JPS5845595A - Reactor - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid metal cooled nuclear reactor, and includes a mechanism for alleviating thermal stress and thermal deformation caused by natural convection that sometimes occurs in an annular gap between a reactor vessel and a shielding plug. Regarding nuclear reactors.

The reactor vessel of a liquid metal cooled nuclear reactor has a reactor core and a primary coolant for cooling the reactor core therein, and therefore requires high reliability regarding its soundness. However, in liquid metal cooled reactors, the temperature of the coolant at the core exit is high, and therefore the temperature of the reactor vessel shell in contact with the core outlet coolant is high, making the design of the reactor vessel extremely difficult as it requires strict high-temperature structural design conditions. It has become a thing. On the other hand, in a nuclear reactor, an annular gap is formed between the reactor vessel shell and a blocking plug mounted on the tower to close the upper open end of the reactor vessel. Natural convection occurs in this gap, resulting in non-uniform temperature distribution in the circumferential direction of the furnace vessel, which causes thermal stress and deformation of the furnace vessel.

As a countermeasure against this problem, measures such as closing the lower end of the annular gap with a jama-no-kana are taken. In order to sufficiently suppress natural convection, it is necessary to make each gap extremely narrow, but there are problems with the dimensional accuracy of the furnace vessel and the shield plug in the can-making structure, as well as the heat of the furnace vessel and the shield plug. It has been difficult to obtain sufficient effects due to differences in expansion and the like. Furthermore, as the size of nuclear reactors increases, the height of the annular gap increases, resulting in the problem that natural convection cannot be sufficiently suppressed even if only the lower end is closed.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to suppress natural convection in the annular gap between the furnace vessel and the Jahei plug, prevent uneven mrti distribution, and prevent thermal deformation. and to provide a highly safe nuclear reactor with low thermal stress.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of the nuclear reactor of the present invention, and FIG. 2 is an enlarged sectional view of the convection prevention bellows part of FIG. 1.A reactor vessel 1 houses a reactor core 2 therein. , supported by the support structure 3. The upper opening of this furnace volume 1%1 is closed by a shield plug 4, and this shield plug 4 is supported by a support base +S installed on the upper part of the support structure 3. A core support structure 6 extending inward in the shape of a collar is provided in the body of the reactor volume a1, and encloses the core 2 therein. Further, an inlet nozzle 7 is provided at the bottom of the furnace vessel 1, and an outlet nozzle 8 is provided at the side of the barrel. A cover gas space 10 is formed between the coolant liquid level 9 and the shielding plug 4. An annular gap 11 is formed between the furnace vessel 1 and the shielding plug 4. A plurality of convection prevention beads 20 described below are attached in the height direction of this annular gap 11.

As shown in Fig. 2, the bead 2 is divided into several parts in the circumferential direction.
0 is set. One end of this pair 20 is fixed to the shield plug 4 with a fixture 21, and the other end is supported movably in the axial direction by a support plate 23 fixed to the shield plug 4 with a fixture 22. has been done. The free height of the beads 20 is set slightly larger than the maximum gap width between the furnace vessel 1 and the shielding plug 4, and the top of the beads 20 is always lightly pressed against the inner wall of the furnace vessel 1. Install it in the same position.

In the reactor configured as described above, even if the width of the gap between the reactor vessel l and the shield plug 4 fluctuates in the circumferential direction due to the thermal expansion difference or dimensional difference during operation, the bead 20 remains in the circumferential direction. Since it is a split structure, the pair 20 of the contact part partially moves in the height direction, as shown by the broken line in Fig. 182.
Radial displacements can be absorbed, and the bellows 20 will always be in contact with the furnace vessel 1. Therefore, the natural convection of the cover gas in the annular gap 8 is blocked by the pears 20 and cannot develop, and the uneven temperature distribution in the furnace vessel and the cooling plug caused by the natural convection is sufficiently alleviated.

As explained above, according to the present invention, natural convection occurring in the gap between the furnace vessel and the shield plug can be suppressed, and the large temperature distribution and thermal stress in the circumferential direction of the furnace vessel and the shield plug caused by natural convection can be suppressed. This makes it possible to alleviate thermal deformation and obtain a highly reliable nuclear reactor. Furthermore, since natural convection is suppressed, it also has the effect of restricting the adhesion of coolant vapor that migrates to the gap due to cover gas convection.

[Brief explanation of drawings]

@Figure 1 is a vertical cross-sectional view of a nuclear reactor according to an embodiment of the present invention, @
FIG. 2 is a longitudinal cross-sectional view of the convection prevention pair of FIG. 1. l...Reactor vessel, 2...Reactor core, 4...Shiyahei plug, 11...Annular gap portion. 20...peas. (7317) Agent Patent Attorney Noriyuki Chika (and 1 others)
Figure 1 Figure 2 Figure 2 501-

Claims (1)

[Scope of Claims] A fast breeder type nuclear reactor that has a nuclear reactor core, a reactor vessel that houses the reactor core and is open at the top, and a shield plug that closes the opening of the reactor vessel. , one end is fixed to the outer periphery of the shield plug in the gap formed between the reactor vessel and the shield plug, and the other end is fixed to the shield plug so as to be movable in the axial direction by a support plate. 1. A nuclear reactor characterized in that a convection prevention bead with its top part in contact with the wall of the reactor vessel is attached to the annular gap. (2) The nuclear reactor according to claim 1, characterized in that it has the base-like circumferentially divided structure.