Measurement of Void Fractions in Parallel Rod Arrays

A study was conducted to establish the suitability of the gamma attenuation method for measuring void fractions in a parallel rod array. A lucite mock-up was used to evaluate the accuracy of the method; the error was found to vary from 7 to 13% depending upon the measuring method. Data were taken on an air-water system flowing vertically upward at atmospheric pressure, and were found to agree reasonably well with similar data for rectangular channels and round tubes. The results of this study are being used to guide the execution of the 600 psia boiling water, void experiments which are part of the heat transfer development for the Pathfinder Boiling Water-Integral Superheating Reactor.