Year
1996
Abstract
In nuclear t%el reprocessing, the mechanical design of vesseIs takes on various shapes and dimensions in order to conform to safety design criteria. From a safeguards point of view many of these vessels also have a very high strategic importance and so accountability has to be supporred with volume measurement techniques where the uncertainty in measurement has to very small. The most common technique applied for volume measurement in both large and small tanks is the bubbler probe. Throughout the operation of the plant the physical and chemical characteristics of the solution can vary, leading to such problems as possible plugging of bubbler probes, with consequences for process control and safeguards. Work has been conducted at the JRC-Ispra TAME (Tank Measurement) Laboratory with the scope of examining the physical variables affecting the design choice of bubbler probe techniques for liquid level measurement. In the past, fluctuations in the pressure readings associated with bubble formation and separation have been a limiting factor in the precision of pneumercator measurements. Application of PC computers for control and data acquisition and highly sensitive electromanometers with resolutions equal to 0.02mm hydrostatic pressure have been used to evaluate the empirical relations between bubble and liquid height. Results are reported on the effects of tube size simulating the plugging phenomena all under slow and fast bubbling air purge rates. A fast track portable pressure measurement system is utilised to monitor the bubble growth and recognition patterns to determine the onset of plugging,