Effects of deposited nuclear and electronic energy on the hardness of R7T7-type containment glass S. Peuget a, * , P.-Y. Noe ¨l a , J.-L. Loubet b , S. Pavan b , P. Nivet a , A. Chenet a a Commissariat a ` l’E ´ nergie Atomique, CEA Marcoule, DEN/DTCD/SECM/LMPA, Ba ˆtiment 166, BP 17171, F-30207 Bagnols-sur-Ce `ze Cedex, France b Laboratoire de Tribologie et Dynamique des Syste `mes, UMR CNRS 5513, E ´ cole Centrale de Lyon 36, avenue Guy de Collongue, 69134 E ´ cully Cedex, France Received 6 October 2005; received in revised form 19 December 2005 Available online 14 February 2006 Abstract The effects of elastic and inelastic interactions induced by cumulative alpha decay on the hardness of R7T7-type nuclear containment glass were investigated on actinide-doped glass specimens and by external irradiation of inactive glass by light and heavy ions. Vickers microindentation and nanoindentation hardness measurements showed that in the deposited energy range investigated (below 3 · 10 22 keV/cm 3 ) inelastic effects have no influence on the plastic response of the glass. Conversely, identical hardness variations versus the nuclear energy deposited in the material were observed on curium-doped glass and on glass irradiated by ion bombardment. The observed hardness variation stabilized after the deposited energy reached about 3 · 10 20 keV nucl /cm 3 . These findings indicate that the change in the plastic response of the glass is a consequence of ballistic effects. Ó 2006 Elsevier B.V. All rights reserved. PACS: 28.41.Kw; 61.43.Fs; 61.80.Jh; 61.82.Ms Keywords: Glass; Irradiation effect; Hardness; Nanoindentation; Deposited energy 1. Introduction The ultimate wasteforms produced by the French nuclear industry are immobilized in a borosilicate glass matrix. Investigating the effects of radiation on the macro- scopic properties of the glass is crucial for ensuring its con- tainment performance after disposal. Numerous published studies have been carried out to assess the impact of radi- ation arising from beta and alpha decay on the properties of nuclear glasses [1–3]. They have revealed variations in the macroscopic properties due to the accumulation of alpha decay within the glass matrix, for example slight swelling or densification depending on the chemical com- position of the nuclear glass. Variations are also observed in the mechanical properties: the glass hardness and mod- ulus of elasticity first diminish by up to 30% depending on the alpha decay dose, then stabilize above a dose of 2 · 10 18 a/g. Similarly, the fracture toughness of the glass increases by about 60% before stabilizing. Validating nuclear glass behavior after disposal requires an understanding of the mechanisms responsible for the changes in its mechanical properties. It is of particular importance to identify the effects of electronic and nuclear processes on these variations. This article examines the effects of elastic and inelastic interactions on the hardness variations induced by cumula- tive alpha decay in R7T7-type nuclear waste containment glass. Alpha decay damage was simulated by two techniques. The first consists in doping glass specimens with a short-lived actinide making it possible over a reasonable time period (a few years) to accumulate the alpha decay equivalent of sev- eral thousand years in the containment glass. The second 0168-583X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.12.053 * Corresponding author. Tel.: +33 466 796529; fax: +33 466 797708. E-mail address: sylvain.peuget@cea.fr (S. Peuget). www.elsevier.com/locate/nimb Nuclear Instruments and Methods in Physics Research B 246 (2006) 379–386 NIM B Beam Interactions with Materials & Atoms