Temperature-Insensitive Additives for Conductive Measurements 

Central Research Institute of Electric Power Industry, Japan 

Abstract: An elaborate measurement technique of void fraction, phasic velocity and phasic temperature helps clarify multi-dimensional and transient boiling flow in nuclear reactor. To quantify void fraction in the gas-liquid flow, the wire mesh sensor is one of the most valuable techniques using an electrode and we employed this method to evaluate the cooling performance of coolant for boiling flow in a heated rod bundle carrying current for the power supply. This paper proposes electric effect and its improving technique, which is caused by methods such as potential gradient, electromagnetic wave and temperature variation. The additional effects of a solute, namely unexpected corrosion, precipitation and other chemical reactions, were also experimentally demonstrated. The aqueous solution, including the solute, increased its electrical conductance and the result had a considerable impact on decreasing the temperature variation of the electrical conductance. This effect suggested that the measurement uncertainty of an equivalent void fraction about temperature in the case of the aqueous solution was smaller than that of pure water. Additionally, it was also clarified that adding solute can increase the ratio between the signal average and its standard deviation without sensor gain and that these ratio values in the case of the aqueous solutions were pursuantly larger than those of pure water. Furthermore, the insulated coating process of the sensor wire except the measuring area increased this effect of improving electric noise.