JPH0528799B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a core instrumentation device for a restrained breeder reactor, and more particularly to fuel assembly outlet instrumentation in which the structure of the shielding portion of the instrumentation well is improved.

[Technical background of the invention and its problems]

Generally, in a fast breeder reactor, a core instrumentation device measures the flow rate and temperature of sodium flowing out from the fuel assemblies that make up the reactor core.

As shown in FIG. 3, a reactor core 3 is housed in a reactor vessel 1, and is filled with sodium 5. The upper part of the reactor vessel 1 is covered with a shielding plug 7, and a core upper mechanism 9 is provided on the shielding plug 7. A large number of core instrumentation devices 11 are arranged in this core upper mechanism 9.

Now, the core instrumentation device 11 of the fast breeder reactor includes an instrumentation well 13 extending in the longitudinal direction of the upper core mechanism 9.
A detector for detecting the flow rate and temperature of sodium 5 is housed in the inner tip (lower end).
A cable is connected to this detector, and this cable extends upward within the instrumentation well 13.

On the other hand, the shielding plug 7 shields neutrons and gamma rays emitted from radioactive substances within the reactor vessel 1. Further, the inside and surroundings of the instrumentation well 13 in the core instrumentation device 11 are also shielded by some kind of shielding means. Among these, the shielding inside the instrumentation well 13 is conventionally
This is done by a lid-shaped shielding part configured to cover the upper end of the. However, during maintenance and inspection of the core instrumentation device 11, the detector in the instrumentation well 13 is pulled out along with the cable and replaced with a new detector, etc., and at that time, it is necessary to remove and reinstall the shield. Therefore, the core instrumentation device 1
There is a drawback that the maintenance and inspection work in step 1 becomes complicated.

Therefore, it has been proposed that a cylindrical shielding part is attached to the cable housed in the instrumentation well 13, and the inside of the instrumentation well 13 is shielded by this shielding part. This shielding part is, for example, a stainless steel cylinder with a longitudinal length of 1 to 2 m, and a cable is attached to the inside thereof by passing through it. However, since this shielding part has a straight cylindrical shape,
If the instrumentation well 13 extends in a straight line, there is no problem in extracting and inserting the detector, but if the instrumentation well 13 has a curved portion 15, a problem occurs. In other words, the shielding part gets caught on this curved part 15, making it difficult to pull out the detector. Therefore, in this case as well, there is a drawback that maintenance and inspection work for the core instrumentation device becomes complicated.

[Purpose of the invention]

This invention was made in consideration of the above-mentioned circumstances, and it is possible to easily pull out and insert the detector from the instrumentation well, thereby improving the workability of maintenance and inspection work of the core instrumentation device. Another object of the present invention is to provide a core instrumentation device for a fast breeder reactor that can reliably ensure the integrity of the shielding part when extracting and inserting a detector.

[Summary of the invention]

The core instrumentation device for a fast breeder reactor according to the present invention includes:
An instrumentation well arranged in the upper core mechanism of a fast breeder reactor, a detector housed in the tip part of this instrumentation well, and a detector attached to a cable inside the instrumentation well that runs inside this instrumentation well. and a shielding part for shielding, wherein the shielding part is configured to include a large number of spherical shielding elements and element fixing members, and each shielding element has a distance from each other in the axial direction of the cable, and the cables are arranged in a row in an axial direction without any intervening material, and the element fixing members are located at both ends of a large number of the shielding elements and fixed to the cables, and the shielding elements When the cable with the mark is not bent, only the bending resistance force of the cable itself acts and no other bending resistance force acts, so the shield part corresponds to the shape of the curved part of the instrumentation well. Element fixing members that are fixed to the cable at both ends of a large number of shield elements prevent the shield elements from being separated in the cable axial direction.

[Embodiments of the invention]

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

FIG. 1 is an enlarged sectional view of a part of an embodiment of a core instrumentation device for a fast breeder reactor according to the present invention, and FIG. 2 is a sectional view of a fast breeder reactor to which the embodiment is applied.

As shown in FIG. 2, a reactor core 25 is housed in a reactor vessel 23 of a fast breeder reactor 21, and is filled with sodium 27. Further, a shielding plug 29 is provided at the upper end of the reactor vessel 23 . This shielding plug 29 shields neutrons and gamma rays emitted from radioactive substances inside the reactor vessel 23. The shielding plug 29 is provided with a core upper mechanism 31 above the core 25, and a core instrumentation device 33 that performs exit instrumentation of the fuel assembly is attached to the core upper mechanism 31. A large number of core instrumentation devices 33, for example about 200, are attached to the fuel assembly sheets in the reactor core 25. Each core instrumentation device detects the flow rate and temperature of sodium flowing out from each fuel assembly.

In other words, as shown in FIG.
3, the cable 3 is installed in the cylindrical instrumentation well 35.
A detector 41 connected to cables 37 and 39 is inserted and arranged in a removable manner.
A shielding part 43 is attached to.

As shown in FIG. 2, the instrumentation well 35 is provided extending over almost the entire length of the upper core mechanism 31, and is, for example, a cylindrical tube with a diameter of 15 mm and a total length of 10 to 15 m. Further, the tip end (lower end in the figure) of the instrumentation well 35 is closed and shielded from the surrounding sodium 27. Furthermore, the upper end of the instrumentation well 35 in the drawing is formed to be open to the outside of the fast breeder reactor 21 .

The detector 41 is inserted and placed at the tip within the instrumentation well 35, and is connected to the thermocouple 45 as shown in FIG.
and a flow meter 47. thermocouple 4
5. Flow meters 47 detect the temperature and flow rate of sodium flowing out from the corresponding fuel assemblies. The aforementioned cable 37 is a thermocouple cable connected to the thermocouple 45, and the cable 39 is a flowmeter cable connected to the flowmeter 47.

The shielding part 43 is for shielding neutrons, gamma rays, etc. in the instrumentation well 35, and has a plurality of shielding elements 49 arranged in a row in the axial direction of the cables 37, 39 with a gap between them. configured. Each shielding element 49 is made of stainless steel and has a spherical shape, and is attached to the cables 37, 39 with the cables 37, 39 passing through it. Element fixing plates 51 and 53 as element fixing members are provided at both upper and lower ends of the shielding element 49 in the figure. The element fixing plates 51 and 53 are fixed to or strongly supported by the cables 37 and 39, thereby integrating the shielding element 49 row with the cables 37 and 39. Furthermore, since the plurality of shielding elements 49 do not have springs or the like interposed between the elements, the cable 3
The shielding portion 43 is easily bent without being pressed in the axial direction of the cables 7 and 39, that is, without being constrained in the axial direction of the cables 37 and 39.

Therefore, when the core instrumentation device 33 malfunctions or during maintenance and inspection, when the detector 41 is pulled out from the instrumentation well 35, even if the instrumentation well 35 has a curved part, the shielding part 43 will not fit into the curved part. It flexibly deforms in response. As a result, an excessive pulling force is not required when extracting the detector 41, and the extracting operation can be carried out smoothly. Thereafter, a new detector or a maintained detector is inserted into the instrumentation well 35. Also during this insertion, the shielding portion 43 deforms in accordance with the curved portion of the instrumentation well 35, so that the insertion work can be facilitated. Therefore, the workability of core instrumentation equipment maintenance and inspection work can be improved.

Furthermore, since the shielding portion 43 can easily conform to the shape of the instrumentation well 35 during insertion/extraction operations, the shielding element 49 is always in close contact with the inner surface of the instrumentation well 35, improving the shielding function. can.

Furthermore, the element fixing plates 51 and 53 are arranged at both ends of the cable 3
7, 39, when the detector 41 is pulled out or inserted, these element fixing plates 51, 5
3 prevents the multiple shielding elements 49 from separating in the axial direction of the cables 37, 39. Some of the shielding elements 49 are connected to the instrumentation well 3
If the cables 37, 39 are separated from the other shielding elements 49 in the axial direction by being caught on the curved portion of may damage the shielding element. In this embodiment, since the arrangement distance of a large number of shielding elements 49 in the cable axis direction is regulated by the element fixing plate, there is no collision of the shielding elements 49.
The integrity of the shielding part 43 can be ensured.

Although the shielding element 49 has been described as having a spherical shape, it may have any shape as long as it has a rounded shape with a curved surface. For example, the shape may be a hemisphere, an ellipsoid (egg shape), a rectangular parallelepiped, or a cube whose corners and sides are curved. Furthermore, the shielding body may be a combination of these, for example, a combination of a spherical shielding element 49 and an ellipsoidal shielding element 49. In these cases as well, since each blocking element 49 has a rounded shape with a curved surface, the shielding part 43 is inserted into the instrumentation well 3 when the detector 41 is pulled out or inserted.
It does not get caught on the curved portion of No. 5, and has the same effect as the above embodiment.

〔Effect of the invention〕

As described above, according to the core instrumentation device for a fast breeder reactor according to the present invention, the shielding section attached to the detector cable is configured with a large number of spherical shielding elements and element fixing members, and each The elements are connected to each other in the axial direction of the above cable.
The element fixing members are arranged at both ends of the plurality of shielding elements and fixed to the cable in a row in the axial direction of the cable without any intervening material. Therefore, when you try to bend a cable with a cutoff element, there is no bending resistance force other than the bending resistance force of the cable itself, so the shielding part conforms to the shape of the curved part of the instrumentation well. The detector can be deformed flexibly and extremely smoothly, making it easy to pull out and insert the detector from the instrumentation well, improving the workability of core instrumentation maintenance work, and The integrity of the shielding part can be ensured when removing and inserting the device. This effect is achieved.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of a part of an embodiment of a core instrumentation device for a fast breeder reactor according to the present invention, and FIG. 2 is a cross-sectional view of a fast breeder reactor to which the embodiment of FIG. 1 is applied. 3 are cross-sectional views showing a fast breeder reactor equipped with a conventional core instrumentation device. 21... Fast breeder reactor, 31... Core upper mechanism,
33...Core instrumentation device, 35...Instrumentation well, 3
7, 39...cable, 41...detector, 45...
...thermocouple, 47...flow meter, 49...shielding element.

Claims (1)

[Claims] 1 An instrumentation well disposed in the upper core mechanism of a fast breeder reactor, a detector housed in the tip of this instrumentation well, and a detector cable extending inside the instrumentation well attached to the instrumentation well. In a core instrumentation device for a fast breeder reactor, the shielding section includes a large number of spherical shielding elements and element fixing members, and each shielding element is connected to the axis of the cable. The cables are arranged in a row in the axial direction of the cables without being constrained, with a gap between them in the direction of the shielding elements, and the element fixing members are located at both ends of the row of shielding elements. A fast breeder reactor core instrumentation device that is fixed to the