Leonard William Niedrach

Oxygen Ion—Conducting Ceramics: A New Application in High-Temperature—High-Pressure pH Sensors

Membrane electrodes fabricated from yttria-stabilized zirconia, a representative oxygen ion-conducting ceramic, show a linear voltage response to pH over the range 3 to 8 at 285�C and a pressure of 1200 pounds per square inch (82 atmospheres). Test units have been operated continuously at 285�C without failure for periods as long as 9 days. Unlike sensors which are based on electron transfer couples, such membrane electrodes are insensitive to changes in the oxidation-reduction environment and, in turn, exert no influence upon the environment. Such ceramic membranes can therefore be used for the direct measurement of the pH of geothermal brines, of water in nuclear reactors, and in high-temperature thermodynamic studies on aqueous systems.

Electrochemical Corrosion Potential Models for Boiling-Water Reactor Applications

Abstract The electrochemical corrosion potential (ECP) of stainless steel (SS) was measured under simulated boiling-water reactor (BWR) coolant circuit conditions using a rotating cylinder electrod...

Monitoring pH and Corrosion Potentials in High Temperature Aqueous Environments

Abstract A zirconia membrane electrode that responds to pH can serve admirably as a pH sensor in high temperature aqueous systems. Alternatively, under conditions of known, stable pH, the sensor ma...

Corrosion Potential Behavior of Noble Metal-Modified Alloys in High-Temperature Water

Abstract The effect of Pd or Pt additions on electrochemical corrosion potential (ECP) behavior of various alloys was investigated in 288°C water containing oxygen (O2), hydrogen (H2), and hydrogen...

The application of noble metals in light-water reactors

Corrosion potential is a primary determinant of the stress-corrosion cracking susceptibility of structural materials in high-temperature water. Efforts to minimize stress-corrosion cracking in light-water reactors include adding hydrogen. In someplants’ out-of-core regions, the hydrogen required to achieve the desired corrosion potential is relatively high. In-core, more hydrogen is needed for an equivalent reduction in corrosion potential. Additionally, sIDe effects of high hydrogen-addition rates, including increased 16N turbine shine and 60CO deposition, have also been observed in some cases. An approach involving noble-metal coatings on and alloying additions to engineering materials dramatically improves the efficiency with which the corrosion potential is decreased as a function of hydrogen addition, such that very low potentials are obtained once a stoichiometric concentration of hydrogen (versus oxygen) is achieved.