2021 FDA Science Forum
A Comparison Between Two Methods of Gamma Spectrum Analysis for FDA Food Emergency Response Network Food Samples
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Contributing OfficeOffice of Regulatory Affairs
Abstract
Due to threats to the nation’s food supply as a result of a nuclear or radiological incident, Food Emergency Response Network (FERN) needs to detect and identify gamma-emitting radionuclides in foods. Proficiency test samples are routinely sent to FERN member laboratories for analysis of food samples containing multiple gamma-emitting radionuclides. FDA’s Winchester Engineering and Analytical Center (WEAC) participates in these proficiency studies and provides rapid identification of unknown gamma radionuclides in test samples.
The gamma spectrometer analyses of proficiency samples were performed using Canberra APEX and VRF (Visual RobFit) software to compare their performance characteristics.
Traditionally, spectrum analysis program begins with simple peak search followed by subtraction of environmental background. If the net peak area for a give peak is statistically significant, it is considered as detected and used for radionuclide identification. When there are unidentified peaks in the spectrum, adjustments to peak search parameters or energy recalibration will be required, which can be tedious and time-consuming.
Identification and quantification of gamma radionuclides is crucial for radiological risk assessment in the event of a radiological emergency. In order to identify gamma radionuclide quickly and reliably, an alternative approach applying non-linear least-squares minimization of chi-square to fit full-spectrum and continuum shapes was studied, which can be used as an additional confirmation for critical sample analysis.
A comparison study on Canberra Apex and VRF gamma spectral software was performed using gamma spectra of mixed gamma standards and fresh fission products. The results of VRF analysis were found to be more reliable for both detection and identification upon the initial run of an automated analysis as compared to its Canberra APEX 1.3 counterpart.
The comparison study indicated that it provides not only a fast identification of gamma radionuclides in food but also a useful alternative capability that is critical for responding to a radiological event that involves radioactive gamma radionuclides.
