The Los Alamos PC/FRAM code for the nondestructive analysis of the isotopic composition of plutonium and other actinides Page: 4 of 8
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THE LOS ALAMOS PC/FRAM CODE FOR THE NONDESTRUCTIVE
ANALYSIS OF THE ISOTOPIC COMPOSITION OF PLUTONIUM AND OTHER ACTINIDES
Thomas E. Sampson and Thomas A. Kelley
Safeguards Science and Technology, Group NIS-5
Los Alamos National Laboratory
Los Alamos, New Mexico 87545
The Safeguards Program at Los Alamos. National
Laboratory has developed versatile software for the
isotopic analysis of plutonium and other actinides from
the gamma ray spectrum of an arbitrary sample. These
developments began over 20 years ago and have been
used routinely at Los Alamos for 15 years. We will
present details of the PC/FRAM code as well as
discussing its application to a wide variety of
PC/FRAM requires a spectrum taken with an HpGe
gamma-ray detector along with a set of parameters that
drives the analysis. PC/FRAM generates estimates of the
plutonium isotopic ratios represented by that spectrum
and voluminous secondary information about the analysis
The spectrum may come from a multichannel
analyzer memory or from a disk file. The code currently
supports the collection and analysis of data from a
Canberra S 100, an ORTEC multichannel buffer, and the
Los Alamos M3CA. It can also read data stored in a
properly-structured text file.
The parameters that direct the analysis of a spectrum
describe the default calibration settings, the gamma-ray
peaks to be analyzed, the regions of interest, the isotopes
to consider, and a number of application-specific
constants that govern customized diagnostic tests,
parameters for the 242Pu correlation, and other functions.
A properly-designed set of parameters can be used for
a relatively wide variety of spectra. Because not all
spectra can be accommodated by a single set of
This work is supported by the US Department of Energy,
Office of Nonproliferation and National Security, Office
of Safeguards and Security, and the Stockpile Support
parameters, the code's database was constructed to handle
multiple parameter sets. A utility function built into the
software allows the user to view or modify the parameter
values without reprogramming the software.
In the first stage of the analysis, PC/FRAM
performs an internal calibration. Selected peaks in the
spectrum are used to provide a calibration of energy vs
channel, full width at half maximum (FWHM) vs
energy, and peak shape (tailing parameters) vs energy.
This means that the analysis does not depend on
measurements that may have been taken under different
conditions such as count rate, detector resolution, or
other electronic adjustments. The internal calibration is
performed with the same unknown spectrum that is being
analyzed. All the peaks used in the internal calibrations
are specified in the parameter set selected for analysis. A
separate list of calibration peaks may be specified for
each parameter. The calibration parameters may be set to
default values for analysis of spectra with weak peaks or
poor counting statistics.
The energy calibration is a piecewise linear
calibration between the pairs of peaks specified in the
The FWHM of the designated internal calibration
peaks is obtained from a quadratic curve fit to the
logarithm of the net counts. When all the FWHM's are
computed, the coefficients in the following model are
determined by a linear least squares analysis.
(FWHM)2 = A1 + A2 E+ A3E~1
This equation is used in the rest of the analysis to
estimate the FWHM of a peak at any given energy. The
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Sampson, T.E. & Kelley, T.A. The Los Alamos PC/FRAM code for the nondestructive analysis of the isotopic composition of plutonium and other actinides, article, June 1, 1996; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc672992/m1/4/: accessed April 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.