Enhanced vehicle radiation monitoring system and method

• US 5,679,956 A
• Filed: 04/14/1995
• Issued: 10/21/1997
• Est. Priority Date: 04/14/1995
• Status: Expired due to Term

• Current Assignee: Thermo Electron Corporation (Thermo Fisher Scientific Incorporated)
• Original Assignee: Saint-Gobain/Norton Industrial Ceramics Corporation
• Inventors: Johnston, Joseph G.
• Primary Examiner(s): Glick, Edward J.
• Application Number:
  US08/422,553
• Time in Patent Office: 921 Days
• Field of Search: 250/336.1, 250/357.1, 250/358.1, 250/359.1, 250/394
• US Class Current: 250/357.1
• CPC Class Codes: G01T 1/167 Measuring radioactive content of objects, e.g. contamination whole body counters G01T1/163
• CPC Class Codes: G01V 5/26 Passive interrogation, i.e. by measuring radiation emitted by objects or goods

Abstract

A radiation detection system and method for scanning an object for ionizing radiation are generally characterized by at least one radiation detector which provides an output related to the level of ionizing radiation impinging thereon, a sensing device which evaluates and provides an output related to a shape characteristic of an object being scanned by the radiation detector, and a processor operatively connected to the radiation detector and sensing device for processing the outputs thereof. The output of the sensing device is used to compensate for variations in ambient background level arising from the sensed shape characteristic of the object. With such a system, the possibility of a geometry induced false alarm is minimized. In a preferred embodiment adapted for dynamic vehicle monitoring, the sensing device is a level detector operative to detect the level of the material in a truck or rail car passing by the radiation detector or detectors. The processor is operatively connected to the radiation detector and level detector for issuing an alarm signal upon satisfying a predetermined criteria, the processor being operative to use the output of the level detector to compensate the output of the radiation detector for variations in the background level arising from differences in the level of the material. The foregoing enables maximum sensitivity to be maintained while eliminating or reducing false alarms arising from variations in scrap loads that otherwise might have triggered a false alarm in previously used systems.

Claims

1. A radiation detection system for scanning an object for ionizing radiation, comprising at least one radiation detector which provides an output related to the level of ionizing radiation impinging thereon, a sensing device which evaluates and provides an output related to a shape characteristic of an object being scanned by the at least one radiation detector, and a processor operatively connected to the at least one radiation detector and sensing device for processing the outputs thereof, the output of the sensing device being used to compensate for variations in the level of background radiation resulting from variations in the shape characteristic of the object;

said at least one radiation detector being directed toward a scan area through which the object can move for scanning by said at least one radiation detector;

said sensing device being positioned in relation to said scan area such that it is operative to determine the height of the object passing through said scan area relative to a base line.

2. A system as set forth in claim 1, wherein said sensing device is located above the scan area and downwardly aimed to detect the height of the object in an open top vehicle.

3. A system as set forth in claim 2, wherein said sensing device includes at least one distance measuring device.

4. A radiation detection system for scanning an object for ionizing radiation, comprising at least one radiation detector which provides an output related to the level of ionizing radiation impinging thereon, a sensing device which evaluates and provides an output related to a shape characteristic of an object being scanned by the at least one radiation detector, and a processor operatively connected to the at least one radiation detector and sensing device for processing the outputs thereof, the output of the sensing device being used to compensate for variations in level of background radiation resulting from variations in the shape characteristic of the object;

said sensing device being positioned in relation to a scan area in front of said at least one radiation detector such that it is operative to determine the height of the object passing through said scan area relative to a base line.

5. A system as set forth in claim 4, wherein said sensing device is located above the scan area and downwardly aimed to detect the height of the object in an open top vehicle.

6. A radioactive material detection system for scanning material for radioactive objects, comprising

at least one radiation detector on which ionizing radiation can impinge to induce an output related to the level of such impinging ionizing radiation, the at least one radiation detector being configured for passage thereby of the material to be scanned, the at least one radiation detector being sensitive to background radiation that is at least partially shielded by the material as the material is being passed thereby, and the at least one radiation detector being operative to provide an output indicative of incident background radiation and any incident radiation arising from a radioactive object in the material as the material is passed by the at least one radiation detector,

a height detector operative to detect the height of the material passing by the at least one radiation detector and provide an output representative of the height,

a processor operatively connected to the at least one radiation detector and height detector for issuing an alarm signal upon the outputs of the at least one radiation detector and the height detector satisfying a predetermined criteria, the processor being operative to use the output of the height detector to compensate the output of the at least one radiation detector for variations in the level of background radiation resulting from differences in the height of the material.

7. A system as set forth in claim 6, wherein said at least one radiation detector comprises a plurality of radiation detectors disposed on respective sides of a scan area through which the material can move for scanning by said radiation detectors.

8. A system as set forth in claim 7, wherein said height detector includes at least one distance measuring device.

9. A system as set forth in claim 8, wherein said at least one distance measuring device is positioned in relation to said scan area such that it is operative to determine the height of the material passing through said scan area relative to a base line.

10. A system as set forth in claim 9, wherein said distance measuring device is located above the scan area and downwardly aimed to detect the height of the material in an open top vehicle.

11. A method of scanning for a load of material for radioactive substances, comprising the steps of:

passing a load of material to be scanned past a radiation detector, the radiation detector being exposed to background radiation when the load of material is not being passed thereby and the background radiation being at least partially shielded by the load of material when the load of material is being passed thereby, the radiation detector providing an output indicative of incident background radiation and any incident radiation arising from a radioactive substance in the load of material,

using a height detector to measure the height of the load of material along the length thereof, and

using a processor to process the outputs of the radiation detector and the height detector, said processing step including the steps of using the output of the height detector to compensate the output of the radiation detector for variations in the level of background radiation resulting from differences in the height of the material and issuing an alarm upon the compensated output of the radiation detector satisfying a predetermined criteria.

12. A method as set forth in claim 11, wherein said using a height detector step includes using at least one distance measuring device.

13. A method as set forth in claim 12, wherein the at least one distance measuring device is positioned in relation to a scan area in front of the radiation detector such that it is operative to determine the height of the material passing through said scan area relative to a base line.

14. A method as set forth in claim 13, wherein the at least one distance measuring device is located above the scan area and downwardly aimed to detect the height of material in an open top vehicle.

15. A method as set forth in claim 11, wherein the material is carried in a truck moving past the radiation detector.

16. A method as set forth in claim 11, wherein the material is carried in a rail car moving past the radiation detector.