Abstract
Safe management of high level nuclear waste is a worldwide significant issue for which vitrification has been selected by many countries. There exists a crucial need for improving our understanding of the ageing of the glass under irradiation. While external irradiation by ions provides a rapid simulation of damage induced by alpha decays, short lived actinide doping is more representative of the reality. Here, we report radiological NMR experiments to compare the damage in International Simplified Glass (ISG) when irradiated by these two methods. In the 0.1 mole percent 244Cm doped glass, accumulation of high alpha decay only shows small modifications of the local structure, in sharp contrast to heavy ion irradiation. These results reveal the ability of the alpha particle to partially repair the damage generated by the heavy recoil nuclei highlighting the radiation resistance of nuclear glass and the difficulty to accurately simulate its behaviour by single ion beam irradiations.
Highlights
Borosilicate glasses, besides other numerous applications, have been recognized as valuable materials for the conditioning of nuclear wastes[1]
In glasses as well as in SiC, ionization induced thermal spike and defect recovery as a result has been proposed to be the responsible mechanism[12,13]. These results suggest that such a defect recovery process should be effective in actinide bearing glasses due to irradiation of the glass by alpha particle (AP) and RN
The International Simplified Glass (ISG) has been chosen for this study as it is considered by the international community as a good surrogate of nuclear borosilicate glasses developed worldwide[3]
Summary
The first MAS NMR experiments on radioactive glasses, close to the reality and doped with 244Cm have revealed similar transformations as identified when samples are subjected to external irradiation by heavy ions, but to a much lower extent This clearly demonstrates a competitive effect occurring between the recoil nucleus and the alpha particle emitted during alpha decay. The partial damage repair occurs due to alpha particle irradiation of the recoil nucleus pre-damaged regions. Deeper investigations of such coupled effects will be of great importance in the near future to assess the appropriateness of accelerated experiments to simulate the ageing of nuclear materials under working conditions
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