JPS62228186A - Apparatus for measuring purity of nuclide - Google Patents

Abstract

PURPOSE:To enable measurement in a real time, by mounting a radiation detector detecting only gamma-rays and a radiation detector also detecting beta-rays other than gamma-rays as the detectors to a specimen containing a radio isotope. CONSTITUTION:A radiation detector 2 detecting only gamma-rays and a radiation detector 3 also detection beta-rays other than gamma-rays are provided to a case 11. The radiation detector 2 detecting only gamma-rays can be realized by using a radiation detector also detecting beta-rays other than gamma-rays and providing a lead plate, for example, having a thickness of about 1mm to the incident surface thereof. The output R2 of the radiation detector 2 and the output R1 of the radiation detector 3 are converted to a digital signal by an A/D converter 4 to be taken in an operation part 5. The operation part 5 calculates the purity of a nuclide according to the output from the A/D converter 4 and that from a function part 7 to display the same on a display device 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an apparatus for analyzing radioisotope-labeled gas (hereinafter referred to as RI gas) mainly used in nuclear medicine and measuring its nuclide purity.

The nuclide purity is the purity of the nuclide of RI, 1For example, II
It refers to the proportion of 11C when the C gas contains impurities such as 13N and ISr○.

(Prior art) In the purity analysis of RI gas, the purity of nuclides that emit gamma rays of the same energy is measured by sampling an appropriate amount of RI gas, measuring the attenuation curve with a Curie meter, etc., and determining the half-life. Ta.

(Problems that Jl! Ming is trying to solve) The method of measuring nuclide purity by half-life takes time. Furthermore, if the operation is to be automated, the device will be large-scale.

The purpose of the present invention is to eliminate these drawbacks of the prior art and to realize a device that is suitable for online use, does not take much time to measure, and can measure nuclide purity using a relatively simple device. be.

(Means for Solving the Problems) To explain with reference to FIG. 1 showing an embodiment: 1. The nuclide purity measuring device of the present invention detects only γ-rays as a detector for samples containing radioisotopes. Radiation detector (2
) and a radiation detector (3) that detects β rays in addition to γ rays, and the signal processing unit has a radiation detection intensity (R:) when detecting only γ rays, relative to the nuclide purity of the sample. , a function section (7) that provides a ratio relationship with the radiation detection intensity (R+) when detecting β rays in addition to γ rays, and a detection signal (2) of the radiation detector (2) that detects only γ rays. R2) and the detection signal (R1) of the radiation detector (3) that detects β-rays in addition to γ-rays
) and calculates the nuclide purity from the ratio of both detection signals and the output of the function section (7).

(Operation) During β decay or β1 decay, β rays or β1 rays (hereinafter, β rays and β+ rays are collectively referred to as β rays) having different energies depending on the nuclide are emitted. The energy of β-rays has a continuous distribution, and the energy distribution of β-rays differs depending on the nuclide. The output of the radiation detector (3), which detects β rays in addition to γ rays, depends on the energy of the β rays, so the radiation detector (2), which detects only γ rays for one nuclide, and the γ ray The signal ratio with the radiation detector (3) which also detects β rays is a constant value. This value changes depending on the nuclide, so
By evaluating the deviation from a constant value based on the ratio of both signals, purity can be calculated if the contaminating nuclide is known.

Suppose there are two types of radioactive isotopes, A and B, and the sensitivities of the radiation detector (2) that detects only gamma rays are CI and C2, respectively, and the sensitivity of the radiation detector (2) that detects only gamma rays is CI and C2, respectively. Let the sensitivities of the detector (3) be C3 and C4, respectively. These four constants shall be measured in advance using a pure radiation source. For a mixture of A and B, where the purity of A is t, the measured value of radiation detection intensity (R2) when detecting only γ rays and the radiation detection intensity when detecting β rays in addition to γ rays. The ratio of (R1) to the measured value (R+/R
When we write ri) as M.

M= (tcs+ (1-t) C4) / (tC+
+ (1-t) C:)= ((C3-C4) t+
Ca) / ((CI - C2) t+C:).

Solving this for t.

t=f(M) = (C4-MC2)/(M (CI-C2)-CG
+Ca), and once M is found, the purity t of A can be found using this formula.

(Example) FIG. 1 represents one embodiment.

R1 gas flows through a case 11 connected to a pipe 10. The case 11 is provided with a radiation detector 2 that detects only gamma rays and a radiation detector 3 that detects not only gamma rays but also beta rays. The radiation detector 2 that detects only γ-rays uses the same radiation detector 3 that detects β-rays in addition to γ-rays, and a lead plate with a thickness of about 1 mm, for example, is provided on its entrance surface. This can be achieved by

Output R2 of radiation detector 2 and output R of radiation detector 3
1 is converted into a digital signal by the A/D converter 4 and taken into the arithmetic unit 5. 7 is the function part, and the above M
Relationship between (=Rr/R=) and nuclide purity t=f(M) =(C4-MC2)/(M((,+-Cri)
C3+C4) is memorized. In the calculation section 5, the nuclide purity is calculated according to the output from the A'/D converter 4 and the output from the function section 7, and is displayed on the display device 6.

The relationship f (M) between the nuclide purity t and the ratio M may be obtained by actual measurement and set in the function unit 7, or may be calculated by the function unit 7 from the nuclide contained in the RI gas.

As shown in FIG. 2, the calculation unit 5 calculates the ratio M (=R
+/R2), and based on the ratio, the nuclide purity f (M) is input from the function section 7 and output to the display device 6.

The calculation section 5 and the function section 7 can be configured separately,
Alternatively, the calculation section 5 and the function section 7 can be realized by a microcomputer.

FIG. 3 shows another embodiment.

In this embodiment, a radiation detector 2 that detects only gamma rays is sandwiched between a pipe 20 with a thin wall through which RI gas flows, and a radiation detector 2 that detects only gamma rays and a
A radiation detector 3 that also detects radiation is provided.

FIG. 4 shows yet another embodiment.

In the embodiment shown in FIG. 1, the radiation detector 2 detects only gamma rays.
Two types of radiation detectors are used: a radiation detector 3 that detects β rays in addition to γ rays, and in this embodiment, a β ray filter 24 is arranged on the incident surface of the radiation detector 22, and the The mechanism allows the β-ray filter 24 to be moved between the position of the incident plane of the radiation detector 22 and a position outside the incident plane. For example, the β-ray filter 24 has a thickness of 1
A lead plate of about mm can be used.

In this embodiment, the radiation detector 22 functions as two types of radiation detectors: a radiation detector that detects only gamma rays, and a radiation detector that detects beta rays in addition to gamma rays.

(Effects of the Invention) The nuclide purity measuring device of the present invention is provided with a radiation detector that detects only γ-rays and a radiation detector that detects β-rays in addition to γ-rays, and the output of both radiation detectors is The nuclide purity of a sample containing radioactive isotopes is calculated from the ratio. Therefore, real-time measurement is possible, and a relatively simple nuclide purity measuring device can be realized.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of the present invention, FIG. 2 is a flow chart showing the operation of the same embodiment, and FIGS. 3 and 4 are schematic diagrams showing other embodiments. 2... Radiation detector that detects only gamma rays, 3.
...Radiation detector that detects β rays in addition to γ rays. 5... Arithmetic section, 7... Function section.

Claims (1)

[Claims] (1) As a detector for samples containing radioactive isotopes, it is equipped with a radiation detector that detects only gamma rays and a radiation detector that detects beta rays in addition to gamma rays. , a function part that gives the ratio relationship between the radiation detection intensity when detecting only γ-rays and the radiation detection intensity when detecting β-rays in addition to γ-rays, and the radiation detection intensity that detects only γ-rays. A calculation unit that receives a detection signal from a detector and a detection signal from a radiation detector that detects β rays in addition to γ rays, and calculates nuclide purity from the ratio of both detection signals and the output of the function unit. A nuclide purity measuring device characterized by: