Abstract
The effects of alpha irradiation on the rare-earth silicate, Ca 2Nd 8(SiO 4) 6O 2, was investigated by X-ray diffraction. X-ray absorption near-edge spectroscopy (XANES), and extended X-ray fine structure (EXAFS) techniques. Irradiation with alpha particles emitted isotropically from a 238PuO 2 source to a cumulative dose of 2.25 × 10 21 alphas/ m 2 (0.36 dpa) produced measurable anisotropic lattice expansions, with no tendency toward the amorphization that was previously reported due to self-radiation damage in Cm-doped samples at similar displacement-damage (0.25 dpa) levels. The unit-cell volume expanded exponentially with dose to a value corresponding to 2.5% volume expansion at saturation. The fluorescence XANES data of irradiated and unirradiated surfaces indicate a rearrangement of the near-neighbor ions about Nd. The EXAFS results indicate an irradiation-induced increase in structural disorder that becomes readily apparent at distances of several coordination spheres away from Nd.
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