Research and development in France

Guidelines. The main objective is to define processes allovring inspection, diagnosis and intervention to be carried out in the reactor block. Any intervention is considered to take place during reactor shutdown, that is, with sodium at a temperature of about 180°C. For routine inspections, the level of sodium will not be lowered. Therefore, under-sodium 

Telemetry. Telemetry is used for detecting displacements of structures or components. The methods chosen are optical measurement devices using light beams, preferably laser, which are reflected by targets or by the surfaces themselves. These techniques are subject to the difficulties specific to light transmission, in particular  

The research and development already performed has shown that the uncertainties about the refraction factor are compatible with the accuracy sought. The characteristics of the targets or reflecting surfaces as well as their evolution over time (deposits), and the incidoice of the diffusion factor, have still to be defined. The most adequate methods will have to be selected, taking account of the accuracy needed and the reactor constraints. These points are to be studied initially by means of models and a number of tests on a simplified mock-up. The process will then be validated on a mock-up representative of the cover gas. 

Volumetric controls. They consist in detecting possible health flaws (cracks). The problem is rather similar to the control of the nuun tank but it is more difficult due to sodium aerosols and/or mesos that may have deposited over the surfaces to be inspected. The use of ultrasound is already known and research and development will allow specific difficulties to be assessed and solved  

Telemetry. In order to optimise known means, a study and a series of in-water tests have been performed. A measurement accuracy of 2 mm at a distance of 5 m was achieved. This accuracy will have to be confirmed by in-sodium tests on some particular points and by an overall qualification at full-scale 1 probe. New woric is in progress in the CEA in order to develop a technique using ultrasonic reflection  

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