JPH0735637A - Raioactivity measuring device - Google Patents

Abstract

PURPOSE:To prevent mixing with gas from the outside of an inspection vessel and measure only FP gas from a glass-solidified body set in the inspection vessel. CONSTITUTION:Constitution is performed in that introduction tubing 28 for setting an object to be detected 25 in a radioactivity shield vessel 20 and introducing clean gas to a detection vessel 21 wherein the object to be detected 25 is set, a pressurization pump 29 for sending the clean gas to a detection vessel 22 provided on the introduction tubing 28, taking-out tubing 31 for taking out the gas in the detection vessel 22 and detection means 26, 27 for detecting radioactivity density of the gas taken out from the detection vessel 21 through the taken-out tubing 31 are equipped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radioactivity measuring device for monitoring a leak of a gas containing fission products (hereinafter referred to as FP gas) from a vitrified body obtained by solidifying radioactive waste with glass. Regarding

[0002]

2. Description of the Related Art In a spent fuel reprocessing plant,
The radioactive waste after reprocessing is processed and stored in a vitrified state. From the viewpoint of ensuring safety, it is necessary to confirm that the FP gas does not leak from the vitrified body.

Therefore, conventionally, the presence or absence of leakage of FP gas from the vitrified body has been measured using a radioactivity measuring device as shown in FIG. In such a radioactivity measuring device, an inspection container 2 is installed inside a radioactivity shielding container called a cell 1, and the vitrified body 3 is put in the inspection container 2. A lid 4 is attached to the opening of the inspection container 2 so that the inspection container 2 can be hermetically sealed. A pipe 5 and a pipe 6 are connected to the inspection container 2, a clean gas is introduced from the outside of the cell into the inspection container 2 by the pipe 5, and the gas in the inspection container 2 is measured by the pipe 6.
Will lead to. A suction pump 8 is attached to the pipe 6, and a radiation detector 9 is attached to the inside of the measurement container 6.

In the above structure, the suction pump 8 sucks the negative pressure of the gas in the inspection container 2 to obtain the inspection container 2
The gas inside is sampled for a certain period of time, and the FP gas is introduced into the measurement container 6 using the clean gas as a carrier. If the gas introduced into the measurement container 6 contains FP gas, the FP gas is detected by the radiation detector 9 and sent to the measuring device 10 installed outside the cell.

By the way, in many cases, a vitrified body 11 before inspection is temporarily placed inside the cell 1. If the FP gas leaks from the temporarily set vitrified body 11, the leak gas may be mixed into the inspection container 2. Considering the workability in the cell 1, it is impossible to use fasteners (bolts, packings, etc.) that can be firmly tightened to fix the lid 4 attached to the inspection container 2. Therefore, when the gas in the inspection container 2 is sucked, a phenomenon occurs in which the air in the cell 1 is sucked into the inside from the gap between the lid 4 and the inspection container 2.

[0006]

As described above, the conventional radioactivity measuring apparatus for detecting the leak of the FP gas from the vitrified body sucks the gas in the inspection container under a negative pressure, so that the object to be inspected is to be inspected. There was a possibility that the FP gas leaking into the cell from the vitrified materials other than the above would flow into the inspection container.

The present invention has been made in view of the above circumstances, and it is possible to prevent the FP gas leaking from the vitrified body other than the inspection object into the cell from flowing into the inspection container, FP from vitrified material installed in the container
It is an object of the present invention to provide a radioactivity measuring device capable of accurately measuring only gas.

[0008]

In order to achieve the above-mentioned object, the invention according to claim 1 cleans a radioactivity measuring device into an inspection container which is installed in a radioactivity shielding container and in which a subject is placed. An introduction pipe for introducing gas, a pressure pump provided in the introduction pipe for feeding the clean gas to the inspection container, an extraction pipe for taking out the gas in the inspection container to the outside of the container, and A detection means for detecting the radioactivity concentration of the gas taken out from the inspection container through the take-out pipe is provided.

According to a second aspect of the present invention, in the above structure, the radioactivity measuring device is detected by auxiliary detection means for detecting the radioactivity concentration in the radioactivity shielding container, and the auxiliary detection means. Pressure control means for controlling the pump pressure of the pressurizing pump according to the radioactivity concentration in the radioactivity shielding container is provided.

According to a third aspect of the present invention, in any one of the above configurations, the radioactivity measuring device is provided with a flow rate adjusting means for controlling the flow rate of the gas provided in the extraction pipe to be supplied to the detecting means to be constant. It is configured to include.

[0011]

In the radioactivity measuring apparatus according to the first aspect, the clean gas is pressurized and introduced from the introduction pipe into the inspection container by the pressurizing pump so that the gas in the inspection container is pushed out from the inspection container. It is sent to the detection means through the extraction pipe. Therefore, the pressure inside the inspection container rises due to the introduction of the clean gas by the pressurizing pump, and the gas flows out of the inspection container into the radioactivity shielding container, so that the air inside the radioactivity shielding container does not flow into the inspection container. Can be stopped.

In the radioactivity measuring device according to claim 2,
The radioactivity concentration in the radioactivity shielding container is detected by the auxiliary detecting means, and the pressure control means which receives the detection signal from the auxiliary detecting means performs the pump pressure control according to the radioactivity concentration in the radioactivity shielding container. . For example, when the radioactivity concentration in the radiation shielding container is high, the ratio of FP gas mixed into the inspection container becomes high. Therefore, the pump pressure should be increased in order to increase the outflow amount from the inspection container to the radiation shielding container. When the radioactivity concentration in the radioactivity shielding container is low, the pump pressure can be lowered.

In the radioactivity measuring device according to claim 3,
The flow rate of the gas supplied to the detecting means is controlled to a constant value by the flow rate adjusting means. Since the radioactivity concentration in the detection means is determined by the radiation count rate with respect to the total flow rate, if the flow rate can be controlled to be constant, the supply flow rate can be accurately obtained, and the measurement accuracy can be improved.

[0014]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a configuration diagram of a radioactivity measuring apparatus according to the first embodiment of the present invention. Inside the cell 20 which will be the radioactivity shielding container,
Inspection container 21, detection container 22, vitrified body 2 before inspection
3 are arranged.

The inspection container 21 is similar to a commonly used container, and is a bottomed container having an open upper end surface. A lid 24 is simply placed on the upper end opening of the inspection container 21, and a vitrified body 25 is stored in the container.

The detection container 22 communicates with the inspection container 21 through a discharge pipe described later, and a radiation detector 26 is provided in the container. The radiation detector 26 is the detection container 2
It is electrically connected to a measuring device 27 arranged outside the cell passing through the inside of the cell 2.

The measuring device 27 has a function of processing a radiation detection signal from the radiation detector 26 to determine whether or not the FP gas leaks from the vitrified body 25 in the inspection container 21.

On the other hand, the inspection container 21 is connected with an introduction pipe 28 for introducing a clean gas into the inspection container 21 from the outside of the cell 20. A gas supply source filled with a clean gas such as a gas cylinder is connected to the tip of the introduction pipe 28.
A pressurizing pump 29 is provided outside the cell in the middle of the introduction pipe 28.

The pressurizing pump 29 serves to send the clean gas supplied from the gas supply source into the inspection container 21 by pressurizing it. Further, the inspection container 21 is connected to a discharge pipe 31 for guiding the gas pushed out of the inspection container 21 by the pressurization of the pressurizing pump 29 to an exhaust system (not shown). The detection container 22 described above is attached inside the cell in the middle of the discharge pipe 31.

In this embodiment constructed as described above, the vitrified body 25 is housed in the inspection container 21 before the start of measurement, and then the lid 24 is placed on the upper end opening of the inspection container 21 for inspection. The inside of the container 21 is simply sealed.

During the measurement period, the inspection container 2 is connected to the gas supply source.
The clean gas supplied to the No. 1 via the introduction pipe 28 is further pressurized by the pressurizing pump 29 and sent into the inspection container 21. As a result, the gas in the inspection container 21 is pushed out to the detection container 22 side together with the clean gas. The pressure inside the inspection container 21 is higher than the atmosphere inside the cell 20 because the clean gas is introduced into the inspection container 21 while being pressurized on the inlet side.
As a result, some of the gas in the inspection container 21 flows out from the gap between the inspection container 21 and the lid 24, so that the gas in the cell 20 can be prevented from flowing into the inspection container 21.

Therefore, even if the FP gas leaks from the vitrified body 23 temporarily placed in the cell 20 and exists in the atmosphere in the cell 20, the FP gas is not mixed in the inspection container 21. Disappear.

In this way, only the gas in the inspection container 21 and the clean gas are introduced into the detection container 22 through the exhaust pipe 31, and the radiation detector 26 if the FP gas is contained.
And the radiation detection signal is sent to the measuring device 27.

As described above, according to this embodiment, the inspection container 21
To the introduction pipe 28 for introducing clean gas to the pressurizing pump 29
Since the clean gas is pressurized and sent to the inspection container 21, the air in the cell 20 is not sucked into the inspection container 21, and the F existing in the cell 20 is prevented.
Accurate measurement is possible without being affected by P gas.

Next, a second embodiment of the present invention will be described. FIG. 2 is a configuration diagram of the radioactivity measuring apparatus according to the second embodiment. The same components as those in the first embodiment described above are designated by the same reference numerals.

The radioactivity measuring apparatus of this embodiment is provided with the inspection container 2
A pressure pump 32, which can control the pressure from the outside, is provided in the introduction pipe 28 for introducing the clean gas to the No. 1 unit. Further, in the cell 20, a radiation detector 33 is installed as an auxiliary detecting means for detecting the radioactivity concentration in the cell 20. The radiation detector 33 is connected to the controller 35 via an interface 34 installed outside the cell 20. This controller 35 is the pressurizing pump 3
Control 2

In the present embodiment, when the measurement is started, the controller 35 controls the pressurizing pump 32 to pressurize the pressurizing pump 32 at a predetermined pressure and send the clean gas into the inspection container 21. On the other hand, the radioactivity concentration in the cell 20 is detected by the radiation detector 33 and input to the controller 35 via the interface 34 in real time.

The controller 35 adjusts the pressure of the pressurizing pump 32 according to the radioactivity concentration detected by the radiation detector 33. Specifically, the pressure of the pressurizing pump 32 is increased as the radioactivity concentration in the cell 20 increases.

Radioactivity concentration in the cell 20 (radiation concentration by the FP gas from the temporarily set vitrified body 23)
The higher the value, the higher the probability that the FP gas of the cell 20 will mix into the inspection container 21, so the blocking rate is changed according to the mixing probability.

Further, since the radioactivity concentration in the cell 20 also increases due to the increase in the background, in such a case, the pressurizing pressure by the pressurizing pump 32 is increased and it is sent to the detection container 22 as described above. By increasing the flow rate, the influence of background is relatively low.

According to the present embodiment as described above, there is an advantage that the blocking rate can be adjusted according to the mixing probability of the FP gas in the cell 20. In addition, the influence of the background can be reduced and highly accurate measurement can be performed.

Next, a third embodiment of the present invention will be described. FIG. 3 is a configuration diagram of a radioactivity measuring apparatus according to the third embodiment. The same components as those in the first and second embodiments described above are designated by the same reference numerals.

The radioactivity measuring apparatus of this embodiment is provided with the inspection container 2
A flow meter 36 and a flow rate adjusting valve 37 are provided in a discharge pipe 31 connecting between 1 and the detection container 22. Flow meter 3
6 and the flow rate adjusting valve 37 are both connected to the controller 35 'through an interface 34' installed outside the cell. Further, the radiation detection signal of the radiation detector 33 installed in the cell 20 is input to the controller 35 '.

In the present embodiment configured as described above, the controller 35 'controls the pressurizing pump 32 to pressurize the clean gas and send it to the inspection container 21, and at the same time, the radioactivity concentration detected by the radiation detector 33. Accordingly, the pressure control described in the second embodiment is performed on the pressurizing pump 32.

On the other hand, the controller 35 'includes the flowmeter 3
The flow rate control valve 37 is controlled so that the flow rate signal from 6 is taken in and the flow rate sent to the detection container 22 is always a constant flow rate.

Here, in the measuring device 27, the radiation count rate with respect to the total flow rate introduced into the detection container 22 in a predetermined period,
Measuring the gas concentration. Therefore, the controller 3
If the pressure change is based on the command from 5 ', the flow rate change corresponding to the pressure change can be calculated and the measured value can be corrected. However, if the pressure of the pressurizing pump 32 fluctuates due to factors other than the command from the controller 35 ', the data cannot be corrected in the calculation, and a measurement error will be included.

According to the present embodiment, the flow rate sent to the detection container 22 is constantly adjusted to a constant flow rate by the flow meter 36 and the flow rate adjusting valve 37, so that the measurement accuracy can be improved.

In the above embodiment, the pressure adjustment of the pressurizing pump 32 and the constant control of the flow rate are carried out at the same time, but only the constant control of the flow rate may be carried out independently. The present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

[0039]

As described above in detail, according to the present invention, it is possible to prevent the FP gas leaking into the cell from the vitrified body other than the inspection object from flowing into the inspection container, and It is possible to provide a radioactivity measuring device capable of accurately measuring only the FP gas from the installed vitrified body.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a radioactivity measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a radioactivity measuring apparatus according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a radioactivity measuring apparatus according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a conventional radioactivity measuring device.

[Explanation of symbols]

20 ... Cell, 21 ... Inspection container, 22 ... Detection container, 23 ...
Temporarily placed vitrified body, 24 ... Lid body, 25 ... Vitrified body, 26, 33 ... Radiation detector, 27 ... Measuring instrument, 28 ...
Introducing piping, 29 ... pressurizing pump, 31 ... discharging piping.

Claims (3)

[Claims] 1. An introduction pipe for guiding a clean gas to an inspection container in which a subject is placed, which is installed in a radioactivity shielding container,
A pressure pump provided in the introduction pipe for feeding the clean gas into the inspection container, an extraction pipe for extracting the gas in the inspection container to the outside of the container, and a gas extracted from the inspection container in the extraction pipe And a detecting means for detecting the radioactivity concentration of the radioactivity measuring device. 2. An auxiliary detection unit for detecting the radioactivity concentration in the radioactivity shielding container, and a pressurizing pump of the pressurizing pump according to the radioactivity concentration in the radioactivity shielding container detected by the auxiliary detection unit. The radioactivity measuring device according to claim 1, further comprising a pressure control means for controlling a pump pressure. 3. The radioactivity measurement according to claim 1 or 2, further comprising flow rate adjusting means provided in the extraction pipe for controlling the flow rate of the gas supplied to the detecting means to a constant value. apparatus.