In support of Stockpile Stewardship activities, accelerated aging tests on a plutonium alloy enriched with 7.3 atomic percentage of 238 Pu is underway using dilatometry at 35, 50, and 65°C and immersion density measurements of material stored at 50°C. Changes in density are expected from radiation damage in the lattice and helium in-growth. After twenty-five equivalent years of aging, the dilatometry data shows that the alloys at 35°C have expanded in volume by 0.11% to 0.12% and have started to exhibit a near linear expansion behavior primarily caused by the helium accumulation. The average He-tovacancy ratio from tested specimens was determined to be around 2.3. The model for the lattice damage and helium in-growth accurately represents the volume swelling at 35°C.The density converted from the dilatometry corresponds well to the decreasing density trend of reference plutonium alloys as a function of time.
The effect of dissolved oxygen shock on the stability of recombinant Escherichia coli cells containing plasmid pKN401 was investigated. The recombinant cells were stable in control batch experiments in media with and without ampicillin. However, these recombinant cells were highly unstable under conditions where a dissolved oxygen shock was induced. The results have implications for design of aerated reactors for recombinant cells.
(ReceivedWe present dimensional and density changes in an aging plutonium alloy enriched with 7.3 at. % of 238 Pu and reference alloys of various ages. After 45 equivalent years of aging, the enriched alloys at 35°C have swelled in volume by 0.14 to 0.16 % and now exhibit a near linear volume 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.
In support of Stockpile Stewardship activities, accelerated aging tests on a plutonium alloy enriched with 7.3 atomic percentage of 238 Pu is underway using dilatometry at 35, 50, and 65°C and immersion density measurements of material stored at 50°C. Changes in density are expected from radiation damage in the lattice and helium in-growth. After twenty-five equivalent years of aging, the dilatometry data shows that the alloys at 35°C have expanded in volume by 0.11% to 0.12% and have started to exhibit a near linear expansion behavior primarily caused by the helium accumulation. The average He-tovacancy ratio from tested specimens was determined to be around 2.3. The model for the lattice damage and helium in-growth accurately represents the volume swelling at 35°C.The density converted from the dilatometry corresponds well to the decreasing density trend of reference plutonium alloys as a function of time.
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