JP2018063205A - Boron concentration meter and method for estimating boron concentration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boron concentration meter and a method for estimating boron concentration which are capable of highly accurately estimating boron concentration in liquid.SOLUTION: A concentration meter body 1a of a boron concentration meter 1 comprises: a measuring cell 10 for storing solution to be measured; a reference cell 20 for storing reference solution not containing boron; and a neutron source 30 for emitting fast neutrons toward the solution to be measured and the reference solution. Thermal neutrons converted from fast neutrons in the solution to be measured are detected by a first detector 11 while thermal neutrons similarly converted in the reference solution are detected by a second detector 21. An operation unit 60 estimates boron concentration in the solution to be measured, on the basis of the number of thermal neutrons detected in this way.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a boron concentration meter for measuring a boron concentration in a liquid and an estimation method thereof.

  Conventionally, various proposals have been made as methods for measuring the concentration of boron contained in a liquid. For example, in Patent Document 1, fast neutrons are emitted from a neutron source to a measurement object, and the number of thermal neutrons formed by converting the fast neutrons in the measurement object is measured by a thermal neutron detector. And the measuring method of the boron concentration which calculates | requires the density | concentration of the boron contained in the said measurement object from the measurement result is disclosed. In this measurement method, a relationship between a thermal neutron count ratio (a thermal neutron count value in a measurement object / a thermal neutron count value in a measurement reference body) and a boron concentration is obtained in advance, and the measurement target is determined based on the relationship. The concentration of boron in the object is estimated (Patent Document 1 (see [0020] and FIGS. 3 and 4). According to this measurement method, the sample is not measured and pretreated in the object to be measured. It becomes possible to continuously measure the boron concentration.

JP 2002-350369 A

  In the case of the conventional measurement method described above, the thermal neutron count ratio that is the basis for estimating the boron concentration is the ratio of the thermal neutron count value in the measurement object to the thermal neutron count value in the measurement reference body. Since the measurement is performed at different timings, it is extremely difficult to match the thermal neutron counting environment between the measurement reference body and the measurement object, and the measurement environments may be greatly different. Thus, the boron concentration obtained based on the counting ratio of thermal neutrons obtained under different counting environments may not be a highly reliable value.

  This invention is made | formed in view of such a situation, The main objective is to provide the estimation method of the boron concentration meter and boron concentration which can solve the said subject.

  In order to solve the above-described problem, a boron concentration meter according to an aspect of the present invention includes a neutron beam source that emits fast neutrons, and a first solution that contains a solution to be measured from which fast neutrons are emitted by the neutron beam source. Fast neutrons are generated by the measurement unit including a storage unit, a first detector that detects thermal neutrons generated by conversion of fast neutrons in the solution to be measured stored in the first storage unit, and the neutron source. A second container that contains a reference solution that is emitted and does not contain boron, and a second detector that detects thermal neutrons generated by converting fast neutrons in the reference solution contained in the second container An estimation means for estimating a boron concentration in the solution to be measured based on the number of thermal neutrons detected by the first detector and the number of thermal neutrons detected by the second detector With.

  In this aspect, it is preferable that the accommodating spaces of the first accommodating portion and the second accommodating portion have a line-symmetric shape with the neutron source as a center.

  In the above aspect, it is preferable that the first detector and the second detector are provided symmetrically about the neutron source.

  Further, in the above aspect, the measurement cell has an inflow port for allowing the solution to be measured to flow into the first storage part, and an outflow port for allowing the solution to be measured to flow out of the first storage part. It is preferable.

  The boron concentration estimation method according to one aspect of the present invention includes a neutron source, a measurement cell including a first storage unit that stores a solution to be measured, and a reference cell including a second storage unit that stores a solution for reference. A method for estimating a boron concentration for estimating a boron concentration in the solution to be measured, using the solution to be measured contained in the first container and the reference contained in the second container Radiating fast neutrons from a neutron source to the solution; detecting thermal neutrons generated by converting fast neutrons in the solution to be measured and in the reference solution; and detecting the measured Estimating the boron concentration in the solution to be measured based on the number of thermal neutrons in the solution and the number of thermal neutrons in the reference solution.

  According to the boron concentration meter and the boron concentration estimating method according to the present invention, it is possible to obtain a highly reliable estimated value for the boron concentration in the liquid.

The block diagram which shows typically the structure of the boron concentration meter which concerns on embodiment. The front view which shows the structure of the concentration meter main body which concerns on embodiment. The top view which shows the structure of the concentration meter main body which concerns on embodiment. FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. FIG. 5 is a cross-sectional view taken along line V-V in FIG. 2. The front view which shows the structure of a neutron beam source and a neutron beam source accommodating part. The graph which shows the relationship between the count difference of a thermal neutron, and a boron concentration. The flowchart which shows the procedure of a boron concentration estimation process.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, each embodiment shown below illustrates the method and apparatus for actualizing the technical idea of this invention, Comprising: The technical idea of this invention is not necessarily limited to the following. Absent. The technical idea of the present invention can be variously modified within the technical scope described in the claims.

(Configuration of boron concentration meter)
FIG. 1 is a block diagram schematically showing a configuration of a boron concentration meter according to the present embodiment. As shown in FIG. 1, the boron concentration meter 1 includes a concentration meter main body 1a and a control device 1b that estimates the boron concentration in the liquid based on information input from the concentration meter main body 1a. The control device 1b includes a first counter 40, a second counter 50, a calculation unit 60, a storage unit 70, and a display unit 80. For example, a personal computer can be used as the control device 1b.

  The densitometer body 1a includes a measurement cell 10 that contains a solution to be measured, which is a boron concentration measurement target, a reference cell 20 that contains a reference solution that does not substantially contain boron, and the solution to be measured and the reference solution. And a neutron beam source 30 that emits fast neutrons. Here, “substantially free of boron” means that the reference solution contains boron less than about 0.1 mg / L (1/10 of the water quality environmental standard). The storage space for each solution provided in each of the measurement cell 10 and the reference cell 20 is partitioned by a partition plate 31.

  The measurement cell 10 is connected to an inflow pipe 12 for allowing the solution to be measured to flow from the outside and an outflow pipe 13 for allowing the solution to be measured to flow out. The solution to be measured flows into the measurement cell 10 from the outside through the inflow pipe 12, and after the boron concentration is measured, it flows out to the outside through the outflow pipe 13.

  The measurement cell 10 includes a first detector 11 that detects thermal neutrons generated by converting fast neutrons in the solution to be measured. The first detector 11 is connected to the first counter 40 and outputs a signal indicating the detection result of thermal neutrons to the first counter 40. Similarly, the reference cell 20 includes a second detector 21 that detects thermal neutrons generated by converting fast neutrons in the reference solution. The second detector 21 is connected to the second counter 50, and outputs a signal indicating the detection result of thermal neutrons to the second counter 50.

  The first counter 40 and the second counter 50 count the number of thermal neutrons based on the signals input from the first detector 11 and the second detector 21, respectively, and send a signal indicating the counting result to the arithmetic unit 60. Output. The calculation unit 60 uses the signals input from the first counter 40 and the second counter 50 and the computer program and various data stored in the storage unit 70 to determine the boron concentration of the solution to be measured, as will be described later. The signal indicating the estimation result is output to the display unit 80. The display unit 80 displays information indicating the estimation result on the screen.

  Hereinafter, the detailed configuration of the densitometer body 1a will be described with reference to FIGS. 2 and 3 are a front view and a plan view showing the configuration of the concentration meter main body 1a according to the present embodiment, respectively. 4 and 5 are a sectional view taken along line IV-IV in FIG. 3 and a sectional view taken along line VV in FIG.

  As shown in FIGS. 2 to 5, the densitometer main body 1 a includes a cylindrical circular pipe portion 2. At both ends of the circular tube portion 2, disk-shaped tube plates 15, 15 that close the opening of the circular tube portion 2 are provided. Each tube sheet 15 is configured by laminating a first tube sheet 15a and a second tube sheet 15b. Two circular through holes are provided at positions corresponding to the measurement cell 10 and the reference cell 20 in the tube plate 15, and among these, the through holes provided at positions corresponding to the reference cell 20. Is closed by a closing member 26 for closing the through hole. On the other hand, the through-hole provided at the position corresponding to the measurement cell 10 is not blocked and communicates with the inflow pipe 12 and the outflow pipe 13. More specifically, a circular plate 16 having a through hole having the same diameter as the inner diameter of the inflow pipe 12 and the outflow pipe 13 is provided between the tube plates 15 and 15 and the inflow pipe 12 and the outflow pipe 13. Through the through hole of the circular plate 16, the through hole provided at a position corresponding to the measurement cell 10 in the tube plates 15 and 15, the inflow pipe 12 and the outflow pipe 13 communicate with each other. The circular plate 16 is configured by laminating a first circular plate 16a and a second circular plate 16b in which through holes are formed.

  The circular pipe part 2 is constituted by a measurement cell 10 and a reference cell 20. As shown in FIG. 4, the measurement cell 10 includes a first storage unit 14 that stores a solution to be measured, and the reference cell 20 includes a second storage unit 24 that stores a reference solution. These 1st accommodating parts 14 and the 2nd accommodating part 24 are comprised with the material which does not absorb a thermal neutron substantially. As shown in FIG. 5, the inside of the circular pipe portion 2 is divided into two spaces of the same shape that form a semi-cylindrical shape by the partition plate 31, and one of these spaces is the first storage portion 14. The accommodation space 14 a is provided, and the other is the accommodation space 24 a of the second accommodation portion 24. The sizes of the accommodating spaces 14a and 24a are not limited to specific ones, but considering the range in which the thermal neutrons move in the liquid, the radius R of the semi-cylinder is preferably 100 mm or less, and more preferably 50 mm or less.

  As shown in FIG. 4, in the first accommodating portion 14, an inlet 14 b and an outlet 14 c are provided at positions corresponding to the inlet pipe 12 and the outlet pipe 13, respectively. The storage space 14a of the first storage portion 14 and the inflow pipe 12 and the outflow pipe 13 communicate with each other through the inflow port 14b and the outflow port 14c. As a result, the solution to be measured flows into the accommodation space 14 a from the outside via the inflow pipe 12, and the solution to be measured flows out from the accommodation space 14 a to the outside via the outflow pipe 13. As a result, the boron concentration can be continuously measured as will be described later.

  A reference solution is sealed in the storage space 24 a of the second storage unit 24. The operator removes one of the blocking members 26, 26 to open the through hole of the tube plate 15, and supplies the reference solution to the storage space 24a through the through hole. Thereafter, the removed blocking member 26 is attached to the tube plate 15 to close the through hole, whereby the reference solution is sealed in the accommodation space 24a. In the present embodiment, the reference solution is a solution that does not substantially contain boron. For example, water or seawater is used as the reference solution.

  The partition plate 31 is provided with a cylindrical through hole penetrating in the vertical direction in FIG. 4, and a cylindrical neutron source housing portion 33 is accommodated in the through hole. The neutron beam source accommodating portion 33 is locked to the tube plate 15 by a locking tool 32 provided on the tube plate 15. The neutron beam source 30 is accommodated in the neutron beam source accommodating portion 33. The neutron source 30 is a source that emits fast neutrons in all directions, and for example, a californium 252 (Cf-252) neutron sealed source can be used. As shown in FIG. 6, the neutron beam source 30 has its tip portion exposed from the neutron beam source accommodating portion 33. The accommodation space 14 a of the first accommodation portion 14 and the accommodation space 24 a of the second accommodation portion 24 described above have a line-symmetric shape with the exposed portion from the neutron beam source accommodation portion 33 in the neutron beam source 30 as the center.

  The first detector 11 included in the measurement cell 10 is disposed to face the outer peripheral surface of the first housing part 14 and detects thermal neutrons that have passed through the first housing part 14. Similarly, the second detector 21 provided in the reference cell 20 is disposed so as to face the outer peripheral surface of the second housing part 24, and detects thermal neutrons that have passed through the second housing part 24. Here, the first detector 11 and the second detector 21 are provided symmetrically about the exposed portion of the neutron source 30 from the neutron source storage unit 33. As the first detector 11 and the second detector 21, for example, a He3 detector can be used.

Fast neutrons emitted from the neutron source 30 pass through the solution to be measured and the reference solution stored in the measurement cell 10 and the reference cell 20, respectively. At this time, some of the fast neutrons collide with the nuclei constituting each solution, decelerate, and are converted into thermal neutrons. Some of the thermal neutrons generated in this way collide with elements in the solution and are absorbed. Thermal neutrons are easily absorbed by relatively light elements. Table 1 shows the absorption cross section of thermal neutrons in the main relatively light elements.

  Fast neutrons radiated to each solution collide with a large amount of hydrogen atoms in the solution and decelerate to become thermal neutrons, which propagate in the solution. Here, when boron with a remarkably large absorption cross section of thermal neutrons is present in the solution, since most of the thermal neutrons are absorbed by the boron, the number of thermal neutrons in the solution decreases. . On the other hand, in a solution in which boron is not present and other elements different from boron are present, thermal neutrons are hardly absorbed by the other elements, so the number of thermal neutrons in the solution is extremely reduced. There are few. As described above, since the reference solution does not substantially contain boron in the present embodiment, the amount of thermal neutron reduction is larger in the solution to be measured than in the reference solution. Therefore, when thermal neutrons are counted in each solution, a difference occurs in the number. By obtaining the relationship between the count difference and the boron concentration in the solution to be measured in advance, it becomes possible to estimate the boron concentration in the solution to be measured as will be described later.

  Data indicating the relationship between the thermal neutron count difference and the boron concentration is stored in advance in the storage unit 70 of the control device 1b. Hereinafter, this relationship is referred to as a boron concentration calibration curve. FIG. 7 is a diagram showing an example of a graph of the boron concentration calibration curve. In this graph, the vertical axis represents the thermal neutron count difference (-(Nm-Mr) / min), and the horizontal axis represents the boron concentration (ppm) in the solution to be measured. Here, Nm represents the thermal neutron count value in the measurement cell 10, and Mr represents the thermal neutron count value in the reference cell 20.

  The calculation unit 60 of the control device 1b uses the difference in thermal neutron counts in the solution to be measured and the reference solution at the time of measuring the boron concentration and the boron concentration calibration curve to obtain the boron concentration in the solution to be measured. Is estimated.

  If boron is not present in the solution to be measured, the thermal neutron count difference between the solution to be measured and the reference solution should be almost zero. In practice, however, the direction of the neutron, the measurement cell 10 and In many cases, it does not become zero due to the manufacturing error of the reference cell 20 and the presence of thermal neutrons that cause disturbance in the measurement environment. Therefore, it is preferable to perform an operation in which the thermal neutron count difference in this case becomes zero. For example, a solution containing no boron is accommodated in the measurement cell 10 and the reference cell 20, and after fast neutrons are emitted from the neutron source 33, the thermal neutrons of each solution are counted, and the count value in the measurement cell 10 is specified. It is assumed that the difference between the counts is made zero by multiplying by a coefficient (hereinafter referred to as “correction coefficient”). In this embodiment, the count difference of thermal neutrons is calculated using this correction coefficient. Specifically, the difference between the value obtained by multiplying the thermal neutron count value in the measurement cell 10 by the correction coefficient and the thermal neutron count value in the reference cell 20 is defined as the thermal neutron count difference.

(Operation of boron concentration meter)
Next, the operation of the boron concentration meter 1 configured as described above will be described with reference to a flowchart. Below, the case where the boron density | concentration in the freshwater obtained from seawater in a seawater desalination plant is measured is mentioned as an example, and is demonstrated.

  The seawater desalination plant includes a tank for storing freshwater obtained from seawater. This tank and the inflow pipe 12 provided in the concentration meter main body 1a are connected, and fresh water can be continuously supplied from the tank to the inflow pipe 12. Thereby, fresh water (solution to be measured) is supplied to the accommodation space 14 a of the first accommodation portion 14 provided in the measurement cell 10 via the inflow pipe 12. On the other hand, in the accommodation space 24a of the second accommodation portion 24 provided in the reference cell 20, the reference solution substantially not containing boron is enclosed in advance as described above. Thus, advance preparation is completed.

  FIG. 8 is a flowchart showing the procedure of the boron concentration estimation process executed by the boron concentration meter of the present embodiment. As described above, after the solution to be measured and the reference solution are stored in the storage spaces 14a and 24a, fast neutrons are emitted from the neutron source 30 in all directions. Thus, fast neutrons are emitted from the exposed portion of the neutron source 30 from the neutron source storage unit 33 to the solution to be measured and the reference solution (S101). The fast neutrons emitted in this way propagate in each solution. When propagating in this way, some of the fast neutrons collide with the nuclei constituting each solution, decelerate, and are converted into thermal neutrons.

  Part of thermal neutrons converted from fast neutrons in the solution to be measured collides with the elements present in the solution to be measured and is absorbed. As described above, boron has a much larger absorption cross section of thermal neutrons than other elements, so most of thermal neutrons absorbed by the elements in the solution to be measured collide with boron and be absorbed. Become. On the other hand, thermal neutrons that have passed through the first housing part 14 without being absorbed by the element are detected by the first detector 11 provided on the outer peripheral surface of the first housing part 14 (S102).

  Further, a part of the thermal neutrons converted from fast neutrons in the reference solution collide with the elements present in the solution to be measured and are absorbed. However, since boron is not substantially present in the reference solution, most of the thermal neutrons pass through the second accommodating portion 24 without being absorbed. The thermal neutrons that have passed through the second accommodating portion 24 in this way are detected by the second detector 21 provided on the outer peripheral surface of the second accommodating portion 24 (S102).

  The above-described detection of thermal neutrons is performed for a certain time (for example, 1 minute), and signals indicating the detection results are sent from the first detector 11 and the second detector 21 to the first counter 40 and the second counter 50, respectively. Is output. Each of the first counter 40 and the second counter 50 counts the number of thermal neutrons in the measurement cell 10 and the reference cell 20 based on the input signals (S103), and outputs a signal indicating the counting result to the arithmetic unit 60. To do.

  The computing unit 60 calculates the thermal neutron count difference in the measurement cell 10 and the reference cell 20 based on the signals input from the first counter 40 and the second counter 50 (S104). At this time, the arithmetic unit 60 calculates the count difference after correcting the thermal neutron count value in the measurement cell 10 using the correction coefficient as described above.

  Next, the calculation unit 60 estimates the boron concentration in the solution to be measured by applying the calculated thermal neutron count difference to the boron concentration calibration curve stored in the storage unit 70 (S105). The boron concentration in the measured solution estimated in this way is displayed on the display unit 80 (S106).

  After the boron concentration in the solution to be measured is estimated as described above, the solution to be measured is discharged to the outside through the outflow pipe 13 from the storage space 14a of the first storage section 14, and the inflow pipe 12 The solution to be measured is exchanged by supplying the solution to be measured to the accommodation space 14a via. Thus, the boron concentration is continuously measured for the fresh water in the tank by repeatedly estimating the boron concentration and replacing the solution to be measured.

  As described above, in the case of the present embodiment, the neutron source 30 emits fast neutrons to the measurement cell 10 and the reference cell 20 at the same timing, and the measurement cell 10 and the reference cell 20 each have a high speed. Thermal neutrons generated by conversion of neutrons are detected, and the number is counted. Therefore, there is an advantage that the environment for counting thermal neutrons in the measurement cell 10 and the environment for counting thermal neutrons in the reference cell 20 to be compared with each other can be easily matched. It can be said that the boron concentration in the measured solution estimated based on the thermal neutron count difference obtained in this way is a highly reliable value.

  Further, in the case of the present embodiment, since the accommodation space 14a of the first accommodation portion 14 and the accommodation space 24a of the second accommodation portion 24 have a line-symmetric shape around the neutron radiation source 33, the counting of thermal neutrons The environment is more easily matched between the measurement cell 10 and the reference cell 20. In addition, since the first detector 11 and the second detector 21 are arranged symmetrically with respect to the neutron source 33, the counting environments are more easily matched. Therefore, it becomes possible to improve the reliability of the estimated value of the boron concentration.

(Other embodiments)
In the embodiment described above, the accommodation space 14a of the first accommodation portion 14 and the accommodation space 24a of the second accommodation portion 24 are semi-cylindrical, but the present invention is not limited to this, and other shapes such as a cylindrical shape are not limited thereto. Shape may be sufficient. Further, the accommodation space 14a of the first accommodation part 14 and the accommodation space 24a of the second accommodation part 24 have a line-symmetric shape around the neutron radiation source 30, but do not have a line-symmetric shape in this way. It doesn't matter. However, in order to increase the reliability of the estimated value of the boron concentration, it is preferable to have a line-symmetric shape with the neutron source 33 as the center as in the present embodiment.

  In the above-described embodiment, the first detector 11 and the second detector 21 are arranged line-symmetrically around the neutron source 33, but may not be arranged line-symmetrically. However, in order to improve the reliability of the estimated value of the boron concentration, it is preferable that the neutron source 33 is arranged symmetrically with respect to the center as in the present embodiment.

  The boron concentration meter and the boron concentration estimation method of the present invention are useful as a boron concentration meter and a boron concentration estimation method used in a seawater desalination plant, respectively.

DESCRIPTION OF SYMBOLS 1 Boron concentration meter 1a Concentration meter main body 1b Control apparatus 2 Circular pipe part 10 Measurement cell 11 1st detector 12 Inflow pipe 13 Outflow pipe 14 1st accommodating part 14a Accommodating space 14b Inlet 14c Outlet 15 Tube plate 20 Reference cell 21 2nd detector 24 2nd accommodating part 24a Accommodating space 30 Neutron beam source 31 Partition plate 32 Locking tool 33 Neutron beam source accommodating part 40 1st counter 50 2nd counter 60 Calculation part 70 Storage part 80 Display part

Claims (5)

A neutron source emitting fast neutrons;
A first container that contains a solution to be measured that emits fast neutrons from the neutron beam source, and thermal neutrons generated by the conversion of fast neutrons in the solution to be measured contained in the first container A measurement cell comprising a first detector;
Fast neutrons emitted from the neutron beam source, heat generated by conversion of the fast neutrons in the second container containing a reference solution containing no boron, and the reference solution contained in the second container A reference cell comprising a second detector for detecting neutrons;
A boron concentration meter comprising: estimation means for estimating a boron concentration in a solution to be measured based on the number of thermal neutrons detected by the first detector and the number of thermal neutrons detected by the second detector . The accommodation spaces of the first accommodation part and the second accommodation part have a line-symmetric shape around the neutron beam source,
The boron concentration meter according to claim 1. The first detector and the second detector are provided symmetrically about the neutron source.
The boron concentration meter according to claim 1 or 2. The measurement cell has an inflow port for allowing the solution to be measured to flow into the first storage part, and an outflow port for allowing the solution to be measured to flow out of the first storage part.
The boron concentration meter according to any one of claims 1 to 3. Estimating the boron concentration in the solution to be measured using a neutron beam source, a measurement cell including a first storage unit that stores a solution to be measured, and a reference cell including a second storage unit that stores a solution for reference A method for estimating boron concentration
Radiating fast neutrons from a neutron source for the solution to be measured contained in the first container and the reference solution contained in the second container;
Detecting thermal neutrons generated by conversion of fast neutrons in the solution to be measured and in the reference solution;
Estimating the boron concentration in the measured solution based on the detected number of thermal neutrons in the measured solution and the number of thermal neutrons in the reference solution.

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