A new thermo-desorption laser-heating setup for studying noble gas diffusion and release from materials at high temperatures

Abstract

A new heating and gas treatment line for Thermo-Desorption Spectrometry (TDS) of noble gases (He, Ne, Ar, Kr and Xe) is presented. It was built with the primary objective to offer advanced temperature controls and capabilities while working in a cold-environment. By choosing a high-power continuous wave laser as an heating source, and using a Proportional-Integral-Derivative (PID) controller system, noble gases TDS can now be performed with fast and highly steady heating ramps (e.g. less than 1°C deviation from setpoint for ≤ 1°C.s -1 ramps). Sample temperature over 2000°C can also routinely be reached, with limited heating of the sample support and the sample chamber, offering the possibility to have several samples awaiting in the ultra-high vacuum chamber. We also present development efforts made to increase temperature homogeneity of the heated sample while limiting contacts with the sample holder.Recent results acquired with this TDS setup on krypton thermal diffusion in uranium dioxide (UO 2 ) as a function of O 2 additions are also presented as an application example.

Diffusion of Xe and Kr implanted at low concentrations in UO2 as a function of temperature – An experimental study

“…The recent study of Horlait et al [26] describes a device that enables O 2 addition into the heating chamber (where the UO 2 pellet stands). The first results show that a slight increase of x in UO 2+x from a starting supposedly perfectly stoichiometric UO 2 could drastically change the diffusion coefficient of Kr (e.g.…”

“…Experimental data on fission gas migration rely on gas release measurements mainly in postirradiation annealing. Xenon and krypton thermal diffusion in UO 2 depends on (i) the stoichiometry [20], [23]- [26]: it increases with stoichiometry for >2.021 values and decreases when below 1.997 and (ii) the burn-up [27]- [29]: it decreases from 10 22 fission/m 3 to reach a saturated state at 10 24 fission/m 3 . The apparent decrease of the diffusion coefficient with the burn-up has been explained by a trapping effect [27].…”