JP2941138B2 - Γ-ray and neutron flux measurement equipment in the reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for easily measuring gamma rays and neutron flux in a reactor when the reactor is shut down,
A gamma-ray / neutron flux measurement device that is underwater specification and can be used to measure locations where equipment with a high dose equivalent rate is stored or used in water, such as in a pool where spent fuel bodies are stored and stored Things.

[0002]

2. Description of the Related Art Conventionally, gamma rays and neutron flux in a reactor when the reactor is shut down are obtained by calculation using a prediction analysis code, and based on the calculation results, core management when the reactor is shut down and the inside of the reactor are calculated. This is reflected in the design of radiation resistance and irradiation tests related to the development of inspection equipment for structures.

[0003]

However, the accuracy of the predictive analysis code is unknown because there is no actual measurement data of gamma rays and neutron flux in the reactor, and there is a margin in developing core management and inspection equipment. It was necessary to take measures such as anticipation. Therefore, γ in the reactor when the reactor is stopped
It is desirable to easily measure the wires and neutron flux, evaluate and review the accuracy of the prediction analysis code, and reflect it in the design related to the core management when the reactor is shut down and the development of inspection equipment for reactor internal structures. However, the measurement had the following problems to be solved.

[0004] In the case of the Fugen power plant, the reactor is composed of 224 elongated tubes having an inner diameter of about 120 mm, called pressure tubes, on which a fuel body is mounted. It is necessary to insert the device into the pressure tube, and the size of the outer diameter is limited.

The distribution of gamma rays and neutron fluxes in the reactor has a difference in the direction of the vertical axis. To measure this distribution, the entire area of the pressure tube constituting the reactor having a length of about 5 m is measured. There is a need.

[0006] The cooling water (light water) of one pressure pipe to be measured cannot be withdrawn structurally, and the entire cooling water cannot be withdrawn because the fuel body is loaded in another pressure pipe. Therefore, the device needs to be underwater.

[0007] The opening and closing of the pressure pipe constituting the reactor is located at the lowermost end, and the seal is made by a special plug. When the apparatus is inserted into the pressure pipe, this plug is used to seal the cooling water. Therefore, the signal cable cannot be routed from the device.

[0008] It cannot be directly measured manually from the structural point of view.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and makes it possible to easily convert γ-rays and neutron flux in a reactor into water without extracting cooling water from the reactor when the reactor is shut down. It is an object of the present invention to provide a gamma-ray / neutron flux measuring device in a nuclear reactor capable of measuring.

[0010]

SUMMARY OF THE INVENTION A gamma ray in a nuclear reactor of the present invention is provided.
The neutron flux measuring device is provided with an aluminum rod inside a hermetically sealed container which is almost the same size as the fuel body and is mounted in the pressure pipe, and along with the aluminum rod, a dosimeter for measuring a large radiation dose or a radiation foil for measuring a neutron flux. Is affixed.

[0011]

According to the present invention, the measurement container for measuring γ-rays and neutron flux in a nuclear reactor is made approximately the same size as the fuel body so that it can be inserted into the pressure tube, and has a closed container structure. When measuring γ-rays, a dosimeter for measuring large radiation dose was used, and when measuring neutron flux, radiation foil was applied over the entire length of the aluminum rod to measure.
The gamma rays and neutron flux in the reactor can be measured in water and very easily without extracting cooling water.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 2, the structure of the nuclear reactor of the Fugen power station is as follows:
224 pressure pipes 3 are vertically arranged in a grid pattern, and a fuel body 4 is loaded on each of the pressure pipes. The replacement of the fuel assembly 4 when the reactor is stopped is performed by remote control by the refueling machine 9, and the seal plug 1 sealing the reactor cooling water in the pressure pipe 3 is also detached and replaced at the same time. The refueling machine 9 is also filled with the same light water as the reactor cooling water, and these replacement operations are all performed underwater. In addition, the vessel 5 for measuring γ-rays and neutron flux in the reactor when the reactor is stopped has the same size as the fuel body 4,
In the same manner as in the replacement work, the fuel exchanger 9 can be mounted in or taken out of the pressure pipe 3.
The steam extracted from the reactor by the steam drum 10 rotates the turbine 11 and drives the generator 12 to generate power.

FIG. 1 is an enlarged view of one of 224 pressure tubes constituting a nuclear reactor, showing a normal fuel body loading state (FIG. 1).
FIG. 1A is a comparison between the measurement container mounted state (FIG. 1B) and FIG. 1C is a partially enlarged view of the measurement container 5. In the normal case shown in FIG. 1 (a), a seal plug 1 for sealing the reactor cooling water is mounted at the lower end of the pressure pipe 3, and a shielding plug 2 is mounted thereon. It is connected and held. When measuring γ-rays and neutron flux in the reactor, the measurement vessel 5 is connected to the shielding plug 2 instead of the fuel body 4 by the fuel exchanger and mounted in the pressure pipe 3 as described above. The measuring container 5 is a closed container. As a small measuring device commercially available, a dosimeter for measuring a large radiation dose is used for measuring γ-rays, and a radiation foil is used for measuring a neutron flux.
The γ-rays and the neutron flux in the reactor are measured by being attached to an arbitrary position over the entire length and inserted into the measurement vessel 5. The dosimeter for measuring large radiation dose is colored by gamma ray irradiation in the reactor, and the degree of this coloring is measured by a spectrophotometer to quantify the intensity of gamma rays. Is to quantify the neutron flux by measuring the nuclides produced by neutron irradiation and the half-life of the produced nuclides with a germanium semiconductor detector.

[0014] As described above, the size of the measuring vessel for gamma rays and neutron flux in the reactor is made substantially the same as that of the fuel body, and a radiation dose for measuring a large radiation dose or a neutron flux is formed in a closed vessel structure. By attaching the foil over the entire length of the aluminum rod, it is possible to easily measure γ-rays and neutron flux in water without extracting cooling water.

[0015]

As described above, according to the present invention, although the inside of the reactor has a very narrow structure, the measuring vessel can be mounted at any position instead of the fuel body.
In addition, it is possible to measure the entire area in the height direction of the reactor (the length of the pressure tube). In addition, mounting and unloading of the measurement vessel in the reactor can be performed remotely by a refueling machine,
There is no need to extract the cooling water from the reactor, and measurement in water is possible. Furthermore, dosimeters for measuring large radiation doses and radiation foils for measuring neutron flux are irradiated in the reactor, then removed from the measurement container and quantified, eliminating the need to route a signal cable. Since the meter and the radiating foil are inserted in the closed vessel, they are not exposed to the reactor cooling water, so that there is no contamination by radioactive substances, and the handling such as limitation of the measuring device accompanying quantification can be greatly simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating the structure of a nuclear reactor.

[Explanation of symbols]

1 ... Seal plug, 2 ... Shield plug, 3 ... Pressure tube,
4 ... Fuel body, 5 ... Measurement vessel, 6 ... Aluminum rod, 7 ... Dosimeter or radiation foil for large radiation dose measurement, 8 ... Container, 9 ... Fuel exchanger, 10 ... Steam drum, 11 ... Turbine, 12 ... Power generation Machine.

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Claims (1)

(57) [Claims] An aluminum rod is provided inside a sealed structure container having the same size as a fuel body and mounted in a pressure tube. A dosimeter for measuring a large radiation dose or a radiation foil for measuring a neutron flux is provided along the aluminum rod. A gamma ray / neutron flux measuring device in a nuclear reactor, which is attached.