When boron carbide is used as a neutron absorber in nuclear power plants, large quantities of helium are produced. To simulate the gas behaviour, helium implantations were carried out in boron carbide. The samples were then annealed up to 1500 °C in order to observe the influence of temperature and duration of annealing. | Helium behaviour in implanted boron carbide EPJ Nuclear Sci. Technol. 1 16 2015 Nuclear Sciences V. Motte et al. published by EDP Sciences 2015 amp Technologies DOI epjn e2015-50007-5 Available online at http REGULAR ARTICLE Helium behaviour in implanted boron carbide Vianney Motte1 4 Dominique Gosset1 Sandrine Miro2 Sylvie Doriot1 Suzy Surblé3 and Nathalie Moncoffre4 1 CEA Saclay DEN-DANS-DMN-SRMA-LA2M 91191 Gif-sur-Yvette cedex France 2 CEA Saclay DEN-DANS-DMN-SRMP-JANNuS 91191 Gif-sur-Yvette cedex France 3 CEA Saclay DSM-IRAMIS-LEEL 91191 Gif-sur-Yvette cedex France 4 CNRS-IN2P3 IPNL Université Lyon 1 69622 Villeurbanne cedex France Received 30 April 2015 Received in final form 24 September 2015 Accepted 5 November 2015 Published online 16 December 2015 Abstract. When boron carbide is used as a neutron absorber in nuclear power plants large quantities of helium are produced. To simulate the gas behaviour helium implantations were carried out in boron carbide. The samples were then annealed up to 1500 C in order to observe the influence of temperature and duration of annealing. The determination of the helium diffusion coefficient was carried out using the 3He d p 4He nuclear reaction NRA method . From the evolution of the width of implanted 3He helium profiles fluence 1 1015 cm2 3 MeV corresponding to a maximum helium concentration of about 1020 cm3 as a function of annealing temperatures an Arrhenius diagram was plotted and an apparent diffusion coefficient was deduced Ea eV atom . The dynamic of helium clusters was observed by transmission electron microscopy TEM of samples implanted with 1016 cm2 to 3 MeV 4He ions leading to an implanted slab about 1 mm wide with a maximum helium concentration of about 1021 cm3. After annealing at 900 C and 1100 C small 5 20 nm flat oriented bubbles appeared in the grain then at the grain boundaries. At 1500 C due to long- range diffusion intra-granular bubbles were no longer observed helium
