Void fraction measurement liquid level detection concept assessment and development

The Coolant Inventory Monitor System for measuring the amount and the distribution of coolant in the primary system under accident conditions of a nuclear power plant is described in this report. This system is based on measuring the local void fraction of the coolant at selected points in the vessel and piping system and then estimating the coolant inventory. This report summarizes the development of the measurement instrument, the supporting tests and the development of the supporting software. Accuracies of +-2% as compared with delta pressure cells can be obtained over void fractions ranging from 0 to 90%. The system can provide local measurements of void fraction and uses probes as small as 0.015 x 1.0 x 0.3 in. (0.038 x 2.54 x 0.76 cm). Experimental test data are shown for temperatures up to 570/sup 0/F (572K). The system can be used up to the critical point. The graphics display shows a real time display of void fraction for up to fifteen channels and gives the instantaneous as well as a running average for each channel. This instrument is believed to meet the intent of the NRC by being able to measure the amount of water above the reactor coremore » under all types of accidents. 10 refs., 31 figs., 3 tabs.« less