AN ADVANCED PD PT RELATIVE RESISTANCE SENSOR FOR THE CONTINUOUS MONITORING OF DISSOLVED HYDROGEN IN AQUEOUS SYSTEMS AT HIGH SUBCRITICAL ANDSUPERCRITICAL TEMPERATURES/

An advanced palladium/platinum resistance sensor has been developed to measure, in situ, dissolved hydrogen in high temperature aqueous syst ems. The measurement of hydrogen is based on the well-known fact that the resistance of palladium changes with the absorption of hydrogen in to the lattice. Comparative electrical resistance measurements are mad e between a pair of palladium and platinum probes wound on an oxidized zirconium metal mandrel. Laboratory tests demonstrate that the sensor displays good sensitivity and responsiveness to changes of dissolved hydrogen concentration in an aqueous system at temperatures up to 410 degrees C and at pressures to 4000 psi (276 bar). The sensor is design ed for use in water-cooled thermal power plant heat transport circuits and in supercritical-water reactor media for the reductive destructio n of toxic waste, where continuous hydrogen monitoring may be necessar y.