APPLICATION OF INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY FOR DETERMINATION OF URANIUM AND PLUTONIUM CONTENT AND ISOTOPIC RATIOS IN ENVIRONMENTAL SAMPLES

10th International Multidisciplinary Scientific GeoConference - SGEM2010, www.sgem.org, SGEM2010 Conference Proceedings/ ISBN 10: 954-91818-1-2, June 20-26, 2010, Vol. 2, 413-418 pp

ABSTRACT

The determination of environmental contamination with natural and artificial actinide
isotopes and evaluation of their source requires precise determination of concentration
and isotopic ratios of actinides in environmental samples. The most conventional
analytical tools used for uranium and plutonium isotope determination are liquid
scintillation and alpha spectrometry, and thermal ionization mass spectrometry is still
considered as the primary method for determination of plutonium isotope ratios.
Inductively coupled plasma mass spectrometry (ICP-MS) can offer now another
alternative method for the isotopic analysis of long-lived radionuclides at the ultra-trace
concentration level due to its high sensitivity, good accuracy and precision.

This paper presents and discuses the results obtained for plutonium and uranium content
and isotope ratios by sector field ICP-MS in different environmental samples. The
determination of uranium and plutonium concentrations and isotopic ratios were
performed using high resolution mass spectrometer ELEMENT Finnigan MAT with
ultrasonic nebulizer U-5000AT+. The detection limit was estimated as 1.10-4 ppb (238U),
2.10-6 ppb (234,235,236U, 239,240,242Pu) in 5% HNO3 solution. The UH+/U+ and PuH+/Pu+
formation rate was about 3.10-5 and sensitivity of 238U up to 3.106 cps ppb-1 was
achieved. The precision of concentration determination was 2-5% (RSD), and the
precision of isotopic analysis was 0.5 % (238U/235U) and 10 % (238U/234U, 238U/236U).
Formed molecular interferences and background at measured masses were taken into
account for reception of correct results.

On the basis of the received data the conclusion about convenience of ICP-MS
alongside with α-spectrometry for ecological monitoring has been made.

Keywords: Uranium, Plutonium, isotopic ratios, environmental samples, inductively coupled plasma mass-spectrometry.