Determination of natural radioactivity in Wilcox lignite (Eocene), eastern Texas

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:45184

Bartow, P M; Ledger, E B ^[1]

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1. Stephen F. Austin State Univ., Nacogdoches, TX (United States)

Natural radioactivity was measured in two series of Wilcox (Eocene) lignites from Rusk and Panola Counties, Texas. Natural radioactivity consists mostly of {sup 235}U, {sup 238}U, {sup 232}Th decay chain isotopes, and {sup 40}K. Uranium isotopes occur in lignite in two ways: in heavy mineral crystals carried by streams and deposited with the lignite as it forms, and trapped in the complex molecules of organic matter in the lignite. Thorium occurs only in the heavy minerals in a known concentration ratio with uranium. Potassium occurs in association with the plant remains of the lignite. A total of 31 samples were analyzed by gamma-ray spectrophotometry for uranium, thorium, and potassium. Uranium averages 1.18 ppm U and ranges from 0.91 to 1.37 ppm U. Thorium averages 7.32 ppm Th and ranges from 6.30 to 8.87 ppm Th. Potassium averages 0.55 weight percent K and ranges from 0.51 to 0.61 weight percent K. The Th/U ratio of 5.5 is well within the range of common heavy minerals like zircon, monazite, and allanite, showing that there is little organic uranium present in these lignites. If organic uranium were present, Th/U ratio would be less than about 3 to 4. Wilcox lignite is lower in uranium than the average United States lignite, and strikingly lower than lignite from South Texas where the sediment enclosing the lignite is a low-level source of uranium. In contrast, East Texas uranium-rich sediments are some 80 mi south of the Wilcox lignites.

• OSTI ID: 45184
• Report Number(s): CONF-941065--; CNN: Grant A9510 1140 30
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
COAL DEPOSITS
EOCENE EPOCH
LIGNITE
NATURAL RADIOACTIVITY
POTASSIUM
TEXAS
THORIUM
URANIUM