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In order to justify the concept of in-vessel core melt retention, it is necessary to understand the thermal and physico-chemical phenomena. Especially the interaction of the molten pool with the reactor vessel during outside cooling needs to be understood. These phenomena are very complex, in particular, where interactions with the oxidic melt are concerned. In the early stages of the retention process, the oxidic corium and the vessel steel interact under the conditions of low oxygen potential in the melt. These conditions can be simulated by a molten corium having the composition UO2/ZrO 2Zr, where the degree of Zr-oxidation is in the range between 30 % (C-30) and 100 % (C-100). Corresponding experiments with prototypic melts at low oxygen potentials are being performed in the ISTC METCOR project 2nd phase. These are: MC 5 of corium composition 71w%UO2-29w%ZrO 2 (C-100) in neutral atmosphere (argon), MC 6 of corium composition 76w%UO2-9w%ZrO2-15w%Zr (C∼30), also in argon. In test MC 5, the interaction of molten C-100 corium with a water-cooled steel specimen was studied for the following maximum temperatures at the specimen surface: 1075°C, 1180°C, 1315°C and 1435°C. The total duration of the experiment was ∼ 36 hours. The MC5 test serves as a reference test for determining the characteristics of the interaction between oxidic melt and steel specimen under the conditions of minimum chemical interaction potential. To investigate the effect of substoichiometry, test MC 6 was then performed with suboxidized molten corium C∼30. The maximum surface temperature of the cooled steel specimen was held at ∼ 1400°C. The test duration was ∼ 10 hours. The ablation phenomena were found to differ significantly from those observed both in the reference test, as well as in former tests with oxidized melts, as they involved the formation of a low-melting metallic phase at the interface which contains iron, zirconium and uranium. The paper summarizes the results of the experiments a, cited By (since 1996) 2. QC 20120306

The project ECOSTAR (acronym for ex-vessel core melt stabilization research) involves in total 17 orgnizations from five European countries. The objective of the project is to demonstrate the technical feasibility of core melt mitigation measures outside the reactor pressure vessel (RPV) as well as the validation of a selected set of codes in order to provide the necessary input for the definition of a convincing safety concept to control corium melts for both existing and future reactors. The ECOSTAR projects is focused on three key phenomena for ex-vessel mitigation measures, namely melt release from RPV, ex-vessel corium transport and long-term corium stabilization. The extensive work program covers different scenarios and consists of a large number of experiments with both simulant and real materials, code development and validation as well as analytical activities. This paper presents the progress of work per end of the year 2001 and the results obtained since the launch of the project.

Traditionally, the P. T. V techniques use a camera to record the displacement of the particles. Then, it is necessary to develop the negative film in order to digitize the images. In this paper, we present a now P.T.V method which is based on colored pulses and a color video camera (3 CCD camera). The particles images are digitizing in real time with a resolution of 24 bits and an image processing software allows to obtain the velocities field. After describing the experimental procedure, some results are presented on a water sock-up. (Author)

This report presents an utilization of laser measurement technique in the specific domain of sodium aerosols. More especially aerosols velocities and sizes were studied using Laser Doppler Velocimetry and Phase Doppler method. The difficulties encountered and synthesis of the experimental results obtained are detailed.