JPS6045832B2 - Radioactive material monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for monitoring radioactive substances, such as radioactive iodine, in fluids.

A conventional device of this type is shown in FIG. In the figure, 1 is a cartridge supply unit, 2 is an activated carbon cartridge that adsorbs radioactivity, 3 is a cartridge moving device, 4 is a sampling unit to which fluid containing radioactive substances is supplied, 5 is a lead shield surrounding the detector 6, Reference numeral 7 denotes a cartridge disposal section, and a conventional example of recycling and reusing cartridges is shown in FIG. In the figure, reference numeral 3 denotes a cartridge moving device that circulates the cartridges in an endless manner without changing the order of the cartridges, and the other components are the same as in FIG. 1. Next, the operation will be explained.

In FIG. 1, an unused activated carbon cartridge 2 stored in a cartridge supply section 1 is sent to a sampling section 4 by a cartridge moving device 3, such as a rotating disk or a belt conveyor.

In the sampling section, radioactive iodine in the sample gas is collected in an activated carbon cartridge, and after collection for a certain period of time, the cartridge is sent to the detection section by a cartridge moving device, and Na
Ti) Detect gamma rays emitted from radioactive iodine by a detector 6, such as a scintillation detector. Here, the solid part of the detector 6 is surrounded by a lead shield 5 to remove background radiation and increase detection sensitivity. Further, the used cartridges 2 are stored in a cartridge disposal section 7. Alternatively, in the example shown in Figure 2, the radioactive iodine is placed on an endless moving device such as a rotating disk, and after measuring the radioactive concentration, the radioactivity of the radioactive iodine is sufficient for the period until the rotating disk rotates and returns to its original position. The cartridge is reused by making it longer than the decay time (which is sufficiently longer than the half-life of 8.05 days in I), and returning the cartridge to the sampling section by the rotation of the rotating disk. The conventional device is constructed as follows.

Therefore, in the example shown in Figure 1, if the cartridge is to be reused, it is necessary to replace and install the cartridge, and in the example shown in Figure 2, there is no need to replace the cartridge, but generally cartridges are replaced quite frequently, so If the required number of cartridges cannot be placed on the rotating disk, when the rotating disk rotates once and the cartridge that has collected high concentration radioactive iodine returns to the detection unit, the radioactivity level will be sufficient. Not attenuated, high background, detection sensitivity at initial state (unused cartridge)
significantly worse than. Furthermore, in any of the examples, when the cartridge is reused for a long period of time, there is a problem in that the cartridge absorbs moisture and the collection efficiency decreases. This invention was made to eliminate the above-mentioned conventional drawbacks. By adding a comparator to the radiation measurement circuit and providing a cartridge exchange device, cartridges with a high accumulated radioactivity level can be removed and unused cartridges can be replaced. The purpose is to provide an automatic sampling device that can be exchanged with

In addition, a heating section is provided to maintain the collection performance of the cartridge. An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, 1 is a cartridge supply section, 2 is an activated carbon cartridge, 3 is a cartridge moving device, 4 is a sampling section, 5 is a lead shield surrounding the detector 6, 8 is a preamplifier, 9 is a measurement section, and 10 is a comparator. , 11 is a cartridge exchange device, and 12 is a heating section. Activated carbon cartridges 5 are arranged at appropriate intervals in an endless cartridge moving device 3. The sampling section 4 includes an activated carbon cartridge 2
It has a cylindrical structure that moves, for example, in the vertical direction each time the activated carbon cartridge 2 reaches that position, and when the activated carbon cartridge 2 comes to the center of the sampling section, the cylinder that had been moving upward moves downward to surround the cartridge 2. Keep it airtight. Here, the cartridge is vented and radioactive iodine in the sampling gas is collected in the activated carbon cartridge 2. After a certain collection time, the cylinder moves upward again, and the cartridge moving device 3 moves the cartridge 2 to the position of the detector 6, where the collected radioactivity is detected. The detected signal is amplified by a preamplifier 8, and a measuring section 9 processes and counts the signal. As a result, if the counting rate is higher than the configured value (
In other words, when a high concentration of radioactive iodine is accumulated in the cartridge to be measured), the cartridge exchange device 11 is driven by the output of the comparator 10. An example of the configuration of the cartridge exchange device 11 will now be described with reference to FIGS. 4 and 5.

In the figure, 1 is a cartridge supply section, 2 is an activated carbon cartridge, 3 is a cartridge moving device, 7 is a cartridge disposal section, 13 is a cartridge push rod, and 14 is a claw. If the radioactivity level of the activated carbon cartridge that has passed through the detection section is lower than the set value, the cartridge is circulated by the cartridge moving device and returns to the sampling section again after a period of time longer than the half-life.

If the radioactivity level exceeds the set value, the cartridge exchange device is activated to move the push rod 13 and push the cartridge 12 to the waste section 7. FIG. 5 shows this operation in plan view. When the push rod 13 returns to its original position, the claw 14 opens and a new cartridge is loaded into the cartridge moving device 3 from the supply section. After attachment, the claw 14 returns to its original position, and the next cartridge is held in the cartridge supply section. The cartridge is then moved to the heating section, where the heating section 12 dehumidifies the heating section, thereby preventing a decrease in the adsorption efficiency of radioactive substances.

As described above, according to the present invention, a cartridge contaminated with high concentration of radioactive iodine is removed based on the judgment of the detected signal level, and a new cartridge is supplied. Since a cartridge with a sufficiently low background level is supplied to the sampling section, a decrease in detection sensitivity is avoided.
Desired measurement accuracy can be maintained.

Furthermore, by heating and dehumidifying, the collection efficiency is restored, so the cartridge can be reused while maintaining the same performance over a long period of time, saving the effort of replacing it and reducing the amount of waste. BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are block diagrams showing an example of a conventional radioactive substance automatic monitoring device, FIG. 3 is a block diagram showing an example of a radioactive substance monitoring device according to the present invention, and FIG. 4 is a block diagram showing an example of a conventional radioactive substance monitoring device. 5 is a configuration diagram showing an example of a cartridge exchange device, and FIG. 5 is an explanatory diagram of the operation of FIG. 4.

In the figure, 2 is a cartridge, 3 is a cartridge moving device, 4 is a sampling section, 6 is a radiation detector, 10 is a comparator, 11 is a cartridge exchange device, and 12 is a heating device.

Claims (1)

[Scope of Claims] 1. A cartridge filled with an adsorbent that adsorbs radioactive substances, a cartridge moving device in which a plurality of these cartridges are arranged and moved along an endless track, and the above-mentioned A sampling section that allows fluid containing radioactive substances to pass through the cartridge, a radiation detector that detects radiation in the cartridge that has passed through this sampling section, and when the detection value of this radiation detector is equal to or higher than a set value, the cartridge is removed from the moving device. A radioactive substance monitoring device equipped with a cartridge exchange device that separates the cartridge and supplies a new cartridge. 2. A cartridge filled with an adsorbent that adsorbs radioactive substances, a cartridge moving device in which a plurality of these cartridges are arranged and moved along an endless trajectory, and a cartridge that is installed in the moving path of this cartridge moving device and contains radioactive substances. a sampling section through which the fluid passes; a radiation detector that detects radiation in the cartridge that has passed through the sampling section; and when the detection value of the radiation detector is equal to or higher than a set value, the cartridge is removed from the moving device and a new cartridge is installed. A radioactive substance monitoring device comprising: a cartridge exchange device for supplying a cartridge; and a heating device for heating a cartridge on the cartridge moving device.