JP2008046030A - Radioactivity measuring apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure radioactivity of a measuring object by measuring relationship of the radioactivity and an ion amount at each radioactivity. <P>SOLUTION: An apparatus for measuring the radioactivity of the measuring object 1 has a gas vessel 11, and vessel partition means 3 and 7 for partitioning the inside into a first space, a second space and a third space storing the measuring object 1. A gas of the inside of the first or the third spaces 6, 10 and 14 partitioned by the vessel partition means 3 and 7 is supplied to ion measurement means 15, 16 and 17 respectively to measure the ion amount generated by being ionized by the radioactivity released from the measuring object 1. A sample of known radioactivity is arranged in the first space 6, the relationship of the radioactivity and the ion amount at each radioactivity being the target of measurement is measured previously. The radioactivity of each radioactivity being the target of the measurement of the measuring object 1 is calculated based on the relationship and the ion amount generated in the first or the third space 6, 10 and 14 by the radioactivity released from the measuring object 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radioactivity measurement apparatus and radioactivity measurement method for measuring radioactivity of a measurement target.

  In general, when measuring radioactivity, when three types of α rays, β rays, and γ rays are emitted from the measurement target, it is necessary to measure each type of radiation. Generally, a Si semiconductor detector or a ZnS scintillation detector is used for α rays, a plastic scintillation detector is used for β rays, and a NaI (Tl) scintillation detector or Ge semiconductor detector is used for γ rays. Therefore, for example, when measuring three types of radiation, the above three types of detectors are required.

Further, for example, Patent Document 1 and Patent Document 2 disclose an apparatus that stores an object to be measured in a measurement chamber and measures the ion current by sucking air ionized by radiation from the gas inside the measurement chamber. .
JP 2004-85497 A JP 2004-239762 A

  When measuring the radioactivity intensity of α-rays, β-rays and γ-rays emitted from the measurement object, three types of detectors and separate measurement systems corresponding to them are required, increasing the scale of the measuring device. . In addition, when using a method of measuring the ion current by sucking the air in which the gas inside the measurement chamber is ionized by radiation by storing a measurement object such as a cylindrical shape in the measurement chamber of the measurement device, The generated ions have a high ion annihilation rate due to the slow velocity of the gas flowing inside the measurement chamber, and the measurement accuracy of radioactivity is lowered. The recombination of ions and the adhesion to the wall also increase the ion annihilation rate, thus reducing the measurement accuracy.

  Then, an object of this invention is to enable it to measure the radioactivity of a measuring object accurately.

  In order to achieve the above-described object, the present invention provides a radioactivity measurement apparatus for measuring radioactivity of a measurement target, a gas container, a storage space for storing the measurement target in the gas container, and at least one Partitioning means for forming a space outside the two storage spaces, and for each space partitioned by the partitioning means, the amount of ions generated by ionizing the gas inside the space by the radiation emitted from the measurement object And an ion measuring means for measuring.

  Further, the present invention relates to a radioactivity measurement apparatus for measuring the radioactivity of a cylindrical measurement object whose both ends are open, the gas container storing the measurement object, the inside of the gas container, and the measurement object Means for supplying a gas flowing inside the measurement object at a flow velocity larger than an average flow velocity of the gas flowing outside, and ions generated by ionizing the gas inside the gas container by radiation emitted from the measurement object And an ion measuring means for measuring the quantity.

  Further, the present invention provides a radioactivity measurement method for measuring radioactivity of a measurement target, wherein ions generated by ionizing a gas inside a space in which the measurement target is stored by radiation emitted from the measurement target. A first ion measurement step for measuring the amount, and a second ion for measuring the amount of ions generated by ionizing a gas outside the space in which the measurement object is stored by the radiation emitted from the measurement object A measurement step, a preliminary step for obtaining a relationship between the radioactivity for each radiation to be measured and the amount of ions measured in the first and second ion measurement steps, and the first and second ion measurements. And calculating the radioactivity for each radiation intended for measurement of the measurement object from the amount of ions measured in the step and the relationship obtained in the preliminary step.

  Further, the present invention provides a radioactivity measurement method for measuring the radioactivity of a cylindrical measurement object whose both ends are open, and flows inside the measurement object at a flow velocity larger than the average flow velocity of the gas flowing outside the measurement object. The method includes a step of supplying a gas and a step of measuring the amount of ions ionized and generated by radiation emitted from the measurement object.

  According to the present invention, the radioactivity of a measurement object can be measured with high accuracy.

  Embodiments of a radioactivity measurement apparatus according to the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or similar structure, and the overlapping description is abbreviate | omitted.

[First Embodiment]
FIG. 1 is a cross-sectional view of the radioactivity measurement apparatus according to the first embodiment of the present invention.

  This radioactivity measuring apparatus has first to third ion measuring means 15, 16, 17 and a gas container 11. The gas container 11 is, for example, a square tube having a total axial length of 2 m.

  Inside the gas container 11, the first container partitioning means 3 is arranged. Further, a second container partitioning means 7 surrounding the first container partitioning means 3 is arranged inside the gas container 11. Inside the gas container 11, a first space 6 partitioned by the first container partitioning means 3 and a second space 10 surrounded by the first container partitioning means 3 and the second container partitioning means 7. And the 3rd space 14 enclosed by the 2nd container partition means 7 and the gas container 11 is formed.

  A first gas intake path 4 that connects the first space 6 to the outside of the gas container 11 is attached to the first container partitioning means 3. The first container partitioning means 3 is provided with a first gas extraction path 5 that connects the first space 6 to the first ion measuring means 15.

  A second gas intake path 8 that connects the second space 10 to the outside of the gas container 11 is attached to the second container partitioning means 7. The second container partitioning means 7 is provided with a second gas extraction path 9 for connecting the second space 10 to the second ion measuring means 16.

  In addition, the gas container 11 is formed with a third gas intake path 12 that connects the third space 14 to the outside of the gas container 11. In addition, a third gas extraction path 13 that connects the third space 14 to the third ion measuring means 17 is attached to the gas container 11.

  In FIG. 1, the first to third gas intake paths 4, 8, 12 and the first to third gas extraction paths 5, 9, 13 are all arranged in the same cross section, but different cross sections. It does not matter even if it is arranged in.

  When radiation such as α-rays, β-rays, and γ-rays is emitted from the radiation source 2 of the measurement object 1 arranged in the first space 6, the gas inside the first to third spaces 6, 10, 14 Are ionized by radiation and become ions.

  A gas such as air outside the gas container 11 flows into the first space 6 from the first gas intake path 4 by, for example, convection, and further passes through the first gas extraction path 5 to the first ion measuring means. 15 flows. Similarly, the gas outside the gas container 11 flows into the second space 10 from the second gas intake path 8 by convection, and further passes through the second gas extraction path 9 to the second ion measuring means 16. Flowing into. The gas outside the gas container 11 flows from the third gas intake path 12 into the third space 14 by convection, and further passes through the third gas extraction path 13 to the third ion measuring means 17. Flowing.

  The shape of the first to third spaces 6, 10, 14 and the material and thickness of the partition means 3, 7 between them are such that ions generated in the first space 6 are ionized by α rays, β rays, and γ rays. The ions generated in the second space 10 are ionized by β rays and γ rays, and the ions generated in the third space 14 are determined to be ionized by γ rays. . For example, the inner width of the first container partition means 3 is 20 cm, the distance between the first container partition means 3 and the second container partition means 7 is 10 cm, and the distance between the second container partition means 7 and the gas container 11 Is 80 cm.

  Note that the first to third gas extraction paths 4, 8, and 12 pass through the first to third spaces 6, 10, and 14 to the first to third gas extraction paths 5, 9, and 13, respectively. The flowing gas flow may be forcibly created using, for example, a blower.

  Next, a method for measuring the radiation emitted from the radiation source 2 of the measuring object 1 using this radiation measuring instrument will be described.

  Prior to measurement of radiation emitted from the radiation source 2 of the measurement object 1, a reference sample having a known radioactivity is placed in the first space 6, and the first to third ion measuring means 15, The current is measured at 16 and 17.

First, an α-ray reference sample having a known α-ray radioactivity a ₀ is placed in the first space 6. Thereby, the gas inside the first space 6 is ionized by α rays and becomes ions. Therefore, the current I _1a0 is measured by the first ion measuring means 15. By this measurement, it is possible to obtain a relationship between the α-ray radioactivity a of an unknown substance arranged in the first space 6 and the current I _1a measured by the first ion measuring means 15. This relationship is expressed as a = A ₁ × I _1a using, for example, a conversion coefficient A ₁ that satisfies a ₀ = A ₁ × I _1a0 .

  At this time, it may be confirmed together that no current is measured by the second and third ion measuring means 16 and 17.

Next, a β-ray reference sample having a known β-ray activity b ₀ is placed in the first space 6. Thereby, the gas inside the first and second spaces 6 and 10 is ionized by β rays to become ions. Therefore, the current I _2b0 is measured by the second ion measuring means 16. By this measurement, the relationship between the β-ray activity b of an unknown substance arranged in the first space 6 and the current I _2b measured by the second ion measuring means 16 can be obtained. This relationship is expressed as b = B ₂ × I _2b using a conversion coefficient B ₂ that satisfies b ₀ = B ₂ × I _2b0 , for example.

Further, the current I _1b0 is measured by the first ion measuring means 15. It is possible to obtain the relationship between the β-ray activity b of an unknown substance placed in the first space and the current I _1b measured by the first ion measuring means 15. This relationship is expressed as b = B ₁ × I _1b using, for example, a conversion coefficient B ₁ that satisfies b ₀ = B ₁ × I _1b0 .

  At this time, it may be confirmed that the current is not measured by the third ion measuring means 17.

Further, a γ-ray reference sample having a known γ-ray radioactivity c ₀ is placed in the first space. Thereby, the gas inside the 1st thru | or 3rd space 6,10,14 is ionized by a radiation, and becomes an ion. Therefore, the current I _3c0 is measured by the third ion measuring means 17. By this measurement, the relationship between the radioactivity c of the γ-ray of the unknown substance arranged in the first space 6 and the current measured by the third ion measuring means 17 can be obtained. This relationship is expressed as c = C ₃ × I _3c using, for example, a conversion coefficient C ₃ that satisfies c ₀ = C ₃ × I _3c0 .

Further, the current I _2c0 is measured by the second ion measuring means 16. By this measurement, the relationship between the γ-ray radioactivity c of the unknown substance arranged in the first space 6 and the current I _2c measured by the second ion measuring means 16 can be obtained. This relationship is expressed as c = C ₂ × I _2c using, for example, a conversion coefficient C ₂ that satisfies c ₀ = C ₂ × I _2c0 .

Similarly, the current I _1c0 is measured by the first ion measuring means 15. By this measurement, the relationship between the radioactivity c of the γ-ray of the substance placed in the first space and the current I _1c measured by the first ion measuring means 15 can be obtained. This relationship is expressed as c = C ₁ × I _1c using, for example, a conversion coefficient C ₁ that satisfies c ₀ = C ₁ × I _1c0 .

  In this way, the current measured by the first to third ion measuring means 15, 16, 17 when α rays, β rays, or γ rays are emitted from the object arranged in the first space. A relationship is required. From these relationships, the radioactivity of the measurement target 1 of unknown radioactivity can be obtained as follows.

First, the measuring object 1 is placed in the first space 6. When the radiation source 2 is attached to the measurement object 1, radiation such as α rays, β rays, and γ rays is emitted corresponding to the type of the radiation source 2. The gas inside the first to third spaces 6, 10, and 14 is ionized by radiation and becomes ions. These ions are measured by the first to third ion measuring means 15, 16, and 17. The currents measured by the first to third ion measuring means 15, 16, and 17 are I ₁ , I ₂ , and I ₃ , respectively.

At this time, since the current I ₃ measured by the third ion measuring means 17 is caused only by γ-rays, the radioactivity c of the γ-rays of the measuring object 1 is given by c = C ₃ × I ₃ Desired.

The current I ₂ measured by the second ion measuring means 16 is caused by β rays and γ rays. Of this I ₂ , the amount caused by γ rays is expressed as c / C ₂ using the γ ray radioactivity c obtained above. B = B ₂ × (I ₃ -c / C ₂ ).

The current I ₁ measured by the first ion measuring means 15 is caused by α rays, β rays and γ rays. Of this I ₁ , the component due to γ rays is expressed as c / C ₁ using the radioactivity c of γ rays obtained above. Moreover, the part resulting from β rays is expressed as b / B ₁ by using the radioactivity b of β rays obtained above. Therefore, the radioactivity a of the alpha ray of the measuring object 1 can be obtained as a = A ₁ × (I ₁ −b / B ₁ −c / C ₁ ).

Thus, from the currents I ₁ , I ₂ , and I ₃ measured by the first to third ion measuring means 15, 16, and 17, the radioactivity of the α ray, β ray, and γ ray of the measuring object 1, respectively. Can be requested.

  In the above description, the radiation to be measured is α rays, β rays, and γ rays. However, β rays, low energy γ rays, high energy γ rays, etc., or low, medium, and high energy γ rays are different. It may be energy radiation. When there are two types of radiation to be measured, two types of the first space 6 and the second space 10 may be used.

  Further, the measurement object 1 may be mounted on a rotating table that is not shown and moved up and down, and measurement may be performed while rotating continuously or stepwise.

  As described above, the measurement object 1 that emits α-rays, β-rays, and γ-rays also collects ions in three types of space, and performs arithmetic processing on the measured current values to obtain α-rays, β-rays and γ-rays Therefore, even with the measurement object 1 in which various kinds of radiation are mixed, the radiation can be measured with a simple measuring device with high accuracy.

[Second Embodiment]
FIG. 2 is a cross-sectional view of the radioactivity measurement apparatus according to the second embodiment of the present invention.

  The radioactivity measurement apparatus according to the present embodiment is the radioactivity measurement apparatus according to the first embodiment, in which the path switching means 18 is introduced into one ion measurement means and the gas purification means 21 is introduced. It is.

  In this radioactivity measurement apparatus, the first to third gas extraction paths 5, 9, and 13 extending from the first to third spaces 6, 10, and 14 are connected to the path switching means 18. The path switching means 18 is connected to the ion measuring means 20 via the gas path 19.

  The ion switching means 20 is switched by the path switching means 18 so that only the gas flowing in one of the first to third spaces 6, 10, 14 reaches. By this path switching means 18, the current due to the ions generated in each of the first to third spaces 6, 10, 14 can be independently measured by the ion measuring means 20. For this reason, the number of ion measuring means for performing the same measurement as the radioactivity measuring apparatus of 1st Embodiment can be reduced.

  A gas purification means 21 is attached to the first to third gas intake paths 4, 8, and 12. Ions contained in a gas such as the atmosphere flowing into the first to third gas intake paths 4, 8, and 12 are adsorbed by the gas purification means 21. For this reason, the influence of the ion outside the gas container 11 which affects measurement accuracy can be reduced, and radioactivity can be measured with high measurement accuracy.

[Third Embodiment]
FIG. 3 is a cross-sectional view of the radioactivity measurement apparatus according to the third embodiment of the present invention.

  In the radioactivity measurement apparatus of the present embodiment, the ion measurement means 20 in the radioactivity measurement apparatus of the second embodiment is replaced with an ion collection means 22 and the like.

  In the radioactivity measurement apparatus of the present embodiment, the path switching unit 18 is connected to the ion collection unit 22. The ion collecting means 22 is connected to a gas transport means 27 for transporting the gas inside the gas container 11 to the ion collecting means 22 via a gas discharge path 61. The gas transport means 27 is connected to a gas purification means 28 that purifies the gas. As the gas purification means 28, for example, a HEPA filter can be used.

  Connected to the ion collecting means 22 are a power source 23 for applying a voltage to the electrodes of the ion collecting means and a current measuring means 24 for measuring the collected ions as a current. As the current measuring means 24, for example, an electrometer can be used. Data processing means 25 is connected to the current measuring means 24.

  Also in this radioactivity measurement apparatus, as in the radioactivity measurement apparatus of the second embodiment, the gas in the first to third spaces 6, 10, and 14 is independently ion collection means by the path switching means 18. 22 is sent. In the first to third spaces 6, 10, and 14, the amount of ions generated by the ionizing action of the radiation emitted from the measuring object 1 is collected by the ion collecting means 22 and measured as a current by the current measuring means 24. Is done.

  As described in the first embodiment, by measuring the amount of ions generated in the first to third spaces 6, 10, and 14, the radiation of the measuring object 1 arranged in the first space 6. Noh can be sought. In the present embodiment, the radioactivity of the measuring object 1 is calculated by the data processing unit 25 based on the current measured by the current measuring unit 24.

  Further, a radiation sensor is arranged in any one of the first to third spaces 6, 10, and 14 to directly measure specific radiation such as γ-rays emitted from the measurement object 1, and the data processing means 25 The radioactivity of the measuring object 1 calculated based on the amount of ions measured by the ion measuring means 20 may be corrected.

  Thus, in this radioactivity measurement apparatus, the gas in the first to third spaces 6, 10, and 14 is transported by the gas transport means 27, so that the gas transport speed is improved and the ion attenuation rate is decreased. For this reason, ions can be collected with high efficiency, and radioactivity can be measured with high accuracy.

[Fourth Embodiment]
FIG. 4 is a cross-sectional view of the radioactivity measurement apparatus according to the fourth embodiment of the present invention.

  The radioactivity measurement apparatus according to the present embodiment measures radiation emitted from a cylindrical measurement object 51 to which radiation sources 52 and 53 are attached and both ends are open.

  This radioactivity measurement apparatus has a cylindrical gas container 11 that can store a cylindrical measurement object 51. A variable opening 30 is attached to one end of the gas container 11. An opening switching means 31 is attached to the variable opening 30. The variable opening 30 has an opening through which the gas inside the cylindrical measurement object 51 passes, an opening through which the external gas passes, and an opening through which the gas inside and outside passes. The opening switching means 31 can switch the variable opening 30 to a target opening among these openings.

  In addition, the ion collection means 22 is attached to the variable opening 30 via the air current converging means 33. The ion collection unit 22 is connected to a gas transport unit 27 that transports the gas inside the gas container 11 to the ion collection unit 22 via a gas discharge path 61. The gas transport means 27 is, for example, a fan. The gas transport means 27 is connected to the gas purification means 28. The gas purification means 28 is connected to the end of the gas container 11 opposite to the end to which the variable opening 30 is attached via a gas introduction path 62. In the vicinity of the end of the gas container 11 opposite to the end to which the variable opening 30 is attached, a flow dividing means 32 for guiding the gas to the inside and the outside of the cylindrical measurement object 51 is disposed. .

  The gas inside the gas container 11 is sent by the gas transport means 27 to the gas purification means 28 through the variable opening 30, the ion collection means 22, and the gas discharge path 61. The gas purified by the gas purification means 28 is introduced again into the gas container 11 through the gas introduction path 62.

  A power source 23 is connected to the ion collector 22 via a power buffer 29 that smoothes the voltage. The ion collecting means 22 is connected to a current measuring means 24 for measuring the collected ions as a current. A data processing means 25 is connected to the current measuring means 24.

  In this radioactivity measurement apparatus, the radioactivity of the radiation sources 52 and 53 attached to the inside and outside of the cylindrical measurement object 51 can be measured as follows.

  For example, it is assumed that the radiation sources 52 and 53 are uranium that emits α rays.

  The gas supplied to the gas container 11 by the diversion unit 32 is transported from one end of the cylindrical measurement object 51 to the outside and the inside by the diversion unit 32. Therefore, when the variable opening 30 is switched to transport gas outside the cylindrical measurement target 51, the other end of the internal gas is closed by the variable opening 30, so Only the gas flowing outside is transported to the ion collecting means 22 through the variable opening 30.

  That is, as a result of the ionization of the gas by the radiation emitted from the radiation source 53 attached to the outside of the cylindrical measurement target 51, the generated ions pass through the variable opening 30 together with the air and reach the ion collecting means 22 to be collected. Then, it is measured as a current by the current measuring means 24.

  Next, the opening is set by the opening switching means 31 so that the gas inside the cylindrical measurement object 51 passes through the variable opening 30. In this case, ions generated by the radiation emitted from the radiation source 52 attached to the inside of the cylindrical measurement target 51 pass through the variable opening 30 together with the air flowing inside the cylindrical measurement target 51, and then the ion collection means 22. And is measured as current.

  As described above, the current from the radiation source 53 attached to the outside of the cylindrical measurement target 51 and the current from the radiation source 52 attached to the inside of the cylindrical measurement target 51 can be measured independently. Using these current values and conversion constants from current to radioactivity caused by ions contained in the gas flowing outside and inside the cylindrical measurement target 51 obtained in advance, the outside and the inside of the cylindrical measurement target 51 are measured. The radioactivity of each can be determined. Moreover, if these external and internal radioactivity are added, the total radioactivity of the cylindrical measuring object 51 is calculated | required.

  In addition, when the variable opening 30 is set as an opening through which gas passing through both the outside and the inside of the cylindrical measurement target 51 is passed, the radiation source 53 attached to the outside of the cylindrical measurement target 51 and the inside are attached. The ions generated by the ionizing action of the radiation from the radiation source 52 are collected and measured simultaneously. For this reason, the total radioactivity of the cylindrical measuring object 51 can also be calculated | required by one measurement operation.

  Note that although uranium that emits α rays has been described as an example of the radiation sources 52 and 53 attached to the outside and inside of the cylindrical measurement target 51, the radiation emitted by the radiation sources 52 and 53 may be β rays. Further, when the radiation transmittance inside and outside the cylindrical measurement target 51 is small, γ rays may be used. When the transmittance of γ-rays is large, in calculating the radioactivity of the radiation source 52 adhering to the inside, the influence of the radiation source 53 adhering to the outside is corrected, and the radioactivity of the radiation source 53 adhering to the outside is calculated. In the calculation, the influence of the radiation source 52 adhering to the inside may be corrected.

  In addition, when the voltage is supplied to the data processing unit 25 via the power supply buffer 29, the fluctuation range of the current after the voltage application is stopped and the voltage without passing through the power supply buffer 29 to the ion collection unit 22. The noise of the power supply may be detected by comparing with the fluctuation range of the current after the application of the voltage is stopped.

  Thus, in this radioactivity measuring apparatus, the radioactivity of the radiation source adhering to the inside and outside of the cylindrical measurement object can be measured independently. Further, since the gas in contact with the measurement object is circulated through this radioactivity measurement device without being discharged to the outside, the possibility that the radiation source diffuses to the outside is reduced.

[Fifth Embodiment]
FIG. 5 is a cross-sectional view of the radioactivity measurement apparatus according to the fifth embodiment of the present invention.

  The radioactivity measurement apparatus of the present embodiment deletes the variable opening, the opening switching means, and the diversion means from the radioactivity measurement apparatus of the fourth embodiment, and supplies the airflow into the cylindrical measurement target 51 Airflow spraying means is added.

  The air current blowing means includes a blowing port 34, a blowing path 35, a blowing air blowing means 36 and a gas purification means 37. The blowing port 34 is disposed in the vicinity of a portion connected to the gas introduction path 62 of the gas container 11, and is configured to be able to blow an airflow toward the end of the cylindrical measurement target 51. An airflow flowing at a speed faster than the average flow velocity flowing through the outside 72 of the cylindrical measurement target 51 is supplied to the inside 71 of the cylindrical measurement target 51 from the blowing port 34.

  When the cross-sectional area of the inside 71 of the cylindrical measurement target 51 is small, the gas velocity may be small, and the rate at which ions disappear before reaching the ion collecting means 22 may be high. In the radioactivity measurement apparatus according to the present embodiment, the annihilation rate of ions generated in the inside 71 of the cylindrical measurement target 51 can be reduced by transporting the gas by the airflow supplied from the spray port 34. .

  Moreover, when the airflow supplied from the blowing port 34 is supplied only to the center of the cross section of the inside 71 of the cylindrical measurement object 51, the air on the inner surface is entrained in the airflow, so that the inner surface is averaged. It is possible to improve the measurement efficiency as compared with the case where the same flow is provided in each other.

  In this way, if the air flow is sprayed on the inside 71 of the cylindrical measurement object 51 by the air current blowing means, the ion annihilation rate is improved. The radioactivity can be measured with high accuracy.

[Sixth Embodiment]
FIG. 6 is a cross-sectional view of the ion collecting means 22 used in the radioactivity measuring apparatus according to the sixth embodiment of the present invention.

  The ion collecting means 22 has a cylindrical outer cylinder 43 whose both ends are open. In the vicinity of one end 91 of the outer cylinder 43, an electrode 38 is fixed to the outer cylinder 43 via an insulating material 39, a guard ring 40, an insulating material 41, and a support rod 42. An electrode free end holding / releasing means 82 is attached in the vicinity of the other end 92 of the outer cylinder 43. The electrode free end holding / releasing means 82 includes an insulating material 44, a fixing bar 45, and a fixing bar adjusting means 46. The electrode 38 extends in the axial direction of the outer cylinder 43, and the free end 81 to which the electrode 38 is not fixed is located in the vicinity of the insulating material 44 of the electrode free end holding / releasing means 82.

  The insulating material 44 is brought into contact with and held by the free end 81 of the electrode 38 by the fixing rod adjusting means 46, and ions in the gas flowing inside the ion collecting means 22 are collected and the ion current is measured.

  Further, when the fixing rod adjusting means 46 is adjusted to release the insulating material 44 from the free end 81 of the electrode 38 and the free end 81 is released, the free end 81 of the electrode 38 vibrates according to the gas flow velocity. For this reason, when the free end 81 of the electrode 38 is released, a time change corresponding to the gas flow velocity occurs in the ion current.

  Therefore, the flow velocity of the gas flowing inside the ion collecting means 22 can be obtained by obtaining the relationship between the vibration width of the ion current and the gas flow velocity in advance. By correcting the ion current based on the gas flow velocity, the ion current can be measured accurately even when the gas flow velocity changes, so that the radioactivity of the radiation source attached to the measurement target can be measured. Can be measured with high accuracy.

[Seventh Embodiment]
FIG. 7 is a cross-sectional view of the ion collecting means 22 used in the radioactivity measuring apparatus according to the seventh embodiment of the present invention.

  The ion collecting means 22 has a cylindrical outer cylinder 43 whose both ends are open. In the vicinity of one end 91 of the outer cylinder 43, an electrode 38 is fixed to the outer cylinder 43 via an insulating material 39, a guard ring 40, an insulating material 41, and a support rod 42. Further, near the other end 92 of the outer cylinder 43, a rectifying means 47 fixed to the outer cylinder 43 with a fixing rod 48 is attached. The rectifying means 47 is convex toward the end portion 92 of the outer cylinder 43, for example, hemispherical, and is disposed in the vicinity of the central axis of the outer cylinder 43. The electrode 38 extends in the axial direction of the outer cylinder 43 to the vicinity of the rectifying means 47.

  In the ion collecting means 22, the gas flows from an end 92 near the rectifying means 47 of the outer cylinder 43. Since the gas is transported by the rectifying means 47 without disturbing the airflow in the vicinity of the electrode 38, fluctuations in the amount of ions captured by the electrode 38 can be reduced. For this reason, fluctuation of the ion current to be measured can be reduced, and the radioactivity of the measurement object can be measured with high accuracy.

[Eighth Embodiment]
FIG. 8 is a cross-sectional view of the ion collecting means 22 used in the radioactivity measuring apparatus according to the eighth embodiment of the present invention.

  The ion collecting means 22 of the present embodiment is different from the ion collecting means 22 of the seventh embodiment in the shape of the rectifying means. The rectifying means 49 is installed on the upstream side of the free end 81 of the electrode 38 and has a plurality of gas passages 93 extending in the axial direction of the outer cylinder 43 in addition to the vicinity of the central axis of the outer cylinder 43. The rectifying means 49 rectifies the gas downstream thereof and suppresses the gas from directly colliding with the free end 81 of the electrode 38. Therefore, the gas can be transported without disturbing the airflow in the vicinity of the electrode 38, the fluctuation of the ion current to be measured can be reduced, and the radioactivity of the measurement object can be accurately measured.

  The above description is merely an example, and the present invention is not limited to the above-described embodiments, and can be implemented in various forms. Moreover, it can also implement combining the characteristic of each embodiment.

It is sectional drawing of the radioactivity measuring apparatus of 1st Embodiment which concerns on this invention. It is sectional drawing of the radioactivity measuring apparatus of 2nd Embodiment which concerns on this invention. It is sectional drawing of the radioactivity measuring apparatus of 3rd Embodiment which concerns on this invention. It is sectional drawing of the radioactivity measuring apparatus of 4th Embodiment based on this invention. It is sectional drawing of the radioactivity measuring apparatus of 5th Embodiment based on this invention. It is a longitudinal cross-sectional view of the ion collection means used for the radioactivity measuring apparatus of 6th Embodiment based on this invention. It is a longitudinal cross-sectional view of the ion collection means used for the radioactivity measuring apparatus of 7th Embodiment based on this invention. It is a longitudinal cross-sectional view of the ion collection means used for the radioactivity measuring apparatus of 8th Embodiment based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Measurement object, 2 ... Radiation source, 3 ... 1st container partition means, 4 ... 1st gas intake path, 5 ... 1st gas extraction path, 6 ... 1st space, 7 ... 2nd Container partition means, 8 ... second gas intake path, 9 ... second gas extraction path, 10 ... second space, 11 ... gas container, 12 ... third gas intake path, 13 ... third Gas extraction path, 14 ... third space, 15 ... first ion measuring means, 16 ... second ion measuring means, 17 ... third ion measuring means, 18 ... path switching means, 19 ... gas path, 20 ... Ion measuring means, 21 ... Gas purifying means, 22 ... Ion collecting means, 23 ... Power source, 24 ... Current measuring means, 25 ... Data processing means, 27 ... Gas transport means, 28 ... Gas purifying means, 29 ... Power supply buffer, 30 ... variable opening, 31 ... opening switching means, 32 ... diversion means, 33 ... airflow convergence means, 4 ... Blowing port, 35 ... Blowing path, 36 ... Blowing means for blowing, 37 ... Gas purification means, 38 ... Electrode, 39 ... Insulating material, 40 ... Guard ring, 41 ... Insulating material, 42 ... Support rod, 43 ... Outside Cylinder, 44 ... Insulating material, 45 ... Fixed rod, 46 ... Fixed rod adjusting means, 47 ... Rectifying means, 48 ... Fixed rod, 49 ... Rectifying means, 61 ... Gas discharge path, 62 ... Gas introduction path

Claims (15)

In a radioactivity measuring device that measures the radioactivity of a measurement target,
A gas container;
Partitioning means for forming a storage space for storing the measurement object inside the gas container, and a space outside the at least one storage space;
For each space partitioned by the partitioning means, an ion measuring means for measuring the amount of ions generated by ionizing the gas inside the space by radiation emitted from the measurement object;
A radioactivity measuring apparatus comprising: For each space partitioned by the partitioning means, a gas intake path for taking the gas outside the gas container into the space;
For each space partitioned by the partitioning means, a gas extraction path for extracting gas from the space and transporting it to the ion measuring means;
The radioactivity measuring apparatus according to claim 1, wherein   The radioactivity measurement apparatus according to claim 2, further comprising a gas purification unit that purifies the gas attached to the gas intake path. Switching means connected to the gas extraction path and switching so that only the gas inside is transported to the ion measuring means for each space partitioned by the partitioning means,
The radioactivity measurement apparatus according to claim 2, wherein the radioactivity measurement apparatus comprises: The relationship between the radioactivity for each measurement target radiation and the amount of ions for each space partitioned by the partitioning unit measured by the ion measuring unit, and the partitioning unit measured by the ion measuring unit Data processing means for calculating the radioactivity for each radiation intended for measurement of the measurement object based on the amount of ions for each partitioned space,
The radioactivity measuring apparatus according to claim 1, wherein the radioactivity measuring apparatus comprises: A radiation sensor disposed inside the gas container;
Correction means for correcting the radioactivity calculated by the data processing means based on the intensity of radiation measured by the radiation sensor;
The radioactivity measurement apparatus according to claim 4, wherein: The measurement object is a cylindrical shape with both ends open,
A variable opening that is attached to one end of the measurement object and switches so that at least one gas inside and outside the measurement object is transported to the ion measurement means,
The radioactivity measuring apparatus according to claim 1, wherein   The radioactivity measurement apparatus according to claim 7, further comprising a diversion unit that is attached to the gas container and guides the gas to the inside and outside of the measurement target. In a radioactivity measuring device that measures the radioactivity of a cylindrical measuring object with both ends open,
A gas container for storing the measurement object;
Means for supplying a gas flowing inside the measurement object at a flow velocity larger than an average flow velocity of the gas inside the gas container and flowing outside the measurement object;
An ion measuring means for measuring the amount of ions generated by ionizing the gas inside the gas container by radiation emitted from the measurement object;
A radioactivity measuring apparatus comprising: The ion measuring means includes
An outer cylinder open at both ends,
An electrode extending in the axial direction of the outer cylinder;
Fixing means for electrically insulating the vicinity of a fixed end which is one end of the electrode and fixing the electrode to the outer cylinder;
Electrode free end holding solution means capable of holding a free end which is the end opposite to the fixed end of the electrode so as not to vibrate the electrode in an open state so as to vibrate by the gas flowing inside the outer cylinder. When,
The flow rate of the gas flowing inside the outer cylinder is obtained based on the amplitude of the ionic current measured with the free end of the electrode open, and the measurement is performed with the free end of the electrode held based on the flow rate. Flow velocity correction means for correcting the ion current,
The radioactivity measurement apparatus according to claim 1, comprising: The ion measuring means includes
An outer cylinder open at both ends,
Rectifying means for rectifying the flow of gas inside the outer cylinder;
An electrode extending in the axial direction of the outer cylinder in the vicinity of the axis of the outer cylinder on the downstream side of the gas flow with respect to the rectifying means;
Fixing means for electrically insulating the vicinity of the end portion of the electrode far from the rectifying means and fixing the outer cylinder;
The radioactivity measurement apparatus according to claim 1, comprising:   The radioactivity measuring apparatus according to claim 11, wherein the rectifying means has a plurality of air passage openings extending in an axial direction of the outer cylinder. A power supply for applying a voltage to the ion measuring means;
Smoothing means for smoothing the voltage applied to the ion measuring means;
The fluctuation range of the current after stopping the application of voltage when the voltage is supplied to the ion measuring means via the smoothing means, and the application of the voltage when the voltage is supplied to the ion collecting means without passing the smoothing means Means for comparing the fluctuation range of the current after stopping and detecting noise of the power source;
The radioactivity measurement apparatus according to claim 1, wherein the radioactivity measurement apparatus comprises: In the radioactivity measurement method for measuring the radioactivity of the measurement object,
A first ion measurement step of measuring an amount of ions generated by ionizing a gas inside a space in which the measurement object is stored by radiation emitted from the measurement object;
A second ion measurement step of measuring the amount of ions generated by ionizing a gas outside the space in which the measurement object is stored by the radiation emitted from the measurement object;
A preliminary step for determining the relationship between the radioactivity for each radiation to be measured and the amount of ions measured in the first and second ion measurement steps;
A step of calculating the radioactivity for each radiation intended for measurement of the measurement object from the amount of ions measured in the first and second ion measurement steps and the relationship obtained in the preliminary step;
A radioactivity measurement method comprising the steps of: In the radioactivity measurement method for measuring the radioactivity of a cylindrical measurement object with both ends open,
Supplying a gas flowing inside the measurement object at a flow velocity larger than an average flow velocity of the gas flowing outside the measurement object;
Measuring the amount of ions produced by ionization by radiation emitted from the measurement object;
A radioactivity measurement method comprising the steps of:

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