JPH0337146B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radioactivity map measurement device that can remotely and automatically measure the maximum surface dose rate and radioactivity concentration distribution by nuclide from the outside of a radioactive waste container.

For radioactive waste containers filled with radioactive waste generated at facilities that handle radioactive materials such as nuclear power plants, it is necessary to determine the distribution of radioactivity concentration and the maximum surface dose rate for radiation management purposes. However, with conventional devices, it has not been possible to automatically check the distribution of radioactive substances contained within the radioactive waste container from the outside of the container by nuclide. That is, a radioactive waste packing container is rotated and moved up and down at a constant speed, and radiation such as gamma rays emitted from the container is measured by a radiation detector via a collimator and scanned in a spiral pattern over the entire surface of the container. There is a known device that can calculate the radioactivity concentration and average surface dose rate for each nuclide contained in the entire radioactive waste container from data analysis. It had the disadvantage that the distribution and maximum surface dose rate could not be determined.

On the other hand, the surface dose rate of radioactive waste containers is stipulated to record its maximum value.
Traditionally, humans have surveyed the surface of the container using an ionization chamber survey meter, etc. to find the maximum surface dose rate, but it has been reported that in this case, the radiation exposure of workers increases. There was a problem.

Therefore, in order to reduce radiation exposure as much as possible,
A device that can perform such measurements remotely and automatically is needed.

The present invention has been made to address these points,
a collimator that narrows down radiation disposed outside a container containing radioactive waste; a radiation detector disposed behind the collimator; a radiation spectrometer connected to the radiation detector; a storage device having a storage space corresponding to area elements formed by dividing in the dimensional direction;
A drive mechanism for vertically and rotating the container, and a drive mechanism are controlled, and the spectrum data outputted from the radiation spectrometer is recorded in each storage space of the storage device in correspondence with the area element. By being equipped with a computer to analyze the distribution status of radioactivity by type, the concentration distribution and maximum surface dose rate of radioactivity by nuclide in radioactive waste packaging containers can be remotely and automatically measured.
The present invention provides a radioactivity map measuring device that can reduce radiation exposure of workers.

An embodiment of the present invention will be described below based on the drawings.

As shown in FIG. 1, the radioactivity map measuring device includes a collimator 3 that narrows down the γ-rays emitted from the radioactive waste container 1, a γ-ray detector 4, a γ-ray spectrometer 5, a computer 6, a storage device 7, and The main body is composed of the drive mechanism control device 8.

For example, a radioactive waste container (hereinafter referred to as a drum) consisting of a drum filled with solidified radioactive waste is placed on a rotating table, and is rotated and vertically driven by drive motors 2, 2. A collimator 3 and a gamma ray detector 4, such as a semiconductor detector, are fixedly arranged on the drum can 1 at a position where the entire surface of the drum can can be scanned, and a gamma ray spectrometer 5 is connected to the gamma ray detector 4. be done. The gamma ray spectrometer 5 consists of an amplifier and a multi-channel wave height analyzer, and amplifies the electrical signal obtained by the gamma ray detector 4, converts it from analog to digital, performs spectrum analysis, and sends the output signal to the computer 6. is input. The computer 6 records this input data in the storage device 7 and issues a command to the drive mechanism control device 8 to move the surface of the drum 1 in the scanning direction.

Here, the surface of the drum 1 is divided into finite two-dimensional area elements as shown in FIG. 2a, and the storage device 7 has a storage space corresponding to each area element as shown in FIG. 2b. Data corresponding to each area element of the drum can 1 is recorded in the storage space. The computer 6 analyzes each recorded data and calculates the radiation intensity C and surface dose rate for each nuclide at each position on the surface of the drum 1, and calculates the radioactivity distribution A for each nuclide inside the drum 1 and the maximum surface The dose rate is determined. Here, radioactivity distribution A by nuclide inside drum 1
In order to obtain the gamma ray absorption effect
can be calculated from the following equation based on the relationship with the nuclide-specific radioactivity intensity C on the surface of the drum 1.

A=X・C The calculation result of the computer 6 is output to an input/output device 9 such as a printer.

Next, the operation of this device will be explained. First, γ is released from the area element [1] on the surface of the drum 1.
The rays are detected by a gamma ray detector 4 via a collimator 3, and a gamma ray energy spectrum is determined by a gamma ray spectrometer 5. The computer 6 records this spectrum at address [1] of the storage device 7, and then issues a command to the drive mechanism control device 8,
The driving motor 2 is operated to move the position of the surface of the drum 1 to detect the gamma rays of the area element [2]. Then, the gamma ray energy spectrum is recorded at address [2] of the storage device 7, and this operation is repeated one after another to scan the entire surface of the drum can 1. The radiation intensity and surface dose rate for each nuclide are determined by the computer 6 from the recorded spectra, and as a result, the radioactivity distribution and surface dose rate distribution for each nuclide inside the drum 1 are calculated.

As explained above, the radioactivity map measuring device of the present invention can remotely and automatically measure the radioactivity distribution by nuclide and the maximum surface dose rate of a radioactive waste packaging container. The radiation dose caused by approaching the container and examining it with a survey meter can be greatly reduced. Furthermore, by using a semiconductor detector with high performance, the detection efficiency can be corrected more strictly than with a conventional survey meter, and therefore, more accurate measurement is possible. Furthermore, the computer can quickly and accurately correct the detection efficiency and analyze and evaluate the measured data.

Furthermore, the time required for measurement can be shortened by using a plurality of radioactive detectors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
Figure a shows an example of division of the surface of a radioactive waste container, and Figure 2b shows the address of the storage device corresponding to figure a. 1... Radioactive waste packing container, 2... Drive motor, 3... Collimator, 4... γ-ray detector, 5...
...γ-ray spectrometer, 6...computer,
7...Storage device, 8...Drive mechanism control device, 9...
...I/O device.

Claims (1)

[Claims] 1. A collimator that narrows down radiation placed outside a container containing radioactive waste, a radiation detector placed behind the collimator, and a radiation spectrometer connected to the radiation detector.
a storage device having a storage space corresponding to area elements formed by dividing the container surface in two-dimensional directions; a drive mechanism for vertically and rotating the container; and a drive mechanism for controlling the drive mechanism and for controlling the storage device. A radioactivity map, comprising: a computer for storing spectrum data outputted from the radiation spectrometer in each storage space in correspondence with the area element, and for analyzing the distribution of radioactivity by nuclide. measuring device.