Abstract A spectroscopic method to rapidly measure the presence of plutonium in soils, filters, smears, and glass waste forms by measuring the uranium L-shell x-ray emissions associated with the decay of plutonium. In addition, the technique can simultaneously acquire spectra of samples and automatically analyze them for the amount of americium and γ-ray emitting activation and fission products present. The samples are counted with a large area, thin-window, n-type germanium spectrometer which is equally efficient for the detection of low-energy x-rays (10-2000 keV), as well as high-energy γ rays (>1 MeV). A 8192- or 16,384 channel analyzer is used to acquire the entire photon spectrum at one time. A dual-energy, time-tagged pulser, that is injected into the test input of the preamplifier to monitor the energy scale, and detector resolution. The L x-ray portion of each spectrum is analyzed by a linear-least-squares spectral fitting technique. The γ-ray portion of each spectrum is analyzed by a standard Ge γ-ray analysis program. This method can be applied to any analysis involving x- and γ-ray analysis in one spectrum and is especially useful when interferences in the x-ray region can be identified from the γ-ray analysis and accommodated during the x-ray analysis.
Inventors
👤 Robert J. Gehrke
👤 Marie H. Putnam
👤 E. Wayne Killian
👤 Richard G. Helmer
👤 Ronnie L. Kynaston
👤 Scott G. Goodwin
👤 Larry O. Johnson
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-10-23 19:29
CPC Classifications
G; G01; G01T; G01T1/00; G01T1/36; G01T1/366
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
263 words
A method for measuring and analyzing an x-ray and γ-ray spectrum of radionuclides in a medium by a spectrometer, comprising the steps of: a. preparing a plurality of unknown activity samples of the medium within sample containers; b. preparing a set of calibration samples consisting of known activity samples of high purity radionuclides and a clean background sample; c. measuring response spectra of the calibration samples with the spectrometer; d. measuring the radionuclide activities or activity concentrations from the spectra associated with the plurality of unknown activity samples; e. injecting a low-energy and a high-energy pulse into a spectrometer preamplifier circuit while accumulating the above spectra thereby providing an energy calibration signal at a periodic interval during steps c. and d.; f. analyzing a γ-ray region of the spectra from the unknown activity samples using a non-linear peak fitting function; g. analyzing an x-ray region of the spectra from the unknown activity samples using a linear-least-squares spectral-fitting method by fitting the spectra of the plurality of unknown activity samples with the response spectra of the calibration samples; h. computing and displaying a Chi-squared number and a quality-of-fit value of the x-ray region data wherein a value less than two (2) indicates a good correlation between the unknown activity samples and the known activity samples, and a value greater than two (2) indicates a poor correlation between the unknown activity samples and the known activity samples; i. displaying the quality-of-fit value and a calibrated channel-by-channel residual when the quality-of-fit value is greater than two (2); and j. displaying an activity value for each nuclide.
Claim 2
Independent Claim
263 words
A method for measuring and analyzing an x-ray and γ-ray spectrum of radionuclides in a medium by a spectrometer, comprising the steps of: a. preparing a plurality of unknown activity samples of the medium within sample containers; b. preparing a set of calibration samples consisting of known activity samples of high purity radionuclides and a clean background sample; c. measuring response spectra of the calibration samples with the spectrometer; d. measuring the radionuclide activities or activity concentrations from the spectra associated with the plurality of unknown activity samples; e. injecting a low-energy and a high-energy pulse into a spectrometer preamplifier circuit while accumulating the above spectra thereby providing an energy calibration signal at a periodic interval during steps c. and d.; f. analyzing a γ-ray region of the spectra from the unknown activity samples using a non-linear peak fitting function; g. analyzing an x-ray region of the spectra from the unknown activity samples using a linear-least-squares spectral-fitting method by fitting the spectra of the plurality of unknown activity samples with the response spectra of the calibration samples; h. computing and displaying a Chi-squared number and a quality-of-fit value of the x-ray region data wherein a value less than two (2) indicates a good correlation between the unknown activity samples and the known activity samples, and a value greater than two (2) indicates a poor correlation between the unknown activity samples and the known activity samples; i. displaying the quality-of-fit value and a calibrated channel-by-channel residual when the quality-of-fit value is greater than two (2); and j. displaying an activity value for each nuclide.
Claim 3
Dependent Claim
20 words
The method as recited in claim 1 wherein the medium is a soil sample having traces of plutonium and americium.
Claim 4
Dependent Claim
23 words
The method as recited in claim 2 wherein a time for measurement of the sample response spectra is between 15 and 30 minutes.
Claim 5
Dependent Claim
19 words
The method as recited in claim 3 wherein a frequency of both injected energy pulses is about 100 Hz.
Claim 6
Dependent Claim
23 words
The method as recited in claim 4 wherein the low-energy pulse is about 12 keV and the high-energy pulse is about 1330 keV.
Claim 7
Dependent Claim
21 words
The method as recited in claim 5 wherein the activity value of the sample is less than 50 pico-Curies per gram.