X-Ray Absorption Measurement of Steam Voids in Water at High Pressures

Abstract

AbstractX-ray absorption, having been earlier demonstrated to be a unique tool for the accurate measurement of density profiles within gas-fluidized solid systems such as those employed in the chemical and related industries, is being applied to the measurement of steam voids in water flowing through electrically heated rectangular stainless steel channels under conditions of pressure, temperature, flow rate, and heat flux corresponding to “local boiling” (subcooled water) as well as “bulk boiling” (saturated water) in the coolant channels of water-cooled nuclear reactors.A balanced dual-beam photometer system is employed. A dual-beam X-ray tube and two scintillation-crystal-photomultiplier-tube detector probes are mounted in a manner permitting remote-operated traversing of the test channel in the horizontal as well as vertical directions. The photomultiplier tubes are used in a difference circuit with one of the tubes monitoring the test channel and the other a remoteoperated reference wedge. The difference-measuring connection offers common made rejection so that any differential output Is due to a change in attenuation of the testchannel beam. This output is fed through a differential amplifier to a strip-chart recorder.With a test channel consisting of 0.020-in-thick stainless steel walls, backed by 0.062-in. beryllium windows for strength, void concentrations within a 0.250-in, thickness of water currently can be measured with an absolute accuracy of 2% or better (which is far superior to that obtainable with previous techniques) and further improvements in accuracy appear likely. The test channel is enclosed in a heavy steel housing with windows, permitting void measurements to be made at pressures up to 2000 psia.