JP2002006045A - Apparatus and method for measurement of concentration of tritium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus by which a concentration range required for the concentration of tritium in a liquid can be continuously measured in real time. SOLUTION: In order to continuously sense the beta rays of the tritium, a tritium concentration measuring apparatus which comprises a tritium-sensitive sensing end, a photoelectric conversion part used to convert a light signal into an electric signal and an electric measuring part used to measure the electric signal is provided, and a tritium concentration measuring method which uses the measuring apparatus is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for continuously measuring the concentration of tritium in a liquid such as cooling water or wastewater in facilities handling tritium such as nuclear fusion facilities and nuclear facilities.

[0002]

2. Description of the Related Art Conventionally, as a tritium concentration measuring apparatus for a liquid, there is a liquid scintillation counter with a special specification and a plastic scintillator used as a monitor by bremsstrahlung and a real-time monitor. In order to make these continuous monitoring devices, the former two need to make special modifications. The detection limit of the latter plastic scintillator is 4 × 10 ⁶ Bq /
cm ³ , the allowable concentration of tritium in wastewater (the concentration limit in wastewater or wastewater according to the Act on Disaster Prevention is 6 × 1
0 ¹ Bq / cm ³ ) cannot be measured.

[0003]

In order to make the above-mentioned liquid scintillation counter or monitor using bremsstrahlung a continuous monitoring device, it is necessary to make special modifications. In the case of measuring the tritium concentration in the waste water with a liquid scintillation counter, a mechanism is required in which a detection end cell packed with fluorescent agent particles is installed in a sample chamber and the waste water is introduced into the cell. In monitoring by bremsstrahlung, in order to obtain the amount of bremsstrahlung necessary for measurement, 40 MBq or more of tritium is required, and in order to obtain this total amount, some mechanism for concentrating tritium in the drainage liquid is required. On the other hand, the practical detection limit value of a plastic scintillator used as a continuous measuring device is about 4 × 10 ⁶ Bq / cm ³ , and the allowable sensitivity standard value of tritium in wastewater (“during drainage or The concentration limit in wastewater is 6 × 10 ¹ Bq / cm ³ )
The following concentrations cannot be measured directly: The present invention has been made in view of such circumstances, and provides an apparatus capable of real-time continuous measurement of a required concentration range of a tritium concentration in a liquid (for example, the above-described allowable concentration lower limit). It is intended to do so.

[0004]

SUMMARY OF THE INVENTION The present invention provides a tritium-sensitive detection end, a photoelectric conversion unit for converting an optical signal into an electric signal, and a measurement of the electric signal for continuously detecting a beta ray of tritium. Provided is a tritium concentration measurement device including an electric measurement unit that performs the measurement, and a tritium concentration measurement method using the same.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The tritium concentration measuring apparatus of the present invention continuously detects low-energy (average 5.7 KeV) beta rays of tritium. According to the configuration of the present invention,
If tritium is present in the drainage or drainage, the plastic scintillator or fluorescent fiber at the detection end emits light. This light emission is converted into an electric signal by a photoelectric converter directly or via an optical transmission fiber. If this electric signal is converted into a digital signal by the electric measuring unit and recorded, it is possible to continuously measure the presence of tritium in real time.

The tritium detecting end used in the present invention may be any one that emits light in response to tritium at a low concentration, and a thin plate or rod-shaped plastic scintillator or a fluorescent fiber is preferably used. Examples of the plastic scintillator include those in which a scintillator substance is put in a polymerized hydrocarbon matrix such as a polymerized substance obtained by dissolving an organic scintillator in a solvent composed of a styrene monomer or the like. For example, by using a bundle of rod-shaped plastic scintillators having an outer diameter of several millimeters, the presence of low-concentration lithium, which has been impossible up to now, can be directly measured. Examples of the fluorescent fiber include a fiber-shaped plastic scintillator having a plastic scintillator as a core, and a fiber having a large liquid contact area is preferable. By using a fluorescent plastic optical fiber having a large liquid contact area or a bundle of rod-shaped plastic scintillators having an outer diameter of several millimeters as a detection end, it is possible to directly measure the presence of tritium at a low concentration, which has been impossible until now. That is, as described above, the practical detection limit value of the plastic scintillator used as a continuous measurement device is about 4 × 10 ⁶ Bq / cm ³ , but the detection end using a 1000 fiber bundle is used. Thereby, measurement at a low concentration of about 8 × 10 ³ Bq / cm ³ becomes possible.

[0007] The photoelectric conversion unit converts the amount of light emitted from the detection end by radiation emitted from tritium into an electric signal. Examples of the photoelectric converter used in the photoelectric conversion unit include a photomultiplier tube, a PIN photodiode, and an avalanche.

In the present invention, if necessary, the light emitted from the detection end is condensed in the light condensing section, transmitted through an optical fiber or the like, and then subjected to photoelectric conversion to perform remote measurement and centralized management. Becomes possible. Although not particularly limited, a fluorescent optical fiber, an optical guide, a lens, or the like is used as the light collecting unit. In order to transmit the optical signal obtained by the light collecting unit to the photoelectric conversion unit, an optical fiber, a light pipe made of transparent glass or acrylic, or the like is used, and an optical fiber is preferably used.

The electric signal converted by the photoelectric conversion unit is measured by the electric measurement unit. The electric measurement unit is, for example, a signal amplifying unit that amplifies the power value of an electric signal output from the photoelectric converter, a signal processing unit that calculates and quantifies the power value of the electric signal, and relates to the quantified tritium concentration. It can be configured to be processed to display an electric signal or to include an output control unit for controlling an electric output. Specifically, it includes an amplifier, an analog / digital converter, a scaler, a discriminator, a simultaneous measurement circuit, and the like.

FIG. 1 shows a basic configuration of a tritium concentration measuring apparatus according to the present invention. The tritium-sensitive detection end 1 is made of a constituent material such as a fluorescent plastic optical fiber that emits light in response to beta rays emitted from tritium or a plate-like plastic scintillator of about 1 mm or a rod-like plastic scintillator having an outer diameter of several millimeters. Light generated in the constituent material of the tritium-sensitive detection end in response to tritium existing in the measurement environment is collected by the light collection unit 2. The light collected by the light collecting component is introduced into the photoelectric converter 4 via the optical transmission optical fiber 3.
If there is no restriction on the arrangement of the measurement environment, the optical transmission optical fiber 3 can be omitted. The light introduced into the photoelectric converter 4 is converted here into an electric signal. The electric measurement system 5 is a system that outputs an electric signal output from the photoelectric converter 4 to the recorder 6 as data of a measured value of tritium concentration.

The electric measurement system 5 shown in FIG.
FIG. 2 shows an example of the configuration. Electric measurement system 5
A signal amplifying unit 5a for amplifying the power value of the output electric signal from the photoelectric converter 4 to a power value sufficient to perform a numerical process, a signal processing unit 5b for calculating the power value of the electric signal and converting it to a numerical value, It comprises an output control unit 5c for processing to display the electric signal relating to the tritium concentration quantified by the unit 5b and controlling the electric output to the recorder 6.

FIG. 3 shows an application example of the tritium concentration measuring apparatus of the present invention. This is a basic configuration in which a condensing unit 2 and an optical transmission optical fiber 3 are provided at both ends of a tritium sensitive detection end 1 so that light generated in response to tritium at the tritium sensitive detection end 1 can be efficiently measured. That is, this is a tritium concentration measuring device with improved light-collecting efficiency that can obtain tritium concentration information from both ends of the tritium sensitive detection end 1. In principle, light can be collected twice as much as in the first embodiment, and efficiency can be improved. The electric measurement system 5 measures the added value of the photoelectric converter 4.

FIG. 4 shows another application example of the tritium concentration measuring apparatus of the present invention. Tritium concentration measurement capable of simultaneously measuring tritium concentrations at a plurality of detection points, including a plurality of sets of detection units each including a tritium-sensitive detection end 1, a light collecting unit 2, an optical transmission optical fiber 3, and a photoelectric converter 4. Device. The electric measurement system 5 has a function of a basic configuration that independently processes each of a plurality of series.

[0014]

According to the present invention, continuous measurement in real time is possible in the required concentration range of the tritium concentration in the liquid. Further, in an aspect in which tritium concentration information can be obtained from both ends of the tritium sensitive detection end,
The detection efficiency and the light collection efficiency can be improved, and in an aspect having a plurality of detection unit sets, the tritium concentration at a plurality of detection locations can be measured simultaneously.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a tritium concentration measuring device of the present invention.

FIG. 2 shows an example of the configuration of the electric measurement system 5 shown in FIG.

FIG. 3 is an application example of the tritium concentration measuring device of the present invention.

FIG. 4 is an application example of the basic configuration of the tritium concentration measuring device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tritium sensitive detection end 2 Condenser 3 Optical transmission optical fiber 4 Photoelectric converter 5 Electric measurement system 5a Signal amplifier 5b Signal processor 5c Output controller 6 Recorder

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Daiyasu Naito 1-1-1 Wadazakicho, Hyogo-ku, Hyogo-ku, Kobe-shi, Hyogo Mitsubishi Heavy Industries, Ltd.Kobe Shipyard (72) Inventor Shigeru Ohira Nakamachi, Naka-gun, Ibaraki Prefecture No. 801, Mukoyama, in the Naka Research Laboratory of the Japan Atomic Energy Research Institute (72) Inventor Takumi Suzuki 2-4, Shirane, Hakukata, Tokai-mura, Naka-gun, Ibaraki Prefecture Within the Tokai Research Laboratory of the Japan Atomic Energy Research Institute (72) Inventor Masataka Nishi Ibaraki 2-4, Shirane, Shirakata, Tokai-mura, Naka-gun Inside the Tokai Research Laboratory, Japan Atomic Energy Research Institute (72) Katsumi Urayama 622, Funashiishikawa, Tokai-mura, Naka-gun, Ibaraki Prefecture F-term (in reference) 2G088 AA03 EE13 EE26 FF05 GG11 GG14 KK15

Claims (4)

[Claims] 1. A tritium comprising: a tritium-sensitive detecting end for continuously detecting a beta ray of tritium; a photoelectric conversion unit for converting an optical signal into an electric signal; and an electric measuring unit for measuring the electric signal. Concentration measuring device. 2. The tritium concentration measuring device according to claim 1, wherein the detection end is a plastic scintillator or a fluorescent fiber. 3. A light condensing part for condensing light generated in response to tritium at the detection end for light transmission to the photoelectric conversion part, and a light from the light condensing part to the photoelectric conversion part. The tritium concentration measuring device according to claim 1 or 2, further comprising an optical transmission optical fiber used for transmission. 4. A method for measuring tritium using the apparatus for measuring tritium concentration according to claim 1.