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A Heat-Flux Calorimeter Prototype for Measuring the Thermal Power Released by Radioactive Waste Packages

The French National Metrology Institute [Laboratoire National de métrologie et d’Essais (LNE)] collaborates with the French National Radioactive Waste Management Agency (Andra) in order to develop a direct measurement method of the thermal power of typical radioactive waste (radwaste) packages (with an expanded uncertainty better than 5%). This method must be traceable to the international system of units. In the framework of the European project “metrology for decommissioning nuclear facilities,” LNE and Andra work on the development of prototypes of calorimeters in order to accurately measure the thermal power up to 500 W of real-size radwaste packages (0.175 m3). One of the selected metrological approaches is based on the principle of heat-flux calorimetry. This paper describes in detail the calorimeter prototype (at a reduced scale of 1/5) as well as the design of a radwaste package simulator that is used in this paper to perform its calibration. Preliminary results obtained from the calibration of the calorimeter and from the determination of thermal power are also presented with an investigation of the measurement uncertainties. Numerical simulation of the heat-flux calorimeter prototype is also presented. It shows a good agreement with the experimental results and encourages the construction of a real-size heat-flux calorimeter.