atw - International Journal for Nuclear Power | 03.2020

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atw Vol. 65 (2020) | Issue 3 ı March 140 RESEARCH AND INNOVATION Improved Metrology of Thermophysical Properties at Very High Temperatures: The EMPIR Project Hi-TRACE Konstantinos Boboridis and Bruno Hay Introduction Power plants, aerospace and materials processing are prominent examples of technologies and industrial processes in which materials are exposed to (very) high temperatures. Refractory materials are employed not only to withstand these high temperatures, but also because of their favourable physical properties at these temperatures. Particularly nuclear reactors are known for the extreme conditions of temperature at which the fuel materials have to operate during several years, in combination with radiation from the fission process. The performance of the fuel, as well as the cladding, is key for the safety of the system and needs, thus, be understood in detail. Scientists and engineers striving to improve the safety margins of a particular technology, as well as its efficiency and competitiveness, often do that by developing new materials or by optimizing existing ones. For instance, in recent years there has been renewed interest in SiC-based composite materials and in so-called ultra-high-temperature ceramics. For example, they are investigated as cladding for enhanced accident tolerant fuel in nuclear power plants, or as components of gas turbine aerospace engines. In these cases design-base and beyond-design-base accident scenarios need to be simulated, during which materials would be exposed to exceedingly high temperatures. Reliable values of thermophysical properties of materials at very high temperatures, however, are typically scarce, increasingly uncertain with temperature, and sometimes contradictory. These measurements are indeed challenging. Moreover, when employing such data in analyses and simulations that are used for licensing of nuclear power plants and risk assessment in general, it is important to ensure their traceability to national or international standards and to establish credible measurement uncertainties. This requires appropriate standard reference materials and reference facilities that can be used to validate a measurement technique. Project description Hi-TRACE is a project aiming to close this gap by developing reference facilities and validating measurement methods, complete with measurement uncertainty budgets, for several technologically important thermophysical properties at temperatures up to 3,000 °C. Its full title is ‘Industrial process optimisation through improved metrology of thermo physical properties’. It brings together eleven partners from five European countries: four National Metrology Institutes (NMIs) or Designated Institutes (DIs), three industrial partners, two universities, and two research centres (see Table 1). The project is receiving funding through EMPIR, the European Metrology Programme for Innovation and Research, which is co-financed by the Participating States and the European Union’s Horizon 2020 research and innovation programme. It was kicked-off in July 2018 and will run for three years with a budget of about 1.6 million Euros. The project’s work packages address the measurement of thermal diffusivity, specific heat, emissivity and melting temperature up to 3,000 °C, as well as the quantification of de-bonding between solid materials Full name Laboratoire national de métrologie et d’essais (LNE) NPL Management Limited (NPL) Physikalisch-Technische Bundesanstalt (PTB) Institut Za Nuklearne Nauke Vinča ArianeGroup SAS NETZSCH Gerätebau GmbH Commissariat à l’énergie atomique et aux énergies alternatives Hochschule für Angewandte Wissenschaften Würzburg-Schweinfurt (FHWS) Technische Universität Graz (TUG) Bayerisches Zentrum für Angewandte Energieforschung e.V. (ZAE Bayern) European Commission, Joint Research Centre (JRC) | Tab. 1. Project partners. | Fig. 1. Hi-Trace: Topics. and the resulting change in thermal contact resistance (see Table 2). These thermophysical properties are significant for their role in heat transfer and in thermal management/ thermal protection systems. In addition, the knowledge of a material’s emissivity is essential for optical temperature measurements, including thermography, which is often the only viable option due Country France United Kingdom Germany Republic of Serbia France Germany France Germany Austria Germany European Commission Research and Innovation Improved Metrology of Thermophysical Properties at Very High Temperatures: The EMPIR Project Hi-TRACE ı Konstantinos Boboridis and Bruno Hay
atw Vol. 65 (2020) | Issue 3 ı March WP N° WP1 WP2 WP3 WP4 WP5 WP6 | Tab. 2. Work packages. Work package title Establishment of traceability for thermal diffusivity measurements at temperatures up to 3000 °C Establishment of traceability for specific heat measurements at temperatures up to 3000 °C Establishment of traceability for emissivity measurements and improved metrology for temperature of fusion at temperatures up to 3000 °C Establishment of methods for quantifying de-bonding at high temperatures (above 1000 °C) Creating impact Management and coordination of good practice guides for calibration and measurement of these thermophysical properties. A workshop for the end-user community will be organised and e-learning modules will be prepared. Finally, the datasets generated in the inter-laboratory comparisons will be made available through open repositories, as long as they are not covered by confidentiality agreements with the industrial partners. More information, including contact information, can be found on the project’s website (https:// hi-trace.eu). Acknowledgement This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme. This article is written on behalf of all partners listed in Table 1. RESEARCH AND INNOVATION 141 | Fig. 2. Emissivity and Temperature of Fusion. to the very high temperatures involved or other parameters such as limited access and fast response time. Reference facilities are currently being developed by the involved NMIs and DIs for thermal diffusivity, specific heat, and emissivity measurements at very high temperatures. These facilities will then undergo a metrological validation before being used to characterise refractory materials of technological significance at the highest temperatures possible. Existing setups and measurement techniques, already in use by the industrial and academic partners, will be validated against the newly | Fig. 3. Temperature rise distribution on the rear face half-way through the test. — NPL Matlab model. developed facilities. Techniques for measuring the melting temperature of refractory materials will benefit from the emissivity data generated by the project. In addition, techniques are being developed to quantify the state of the mechanical adhesion of solid materials, in particular functional layers for thermal or corrosion protection above 1,000 °C, by knowledge of the thermal contact resistance. They will be validated in a second step using well-characterised multilayer artefacts suitable for high temperatures, which will also be developed in the frame of this project. The project is coordinated by the French National Metrology Institute (LNE). An advisory board has been set up to regularly review progress and provide guidance in terms of relevance for the end users. Particular importance is placed upon ensuring the widest possible dissemination of the knowledge generated within the project, including to standards bodies, as well as collecting feedback from end users, such as instrumentation manufacturers, actors in aerospace, nuclear energy, additive and conventional manufacturing involving very high temperatures. Inter-laboratory comparisons organised during the project will lead to the publication Authors Konstantinos Boboridis European Commission Joint Research Centre (JRC) Karlsruhe, Germany Bruno Hay Laboratoire national de métrologie et d’essais (LNE) Trappes, France Research and Innovation Improved Metrology of Thermophysical Properties at Very High Temperatures: The EMPIR Project Hi-TRACE ı Konstantinos Boboridis and Bruno Hay
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