Accuracy aspects in multiphase flow metering using X-raytransmission

The composition of a mixture of several components flowing through a pipe can be determined by means of an X-ray transmission technique/analysis. We present some aspects of the theory relating to an application in which the component volume fractions of an oil, water, and gas mixture are determined. It will be shown that on fundamental grounds, this technique has its limits regarding the number of components that can be distinguished in relation to the achieved accuracy of the measured attenuation     

Radiation distribution sensing with normal optical fiber

The purpose of this study is to develop a radiation distribution monitor using a normal plastic optical fiber. The monitor has a long operating length and can obtain continuous radiation distributions. A principle of the position sensing is based on a time-of-flight technique. The monitor is sensitive to beta rays or charged particles, gamma rays, and fast neutrons. The spatial resolutions for beta-rays ( ⁹⁰Sr-⁹⁰Y), gamma-rays (¹³⁷Cs), and D-T neutrons are 30, 37, and 13 cm, respectively. The detection efficiencies for the beta-rays, gamma-rays, and D-T neutrons are 0.11%, 1.6×10 ^-5% and 1.2×10^-4%, respectively. The effective attenuation length of the detection efficiency is 18 m. In this paper, we describe the basic characteristics of this monitor     

Challenges left in the area of in-vessel melt retention

The in-vessel melt retention becomes an important safety objective for the present or future middle power nuclear plants, so care has to be taken in the evaluation of the various phenomena related to ensuring the feasibility of this objective. Since the prediction of the relevant phenomena has to be performed for the prototypical accident conditions, the applicability of the measured data or of the correlations derived from these measurements have to be established and the uncertainties determined. In this context, most uncertainties are introduced by the non-prototypicalities in the experiments. The paper describes the major findings from the OECD RASPLAV project and discusses the remaining challenges left in the area of in-vessel molten corium coolability.