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Northern Chapter of the New Mexico Network for Women in Science and Engineering LUNCHTIME TALK SERIES https://archive.nmnwse.org/lawis/lunchtalks sponsored by the Synergy Center , the Zocher Corporation and the Bradbury Science Museum Talk at 12:00, Tuesday, July 12, 2005 Bldg 1, Los Alamos Research Park Synergy Center Conference Room, 3rd flr |
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Roberta N. Mulford, NMT-15, LANL
Radiation Damage and Aging in Plutonium Metal |
The density of plutonium metal decreases as a function of time, over 30 years or more. Variations in the rate of change have been
observed. A decrease in the density is expected with increasing age, as radiation damage resulting from the decay of the plutonium is
complemented by the buildup of helium within the lattice, a product of that decay. Densities of a set of plutonium samples cut from
retired pits exhibit decreases in density from the known manufactured density. Linear fits to the densities of the group of samples of
various ages give two rates. Samples between about 20 and about 35 years of age exhibit a rate of about -0.005 %/annum, which is
fairly consistent with independent measurements of the emergence of helium bubbles within the metal, and with theoretical predictions
of the rate of helium bubble formation and growth. The rate of density decrease changes with age, and the density appears to decrease
more rapidly for samples older than about 36 years. Older samples exhibit a rate of change in density of -0.06%/annnum. Each sample,
measured repeatedly over two or more years shows a rate of change nearly commensurate with the rate determined by comparing
different samples with various ages. Some samples are not consistent with the global rate, and some appear to increase in density.
Possible systematic errors have been suggested to explain the observed decreases in density and the various rates of change observed
among the individual samples. The possible magnitudes of these systematic errors are discussed, and shown to be too small to account
for the observed changes.
(Work done with E. Ann Trujillo and Wendel Brown, LA-UR-04-3097.)
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Members and Nonmembers Welcome! Open to the Public |  |
LunchTalks webpage: https://archive.nmnwse.org/lawis/lunchtalks
