Portable detection apparatus and method

• US 9,562,978 B2
• Filed: 10/26/2012
• Issued: 02/07/2017
• Est. Priority Date: 10/27/2011
• Status: Active Grant

• Current Assignee: Atomic Energy of Canada Limited (Government of Canada)
• Original Assignee: Atomic Energy of Canada Limited (Government of Canada)
• Inventors: Dai, Xiongxin, Li, Liqian, Jonkmans, Guy, Ho, Aaron
• Primary Examiner(s): Porta, David
• Assistant Examiner(s): FEIN, ABRA S
• Application Number:
  US14/262,186
• Publication Number:
  US 20140291531A1
• Time in Patent Office: 1,565 Days
• Field of Search: 250/366, 250/394
• US Class Current: 1/1
• CPC Class Codes: G01T 1/167 Measuring radioactive content of objects, e.g. contamination whole body counters G01T1/163
• CPC Class Codes: G01T 1/2002 Optical details, e.g. reflecting or diffusing layers
• CPC Class Codes: G01T 1/2006 using a combination of a scintillator and photodetector which measures the means radiation intensity
• CPC Class Codes: G01T 1/2023 Selection of materials see provisionally also G01T1/202
• CPC Class Codes: G01T 7/00 Details of radiation-measuring instruments
• CPC Class Codes: G01T 7/125 Alarm- or controlling circuits using ionisation chambers, proportional counters or Geiger-Mueller tubes, also functioning as UV detectors measuring radiation intensity with counting tubes G01T1/18; measuring radiation intensity with ionisation chambers G01T1/185; flame monitoring in combustion devices F23Q7/00, F23N; fire alarms actuated by presence of radiation of particles, e.g. of infrared radiation, of ions G08B17/11; discharge tubes per se H01J47/00

Abstract

A portable detection apparatus can include a housing, a first detector for detecting ionizing radiation from a first subject and a second detector within the housing for the detecting the background radiation. A shield within the housing can surround the first and second detectors and define a shield aperture around the first and second detectors for radiation from the subject to enter the housing. A radiation blocking member can substantially block at least a portion of the ionizing radiation from reaching the second detector, whereby radiation detected by the second detector comprises substantially only the background radiation. A processor module can be connected to the first and second detectors for determining the amount of ionizing radiation detected by the first detector attributable to secondary radiation.

Claims

1. A portable detection apparatus, comprising:

a) a housing;

b) a first detector within the housing for detecting ionizing radiation comprising background radiation and secondary radiation;

c) a second detector within the housing for the detecting the background radiation;

d) a shield within the housing and surrounding the first and second detectors, the shield defining a shield aperture around the first and second detectors for the ionizing radiation to enter the housing;

e) a radiation blocking member positioned between the shield aperture and the second detector so that a first portion of the ionizing radiation entering the housing through the shield aperture reaches the first detector without passing through the radiation blocking member and a second portion of the ionizing radiation entering the housing through the shield aperture passes through the radiation blocking member before reaching the second detector, whereby radiation detected by the second detector comprises substantially only the background radiation; and

f) a processor module connected to the first and second detectors for determining the amount of ionizing radiation detected by the first detector attributable to the secondary radiation.

2. The apparatus of claim 1, wherein the housing defines a detection apparatus axis and being axially alignable with the subject, and the first detector comprises a first scintillator having an exposed first detection surface extending in a generally lateral direction and positionable opposite the subject, and the second detector comprising a second scintillator having an second detection surface extending in the generally lateral direction.

3. The apparatus of claim 2, wherein the radiation blocking member covers substantially all of the second detection face, whereby the secondary radiation is substantially prevented from reaching the second detection face.

4. The apparatus of claim 2, wherein the first scintillator produces a first light when excited by the ionizing radiation and the second scintillator produces a second light when excited by the ionizing radiation and further comprising a photosensor positioned adjacent the first and second scintillators to receive the first light and generate a corresponding first output signal, and to receive the second light and generate a corresponding second output signal.

5. The apparatus of claim 4, wherein the processor module is operably linked to the photosensor and is operable to determine the amount of ionizing radiation detected by the first detector attributable to the secondary radiation by comparing the second output signal with the first output signal.

6. The apparatus of claim 4, wherein the photosensor comprise a first photomultiplier tube to receive the first light and generate the first output signal and a second photomultiplier tube to receive the second light and generate the second output signal.

7. The apparatus of claim 2, wherein the first and second scintillators comprise first and second detection crystals, respectively.

8. The apparatus of claim 7, wherein the first scintillator has an overall surface area and the first detection surface has a detection surface area, and the detection surface area is between about 25% and about 45% of the overall surface area.

9. The apparatus of claim 7, wherein the first scintillator has a first thickness in the axial direction of less than about 25 mm.

10. The apparatus of claim 7, wherein the first and second detection crystals comprise NaI(TI) crystals.

11. The apparatus of claim 7, wherein the second scintillator is generally identical to the first scintillator.

12. The apparatus of claim 2, wherein the shield laterally surrounds the first scintillator and the second scintillator and the shield aperture is registered with the first detection surface and the second detection surface.

13. The apparatus of claim 1, wherein the radiation blocking member has a thickness between about 0.05 mm and about 5 mm.

14. The apparatus of claim 1, wherein the shield comprises

a) a first shielding layer formed from a first material;

b) a second shielding layer formed from a second material and disposed laterally inboard of the first shielding layer; and

c) a third shielding layer disposed laterally inboard of the second shielding layer;

and wherein the first shielding layer has a first lateral width, the second shielding layer has a second lateral width and the third shielding layer has a third lateral width, the first lateral width being greater than the both the second and third lateral widths.

15. The apparatus of claim 14, wherein the first shielding layer is formed from lead or tungsten, and the first lateral width is between about 2.5 mm and 125 mm.

16. The apparatus of claim 14, wherein the second shielding layer is formed from tin, and the second lateral width is between about 0.25 mm and about 25 mm.

17. The apparatus of claim 14, wherein the third shielding layer is formed from copper, and the third lateral width is between about 0.25 mm and about 25 mm.

18. The apparatus of claim 1, wherein the detection apparatus is a mountable on a vehicle.

19. The apparatus of claim 1, wherein radioactive material within the subject emits beta radiation and the secondary radiation is bremsstrahlung radiation produced by an interaction between the beta radiation from the radioactive material and the subject.

20. The apparatus of claim 1, wherein the detection apparatus is configured to measure photons having an energy that is less than about 500 keV.

21. The apparatus of claim 20, wherein the detection apparatus is configured to measure photons having an energy that is greater than about 30 keV.

22. The apparatus of claim 1, wherein the processor module is operable to determine a quantity of a radioactive material contained in the subject based on the amount of ionizing radiation detected by the first detector attributable to the secondary radiation measured by the detection apparatus.

23. The apparatus of claim 22, wherein the processor module is operable to compare at least one of the amount of ionizing radiation detected by the first detector attributable to the secondary radiation and the quantity of the radioactive material contained in the subject to a predetermined alarm threshold value and generate an alarm signal if the at least one of the amount of ionizing radiation detected by the first detector attributable to the secondary radiation and the quantity of the radioactive material contained in the subject exceeds the alarm threshold value.

24. The apparatus of claim 1, wherein the radiation blocking member comprises a plate member.

25. The apparatus of claim 24, wherein the plate member comprises at least one of copper, tin, and aluminum or a combination thereof.

26. The apparatus of claim 1, wherein the radiation blocking member allows transmission of the background radiation there through, whereby the background radiation can reach the second detector.

27. A portable detection apparatus, comprising:

a) a housing;

b) a first detector within the housing for detecting ionizing radiation comprising background radiation and secondary radiation from a subject;

c) a second detector within the housing for the detecting the background radiation;

d) a shield within the housing surrounding the first and second detectors and defining a shield aperture around the first and second detectors for radiation from the subject to enter the housing;

e) a radiation blocking member substantially blocking at least a portion of the ionizing radiation entering the housing through the shield aperture from reaching the second detector, whereby radiation detected by the second detector comprises substantially only the background radiation; and

f) a processor module connected to the first and second detectors for determining the amount of ionizing radiation detected by the first detector attributable to the secondary radiation;

wherein time elapsed between exposure of the detection apparatus to the source of the secondary radiation and obtaining the resultant output signal defines a detection cycle time, and the detection cycle time is less than about 10 minutes.

28. The apparatus of claim 27, wherein the detection cycle time is less than about 2 minutes.

29. A portable detection apparatus, comprising:

a) a housing;

b) a first detector within the housing for detecting ionizing radiation comprising background radiation and secondary radiation from a subject;

c) a second detector within the housing for the detecting the background radiation;

d) a shield within the housing surrounding the first and second detectors and defining a shield aperture around the first and second detectors for radiation from the subject to enter the housing;

e) a radiation blocking member substantially blocking at least a portion of the ionizing radiation entering the housing through the shield aperture from reaching the second detector, whereby radiation detected by the second detector comprises substantially only the background radiation; and

f) a processor module connected to the first and second detectors for determining the amount of ionizing radiation detected by the first detector attributable to the secondary radiation;

wherein the detection apparatus has an operating sensitivity capable of detecting an activity of at least about 460 Bq within the subject using a 5 minute scan.

30. A portable radiation detection system comprising:

a) a vehicle; and

b) a portable radiation detection apparatus according to any one of claims 1-3, 5, 10, 14, 19, 24, 26, 27, 28 and 29 mounted on and transportable with the vehicle.

31. The system of claim 30, wherein the vehicle comprises a radiation shielded chamber, and the first and second detectors are provided within the shielded chamber.

32. A method of indirectly measuring a quantity of a beta-emitting radioactive material within a subject using a portable detection apparatus, the method comprising:

a) positioning the portable detection apparatus adjacent the subject, the portable detection apparatus comprising a first detector, configured to detect ionizing radiation comprising background radiation and secondary radiation, and a second detector configured to detect ionizing radiation, wherein the secondary radiation is emitted by the subject and is produced by an interaction between beta radiation emitted by the radioactive material and the subject;

b) detecting a combination of the secondary radiation and the background radiation using the first detector and providing a corresponding a first output signal;

c) simultaneously detecting the background radiation using the second detector and providing a corresponding second output signal; and

d) automatically calculating a resultant output value based on at least the first output signal and the second output signal by subtracting the second output signal from the first output signal to determine a first quantity of secondary radiation received by the detection apparatus.

33. The method of claim 32, further comprising comparing the resultant output value to a predetermined alarm threshold value, and generating an alarm output if the resultant output value exceeds the alarm threshold value.

34. The method of claim 32, wherein calculating the resultant output value comprises comparing subtracting the second output signal from the first output signal to determine a first quantity of secondary radiation received by the detection apparatus.

35. The method of claim 32, further comprising transporting the portable detection apparatus to a temporary testing location.

36. The method of claim 32, further comprising positioning a radiation blocking member between the second detector and the subject to inhibit the secondary radiation from reaching the second detector.

37. A method of measuring a quantity of a beta-emitting radioactive material within a subject using a portable detection apparatus, the method comprising:

a) positioning the portable detection apparatus adjacent the subject, the portable detection apparatus comprising a first detector, configured to detect ionizing radiation comprising background radiation and secondary radiation, and a second detector configured to detect ionizing radiation;

b) detecting a combination of the secondary radiation and the background radiation using the first detector and providing a corresponding a first output signal;

c) simultaneously detecting the background radiation using the second detector and providing a corresponding second output signal; and

d) automatically calculating a resultant output value based on at least the first output signal and the second output signal by comparing subtracting the second output signal from the first output signal to determine a first quantity of secondary radiation received by the detection apparatus;

wherein calculating the resultant output value further comprises determining a second quantity of radioactive material contained within the subject based on the first quantity of secondary radiation.

38. The method of claim 37, wherein the resultant output value comprises at least one of the first quantity of secondary radiation and the second quantity of radioactive material.