Howard Ocken

Determination of the high temperature zeta potential and pH of zero charge of some transition metal oxides

Abstract The zeta potential of a particle (i.e. the potential difference between the outer Helmholtz plane of the electrical double layer formed at the particle/fluid interface and the bulk fluid) is a measure of its surface charge. Typically, measurements of the zeta potential have been made at ambient temperature. This paper provides a brief description of new equipment used to measure streaming potentials of oxides at elevated (235°C) temperature from which zeta potentials were calculated. Measurements are reported of the zeta potential of simulated colloids (i.e. corrosion products such as magnetite and hematite) typically generated in the operation of nuclear and fossil-fired power plants. Because zeta potentials provide a framework for interpreting the transport and deposition of colloids, measurements also are reported of oxides that could possibly serve as coatings to prevent deposition of corrosion products on selected surfaces in power plants.

The chemistry and structure of wear-resistant, iron-base hardfacing alloys

The chemistry and microstructure of iron-base alloys resistant to galling wear were determined by using optical microscopy and scanning electron microscopy (SEM). Castings and weld overlays, deposited by the gas tungsten arc and plasma arc welding (GTAW and PAW, respectively) processes, were evaluated. The microstructure typically consisted of a primary austenitic matrix, eutectic carbides (M7C3 type), and noneutectic carbides. Processing techniques that resulted in high cooling rates yielded microstructures with finer features, less complete partitioning of alloying elements to the carbides, and improved resistance to galling wear. Carbon and manganese appeared to improve resistance to galling wear. Nickel was detrimental to galling wear resistance.

Radiation dose management in nuclear power plants

Various approaches available for radiation dose management in nuclear power plants are reviewed in this paper. These approaches include radiation field reduction, accurate dose reporting, good health physics planning, exposure control during job execution, and implementation of a radiation protection culture. For the reduction of radiation fields, a wide variety of technological methods are also available. These include controlling cobalt sources, preconditioning of replacement components, controlling primary chemistry, controlling reactor shutdown and startup chemistry, chemical decontamination, minimizing fuel failures, and using sub-micron purification filters. Successful radiation management requires cooperation among the various groups with relevant responsibilities at a nuclear power plant if the desired exposure goals are to be achieved.