RADIATION PROBE SYSTEM AND METHOD

• US 20160011320A1
• Filed: 03/02/2015
• Published: 01/14/2016
• Est. Priority Date: 06/13/2014
• Status: Active Grant

• Current Assignee: Mirion Technologies Incorporated (American Capital Limited)
• Original Assignee: Canberra France SAS (American Capital Limited)
• Inventors: Dupont, Archibald, Ulmann, Adrien Gallozzi, Meyer, Frdric, Menaa, Nabil, Ducoux, Xavier
• Granted Patent: US 9,689,991 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01T 1/16 Measuring radiation intensity G01T1/29 takes precedence ; self-powered detectors G01T3/006; using an ionisation chamber filled with a liquid or solid, e.g. frozen liquid, dielectric G01T3/008
• CPC Class Codes: G01T 1/169 Exploration, location of contaminated surface areas

Abstract

A radiation probe system and method incorporating adaptive gamma radiation background subtraction for enhanced radiation detection capability is disclosed. The system and method are generally applicable to radiation “frisking” applications in which the contamination area may have high gamma radiation background levels that normally would result in loss of contamination radiation detection accuracy. Readings from a background radiation detector (BRD) are subtracted from a contamination radiation detector (CRD) to determine a count rate solely associated with contamination. A background subtraction factor (BSF) is used to scale the BRD subtraction and is automatically adjusted based on environmental conditions. A smoothing algorithm is used to increase/decrease the BRD and/or CRD acquisition times to account for signal variations in BRD/CRD measurement readings. The system and method provide for lower limit of detection (LLD) radiation levels that are below that of conventional radiation detectors.

Claims

1. A radiation probe system comprising:

(a) background radiation detector (BRD);

(b) contamination radiation detector (CRD);

(c) proximity sensor (PRS);

(d) operator audible alarm (OAA);

(e) operator visual indicator (OVI);

(f) computing control device (CCD); and

(g) radiation probe enclosure (RPE);

wherein

said RPE is configured to mechanically couple said BRD, said CRD, said PRS, and said CCD in said RPE;

said BRD is positioned behind said CRD such that gamma radiation external to said RPE first passes through said CRD before detection by said BRD;

said PRS is configured to determine the proximity of a radiation source to said RPE;

said BRD is configured to detect gamma radiation from said radiation source;

said CRD is configured to detect alpha, beta, and gamma radiation from said radiation source;

said CCD is configured to read background radiation counts (BRC) from said BRD;

said CCD is configured to read contamination radiation counts (CRC) from said CRD;

said CCD is configured to calculate a radiation background count (RBC) by processing said BRC to estimate static background gamma radiation;

said CCD is configured to calculate a background subtraction factor (BSF) based on said RBC;

said CCD is configured to calculate a net measured radiation (NMR) value by subtracting from said CRC the product of said RBC and said BSF;

said CCD is configured to periodically perform a coherence test of said NMR to determine the statistical correctness of said BSF;

said CCD is configured to calculate a radiation detection threshold (RDT) based on said RBC; and

said CCD is configured to activate said OAA and said OVI based on the values of said NMR, said RDT, and a predetermined alarm threshold value (ATV).

2. The radiation probe system of claim 1 wherein said PRS is configured to have an object detection range of at least 8 cm.

3. The radiation probe system of claim 1 wherein said BSF is recalculated with a sample frequency in the range of 0.1 seconds to 2.0 seconds.

4. The radiation probe system of claim 1 wherein said BSF is recalculated with a sample frequency of 0.25 seconds.

5. The radiation probe system of claim 1 wherein said RDT is calculated by multiplying said BRC value by a constant.

6. The radiation probe system of claim 1 wherein said BSF is subject to a correction of ±

0.1 if said NMR value is beyond the range of [−

0.9;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

7. The radiation probe system of claim 1 wherein said BSF is subject to a correction of ±

0.01 if said NMR value is beyond the range of [−

0.9;

−

0.6] or [+0.6;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

8. The radiation probe system of claim 1 wherein said BSF is corrected only if the measurement time associated with said BRC or said CRC is equal to or greater than 5 seconds.

9. The radiation probe system of claim 1 wherein said CCD is configured to periodically test said BSF for correction, and if correction is determined to be necessary, adjusting said BSF by a step value within the range of 0.01 to 0.10.

10. The radiation probe system of claim 1 wherein said OAA is configured to operate with a DT hysteresis value (DHV) in the range of 5% to 25% of said ATV.

11. A radiation probe method, said method operating in conjunction with a radiation probe system comprising:

(a) background radiation detector (BRD);

(b) contamination radiation detector (CRD);

(c) proximity sensor (PRS);

(d) operator audible alarm (OAA);

(e) operator visual indicator (OVI);

(f) computing control device (CCD); and

(g) radiation probe enclosure (RPE);

wherein

said RPE is configured to mechanically couple said BRD, said CRD, said PRS, and said CCD in said RPE; and

said BRD is positioned behind said CRD such that gamma radiation external to said RPE first passes through said CRD before detection by said BRD;

wherein said method comprises the steps of;

(1) with said PRS, determining the proximity of a radiation source to said RPE;

(2) with said BRD, detecting gamma radiation from said radiation source;

(3) with said CRD, detecting alpha, beta, and gamma radiation from said radiation source;

(4) with said CCD, reading background radiation counts (BRC) from said BRD;

(5) with said CCD, reading contamination radiation counts (CRC) from said CRD;

(6) with said CCD, calculating a radiation background count (RBC) by processing said BRC to estimate static background gamma radiation;

(7) with said CCD, calculating a background subtraction factor (BSF) based on said RBC;

(8) with said CCD, calculating a net measured radiation (NMR) value by subtracting from said CRC the product of said RBC and said BSF;

(9) with said CCD, periodically performing a coherence test of said NMR to determine the statistical correctness of said BSF;

(10) with said CCD, calculating a radiation detection threshold (RDT) based on said RBC; and

(11) with said CCD, activating said OAA and said OVI based on the values of said NMR, said RDT, and a predetermined alarm threshold value (ATV).

12. The radiation probe method of claim 11 wherein said PRS is configured to have an object detection range of at least 8 cm.

13. The radiation probe method of claim 11 wherein said BSF is recalculated with a sample frequency in the range of 0.1 seconds to 2.0 seconds.

14. The radiation probe method of claim 11 wherein said BSF is recalculated with a sample frequency of 0.25 seconds.

15. The radiation probe method of claim 11 wherein said RDT is calculated by multiplying said BRC value by a constant.

16. The radiation probe method of claim 11 wherein said BSF is subject to a correction of ±

0.1 if said NMR value is beyond the range of [−

0.9;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

17. The radiation probe method of claim 11 wherein said BSF is subject to a correction of ±

0.01 if said NMR value is beyond the range of [−

0.9;

−

0.6] or [+0.6;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

18. The radiation probe method of claim 11 wherein said BSF is corrected only if the measurement time associated with said BRC or said CRC is equal to or greater than 5 seconds.

19. The radiation probe method of claim 11 wherein said CCD is configured to periodically test said BSF for correction, and if correction is determined to be necessary, adjusting said BSF by a step value within the range of 0.01 to 0.10.

20. The radiation probe method of claim 11 wherein said OAA is configured to operate with a DT hysteresis value (DHV) in the range of 5% to 25% of said ATV.

21. A tangible non-transitory computer usable medium having computer-readable program code means embodied thereon comprising a radiation probe method, said method operating in conjunction with a radiation probe system comprising:

(a) background radiation detector (BRD);

(b) contamination radiation detector (CRD);

(c) proximity sensor (PRS);

(d) operator audible alarm (OAA);

(e) operator visual indicator (OVI);

(f) computing control device (CCD); and

(g) radiation probe enclosure (RPE);

wherein

said RPE is configured to mechanically couple said BRD, said CRD, said PRS, and said CCD in said RPE; and

said BRD is positioned behind said CRD such that gamma radiation external to said RPE first passes through said CRD before detection by said BRD;

wherein said method comprises the steps of;

(1) with said PRS, determining the proximity of a radiation source to said RPE;

(2) with said BRD, detecting gamma radiation from said radiation source;

(3) with said CRD, detecting alpha, beta, and gamma radiation from said radiation source;

(4) with said CCD, reading background radiation counts (BRC) from said BRD;

(5) with said CCD, reading contamination radiation counts (CRC) from said CRD;

(6) with said CCD, calculating a radiation background count (RBC) by processing said BRC to estimate static background gamma radiation;

(7) with said CCD, calculating a background subtraction factor (BSF) based on said RBC;

(8) with said CCD, calculating a net measured radiation (NMR) value by subtracting from said CRC the product of said RBC and said BSF;

(9) with said CCD, periodically performing a coherence test of said NMR to determine the statistical correctness of said BSF;

(10) with said CCD, calculating a radiation detection threshold (RDT) based on said RBC; and

(11) with said CCD, activating said OAA and said OVI based on the values of said NMR, said RDT, and a predetermined alarm threshold value (ATV).

22. The computer usable medium of claim 21 wherein said PRS is configured to have an object detection range of at least 8 cm.

23. The computer usable medium of claim 21 wherein said BSF is recalculated with a sample frequency in the range of 0.1 seconds to 2.0 seconds.

24. The computer usable medium of claim 21 wherein said BSF is recalculated with a sample frequency of 0.25 seconds.

25. The computer usable medium of claim 21 wherein said RDT is calculated by multiplying said BRC value by a constant.

26. The computer usable medium of claim 21 wherein said BSF is subject to a correction of ±

0.1 if said NMR value is beyond the range of [−

0.9;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

27. The computer usable medium of claim 21 wherein said BSF is subject to a correction of ±

0.01 if said NMR value is beyond the range of [−

0.9;

−

0.6] or [+0.6;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

28. The computer usable medium of claim 21 wherein said BSF is corrected only if the measurement time associated with said BRC or said CRC is equal to or greater than 5 seconds.

29. The computer usable medium of claim 21 wherein said CCD is configured to periodically test said BSF for correction, and if correction is determined to be necessary, adjusting said BSF by a step value within the range of 0.01 to 0.10.

30. The computer usable medium of claim 21 wherein said OAA is configured to operate with a DT hysteresis value (DHV) in the range of 5% to 25% of said ATV.

31. A radiation probe system comprising:

(a) background radiation detector (BRD);

(b) contamination radiation detector (CRD);

(c) proximity sensor (PRS);

(d) operator audible alarm (OAA);

(e) operator visual indicator (OVI);

(f) computing control device (CCD); and

(g) radiation probe enclosure (RPE);

wherein

said RPE is configured to mechanically couple said BRD, said CRD, said PRS, and said CCD in said RPE;

said BRD is positioned proximal to said CRD;

said PRS is configured to determine the proximity of a radiation source to said RPE;

said BRD is configured to detect gamma radiation from said radiation source;

said CRD is configured to detect alpha, beta, and gamma radiation from said radiation source;

said CCD is configured to read background radiation counts (BRC) from said BRD;

said CCD is configured to read contamination radiation counts (CRC) from said CRD;

said CCD is configured to calculate a radiation background count (RBC) by processing said BRC to estimate static background gamma radiation;

said CCD is configured to calculate a background subtraction factor (BSF) based on said RBC;

said CCD is configured to calculate a net measured radiation (NMR) value by subtracting from said CRC the product of said RBC and said BSF;

said CCD is configured to periodically perform a coherence test of said NMR to determine the statistical correctness of said BSF;

said CCD is configured to calculate a radiation detection threshold (RDT) based on said RBC; and

said CCD is configured to activate said OAA and said OVI based on the values of said NMR, said RDT, and a predetermined alarm threshold value (ATV).

32. The radiation probe system of claim 31 wherein said PRS is configured to have an object detection range of at least 8 cm.

33. The radiation probe system of claim 31 wherein said BSF is recalculated with a sample frequency in the range of 0.1 seconds to 2.0 seconds.

34. The radiation probe system of claim 31 wherein said BSF is recalculated with a sample frequency of 0.25 seconds.

35. The radiation probe system of claim 31 wherein said RDT is calculated by multiplying said BRC value by a constant.

36. The radiation probe system of claim 31 wherein said BSF is subject to a correction of ±

0.1 if said NMR value is beyond the range of [−

0.9;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

37. The radiation probe system of claim 31 wherein said BSF is subject to a correction of ±

0.01 if said NMR value is beyond the range of [−

0.9;

−

0.6] or [+0.6;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

38. The radiation probe system of claim 31 wherein said BSF is corrected only if the measurement time associated with said BRC or said CRC is equal to or greater than 5 seconds.

39. The radiation probe system of claim 31 wherein said CCD is configured to periodically test said BSF for correction, and if correction is determined to be necessary, adjusting said BSF by a step value within the range of 0.01 to 0.10.

40. The radiation probe system of claim 31 wherein said OAA is configured to operate with a DT hysteresis value (DHV) in the range of 5% to 25% of said ATV.

41. A radiation probe method, said method operating in conjunction with a radiation probe system comprising:

(a) background radiation detector (BRD);

(b) contamination radiation detector (CRD);

(c) proximity sensor (PRS);

(d) operator audible alarm (OAA);

(e) operator visual indicator (OVI);

(f) computing control device (CCD); and

(g) radiation probe enclosure (RPE);

wherein

said RPE is configured to mechanically couple said BRD, said CRD, said PRS, and said CCD in said RPE; and

said BRD is positioned proximal to said CRD;

wherein said method comprises the steps of;

(1) with said PRS, determining the proximity of a radiation source to said RPE;

(2) with said BRD, detecting gamma radiation from said radiation source;

(3) with said CRD, detecting alpha, beta, and gamma radiation from said radiation source;

(4) with said CCD, reading background radiation counts (BRC) from said BRD;

(5) with said CCD, reading contamination radiation counts (CRC) from said CRD;

(6) with said CCD, calculating a radiation background count (RBC) by processing said BRC to estimate static background gamma radiation;

(7) with said CCD, calculating a background subtraction factor (BSF) based on said RBC;

(8) with said CCD, calculating a net measured radiation (NMR) value by subtracting from said CRC the product of said RBC and said BSF;

(9) with said CCD, periodically performing a coherence test of said NMR to determine the statistical correctness of said BSF;

(10) with said CCD, calculating a radiation detection threshold (RDT) based on said RBC; and

(11) with said CCD, activating said OAA and said OVI based on the values of said NMR, said RDT, and a predetermined alarm threshold value (ATV).

42. The radiation probe method of claim 41 wherein said PRS is configured to have an object detection range of at least 8 cm.

43. The radiation probe method of claim 41 wherein said BSF is recalculated with a sample frequency in the range of 0.1 seconds to 2.0 seconds.

44. The radiation probe method of claim 41 wherein said BSF is recalculated with a sample frequency of 0.25 seconds.

45. The radiation probe method of claim 41 wherein said RDT is calculated by multiplying said BRC value by a constant.

46. The radiation probe method of claim 41 wherein said BSF is subject to a correction of ±

0.1 if said NMR value is beyond the range of [−

0.9;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

47. The radiation probe method of claim 41 wherein said BSF is subject to a correction of ±

0.01 if said NMR value is beyond the range of [−

0.9;

−

0.6] or [+0.6;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

48. The radiation probe method of claim 41 wherein said BSF is corrected only if the measurement time associated with said BRC or said CRC is equal to or greater than 5 seconds.

49. The radiation probe method of claim 41 wherein said CCD is configured to periodically test said BSF for correction, and if correction is determined to be necessary, adjusting said BSF by a step value within the range of 0.01 to 0.10.

50. The radiation probe method of claim 41 wherein said OAA is configured to operate with a DT hysteresis value (DHV) in the range of 5% to 25% of said ATV.

51. A tangible non-transitory computer usable medium having computer-readable program code means embodied thereon comprising a radiation probe method, said method operating in conjunction with a radiation probe system comprising:

(a) background radiation detector (BRD);

(b) contamination radiation detector (CRD);

(c) proximity sensor (PRS);

(d) operator audible alarm (OAA);

(e) operator visual indicator (OVI);

(f) computing control device (CCD); and

(g) radiation probe enclosure (RPE);

wherein

said RPE is configured to mechanically couple said BRD, said CRD, said PRS, and said CCD in said RPE; and

said BRD is positioned proximal to said CRD;

wherein said method comprises the steps of;

(1) with said PRS, determining the proximity of a radiation source to said RPE;

(2) with said BRD, detecting gamma radiation from said radiation source;

(3) with said CRD, detecting alpha, beta, and gamma radiation from said radiation source;

(4) with said CCD, reading background radiation counts (BRC) from said BRD;

(5) with said CCD, reading contamination radiation counts (CRC) from said CRD;

(6) with said CCD, calculating a radiation background count (RBC) by processing said BRC to estimate static background gamma radiation;

(7) with said CCD, calculating a background subtraction factor (BSF) based on said RBC;

(8) with said CCD, calculating a net measured radiation (NMR) value by subtracting from said CRC the product of said RBC and said BSF;

(9) with said CCD, periodically performing a coherence test of said NMR to determine the statistical correctness of said BSF;

(10) with said CCD, calculating a radiation detection threshold (RDT) based on said RBC; and

(11) with said CCD, activating said OAA and said OVI based on the values of said NMR, said RDT, and a predetermined alarm threshold value (ATV).

52. The computer usable medium of claim 51 wherein said PRS is configured to have an object detection range of at least 8 cm.

53. The computer usable medium of claim 51 wherein said BSF is recalculated with a sample frequency in the range of 0.1 seconds to 2.0 seconds.

54. The computer usable medium of claim 51 wherein said BSF is recalculated with a sample frequency of 0.25 seconds.

55. The computer usable medium of claim 51 wherein said RDT is calculated by multiplying said BRC value by a constant.

56. The computer usable medium of claim 51 wherein said BSF is subject to a correction of ±

0.1 if said NMR value is beyond the range of [−

0.9;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

57. The computer usable medium of claim 51 wherein said BSF is subject to a correction of ±

0.01 if said NMR value is beyond the range of [−

0.9;

−

0.6] or [+0.6;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

58. The computer usable medium of claim 51 wherein said BSF is corrected only if the measurement time associated with said BRC or said CRC is equal to or greater than 5 seconds.

59. The computer usable medium of claim 51 wherein said CCD is configured to periodically test said BSF for correction, and if correction is determined to be necessary, adjusting said BSF by a step value within the range of 0.01 to 0.10.

60. The computer usable medium of claim 51 wherein said OAA is configured to operate with a DT hysteresis value (DHV) in the range of 5% to 25% of said ATV.

61. A radiation probe method, said method operating in conjunction with a radiation probe system comprising:

(a) background radiation detector (BRD);

(b) contamination radiation detector (CRD);

(c) proximity sensor (PRS);

(d) operator audible alarm (OAA);

(e) operator visual indicator (OVI); and

(f) computing control device (CCD);

wherein

said BRD is positioned proximal to said CRD;

wherein said method comprises the steps of;

(1) With the CCD, collecting counts from said BRD;

(2) With said CCD, smoothing BRD data using a Radiation Probe Smoothing Algorithm Method with a previous count of said BRD used as input parameters to said smoothing algorithm;

(3) With said CCD, smoothing CRD data using a Radiation Probe Smoothing Algorithm Method with a previous count of said CRD used as input parameters to said smoothing algorithm;

(4) With said CCD, calculating net measured radiation (NMR) values using a background radiation subtraction factor (BSF) K;

(5) With said CCD, performing a coherence test and according to said coherence test estimating a new value of said BSF K;

(6) With said CCD, activating said OAA if said NMR is greater than an alarm threshold value (ATV);

(7) With said CCD, activating said OVI to indicate consistency of radiation detection events; and

(8) Proceeding to step (1) to repeat said BRD and CRD radiation measurements and subsequent determination of said NMR.

62. The radiation probe method of claim 61 wherein said PRS is configured to have an object detection range of at least 8 cm.

63. The radiation probe method of claim 61 wherein said BSF is recalculated with a sample frequency in the range of 0.1 seconds to 2.0 seconds.

64. The radiation probe method of claim 61 wherein said BSF is recalculated with a sample frequency of 0.25 seconds.

65. The radiation probe method of claim 61 wherein a radiation detection threshold (RDT) is calculated based on said BRD data to determine activation of said OAA and said OVI.

66. The radiation probe method of claim 61 wherein said BSF is subject to a correction of ±

0.1 if said NMR value is beyond the range of [−

0.9;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

67. The radiation probe method of claim 61 wherein said BSF is subject to a correction of ±

0.01 if said NMR value is beyond the range of [−

0.9;

−

0.6] or [+0.6;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

68. The radiation probe method of claim 61 wherein said BSF is corrected only if the measurement time associated with said BRC or said CRC is equal to or greater than 5 seconds.

69. The radiation probe method of claim 61 wherein said CCD is configured to periodically test said BSF for correction, and if correction is determined to be necessary, adjusting said BSF by a step value within the range of 0.01 to 0.10.

70. The radiation probe method of claim 61 wherein said OAA is configured to operate with a DT hysteresis value (DHV) in the range of 5% to 25% of said ATV.

71. A tangible non-transitory computer usable medium having computer-readable program code means embodied thereon comprising a radiation probe method, said method operating in conjunction with a radiation probe system comprising:

(a) background radiation detector (BRD);

(b) contamination radiation detector (CRD);

(c) proximity sensor (PRS);

(d) operator audible alarm (OAA);

(e) operator visual indicator (OVI); and

(f) computing control device (CCD);

wherein

said BRD is positioned proximal to said CRD;

wherein said method comprises the steps of;

(1) With the CCD, collecting counts from said BRD;

(2) With said CCD, smoothing BRD data using a Radiation Probe Smoothing Algorithm Method with a previous count of said BRD used as input parameters to said smoothing algorithm;

(3) With said CCD, smoothing CRD data using a Radiation Probe Smoothing Algorithm Method with a previous count of said CRD used as input parameters to said smoothing algorithm;

(4) With said CCD, calculating net measured radiation (NMR) values using a background radiation subtraction factor (BSF) K;

(5) With said CCD, performing a coherence test and according to said coherence test estimating a new value of said BSF K;

(6) With said CCD, activating said OAA if said NMR is greater than an alarm threshold value (ATV);

(7) With said CCD, activating said OVI to indicate consistency of radiation detection events; and

(8) Proceeding to step (1) to repeat said BRD and CRD radiation measurements and subsequent determination of said NMR.

72. The computer usable medium of claim 71 wherein said PRS is configured to have an object detection range of at least 8 cm.

73. The computer usable medium of claim 71 wherein said BSF is recalculated with a sample frequency in the range of 0.1 seconds to 2.0 seconds.

74. The computer usable medium of claim 71 wherein said BSF is recalculated with a sample frequency of 0.25 seconds.

75. The computer usable medium of claim 71 wherein a radiation detection threshold (RDT) is calculated based on said BRD data to determine activation of said OAA and said OVI.

76. The computer usable medium of claim 71 wherein said BSF is subject to a correction of ±

0.1 if said NMR value is beyond the range of [−

0.9;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

77. The computer usable medium of claim 71 wherein said BSF is subject to a correction of ±

0.01 if said NMR value is beyond the range of [−

0.9;

−

0.6] or [+0.6;

+0.9] multiplied by a detection threshold (DT) that is determined by said BSF.

78. The computer usable medium of claim 71 wherein said BSF is corrected only if the measurement time associated with said BRC or said CRC is equal to or greater than 5 seconds.

79. The computer usable medium of claim 71 wherein said CCD is configured to periodically test said BSF for correction, and if correction is determined to be necessary, adjusting said BSF by a step value within the range of 0.01 to 0.10.

80. The computer usable medium of claim 71 wherein said OAA is configured to operate with a DT hysteresis value (DHV) in the range of 5% to 25% of said ATV.