Identifying and quantifying actinide radiation damage in ZrSiO4 minerals and ceramics with nuclear magnetic resonance

This paper discusses how high-resolution solid-state nuclear magnetic resonance (NMR) can be used to characterize and quantify radiation damage in natural minerals and ceramic nuclear waste forms that contain actinides. The scientific goal is to identify the nature of the amorphous component of the radiation damaged material through similar approaches to those where NMR has been used to study glasses and amorphous materials. NMR also allows the amount of amorphous material to be quantified as an atomic number fraction of the total. This is in contrast to traditional methods that express the damaged amorphous component as volume fractions of the total. Very old mineral samples of ZrSiO4 (zircon) containing 238U and 232Th with varying alpha radiation doses can be used to provide samples with differing levels of radiation damage. Radiation damage due to the emission of an alpha particle by an actinide nucleus is believed to occur through two distinct processes. The alpha particle itself (4.5 ? 5.5 MeV), will mainly cause ionizations during its flight through a material, it is also thought to cause a few hundred atomic displacements (Frenkel defects) as it is stopped by collision with atomic nuclei. The recoil of the heavy actinide nucleus (70-100 keV) is believed to cause the majority of the localized structural damage (amorphization) as it creates a cascade of collisions with surrounding ions. The extent and nature of this ''displacement cascade'' is the subject of extensive modeling by both ballistic and increasingly molecular dynamics methods. There is a profound need for experimental data to distinguish between these models