Helium migration in nuclear reactors
In nuclear reactors, Helium migration and trapping may lead to swelling, hardening, drastic creep rupture, blistering… To ensure longevity of structural nuclear materials, it is thus of Paramount importance to better understand helium diffusion mechanisms and to describe its distribution below the surface.
Compared to other techniques commonly used for the analysis of nuclear materials such as NRA (Nuclear Reaction Analysis), Proton back scattering or elastic recoil detection, SIMS provides better sensitivity, wide dynamic range and high depth resolution adding to the fact that the impurity profile can be directly obtained without any mathematical treatment.
In a recent study, Helium distribution in implanted monocrystalline and polycrystalline Fe samples was measured, and concentrations at or above 5E18 at/cm3 (~60 ppm) could be detected, confirming the superior depth profiling capabilities and excellent detection limits provided by the IMS 7f/7f-Auto instruments.
Data from H. Lefaix-Jeuland et al, Nuclear Instru. and Methods in Physics Research B (2013).
The detection of CsHe+ molecular ions proves an efficient method to overcome the very high first ionization potential of helium. Concentrations at or above 60 ppm could be measured.