Nonintrusive method for the detection of concealed special nuclear material

• US 20050220247A1
• Filed: 04/06/2004
• Published: 10/06/2005
• Est. Priority Date: 04/06/2004
• Status: Active Grant

• Current Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Congedo, Thomas V., Petrovic, Bojan, Kucukboyaci, Vefa N., Seidel, John G., Dulloo, Abdul R., Ruddy, Francis H.
• Granted Patent: US 7,151,815 B2
• Time in Patent Office: Days
• US Class Current: 376/159
• CPC Class Codes: G01V 5/281 detecting special nuclear material [SNM], e.g. Uranium-235, Uranium-233 or Plutonium-239

Abstract

A method and associated apparatus for detecting concealed fissile, fissionable or special nuclear material in an article, such as a shipping container, is provided. The article is irradiated with a source of fast neutrons, and fast neutrons released by the fissile or fissionable material, if present, are detected between source neutron pulses. The method uses a neutron detector that can detect and discriminate fast neutrons in the presence of thermal neutrons and gamma radiation. The detector is able to process high count rates and is resistant to radiation damage, and is preferably a solid state neutron detector comprised of silicon carbide.

Claims

1. A method of detecting concealed fissile material in an article comprising:

providing at least one solid state fast neutron detector and at least one source of fast neutrons characterized by a particle energy greater than 1 Mev, a source strength, a pulse width and a pulse frequency;

irradiating said article with fast neutrons having energy levels greater than 1 Mev from said at least one neutron source to effect emission of fast neutron radiation from said fissile material, if present;

acquiring fast neutron data indicative of the number of fast fission neutrons emitted from said fissile material during a predetermined time period; and

analyzing said data to determine the presence or absence of said fissile material.

2. The method of claim 1, wherein said neutron detector is comprised of Sic.

3. The method of claim 1, wherein said neutron detector is comprised of a material selected from the group consisting of silicon, cadmium zinc telluride (CZT), cadmium telluride, gallium arsenide and diamond.

4. The method of claim 1, wherein said particle energy of said neutron source irradiating the article is between 1 Mev and 25 Mev.

5. The method of claim 1, wherein said particle energy of said neutron source irradiating the article is selected from the group consisting of 2.5 Mev and 14 Mev.

6. The method of claim 1, wherein said source strength is about 10⁷ -10¹² neutrons per second.

7. The method of claim 1, wherein said pulse width is about 4 ns to 200 μ

s.

8. The method of claim 1, wherein said pulse frequency is about 100 to 10,000,000 Hz.

9. The method of claim 1, wherein said article is a cargo container.

10. The method of claim 1, wherein said at least one neutron source is a plurality of neutron sources.

11. The method of claim 1, wherein said at least one neutron detector is a plurality of neutron detectors.

12. An apparatus for detecting fissile material in an article comprising:

a neutron source for generating neutrons characterized by a particle energy, source strength, pulse width and pulse frequency;

at least one fast neutron detector for detecting the fast neutron radiation emitted from the article;

source electronics means associated with the neutron source for controlling said pulse width of neutrons generated by the neutron source;

detector electronics means associated with the at least one fast neutron detector for amplifying and digitalizing signals generated by the at least one fast neutron detector and storing data representing the digitalized signals;

spectral analysis means for analyzing the data and determining the presence or absence of fast neutron emission from the article; and

an acquisition interface module (AIM) for controlling the timing of the source and detector electronics such that the neutron source generates neutrons in a burst of a prescribed pulse width and the detectors and detector electronics means detect fast neutrons during the time interval between bursts and acquire data indicative of the number of fast neutrons emitted in the time interval between successive bursts.

13. The apparatus of claim 12, wherein said neutron detector is comprised of SiC.

14. The apparatus of claim 12, wherein said neutron detector is comprised of a material selected from the group consisting of silicon, cadmium zinc telluride (CZT), cadmium telluride, gallium arsenide and diamond.

15. The apparatus of claim 12, wherein said particle energy of said neutron source is about 100 Kev to 25 Mev.

16. The apparatus of claim 12, wherein said particle energy of said neutron source is selected from the group consisting of 0.025 eV, 750 Kev, 2.5 Mev and 14 Mev.

17. The apparatus of claim 12, wherein said source strength is about 10⁷-10¹² neutrons per second.

18. The apparatus of claim 12, wherein said pulse width is about 4 ns to 200 μ

s.

19. The apparatus of claim 12, wherein said pulse frequency is about 100 to 10,000,000 Hz.

20. The apparatus of claim 12, wherein said article is a cargo container.

21. The apparatus of claim 12, wherein said at least one neutron source is a plurality of neutron sources.

22. The apparatus of claim 12, wherein said at least one neutron detector is a plurality of neutron detectors.

23. The apparatus of claim 12, in combination with an x-ray detector.

24. The apparatus of claim 12, in combination with a gamma ray detector.