We describe the characteristics and features and demonstrate the performance of a new code (FRAM) for determining the isotopic composition of plutonium using gamma-ray spectroscopy. This versatile code can measure an extremely wide range of isotopic compositions and is extremely easy to tailor to specialized measurement conditions. Measurement precision, accuracy, and throughput are significantly improved over previous Los Alamos National Laboratory (LANL) codes. 13 refs., 2 figs., 4 tabs.

The FRAM code (Fixed-energy Response-function Analysis with Multiple efficiency) was developed at Los Alamos National Laboratory (LANL) for the gamma-ray spectrometry measurement of the isotopic composition of plutonium, uranium, and other actinides. It is capable of analyzing gamma ray peaks obtained with the germanium detectors in the energy range from 30 keV to greater than 1 MeV, including the X-ray region. It is very robust and can analyze spectra from good detectors as well as much degraded detectors. How much does the detector degradation affect the FRAM isotopic analysis performance at each different energy region? What are the worst resolutions of a detector (planar germanium or coaxial germanium) at various energy regions that FRAM can still analyze the data? What input rate is optimal for an isotopic gamma-ray system? How does the input rate affect the precision and the bias of a measurement? These questions and others will be answered.

The Fixed-Energy Response-Function Analysis with Multiple Efficiency (FRAM) software has been developed and is continuing to be refined at the Los Alamos National Laboratory for gamma-ray spectrometry measurements of isotopic composition of plutonium, uranium, and other actinides. The FRAM vA code was released in 2002. Since then, we have added many new features to improve the analysis for better analytical results and to meet user needs. 'Simple is good' is the motto of this upgraded version, v.5. We have strived to make this new version as simple and intuitive as possible such that almost anyone can use it effectively without the need for extensive training. Even with a simple user interface, FRAM v.5 still retains virtually all the capability of FRAM v.4 and has many new functions for the experts to use in addressing the many difficult-to-analyze spectra.

The Fixed-Energy Response-Function Analysis with Multiple Efficiency (FRAM) code was developed at Los Alamos National Laboratory to measure the gamma-ray spectrometry of the isotopic composition of plutonium, uranium, and other actinides. Its reported uncertainties of the results come from the propagation of the statistics in the peak areas only. No systematic error components are included in the reported uncertainties. We have done several studies and found that the FRAM's statistical precision can be reasonably represented by its reported uncertainties. The FRAM's biases or systematic uncertainties can come from a variety of sources and can be difficult to determine. We carefully examined the FRAM analytical results of the archival plutonium data and of the data specifically acquired for this isotopic uncertainty analysis project and found the relationship between the bias and other parameters. We worked out the equations representing the biases of the measured isotopes from each measurement using the internal parameters in the spectrum such as peak resolution and shape, region of analysis, and burnup (for plutonium) or enrichment (for uranium).

The Fixed-Energy Response-Function Analysis with Multiple Efficiency (FRAM) code was developed at Los Alamos National Laboratory to measure the gamma-ray spectrometry of the isotopic composition of plutonium, uranium, and other actinides. They have studied and identified two different kinds of errors from FRAM analysis: random and systematic. The random errors come mainly from statistics and are easily determined. The systematic errors can come from a variety of sources and can be very difficult to determine. The authors carefully examined the FRAM analytical results of the archival plutonium data and of the data specifically acquired for this isotopic uncertainty analysis project, and found the relationship between the systematic errors and other parameters. They determined that the FRAM's systematic errors could be expressed as functions of the peak resolution and shape, region of analysis, and burnup (for plutonium) or enrichment (for uranium). All other parameters such as weight, matrix material, shape, size, container, electronics, detector, input rate, etc., contribute little to the systematic error or they contribute to the peak resolution and shape and then their contributions can be determined from the peak resolution and shape.

FRAM is the acronym for Fixed-energy Response-function Analysis with Multiple efficiency. This software was developed at Los Alamos National Laboratory originally for plutonium isotopic analysis. Later, it was adapted for uranium isotopic analysis in addition to plutonium. It is a code based on a self-calibration using several gamma-ray peaks for determining the isotopic ratios. The versatile-parameter database structure governs all facets of the data analysis. User editing of the parameter sets allows great flexibility in handling data with different isotopic distributions, interfering isotopes, and different acquisition parameters such as energy calibration and detector type.