230Th-234U Age-Dating Uranium by Mass Spectrometry

Williams, R W ; Gaffney, A M

关键词: AGE ESTIMATION;    DILUTION;    DISSOLUTION;    HYDROFLUORIC ACID;    ISOTOPE RATIO;    LAWRENCE LIVERMORE NATIONAL LABORATORY;    MASS SPECTROSCOPY;    NITRIC ACID;    PURIFICATION;    QUARTZ;    RESINS;    THORIUM;    THORIUM ISOTOPES;    URANIUM;    URANIUM 228;    URANIUM ISOTOPES;    URANIUM OXIDES;    WATER;   

DOI  :  10.2172/1044939
RP-ID  :  LLNL-TR-551011
PID  :  OSTI ID: 1044939
Others  :  TRN: US1203580

学科分类：化学（综合）

美国|英语

来源: SciTech Connect

【 摘 要 】

This is the standard operating procedure used by the Isotope Ratio Mass Spectrometry Group of the Chemical Sciences Division at LLNL for the preparation of a sample of uranium oxide or uranium metal for {sup 230}Th-{sup 234}U age-dating. The method described here includes the dissolution of a sample of uranium oxide or uranium metal, preparation of a secondary dilution, spiking of separate aliquots for uranium and thorium isotope dilution measurements, and purification of uranium and thorium aliquots for mass spectrometry. This SOP may be applied to uranium samples of unknown purity as in a nuclear forensic investigation, and also to well-characterized samples such as, for example, U{sub 3}O{sub 8} and U-metal certified reference materials. The sample of uranium is transferred to a quartz or PFA vial, concentrated nitric acid is added and the sample is heated on a hotplate at approximately 100 C for several hours until it dissolves. The sample solution is diluted with water to make the solution approximately 4 M HNO{sub 3} and hydrofluoric acid is added to make it 0.05 M HF. A secondary dilution of the primary uranium solution is prepared. Separate aliquots for uranium and thorium isotope dilution measurements are taken and spiked with {sup 233}U and {sup 229}Th, respectively. The spiked aliquot for uranium isotope dilution analysis is purified using EiChrom UTEVA resin. The spiked aliquot for thorium isotope dilution analysis is purified by, first, a 1.8 mL AG1x8 resin bed in 9 M HCl on which U adsorbs and Th passes through; second, adsorbing Th on a 1 mL AG1x8 resin bed in 8 M HNO{sub 3} and then eluting it with 9 M HCl followed by 0.1 M HCl + 0.005 M HF; and third, by passing the Th through a final 1.0 mL AG1x8 resin bed in 9 M HCl. The mass spectrometry is performed using the procedure 'Th and U Mass Spectrometry for {sup 230}Th-{sup 234}U Age Dating'.