JP6510340B2 - Radiation measurement unit and radioactivity concentration measuring device - Google Patents

Description

  The present invention relates to a radiation measurement unit which is immersed in a test solution to measure a radiation dose, and a radiation concentration measurement apparatus using the radiation measurement unit.

  Conventionally, as shown in Patent Document 1, the radiation dose or radioactivity concentration of the measurement sample is background measurement in which the radiation dose is measured without putting the measurement sample in the storage container, and the radiation dose is put in the storage container with the measurement sample It is determined by performing this measurement to measure the Specifically, the radiation dose or the radioactivity concentration is determined using the net value obtained by subtracting the background measurement value from the measurement value of this measurement.

  However, in the conventional method, since it is necessary to perform background measurement to cancel the spatial radiation dose in the surrounding environment, the measurement operation becomes complicated. In addition, in order to prevent positional deviation between the installation position of the dosimeter for background measurement and the installation position of the dosimeter for this measurement, a dedicated fixing jig is required. Furthermore, it is difficult to perform background measurement, for example, in the case of directly measuring contaminated water stored in a water reservoir or the like.

JP, 2013-36957, A

  On the other hand, the inventor of the present application has conducted intensive studies to cancel the spatial radiation dose in the surrounding environment without performing background measurement. Then, the inventor of the present application has focused on the fact that the spatial radiation dose in the surrounding environment is not substantially measured due to the radiation shielding effect of the test solution by immersing the dosimeter in the test solution.

  However, if the dosimeter is too close to the bottom wall of the test fluid container, it will be affected by the spatial radiation dose from the ground or sediment, and if too close to the water surface of the test fluid, the spatial radiation from the water surface It is affected by the quantity. Furthermore, when the test solution is suspended, it is not possible to visually recognize the immersed dosimeter, and it becomes more difficult to grasp the immersion depth of the dosimeter.

  Therefore, the present invention is intended to provide a radiation measurement unit capable of installing the dosimeter at an appropriate position by easily grasping the immersion depth of the dosimeter.

  That is, a radiation measurement unit according to the present invention is a radiation measurement unit which is immersed in a test solution to measure the radiation dose of the test solution, and a cylindrical body to be immersed in the test solution, and the cylindrical shape A radiation dosimeter housed at the tip of the body, and a depth indicator provided on the cylindrical body to indicate the immersion depth of the radiation dosimeter.

  If it is such, since the depth display part which shows the immersion depth of a dosimeter is provided in a cylindrical body, the immersion depth of a dosimeter can be grasped | ascertained easily. Thereby, a dosimeter can be installed in the immersion depth optimal with respect to the water depth of a test solution.

  When the sensing unit of the dosimeter is housed inside the cylindrical body, radiation is attenuated by the air layer between the cylindrical body and the sensing unit, and a measurement error occurs in the radiation dose. It will For this reason, it is desirable for the sensing part of the said dosimeter to be exposed outside from the said front-end | tip part. With this configuration, attenuation by the air layer can be prevented, and measurement sensitivity can be increased.

  When immersing the cylindrical body in the test liquid, buoyancy acts on the cylindrical body. And, the deeper the immersion depth of the dosimeter, the greater the buoyancy and the more difficult the immersion operation. For this reason, it is desirable that at least a portion on the proximal side of the distal end of the cylindrical body be thinner. With this configuration, at least a part of the proximal end side is thinner than the distal end portion, and therefore, the buoyancy can be reduced compared to the case of immersing a tubular body having the same thickness, and the immersion operation can be performed. It can be easy.

  Further, regardless of the buoyancy acting on the cylindrical body, in order to facilitate the immersion operation, the cylindrical body is further provided with a propeller for lowering the tip end portion in the test liquid. Is desirable. Moreover, the test solution can be stirred by this propeller. By stirring the test solution, it is possible to disperse the deposited radioactive substance and to accurately measure the radiation dose of the test solution.

  It is desirable that the sensing unit of the dosimeter be exposed to the outside from the end face in the axial direction of the cylindrical body, and the propeller be provided to face the end face in the axial direction. With this configuration, the test solution stirred by the propeller hits the sensing unit, and the sensing unit can be cleaned, and adhesion of dirt to the sensing unit can be prevented.

Further, a radioactivity concentration measuring apparatus according to the present invention includes the above-described radiation measurement unit, and a calculation unit that calculates the radioactivity concentration of the test solution using the radiation dose obtained by the radiation measurement unit as a parameter. It is characterized by
If it is such, a dosimeter can be installed in a suitable position by a radiation measurement unit. Therefore, the radiation concentration which is not influenced by the background (space radiation dose of the surrounding environment) can be used to determine the correct radioactivity concentration.

  According to the present invention configured as described above, the tubular body is provided with the depth display unit indicating the immersion depth of the dosimeter, so that the immersion depth of the dosimeter can be easily grasped. The radiation dosimeter can be installed at an optimum immersion depth with respect to the water depth of the test solution.

It is a whole schematic diagram showing the radioactivity concentration measuring device in one embodiment of the present invention. It is a schematic diagram including the partial cross section which shows the structure of the radiation measurement unit of the embodiment. It is a figure which shows the relationship between space radiation dose rate and radioactivity concentration. It is a schematic diagram which shows the structure of the radiation measurement unit of modification embodiment.

  An embodiment of a radioactivity concentration measuring apparatus according to the present invention will be described below with reference to the drawings.

  The radioactivity concentration measuring apparatus 100 of this embodiment measures the radioactivity level of the polluted water emitted at the time of the decontamination work of the radioactive material using a high pressure washing machine etc., for example, and the simple radiation monitoring which monitors and manages the polluted water concerned It is used for the system. The contaminated water is stored in a reservoir and treated in an appropriate manner, and the supernatant is treated as drainage.

  Specifically, as shown in FIG. 1, the radioactivity concentration measuring apparatus 100 is a radiation which is immersed in the contaminated water (the test solution) in the water storage tank WT and measures the radiation dose (μSv / h or cps) of the contaminated water. The measurement unit 2 and an operation unit 3 for calculating the radioactive concentration (Bq / L) of the contaminated water using the radiation dose obtained by the radiation measurement unit 2 as a parameter.

  As shown in FIG. 2, the radiation measurement unit 2 includes a cylindrical body 21 immersed in the contaminated water, and a radiation dosimeter 22 housed at the tip of the cylindrical body 21.

  The cylindrical body 21 has, for example, a substantially straight pipe shape made of resin, and is a cylindrical pipe in the present embodiment. Further, the distal end opening of the cylindrical body 21 is closed by the distal end wall 211. The cylindrical body 21 is immersed in the contaminated water from the distal end 21A, and the base end 21B opposite to the distal end 21A serves as a grip to be gripped by the user. Other specific configurations will be described later.

  The radiation dosimeter 22 is a portable type that measures spatial radiation dose (gamma rays), and a CsI (Tl) scintillator 221 that emits light by radiation (gamma rays) and a photodiode (silicon that detects the luminescence of the CsI scintillator 221 And a computing unit 223 for calculating the radiation dose from the detection signal (current signal) obtained by the photodiode 222. Further, in the radiation dosimeter 22, the CsI scintillator 221 serves as a sensing unit. The + marks shown in FIG. 2 indicate the central portion of the sensing unit (CsI scintillator) 221 in a front view.

  Although not shown, the radiation dosimeter 22 incorporates a wireless communication device such as Bluetooth (registered trademark), for example, and is configured to be able to wirelessly communicate with an external device. Since the radiation dosimeter 22 is accommodated in the tubular body 21, it is possible to acquire wireless communication and GPS through the internal space of the tubular body 21. Although not shown, the radiation dosimeter 22 is also provided with a connector to which a communication cable C such as a USB cable is connected. The communication cable C connected to the dosimeter 22 extends from the proximal end 21B of the cylindrical body 21 to the outside, and is connected to the external arithmetic unit 3.

  In this configuration, the sensing unit 221 of the radiation dosimeter 22 is housed so as to be exposed to the outside from the tip end 21A of the cylindrical body 21. Specifically, the sensing unit 221 of the dosimeter 22 is exposed to the outside from the axial direction distal end surface (the outer surface 211 a of the distal end wall 211) of the cylindrical body 21. More specifically, the radiation dosimeter 22 is fitted in the through hole formed in the tip wall 211 of the cylindrical body 21 so that the sensing unit 221 is exposed to the outside. In addition, the part exposed outside from the axial direction front end surface 211a of the cylindrical body 21 is covered by the protective cover 21p. Here, the exposed portion and the protective cover 21p are in proximity or in contact with each other to such an extent that the attenuation effect of the radiation can be ignored. The protective cover 21p also plays a role of ensuring liquid tightness between the radiation dosimeter 22 and the through hole.

  Furthermore, in the cylindrical body 21, at least a part on the proximal end side of the distal end portion 21A to which the dosimeter 22 is attached is thinner. In the tubular body 21 of the present embodiment, the entire proximal end excluding the distal end portion is thin. That is, the cylindrical body 21 has the large diameter part 21x including the tip 21A to which the dosimeter 22 is attached, and the small diameter part 21y having a diameter smaller than that of the large diameter part 21x. In addition, the base end side of this small diameter part 21y turns into a holding part held by a user.

Thus, the tubular body 21 of the present embodiment is provided with a depth display unit 23 that indicates the immersion depth of the radiation dosimeter 22.
The depth display portion 23 is a scale displayed along the axial direction on the outer peripheral surface of the cylindrical body 21. This scale has a plurality of scale lines 23a. The scale line 23 a is displayed based on the position of the sensing unit 221 of the radiation dosimeter 22, and indicates the distance from the sensing unit 221. Further, in the present embodiment, a notation 23b such as a numerical value or a unit of the distance from the sensing unit 221 is displayed along with a predetermined scale line 23a.

  The arithmetic unit 3 receives radiation dose data indicating the spatial radiation dose rate (μSv / h) from the radiation dosimeter 22 and calculates the radioactivity concentration (Bq / L). The device configuration is a general-purpose or dedicated computer comprising a CPU, a memory, an input / output interface, an AD converter, etc. (not shown), and the CPU and its peripheral devices are based on a program stored in a predetermined area of the memory. Operate. In addition, it may be configured not to use the CPU but to perform the function as the above each part by only the analog circuit, or it is necessary to be physically integrated such that a part of the function is shared with an external personal computer etc. Instead, it may be composed of a plurality of devices connected to each other by wire or wireless.

  Specifically, as shown in FIG. 1, the arithmetic unit 3 stores relational equation data storing unit 31 that stores relational equation data indicating the relationship between the spatial radiation dose rate (μSv / h) and the radioactivity concentration (Bq / L). And a concentration calculation unit 32 which calculates the radiation concentration using the relational expression data and the radiation dose data.

  As shown in FIG. 3, the relational expression data storage unit 31 stores relational expression data indicating a relational expression indicating a relationship between the spatial radiation dose rate and the radioactivity concentration. The relational data is obtained in advance from the contaminated water in the water storage tank WT. Specifically, the spatial radiation dose rate (μSv / h) of gamma rays by radioactive cesium (Cs134, Cs137), and radioactive cesium Shows the relationship with the radioactivity concentration (Bq / L) of

  The concentration calculation unit 32 acquires relational expression data from the relational expression data storage unit 31, acquires radiation dose data from the radiation dosimeter 22, and calculates the radiation concentration using these. Then, the concentration calculation unit 32 outputs radioactivity concentration data indicating the radioactivity concentration to the output device 4 such as a display.

According to the radioactivity concentration measuring apparatus 100 configured as described above, the following effects can be obtained.
That is, since the depth display part 23 which shows the immersion depth of the dosimeter 22 is provided in the cylindrical body 21, the immersion depth of the dosimeter 22 can be grasped | ascertained easily. Thereby, the dosimeter 22 can be installed in the immersion depth optimal with respect to the water depth of contaminated water. Therefore, without performing background measurement, radiation dose and radioactivity concentration can be measured without being affected by ambient radiation dose.
Even when the dosimeter 22 is installed obliquely from the edge of the storage tank WT by providing the depth display portion 23, from the scale on the water surface and the inclination of the cylinder 21, from the water surface You can grasp the immersion depth of As a result, the cylindrical body 21 need not necessarily be installed along the vertical direction, and a dedicated attachment member for installing along the vertical direction can be omitted.
Further, since the sensing unit 221 of the dosimeter 22 is exposed to the outside from the tip 21A, the attenuation by the air layer can be prevented, and the measurement sensitivity can be increased.
Furthermore, in the cylindrical body 21, at least a part on the proximal end side of the distal end 21A is thinner than the distal end 21A. The buoyancy can be reduced as compared with the case of immersing cylindrical bodies of the same thickness, and the immersing operation can be facilitated.

  The present invention is not limited to the above embodiment.

  For example, the depth display unit is not limited to the scale and numerical values described in the above embodiment, as long as the depth can be recognized, and may be a scale, numerical values, characters, symbols or the like.

  Further, as the depth display unit, a water depth sensor may be provided at the tip of the cylindrical body or in the vicinity of the dosimeter, and the water depth obtained by the water depth sensor may be displayed.

  Furthermore, in the relational expression data, the relational expression (specifically, the slope) changes with the passage of time. For this reason, a relational expression data correction unit that corrects the inclination or the like of the relational expression may be provided based on the elapsed time since the generation of the relational expression data.

  Furthermore, as shown in FIG. 4, the radiation measurement unit of the embodiment may be provided with a propeller 5 for lowering the tip 21A of the cylindrical body 21 in the contaminated water.

  Specifically, the propeller 5 is provided to face the axial front end surface 211 a and the sensing portion 221 exposed to the front end surface 211 a. The propeller 5 is fixed to the cylindrical body 21 by the support member 6, and has a rotary wing 51 rotating around a rotation axis coaxial with the axial direction of the cylindrical body 211, and a motor for rotating the rotary wing 51. It has 52 and. Then, when the motor 52 rotates the rotary wing 51, a water flow is generated in the direction in which the tip 21A is immersed, and the tip 21A is lowered. In addition, the contaminated water can be stirred by the water flow generated by the propeller 5, and the radioactive substance deposited can be dispersed to accurately measure the radiation amount of the contaminated water. Furthermore, the polluted water stirred by the propeller 5 hits the sensing unit 221, and the sensing unit 221 can be cleaned and adhesion of dirt to the sensing unit 221 can be prevented.

  The propeller 5 is not limited to the above as long as it can move down the tip 21A such as the side of the tip 21A of the cylindrical body 21 in addition to the position facing the axial tip 211a. .

  In addition, the number of revolutions of the propeller motor may be changed. Specifically, since the buoyancy increases as the immersion depth of the dosimeter increases, it is conceivable that the number of rotations of the motor can be changed manually or automatically according to the immersion depth.

  Furthermore, although the radiation dosimeter of the said embodiment used the CsI (Tl) scintillator, you may use gamma ray space dosimeter other than NaI (Tl) scintillator etc. besides it.

  In addition, although the radioactivity concentration measuring device of the above-mentioned embodiment measures the radioactivity level of the drainage generated by decontamination work, others, such as drinking water, sewage, agricultural settlement drainage, fishing settlement drainage etc. It can also be used to measure the level of radioactivity.

  In addition, the present invention is not limited to the embodiment described above, and various modifications can be made without departing from the scope of the invention.

100 · · · Radioactivity concentration measuring device 2 · · · Radiation measuring unit 21 · · · Cylindrical body 21A · · · Tip portion 211a · · · · · · tip end surface 22 · · · dosimeter 23 · · · depth Display unit 221 ··· Sensing unit 3 · · · Operation unit 5 · · · Propeller 6 · · · Support member

Claims (6)

A radiation measurement unit which is immersed in a test solution to measure the radiation dose of the test solution,
A cylindrical body to be immersed in the test solution;
A radiation dosimeter housed at the tip of the cylindrical body;
A radiation measurement unit comprising: a depth indicator provided on the cylindrical body to indicate the immersion depth of the radiation dosimeter.   The radiation measurement unit according to claim 1, wherein the sensing unit of the dosimeter is exposed to the outside from the tip portion.   The radiation measurement unit according to claim 1 or 2, wherein at least a part on the proximal side of the distal end of the cylindrical body is thinner.   The radiation measurement unit according to any one of claims 1 to 3, further comprising a propeller provided on the cylindrical body for lowering the tip portion in the test solution. The sensing portion of the radiation dosimeter is exposed to the outside from an axial tip end surface of the cylindrical body,
The radiation measurement unit according to claim 4, wherein the propeller is provided to face the axial front end surface. A radiation measurement unit according to any one of claims 1 to 5;
And a calculation unit for calculating the radioactivity concentration of the test solution using the radiation dose obtained by the radiation measurement unit as a parameter.