[en] We present dimensional and density changes in an aging plutonium alloy enriched with 7.3 at.% of ²³⁸Pu and reference alloys of various ages. After 45 equivalent years of aging, the enriched alloys at 35 deg. C have swelled in length by 0.048-0.052% and now exhibit a near linear dimensional increase, without void swelling. Based on X-ray diffraction measurements, the lattice expansion by self-irradiation appears to be the primary cause for dimensional changes during the initial 2-3 years of aging. Following the initial transient, the density change is primarily cause by a constant helium in-growth rate as a result of α-particle decay