Investigating rapid alpha-decay induced aging of 238PuO2 by Raman Spectroscopy

Abstract

Investigating alpha-decay induced aging in PuO2 is useful in nuclear forensics; helping to determine the time since last calcination. This was previously investigate by monitoring the damage to 240PuO2 over the course of a few years. The rate of alpha-decay induced aging has long been assumed to scale only with the decay rate of other isotopes without direct verification. This article reports the first alpha-decay aging study of 238PuO2 by Raman spectroscopy. Contrary to the expected 10 days for 238PuO2 to reach steady state based on 240PuO2 studies, the alpha aging curve reached an approximate steady state ∼24–30 h after laser annealing. While the cause of the order of magnitude decrease is unknown, it is speculated that dynamic annealing could contribute to the differences in rate of induced aging. The Raman spectra of annealed and aged 238PuO2 matched the expected features in 239PuO2 and 240PuO2 spectra; showing no formation of new stable chemical species in the material such as secondary Pu oxide phases (e.g., Pu4O9). Results indicate that 238Pu could be leveraged for rapid alpha-decay aging studies to characterize alpha-decay induced features and better understand matrix temperatures and the annealing of Frankel pair defects.