does not warm up the water significantly and there are no restrictions regarding the duration of such an event.

However, when cooling water flow is lost, the water inside the insulating hoses will warm up exponentially with time. The time until boiling has a strong (square) dependence on the rated generator voltage, as well as on the insulating hose length, and has a linear dependence on water resistivity. The spatial position of insulating hoses (hoses are mounted vertically, horizontally, or bent) is also of importance. In addition, the stationary cooling water inside the stator bars, as well as the entire stator winding, is subjected to critical temperatures, especially at high load conditions. Therefore, appropriate action must be taken prior to reaching the water boiling level. To avoid a costly stator winding breakdown, the cooling water flow must be restored at once. Otherwise, the generator has to be shut down completely as soon as possible.

PPCHEM^® 2022, 24(2), 52–63

Avoidance of Common Mistakes during Failure Analyses and Misinterpretation of Lab Results – Part 2: Lab Analyses / Sample Handling, Preparation, and Analytical Procedures

Frank Udo Leidich

For a proper failure analysis or root cause analysis (RCA), a great deal of data and evidence-based information is needed. Within this context, various types of samples from different locations need to be taken for chemical and/or metallurgical examination. In addition to proper and correct sampling without alteration of the composition or contamination of the samples, which is described in the first article of this short series [1], it is of utmost importance to use the right analytical methods and execute sample preparation carefully. This includes being aware of the basic principles of the methods applied and of course knowing their limits. This article discusses the analytical part of an RCA and is the second part in a short series of ongoing articles.

PPCHEM^® 2022, 24(2), 70–75

HINTS FROM THE EXPERTS

Considerations for the Control of the Dosing of Trisodium Phosphate (Na₃PO₄) in Boiler Water

In the recent past, various organizations have been trying to establish a more or less full automatization of the dosing control for the phosphate boiler water treatment (typically called PT), similar to the well-established and well-functioning automatic dosing control of ammonia. Although this may sound easy, as nowadays very reliable instruments and sampling systems are available, it is relatively difficult to implement, especially for PT, as the entire phosphate chemistry is very complex compared to that of ammonia. Therefore a safe and reliable automatic control of PT involves a lot of traps and risks which must be considered. The most common and challenging issues in this respect are described here. Although this list may not be complete, it could be used to reconsider the idea of fully automated control of phosphate dosing.

PPCHEM^® 2022, 24(2), 76–81