WP 3: Thermophysical Properties of advanced materials

Background

As part of the process of developing new fission reactors, a fundamental understanding of the thermal behaviour of the used materials at high temperature (structural and refractory materials, as well as irradiated and nuclear materials) must be established, in particular to define the critical performance limitations of these materials and possible design alternatives. It is thus necessary to accurately determine the thermal properties of the materials concerned under temperature conditions close to those of in-pile operation and accident conditions (up to several thousand °C). The thermal characterisation of irradiated materials and nuclear fuels, which must be carried out under safe manipulation conditions (glove boxes fitted with remote manipulators), are performed up to very high temperatures, in some cases exceeding 2000 °C, by well experienced staff of nuclear research institutes (JRC (ITU), CEA).


State of the art

The measurement methods used by these research institutes to study thermal quantities require reference materials certified up to 2000 °C as a minimum, either for the validation of absolute measurement methods (drop calorimetry, laser flash method…) or for calibration of comparative ones (e.g. differential scanning calorimetry or differential dilatometry).

Unfortunately, for many thermal properties, there is currently no possibility of ensuring the traceability of these measurements to the SI above 800 °C, due to the temperature range limitation of the metrological reference facilities currently available in European NMIs and the lack of suitable reference materials.


Aims of the work package

The aim of this WP is therefore to implement a European metrological infrastructure in the field of thermophysical properties in order to provide reliable and traceable high temperature measurements for materials having thermal properties similar to those used in fission reactors. The availability of accurate facilities and reference materials will improve the traceability of the nuclear research laboratories measurements.

The main scientific and technological objectives are to:

Develop and improve accurate reference facilities and methods for the measurement of thermal properties of homogeneous and layered solid materials up to 2000 °C and molten salt coolants up to 1000 °C.

Perform a feasibility study of "transfer reference materials" for high temperature thermal properties measurements (up to 2000 °C where possible) .


Major facilities/equipment

This WP makes use of the following facilities which exist already:

  • Pushrod dilatometers and differential scanning calorimeters at NPL, PTB and LNE.
  • Drop calorimeters, differential dilatometer and laser-flash facility, which are currently dedicated at JRC (ITU) to the study of materials related to nuclear power plant technology (non-active materials, materials containing only natural uranium or thorium, active materials).

    • Moreover, in this WP reference metrological facilities will be developed or improved by NPL, LNE and PTB to enable measurements of thermal diffusivity, specific heat and emissivity up to 2000 °C (1500 °C in the case of specific heat). These reference facilities will only be funded within the framework of national research programmes. They will ensure the traceability of the thermo-physical properties measurements performed by JRC (ITU), which is deeply involved in research to the benefit of the nuclear industry.


    Scientific tasks

    3.1 Implementation of reference metrological setups and methods for the measurement of thermal properties of advanced materials at temperatures up to 2000 °C (LNE, NPL, JRC (ITU), PTB)

    3.2 Feasibility study of "transfer reference materials" for high temperature thermal properties measurements (LNE, JRC (ITU), PTB, NPL)