In liquid breeder blankets (LBBs), MHD flowmeters are considered as the most suitable tool for the measurement of volumetric flowrate of the Pb-Li coolant at operational temperatures as high as 500oC. An important aspect for a MHD flowmeter is its calibration. Presently, MHD flowmeters are being calibrated using the flowrate data estimated directly or indirectly from analytical expression. In few other cases, the calibration had been performed at room temperature using a surrogate liquid metal such as Hg or GaInSn, for which sophisticated diagnostic tools are readily available. Thereafter, the calibration factor had been adjusted suitably for the flowmeter to use it in Pb-Li applications. These calibration processes may not provide high accuracy for the flowmeter, as the analytical expression does not contain all the parameters affecting the signal generated in the flowmeter. Moreover, the surrogate liquids may not have the exact contact resistance as that of Pb-Li. An absolute way for flowmeter calibration would be to measure the volume or weight of liquid transferred per unit time through the flowmeter and use this information to calibrate the flowmeter. However, for high operational temperatures this is not an easy task due to the lack of precise diagnostic tools and welded connections pipes. Typically the connection pipes are made up of SS 316 and welded to other components of the test facility. Therefore, there will be reaction forces on connection pipes which causes errors in the measurement of the weight of liquid being transferred. In the present work, a novel technique has been devised using an edge welded bellow to isolate the reaction force of the connection pipes. This would allow us to precisely measure the weight of liquid being transferred through the flowmeter and hence calibrate the MHD flowmeter in an absolute manner. The facility will have Pb-Li as its experimental liquid operating at a temperature of 350oC with maximum flowrate up to 6 kg/s.
A schematic of the experimental set up is shown in Fig-1. The experimental plan is to transfer the molten Pb-Li from dump tank to the collector tank through the flowmeters and record the weight of liquid transferred per unit time. Based upon the measurement of Pb-Li weight transferred per unit time, the flowmeter would be calibrated. A schematic of the internal arrangement of edge welded bellow for isolating the reaction force on the collector tank is shown in Fig-2. The details of experimental set up, experimental procedure and flowmeter calibration results will be presented.
|Country or International Organization||India|
|Affiliation||Institute for Plasma Research, Bhat, Gandhinagar, Gujarat, 382428|