Steam-content and coolant-level emission sensors for a nuclear reactor

Abstract

Fast sensors for the coolant steam content and level are examined. These sensors are based on the detection of the attenuation of the β radiation passing through a coolant layer. The β-particle emitter is a material containing 90Sr and the β-particle detector is a cable with magnesia (MgO) insulation. The current signals as a function of the water level and the average density of the water-air (steam) mixture are obtained using models of the coolant-level and steam-content sensors using β emitters in the form of pellets and cylinders. The density of the air-water mixture was changed by feeding air into the sensitive volume of the steam-content sensor. It is noted that one of the main advantages of the β-emission steam-content and coolant-level sensors is their zero time constant and small size and, for measurements of the steam content of the coolant, the fact that the indications are independent of the temperature and pressure of the medium and the γ-ray dose rate. In addition, the sensors can operate at any point of the reactor vessel or loop.