JPS588752B2 - Radiation measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation measuring device that detects radiation in a liquid with high sensitivity.

FIG. 1 is a cross-sectional view showing the configuration of a conventional radiation measuring device in a liquid, in which 1 is a radiation shield, 2 is a container for holding a sample liquid,
3 is a plastic scintillator detector for detecting radiation, 4 is a light guide bonded to the plastic scintillator detector 3, 5 is a photomultiplier tube, 6 is a signal cable, and 7 is a sampling pipe through which a sample liquid passes.

In this measuring device, a sample liquid introduced through a sampling pipe 7 is temporarily retained in a container 2 covered with a radiation shield 1 .

Radiation from the radioactive substance contained in the sample liquid enters the plastic scintillator detector 3 and is converted into light within the plastic scintillator detector 3.

This light pulse is transmitted to a photomultiplier tube 5 by a light guide 4.
is converted into a current pulse signal and transmitted to the measurement processing circuit via the signal cable 6.

Due to radiation quality, most radiation detection devices in sample liquids measure gamma ray nuclides (eg, 60Co, 137Cs, etc.).

However, in some cases, it may be necessary to detect β-rays or weak-energy γ-ray nuclides in liquids such as tritium.

In this case, since the range of the target radiation in the sample liquid is extremely short, measurement is difficult with a measurement container of a normal shape, so the height of the container 2 is made as low as possible to make the liquid layer thinner.
In addition, the plastic scintillator detector 3 has a large diameter to improve detection sensitivity.

However, in the conventional method as described above, since the plastic scintillator detector 3 is made to have a large diameter, the accompanying light guide 4 and photomultiplier tube 5 become large, and the radiation shield 1 that covers them also becomes large. Therefore, it has the disadvantage of increasing weight.

In addition, there is a structural upper limit to making the liquid layer thinner, and if it is extremely thin, there will be a large pressure drop when the sample liquid flows in and out, and if a highly concentrated sample liquid stagnates, there will be disadvantages such as contamination of the detector and container. Therefore, it was not possible to obtain sufficiently high sensitivity.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by providing a large number of pores in a plastic scintillator detector and passing a sample liquid sprayed in a shower form through these pores. This is a compact and highly sensitive device that can measure radiation in liquids.

This invention will be explained below.

FIGS. 2 and 3 show an embodiment of the present invention, with FIG. 2 being a cross-sectional view of the overall structure, and FIG. 3 being an exploded perspective view of the main parts of FIG.

In these figures, 11 is a radiation shield, 12 is a photomultiplier tube, 13 is a signal cable, 14 is a sampling pipe, 15 is a plastic scintillator detector, and 16 is a fountain head that sprays the introduced sample liquid in a shower shape. ,1
7 is a plurality of fountain holes provided in the fountain head 16, 18 is a liquid column, and 19 is the plastic scintillator detector 15.
The number of pores 20 is the same as the number of the water fountain holes 17, and 20 is a water receiving container.

Next, this operation will be explained with reference to FIGS. 4a and 4b.

As shown in FIG. 4a, in the conventional example, the radiation Ra and Rb emitted from the radioactive substance n in the sample liquid in the container 2 are attenuated in the sample liquid and cannot be detected with high sensitivity. In the invention, as shown in FIGS. 2 and 3, the sample liquid introduced through the sampling pipe 14 flows into a shower-like thin liquid column 18 from a plurality of fountain ports 17 provided in the fountain head 16.
It is squirted out.

On the other hand, a plastic scintillator detector 15 placed directly below this fountain head 16 has a fine hole 19 in the same bush as the fountain mouth 17, and as shown in FIG. The liquid becomes a liquid column 18 and falls.

In this case, the pores 19 are configured to have a diameter equal to or slightly larger than the diameter of the liquid column 18, and a structure is adopted in which the plastic scintillator detector 15 does not come into direct contact with the liquid column 18 if contamination is a problem.

Liquid 1 passing through plastic scintillator detector 15
Radiation Ra and Rb from the plastic scintillator detector 1 surrounding the liquid column 18 as shown in FIG.
5 and causes it to emit light.

Then, as shown in FIG. 3, the photomultiplier tube 12 attached to the side of the plastic scintillator detector 15 receives this emission pulse and converts it into a current pulse signal, which is then transmitted to the measurement processing circuit via the signal cable 13. be done.

In the above embodiment, only one photomultiplier tube 12 is used, but a plurality of photomultiplier tubes may be provided in order to further compensate and improve detection sensitivity.

As explained above, in the present invention, the sample liquid can be made into a sufficiently thin liquid column, so that the radiation from the sample liquid enters the plastic scintillator detector without being significantly attenuated within the liquid.

Furthermore, since the plastic scintillator detector surrounds the liquid column, radiation emitted in all directions except the axial direction of the liquid column can be captured, and the detection efficiency is improved compared to the conventional method.

Therefore, it is possible to downsize the device to obtain the same sensitivity as the conventional type.

It is particularly effective in detecting short-range radiation such as β-rays in liquids.

In addition, if necessary, the pores of the plastic scintillator detector can be made larger than the diameter of the liquid column, so the sample liquid does not come into direct contact with the plastic scintillator detector.
It has many advantages, such as being able to prevent long-term contamination of the plastic scintillator detector, providing stable detection sensitivity, and being lightweight and compact.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the configuration of a conventional radiation measurement device, FIG. 2 is a sectional view of the entire radiation measurement device showing an embodiment of the present invention, and FIG. 3 is an exploded perspective view of the main parts of FIG. Figure 4a
, b are a partial front view and a partial cross-sectional perspective view for explaining the operation of the conventional example and the present invention in comparison. In the figure, 11 is a radiation shield, 12 is a photomultiplier tube, and 13
is a signal cable, 14 is a sampling pipe, 15 is a plastic scintillator detector, 16 is a fountain head, 17
is a water fountain, 18 is a liquid column, 19 is a pore, and 20 is a water receiving container. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A radiation shield that shields radiation, a fountain head equipped with a plurality of water fountains that introduce a liquid to be measured into the interior covered by the radiation shield and eject the liquid to be measured as a liquid column, and What is claimed is: 1. A radiation measuring device comprising: a plastic scintillator detector having a plurality of pores through which liquid columns pass through and detecting radiation; and a water receiving container receiving the liquid.