JPH03231196A - Radioisotope container - Google Patents

Abstract

PURPOSE:To improve the precision in radiation measurement by a method wherein an insertion part wherein a radiation detector for detecting the radiation of a radioactive material contained in the main body of a container is inserted is provided in the main body of the container along the direction of the center thereof. CONSTITUTION:An insertion part 1a is formed in the main body 1 of a tubular container the upper end of which is sealed hermetically by a cap 3, so that a neutron detector 4 can be inserted thereinto toward the central part of the container. This insertion part 1a is a well-type cavity formed from the base of the main body 1 toward the central part thereof. A uranium dioxide 2, for instance, is contained in the main body 1, and when the total amount of this uranium dioxide 2 is measured, the detector 4 is inserted into the insertion part 1a. A signal from the detector 4 is connected to a measuring circuit 5. In a radioisotope container provided with the insertion part 1a enabling installation of the detector 4 in the central part in this way, the count of neutrons is large in the central part of the main body 1, while it lessens toward both ends.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to radioactive materials for storing radioactive materials used in, for example, nuclear power plants, nuclear fuel processing plants, or fuel reprocessing facilities. Regarding storage containers.

(Conventional technology) Nuclear fuel processing plants for processing into nuclear fuel for nuclear power plants or reprocessing plants for reprocessing spent fuel used in nuclear power plants store nuclear fuel, which is radioactive material, in special storage containers. ing.

In order to non-destructively identify the radioactive isotopes in the contents contained in these storage containers, it is necessary to measure the radiation emitted from the radioactive materials.

FIG. 5 shows a storage container containing uranium dioxide powder before being processed into fuel pellets to be used in a nuclear power plant in a nuclear fuel processing plant, and a case in which this storage container is subjected to radiation measurements. In the figure, uranium dioxide 2 is contained in a container body 1 whose cross section is rough, and then the container body 1 is sealed with a lid 3. Uranium dioxide constantly generates neutrons because U-238 undergoes spontaneous nuclear fission. A neutron detector 4 is provided to detect these neutrons, and this neutron detector 4 is connected to a measurement circuit 5.

(Problems to be Solved by the Invention) However, the radioactive substance container having such a shape has the following problems.

FIG. 6 is a graph showing the number of neutrons counted by the measuring circuit 5 in FIG. 5 on the vertical axis and the diameter of the container body 1 on the horizontal axis. Note that the width of the horizontal axis is the same as the diameter of the container body 1 shown in FIG. As is clear from FIG. 6, the number of neutron counts in the measuring circuit 5 is large on the surface of the container body 1, and gradually decreases toward the center.

This is because the amount of uranium dioxide 2 serving as a neutron absorber existing between the neutron detector 4 and the neutron detector 4 increases along the center direction. In such cases, calculating the total amount of uranium dioxide from the number of neutron counts poses a problem with accuracy because the neutron detection efficiency is low.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a radioactive substance storage container that can improve the measurement accuracy of radiation measurement.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes a container body having a sealed structure, and a device provided along the center direction of the container body to detect radiation of a radioactive substance contained in the container body. and an insertion section into which a radiation detector is inserted.

(Function) In the present invention, by inserting a radiation detector into the insertion portion when measuring the radioactive substance contained in the container main body, the measurement can be performed non-destructively and with high precision.

(Example) The first example of the radioactive material storage container according to the present invention is shown in the first example.
This will be explained with reference to the figures and FIG. In addition, the same parts in the figure as in FIG. 5 are given the same reference numerals, and the explanation of the overlapping parts will be omitted.

In FIG. 1, an insertion portion 1a is formed in a cylindrical container body 1 whose upper end is sealed with a lid 3 so that a neutron detector 4 can be inserted toward the center.

The insertion portion 1a is a well-shaped recess formed from the bottom of the container body 1 toward the center.

For example, uranium dioxide 2 is contained within the container body. When measuring the total amount of uranium dioxide 2, a neutron detector 4 is inserted into the insertion portion 1a. Neutron detector 4
The signal from is connected to the measuring circuit 5.

The operation of the radioactive substance container provided with the insertion part 1a that can be installed in the center of the neutron detector 4 will be explained. FIG. 2 is a graph in which the number of neutrons counted by the measuring circuit 5 in FIG. 1 is plotted on the vertical axis and the diameter of the container is plotted on the horizontal axis, as in the conventional example.

As is clear from FIG. 2, since the amount of uranium dioxide which acts as a neutron absorber decreases, the number of neutrons counted increases in the center of the container body 1. The count decreases toward both ends.

FIG. 3 shows a second embodiment of the present invention, in which a tunnel-shaped insertion portion 1a is formed passing through the center of the container body 1. The other parts are the same as those in the first embodiment, so their explanation will be omitted. This embodiment has the advantage that the neutron detector 4 can be inserted from either the left or the right.

FIG. 4 shows a third embodiment of the present invention, in which the lid 3 is provided with an insertion portion 1a. According to this embodiment, since the neutron detector 4 is inserted from above, operability is easy.

The operations of the container and radiation measuring device shown in FIGS. 3 and 4 are the same as in the first embodiment.

In each of the above embodiments, a nuclear fuel material storage container containing uranium dioxide at a fuel fabrication plant was described as an example, but the same can be applied to a nuclear fuel material storage container containing nuclear fuel material produced at a reprocessing plant, for example. Furthermore, similar effects can be obtained in cases other than neutron measurements, such as gamma ray measurements.

[Effects of the Invention] According to the present invention, radiation detection efficiency can be increased and radiation can be measured with high accuracy in a non-destructive manner.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a radioactive material storage container according to the present invention, FIG. 2 is a characteristic diagram showing the action in FIG. 1, and FIGS. FIG. 5 is a configuration diagram showing a conventional radioactive material storage container, and FIG. 6 is a characteristic diagram showing the operation in FIG. 5. 1... Container body 1 a... Insertion section... Uranium dioxide 3... Lid 4... Neutron detector 5... Measurement circuit (8733)

Claims (1)

[Claims] It is characterized by comprising a container body with a sealed structure, and an insertion part provided along the center direction of the container body and into which a radiation detector for detecting radiation of the radioactive substance contained in the container body is inserted. radioactive material storage container.