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The TIR100-2 emissometer (manufactured by Inglas GmbH & Co.KG) is an emissivity measurement device used by several producers of thermal insulation products for buildings and by some organizations certifying performance of insulation products. A comparison of emissivity measurements on low-emissivity foils involving different measurement techniques, including the TIR100-2 emissometer, gave widely dispersed results; the discrepancies were not explained. The metrological performance of the TIR100-2 emissometer and the uncertainties for measurement on reflective foils was not known, which could be detrimental to users. In order to quantify the performance of TIR100-2 devices for measurement of total near-normal emissivity of low-emissivity foils, the Laboratoire National de Métrologie et d'Essais (LNE) analyzed in detail the measuring principle and listed the associated assumptions and uncertainty sources. A TIR100-2 emissometer actually measures the reflectance and, for opaque materials, the emissivity is calculated from the measured reflectance. The parameters analyzed experimentally are the temperature stability and uniformity of the thermal radiation source, the emissivity of the radiation source, the response function linearity and the spectral sensitivity of the radiometric detection system measuring the reflected radiation, the size of the measurement area, and the measurement repeatability and reproducibility. A detailed uncertainty budget was established. The uncertainty sources taken into account are the uncertainties of the emissivities of the two calibrated standards used for calibration, the stability and uniformity of the radiation source temperature, the non-linearity and the spectral sensitivity of the radiometric detection system, the specific measurement condition related to the radiation source temperature, the uncertainties related to the temperatures of the standards and the sample, the noises on results, and the non-homogeneity in emissivity of the tested material. The combined measurement uncertainty was calculated for different types of reflective foils; the expanded uncertainty is around 0.03 for total near-normal emissivity measurements on smooth low-emissivity foils. A measurement campaign on five types of low-emissivity foils, involving four TIR100-2 emissometers, and a comparison to a primary reference setup at the Physikalisch-Technische Bundesanstalt (PTB) confirmed the uncertainties assessed.

The French National Metrology Institute LNE has improved its homemade laser flash apparatus in order to perform accurate and reliable measurements of thermal diffusivity of homogeneous solid materials at very high temperature. The inductive furnace and the associated infrared (IR) detection systems have been modified and a specific procedure for the in situ calibration of the used radiation thermometers has been developed. This new configuration of the LNE’s diffusivimeter has been then applied for measuring the thermal diffusivity of molybdenum up to 2200 °C, tungsten up to 2400 °C and isotropic graphite up to 3000 °C. Uncertainties associated with these high temperature thermal diffusivity measurements have been assessed for the first time according to the principles of the “Guide to the Expression of Uncertainty in Measurement” (GUM). Detailed uncertainty budgets are here presented in the case of the isotropic graphite for measurements performed at 1000 °C, 2000 °C and 3000 °C. The relative expanded uncertainty (coverage factor k = 2) of the thermal diffusivity measurement is estimated to be between 3 % and 5 % in the whole temperature range for the three investigated refractory materials.

The French National Metrology Institute [Laboratoire National de metrologie 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.

Decommissioning of nuclear facilities incurs high costs regarding the accurate characterisation and correct disposal of the decommissioned materials. Therefore, there is a need for the implementation of new and traceable measurement technologies to select the appropriate release or disposal route of radioactive wastes. This paper addresses some of the innovative outcomes of the project “Metrology for Decommissioning Nuclear Facilities” related to mapping of contamination inside nuclear facilities, waste clearance measurement, Raman distributed temperature sensing for long term repository integrity monitoring and validation of radiochemical procedures.

Raman distributed temperature sensing techniques (Raman-DTS) are currently meeting a growing interest from the industry as they are a promising and cheap alternative to classical temperature measurements which require the deployment of many sensors. The reliability of the DTS measurements, as well as the traceability to the temperature standards, must be ensured throughout the entire period of use (typically over a few tens of years for nuclear waste repositories and hydraulic structures). LNE, in association with Andra and EDF has developed facilities dedicated to the metrological characterization of Raman DTS devices. A first benchmark performed on five devices from different manufacturers has been performed following experimental procedures which enable a relevant comparison of these instruments. This paper defines the proposed metrological features to be evaluated for each Raman DTS system, and presents a ranking method enabling to provide useful pieces of information to the final users for the selection of the most appropriate device to the requirements of their applications.

This paper presents the effects of short-term and long-term temperature exposure on noble metal thermocouples in the range from 1000 degrees C to 1720 degrees C in oxidizing atmosphere (air). As thermocouples voltage output depends on the wire material of which the sensors are constructed, high-temperature and long continuous exposure to limit temperatures can introduce changes to the materials composition and structure. This can result in drift of generated voltage independent of the thermal environment and into reduced lifetime of the sensors. The intensions of conducted measurements were to determine the drift and lifetime of commonly available alumina-sheathed noble metal thermocouples and furthermore to establish traceable techniques to enable lifetime testing and thermoelectric stability evaluation of noble metal thermocouples at high temperatures. Result presented within this paper is not intended to test the capabilities of thermocouple Types B, R and S in general, but to show a possible behavior in the above-specified temperature conditions. This work puts more emphasis on the procedures that can be used for regular checks of intensely used thermocouple. Results obtained by this study show that the long-term temperature drift of Type B thermocouples at 1600 degrees C, and R-, S-type thermocouples at 1000 degrees C are much smaller than thermoelectric stability declared by IEC 60584-1:2013 standard (International standard IEC 60584-1:2013, ThermocouplesPart 1: EMF specifications and tolerances, 2013) tolerance classes after exposure to thermal stress up to 4months. More specifically tolerance for class 1 thermocouple Types R, S from 0 degrees C up to 1100 degrees C is +/- 1 degrees C and for class 2 tolerance for Type B at 1600 degrees C is +/- 1.5 degrees C. The short-term thermoelectric stability of R- and S-type thermocouples exposed to 1600 degrees C for repeated 8h periods has been within 2 degrees C when measured by comparison with a reference Pt-Pd thermocouple at 960 degrees C. The short-term thermoelectric stability of B-type thermocouple when exposed to 1720 degrees C for repetition of 8h has been within 1 degrees C.

Thermocouples are prone to significant drift in use particularly when they are exposed to high temperatures. Indeed, high-temperature exposure can affect the response of a thermocouple progressively by changing the structure of the thermoelements and inducing inhomogeneities. Moreover, an oxidizing atmosphere contributes to thermocouple drift by changing the chemical nature of the metallic wires by the effect of oxidation. In general, severe uncontrolled drift of thermocouples results from these combined influences. A periodic recalibration of the thermocouple can be performed, but sometimes it is not possible to remove the sensor out of the process. Self-validation methods for thermocouples provide a solution to avoid this drawback, but there are currently no high-temperature contact thermometers with self-validation capability at temperatures up to \(1600\,^{\circ }\hbox {C}\). LNE-Cnam has developed fixed-point devices integrated to the thermocouples consisting of machined alumina-based devices for operation under oxidizing atmospheres. These devices require small amounts of pure metals (typically less than 2 g). They are suitable for self-validation of high-temperature thermocouples up to \(1600\,^{\circ }\hbox {C}\). In this paper the construction and the characterization of these integrated fixed-point devices are described. The phase-transition plateaus of gold, nickel, and palladium, which enable coverage of the temperature range between \(1000\,^{\circ }\hbox {C}\) and \(1600\,^{\circ }\hbox {C}\), are assessed with this self-validation technique. Results of measurements performed at LNE-Cnam with the integrated self-validation module at several levels of temperature will be presented. The performance of the devices are assessed and discussed, in terms of robustness and metrological characteristics. Uncertainty budgets are also proposed and detailed.

Within the frame of a European project called Eura-Thermal, the general objective was to upgrade the regional metrological infrastructure (Bosnia & Herzegovina, Croatia, Ireland, Serbia...) with new capabilities, especially in the field of thermal measurements. This paper highlights the strategy used for improving in the short term, scientific knowledge transfer and the capabilities of different emerging institutes. Furthermore, as a main output, the impacts and benefit for Industry and for the end-users are also presented as examples. © 2018 Institute of Physics Publishing. All rights reserved. XXII World Congress of the International Measurement Confederation (IMEKO 2018)

This paper complements the existing measurement standards and literature for high-temperature guarded hot plates (HTGHPs) by addressing specific issues relating to thermal conductivity measurement of technical insulation at high temperatures. The examples given are focused on the designs of HTGHPs for measuring thin thermal insulation. The sensitivity studies have been carried out on major influencing factors that affect the thermal conductivity measurements using HTGHPs, e.g., the uncertainty of temperature measurements, plate flatness and center-guard gap design and imbalance. A new configuration of center-guard gap with triangular shape cross section has been optimized to obtain the same thermal resistance as a 2 mm wide gap with rectangular shape cross section that has been used in the HTGHPs at NPL and LNE. Recommendations have been made on the selections of heater plate materials, high-temperature high-emissivity coatings and miniature temperature sensors. For the first time, thermal stress analysis method has been applied to the field of HTGHPs, in order to estimate the effect of differential thermal expansion on the flatness of thin rigid specimens during thermal conductivity tests in a GHP.

The eutectic Co–C is a promising system to serve as a thermometric fixed point beyond the freezing point of copper ( $$1084.62\,^{\circ }\mathrm{C}$$ ). Some national metrology institutes have developed, characterized, and compared their Co–C fixed-point cells based on conventional designs. Indeed, the fixed-point cells constructed are directly inspired by the technologies applied to the fixed points of the ITS-90 to the lower levels of temperature. By studying the eutectic metal–carbon systems, is appears that the high temperatures of implementation give a set of difficulties, such as the strong mechanical stresses on the graphite crucibles, due to the important thermal expansion of the eutectic alloys during their phase transitions. If these devices are suitable with research activities to serve like primary standards, it is not envisaged to propose them for a direct application to the calibration activities for the industry. As regards the limited robustness of the conventional fixed-point cells constructed, an intensive use of these device would not be reasonable, in term of cost for example. In this paper, a new Co–C fixed-point design is introduced. This low cost device has been developed specifically for intensive use in thermocouple calibration activities, with the aim of achieving the lowest level of uncertainties as is practicable. Thus, in this paper, the metrological characterization of this device is also presented, and a direct comparison to a primary Co–C fixed-point cell previously constructed is discussed.

In the framework of the European Metrology Research Project ENG08 “MetroFission,” LNE-Cnam and NPL have undertaken cooperative research into the development of temperature measurement solutions for the next generation of nuclear fission power plants. Currently, in-pile temperature monitoring is usually performed with nickel-based (Type K or N) thermocouples. When these thermocouples are exposed to a neutron flux, the thermoelements transmute, leading to large and unknown drifts in output. In addition, it is impossible to routinely recalibrate the thermocouples after irradiation for obvious reasons of safety. To alleviate this problem, both LNE-Cnam and NPL have developed, via differing approaches, in situ calibration methods for the thermocouples. The self-validating thermocouple methodologies are based on the principle of a miniature fixed-point cell to be co-located with the thermocouple measurement junction in use. The drift of the thermocouple can be monitored and corrected for by regular determination of the output at the phase transition of the fixed-point material: in effect performing regular in situ calibration checks. The two institutes have constructed miniature fixed-point cells for use at three different temperatures; the freezing point of silver $$(961.78\,^{\circ }\mathrm{C}$$ ; LNE-Cnam), the freezing point of copper $$(1084.62\,^{\circ }\mathrm{C}$$ ; LNE-Cnam and NPL), and the melting point of Fe–C ( $${\sim }1154\,^{\circ }\mathrm{C}$$ ; NPL). This paper introduces the construction and validation of the miniature fixed-point cells prior to use, to ensure traceability to the ITS-90. A comparison of the performance of the two cell designs is discussed, where typical industrial Type N thermocouples have been used for measurement of the fixed-point cells. Such initial measurements demonstrate the feasibility of each of these two approaches.

In the framework of the European Metrology Research Programme ENG08 “MetroFission” project, two National Measurement Institutes, LNE-Cnam (France) and NPL (UK), have cooperatively developed methods of in situ validation of thermocouple output for application in next-generation nuclear fission power plants. Miniature fixed-point cells for use at three temperatures were constructed in the first step of this project: at the freezing point of silver (\(961.78\,^{\circ }\mathrm{C}\)), the freezing point of copper (\(1084.62\,^{\circ }\mathrm{C}\)), and the melting point of the iron–carbon eutectic (\(1154\,^{\circ }\mathrm{C}\)). This paper reports the results of a second step in the study, where the robustness of the self-validation method has been investigated. Typical industrial Type N thermocouples have been employed with each of the miniature fixed-point devices installed, and repeatedly thermally cycled through the melting and freezing transitions of the fixed-point ingots. The devices have been exposed to a total of up to 90 h in the molten state. Furthermore, the LNE-Cnam devices were also subjected to fast cool-down rates, on five occasions, where the rate is estimated to have been between \(150\,^{\circ }\mathrm{C}\,{\cdot }\min ^{-1}\) and \(200\,^{\circ }\mathrm{C}\,{\cdot } \min ^{-1}\). The devices are shown to be repeatable, reliable, and robust over the course of these tests. The drift of the Type N thermocouple has been identified separately to the behavior of the device. A reliable method for improving thermocouple performance and process control is therefore demonstrated. Requirements for implementation and the advantages of each approach for monitoring and correcting thermocouple drift are discussed, and an uncertainty budget for self-validation is presented.

A series of high-temperature fixed points (HTFPs) Pt–C (1738 $$^{\circ }\mathrm {C}), \text {Cr}_{7}\text {C}_{3}{-\text {Cr}}_{3}\text {C}_{2}\,(1742\,^{\circ } \mathrm{C}), \text {Cr}_{3}\text {C}_{2}{-\text {C}}\,(1826\,^{\circ }\mathrm{C})$$ , and Ru-C (1953 $$^{\circ }\text {C}$$ ) have been constructed at the National Physical Laboratory (NPL) and the Laboratoire National de metrologie et d’Essais and Conservatoire national des arts et metiers (LNE-Cnam). These are required for the calibration of high-temperature thermocouples in the framework of work package 6 of the European Metrology Research Programme IND01 project “HiTeMS.” The goal of this work package is to establish a European capability that can determine low-uncertainty reference functions of non-standard high-temperature thermocouples. For reference functions to be widely applicable, measurements must be performed by more than one institute and preferably by more than one method. Due to the high price of the ingot materials, miniature HTFP cells are used. NPL and LNE-Cnam constructed their HTFP cells with different designs; these are described here, together with the performance of the cells using both radiation thermometry and thermocouples. The melting temperature of the Ru–C cells (for thermocouple calibrations) was determined using radiation thermometry at both NPL and LNE-Cnam, and the two results are compared. The suitability of the cells for calibration of W–Re and Rh–Ir thermocouples is evaluated, and some results are presented. Some discussion is given regarding the materials challenges when calibrating Rh–Ir thermocouples up to 2000 $$^{\circ }$$ C.

In order to enhance the availability of facilities in the field of high temperature contact thermometry in European emerging National Metrology Institutes (NMIs) and Designated Institutes (DIs), where access to types of facilities is currently limited an EMPIR Research Potential Project named Eura- Thermal has been launched. This project develop skills and tools for less experienced NMIs/DIs in order to acquire the required knowledge and expertise in temperature metrology. Within the frame of the work package dedicated to contact thermometry, the work is focused on the silver fixed point cell which is one of the fixed points defined by the International Temperature Scale of 1990 (ITS-90). In this way, the traceability for the practical realization of the kelvinin accordance with the International System of Units (SI) would be provided with the lowest uncertainties. The home-made software has been developed in Lab View language which includes and standardizes the validated measurement procedure. Moreover, the software provides a practical tool for the evaluation of uncertainties according to the “Guide to the expression of uncertainty in measurements". This enables to quantifying the main component contribution on uncertainty budget during the realization of the Silver fixed point cell measurements. Performance and usefulness of the software and evaluation of uncertainty will be discussed in this paper. This work is funded through the European Metrology Programme for Innovation and Research (EMPIR) project “RPT05 - EuraThermal”. EMPIR is jointly funded by the EMPIR participating countries within EURAMET and the European Union.

Five iron-carbon (Fe-C) eutectic fixed-point cells have been constructed between NPL and LNE-Cnam to investigate the robustness and to measure the agreement of their melting temperatures. Each cell was constructed with a different selection of materials sourced by NPL and LNE-Cnam. The measured emfs at the Fe-C fixed-point temperature (1153 °C), compared between cells, agree within around 1.98 µV (90 mK), where the most important contribution to the uncertainty of each measurement is the inhomogeneity associated with the measuring Pt/Pd thermocouple. This demonstrates that these cells are suitable for use as secondary fixed-point cells in contact thermometry but the robustness of the presented cells is not found to be sufficient for maintaining their integrity during repeated cycling procedures.

An intercomparison of the melting temperatures of four Pd–C eutectic fixed-point cells was performed using four Pt/Pd thermocouples. The cells are designed for the calibration of thermocouples and were constructed in the participating laboratories of NPL, LNE, NMIJ and PTB. The measurements were performed in four different high-temperature furnaces but by applying the same measurement procedure. In spite of slightly different cell designs and different material sources, the melting temperatures of three of the four Pd–C cells (NPL, LNE and NMIJ) agreed very well within their expanded uncertainties of k = 2.

Within the framework of the Euramet project 732, LCM/LNE-CNAM has recently proposed a new device to investigate the melting point of indium (156.5985 °C) by the way of an adiabatic calorimetry approach. An apparatus based on a cell-within-cell configuration was developed and experimentally tested. First results highlighted parasitic heat flows due to the geometrical characteristics of the cell, disturbing significantly the isothermal condition within the calorimeter. Such thermal effects were also clearly identified with a specific numerical model developed for this purpose. Considering the remarkable agreement between the model and relevant experiments, an optimization step has been carried out to design a suitable cell geometry. A new enhanced cell was subsequently fabricated and arranged within the calorimeter (indium load of 122.32 g). The purpose of this article is to introduce the thermal behavior of such a highly effective apparatus, while presenting some series of measurements; on the one hand, the melting point of indium under adiabatic conditions is studied, and on the other hand, the so-called continuous heat flow method under isothermal conditions is worked out. The obtained results are discussed and analyzed according to the impurity concentrations into the ingot (sum of individual estimate method).

International audience; Heat flow transducers have been implemented within a thermometric fixed-point cell operated with indium. Then a local heat flow rate was monitored simultaneously with the classical temperature measurement. A specific configuration, so-called cell-within-cell, allowed us to control a melting transition plateau and to observe the behaviour of the heat exchanged during the whole process of the melting transition. Owing to their dynamic character, heat flow measurements prove to be the most appropriate for defining specific boundaries on a given transition plateau, and relevant sensors are found to be suitable tools to be coupled with enhanced temperature measurements. This piece of work is presented in two parts, with the description of the set-up and measurement results in this first paper and their subsequent thermodynamic implications in the following one.

The estimation and control of the thermal power released by the radioactive waste packages are a key parameter in the management of radioactive waste geological repository sites. In the framework of the European project "Metrology for decommissioning nuclear facilities," the French National Agency of Radioactive Waste Management (ANDRA) collaborates with Laboratoire National de Metrologie et D'essais in order to measure the thermal power up to 500 W of typical real size radioactive waste packages (of at least 0.175 m3) with an uncertainty better than 5% by using a measurement method traceable to the international system of units. One of the selected metrological approaches is based on the principles of air flow calorimetry. This paper describes in detail the development of the air flow calorimeter prototype as well as the design of a radioactive waste package simulator used for its calibration. Results obtained from the calibration of the calorimeter and from the determination of thermal powers are presented here with an investigation of the measurement uncertainties.

Laboratoire national de metrologie et d’essais has recently constructed a new device to realize the indium fixed point adiabatically. In parallel, a numerical heat transfer model has been developed as an aid to understanding its thermal behavior. This transient axially symmetric two-dimensional (2D) model simulates the melting process using the apparent specific heat method; the effects of mixing and convection within the liquid phase of indium are not taken into account. The thermal parameters, the nonuniformity of the furnace, and the thermal control of the surroundings were assessed with the aim of reducing parasitic heat exchanges. The results of the modeling are in good agreement with the measurements and clarify the parasitic heat flux observed during the phase transition. This article describes the model and the first results obtained. The model is a helpful tool in evaluating future technical improvements of the enclosure used to realize the indium fixed point.

Temperature measurements in the nuclear field require a high degree of reliability and accuracy. Despite their sheathed form, thermocouples subjected to nuclear radiations undergo changes due to radiation damage and transmutation that lead to significant EMF drift during long-term fuel irradiation experiment. For the purpose of a High Temperature Reactor fuel irradiation to take place in the High Flux Reactor Petten, a dedicated fixed-point cell was jointly developed by LNE-Cnam and JRC-IET. The developed cell to be housed in the irradiation rig was tailor made to quantify the thermocouple drift during the irradiation (about two year duration) and withstand high temperature (in the range 950 °C–1100 °C) in the presence of contaminated helium in a graphite environment. Considering the different levels of temperature achieved in the irradiation facility and the large palette of thermocouple types aimed at surveying the HTR fuel pebble during the qualification test both copper (1084.62 °C) and gold (1064.18 °C) fixed-point materials were considered. The aim of this paper is to first describe the fixed-point mini-cell designed to be embedded in the reactor rig and to discuss the preliminary results achieved during some out of pile tests as much as some robustness tests representative of the reactor scram scenarios.

Thermocouples are often exposed to harsh conditions when used for high-temperature measurements in industry. They suffer commonly from unavoidable drift effects which influence the required process efficiency and control. A self-validation concept for thermocouples to monitor their performance in the temperature range between 1000 C and about 1800 C in oxidizing atmospheres by using integrated miniature fixed-point units of different designs was tested. Two different models of fixed-point crucibles filled with high purity palladium (1553.4 °C) and platinum (1769 °C) have been constructed and assembled with type B thermocouples to be used as traceable references. Furthermore, two innovative self-validation methods by using thick wires of high purity gold (1064.18 °C), nickel (1455 °C), and palladium in multi-bore insulators as fixed-point materials were developed and investigated by assembling them with type B thermocouples. The measurement results obtained have demonstrated the suitability of the integrated fixed-point units to provide long-term confidence in industrial high-temperature measurements within about (2−3) K.

This paper deals with a new European project in which the overall objective is to enhance the availability of facilities in the field of thermal metrology (e.g. high temperature contact thermometry, non-contact thermometry and thermo-physical properties of materials characterisation) in European emerging National Metrology Institutes (NMIs), where access to these types of facilities is currently limited.

In preparation for the new challenges posed by the higher temperature environments which are likely to be encountered in the next generation of nuclear power plants, to maintain the safety and to ensure the long-term reliability of such plants, it is crucial that new temperature sensors and methods for in-situ measurement are investigated and developed. This is the general objective of the first workpackage of the joint research project, ENG08 MetroFission, funded in the framework of the European metrology research program. This paper will review the results obtained in developing and testing new temperature sensors and references during the course of the project. The possible continuation of these activities in the future is discussed.

During irradiation tests at high temperature failure of commercial Inconel 600 sheathed thermocouples is commonly encountered. As instrumentation, in particular thermocouples are considered safety-relevant both for irradiation tests and for commercial reactors, JRC and THERMOCOAX joined forces to solve this issue by performing out-of-pile tests with thermocouples mimicking the environment encountered by high temperature reactor (HTR) in-core instrumentation. The objective was to screen innovative sheathed thermocouples which would consecutively be tested under irradiation. Two such screening tests have been performed in high temperature environment (i.e. temperature in the range 1100–1150◦C) with purposely contaminated helium atmosphere (mainly CH4, CO, CO2, O2impurities) representative for high temperature reactor carburizing atmospheres. The first set of thermocouples embedded in graphite (mainly conventional N type thermocouples and thermocouples with innovative sheaths) was tested in a dedicated furnace at THERMOCOAX lab with helium flushing. The second out-of-pile test at JRC with a partly different set of thermocouples replicated the original test for comparison. Performance indicators such as thermal drift, insulation resistance and loop resistance were monitored. Through these long-term screening tests the effect of several parameters were investigated: niobium sleeves, bending, diameter, sheath composition as well as the chemical environment. SEM examinations were performed to analyze local damage (bending zone, sheath). The present paper describes the two tests, sums up data collected during these tests in terms of thermocouple behavior and describes further instrumentation testing work with fixed point mini cells for qualification under irradiation., JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Management

Parmi les missions devolues au Laboratoire Commun de Metrologie LNE-Cnam figurent la realisation, l’amelioration et la dissemination de l’unite de temperature, le kelvin, sur tout le domaine de temperature. Dans le departement « hautes temperatures et pyrometrie optique » cela concerne la thermometrie de contact au-dessus de 1000 °C et la pyrometrie optique sur tout le domaine de temperature. L’objectif de cet article est de permettre une vue d’ensemble des activites de recherche et d’etalonnage dans ce department ainsi que les projets transverses dans lesquels l’equipe est impliquee au-dela des limites des departements et des poles du laboratoire. L’accent sera mis en particulier sur notre implication dans les projets europeens de recherche concertee (JRP) qui nous engagent sur des durees de plusieurs annees avec nos collegues europeens sur des enjeux importante pour l’industrie et la societe, tels que l’energie, le systeme international d’unites et l’aide a l’industrie.

The eutectic Co-C melting point is a promising system to serve as a thermometric fixed-point in the temperature range above 1084.62 °C (copper freezing point). During the last decade, LNE-Cnam has developed and characterized some fixed-point devices, based on eutectic Co-C alloy, for applications to contact and radiation thermometry. Above 962 °C, the ITS-90 is realized by radiation thermometry by the extrapolation from a Ag, Au or Cu fixed point using the Planck law for radiation. So the only way for assigning a temperature in the scale to a Co-C cell (∼1324 °C) is by radiation thermometry. An indirect method is commonly used to assign a temperature to a high-temperature fixed point (HTFP) cell designed for contact thermometry is to fill a pyrometric cell with the same mixture as the contact thermometry cell. In this case, the temperature assigned to the pyrometric cell is attributed to the contact cell. This paper describes a direct method allowing the determination of the melting temperature realized by a "contact thermometry" Co-C cell by comparison to a "radiation thermometry" Co-C cell whose melting temperature was assigned in accordance to the scale by extrapolation from the Cu point. In addition, the same Co-C cell is studied with a standard Pt/Pd thermocouple.

Une des grandes difficultes dans l’utilisation de thermocouples a haute temperature (au-dela de 1000 °C) est de maitriser leur derive. Soumis a leurs temperatures limites de fonctionnement, les thermocouples ont tendance a deriver, principalement a cause de recombinaisons structurelles inherentes au recuit thermique. Ceux-ci sont egalement exposes a des pollutions depuis leurs milieux de mise en œuvre, ce qui peut conduire a des heterogeneites de composition sur la longueur des thermo-elements, alterant ainsi leurs pouvoirs thermoelectriques. La solution proposee est d’embarquer, voire integrer un point-fixe de temperature de reference au thermocouple, permettant ainsi un etalonnage in situ du capteur lorsque le procede permet de realiser la transition de phase (fusion et/ou congelation) du materiau point-fixe. Cet article presente quelques methodes et techniques en cours de developpement au LNE-Cnam visant a mettre en pratique des methodes d’auto-validation de thermocouples a haute temperature, sous atmospheres neutres et oxydantes.

The European metrology research programme (EMRP) allows funding for metrology-oriented projects in the frame of targeted calls aimed at improving metrology for important contemporary and future needs in different fields such as energy, environment and industry. A joint research project (JRP), called "MetroFission", was selected for funding in the "Energy" call of 2010. This JRP, led by NPL (UK), aims to anticipate and to start addressing the metrological needs of the next generation of nuclear power plants. The need for improving the accuracy and reliability of temperature measurements at temperatures higher than those currently measured in nuclear power plants is dealt with in the first workpackage of the project. This project started in September 2010 and will last for three years. This paper summarizes the activities of the first half of the project and the expected final achievements, which will be essentially oriented towards new temperature references and new devices, adapted to the high temperature range as well as the particularly harsh working conditions.

Raman distributed temperature sensing (DTS) technologies are currently under evaluation by the nuclear and hydraulic industries as it may bring promising alternatives to classical measurement techniques. The reliability of the DTS measurements, as well as the traceability to the temperature standards, must be ensured throughout the entire period of monitoring (typically over a few tens of years). In order to achieve this goal, one key task consists in the verification of the performances claimed by the DTS devices manufacturers. Thus, the metrological performances and characteristics of the DTS devices, such as their limitations and accuracies, as well as the practical aspects of systems implemented on site should be evaluated step by step. This paper describes the dedicated facilities which have been developed at LNE in order to evaluate and to qualify DTS devices for very demanding applications. A first case study performed on one specific DTS device is detailed. A systematic bias has been observed among others on the spatial resolution. The DTS response to a temperature variation step over 1 m (spatial resolution typically claimed by the manufacturers) of sensing optical fibre corresponds indeed to only 90% of the temperature step magnitude, whereas the full DTS response is obtained in fact for 10 m (the practical spatial resolution) of sensing optical fibre solicited by this temperature step variation.

International audience; This second part of the work is devoted to the thermodynamic implications of the results presented in the preceding paper, as heat flow meters (HFMs) were installed within a thermometric fixed-point cell operated with indium. Then, simultaneous measurements of both temperature and heat flow allow us to pinpoint the specific boundaries (solidus and melt-off points) of a given transition plateau. To the best of our knowledge, this work is the first experimental illustration being reported on how to consider a plateau as a specific thermodynamic regime marked with a minimum amount of generated entropy in a metrological fixed-point cell. As a result, a significant relationship linking the boundaries of the plateau and the melting temperature of the material studied is presented. In order to obtain a quantitative understanding of the quality of a given transition process, straightforward thermodynamic considerations allow us to consider both theoretically and experimentally an adimensional parameter defined as the ratio of the entropy generation over the entropy change.

Topic In this paper, an original configuration, named as cell-within-cell, is described together with a specific measurement policy. To this end, concomitant temperature and heat flow assessments are carried out so as to obtain the exhaustive energy monitoring within the thermometric fixed-point cell. Two different melting schemes are investigated so as to consider an optimized control strategy in the near future. 1. General considerations regarding thermometric fixed-point cells The characterization of temperature transition processes associated with numerous pure materials is since a long time ensured by way of high grade Resistor Temperature Detectors, such as classical Pt 25 devices. Such a way to operate enables a well-known and reliable measurement policy as regard various fixed points defining the International Temperature Scale, especially EIT-90 [1]. Sensitivity and low-noise sensor structures are most fundamental prerequisites for best operation together with specific designs regarding the cell, so as to screen out any polluting materials. Moreover, a prominent issue is to be considered as the phase transition is most often associated with an unfortunate marked density variation of the material experimented with. Then, the dimensional parameters of the cell must meet specifications allowing to reduce any untoward temperature gradient highly susceptible to alter the quality of the measurement process.

Accurate high temperature measurement has always been problematic for industry. The vast majority of industrial temperature measurements are performed with thermocouples. The development of any new thermocouple types requires the characterisation of the relationship between thermocouple output and temperature, i.e. the reference function. An important thermocouple for measuring temperatures above about 1500 °C is the so-called Land-Jewell Pt-40%Rh/Pt-20%Rh thermocouple. As the reference function of this thermocouple is not well characterised, this was used as a test thermocouple for a new European distributed facility for characterising thermocouple reference function. The facility is described, and used to generate a demonstrator reference function for the thermocouple. It is found that the demonstrator reference function differs from the de-facto standard reference function of ASTM E1750-09 by several degrees above 1500 °C; a suggested explanation for this is given.