Timescale of natural annealing in radioactive minerals affects retardation of radiation-damage-induced leaching

The paper concerns natural annealing and radiation-damage-induced leaching in solidified nuclear materials. Results are presented of radioisotope measurements on ancient uranium- and thorium-rich materials, which indicate that 'self-annealing' strikingly reduces the rate of dissolution. An annealing time of 15 k yr is estimated. The results also suggest a localized submicroscopic loss of order. Finally the data infers that minerals in which such annealing occurs could be suitable for nuclear waste-storage media. (U.K.)