G. Failleau

Investigation of Pd–C cells to improve thermocouple calibration

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.

Fe?C eutectic fixed-point cells for contact thermometry: an investigation and comparison

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??V (~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.

New temperature references and sensors for the next generation of nuclear power plants

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.

A pan-European investigation of the Pt-40%Rh/Pt-20%Rh (Land–Jewell) thermocouple reference function

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 characterization 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. This was used as a test thermocouple for a new European distributed facility for characterizing 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.

New fixed-point mini-cell to investigate thermocouple drift in a high-temperature environment under neutron irradiation

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.

A new technique for direct traceability of contact thermometry Co-C eutectic cells to the ITS-90

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 b...