Quantitative portable gamma-spectroscopy sample analysis for non-standard sample geometries |
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Authors: | S B Ebara M W Enghauser |
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Institution: | (1) Personnel Monitoring and Laboratory Services, Radiation Protection Sample Diagnostics, Sandia National Laboratories, P.O. Box 5800, MS 0651, 87185-0651 Albuquerque, NM, USA;(2) Science Applications International Corporation (SAIC), 1180 Town Center Drive, 89134 Las Vegas, NV, USA |
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Abstract: | Utilizing a portable spectroscopy system, a quantitative method for analysis of samples containing a mixture of fission and
activation products in nonstandard geometries was developed. This method was not developed to replace other methods such as
Monte Carlo or Discrete Ordinates but rather to offer an alternative rapid solution. The method can be used with various sample
and shielding configurations where analysis on a laboratory based gamma-spectroscopy system is impractical. The portalle gamma-spectroscopy
method involves calibration of the detector and modeling of the sample and shielding to identify and quantify the radionuclides
present in the sample. The method utilizes the intrinsic efficiency of the detector and the unattenuated gamma fluence rate
at the detector surface per unit activity from the sample to calculate the nuclide activity and Minimum Detectable Activity
(MDA). For a complex geometry, a computer code written for shielding applications (MICROSHIELD) is utilized to determine the
unattenuated gamma fluence rate per unit activity at the detector surface. Lastly, the method is only applicable to nuclides
which emit gamma-rays and cannot be used for pure beta or alpha emitters. In addition, if sample self absorption and shielding
is significant, the attenuation will result in high MDA's for nuclides which solely emit low energy gamma-rays. The following
presents the analysis technique and presents verification results using actual experimental data, rather than comparisons
to other approximations such as Monte Carlo techniques, to demonstrate the accuracy of the method given a known geometry and
source term. |
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