Ge(Li) spectrometric measurements of isotopic uranium ratios in soils treated with apatite-derived fertilizers

Conference · Wed Jan 01 04:00:00 EST 1975

OSTI ID:4164365

Lindeken, C L; Coles, D G; Meadows, J W

Soil samples collected in an agricultural region of the Sacramento-San Joaquin Delta in central California contained levels of uranium as high as 17 ppm. Isotopic uranium analysis, determined by mass spectrometry, showed $sup 235$U/ $sup 238$U ratios of 7.1 x 10$sup -3$, typical of natural uranium. However, the $sup 238$U content inferred from gamma counting of the $sup 226$Ra daughters disclosed marked disequilibrium in the $sup 238$U decay series. The elevated levels of uranium are attributed to its presence in ammonium phosphate fertilizer produced from apatite [CaF$sub 2$Ca$sub 3$(PO$sub 4$$)$$sub 2$]. The $sup 238$U daughter disequilibrium is due to removal of $sup 226$Ra by coprecipitation with CaSO$sub 4$ during conversion of the raw material to phosphoric acid with sulphuric acid. A more direct method for $sup 238$U measurement based on detection of the 63-keV transition gamma of $sup 234$Th and using Ge(Li) gamma spectrometry is described. This method is independent of $sup 226$Ra daughters and can detect $sup 238$U down to about 0.1 $mu$g/g in soils. A comparison with $sup 238$U measurements using mass spectrometry shows agreement within +- 10 percent. (auth)

• Research Organization: Univ. of California, Livermore
• NSA Number: NSA-33-007323
• OSTI ID: 4164365
• Country of Publication: IAEA
• Language: English

Related Subjects

*FERTILIZERS-- RADIATION MONITORING
*RADIUM 226-- RADIATION MONITORING
*SOILS-- RADIATION MONITORING
*URANIUM 235-- RADIATION MONITORING
*URANIUM 238-- RADIATION MONITORING
510101* --Environmental Sciences
Terrestrial--Basic Studies- -Radiometric Techniques
CALIFORNIA
DAUGHTER PRODUCTS
GAMMA SPECTROMETERS
ISOTOPE RATIO
MASS SPECTROMETERS
N44300 --Environmental & Earth Sciences--Radioactivity Monitoring & Transport
N44420* --Environmental & Earth Sciences--Radiometric Techniques--Soil
THORIUM 234