Evaluation of Impurity Monitoring Devices Tested in a Dynamic System

Several devices for the detection and monitoring of impurities in sodium are being evaluated in a dynamic test loop. The loop consists basically of a main loop and test loop and is equipped with cold trap, hot trap, plugging meter, sampling station, impurity injection port, and with the various impurity monitoring and purification devices that are being evaluated. Total sodium inventory in the loop is 150 gal. Sodium circulation is 100 gal/min in the main loop and 7.5 gal/min in the test loop. The loop can be operated up to 1000°F. Three rhometers are being evaluated. In the initial test evaluation of the rhometer, impurities were injected by raising the loop cold-trap temperature, and the impurity level was determined by utilizing plugging temperatures and sodium monoxide solubility data. On this basis, the rhometer response was approximately 0.008% Rper ppm of monoxide. Subsequent tests were performed by directly injecting specific impurities including Na2O, NaOH, NaH, Na2CO3 and H2O into the loop. The rhometer response to the specific impurity injections, except for H2O, was substantially less than had been previously observed. The rhometer response for Na2O injection was a factor of 10 less. More recently, evaluations of the meters with sodium monoxide injections tend to confirm the preliminary results. Four electrolytic oxygen cells are being evaluated in the loop. In the initial semi-quantitative tests, the meters were observed to respond in the predicted direction to specific injections of sodium monoxide and water. The data indicate a large noise-to-signal ratio which primarily has been attributed to changes in ambient temperature. Preliminary tests show that significant step changes in the cell output result from temperature cycling and also from the presence of gamma radiation. In conjunction with the evaluation of the rhometers and oxygen meters, test programmes are being conducted to evaluate both the plugging meter, and sampling and chemical analysis as means of impurity monitoring. The enclosure of the loop sampling station in an inert atmosphere glove box has eliminated atmospheric contamination. Segregation of impurities in samples has been definitely established, and the effect has been found to increase with increasing impurity level. A precision of ± 10%has been demonstrated for the determination of sodium monoxide by the amalgamation analysis technique at the 10 ppm level. Plugging meter readings have been demonstrated to be reproducible within ± 10®F in the range 220-300°F. (author)