Validation Testing for Automated Solubility Measurement Equipment Final Report
Laboratory tests have been completed to test the validity of automated solubility measurement equipment using sodium nitrate and sodium chloride solutions (see test plan WRPS-1404441, “Validation Testing for Automated Solubility Measurement Equipment”). The sodium nitrate solution results were within 2-3% of the reference values, so the experiment is considered successful using the turbidity meter. The sodium chloride test was done by sight, as the turbidity meter did not work well using sodium chloride. For example, the “clear” turbidity reading was 53 FNU at 80 °C, 107 FNU at 55 °C, and 151 FNU at 20 °C. The sodium chloride did not work because it is granular and large; as the solution was stirred, the granules stayed to the outside of the reactor and just above the stir bar level, having little impact on the turbidity meter readings as the meter was aimed at the center of the solution. Also, the turbidity meter depth has an impact. The salt tends to remain near the stir bar level. If the meter is deeper in the slurry, it will read higher turbidity, and if the meter is raised higher in the slurry, it will read lower turbidity (possibly near zero) because it reads the “clear” part of the slurry. The sodium chloride solution results, as measured by sight rather than by turbidity instrument readings, were within 5-6% of the reference values.