JP2008134200A - Entire celestial sphere-type incident direction detector of radiation, radiation monitoring method, and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an entire celestial sphere-type incident direction detector of radiation housed in an ordinary radiation monitoring post, with the incident direction of radiation defined in terms of a round angle and elevation angle in the horizontal direction. <P>SOLUTION: This entire celestial sphere-type incident direction detector is equipped with a plurality of independent scintillators 11, 12, and 13 of the same material disposed circumferentially relative to incident radiation with at least their parts overlapped, and a conversion part 20 comprising light receiving elements 21, 22, and 23 optically connected to the respective scintillators, wherein the combination of the percentage of radiation directly incident on the respective scintillators with that of radiation indirectly incident on them because of being hidden behind other scintillators is made to change according to an incident direction shown by the round angle and elevation angle. This detector is equipped with a means for comparing ratios r (r1, r2, and r3) calculated by using spectra S1, S2, and S3 obtained from the respective scintillators with a previously stored response function group, and detects the round angle and elevation angle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radiation omnidirectional incidence direction detection apparatus, and a radiation monitoring method and apparatus, and more particularly to radiation or radioactive material from a nuclear facility or the like suitable for accommodation in a normal radiation monitoring post. An omnidirectional incident direction detector for omnidirectional radiation to determine the incident direction of radiation, especially gamma rays, which can detect leakage / dissipation and the approach of radioactive plumes by nuclear tests, etc. The present invention relates to a radiation monitoring method and apparatus using a spherical incident direction detection apparatus.

  Patent Documents 1 to 5 describe conventional techniques for detecting radiation from a horizontal plane direction with respect to the detector.

  Further, Patent Documents 6 and 7 describe conventional techniques that enable the determination of the incident direction from the omnidirectional sphere.

JP 2004-170121 A JP 2004-170122 A JP 2004-170125 A JP 2004-361290 A JP 2006-201086 A JP 2004-170116 A JP 2004-170107 A

  However, in the prior arts of Patent Documents 1 to 5, only a horizontal incident direction can be detected, and a radioactive substance flowing in the atmosphere from a place where the line-of-sight does not work, behind the mountains, the horizon or the horizon, Cannot detect radiation from radioactive plumes contained in scattered materials.

  On the other hand, according to the prior art of Patent Document 6 or 7, it is possible to detect the incident direction from the omnidirectional sphere, but a large number of 25 scintillators for detecting radiation are required, and a scintillator is provided on a spherical outer shell. Because of the attachment, a sufficient volume of the scintillator cannot be secured, so that the detection efficiency of radiation, particularly gamma rays, is low. Since many scintillators are installed, the detector becomes larger, and it is geometrically compatible with ordinary radiation monitoring posts (equipped with a scintillator with a diameter of 7.62 cm (3 inches) and a thickness of 7.62 cm (3 inches)). There was a problem such as missing.

  The present invention has been made to solve the above-mentioned conventional problems, and can detect the incident direction of radiation defined by the circumferential angle and elevation angle in the horizontal direction, and can be accommodated in a normal radiation monitoring post. It is an object of the present invention to provide an omnidirectional incident direction detection device.

  The present invention is an omnidirectional incident direction detection device for detecting the incident direction of radiation, and is an independent plurality of the same material arranged at least partially overlapping the incident radiation in the circumferential direction. Each scintillator and a light receiving element optically bonded to each scintillator, and the combination of the ratio of the radiation directly incident on each scintillator and the radiation incident indirectly in the shadow of the other scintillator is horizontal. The above-mentioned problem is solved by changing according to the incident direction indicated by the circumferential angle and the elevation angle of the direction.

  The number of scintillators is three or more, and it is possible to detect an incident direction indicated by a circumferential angle ranging from 0 degrees to 360 degrees and an elevation angle ranging from 0 degrees to 90 degrees.

  In addition, each scintillator has a fan-shaped cross section, and by combining all the scintillators into a cylinder, it is possible to detect the incident direction indicated by a circumferential angle from 0 degrees to 360 degrees and an elevation angle from 0 degrees to 90 degrees It can be.

  Furthermore, it is possible to make the circumferential resolution uniform by making each scintillator have the same shape.

  Further, a non-destructive inspection around the scintillator is provided by arranging a band-like member (for example, a steel band around 5 mm thick) for adjusting the radiation transmittance from the horizontal direction. It is possible to avoid the influence of leakage of radiation due to the radiation or the increase of the surrounding radiation dose due to the approach of the patient receiving the radioisotope, and to relatively increase the sensitivity in the sky direction.

  In addition, a lid-like member (for example, a plate made of iron and having a thickness of 1 cm) for adjusting the transmittance of radiation from above is disposed on the scintillator, thereby reducing the influence of cosmic rays and the like. Therefore, it is possible to increase the sensitivity in a direction close to the horizontal with a small elevation angle.

  Further, a spectrum analyzing means for analyzing a spectrum generated by each scintillator, a ratio calculating means for obtaining a ratio between the scintillators of the photoelectric absorption peak count value output from the spectrum analyzing means, and a peripheral angle and an elevation angle corresponding to each ratio. A function storage means for storing the function, a function reference means for obtaining a function corresponding to the ratio obtained by the ratio calculation means with reference to the function storage means, and an output means for outputting the obtained peripheral angle and elevation angle And can be provided.

  The present invention also provides a radiation monitoring method using the omnidirectional incident direction detection device.

  The present invention also provides a radiation monitoring apparatus comprising the omnidirectional incident direction detection apparatus.

  According to the present invention, it is possible to specify the incident direction of radiation from the celestial sphere represented by the horizontal circumferential angle and elevation angle, the increase in dose rate is the leakage or dissipation of radiation or radioactive materials from nuclear facilities, Based on the incident direction from the omnidirectional sphere, whether it is the approach of a radioactive plume by a nuclear test, or other causes, such as natural phenomena, the approach of a patient with a radioisotope, or a nearby radiation nondestructive inspection. Judgment can be made quickly, and tracking at the circumferential angle and elevation angle in the horizontal direction is also possible.

  This can greatly contribute to ensuring the safety and security of neighboring residents and the general public.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a detection unit 10 of an embodiment of a radiation omnidirectional incidence direction detection apparatus according to the present invention. At the same time, it defines that the incident direction of radiation from above the celestial sphere is indicated by a horizontal circumferential angle and an elevation angle.

  A scintillator 13 similar to the scintillator 12 similar to the columnar scintillator 11 having the same material and shape but having a horizontal cross section is arranged so as to be shaded with respect to a certain direction. In the figure, reference numeral 14 denotes a case made of, for example, thin aluminum or opaque plastic that transmits radiation.

  The incident direction B of the radiation indicates a circumferential angle of 30 degrees and an elevation angle of 0 degrees with respect to the reference direction of radiation incidence of 0 degrees A. Similarly, the incident direction C of radiation indicates a circumferential angle of 30 degrees and an elevation angle of 60 degrees. Similarly, the incident direction D of radiation represents an indefinite peripheral angle and an elevation angle of 90 degrees, that is, incident from directly above.

  FIG. 2 shows how the spectrum is obtained. In FIG. 2, the horizontal axis indicates energy, and the vertical axis indicates counting. Radiation enters the detection unit 10 including the scintillators 11, 12, and 13, and the scintillators 11, 12, and 13 emit light. The light is electrically amplified by the light receiving elements 21, 22, and 23 of the conversion unit 20, and the spectra S 1, S 2, and S 3 are generated by the multi-channel analyzers (MCAs) 31, 32, and 33 of the spectrum resolving unit 30, respectively. To do.

  For example, considering the case of radiation incident direction C (circumferential angle 30 degrees, elevation angle 60 degrees), the most radiation is directly incident on the scintillator 11. Therefore, a large photoelectric absorption peak p1 is observed in the spectrum S1 generated by the MCA 31. On the other hand, since the scintillators 12 and 13 are partially shaded by the scintillator 11, the directly incident radiation is relatively less, and after reacting with the scintillator 11, the radiation that is incident with a part of energy absorbed. Will be relatively large. Therefore, the photoelectric absorption peaks p2 and p3 of the spectra S2 and S3 generated by the MCAs 32 and 33 become small.

  Further, considering the case of the incident direction B of radiation (circumferential angle 30 degrees, elevation angle 0 degrees), for example, the above phenomenon becomes more prominent.

  On the other hand, for example, in the case of the incident direction D of radiation (circular angle indefinite, elevation angle 90 degrees), direct incidence and indirect incidence on the scintillators 11, 12, 13 are the same conditions. In 33, photoelectric absorption peaks p1, p2, and p3 having the same size are observed.

  Here, a ratio r, which is an index for specifying the incident direction, is defined. The count values of the photoelectric absorption peaks of the spectra S1, S2, and S3 obtained by the MCAs 31, 32, and 33 are p1, p2, and p3, respectively, and the total value of the count values of the three spectrum photoelectric absorption peaks is T (= p1 + p2 + p3). . The ratio r is defined as (r1, r2, r3) where p1 / T is r1, p2 / T is r2, and p3 / T is r3.

  FIG. 3 is an overall view showing the relationship between the ratios r1, r2, r3 (vertical axis) and the horizontal circumferential angle (horizontal axis) in the case of radiation incident direction B (circumferential angle 30 degrees, elevation angle 0 degrees). It is. The relationship between r1 and the surrounding angle is shown in graph B1, the relationship between r2 and the surrounding angle is shown in graph B2, and the relationship between r3 and the surrounding angle is shown in graph B3.

  FIG. 4 is an overall view showing the relationship between the ratios r1, r2, and r3 and the horizontal circumferential angle in the case of the radiation incident direction C (circular angle 30 degrees, elevation angle 60 degrees). The relationship between r1 and the surrounding angle is shown in graph C1, the relationship between r2 and the surrounding angle is shown in graph C2, and the relationship between r3 and the surrounding angle is shown in graph C3.

  FIG. 5 is an overall view showing the “relationship between the ratios r1, r2, and r3 and the circumferential angle in the horizontal direction” in the case of the radiation incident direction D (circular angle indefinite, elevation angle 90 degrees). The relationship between r1 and the surrounding angle is graph D1, the relationship between r2 and the surrounding angle is graph D2, and the relationship between r3 and the surrounding angle is graph D3. In this case, three graphs overlap.

  FIG. 6 is an overall view showing the relationship between the ratio r1 and the horizontal circumferential angle when the elevation angle is 0 degree, the elevation angle is 60 degrees, and the elevation angle is 90 degrees. When the elevation angle is 0 degree, the same graph B1 as FIG. 3 corresponds to the same graph C1 as FIG. 4 when the elevation angle is 60 degrees, and when the elevation angle is 90 degrees, the same graph D1 as FIG. As can be seen in FIG. 6, as the elevation angle increases, the amplitude of the graph decreases, indicating that it approaches the horizon.

  Here, FIG. 7 is used to show the procedure of detecting the incident direction by the apparatus of the present invention. FIG. 7 shows a flow from the start of measurement (step S100) until the incident direction, that is, the combination of the circumferential angle and the elevation angle, which is a solution, is obtained.

  Radiation is detected by the scintillators 11, 12, and 13 for a predetermined time from the start of measurement in step S 100, and spectra S 1, S 2, and S 3 are generated by the MCAs 31, 32, and 33 (steps S 110, S 120, and S 130).

  From each spectrum S1, S2, S3, the energy of the radiation corresponding to the peak count values p1, p2, p3 and the peak position is obtained by general-purpose spectrum analysis software (steps S140, S150, S160).

  From these values, the ratio r (r1, r2, r3) is calculated (step S170). Ratio matching calculation is performed using the ratio r (step S180).

  The concept of the comparison match calculation will be described with reference to FIG. In FIG. 3, it can be seen that for each ratio r, two circumferential angles always match. Therefore, from all the diagrams showing the “relationship between the ratio and the horizontal circumferential angle” prepared for each predetermined elevation angle in the obtained energy, there are circumferential angles that match all the ratios (r1, r2, r3). Search for. The elevation angle and the surrounding angle of the found figure are the solution.

  Actually, a response function group (see FIG. 8) or a numerical table (see FIG. 9) and a ratio r, which is a set of graphs representing the relationship between the circumferential angle and elevation angle created in advance for each energy, and r1, r2, and r3. Are compared, the matching circumferential angle and elevation angle are obtained as solutions, and the incident direction is detected (steps S200 and S210).

  FIG. 8 is an example of a response function group with an energy of 662 keV approximated by a sine wave curve which is the simplest function by experiment. For example, a polynomial can be used in place of the sine wave.

  FIG. 9 is an example of a numerical table created (interpolated if necessary) using the response function group of FIG.

  A configuration example of the apparatus described above is shown in FIG.

  This apparatus includes a spectrum analyzing means 30 for analyzing a spectrum generated in each scintillator 11, 12, 13 of the detection unit 10 and converted into an electric signal by each light receiving element 21, 22, 23 of the conversion unit 20, and the spectrum Ratio calculation means 40 for obtaining the ratio between the scintillators of the photoelectric absorption peak count value output from the analysis unit 30, a function storage means 50 for storing a function composed of a circumferential angle and an elevation angle corresponding to each ratio, and the function storage means 50, a function reference means 60 for obtaining a function corresponding to the ratios r1, r2, and r3 obtained by the ratio calculation means 40, and an output means 70 for outputting the obtained peripheral angle and elevation angle. It consists of a CPU, ROM, RAM, interface and software.

  An embodiment of the above-described radiation omnidirectional incidence direction detection apparatus of the present invention will be described.

  The scintillators 11, 12, and 13 of FIG. 1 were made of a material of sodium iodide NaI (Tl), and had a sector shape with a radius of 37.5 mm and an apex angle of 120 degrees, and a height of 75 mm. These were combined into a cylinder to form the detection unit 10. The detection unit 10 was coupled to the conversion unit 20, and electric signals were transmitted to the MCAs 31, 32, and 33, and spectra S1, S2, and S3 were obtained.

  Using general-purpose spectrum analysis software stored in the HDD (RAM), peak count values p1, p2, p3 and energy of each spectrum S1, S2, S3 were obtained. The ratio r (0.463, 0.204, 0.332) was obtained using the count value p1, p2, p3 of each peak and the total value T of the count values of each peak. At the same time, 622 keV was obtained as energy. The response function group of FIG. 8 which is a set of graphs representing the relationship between the circumferential angle, the elevation angle, and the ratios r1, r2, and r3, which are created in advance for each energy and stored in the HDD or ROM, and temporarily stored in the RAM The ratio r (0.463, 0.204, 0.332) was calculated to match, and an output with a peripheral angle of 30 degrees and an elevation angle of 0 degrees was obtained from the interface.

  In the same manner as in Example 1, general-purpose spectrum analysis software was used to determine the peak count values p1, p2, p3 and energy of each spectrum S1, S2, S3. The ratio r (0.398, 0.269, 0.332) was obtained using the count value p1, p2, p3 of each peak and the total value T of the count values of each peak. At the same time, 622 keV was obtained as energy. The response function group and the ratio r (0.398, 0.269, 0.332) in FIG. 8 which is a set of graphs representing the relationship between the circumferential angle, the elevation angle, and the ratios r1, r2, and r3, created in advance for each energy. When the coincidence calculation was performed, a circumferential angle of 30 degrees and an elevation angle of 60 degrees were obtained.

  In the same manner as in Example 1, general-purpose spectrum analysis software was used to determine the peak count values p1, p2, p3 and energy of each spectrum S1, S2, S3. The ratio r (0.333, 0.333, 0.333) was obtained using the count value p1, p2, p3 of each peak and the total value T of the count values of each peak. At the same time, 622 keV was obtained as energy. The response function group and the ratio r (0.333, 0.333, 0.333) in FIG. 8 which is a set of graphs representing the relationship between the circumferential angle and elevation angle and the ratios r1, r2, and r3 created in advance for each energy. When the coincidence calculation was performed, an indefinite angle and an elevation angle of 90 degrees were obtained.

  The relationship between the response function group and the ratio r in FIG. 8 may be stored in the function storage unit 50 as the calculation formula shown in FIG. 8, but the function is stored as the numerical tables 51, 52, and 53 shown in FIG. It is preferable to store the data in the means 50 because the processing speed is increased. In this case, the minimum setting unit of each angle in FIG. 9 is set according to the required detection angle.

  Note that the steps of the circumferential angle and the elevation angle shown in FIGS. 8 and 9 can be changed in consideration of predetermined accuracy by an interpolation method.

In addition, as shown in FIG. 11, when an iron band 15 having a thickness of 5 mm, for example, is wound around the scintillators 11, 12, 13 from a patient receiving X-rays of about 100 keV or a radioisotope by non-destructive inspection in the surrounding area. As shown in FIG. 12 (the vertical axis is the vertical position of the gamma ray incident from the left and the horizontal axis is the horizontal position), the transmitted radiation R ₀ decreases and the horizontal direction This is suitable for grasping the behavior of the radioactive material in the sky.

  Alternatively, as shown in FIG. 13, when an iron lid 16 having a thickness of, for example, 1 cm is disposed on the scintillators 11, 12, and 13, the influence of cosmic rays and the like is reduced, and the horizontal direction with a relatively small elevation angle is obtained. Can increase the sensitivity.

  Further, the material of the belt 15 and the lid 16 is not limited to iron, and other metals such as aluminum can be used. Furthermore, the sensitivity in a specific direction can be increased or decreased by partially changing the thickness or material.

  Further, the shape of the scintillator may be changed in the circumferential direction.

  The output signal output from the output means is not particularly limited, and may be an analog or digital display that can be visually recognized, or an output signal that can communicate with another computer.

  Even if the number of scintillator components increases and the number of peaks increases, the circumferential angle and the elevation angle can be obtained according to the above-described method. For example, in the case of 4 divisions, as shown in FIG. 14, from (r1, r2, r3, r4), “r1 + r2 + r3 + r4 = 1”, any three graphs (of course, 4 may be used), that is, scintillator number −1. The solution is obtained from the graph (response function).

  Also, since the spectrum has energy information, if there are multiple peaks, select the response function group or numerical table corresponding to each peak, and if the same processing is performed, multiple directions can be obtained simultaneously. it can.

  The diameter of the scintillator is preferably 100 mm or more when only gamma rays with a relatively large energy of 1 MeV or more are targeted, and preferably 50 mm or less when targeting a relatively small energy of less than 1 MeV. When the target is 50 KeV to 3 MeV, about 75 mm is preferable. The height is economical from 25 mm to 100 mm.

The figure which defines the detection part and incident direction of the omnidirectional incident direction detection apparatus which concerns on this invention Figure showing spectrum generation The figure which shows the change of ratio r1, r2, r3 in the case of 30 degrees of surrounding angles and 0 degree of elevation angles for demonstrating the principle of this invention Similarly, the figure which shows the change of ratio r1, r2, r3 in the case of 30 degrees of surrounding angles and 60 degrees of elevation angles Similarly, the figure which shows the change of ratio r1, r2, r3 in the case of an indefinite peripheral angle and an elevation angle of 90 degree | times. Similarly, the figure which shows the change of ratio r1 in the case of the elevation angles of 0, 60 and 90 degrees of the scintillator. The flowchart which shows the procedure until the incident direction is obtained in the embodiment of the present invention. The figure which shows the example of the response function group in embodiment of this invention The figure which similarly shows the example of the numerical table The block diagram which shows the structure of embodiment of the omnidirectional incident direction detection apparatus of the radiation which concerns on this invention The perspective view which shows the principal part of a modification Diagram showing the principle of the modification Longitudinal sectional view showing the main part of another modification The figure which shows the change of ratio r1, r2, r3, r4 of the modification of 4 divisions

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Detection part 11, 12, 13 ... Scintillator 14 ... Case 15 ... Band 16 ... Lid 20 ... Conversion part 21, 22, 23 ... Light receiving element 30 ... Spectral cracking means 31, 32, 33 ... Multichannel analyzer (MCA)
40: Ratio calculation means 50 ... Function storage means 51, 52, 53 ... Table 60 ... Function reference means 70 ... Output means

Claims (9)

An incident direction detection device for detecting an incident direction of radiation,
A plurality of independent scintillators of the same material, arranged at least partially overlapping the incident radiation in the circumferential direction;
Each scintillator and a light receiving element optically bonded,
The combination of the radiation directly incident on each scintillator and the proportion of the radiation indirectly incident in the shadow of the other scintillator changes according to the incident direction indicated by the horizontal circumferential angle and elevation angle. An omnidirectional incident direction detector for radiation.   The radiation according to claim 1, wherein the number of the scintillators is three or more, and an incident direction indicated by a circumferential angle ranging from 0 degrees to 360 degrees and an elevation angle ranging from 0 degrees to 90 degrees is detected. Omnidirectional incident direction detector.   3. The omnidirectional incidence direction detection device for radiation according to claim 2, wherein each scintillator has a fan-shaped cross section and becomes a cylinder when all the scintillators are joined.   The omnidirectional incident direction detection device for radiation according to claim 2 or 3, wherein each scintillator has the same shape.   5. A radiation omnidirectional type according to claim 1, wherein a cylindrical member for adjusting the transmittance of radiation from the horizontal direction is disposed around the scintillator. Incident direction detector.   The omnidirectional type of radiation according to any one of claims 1 to 5, wherein a lid-like member for adjusting the transmittance of radiation from above is disposed above the scintillator. Incident direction detector. Spectrum analysis means for analyzing the spectrum generated by each scintillator;
A ratio calculation means for obtaining a ratio between scintillators of the photoelectric absorption peak count value output from the spectrum analysis means;
Function storage means for storing a function composed of a circumferential angle and an elevation angle corresponding to each ratio;
Function reference means for obtaining a function corresponding to the ratio obtained by the ratio calculation means with reference to the function storage means;
Output means for outputting the obtained circumferential angle and elevation angle;
The omnidirectional incident direction detection device for radiation according to any one of claims 1 to 6, further comprising:   A radiation monitoring method using the omnidirectional incident direction detection device according to claim 1.   A radiation monitoring apparatus comprising the omnidirectional incident direction detection device according to claim 1.

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