This paper describes all the procedures and methods currently used at UPV (Universitat Politécnica de Valencia) and UJI (University Jaume I) for the development and use of sensors for multi-phase flow analysis in vertical pipes. This paper also describes the methods that we use to obtain the values of the two-phase flow magnitudes from the sensor signals and the validation and cross-verification methods developed to check the consistency of the results obtained for these magnitudes with the sensors. First, we provide information about the procedures used to build the multi-sensor conductivity probes and some of the tests performed with different materials to avoid sensor degradation issues. In addition, we provide information about the characteristics of the electric circuits that feed the sensors. Then the data acquisition of the conductivity probe, the signal conditioning and the data processing including the device that have been designed to automatize all the measurement process of moving the sensors inside the channels by means of stepper electric motors controlled by computer are shown in operation. Then, we explain the methods used for bubble identification and categorization. Finally, we describe the methodology used to obtain the two-phase flow information from the sensor signals. This includes the following items: void fraction, gas velocity, Sauter mean diameter and interfacial area concentration. The last part of this paper is devoted to the conductance probes developed for the annular flow analysis, which includes the analysis of the interfacial waves produced in annular flow and that requires a different type of sensor.

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An upward isothermal co-current air-water flow in a vertical pipe ( 50.2 mm inner diameter ) has been experimental investigated. Local measurements of void fraction, interfacial area concentration ( IAC ), interfacial velocity and Sauter mean diameter were measured using a double sensor conductivity probe. Liquid velocity and turbulence intensity were measured using Laser Doppler Anemometry (LDA). Different air-water flow configurations was investigated for a liquid flow rate ranged from 0.491 m/s to 0.981 m/s and a void fraction up to 10 % .For each twophase flow configuration twenty five radial position and three axial locations were measured by the conductivity probe methodology, and several radial profiles was measured with LDA at different axial positions.

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Interdiffusion coefficients of plutonium and uranium have been calculated from electron microprobe analysis of diffusion couples UO;! (green compact) / Pu02 (green compact) or U02 (green compact) / U02+Pu02 (green compact). A series of these diffusion couples was sintered at 1773, 1873 and 2023 K during O to 50 hours and under controlled oxygen potential (-88,-95 and-125 kcal/mol). The results show that grain-boundary diffusion predominates in the overall diffusion process, even during sintering and that lattice diffusion is very slow. The sintering process enhances the interdiffusion coefficients which are greater by one order of magnitude compared to those of polycrystalline diffusion couples.