JPS61160079A - Apparatus for analysis of beta nuclide - Google Patents

Abstract

PURPOSE:To enable the discrimination of a beta nuclide with high sensitivity by simple constitution, by laminating scintillators different in a fluorescence attenuation constant in a coaxial cylindrical form to provide the same in a hollow container and providing the inflow and outflow parts of a liquid specimen to said container. CONSTITUTION:Scintillators 21, 22, 23 different in a fluorescent attenuation constant gamma are successively laminated to a photomultiplier tube 1 in a coaxial cylindrical form and the scintillators 21, 22 are provided in a hollow cylindrical container and the inflow and outflow ports of a liquid specimen are provided to said container. That is, coaxial cylindrical laminated scintillators 13 are optically connected to the upper and lower photomultipliers 1 and the liquid specimen flowed in from specimen inlet piping 5 is passed around the coaxial cylindrical laminated scintillators 13 to be flowed out from a specimen outlet 4. By using this flow cell type detector, the enhancement of efficiency three times a conventional one is expected and a beta nuclide can be discriminated with high sensitivity by simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to the analysis of beta-ray emitting nuclides, and particularly to a radioactivity analyzer suitable for cases where the type of isotope contained is known.

[Background of the invention]

89 of beta-ray emitting nuclides (hereinafter referred to as beta nuclides)
The analysis method for 3r and 903r is detailed in "Radioactive Strontium Analysis Method", Science and Technology Agency (1963). In this work, a method for isotopic nuclide analysis based on chemical separation of 3r isotopes has been clarified. Similarly, [Nuclear Safety Commission Safety Examination Guidelines Collection JP] supervised by the Science and Technology Agency and the Nuclear Safety Bureau
180 also describes a method for analyzing Sr isotopes. 8113r and 9 were obtained from the chemically separated fraction of 3r.
There are the following three methods for quantitatively analyzing 03r. .

(i) 90 Br and 119 from the radioactivity immediately after pure separation of sr and the radioactivity (milking) in a state where the radioactivity of 903 r 90y has been reached after leaving it for more than 2 weeks.
Quantify the radioactivity of Sr.

(2) Measure at two different times during the 90Y generation process (the process of reaching radiative equilibrium) of the pure separated 3r fraction, and quantify 3r and Sr from the Y generation process.

(3) By beta-ray spectrometry 903
Directly separate and measure r and 893 to find their respective amounts.

The above is an overview of the reference literature, and the current Br analysis of nuclear power plants also uses one of these methods. the above(
13, method (2) is all based on the radiation equilibrium of 903r and 90y, and the time required for analysis is 1 to 2 weeks. In method (3), the beta ray spectrum is analyzed by computer, which increases the size and cost of the analysis system.

[Purpose of the invention]

An object of the present invention is to provide a beta-nuclide analyzer that is easy to automate and capable of highly sensitive measurement in isotope analysis of beta-nuclides.

[Summary of the invention]

In order to achieve higher sensitivity measurement, the present invention employs a structure in which the above-described flat plate laminated scintillator is provided in the form of a laminated cylinder or a laminated sphere, and is immersed in the measurement sample water. This structure can greatly improve the geometrical efficiency of measurements compared to a flat plate laminated scintillator. Furthermore, an inlet and an outlet for the measurement sample are provided.
The flow cell structure makes the detector easy to automate.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. In the configuration of the present invention, a hollow cylindrical container 3 in which a cylindrical laminated scintillator 2 is mounted is provided between two photomultiplier tubes 1 facing each other. At the bottom of the hollow cylindrical container 3, an inlet/outlet 4.degree. 5 is provided through which the sample to be measured flows in and out. A flow cell and a photomultiplier tube consisting of a cylindrical laminated scintillator 2 and a hollow cylindrical container 3 are housed in a lead jacket 6 to block the incidence of external radiation. The output signals of the two photomultiplier tubes 1 are sent to an amplifier 7, a waveform discrimination circuit 8, and a single channel analyzer 9.10.11. The data is input to the data processing device 12 via the data processor 12, and nuclide analysis of beta rays is carried out. The operation of the present invention will be explained in detail below.

and <K, here, Br analysis will be explained as beta nuclear motion analysis. In Br analysis, the Br fraction is extracted using chemical separation operations such as liquid chromatography.
89Sr, 90B contained in the Some fraction
, it is necessary to analyze IOy.

89B r, 903 r are the nuclides to be analyzed, 9
0y is the daughter nuclide of 903. The nuclear data for each are shown in Table 1.

FIG. 2 shows an explanatory diagram of the beta nuclide discrimination principle of the present invention. Scintillators 21, 22, and 2.3 having different fluorescence attenuation constants τ are laminated in order on the photomultiplier tube 1. When each scintillator 21, 22, 23 is independent, the output waveform shown in FIG. 3 is obtained from the output of the amplifier 7. Since the fluorescence attenuation constant τ of each scintillator is different, the rise time of the output waveform is different.

In the case of the laminated scintillator shown in FIG. 2, the output waveform is shown in FIG. 4. That is, the laminated scintillator 21 shown in FIG. 2 has a flight thickness of the maximum energy Ba of beta rays, and the scintillator 22 has a thickness so that the sum of the thicknesses of the scintillators 21 and 22 is the range thickness for analysis. (Scintillator 23 is EC
(The design should be designed to have a range thickness greater than or equal to Table 2 shows specific design examples of laminated scintillators targeted for Br analysis.

A detector designed in this way produces an output waveform with a rise time of τa, an output waveform synthesized by τa and τb, τa, τb, corresponding to the beta ray energy to be analyzed.
, τC, a synthesized output waveform is obtained (FIG. 4). By distinguishing this rise time, we can discern the energy of beta rays. This measurement system blower wire is shown in FIG. A waveform discrimination circuit 8 discriminates the rising 9 hours of the output waveform. The output of the waveform discrimination circuit 8 is a pulse with different peak values, which are identified by simple channels 9, 10, 11, and the beta nuclide is quantified from the count number of each peak value obtained by the data processing device 12.

The present invention applies the principle of beta nuclide discrimination described above, and uses a laminated scintillator manufactured in a coaxial cylindrical shape. 1. The structure 13 of a coaxial cylindrical laminated scintillator is shown in FIG. The scintillator 23 in Fig. 2 is the part that targets the long range of the scintillator 14.
corresponds to Similarly, scintillator 15 in FIG. 1 is similar to scintillator 22 in FIG. 2, scintillator 1G in FIG.
corresponds to the scintillator 21 in FIG. This coaxial cylindrical laminated scintillator 13 has upper and lower photomultiplier tubes 1
optically connect to. A liquid sample flowing in from the sample inlet pipe 5 passes around a coaxial cylindrical laminated scintillator 13 and flows out from the sample outlet 4. If this flow cell type detector is used, an efficiency improvement of more than three times can be expected compared to the somewhat higher efficiency shown in FIG. In other words, highly sensitive measurement of 3 times or more becomes possible.

FIG. 5 shows a modification using a spherical laminated scintillator 20. A spherical laminated scintillator 20 is filled in a space surrounded by a photomultiplier tube 1 and a hollow cylindrical container 3 as in FIG. The sample water flows in through the sample inlet pipe 5 and flows out through the sample outlet 4. In this modification, the degree of adhesion between the sample water and the scintillator is greater than the structure shown in FIG. 19, and a much higher sensitivity can be achieved.

Since both of FIG. 1 and FIG. 5 are flow cell type detectors, it is possible to easily and directly measure the eluate from which Sr has been separated by liquid chromatography. This is because the eluate can be transferred simply by switching the valve in the piping flow path.
Automation of measurements can be easily achieved.

Table 1 [Effects of the invention] According to the present invention, highly sensitive beta nuclide discrimination is possible with a simple configuration using only a commercially available radiation measurement module, and an automatic method that improves sensitivity by about three times compared to conventional methods We can provide analysis equipment.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of an embodiment of the present invention, Figure 2 is an explanatory diagram of the first principle of beta nuclide discrimination, Figure 3 is an output waveform diagram when each scintillator is used alone, and Figure 4 is the output of the laminated scintillator. The waveform diagram in FIG. 5 is a configuration diagram showing a modification of the present invention. DESCRIPTION OF SYMBOLS 1... Photomultiplier tube, 2... Cylindrical laminated scintillator 3... Hollow cylindrical container, 5... Sample inlet piping, 6...
...Lead jacket body, 7...Amplifier, 8...Waveform discrimination circuit, 12...Data processing device.

Claims (1)

[Claims] 1. In a beta-ray emitting nuclide analyzer that discriminates output waveforms obtained from scintillators with different fluorescence attenuation constants and radiation absorption thicknesses, scintillators with different fluorescence attenuation constants are stacked in a coaxial cylindrical shape, and the scintillators are A beta nuclide analyzer characterized by being installed in a hollow container and provided with inflow and outflow ports for a liquid sample.