Development of procedures for local void fraction measurements

With increasing requirements with respect to the local resolution, the efforts for measurement techniques increase as well. For that purpose AREVA has built up a specific test loop to develop adequate measurement techniques and corresponding validation processes. This loop allows the adjustment of water/steam properties representative of operational and accident conditions of LWRs and has been used to develop a procedure to measure the void fraction distribution in an annulus representing the hydraulic diameter of a typical LWR core sub-channel by means of a gamma tomography system. This paper describes the process, which has been established to reach a reliable high special resolution measurement. Further steps planned to increase the validity of the measurement procedure will also be discussed.