Device and method for the location and identification of a radiation source

Abstract

A handheld device for the location and identification of a radiation source, including: a radiation transparent housing; a radiation locator device disposed within the radiation transparent housing operable for determining the location of the radiation source, wherein the radiation locator device includes a plurality of gamma detection crystals arranged in a geometric pattern and separated by a gamma shielding material, a plurality of detectors coupled to the plurality of gamma detection crystals, and a processor module coupled to the plurality of detectors; one or more of a neutron detection crystal and a gamma spectroscopy crystal disposed within the radiation transparent housing adjacent to the radiation locator device; and one or more detectors coupled to the one or more of the neutron detection crystal and the gamma spectroscopy crystal and the processor module; wherein the one or more of the neutron detection crystal and the gamma spectroscopy crystal, the one or more detectors, and the processor module are collectively operable for identifying the radiation source.

Claims

1. A handheld device for the location and identification of a radiation source, comprising: a radiation transparent housing; a radiation locator device disposed within the radiation transparent housing operable for determining the location of the radiation source, wherein the radiation locator device comprises a plurality of gamma detection crystals arranged in a geometric pattern and separated by a gamma shielding material, a plurality of detectors coupled to the plurality of gamma detection crystals, and a processor module coupled to the plurality of detectors; one or more of a neutron detection crystal and a gamma spectroscopy crystal disposed within the radiation transparent housing; and one or more detectors coupled to the one or more of the neutron detection crystal and the gamma spectroscopy crystal and the processor module; wherein the one or more of the neutron detection crystal and the gamma spectroscopy crystal, the one or more detectors, and the processor module are collectively operable for identifying the radiation source; and wherein the one or more of the neutron detection crystal and the gamma spectroscopy crystal comprise both a neutron detection crystal and a gamma spectroscopy crystal.

2. The device of claim 1, wherein the neutron detection crystal comprises one or more of a lithium containing chalcopyrite, a lithium elapsolite, a lithium glass, and a lithium doped metal halide.

3. The device of claim 1, wherein the gamma spectroscopy crystal comprises one or more of SrI2, LaBr3, and CeBr3.

4. The device of claim, 1, wherein the gamma spectroscopy crystal is environmentally sealed.

5. The device of claim 1, wherein the one or more detectors comprise one or more photodetectors.

6. The device of claim 1, wherein identifying the radiation source comprises discriminating between a fissile radiation source and a non-fissile radiation source.

7. The device of claim 1, further comprising a display coupled to the processor module operable for displaying the location and identification of the radiation source to a user.

8. A method for the location and identification of a radiation source, comprising: providing a radiation transparent housing; providing a radiation locator device disposed within the radiation transparent housing operable for determining the location of the radiation source, wherein the radiation locator device comprises a plurality of gamma detection crystals arranged in a geometric pattern and separated by a gamma shielding material, a plurality of detectors coupled to the plurality of gamma detection crystals, and a processor module coupled to the plurality of detectors; providing one or more of a neutron detection crystal and a gamma spectroscopy crystal disposed within the radiation transparent housing; and providing one or more detectors coupled to the one or more of the neutron detection crystal and the gamma spectroscopy crystal and the processor module; wherein the one or more of the neutron detection crystal and the gamma spectroscopy crystal, the one or more detectors, and the processor module are collectively operable for identifying the radiation source; and wherein the one or more of the neutron detection crystal and the gamma spectroscopy crystal comprise both a neutron detection crystal and a gamma spectroscopy crystal.

9. The method of claim 8, wherein the neutron detection crystal comprises one or more of a lithium containing chalcopyrite, a lithium elapsolite, a lithium glass, and a lithium doped metal halide.

10. The method of claim 8, wherein the gamma spectroscopy crystal comprises one or more of SrI2, LaBr3, and CeBr3.

11. The method of claim 8, wherein the gamma spectroscopy crystal is environmentally sealed.

12. The method of claim 8, wherein the one or more detectors comprise one or more photodetectors.

13. The method of claim 8, wherein identifying the radiation source comprises discriminating between a fissile radiation source and a non-fissile radiation source.

14. The method of claim 8, further comprising providing a display coupled to the processor module operable for displaying the location and identification of the radiation source to a user.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure is illustrated and described herein with reference to the various drawings, in which like reference numbers are used to denote like device components/method steps, as appropriate, and in which:

(2) FIG. 1 is a schematic diagram illustrating one exemplary embodiment of the handheld hot spot locator of the present disclosure; and

(3) FIG. 2 is a schematic diagram of one exemplary embodiment of the handheld device for the location and identification of a radiation source of the present invention, combining the handheld hot spot locator of FIG. 1 with the capability to discriminate between fissile and non-fissile materials through the use of one or more additional solid state gamma detection crystals, gamma spectroscopy crystals, neutron detection crystals, and/or photodetectors.

DETAILED DESCRIPTION OF THE DISCLOSURE

(4) Again, the handheld device for the location and identification of a radiation source of the present invention combines a handheld hot spot locator with the capability to discriminate between fissile and non-fissile materials through the use of one or more additional solid state gamma detection crystals, gamma spectroscopy crystals, neutron detection crystals, and/or photodetectors.

(5) Referring now specifically to FIG. 1, in one exemplary embodiment, the hot spot locator (described in detail in SL 24520 to Petrovic, incorporated in full by reference herein) locates a radiation source 1 emitting gamma radiation 2 towards the locator via a gamma radiation transparent housing 3 encompassing a plurality of gamma detection crystals 4. As is shown, four low resolution pillar shaped crystals 4 (2210 cm each, for example) are disposed at the opposed edges of a cube structure with a lead cross structure 5 filling the spaces between them, such that all directions are simultaneously monitored. The lead cross structure 5 provides gamma shielding, such that there is a differential response on each crystal 4 based on the direction of the radiation source 1. A proprietary data analysis and triangulation algorithm is implemented in a series of processors 6 and 7 coupled to a plurality of photodetectors 8 associated with the plurality of crystals 4. This provides gamma radiation detection with a full 4pi coverage area.

(6) Referring now specifically to FIG. 2, in one exemplary embodiment, for radiation source identification, as well as location, a room temperature gamma detection crystal 9 is also disposed within the housing 3, as well as the crystals 4 described herein above. To determine whether or not the radiation source 1 is fissile, this additional crystal 9 should be a solid state, gamma insensitive neutron detection crystal, such as a lithium containing chalcopyrite. This additional crystal 9 allows the gamma rays 2 of fissile material to be differentiated from gamma rays of non-fissile isotopes with similar energies. For simple identification, a 3-10% energy resolution gamma detecting scintillator, such as SrI2, LaBr3, or CeBr3, will suffice. An appropriate photodetector 11, such as SiPM or APD, is coupled to the additional crystal 9, as well as the processor(s) 6 and 7.

(7) More specifically, in a gamma location and gamma spectroscopy application, the locator is coupled with an additional gamma spectroscopy crystal 10. The gamma spectroscopy crystal 10 could be Srl2, LaBr3, CeBr3, or another similar room temperature, solid state, scintillating detection crystal. Preferably the gamma spectroscopy crystal 10 is encapsulated to protect it from reacting with the environment. The gamma spectroscopy crystal 10 is optically coupled to a SiPM, APD, or the like, which is connected to the electronic read-out chain 6 and 7 that includes a multichannel analyzer, for example.

(8) The addition of spectroscopic capabilities improves the angular response of the device and its dose rate determination accuracy. This is because there is the possibility of compensation for interaction differences at different gamma ray energies. Roughly 2-3% energy resolution is achieved.

(9) The addition of this spectroscopy functionality does not significantly affect the size of the locator, and all additional and necessary components fit into the original locator form factor.

(10) In a gamma location and neutron detection application, the object is to locate fissile materials, or differentiate between gamma sources that are fissile and those that are not (Pu vs. medical I-131, for example). Neutron detection primarily involves thermal neutron counting as an indication of a radiation source 1 that emits neutrons.

(11) The additional solid state neutron detection crystal 9 is coupled to a solid state photodetector 11, such as a SiPM or APD. A solid state neutron detection medium is required to achieve sufficient neutron absorber density within a portable handheld form factor. 6LilnSe2 or similar gamma insensitive thermal neutron scintillators are ideal for this embodiment.

(12) The output is generated via a pulse height discriminator in counting mode, within the digital circuitry 6 and 7. Without using gamma spectroscopy, this version of the device can locate radiation, primarily based on the gamma signature, and indicate the presence of a neutron emitting isotope (i.e., fissile material).

(13) In a gamma location, gamma spectroscopy, and neutron detection application, relatively large areas can be surveyed to find radioactive sources 1 and contamination quickly. Once a source of gamma radiation 1 is located, it is important to accurately identify the isotope causing the ionizing radiation in order to respond to its presence appropriately. This can be done with a series of gamma spectroscopy devices 10 and detection scintillators 11; however, each detection material has a unique detection efficiency, sensitivity (i.e., light yield), and energy resolution.

(14) Identification capabilities are specifically limited by the inherent energy resolution of the detecting media. CsI(TI) and NaI(TI) reach an overall energy resolution just below 7% at 662 keV (Cs-137), which is insufficient for most applications of gamma spectroscopy.

(15) However, using a gamma spectroscopy crystal 10, such as SrI2, LaBr3, CeBr3, or another similar gamma scintillator, allows spectroscopic resolution to reach 2-3% at 662 KeV. At this gamma energy resolution, sensitivity and selectivity of radiation detection devices become sufficient for most handheld applications.

(16) One special case is the search for fissile materials. Fissile materials emit a number of gamma ray energies and these energies often overlap with other isotopes, most of which are not a threat. It is particularly important to differentiate and identify fissile material radiation from other isotopes. Gamma ray spectrometers, such as high purity Germanium (HPGe) or CdZnTe, which offer less than 1% energy resolution at 662 keV, are commonly used for this purpose. These spectrometers are, however, expensive and less portable.

(17) In this version, employment of a medium resolution gamma spectrometer 10 and a neutron detection crystal 9 provide the same level of identification as the less portable spectrometers. As an example, medical iodine and fissile plutonium have gamma emissions with such similar energies that HPGe energy resolution is needed to distinguish them. Plutonium, however, emits neutrons, while medical iodine does not. Therefore, the combination of a gamma spectrometer and a neutron detector effectively provides identification without the need for ultra-high gamma spectroscopic resolution.

(18) The device is designed to fit into the current locator form factor, with the neutron detection crystals 9 and/or gamma spectroscopy crystals 10, photodetectors 11, and optional circuity all placed either above or below the central location detection block. This circuitry integrates into the detection architecture. Results are displayed on the hot spot locator LCD, for example.

(19) Although the present disclosure is illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the present invention, are contemplated thereby, and are intended to be covered by the following non-limiting claims.