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Metrology for new generation nuclear power plants-MetroFission.

Johansson, L C; Filtz, J-R*; DeFelice, P*; Sadli, M*; Plompen, A*; Heyse, J*; Hay, B*; Dinsdale, A; Pomme, S*; Cassette, P*; Keightley, J (2014) Metrology for new generation nuclear power plants-MetroFission. IEEE Trans. Nucl. Sci., 61 (4). pp. 2017-2023.

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This paper gives an overview of an EMRP (European Metrology Research Programme) project, MetroFission, that has been looking at solving metrological problems related to a new generation of nuclear power plants. The three year joint project ended in 2013 and this paper gives an overview of the results, outcomes and conclusions of the project, with references to more detailed papers on the specific instrumentation and scientific data that has been developed within this framework.
The proposed Generation IV power plants are designed to run safely, make efficient use of natural resources, minimize the waste and maintain proliferation resistance. In order to reach these goals, the reactor operation involves higher temperatures, high-energy neutron fluence, different types of fuel where the minor actinides are included etc. In this multidisciplinary project, which had 12 partners in 10 countries, the work described was focusing on improved temperature measurements, investigation of thermal properties of advanced materials, determination of new and relevant nuclear data and development of measurement techniques for radionuclides suitable for Generation IV power plants.
The improved temperature measurement for nuclear power plant applications includes the development of a new Fe-C fixed point. A practical acoustic thermometer has been tested at high temperature (1000 °C) with success thanks to the use of innovative signal processing methods. Furthermore, Mo/Nb thermocouples have been obtained with different sheath materials and tested with the aim to achieve for the first time a reference function determined with the best possible uncertainties.
Following reviews of designs and technology proposed for fourth generation nuclear plants effort within this project, with regards to thermal properties of advanced materials for nuclear design, has concentrated on provision of thermodynamic data to support the development of the sodium cooled fast reactor ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration). Data have been critically assessed to represent the potential interaction between the Na coolant and the nuclear fuel.
Reference metrological facilities and methods have been developed or improved for the measurements of normal spectral emissivity and specific heat up to 1500 °C, and thermal diffusivity up to 2000 °C. For this purpose, two complementary facilities based on different metrological approaches (calorimetric and optical methods) were developed at PTB (Physikalisch Technische Bundesanstalt) and LNE (Laboratoire National de Metrologie et d'Essais) for the measurement of emissivity of solid materials at high temperature and a modification of the LNE diffusivimeter. These facilities have been used for the measurement of thermophysical properties of some materials (Ni, MgO and ZrO2), because they have thermal properties similar to those encountered in Generation IV reactors.
Regarding neutron cross sections, the current nuclear databases concentrate on thermal energies, but new fast reactor designs will involve materials exposed to higher energy neutron fields. Advantage has been taken of National Measurement Institutes (NMIs) experience in neutron fluence measurements to improve high-energy cross-section measurements. A secondary fluence standard has been established and used to determine the cross sections of actual interest improving nuclear data standards in the form of reduced measurement uncertainties.
The heavier actinides and their decay products have a role in the future development and adoption of nuclear power plants in whose fuels they will be present in controlled amounts. A list of specific needs for improved actinide decay data has recently been outlined in a review by the IAEA. Responding to those needs, an objective of the MetroFission project was to measure the alpha-particle emission probabilities of 238U with certified isotopic composition. The nuclear data from alpha spectrometry of 238U sources has been successful, obtaining data that will be provided to the international community and that further lower the uncertainties of the nuclear data. The quality of the alpha spectrum measurement, in terms of energy resolution and peak tailing of the 238U alpha spectra, was significantly better than in any previous measurement.
Fission fragments containing beta-decaying isotopes will result from proposed fast reactors. Cryogenic detectors have been developed aimed at improving the measurement of beta spectra and verifying theoretical models. A beta spectrum shape of 63Ni has successfully been obtained. Improvements have been made in the source components and in the source production method in order to lower uncertainties. The exchange effect has been implemented in the calculation of theoretical beta spectra. The measurement of the beta spectrum of 63Ni has for the first time confirmed the exchange effect at very low energy. The energy threshold of the metallic magnetic calorimeter is 180 eV. At this energy, the enhancement of the beta emission due to the exchange effect is larger than 20 %.
Nuclear power plants could benefit from on-site activity measurements of radionuclides including low-energy beta emitters that are abundant but can prove difficult to assay. Within this project, a primary liquid scintillation coincidence counting method called Triple to Double Coincidence Ratio (TDCR) has been modified for this purpose. Five partners have built miniature TDCR systems, miniaturising the instrument¿s detection chamber by using newer, smaller, more efficient photomultiplier tubes. The system also includes replacing the analogue electronic modules with digital acquisition systems and signal processing in order to significantly improve digital coincidence counting (DCC).

Item Type: Article
Subjects: Ionising Radiation
Ionising Radiation > Radioactivity
Identification number/DOI: 10.1109/TNS.2014.2320793
Last Modified: 02 Feb 2018 13:13
URI: http://eprintspublications.npl.co.uk/id/eprint/6325

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