JP2014169943A - Radiation measurement device and radiation measurement program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a decontamination effect of a decontamination work to be correctly determined or a place required for the decontamination work to be correctly determined.SOLUTION: A radiation measurement device comprises: a first radiation detector 2 that has a directional characteristic indicative of peak sensitivity in a first direction; a second radiation detector 3 that has a directional characteristic indicative of peak sensitivity in a second direction; a computation section 5 that, with a first radiation dose Sof the first radiation detector 2 as a reference, computes a ratio Rof a second radiation dose Sof the second radiation detector 3 to the referenced first radiation dose S; a display control section 6 that displays the first and second radiation doses Sand Sof the two radiation detectors 2 and 3, and the ratio Robtained by the computation section 5 on a screen.

Description

  The present invention relates to a radiation measuring apparatus.

  The decontamination work of the radioactive material includes a work of scraping off the top soil to which the radioactive material is attached, a work of removing branches and leaves, or a cleaning work of the building surface. And conventionally, in order to confirm the decontamination effect by the decontamination work, the radiation dose before the work of the decontamination work is compared with the radiation dose after the work using the radiation measuring device.

  However, in addition to the radiation dose emitted from the decontamination target location, the radiation dose measured by the radiation measurement device is the radiation released upward from the radiation material on the ground, scattered by the atmosphere, and returned to the ground. Amount (radiation dose due to skyshine) is included (see FIG. 3). Then, even after decontamination, the radiation dose due to Skyshine is measured (see the lower figure in FIG. 3), and only the radiation dose actually emitted from the decontamination target location is not measured. It is difficult to judge accurately.

  In addition, even when measuring the radiation dose with a radiation measurement device when specifying the location where decontamination work is required, the measured radiation dose includes not only the radiation dose emitted from the decontamination target location but also the sky dose. The radiation dose due to Shine is included, and it is difficult to accurately determine whether decontamination work is necessary (see the lower diagram of FIG. 3). Furthermore, by decontaminating a certain decontamination target location, the radiation dose measured at a location adjacent to the decontamination target location is also reduced (see the lower figure in FIG. 3). It is difficult to accurately determine whether or not the adjacent location needs to be decontaminated.

  In addition, as shown in Patent Document 1, a plurality of radiation detectors are provided in the circumferential direction so that the direction characteristics are different from each other, and the total of the measurement values obtained by the plurality of radiation detectors and radiation detection directed in a predetermined direction A radiation measuring device that identifies the direction of radiation radiation by calculating the ratio of the measured value to the measured value of the instrument has been considered.

  However, this radiation measurement device uses the sum of the measurement values of a plurality of radiation detectors arranged in the circumferential direction, and does not consider the influence of the radiation dose due to Skyshine. There are problems that it is difficult to determine the effect and it is difficult to specify a place where decontamination work is necessary.

JP 2007-155332 A

  Therefore, the present invention has been made to solve the above-mentioned problems all at once, so that the decontamination effect of the decontamination work can be accurately judged or the place where the decontamination work is necessary can be specified accurately. This is the main issue.

  That is, the radiation measuring apparatus according to the present invention includes a first radiation detector having a directional characteristic that exhibits a peak sensitivity in a direction in which a change in radiation dose, which is the first direction, is small, and a peak sensitivity in a second direction different from the first direction. Obtained by the second radiation detector with respect to the first measurement result set as a reference, with the second radiation detector having a directional characteristic indicating the first measurement result obtained by the first radiation detector as a reference. And a calculation unit that calculates a relationship value that is a value indicating the relationship between the second measurement results, and an output unit that outputs the relationship value obtained by the calculation unit.

If it is such, the 1st radiation detector has the direction characteristic which shows a peak sensitivity in the direction where the change of the radiation dose by decontamination is small, The 1st measurement result obtained by the 1st radiation detector Since the relationship value which shows the relationship of the 2nd measurement result obtained by the 2nd radiation detector with respect to is output, there exist the following effects.
In other words, the determination of the decontamination effect of the decontamination work or the identification of the location where decontamination is necessary is not determined by the measurement result of the radiation detector (for example, the radiation dose) but by the relational value. The influence of the radiation dose or the radiation dose emitted from the surrounding radioactive material can be suppressed and performed accurately. As described above, the present invention outputs the relation value of the second measurement result obtained by the second radiation detector with respect to the first measurement result obtained by the first radiation detector. It was made for the first time when it was found to be meaningful in the determination of the above or the identification of the place where decontamination is necessary.

It is desirable that the first direction is set in a vertically upward direction.
As a result, the first radiation detector measures the radiation dose in the sky. The amount of radiation in the sky is the amount of radiation due to Skyshine, and the amount of change before and after the decontamination work is the smallest. The location where decontamination work is required can be identified more accurately.

The relation value is preferably a ratio between the first measurement result and the second measurement result.
In this case, it is only necessary to obtain a ratio of measurement results (for example, radiation doses) obtained by the respective radiation detectors, and the arithmetic processing of the arithmetic unit can be extremely simplified. In addition, since the relation value is a ratio, it is possible to simplify the determination by the user.

The output unit is a display control unit that displays on the screen the relationship value obtained by the calculation unit, the display control unit, the relationship value obtained by radiation measurement before decontamination of radioactive material, It is desirable to display the relation value obtained by radiation measurement after decontamination of the radioactive substance on the screen simultaneously or by switching.
In this case, since the relation values before and after the decontamination work can be compared on the same screen, the judgment by the user can be simplified.

A third radiation detector having a directional characteristic exhibiting peak sensitivity in a third direction different from the first direction and the second direction, wherein the arithmetic unit is configured to perform the first measurement result as the reference; Calculating a relation value which is a value indicating a relation between the second measurement result of the second radiation detector and the third measurement result of the third radiation detector, and the first direction is set in a vertically upward direction. Preferably, the second direction is set in a vertically downward direction, and the third direction is set in a horizontal direction.
In this case, since the first direction is set vertically upward and the second direction is set vertically downward, the determination of the decontamination effect is determined by the relation value of the second measurement result with respect to the first measurement result. Can do. In addition, since the third direction is set to the horizontal direction, it is possible to determine the location where decontamination is necessary based on the relationship value of the third measurement result with respect to the first measurement result. That is, after the decontamination work, it is possible to determine the decontamination effect at the decontamination site, and at the same time, specify a place where decontamination is necessary around the decontamination site.

  In addition, the radiation measurement program according to the present invention includes a first radiation detector having a directional characteristic that exhibits peak sensitivity in a direction in which a change in radiation dose, which is the first direction, is small, and a peak in a second direction different from the first direction. A radiation measurement program used in a radiation measurement apparatus including a second radiation detector having a directional characteristic indicating sensitivity, wherein the first measurement result obtained by the first radiation detector is used as a reference. A calculation unit that calculates a relationship value that is a value indicating a relationship of the second measurement result obtained by the second radiation detector with respect to the first measurement result; and an output unit that outputs the relationship value obtained by the calculation unit; The computer is provided with the functions as described above.

  According to the present invention configured as described above, the relationship between the second measurement result obtained by the second radiation detector with respect to the first measurement result is obtained with reference to the first measurement result obtained by the first radiation detector. Since the relationship value shown is output, the decontamination effect of the decontamination work can be accurately determined, or the place where the decontamination work is necessary can be accurately identified.

The schematic diagram which shows the structure of the radiation measuring device of this embodiment. The perspective view and sectional drawing which show the structure of the radiation detector of the embodiment. The schematic diagram which shows the radiation dose etc. by the Skyshine before and after decontamination.

  The radiation measuring apparatus according to the present invention will be described below with reference to the drawings.

  The radiation measuring apparatus 100 according to the present embodiment is capable of simultaneously measuring radiation doses in three directions, and as shown in FIG. 1, a first radiation detector having a directional characteristic indicating peak sensitivity in the first direction. 2 and a second radiation detector 3 having a direction characteristic indicating peak sensitivity in a second direction different from the first direction, and a direction characteristic indicating peak sensitivity in a third direction different from the first direction and the second direction. And a third radiation detector 4.

  As shown in FIGS. 1 and 2, each of the radiation detectors 2 to 4 includes a scintillator 10 such as a CsI (Tl) scintillator that emits light by radiation, a photodiode (silicon photodiode) that detects light emission of the scintillator 10, and the like. The photodetector 11 is provided.

  As shown in FIG. 2 in particular, the scintillator 10 has a columnar shape. The scintillator 10 has an incident surface 10a on which radiation is incident on one surface, and an exit surface 10b that emits scintillation light. And the light-receiving surface 11a of the photodetector 11 is provided facing this emission surface 10b. The scintillator 10 of this embodiment has a quadrangular prism shape.

  In the scintillator 10, five surfaces except the incident surface 10a are covered with a shielding member 12 such as a lead plate having a thickness of 8 mm, for example, and radiation (specifically, gamma rays) incident on a surface other than the incident surface 10a. It is set as the structure which attenuates. Further, the photodetector 11 facing the emission surface 10 b of the scintillator 10 is also covered with the shielding member 12 together with the scintillator 10. Thereby, each radiation detector 2-4 has a directional characteristic which shows a peak sensitivity in the direction which the entrance plane 10a faces.

  As shown in FIG. 1, the three radiation detectors 2 to 4 are set so that the incident surface 10 a of the first radiation detector 2 faces in the vertically upward direction, and the incident surface 10 a of the second radiation detector 3. Is set to face in the vertically downward direction, and the incident surface 10a of the third radiation detector 4 is set to face in the horizontal direction. That is, the incident surface 10a of the first radiation detector 2 and the incident surface 10a of the second radiation detector 3 are arranged to face in opposite directions, and the incident surface 10a of the third radiation detector 4 It arrange | positions so that the direction orthogonal to the opposing surface of the entrance plane 10a of the 1 radiation detector 2 and the entrance plane 10a of the said 2nd radiation detector 3 may face. Accordingly, the first radiation detector 2 has a directional characteristic indicating peak sensitivity in the vertically upward direction, the second radiation detector 3 has a directional characteristic indicating peak sensitivity in the vertically downward direction, and the third radiation detector 4 has a directional characteristic indicating peak sensitivity in the horizontal direction.

  And the radiation measuring apparatus 100 of this embodiment acquires a light intensity signal from each photodetector 11 of the said three radiation detectors 2-4, and the dose equivalent rate (dose equivalent per unit time) which is a radiation dose. ) Is provided.

The calculation unit 5 uses the first radiation dose S ₁ that is the first measurement result of the first radiation detector 2 as a reference, and the second measurement of the second radiation detector 3 with respect to the first radiation dose S ₁ as the reference. Relation values R ₁ and R ₂ , which are values indicating the relationship between the second radiation dose S ₂ as the result and the third radiation dose S ₃ as the third measurement result of the third radiation detector 4, are calculated. The calculation unit 5 of the present embodiment uses, as the relation values R ₁ and R ₂ , the radiation dose ratio (R ₁ = S) between the first radiation dose S ₁ and the second radiation dose S ₂ and the third radiation dose S _{3. 2 / S 1, R 2 =} S 3 / S 1) for calculating a.

Furthermore, the radiation measuring apparatus 100 of the present embodiment is a display control that is an output unit that displays the radiation doses S _{1 to} S ₃ and the radiation dose ratios R ₁ and R ₂ obtained by the calculation unit 5 on the screen of the display 7. Part 6 is provided.

The display control unit 6 acquires radiation dose data and radiation dose ratio data from the calculation unit 5 and displays the radiation doses S _{1 to} S ₃ of the _three radiation detectors 2 to 4 on the screen of the display 7. At the same time, the radiation dose ratios R ₁ and R ₂ are displayed on the screen simultaneously with or while switching the radiation doses S _{1 to} S ₃ . When switching and displaying on the screen, it is conceivable that the display is switched by the user pressing a display switching button (not shown) provided in the radiation measuring apparatus 100. In addition, it may be configured to automatically switch and display.

Moreover, the display control part 6 is obtained by the radiation dose ratio (R1 _{(before decontamination)} , R2 _{(before decontamination)} ) obtained by the radiation measurement _{before the} decontamination work, and the radiation measurement after the decontamination work. The obtained radiation dose ratios (R _{1 (after decontamination)} , R _{2 (after decontamination)} ) are displayed on the screen simultaneously or switched.

Radiation dose before decontamination work (S1 _{(before decontamination) to} S3 _{(before decontamination)} ) and radiation dose ratio (R1 _{(before decontamination)} , R2 _{(before decontamination)} ) are measured by the radiation measuring apparatus 100. The display control unit 6 stores the radiation dose (S1 _{(before decontamination) to} S3 _{(before decontamination)} ) and the radiation dose ratio (R) stored in the memory before the decontamination work. _{1 (before decontamination)} and R2 _{(before decontamination)} ) are read out and displayed on the screen.

  Next, a method for using the radiation measuring apparatus 100 configured as described above will be described.

First, before decontamination, using said radiation measuring device 100, dividing the radiation dose of the dye target location _{(S 1 (decontamination ago)} to S _{3 (decontamination ago))} and radiation amount ratio _{(R 1 (except Before dyeing)} and R _{2 (before decontamination)} ). At this time, the radiation measuring apparatus 100 is measured at a predetermined height (for example, a height of 1 m from the ground) from the decontamination target location. The third radiation detector 4 is rotated once in the vertical direction, and the radiation dose S _{2 (before decontamination)} (radiation dose ratio R _{2 (exclusion} ) at a plurality of surrounding points (for example, four points in the east, west, south, and north _)). It is conceivable to measure _{before dyeing))} ).

Then, the after decontamination of the decontamination object location, by using the radiation measurement device 100, the radiation amount of the decontamination object location (S 1 _{(after decontamination)} to S 3 _{(after decontamination))} and The radiation dose ratio (R _{1 (after decontamination)} , R _{2 (after decontamination)} ) is measured. At this time, the radiation measuring apparatus 100 is arranged at the same position before and after decontamination. In addition, the third radiation detector 4 is rotated around the vertical direction once, and the radiation dose S _{2 (after decontamination)} (radiation dose ratio R _{2 (exclusion} ) at a plurality of surrounding points (for example, 4 points in the east, west, south, and north _{)). After dyeing))} ) may be measured.

Then, the radiation dose ratio R ₁ before decontamination work _{(before decontamination)} and _{decontamination} calculated from the first radiation dose S ₁ of the first radiation detector 2 and the second radiation dose S ₂ of the second radiation detector 3. By comparing the radiation dose ratio R1 _{(after decontamination)} after the dyeing work, the decontamination effect at the decontamination target location is determined.

Further, the radiation dose ratio R ₂ before decontamination work calculated by the first radiation dose S ₁ of the first radiation detector 2 before the decontamination work and the third radiation dose S ₃ of the third radiation detector 4 _(removal) By comparing the radiation dose ratio R2 ₍ after decontamination _{) before} and after decontamination, a place where decontamination is necessary around the decontamination target place is specified. Here, as described above, after decontamination before and decontamination operations, by one rotation of the third radiation detector 4 in the vertical direction around keep measuring the radiation dose ratio R ₂ at a plurality of points around This makes it easy to identify a place where decontamination is required.

Next, the radiation dose and radiation dose before and after decontamination work on the farm road (at a height of 1 m from the ground) when decontamination work is performed by scraping off the topsoil of the farm road at an actual certain place in Fukushima Prefecture The ratios are shown in Tables 1 and 2 below. Incidentally, Table 1, the radiation amount before decontamination farm roads _{(S 1 (decontamination ago)} to S _{3 (decontamination ago))} and radiation amount ratio _{(R 1 (decontamination before), R 2 (decontamination} respectively _to the _front)), Table 2, the radiation dose after decontamination of farm roads _{(S 1 (after decontamination)} to S _{3 (after decontamination))} and radiation amount ratio _{(R 1 (after decontamination),} R _{2 (after decontamination)} ).

The decontamination of farm roads, it can be seen that the second radiation amount S ₂ of the second radiation detector 3 which measures the radiation amount of farm roads is reduced. It can also be seen that by decontaminating the farm road, the radiation dose in the farmland direction is reduced from 1.344 (μSv / h) to 0.964 (μSv / h). That is, if the radiation dose in the direction of the farmland is measured after the agricultural road decontamination and the radiation dose is determined, it may not be determined that the decontamination work is necessary.

On the other hand, looking at the dose ratio R _1, in the farm roads decontamination is, the radiation dose ratio has decreased from 1.75 to 0.78, is possible to determine that the decontamination effect it can. In farmland, the radiation dose ratio is slightly reduced from 1.59 to 1.53, but is hardly changed. Thus, by comparing the dose ratio R _2, it can be farmland to accurately determine if there where needed for decontamination.

<Effect of this embodiment>
According to the radiation measuring apparatus 100 according to the present embodiment configured as described above, the second radiation dose S ₂ and the third radiation detection of the second radiation detector 3 with respect to the first radiation dose S ₁ of the first radiation detector ₂ . Since the radiation dose ratios R ₁ and R ₂ of the third radiation dose S ₃ of the device 4 are displayed on the screen, the change between the radiation dose before decontamination and the radiation dose after decontamination is represented by the radiation dose ratio R ₁ , can be judged by R _2, it is possible to accurately grasp the effect of decontamination. Moreover, when grasping the place where decontamination is necessary, the radiation dose of the radiation coming from the place side can be determined by the radiation dose ratios R ₁ and R ₂ , and the decontamination effect can be grasped accurately. be able to.
As described above, in the radiation measuring apparatus 100 according to the present embodiment, the decontamination effect of the radioactive substance and the place where decontamination is necessary are not determined by the radiation doses S _{1 to} S ₂ of the radiation detectors 2 to 4 but the sky. Judgment is made based on the radiation dose ratios R ₁ and R _{2 based} on the radiation dose S ₁ coming from the sky. Therefore, the effects of the radiation dose caused by Skyshine and the radiation dose emitted from the surrounding radioactive materials are suppressed and accurately grasped. can do.

The present invention is not limited to the above embodiment.
For example, in the above-described embodiment, the three radiation detectors 2 to 4 are arranged in different directions. However, the four or more radiation detectors have direction characteristics indicating peak sensitivity in different directions. It may be arranged. Thus, as the number of radiation detectors is increased, the radiation dose in more directions can be measured simultaneously.

Further, in the above embodiment, the direction characteristic of the first radiation detector 2 for measuring a first amount of radiation S ₁ serving as a reference was vertically upward direction, other, in the direction the radiation amount is small before and after the decontamination If there is, it is not limited to the vertically upward direction.

  Further, the scintillator 10 of the above embodiment has a quadrangular column shape, but may have a columnar shape, or may have a flat plate shape in addition to the columnar shape.

  In addition, the scintillator 10 may be a NaI (Tl) scintillator in addition to the CsI (Tl) scintillator. In addition to the scintillation method, the radiation detector may be a detector of another method such as a GM counter type or a semiconductor type.

  In addition, the radiation detector may be one that detects beta rays, X-rays, etc. in addition to those that detect gamma rays. At this time, various scintillators can be used in addition to the CsI (Tl) scintillator and the NaI (Tl) scintillator.

  Furthermore, the radiation measurement apparatus may include a GPS receiver, and the radiation dose and the radiation dose ratio in each radiation measurement may be stored in the memory in association with the measurement position (latitude / longitude). If it is this, decontamination work and its management can be efficiently performed by mapping the decontamination place and the radiation dose and the radiation dose ratio of the place.

  In addition, in the embodiment described above, the radiation dose ratio before the decontamination work and the radiation dose ratio after the decontamination work are compared to identify the place where the decontamination work is necessary. You may make it identify the place which needs decontamination work using only a radiation dose ratio. That is, the third radiation detector may be rotated around the vertical direction, and a place showing a ratio of a predetermined value or more in the radiation dose ratio obtained at that time may be specified as a place where decontamination work is necessary.

In the embodiment, the radiation dose ratio between the first radiation dose S ₁ and the second radiation dose S ₂ is calculated as the relation values R ₁ and R _2. The difference between the dose S ₁ and the second radiation dose S ₂ or the like may be used, or any other value that indicates the relationship between the other first radiation dose S ₁ and the second radiation dose S ₂ or the like.

  Moreover, in the said embodiment, although the output part is comprised by the output display part which displays the related value obtained by the calculating part on a screen, you may print on paper and output, You may transmit to another another portable terminal and computer.

  In addition, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Radiation measuring apparatus 2 ... 1st radiation detector 3 ... 2nd radiation detector 4 ... 3rd radiation detector 5 ... Calculation part 6 ... Display control part (output part) )

Claims (6)

A first radiation detector having a directional characteristic that exhibits peak sensitivity in a direction in which a change in radiation dose, which is a first direction, is small;
A second radiation detector having a directional characteristic exhibiting peak sensitivity in a second direction different from the first direction;
A relation value which is a value indicating a relation of the second measurement result obtained by the second radiation detector with respect to the first measurement result based on the first measurement result obtained by the first radiation detector. A computing unit for computing
A radiation measurement apparatus comprising: an output unit that outputs a relational value obtained by the calculation unit.   The radiation measuring apparatus according to claim 1, wherein the first direction is set in a vertically upward direction.   The radiation measurement apparatus according to claim 1, wherein the relation value is a ratio between the first measurement result and the second measurement result. The output unit is a display control unit for displaying a relation value obtained by the calculation unit on a screen;
The display control unit displays the relation value obtained by radiation measurement before decontamination of the radioactive substance and the relation value obtained by radiation measurement after decontamination of the radioactive substance on the screen at the same time or by switching. The radiation measuring apparatus according to any one of claims 1 to 3. A third radiation detector having a directional characteristic showing peak sensitivity in a third direction different from the first direction and the second direction;
The calculation unit calculates a relation value that is a value indicating a relation between the second measurement result of the second radiation detector and the third measurement result of the third radiation detector with respect to the first measurement result as the reference. And
The first direction is set in a vertically upward direction;
The second direction is set in a vertically downward direction;
The radiation measuring apparatus according to claim 1, wherein the third direction is set in a horizontal direction. A first radiation detector having a directional characteristic exhibiting peak sensitivity in a direction having a small change in radiation dose, which is the first direction, and a second radiation detecting having a directional characteristic exhibiting peak sensitivity in a second direction different from the first direction; A radiation measurement program for use in a radiation measurement apparatus comprising:
A relation value which is a value indicating a relation of the second measurement result obtained by the second radiation detector with respect to the first measurement result based on the first measurement result obtained by the first radiation detector. A radiation measurement program for causing a computer to have a function as a calculation unit that calculates the above and an output unit that outputs a relation value obtained by the calculation unit.