Modeling and Simulation of Radioactive Nanomaterials of Pb-U, Pb-Th, and Pb-Co in Water-Filled Containers for Nuclear Security Applications
Not provided.
Nuclear Science & Technology↗
SEARCH · Engineering Papers
Results for “Pb-U”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
U-Th-Pb systematics in three Apollo 14 basalts and the problem of initial Pb in lunar rocks.
The isotopic composition of Pb and the elemental concentration of U, Th and Pb were measured on 'total' rock samples 14053, 14073 and 14310 and on mineral separates of 14310 and 14053. These are the first Pb-U isochrons obtained for lunar basalts and indicate a reasonable solution to the previous discrepancy between the different methods of 'absolute' age determination. The resulting U-Pb isochron ages are compatible with the Rb-Sr and K-Ar ages on the same rocks. However, it is not possible to establish a precise time of 'crystallization' from the Pb-U data because of the small angle of intersection between the linear arrays and the concordia curve. These data show that total rock model ages do not in general yield crystallization ages. The data on 14310 and 14053 show that these rocks were formed containing a highly radiogenic initial lead which accounts for the excessively high total rock model ages by the U-Th-Pb method. The data prove that at the time of extrusion of some basalts, unsupported lead with extremely high Pb-207/Pb-206 ratios was added to the lunar surface.
Tera, F.↗
Isotopic evidence for a terminal lunar cataclysm
Most highland total rock samples define a single U-Pb isochron which corresponds to a metamorphism age of about 3.9 aeons. This age is also obtained for internal U-Pb isochrons for some of these samples. The data on 18 rock samples range from concordant samples with U-238/Pb-206 ratio of about 1.2 to discordant ones with U-238/Pb-206 ratio of about 0.02. This feature, coupled with a correlated pattern of U-238/Pb-204 ratios, indicates that Pb was extensively mobilized at about 3.9 aeons. The observed Pb-U fractionation is essentially due to Pb volatilization during the metamorphic events. Volatile Pb transport is not accompanied by similar effects in Rb and must therefore be attributed to a specific process. Rb-Sr internal isochrons for the same rocks determine distinct metamorphic events in the interval 3.85 to 4.00 aeons. It is concluded that highland samples from widely separated areas bear the imprint of an event or series of events in a narrow time interval which can be identified with a cataclysmic impacting rate of the moon at about 3.9 aeons, although diffrentiation by internal magma generation cannot be excluded.
Tera, F.↗
Materials Data on UPb by Materials Project
UPb is Tetraauricupride structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. U is bonded in a distorted body-centered cubic geometry to eight equivalent Pb atoms. All U–Pb bond lengths are 3.35 Å. Pb is bonded in a distorted body-centered cubic geometry to eight equivalent U atoms.
36 MATERIALS SCIENCE↗
Materials Data on UPb by Materials Project
UPb crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. U is bonded in a 12-coordinate geometry to eight equivalent Pb atoms. There are four shorter (3.24 Å) and four longer (3.46 Å) U–Pb bond lengths. Pb is bonded in a 12-coordinate geometry to eight equivalent U atoms.
36 MATERIALS SCIENCE↗