JP2018194401A - Neutron measurement member and radioactivation amount measurement method - Google Patents

Abstract

To provide a neutron measurement member and a radioactivation amount measurement method which can accurately measure the distribution of neutrons.SOLUTION: A neutron measurement member 1 includes: a plurality of radioactivation members 11 made of a metal to be radioactivated by applying a neutron beam; and a fixing part 12 on which the plurality of radioactivation members 11 are fixed at a predetermined interval.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a neutron measuring member and an activation amount measuring method.

  In neutron beam capture therapy, it is necessary to appropriately manage the dose of neutron beam irradiated to the irradiation target position of the irradiated object. Therefore, for example, as described in Patent Document 1, a method of attaching a gold wire for neutron measurement to a target site and estimating the neutron distribution from the activation amount of the gold wire is used.

JP 2004-233168 A

  However, in order to evaluate the neutron distribution, it is necessary to measure the activation amount of each of the plurality of gold wires after arranging the plurality of gold wires at different positions. In an environment where a neutron beam is irradiated, if an attempt is made to accurately place each of the plurality of gold wires at a target position, the amount of work increases.

  The present invention has been made in view of the above, and an object of the present invention is to provide a neutron measuring member and an activation amount measuring method capable of accurately measuring the neutron distribution.

  In order to achieve the above object, a neutron measurement member according to an aspect of the present invention includes a plurality of activation members made of metal that is activated by irradiation with neutron beams, and the plurality of activation members at a predetermined interval. And a fixing part fixed at

  According to the above neutron measurement member, since the plurality of activation members are fixed to the fixed member at a predetermined interval, the radiation is emitted as compared with the case where the plurality of activation members are individually arranged at desired positions. It becomes possible to arrange | position a chemical-ized member appropriately, and it becomes possible to measure the distribution of neutrons accurately.

  Here, the said fixing | fixed part can be made into the aspect which is a sheet-like member which has plasticity.

  As described above, when the fixing part is a sheet-like member having plasticity, the fixing part can be deformed according to the shape of the place to be measured for neutrons, etc. Sound that accurately measures the distribution of neutrons becomes possible.

  Moreover, the activation amount measurement method according to an aspect of the present invention is a method for measuring the activation amount of a neutron measurement member, and includes a plurality of activation members made of metal activated by irradiation with a neutron beam. A step of preparing a neutron measurement member after neutron irradiation, the plurality of activation members being fixed at a predetermined interval, and a plurality of the activation members being fixed at the same interval as the interval at which the activation member is fixed A step of bringing the plurality of activation members of the neutron measurement member into contact with each of the plurality of holes of the gamma ray collimator in which the holes are formed, and being emitted from each of the plurality of activation members, And individually detecting radiation guided through each of the plurality of holes by a radiation detector.

  According to the above-described activation amount measuring method, using a gamma ray collimator in which a plurality of holes are formed at the same interval as the interval at which the plurality of activation members are fixed in the neutron measurement member, The emitted radiation can be detected individually. Therefore, the activation amounts of the plurality of activation members of the neutron measurement member can be individually and accurately measured.

  Moreover, the activation amount measurement method according to an aspect of the present invention is a method for measuring the activation amount of a neutron measurement member, and includes a plurality of activation members made of metal activated by irradiation with a neutron beam. A step of preparing a neutron measuring member after irradiation with neutron radiation, the activating member having one of the plurality of activating members; The one activation member in a state where one activation member of the plurality of activation members of the neutron measurement member is brought into contact with the hole of the shielding member in which a hole corresponding to only the hole is formed. A radiation detector that detects the radiation emitted from each of the light beams and guided through the holes of the shielding member, and the activation member that contacts the holes of the shielding member is different from the one activation member. Change to the activation member To, be released from the other activation member, and a step of detecting by radiation the radiation detector holes and guided in the shielding member.

  According to the above-described activation amount measurement method, one activation member among the plurality of activation members is formed using the shielding member in which the hole corresponding to only one activation member among the activation members is formed. After detecting the radiation emitted from the radiation member, the radiation member that contacts the hole of the shielding member is changed from one member to another member to detect the radiation. By setting it as such a structure, it becomes possible to detect separately the radiation discharge | released from each of several activation member. Therefore, the activation amounts of the plurality of activation members of the neutron measurement member can be individually and accurately measured.

  ADVANTAGE OF THE INVENTION According to this invention, the neutron measurement member and activation amount measurement method which can measure the distribution of neutrons accurately are provided.

It is a figure explaining a neutron measuring member and an activation amount measuring apparatus. It is a figure explaining the activation amount measuring method. It is a figure explaining one Example of the measuring method of activation amount. It is a figure explaining the other Example of the measuring method of activation amount.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a diagram showing a neutron measurement member according to an embodiment of the present invention and an activation amount measurement device used for measuring the activation amount of the neutron measurement member. FIG. 1A is a schematic configuration diagram of the neutron measuring member 1, and FIG. 1B is a schematic configuration diagram of the activation amount measuring device 2.

  The neutron measurement member 1 includes a plurality of activation members 11 and a fixing portion 12 that fixes the plurality of activation members 11. The neutron measuring member 1 is used for measuring the distribution of neutron intensity in an environment irradiated with neutrons such as a neutron capture therapy system. When the neutron measurement member 1 is used in a neutron capture therapy system, for example, it is used for measurement of intensity distribution along the beam axis direction of a device that irradiates a neutron beam N.

  The activation member 11 of the neutron measurement member 1 is made of a metal material that is activated when irradiated with neutrons. Examples of the metal material that is activated when irradiated with neutron beams include gold, iodine, and manganese. Since the activation amount of these metals changes according to the intensity of the irradiated neutron, the intensity of the neutron can be estimated by measuring the activation amount.

  The shape of the some activation member 11 can be made into linear or foil shape, for example. However, each of the activation members 11 has a size and a thickness that do not disturb the neutron field. Specifically, for example, when a gold foil is used as the activation member 11, the activation member 11 can have an area of about 2 mm × 2 mm and a thickness of about 0.5 mm. In addition, when the activation member 11 is too large, measurement accuracy will fall. On the other hand, if the activation member 11 is too small, the detection efficiency decreases. Therefore, the size can be appropriately selected in consideration of the type of metal.

  The activation member 11 is disposed on the fixed portion 12 at a predetermined interval. The interval between the activation members 11 is determined based on the measurement interval of the neutron intensity distribution.

  The fixing portion 12 to which the plurality of activation members 11 are fixed is a sheet-like member made of a material that does not disturb the neutron field. As a material of the fixing portion 12, for example, an acrylic resin or the like can be used, but is not particularly limited. However, if the fixing portion 12 has plasticity, the handleability is improved. In addition, if the fixing portion 12 has plasticity, for example, even if the target position for measuring the intensity distribution of the neutron is arranged in a curved shape, it can be deformed according to the shape. It becomes possible to cope with various measurement conditions.

  The size of the fixed portion 12 is set according to the number and arrangement (interval) of the activation members 11 attached to one neutron measurement member 1. The number of activation members 11 attached to the fixing portion 12 is not particularly limited. Moreover, arrangement | positioning can also be changed suitably. FIG. 1A shows an example in which the activation members 11 are arranged in a row with respect to the fixing portion 12, but a plurality of activation members 11 are two-dimensionally arranged with respect to the sheet-like fixing portion 12. May be.

  Further, the thickness of the fixing portion 12 is not particularly limited, but it is preferable to make the fixing portion 12 thinner in order not to disturb the neutron field.

  The activation member 11 may be fixed to the surface of the fixing portion 12, or may be fixed by sandwiching the activation member 11 with a plurality of sheet-like members, for example. The fixing part 12 only needs to be able to fix the activation member 11 so that the plurality of activation members 11 are held at a predetermined interval, and the method is not particularly limited.

  After calculating the activation amount, when calculating the neutron intensity from the calculation result, the material type (metal type) of the activation member 11 included in the neutron measurement member 1 and the relative position (between the activation members 11). ) And the mass of each of the activation members 11 is required. However, the relative positions and masses of the plurality of activation members 11 may differ depending on the neutron measurement member 1. Therefore, the neutron measuring member 1 has the above information recorded in advance for each neutron measuring member 1 before use. When calculating the neutron intensity based on the activation amount, the neutron amount is calculated in each activation member 11 using information recorded in advance for each neutron measurement member 1. The above-mentioned information (material type, relative position, and mass) of the neutron measuring member 1 for each neutron measuring member 1 is previously associated with information (for example, a serial number) that individually specifies the neutron measuring member 1. It can be set as a database and managed.

  Next, the activation amount measuring apparatus 2 that measures the activation amount related to the activation member 11 of the neutron measurement member 1 will be described. As shown in FIG. 1B, the activation amount measuring apparatus 2 includes a gamma ray absolute value measuring device 21, a gamma ray individual measuring device 22 (radiation detector), and a measured value calibration unit 23. The functional unit included in the activation amount measuring device is configured by combining a plurality of devices (measuring instruments).

  The gamma ray absolute value measuring device 21 has a function of measuring the absolute amount of gamma rays generated with the activation of the plurality of activation members 11 of the neutron measurement member 1. A known gamma ray detector can be used as the gamma ray absolute value measuring device 21.

  The gamma ray individual measuring device 22 has a function of measuring the dose of gamma rays generated along with the activation of the plurality of activation members 11 of the neutron measurement member 1 for each activation member 11. Although the details of the method of individually measuring each activation member 11 will be described later, the measurement is performed while distinguishing the gamma rays from the activation member 11 to be measured and the gamma rays from the adjacent activation member 11.

  The measurement value calibration unit 23 calibrates the gamma ray dose for each activation member 11 measured by the gamma ray individual measuring device 22 with the gamma ray dose measured by the gamma ray absolute value measurement device 21, and for each activation member 11. It has a function of calculating the dose of gamma rays, that is, the activation amount for each activation member 11. Since the gamma ray dose for each activation member 11 by the individual gamma ray measuring device 22 is measured separately from the gamma rays from the adjacent activation member 11 as described above, the numerical value may be small. Therefore, the measurement value calibration unit 23 calibrates using the gamma ray dose measured by the gamma ray absolute value measuring device 21, thereby calculating the gamma ray dose for each activation member 11 more accurately. The measurement value calibration unit 23 can be configured as an electronic control unit including a CPU, a ROM, a RAM, and the like.

  The absolute value measurement by the gamma ray absolute value measuring device 21 and the calibration by the measurement value calibration unit 23 may not be performed. Even in such a case, the activation amount can be calculated by measuring the dose of gamma rays for each activation member 11.

  Next, the activation amount measuring method will be described with reference to FIG. First, the neutron measuring member 1 is placed in the region to be measured (S01). At this time, each of the plurality of activation members 11 is arranged at a desired position by appropriately arranging the neutron measurement member 1 at a desired location. Next, the neutron beam is irradiated to activate each activation member 11 of the neutron measurement member 1 (S02). Thereby, the neutron measurement member 1 in which each activation member 11 after the neutron irradiation is activated is prepared.

  Thereafter, with respect to the neutron measuring member 1, the absolute value of gamma rays generated along with the plurality of activation members 11 is measured by the gamma ray absolute value measuring device 21 (S 03), and the gamma rays of each of the plurality of activation members 11 are individually detected. Measurement by the measuring instrument 22 (S04) is performed. These measurements (S02, S03) may be performed simultaneously or individually. Further, the measurement order is not particularly limited.

  With reference to FIG. 3, an example of measurement by the gamma ray absolute value measuring device 21 and measurement by the gamma ray individual measuring device 22 will be described.

  In the embodiment shown in FIG. 3, the measurement by the gamma ray absolute value measurement device 21 and the measurement by the gamma ray individual measurement device 22 are simultaneously performed on both surfaces of the neutron measurement member 1. First, below the figure of the neutron measuring member 1, gamma rays from the respective activation members 11 of the neutron measuring member 1 are measured by a gamma ray detector as the gamma ray absolute value measuring device 21. Since the gamma rays generated in the activation member 11 are isotropically emitted, the gamma ray absolute value measuring device 21 provided below the neutron measurement member 1 is emitted from the plurality of activation members 11 of the neutron measurement member 1. ½ of the gamma rays that can be detected. Therefore, when the dose of gamma rays detected by the gamma ray absolute value measuring device 21 is doubled, the absolute values of gamma rays emitted from the plurality of activation members 11 of the neutron measurement member 1 can be calculated.

  On the other hand, a gamma ray individual measuring device 22 combining a position sensitive gamma ray detector 31 (radiation detector) and a gamma ray collimator 32 is provided above the neutron measuring member 1 in the figure. The gamma ray collimator 32 has a plurality of holes 32a (openings) respectively provided at positions corresponding to the plurality of activation members 11 of the neutron measurement member 1, and detects gamma rays from the respective activation members 11 by position sensitive gamma ray detection. Waveguided to the vessel 31. The gamma ray collimator 32 shields radiation (gamma rays) except for the holes 32a. Further, at the time of measurement, each of the plurality of activation members 11 of the neutron measurement member 1 is brought into contact with each of the plurality of holes 32 a of the gamma ray collimator 32. Therefore, gamma rays from the adjacent activation member 11 are prevented from entering the other hole 32a.

  When gamma rays are measured with the gamma ray collimator 32 and the position sensitive gamma ray detector 31 arranged as described above, the gamma rays emitted from the respective activation members 11 pass through different holes 32a and are position sensitive. By arriving at the gamma ray detector 31, the position sensitive gamma ray detector 31 measures the dose of gamma rays from each of the plurality of activation members 11 by individually measuring gamma rays incident from different holes 32a. can do.

  However, since the gamma ray collimator 32 is used to detect only the gamma rays emitted from each activation member 11 in a specific direction (direction toward the position sensitive gamma ray detector 31). The total amount of gamma rays detected by the gamma ray individual measuring device 22 is smaller than the dose of gamma rays detected by the gamma ray absolute value measuring device 21.

  Therefore, in the measurement value calibration unit 23 (see FIG. 2) of the activation amount measuring device 2, the absolute values of the gamma rays emitted from the plurality of activation members 11 calculated from the detection results of the gamma ray absolute value measuring device 21 are obtained. Calibration is performed using the data (S05). Thereby, the dose of gamma rays emitted from each of the plurality of activation members 11 can be calculated.

  In addition, when the calibration using the absolute value of the gamma ray detected by the gamma ray absolute value measuring device 21 is not performed, the activation amount may be calibrated by another method. For example, of the radiation emitted from the activation member 11 from the arrangement of the activation member 11 and the shape and arrangement of the gamma ray collimator 32, the position sensitive gamma ray detector 31 is reached through the hole 32 a of the gamma ray collimator 32. The ratio of radiation may be obtained in advance by simulation or the like, and the activation amount may be calibrated using the result. Further, by measuring gamma rays from a radiation source with a known dose in advance, the activation amount may be calibrated using the measurement result.

  As shown in FIG. 3, when the position sensitive gamma ray detector 31 is used, it is preferable that the position resolution is a little larger than the size of the activation member 11. By adjusting the position resolution as described above, the detection accuracy can be increased.

  Next, FIG. 4 explains another embodiment of the measurement by the gamma ray absolute value measuring device 21 and the measurement by the gamma ray individual measuring device 22.

  In the embodiment shown in FIG. 4, the measurement by the gamma ray absolute value measurement device 21 and the measurement by the gamma ray individual measurement device 22 are simultaneously performed on both surfaces of the neutron measurement member 1. The measurement of the gamma rays from each activation member 11 of the neutron measuring member 1 by the gamma ray detector as the gamma ray absolute value measuring device 21 below the neutron measuring member 1 is the same as the embodiment shown in FIG.

  On the other hand, on the upper side of the neutron measuring member 1, only the single channel type single channel type gamma ray detector 33 (radiation detector) and the gamma rays from one activation member 11 reach the single channel type gamma ray detector 33. There is provided a gamma ray individual measuring device 22 having a hole 34a to be combined and a shielding member 34 for shielding gamma rays from other activation members 11. In such a gamma ray individual measuring device 22, the neutron measuring member 1 is in contrast to the hole 34 a of the shielding member 34 in which the hole 34 a corresponding to only one of the plurality of activating members 11 is formed. Radiation (gamma rays) emitted from each of the activation members 11 and guided through the holes 34a of the shielding member 34 in a state where one of the activation members 11 is in contact with the activation member 11 is detected. To do.

  Thereafter, by changing the relative position between the gamma ray individual measuring device 22 and the neutron measuring member 1, gamma rays from other activation members 11 can be individually detected. Specifically, the gamma ray individual measuring device 22 is moved with the neutron measuring member 1 fixed, or the neutron measuring member 1 is moved with the gamma ray individual measuring device 22 fixed. Thereby, the radiation (gamma rays) emitted from the other activation member 11 and guided through the hole 34a of the shielding member 34 can be detected. And by repeating this process, the radiation from each activation member 11 of the neutron measurement member 1 can be detected individually.

  After the gamma rays from the plurality of activation members 11 are individually detected, the gamma ray absolute value measuring device is used in the measurement value calibration unit 23 (see FIG. 2) of the activation amount measuring apparatus 2 as in the embodiment shown in FIG. Calibration is performed using the absolute values of gamma rays emitted from the plurality of activation members 11 calculated from the detection results at 21 (S05). Thereby, the dose of gamma rays emitted from each of the plurality of activation members 11 can be calculated.

  In addition, like the Example shown in FIG.3 and FIG.4, the measurement of the absolute value of the gamma ray from each activation member 11 of the neutron measurement member 1 by the gamma ray absolute value measuring device 21 in the lower part of the neutron measurement member 1 in the figure, It is not necessary to simultaneously perform the individual measurement of gamma rays from the respective activation members 11 of the neutron measurement member 1 by the gamma ray individual measuring device 22 in the upper part of the figure. Therefore, for example, after measuring the absolute value of the gamma ray from each activation member 11, the calibration may be performed to individually measure the gamma ray from each activation member 11. However, since the amount of gamma rays emitted changes depending on the elapsed time from activation, it is preferable to evaluate by combining the elapsed time and the like.

  As described above, according to the neutron measurement member 1 according to the present embodiment, since the plurality of activation members 11 are fixed to the fixed portion 12 at a predetermined interval, the plurality of activation members 11 are individually set. The activation member can be appropriately arranged as compared with the case where the activation member is arranged at a desired position. Therefore, the neutron distribution can be accurately measured.

  Moreover, when the fixing | fixed part 12 is a sheet-like member which has plasticity like said neutron measuring member 1, it becomes possible to deform | transform a fixing | fixed part according to the shape etc. of the place used as the measurement object of a neutron. . Therefore, a sound for accurately measuring the distribution of neutrons is possible regardless of the location of the measurement object.

  Further, according to the activation amount measuring method shown in FIG. 3, by using the gamma ray collimator 32 in which the plurality of holes 32a are formed at the same interval as the interval at which the plurality of activation members 11 are fixed in the neutron measurement member 1. The position-sensitive gamma ray detector 31 can individually detect the radiation emitted from each of the plurality of activation members 11. Therefore, the activation amounts of the plurality of activation members 11 of the neutron measurement member 1 can be measured individually and accurately.

  Further, according to the activation amount measuring method shown in FIG. 4, the shielding member 34 in which a hole corresponding to only one activation member 11 among the plurality of activation members 11 of the neutron measurement member 1 is used. Then, after the radiation emitted from one of the plurality of activation members 11 is detected by the single channel type gamma ray detector 33, the activation member that comes into contact with the hole 34a of the shielding member 34 is used as one member. Change to other member and measure. By setting it as such a structure, it becomes possible to detect separately the radiation discharge | released from each of several activation member. Therefore, the activation amounts of the plurality of activation members of the neutron measurement member can be individually and accurately measured.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment.

  For example, in the above-described embodiment, the case where the radiation emitted from the activated activation member 11 is gamma rays has been described, but the type of radiation emitted from the activation member 11 is not particularly limited.

  The shapes of the gamma ray collimator 32 and the shielding member 34 for individually detecting radiation emitted from the activated activation member 11 are not particularly limited.

  DESCRIPTION OF SYMBOLS 1 ... Neutron measuring member, 2 ... Activation amount measuring apparatus, 11 ... Activation member, 12 ... Fixed part, 21 ... Gamma ray absolute value measuring device, 22 ... Gamma ray individual measuring device, 23 ... Measurement value calibration part, 31 ... Position Sensitive gamma ray detector, 32... Gamma ray collimator, 33... Single channel gamma ray detector, 34.

Claims (4)

A plurality of activation members made of metal that is activated by irradiation with neutrons;
A neutron measurement member, comprising: a fixing portion to which the plurality of activation members are fixed at a predetermined interval.   The neutron measurement member according to claim 1, wherein the fixing part is a sheet-like member having plasticity. A method for measuring the amount of activation of a neutron measuring member,
Neutron measurement after neutron beam irradiation, comprising: a plurality of activation members made of metal activated by neutron beam irradiation; and a fixed portion to which the plurality of activation members are fixed at predetermined intervals. Preparing a member;
Contacting the plurality of activation members of the neutron measurement member with each of the plurality of holes of the gamma ray collimator in which a plurality of holes are formed at the same interval as the interval at which the activation member is fixed;
Individually detecting radiation emitted from each of the plurality of activation members and guided through each of the plurality of holes by a radiation detector;
A method for measuring the amount of activation. A method for measuring the amount of activation of a neutron measuring member,
Neutron measurement after neutron beam irradiation, comprising: a plurality of activation members made of metal activated by neutron beam irradiation; and a fixed portion to which the plurality of activation members are fixed at predetermined intervals. Preparing a member;
Activation of one of the plurality of activation members of the neutron measurement member with respect to the hole of the shielding member in which a hole corresponding to only one activation member of the plurality of activation members is formed. Detecting radiation emitted from each of the one activation members and guided through the holes of the shielding member by a radiation detector in a state where the members are in contact with each other;
The activation member that contacts the hole of the shielding member is changed to another activation member different from the one activation member, and is emitted from the other activation member to guide the hole of the shielding member. Detecting the waved radiation by the radiation detector;
A method for measuring the amount of activation.

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