Low-Level Determination of Plutonium by Gamma and?L X-ray Spectroscopy
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Heino Nitsche, Raymond C. Gatti, Shan C. Lee
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Lawrence Berkeley Laboratory
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? University of California
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Earth Sciences Division
April1991
?
Accepted for publication in the Journal of?Radioanalytical and Nuclear Chemistry.
This work was supported by the Yucca Mountain Site Characterization Project Office as part of the U.S.?Civilian Radioactive Waste Management Project through the Los Alamos National Laboratory. The Yucca?Mountain Site Characterization Project is managed by the U.S. Department of Energy, Yucca Mountain?Project. This work was performed at the Lawrence Berkeley Laboratory, which is operated by the University?of California for the U.S. Department of Energy under Contract DE-AC03-76SF00098.
ABSTRACT
We have developed an analytical method for detection of 239pu in aqueous samples at?concentrations as low as 10e-10M. This nuclear counting technique utilizes the uranium L X-rays,?which follow the alpha decay of plutonium. Because L X-rays are specific for the element and not for?the individual isotope, the isotopic composition of the plutonium sample must be known. The?counting efficiency in the 11-23 keV range is determined from a plutonium standard, and the?concentration of the sample is then calculated from the L X-ray count and the isotopic composition.
The total L X-ray count is corrected for possible contributions from? other radionuclides present as?impurities by measuring the low-energy gamma spectrum for each contaminant to establish specific?photon/X-ray ratios. The ratios are important when 241Pu and 242pu are measured, because the?respective decay chain members produce non-U L X-rays. This new method can replace the use of
labor-intensive radiochemical separation techniques and elaborate activation methods for analysis of?239pu in aqueous samples. It is also applicable for assaying plutonium in liquid wastes that pose?possible hazards to the environment.
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