JPS58172521A - Method and device for measuring level in radioactive waste liquid storing tank - Google Patents

Abstract

PURPOSE:To measure a boundary level between supernatant liquid and a deposition layer as well as the level of waste liquid without direct contact with the waste liquid, by moving a radiation detector relatively to the direction of the height of a storing tank, and by finding the level from a change in the strength of radiation in the direction of the height of the tank. CONSTITUTION:A radiation detecting apparatus 12 is set adjacently to a storing tank 10, and a lift 15 whereon a shielding vessel 14 is mounted is driven upward at a prescribed speed. A radiation falling into a slender hole 16 of the shielding vessel 14 is detected by a radiation detector 13, subjected to signal processing in a radiation signal processing circuit 18, and compared with a value set beforehand in a discrimination circuit 19. The level of the incident radiation lowers remarkably with the elevation of the radiation detector 13, and when an input measurement signal falls below the set value, the position of the detector 13 is called by a driving control circuit 17 and is indicated in an indicator 21 as the level of waste liquid or a boundary between a deposition layer and supernatant liquid.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is used in radioactive material handling facilities to determine the level of waste liquid in the storage tank by measuring the intensity of radiation in the height direction of the storage tank for storing radioactive waste liquid. The present invention relates to a method for measuring and an apparatus therefor.

[Technical background of the invention]

Conventionally, when measuring the liquid level of waste liquid in a storage tank, a device as shown in FIG. 1 has been mainly used. That is, storage tank 1
A float 6 is floated on the waste liquid 2 inside, and this float 3 is connected to a weight 5 by a wire 4. This weight 5 passes through a shielding wall 6 and is suspended on the side opposite to the storage tank 1. The weight of the weight 5 and the float 3 are adjusted to be balanced by the specific gravity of the waste liquid 2, and as the waste liquid 2 flows in and the liquid level rises, the float 6 rises and the weight 5 descends. A liquid level scale plate 7 is attached near where the weight 5 is suspended, and the liquid level is displayed by this scale plate 7. however,
In such a device, since the float 3, which is a detection part, comes into direct contact with the waste liquid 2, there is a risk that the float 3 will be contaminated with radioactivity and that workers will be exposed to it during maintenance.

Furthermore, when waste liquid is separated into a supernatant liquid and a precipitate, when it is desired to know the boundary between the two, it is very difficult to measure the boundary using the above method, partly because the difference in specific gravity is small.

[Purpose of the invention]

The present invention has been made to address this problem, and includes moving the radiation detector relative to the height direction of the storage tank.
By determining the liquid level from changes in the intensity of radiation in the height direction of the storage tank, it is possible to measure not only the liquid level of the waste liquid in the storage tank, but also the interface between the supernatant liquid and the precipitate layer. The purpose of this project is to provide a method and device for measuring the liquid level in a radioactive waste liquid storage tank that does not come into direct contact with waste liquid.

□、′ [Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 2, a radioactive waste liquid 11 is stored in a storage tank 10, and the waste liquid 11 is divided into a supernatant layer 11& and a sediment layer 11b.
It is divided into A radiation detection device 1 is installed outside the storage tank 10.
2 is installed, and the radiation level from the storage tank 10 is measured.This radiation detector [12 is a radiation detector 16,
It is comprised of a shielding container 14 for housing this radiation detector 16 and shielding it from external radiation, and a lifting platform 15 for placing this shielding container 14 and moving it up and down. The shielding container 14 is provided with a pore 16 at one end facing the storage tank 10, and only radiation passing through the pore 16 is detected by the detector 13.

The driving side of the lifting platform 15 is divided by a drive control circuit 17, and this drive control circuit 17 can program the movement method of the lifting platform 15, and can adjust the moving speed.
The position of the lifting platform 15 can be memorized. 18 is a radiation signal processing circuit that converts the detection signal from the radiation detector 16 and sends the output signal to the discrimination circuit 1? send to In the discrimination circuit 19, this input signal is compared with a preset value, and when the measured value is less than the preset value, the position of the radiation detector 16 at that time is called by the drive control circuit 17. Indicator 21 via signal conversion circuit 20
will be displayed. As shown in FIG. 6, by appropriately selecting these set values, it is possible to display the liquid level and the interface between the sediment layer and the supernatant layer.

Further, the signal from the radiation signal processing circuit 18 is input to the coefficient conversion circuit 22, where the input signal is converted into radioactivity concentration based on the ratio of the measurement signal to the unit radioactivity concentration determined in advance. 26 is a radioactivity concentration display meter, into which a signal indicating the position of the radiation detector 16 from the drive control circuit 17 is input together with a signal from the coefficient conversion circuit 22;
The radioactivity concentration corresponding to the height of the storage tank 10 is displayed. On the other hand, the average calculation circuit 24 inputs the signal from the coefficient conversion circuit 22, performs an integral calculation, calculates the average radioactivity concentration, and outputs it to the radioactivity concentration display meter 26.

Next, the operation of the apparatus configured as above will be explained.

A radiation detection device 12 is installed close to the storage tank 10, and a lifting platform 15 on which a shielding container 14 is placed is driven from bottom to top at a constant speed. The radiation that has entered the pores 16 of the shielding container 14 is detected by the radiation detector 13, subjected to signal processing by the radiation signal processing circuit 18, and then compared with a preset value in the discrimination circuit 19. When the level of incident radiation drops significantly as the detector 16 rises, and the input measurement signal becomes below the set value, the position of that detector 16 is called by the drive control circuit 17, and the liquid level or This is displayed on the indicator 21 as the boundary between the sediment layer and the supernatant layer.

On the other hand, the Ig signal converted by the radiation signal processing circuit 18 is converted into radioactivity concentration by the coefficient conversion circuit 22.
It is displayed on the display meter 26 in correspondence with the height position of the fixed height, and the average radioactivity 1 degree is also calculated in the average calculation circuit 24 and displayed on the display meter 26.

In addition, during measurement, as shown in FIG. 4, by bringing the entrance of the pore 16 as close as possible to the storage tank 10, the range of the curve # of radiation incident on the pore 16 can be reduced, and therefore the measurement accuracy can be improved. I can sell it.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, it is possible to measure the liquid level of waste liquid without having to come into direct contact with the waste liquid, and when a sediment layer exists, it is also possible to measure the boundary surface between the layers. Furthermore, since the radioactivity concentration of the waste liquid can be determined from the measured radiation level, useful information can be obtained regarding the storage and treatment of the waste liquid.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a conventional liquid level measuring device, Fig. 2 is a configuration diagram showing an embodiment of the liquid level measuring device of the present invention, and Fig. 6 shows the height direction of the storage tank and measurement No. 44. A graph showing the relationship between
FIG. 4 is an explanatory diagram showing the relationship between the pores of the shielding container and incident radiation. 1.10... Storage tank 2.11... Waste liquid 16... Radiation detector 17...
...... Drive control circuit 18 ...... Radiation signal processing circuit 19 ...... Discrimination circuit 20 ...... Signal conversion circuit 21 ...... Indicator 26 .....Radioactivity concentration indicator Patent attorney Sa Suyama - Figure 2 No. lb

Claims (1)

[Claims] 1. By measuring the intensity of radiation emitted from a storage tank storing radioactive waste liquid with a radiation detector movable in the height direction relative to the storage tank, A method for measuring the liquid level of a radioactive waste liquid storage tank, characterized in that the liquid level of the waste liquid in the storage tank is determined from a change in the intensity of radiation corresponding to a position in the height direction of the storage tank. 2. A radiation detector that detects radiation from a storage tank that stores radioactive waste liquid, a shielding container that houses this detector and has a pore for narrowing down the radiation that enters the detector, and a shielding container that is connected to the storage tank. a drive circuit that moves the shielding container relative to the storage tank in the height direction, a position measurement circuit that measures the position of the shielding container in the height direction with respect to the storage tank, and a radiation signal processing circuit that processes the signal from the radiation detector. A liquid level measuring device for a radioactive waste liquid storage tank, characterized by comprising: