Real time method and computer system for identifying radioactive materials from HPGe gamma-ray spectroscopy

• US 20040195517A1
• Filed: 04/19/2004
• Published: 10/07/2004
• Est. Priority Date: 11/19/2002
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Howard, Douglas E., Rowland, Mark S., Wong, James L., Miller, Wayne O., Jessup, James L., Bianchini, Greg M.
• Granted Patent: US 7,285,784 B2
• Time in Patent Office: Days
• US Class Current: 250/370.15
• CPC Class Codes: G01T 1/244 Auxiliary details, e.g. casings, cooling, damping or insulation against damage by, e.g. heat, pressure or the like

Abstract

A real-time method and computer system for identifying radioactive materials which collects gamma count rates from a HPGe gamma-radiation detector to produce a high-resolution gamma-ray energy spectrum. A library of nuclear material definitions (“library definitions”) is provided, with each uniquely associated with a nuclide or isotope material and each comprising at least one logic condition associated with a spectral parameter of a gamma-ray energy spectrum. The method determines whether the spectral parameters of said high-resolution gamma-ray energy spectrum satisfy all the logic conditions of any one of the library definitions, and subsequently uniquely identifies the material type as that nuclide or isotope material associated with the satisfied library definition. The method is iteratively repeated to update the spectrum and identification in real time.

Claims

1. A real-time method in a computer system for identifying radioactive materials, the method comprising:

providing a data library of nuclear material definitions (“

library definitions”

) each uniquely associated with a known nuclide, isotope, or material and each comprising at least one logic condition associated with a spectral parameter of a gamma-ray energy spectrum;

collecting gamma count rates from a HPGe gamma-radiation detector to produce a high-resolution gamma-ray energy spectrum;

determining whether the spectral parameters of said high-resolution gamma-ray energy spectrum satisfy all the logic conditions of any one of said library definitions; and

uniquely identifying the material type as that nuclide, isotope, or material associated with the satisfied library definition.

2. The method of claim 1,

wherein the determination step includes evaluating peak regions of the high-resolution gamma-ray energy spectrum for statistical significance by determining whether the gamma count rate associated with a peak region exceeds a pre-set significance threshold, upon which a logical variable associated with a peak region is assigned a value of logical true.

3. The method of claim 2,

wherein the logic condition(s) of at least one of the library definitions require coincidence in peak region significance.

4. The method of claim 2,

wherein the determination step includes determining whether the count rate falls within pre-defined regions of interest (“

ROI”

), upon which a logical variable associated with one of said pre-defined regions of interest is assigned a value of logical true.

5. The method of claim 4,

wherein, a pre-defined message is sent to an operator when the logical variable associated with an ROI is assigned a value of logical true.

6. The method of claim 4,

wherein the determination step includes calculating ratios of numerical values associated with peak regions and/or ROIs, and assigning a logical variable associated therewith a value of logical true.

7. The method of claim 6, further comprising:

determining an applicable one of a set of pre-defined numerical ranges into which the calculated ratios fall; and

sending to an operator a pre-defined message associated with the applicable numerical range.

8. The method of claim 7,

wherein at least one numerical range is associated with a pre-defined message chosen from the group consisting of background, metal uranium, and beta emitters.

9. The method of claim 6,

wherein the spectral parameters include at least one of peak region, ROI, and calculated ratio, and the predefined logic conditions of the library definitions involve at least one of said spectral parameters.

10. The method of claim 9,

wherein the predefined logic conditions of said library definitions include logical value requirements of true, false, and combinations thereof for different logical variables.

11. The method of claim 1,

wherein the method steps are iteratively repeated at substantially short time intervals to update the identification with cumulative data.

12. The method of claim 11,

wherein the substantially short time intervals is in the range of about one to about 5 seconds.

13. The method of claim 12,

wherein the substantially short time intervals is one second.

14. The method of claim 1, further comprising:

determining an applicable one of a set of pre-defined numerical ranges into which the gamma count rate falls; and

sending to an operator a pre-defined message associated with the applicable numerical range.

15. The method of claim 1, further comprising:

reporting the identified nuclide or isotope type to an operator.

16. The method of claim 15,

wherein the identified nuclide or isotope type is reported to the operator via a display screen.

17. The method of claim 15,

wherein the reporting of the identified nuclide or isotope type to the operator precludes the sending of inconsistent messages to the operator.

18. The method of claim 1, further comprising:

automatically deriving the energy calibration by utilizing an energy calibration coefficient table to map the relationship between system component temperatures and current energy calibration.

20. The computer system of claim 18, further comprising:

a peak region significance evaluation module that determines whether the gamma count rate associated with a peak region exceeds a pre-set significance threshold.

21. The computer system of claim 18, further comprising:

a reporting module adapted to report the unique identification to an operator.

19. A computer system for identifying radioactive materials, the system comprising:

a gamma-ray detection module that converts gamma rays into electrical signals from which gamma count rates are collected and a gamma-radiation energy spectrum is produced;

a library module of nuclear material definitions (“

library definitions”

) each uniquely associated with a nuclide or isotope material and each comprising at least one logic condition associated with a spectral parameter of a gamma-ray energy spectrum;

a compliance module adapted to determine whether the spectral parameters of said high-resolution gamma-ray energy spectrum satisfy all the logic conditions of any one of said library definitions; and

an identification module adapted to uniquely identify the material type as that nuclide or isotope material associated with the compliant library definition.

22. A computer program product comprising:

a computer usable medium having computer readable program code embodied therein for causing the identification of radioactive materials, the computer readable program code comprising;

a database comprising a library of nuclear material definitions (“

library definitions”

) each uniquely associated with a nuclide or isotope material and each comprising at least one logic condition associated with a spectral parameter of a gamma-ray energy spectrum;

computer readable program code means for collecting gamma count rates collecting gamma count rates from a HPGe gamma-radiation detector to produce a high-resolution gamma-ray energy spectrum;

computer readable program code means for determining whether the spectral parameters of said high-resolution gamma-ray energy spectrum satisfy all the logic conditions of any one of said library definitions; and

computer readable program code means for uniquely identifying the material type as that nuclide or isotope material associated with the satisfied library definition.

23. A real-time method in a computer system for gamma-ray energy calibration comprising:

providing a database of pre-determined gamma-ray energy coefficients associated with various temperature ranges; and

automatically deriving the energy calibration by utilizing the energy calibration coefficients of the database to map the relationship between system component temperatures and current energy calibration.