Los Alamos Women in Science
Northern Chapter of the New Mexico Network for
Women in Science and Engineering
LUNCHTIME TALK SERIES

Thursday, December 9, 1999
11:30 am - 1:30 pm, Otowi cafeteria side room C, LANL

TALK at 12:00:
Robi Mulford, NMT-15, LANL*
"A Survey of Plutonium Characteristics as a Function of Age:
The ARIES Sampling Program"
*work done in collaboration with W. Brown and J. Wendelberger

A survey of a wide variety of Pu samples from a large number of retired nuclear weapons is providing a substantive statistical foundation for description of characteristics of Pu as a function of age. A statistically significant body of data from these very old units may provide a basis for prediction of incipient problems in the stockpile.

The ARIES line is a system that disassembles old pits and converts the weapons-grade Pu to oxide as feed material for commercially usable MOX fuel, thus providing an elegant means for reducing the nuclear stockpile. The large number and variety of units to be dismantled by the ARIES line provide the opportunity to sample several plutonium alloys with a broad range of ages. Small samples are taken, examined, and returned to the ARIES line.

The plutonium metal ageing may have several effects on the metal. Evidence for these effects is being sought. Radioactive decay disrupts the metal lattice, and may result in annealing or in phase changes. Phase changes may also be caused by migration of impurities during annealing. Phase changes may be nucleated by interstitial atoms and decay products incorporated into the metal matrix. Void swelling is a common radiation damage effect, resulting from gaseous products of decay that are trapped within the metal. Thus the helium (daughter product) produced during the alpha decay of plutonium may reduce the density of the metal. The location of helium in the metal, and the mechanical effects of this helium can be compared with several theoretical damage models. Ageing effects are examined by a variety of techniques.

Statistical analysis of the data provides a template for evaluation of subsequent samples, and prediction of the condition of plutonium metal of all ages. The problem of absent baseline data for some plutonium parts manufactured in the past can be addressed by this large database, both by using the properties of newer units as a baseline for older, and by permitting justifiable extrapolation of data to the time of manufacture. Currently, insufficiently detailed manufacturing records result in the absence of a baseline from which age-induced changes can be measured. This extrapolation will provide a foundation for evaluation of aging effects observed in plutonium by a large number of other workers.

--> Nonmembers Welcome! <-- 

Sideroom C is reserved from 11:30 to 1:30 for people who like to eat earlier or later, and informal discussion. You are welcome to come for just the talk at noon, and questions are encouraged!

For driving directions to Otowi Cafeteria (TA-3, building 261) at LANL, see: http://www.lanl.gov/tools/maps
(direct link to map showing the Otowi Building: http://nis-www.lanl.gov/cgi-bin/wthi?ta=3&bldg=261).

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LAWIS Lunch-Time Talk Organizer: Huyen Dinh, dinh@lanl.gov, 665-0737
LAWIS home page: http://home.lanl.gov/lawis
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