A lot of work was already done on helium atomic diffusion in UO2 samples, but

information was still lacking about the fate of helium in high level damaged UOX

and MOX matrices and more precisely their intrinsic evolutions under alpha self

irradiation in disposal/storage conditions. The present study dealt with helium

atomic diffusion in actinide doped samples versus damage level. The presently

used samples permitted a disposal simulation of about 100 years of a UOX spent

fuel with a 60MWd/kg burn-up or a storage simulation of a MOX spent fuel with a

47.5MWd/kg burn-up. For the first time, nuclear reaction analysis of radioactive

samples was performed in order to obtain diffusion coefficients of helium in

(U,Pu)O2. Samples were implanted with 3He+ and then annealed at 1123K to

1273K. The evolution of the 3He depth profiles was studied by means of the non resonant reaction: 3He(d,p)4He. Using SIMNRA software and Fick’s second law,

thermal diffusion coefficients were measured and compared to the 3He thermal

diffusion coefficients in UO2 found in the literature.

The Use of NRA to Study Thermal Diffusion of Helium in (U,Pu)O2. Y.Pipon,

C.Raepsaet, D.Roudil, H.Khodja: Nuclear Instruments and Methods in Physics

Research B, 2009, 267[12-13], 2250-4