Electrochemical corrosion potential device and method

Abstract

The invention provides at least two electrochemical sensors positioned in a nuclear reactor or in a system adjacent to the nuclear reactor, wherein at least one of the at least two electrochemical sensors has a heated zirconium electrode, and the at least two electrochemical sensors produce voltages proportional to an electrochemical corrosion potential for a surface that each of the at least two electrochemical sensors are installed upon. The invention also provides an arrangement configured to accept the voltages produced by the at least two electrochemical sensors, wherein the arrangement is configured to determine an electrochemical corrosion potential of a zirconium fuel rod in the nuclear reactor based upon the voltages of the at least two electrochemical sensors.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is a continuation-in-part application of U.S. patent application Ser. No. 10 / 951,531 filed Sep. 28, 2004, which is incorporated herein by reference.FIELD OF THE INVENTION[0002]The current invention relates to the determination of electrochemical corrosion potential for components in a nuclear power plant. More specifically, the current invention provides a device and method for determination of electrochemical corrosion potential for both zirconium fuel rods and various structural materials (of the nuclear plant system) at the reactor water temperature in a reactor coolant system for a nuclear power plant, wherein the electrochemical corrosion potential is determined through potential measurements remote from the fuel rod.BACKGROUND INFORMATION[0003]Nuclear reactors, for example boiling water and pressurized water reactors, pass water through a reactor core which contains nuclear fuel. The passing of this water through the...

AI Technical Summary

Benefits of technology

[0011]It is therefore an objective of the present invention to provide an electrochemical corrosion potential measuring system that will allow for determining an electrochemical corrosion potential for both zirconium fuel rods and various structural materials (of the nuclear plant system) at the reactor water temperature during an entire fuel cycle of a nuclear power plant.

[0012]It is also an objective of the present invention to provide an electrochemical corrosion potential measuring system that allows for replacement of a probe and its associated sensors at the end of the sensors' respective lifetime in a cost efficient manner.

Problems solved by technology

These piping systems and components transporting the fluid are made of various materials which may be susceptible to corrosion and irradiation induced or assisted stress corrosion cracking.

Practically, however, maintaining dissolved oxygen, hydrogen and hydrogen peroxide concentrations at this low level is extremely difficult due to the changing water chemistry in the reactor coolant system.

Above the threshold value, however, the possibility of stress corrosion cracking and / or the corrosion rate increases when electrochemical corrosion potential values increase.

First, the probes used are fragile and are only operable for approximately three months as the sensors within the probes deteriorate from heat and radiation.

As a consequence, the probes can only measure the electrochemical corrosion potential for less than 25% of the resident reactor core time precluding their usage around a nuclear reactor.

Nuclear power plant operators' alternatives to alleviate this drawback are few.

The nuclear power plant may be operated without monitoring corrosive conditions, however if the electrochemical corrosion potential is not measured for the entire fuel cycle, conditions may favor the formation of corrosion or stress corrosion cracking, thereby potentially damaging sensitive and expensive nuclear power plant systems.

This alternative is economically unattractive due to the economics of a facility closure.

The second drawback is that existing systems use a discrete measurement point probe for analysis.

Existing systems cannot ascertain if the electrochemical corrosion potential is elevated in a part of the nuclear plant system not directly measured.

The complex and changing materials through a nuclear power plant coolant system do not allow current systems to accurately measure electrochemical corrosion potential of systems relative to one another.

As a consequence, certain systems or subsystems of the nuclear reactor are more prone to corrosion and stress corrosion cracking, as compared to others.

Current systems do not allow the nuclear plant operator to compare data derived from measuring different systems, therefore attention is focused on the probe location.

Current systems also do not determine an electrochemical corrosion potential for the zirconium clad fuel elements, as compared with the electrochemical corrosion potential measured for structural internals or piping materials.

To date, current systems are limited to determining electrochemical corrosion potential of structural or piping members inside the reactor cooling systems.

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