RADIOACTIVE/NUCLEAR THREAT MONITORING USING LONG DETECTORS

• US 20120153168A1
• Filed: 04/14/2011
• Published: 06/21/2012
• Est. Priority Date: 04/19/2010
• Status: Abandoned Application

• Current Assignee: Rapiscan Systems Incorporated (OSI Systems Incorporated)
• Original Assignee: Rapiscan Systems Incorporated (OSI Systems Incorporated)
• Inventors: Langeveld, Willem Gerhardus Johannes
• Application Number:
  US13/086,738
• Publication Number:
  US 20120153168A1
• Time in Patent Office: Days
• US Class Current: 250/366
• CPC Class Codes: G01T 1/201 using scintillating fibres
• CPC Class Codes: G01T 3/008 using an ionisation chamber filled with a gas, liquid or solid, e.g. frozen liquid, dielectric G01T3/006 takes precedence
• CPC Class Codes: G01T 3/06 with scintillation detectors
• CPC Class Codes: G01V 5/0075 Passive interrogation for hand, feet or portals G01T1/167; for contaminated surface areas G01T1/169
• CPC Class Codes: G01V 5/26 Passive interrogation, i.e. by measuring radiation emitted by objects or goods
• CPC Class Codes: H01J 47/08 Geiger-Müller counter tubes gas filling with very short deionisation times H01J17/64, H01T

Abstract

The present specification discloses a radiological threat monitoring system capable of withstanding harsh environmental conditions. The system has (a) one or more cables for measuring a signal induced by a radiological material emitting ionizing radiation when the radiological material comes within a predefined distance of the cables; (b) one or more stations connected with one or more cables for measuring and recording the induced signal; and (c) a central station in communication with one or more stations for gathering the recorded measurements. Radiological material includes fissile threat material such as a ‘Special Nuclear Material’ (SNM).

Claims

1. A radiological threat monitoring system, comprising:

a. at least one cable having an enclosed, elongated interior volume for carrying an ionization current that is induced within the at least one cable by a radiological material emitting ionizing radiation when the radiological material is within a predefined distance from the at least one cable; and

b. at least one detector coupled with the at least one cable for measuring a signal corresponding to the induced ionization current, wherein the at least one detector records the measured signal.

2. The system of claim 1 wherein the radiological material is a fissile material.

3. The system of claim 1 wherein the cable is a Panofsky Long Ion Chamber.

4. The system of claim 1 further comprising a second cable having an enclosed, elongated interior volume for carrying an ionization current that is induced within the second cable by a radiological material emitting ionizing radiation when the radiological material is within a predefined distance from the second cable.

5. The system of claim 1 wherein the first cable is parallel to the second cable.

6. The system of claim 4 further comprising a second detector coupled to the second cable for measuring a signal corresponding to the induced ionization current, wherein the second detector records the measured signal.

7. The system of claim 6 wherein a monitoring station is in data communication with the at least one detector and second detector.

8. The system of claim 1 further comprising at least one sensor adapted to detect an attempt to tamper with the system.

9. The system of claim 8 wherein said at least one sensor is adapted to detect a severing of the at least one cable by periodically sending a signal through the at least one cable, to detect when the signal is reflected by an end of the at least one cable;

to determine a severing of the at least one cable when the reflected signal is not detected;

to calculate a time difference between a time of sending the signal and a time of receiving the reflected signal; and

to detect a severing of the at least one cable if the reflected signal is received before a predefined time period.

10. The system of claim 9 wherein the predefined time period is dependent upon a length of the at least one cable.

11. The system of claim 8 wherein the at least one sensor periodically sends a predefined status message conveying an operational status of said system to a monitoring station, wherein the monitoring station determines that the system is malfunctioning if the status message is not received at a predefined time interval.

12. The system of claim 1 wherein the at least one cable comprises a gas-filled coaxial cable adapted to carry a voltage, wherein said coaxial cable comprises at least one inner signal electrode concentrically surrounded by at least one outer electrode, wherein the inner and outer electrodes are separated by a spacer surrounding the inner electrode, and wherein the outer electrode is at a higher voltage compared to the inner electrode.

13. The system of claim 12 wherein the spacer is a ceramic material resistant to high voltages.

14. The system of claim 12 wherein the inner electrode comprises a conductive material.

15. The system of claim 12 wherein the spacer comprises a radiation ionizable dielectric at pressures in the range of 1 to 20 atmospheres before being sealed.

16. The system of claim 1 wherein the at least one cable comprises a scintillating substance and a plurality of light sensitive detector arranged along a length of the at least one cable.

17. The system of claim 16 wherein the scintillating substance is a liquid scintillator.

18. The system of claim 17 wherein light emitted by the scintillating substance is transmitted to the light sensitive detectors by wavelength shifting fibers.

19. The system of claim 16 where the scintillating substance comprises scintillating fibers.

20. A method of monitoring for radiological material, comprising:

a. Positioning at least one cable having an enclosed, elongated interior volume for carrying an ionization current that is induced within the at least one cable by a radiological material emitting ionizing radiation when the radiological material is within a predefined distance from the at least one cable;

b. Measuring a signal corresponding to the induced ionization current using at least one detector coupled with the at least one cable; and

c. Determining, based upon said measurement, whether radiological material is present within the predefined distance from the at least one cable.

21. The method of claim 20 wherein the at least one cable is positioned proximate to vehicular traffic to passively scan vehicular traffic for radiological material.

22. The method of claim 21 wherein the at least one cable is positioned by embedding it within a section of paved road.

23. The method of claim 20 wherein the at least one cable is positioned by laying it on the ground and attached to a plurality of stakes.

24. The method of claim 20 wherein the at least one cable is positioned by hanging it from a plurality of poles.

25. The method of claim 20 further comprising positioning a second cable having an enclosed, elongated interior volume for carrying an ionization current that is induced within the second cable by a radiological material emitting ionizing radiation when the radiological material is within a predefined distance from the second cable.

26. The method of claim 25 wherein the first cable is positioned parallel to the second cable.

27. The method of claim 25 further comprising measuring a signal corresponding to the induced ionization current in the second cable using a second detector.