Evolving density and static mechanical properties in plutonium from self-irradiation

Plutonium, because of its self-irradiation by alpha decay, ages by means of lattice damage and helium ingrowth. These integrated aging effects result in microstructural and physical property changes. Because these effects would normally require decades to measure, studies are underway to assess the effects of extended aging on the physical properties of plutonium alloys by incorporating roughly 7.5 wt% of highly specific activity isotope Pu-238 into the Pu-239 metal to accelerate the aging process. This paper presents updated results of self-irradiation effects on Pu-238-enriched alloys measured by immersion density, dilatometry, and tensile tests. After nearly 90 equivalent years of aging, both the immersion density and dilatometry show that the enriched alloys continue to decreased in density by similar to 0.002% per year, without void swelling. Quasi-static tensile measurements show that the aging process increases the strength of plutonium alloys. (c) 2008 Elsevier B.V. All rights reserved.