Irradiation-induced heterogeneous nucleation in uranium dioxide

Atomic scale mechanisms for the amorphisation of irradiated graphite

“…This procedure consists in impulsing cascades one after the other in the same simulation box. This gives to interesting results about the clustering of point defects such as those obtained in UO 2 [60]. However, displacement cascades simulations are extremely time consuming.…”

A study of helium mobility in polycrystalline uranium dioxide

“…A set of experiments has been carried out in order to characterise helium mobility mainly in ion implanted uranium dioxide polycrystalline samples at a fluence of 10 16 ions cm À2 and in the temperature range 700°C to 1100°C. Helium distribution and release kinetics were monitored using three different implementations of the 3 He (d, a) p nuclear reaction in order to determine the changes in space and time of 3 He concentrations.…”

“…The method involves analysing the a particle energy spectrum, usually with a 625 keV deuteron beam approximately 1 nA in intensity and covering an area of roughly 1 mm 2 . This however requires detecting in coincidence both reaction products as described by Sauvage et al [11] in order to eliminate particles produced mainly as a result of the 16 O(d,p) and 16 O(d,a) reactions.…”

“…13 is controlled not by the elemental concentration but by the level of damage the material is subjected to. The actual mechanism is akin to heterogeneous nucleation and results from the formation of vacancy clusters in the core of damage cascades which act as sinks for insoluble elements [16,17]. Such bubble nucleation will tend to hinder helium movement at temperatures below 1000°C.…”

“…Notwithstanding Comparison of helium diffusion coefficients in uranium dioxide. Study [7] was carried out at 3 Â 10 15 and 3 Â 10 16 He cm À2 for the low and high dose results respectively. this, it is interesting to note that activation enthalpies and preexponential factors are similar in both studies.…”