JPH06148380A - Inspection method of reactor core internal structure - Google Patents

Abstract

PURPOSE:To enable inspection of displacement and deformation of core support plates and a connecting tube part. CONSTITUTION:A fuel assembly is pulled out from a connecting tube 4 supported by core support plates 3 and a jig 7 for inspection is inserted in place of it. The top part of the jig 7 for inspection is provided with a marking or a target. With this marking or the target used as a mark, displacement and a tilt of the jig 7 for inspection are observed and measured by an ultrasonic transducer 14 fitted to an inspection device through sodium 13 and displacement and deformation of the core support plates 3 and the connecting tube 4 are detected therefor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting core internals for supporting core fuel of a fast breeder reactor.

[0002]

2. Description of the Related Art As a method of inspecting the internal structure for supporting the core fuel of a fast breeder reactor, a high temperature of 200 ° C. or higher, a liquid sodium atmosphere, a high radiation Since it is in an environment, a method of observing and measuring the displacement and deformation of the reactor core top level with a sodium see-through device when the reactor is shut down, a contact scanning method of measuring from the reactor top plug using the reactor core top level and jig, etc. Has been considered.

Next, a method of inspecting the displacement and deformation of the core support structure by the sodium see-through device will be described with reference to FIG.

In FIG. 3, reference numeral 1 is a reactor vessel,
Inside the reactor vessel 1, a reactor internal structural support structure 2 is installed. The core support plate 3 is attached to the core structure support structure 2.
And a connecting pipe 4 is erected on the core support plate 3,
The entrance nozzle portion of the fuel assembly 6 is inserted into the connecting pipe 4. The reactor core 5 is provided outside the fuel assembly 6.

A shield plug 11 and a rotary plug 12 are provided and closed at the upper end opening of the reactor vessel 1.
A sodium see-through device 13 having an ultrasonic transducer 14 is vertically installed in the rotary plug 12, and sodium 10 as a coolant is contained in the reactor vessel 1.

FIG. 3 shows that the deformation of the in-core structural support structure 2 of the core support structure appears at the top of the core cistern 5 so that markings provided on the top of the core cistern 5 by the sodium see-through device 13 or A method for measuring the displacement and deformation of the in-core structural support structure 2 by observing and measuring the target, and measuring and organizing data in four directions at 90 ° horizontal displacement and vertical displacement. Is.

[0007]

The conventional inspection method is very effective in measuring the deformation of the entire core supporting structure. However, it is not effective in observing the displacement and deformation of each component of the core support structure, and in particular, the core support plate 3 and the connecting pipe that are exposed to thermal transients due to the most severe neutron irradiation of the core support structure. No information is available on the four copies.

As described above, the conventional technique has a problem that the core support plate and the connecting pipe portion that are subjected to the most severe neutron irradiation among the core support structures and are also exposed to the thermal transient cannot be inspected.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a method for inspecting internal structures capable of inspecting the displacement and deformation of the core support plate and the connecting pipe portion.

[0010]

According to the present invention, an inspection jig having a lower entrance nozzle which can be tightly mounted on a connecting pipe portion is inserted into the connecting pipe instead of the fuel assembly loaded in the reactor core. By utilizing the fact that the displacement and deformation of the core support plate and the connecting pipe part are amplified and displayed as displacement and inclination on the top of this inspection jig by the function of this inspection jig, the displacement and inclination of the top can be utilized. Is characterized by inspecting and measuring with a fluoroscope in sodium to inspect displacement and deformation of the core support plate and the connecting pipe part.

[0011]

When the core support plate is displaced or deformed, the displacement and deformation of the core support plate 3 and the connecting pipe 4 are amplified by the inspection jig 7 and appear on the inspection jig top. The marking or the target is observed and measured by the ultrasonic transducer of the fluoroscope 13 in sodium.

Thus, the displacement and deformation of the core support plate and the connecting pipe can be inspected.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for inspecting a reactor internal structure according to the present invention will be described with reference to FIGS.

In FIG. 1, a reactor internal structure support structure 2 is installed in a reactor vessel 1. A core support plate 3 is provided on the in-core structure support structure 2, and the core support plate 3
A connecting pipe 4 is erected on the inside of the connecting pipe 4, and an inspection jig 7 is inserted into the connecting pipe 4. The reactor core 5 is provided outside the inspection jig 7.

A shield plug 11 and a rotary plug 12 are provided at the upper end opening of the reactor vessel 1. Rotating plug
A sodium see-through device 13 having an ultrasonic transducer 14 is vertically provided at 12, and sodium 10 as a coolant is contained in the reactor vessel 1. In the figure, reference numeral 15 is an arm for adjusting the angle of the ultrasonic transducer 14.

Here, in order to examine the displacement and deformation of the core support plate 3 and the connecting pipe 4, the fuel assembly 6 in the core tank 5 shown in FIG. 3 is pulled out, and the inspection jig 7 is connected instead. Insert in 4 tubes.

The inspection jig 7 has an entrance nozzle portion which can be tightly attached to the connecting pipe 4 at the lower portion, and a handling head 9 portion which can be handled by the fuel exchange device at the upper portion, and in FIG. 2 (d). As shown, a different marking or target 8 is provided on the top of the handling head 9 for each address so that it can be easily observed and measured by the ultrasonic transducer 14.

Further, in the inspection jig 7, the diameter of the fuel assembly 6 at the position corresponding to the trumpet pipe is made smaller than that of the fuel assembly, so that the displacement and deformation in the core support plate 3 and the connecting pipe 4 are gathered around. It is designed to appear on the top of the inspection jig 7 without being affected by the body.

The displacement and inclination of the apex of the inspection jig 7 thus appearing are shown in FIG. 2 (c). For the fuel assembly in the reactor core 5, radial and circumferential addresses are marked or targets 8 are marked. Then, the displacement and deformation of the whole core support plate 3 can be inspected by examining the ultrasonic transducer 14 of the sodium see-through device 13 at a plurality of locations.

FIG. 2A shows the case where the core support plate 3 is not displaced or deformed, and FIG. 2B is the case where the core support plate 3 is displaced or deformed.
This is the case when deformation has occurred.

The positions (A) and (B) in FIGS. 2A and 2B are on the extension of the core center as shown in FIG. 2C, and the radial addresses are different. . Therefore, for example, when the positions of the fuel assemblies of (A) and (B) are inspected, if inclination is recognized as shown in FIG. 2B, it is understood that some abnormality has occurred in the core support plate 3.

[0022]

According to the present invention, it is possible to easily perform displacement and deformation inspection of core internals such as the core support plate and the connecting pipe portion, which could not be inspected in the past, by the combination of the sodium see-through device and the inspection jig. It can be carried out.

Further, by making the inspection jig to have substantially the same outer shape and dimensions as the fuel assembly, it becomes easy to carry out the work in and out of the furnace by the fuel exchange device and the fuel in / out machine. Furthermore, since permanent structures such as reactor internal structures do not need to be modified for inspection, they can be applied to existing fast reactor plants.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view for explaining an embodiment of a method for inspecting an internal structure according to the present invention.

2 (a) is an elevation view when the core support plate in FIG. 1 is not displaced or deformed, and (b) is an elevation view when the core support plate is similarly displaced or deformed, (C) is a plan view showing the core in FIG. 1 for explaining (a), and (d) is an enlarged elevational view showing a d portion in (a).

FIG. 3 is a vertical cross-sectional view for explaining a conventional method for inspecting a reactor internal structure.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor vessel, 2 ... Reactor internal structure support structure, 3 ... Core support plate, 4 ... Connection pipe, 5 ... Reactor tank, 6 ... Fuel assembly, 7 ...
Inspection jig, 8 ... Marking or target, 9 ... Handling head, 10 ... Sodium, 11 ... Shield plug, 12 ... Rotating plug, 13 ... Sodium see-through device, 14 ...
Ultrasonic transducer, 15 ... arm.

Claims (1)

[Claims] 1. A fuel assembly is drawn out from a connecting pipe supported by a core support plate, and a lower entrance nozzle that can be tightly mounted on the connecting pipe from which the fuel assembly is drawn is provided, and a target or marking is provided on the top thereof. The inspection jig is inserted, and the displacement and inclination of the top of the inspection jig after insertion are observed and measured by a sodium see-through device to detect the displacement and deformation of the core support plate and connecting pipe. A method for inspecting a structure inside a furnace, which is characterized by the above.