An electrical resistivity monitor for the detection of composition changes in Pb-17Li

An electrical resistivity monitor for the detection of composition changes in the lithium-lead eutectic alloy, Pb-17Li, has been developed. A miniature electromagnetic pump is used to sample alloy continuously from a pool or loop system and force it through a capillary section, within which the necessary resistance measurements are made, prior to its return to the bulk source. To calibrate the monitor, detailed resistivity-temperature and resistivity-composition data have been determined for Pb-Li alloys at temperatures from 600 to 800K and compositions from 0 to 20.5 at% Li. The resistivity increases with both temperature and composition; for Pb-17li at 723 K, dρ/dT=0.054x10-8ΩmK-1, and dρ/d[Li]=1.27x10-8Ωm(at% Li)-1. The sensitivity of the monitor is such that changes in composition of as little as ±0.05 at% Li can be detected and its response time is limited soley by the rate of sampling. (orig.)