Investigation of self-validating thermocouples with integrated fixed-point units

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

Long term out-of-pile thermocouple tests in conditions representative for nuclear gas-cooled high temperature reactors

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 forcesto 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 suchscreening tests have been performed in high temperature environment (i.e. temperature in the range 1100–1150◦C) with purposely contaminated heliumatmosphere (mainly CH4, CO, CO2, O2impurities) representative for high temperature reactor carburizing atmospheres. The first set of thermocouplesembedded in graphite (mainly conventional N type thermocouples and thermocouples with innovative sheaths) was tested in a dedicated furnace atTHERMOCOAX lab with helium flushing. The second out-of-pile test at JRC with a partly different set of thermocouples replicated the original test forcomparison.Performance indicators such as thermal drift, insulation resistance and loop resistance were monitored. Through these long-term screening teststhe effect of several parameters were investigated: niobium sleeves, bending, diameter, sheath composition as well as the chemical environment. SEMexaminations 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 instru-mentation testing work with fixed point mini cells for qualification under irradiation.JRC.E.2-Safety of Irradiated Nuclear Material

Long term out-of-pile thermocouple tests in conditions representative for nuclear gas-cooled high temperature reactors

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 Managemen

Long Term out-of-pile Thermocouple Tests in Conditions Representative for Nuclear Gas-cooled High Temperature Reactors

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 the 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 - 11500C) with purposely contaminated helium atmosphere (mainly CH4, CO, CO2, O2 impurities) 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 in Petten with a partly different set of thermocouples replicated the original test for comparison. Performance indicators such as thermocouples thermal drift, insulation resistance measurements and loop resistance measurements were monitored. Through these long-term screening tests several effects 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 experimentations, sums up data collected during these tests in terms of thermocouple behavior and describes further work, in particular to select suitable thermocouples equipped with fixed point mini cells for qualification under irradiation.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen

Home-made software development for optimizing the uncertainty evaluation of silver fixed point cell used for practical realization of ITS-90

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

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.JRC.G.I.3-Nuclear Fuel Safet

Metrology for decommissioning nuclear facilities: partial outcomes of joint research project within the European Metrology Research Program

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.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard