In pressurized water nuclear plants, it is important to know the evolution of the mechanical properties of steel which is subjected to radiation and to temperatures around 300°C. At Areva’s request, we have resumed the elaboration of temperature indicators for future plants.
Why us? Because it was a specialty of the physical metallurgy laboratory, which has since become the « nanostructure and magnetism » laboratory, and also because the know-how has been preserved. We first prepared the case with the help of the person in charge of quality at the institute. In ten years, the norms have not changed, but now all procedures must be written and audited prior to any sample fabrication. The entire process thus becomes more formal.
These temperature indicators come in the form of wires of various metallic alloys. These are eutectic alloys with a precise composition that is adjusted so that the fusion temperature Tf is very well defined: They allow for long-term monitoring of the temperature evolution in the reactor, and their potential melting indicates the maximal temperature that was reached.
We have resumed the elaboration of Pb99.5Zn0.5 (Tf =318°C) and Pb96Ag2Sb2 (Tf =293°C) alloys. Differential scanning calorimetric (DSC) measurements were performed, with our colleagues at INAC/SPrAM, thanks to a very sensitive new instrument. We have, in this way, measured the fusion temperature of the eutectic alloy Pb99.5Zn0.5 with a precision of a few tenths of a degree, and we have refined our knowledge of the Pb96Ag2Sb2 phase diagram..
Maj : 20/02/2014 (983)