WO2008082389A1

WO2008082389A1 - Personal radiation detector with directional capability

Info

Publication number: WO2008082389A1
Application number: PCT/US2006/049589
Authority: WO
Inventors: Andrew J. Zillner; Gregory A. Johnson
Original assignee: Pratt and Whitney Rocketdyne Inc
Current assignee: Aerojet Rocketdyne of DE Inc
Priority date: 2006-12-28
Filing date: 2006-12-28
Publication date: 2008-07-10
Anticipated expiration: 2009-06-28

Abstract

A portable, directional radiation detector includes a radiation detector that is positioned proximate a person's body. The user's body shields the radiation detector from radiation in at least one direction, thereby providing directionality to the radiation detector. The detector may be clipped to or strapped around any part of the body, such as the chest, waist, limb or ankle. It can also be clipped or straped to the head or a hat. Multiple directional detectors can be used to triangulate the position of a radiation source.

Description

PERSONAL RADIATION DETECTOR WITH DIRECTIONAL CAPABILITY

BACKGROUND OF THE INVENTION

Radiation detectors are used to detect the presence of radioactive material. The classic Geiger counter (or Geiger-Muller counter) typically consists of a metal tube with a glass window at one end. The tube is sealed, with a wire running along the length of the tube, and filled with an inert gas, like argon. More recently, solid state radiation detectors using crystals of germanium, silicon and cadmium telluride have been developed. Solid state radiation detectors have the advantage of being smaller and consuming less power than radiation detectors like the Geiger counter.

It is often desirable to determine the location of a source of radioactivity, and various techniques have been used to make radiation detectors that can identify the direction from which the radiation originates. For example, U.S. Patent No. 3,454,770 shows a radiation detector for battlefield use that is placed in the barrel of a tank's gun. The barrel shields radiation from all sides except the opening of the gun. U.S. Patent No. 3,942,009 discloses a radiation detector with a honeycomb- like panel in front of it. The material of the panel absorbs radiation and thereby restricts the viewing angle of the detector. The invention disclosed in U.S. Patent No. 5,665,970 sandwiches two materials with different atomic numbers around a radiation detector. It uses the difference in the count rate of photo-Compton electrons in the two materials to calculate the direction from which the radiation originates.

Another way to provide directionality of a radiation detector is to surround the radiation detector with shielding, allowing radiation to enter the detector through a small, unshielded opening. Such radiation shielding, however, can be quite heavy and bulky. A personal, portable radiation detector should be small, light and easy to transport. However, it is difficult to build small, lightweight radiation detectors. The detectors themselves can be large and heavy. Radiation detectors need a power supply, and batteries will add to their weight. Smaller, lighter solid state detectors present problems as well. The germanium crystals of a germanium-based radiation detector, for instance, must be cooled to very low temperatures with liquid nitrogen. This sort of cooling apparatus also adds to the bulk and weight of the radiation detector.

There is a particular need for a portable personal radiation detector in the area of civil defense. For example, a small portable personal radiation detector can be used to search luggage and backpacks at airports or the trunks of cars that border checkpoints. Also, terrorists may attempt to hide a small nuclear weapon in the trunk of a car or some other location before it is detonated. Even more portable are "dirty bombs," which are made by surrounding conventional explosives with radioactive material. Upon detonating the explosives, the radioactive material is spread over a large area.

If civil defense authorities are aware that a weapon that includes radioactive material is in a certain area, a portable personal radiation detector with directional capability may allow them to locate the weapon before it detonates. After an explosion involving radioactive materials, such as a dirty bomb, civil defense authorities could use portable personal radiation detectors with directional capability to locate radioactive residue that must be removed. Thus, there is a need for a small, portable personal radiation detector with directional capability. Adding directional capability to the radiation detector, however, should not increase its size or weight, or at least minimize the added bulk. In addition, if the device is to be used in the field by civil defense authorities, the directional capabilities of the radiation detector should be simple and easy to use.

BRIEF SUMMARY OF THE INVENTION

The present invention is a portable personal radiation detector with directional capability. A conventional radiation detector is placed on a user's body and the user's body shields the detector from radiation from at least one direction. Two or more detectors can also be used in combination to provide additional directional capability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a first embodiment of the invention. FIG. 2 shows the invention of FIG. 1 placed in exemplary locations on a user.

FIG. 3 shows a second embodiment of the invention that utilizes additional radiation shielding. FIG. 4 shows multiple radiation detectors according to the invention used in combination to provide additional directional capability.

DETAILED DESCRIPTION

FIG. 1 shows an embodiment of the invention. Radiation detector

100 is a conventional radiation detector that is small enough and light enough to be carried by a person. Radiation detector 100 is placed somewhere on the body of person 110. For example, in FIG. 1 radiation detector 100 is located on the chest of person 110. In practice, radiation detector 100 might be connected to a lanyard that is worn around the neck of person 110, so that the radiation detector hangs in front of chest of person 110. Alternatively, radiation detector 100 may be connected to person 110 in any practical manner, such as a strap, a pin, a clip, a belt, an adhesive, or a Velcro® hook and loop fastener attached to a shirt, vest, jacket, pants, hats, shoes, gloves or other articles worn by person

110, or by any other means by which radiation detector 100 can be supported proximate to person 110.

Radiation is blocked by the human body. Person 110 shields at least one side of radiation detector 100 from a significant amount of radiation. Thus, when person 110 faces a radiation source, radiation detector 100 will have a higher reading than when person 110 faces away from the same radiation source. As a result, radiation detector 100, when used as shown in FIG. 1 , has directional capability. However, adding this directional capability does not add any significant weight to radiation detector 100.

For example, person 110 may be a military or homeland security officer using radiation detector 100. In searching for a source of radiation, such as a hidden nuclear weapon or dirty bomb, person 110 can move about until radiation detector 100 detects some radiation. A stronger reading is obtained by radiation detector 100 when person 110 faces the source of the radiation. Thus, by systematically orienting his body to face in different directions, person 110 will detect a stronger reading when facing the direction of the radiation source. The direction of the stronger reading is the direction of the radioactive source. This will allow person 110 to more quickly and accurately locate the source of radiation than by using a conventional handheld radiation detector.

In FIG. 2, radiation detector 100 is shown in exemplary locations on person 110, such as the chest, head, wrist, waist and leg. The number and location of the detectors is purely exemplary. A person might wear any number of radiation detectors located on any part of his or her body and still fall within the scope of this invention. Radiation detector 110 may be supported proximate to person 110 by a strap, band, lanyard, necklace or other supporting structure. Radiation detector 110 may also be attached to the clothing of person 110, such as a shirt, vest or jacket, or it may be attached to accessories such as a hat or cap. FIG. 3 shows a second embodiment of the invention. In FIG. 2, shielding 130 has been added to one or more sides of radiation detector 100. Shielding 130 shields radiation detector 100 from radiation in additional directions than the body of person 110. Shielding 130 improves the directionality of radiation detector 100 at the cost of adding additional weight to radiation detector 100. Radiation detector 100 is shown as a square by way of example, but in practice it may also be circular, rectangular, or any other shape that is practical. Shielding 130 may be located around some or all of the perimeter or circumference of radiation detector 110. Shielding 130 may also be located on some or all of the front surface or back surface of radiation detector 110.

FIG. 4 shows a method by which two or more portable personal radiation detector with directional capability can be used to locate a radiation source. In FIG. 4, two or more radiation detectors 100 are worn by two people. Radiation detector 100 will provide a higher reading when facing radiation source 150 than when facing away from radiation source 150. By rotating their bodies until they both obtain a strong reading, the two people wearing radiation detector 100 can determine the location of radiation source 150. Although FIG. 4 shows two radiation detectors worn by two people, any number of radiation detectors and any number of people can be used. Alternatively, a single person could use multiple radiation detectors, like one on each wrist, and achieve the same result. People wearing radiation detectors 100 could communicate with each other to compare readings from their detectors, either by speaking to each other directly, or using radios or telephones. Alternatively, radiation detectors 100 could be connected to circuitry and software that allows the radiation detectors to communicate directly using radio, infrared or some other appropriate communication technology.

The invention is a portable personal radiation detector that uses the human body to shield a portion of the radiation detector to achieve directionality. The radiation detector may be positioned on any part of the human body that provides sufficient shielding of the radiation detector. When the detector is facing a radiation source, it will provide a higher reading then when the body blocks the radiation detector from the radiation source. In addition, multiple radiation detectors can be used to triangulate the source of radiation.

Although the present invention has been described with reference to the preferred embodiment, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

CLAIMS:

1. A portable directional radiation detector comprising: a radiation detector; means to position the radiation detector proximate a human body so that the body shields the radiation detector from radiation in at least one direction.

2. The portable radiation detector of claim 1 wherein the means to position is selected from the group consisting of a strap, a lanyard, a hook and loop fastener, a clip, a belt, and an adhesive.

3. The portable radiation detector of claim 1 wherein the human body has a torso and the radiation detector is proximate the torso.

4. The portable radiation detector of claim 1 wherein the human body has an arm and the radiation detector is proximate the arm.

5. The portable radiation detector of claim 1 wherein the human body has a leg and the radiation detector is proximate the leg.

6. The portable radiation detector of claim 1 wherein the human body has a head and the radiation detector is proximate the head.

7. The portable radiation detector of claim 1 wherein the human body has a wrist and the radiation detector is proximate the wrist.

8. The portable radiation detector of claim 1 further comprising: the radiation detector having a front, back and at least two sides; shielding to shield the radiation detector from radiation on at least one side of the radiation detector.

9. The portable radiation detector of claim 8 wherein the shielding shields the radiation detector on all of its sides.

10. A portable directional radiation detection system comprising: a radiation detector; a person wearing clothing; a fastener to attach the radiation detector to the person's clothing wherein the person shields the radiation detector from radiation in at least one direction.

1 1. The portable radiation detection system of claim 10 wherein the means to connect is selected from the group consisting of a strap, a necklace, a pin, a hook and loop fastener, a clip, a belt, and an adhesive.

12. The portable radiation detection system of claim 10 wherein the person is wearing a jacket and the radiation detector is connected to the jacket.

13. The portable radiation detection system of claim 10 wherein the person is wearing a hat and the radiation detector is connected to the hat.

14. The portable radiation detection system of claim 10 wherein the person is wearing pants and the radiation detector is connected to the pants.

15. The portable radiation detection system of claim 10 further comprising: the radiation detector having a front, back and at least two sides; shielding to shield the radiation detector from radiation on at least one side of the radiation detector.

16. The portable radiation detection system system of claim 15 wherein the shielding shields the radiation detector on all of its sides.

17. A method for locating a source of radiation, the method comprising: positioning a radiation detector proximate a user's body; partially shielding the radiation detector from radiation with the user's body; detecting radiation with the radiation detector; outputting a signal from the radiation detector that is proportional to the quantity of radiation detected; rotating the user's body in the direction of the highest output signal.

18. The portable radiation detector of claim 17 further comprising: the radiation detector having a front, back and at least two sides; shielding to shield the radiation detector from radiation on at least one side of the radiation detector wherein the shielding improves the directionality of the radiation detector.

19. The method of claim 17 further comprising: positioning a second radiation detector proximate a second user's body; partially shielding the second radiation detector from radiation with the second user's body; detecting radiation with the second radiation detector; outputting a second signal from the second radiation detector that is a function of the quantity of radiation detected; rotating the second user's body in the direction of the highest second output signal; and comparing the first and second output signals to locate the source of radiation.

20. The method of claim 19 wherein the first and second signals are compared by the first and second users.

21. The method of claim 19 wherein the first and second signals are compared by a computer.