JPS6249953B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear reactor vessel in which the temperature of the vessel wall in the cover gas region above the coolant liquid level of a liquid metal cooled nuclear reactor is made uniform.

In a liquid metal cooled nuclear reactor, a reactor vessel body 1 containing a reactor core and coolant is usually installed on a pedestal 2 as shown in FIG. (Usually a fixed plug that does not have a rotating function) is fitted and assembled. For this reason, it is necessary to provide a gap of a certain size or more between the furnace vessel body 1 and the outer circumferential surface of the shrinkage plug 51, which is determined by manufacturing tolerances and assembly requirements between the two. Normally, this size is on the order of several tens of millimeters, which causes the following problems.

(1) At this annular gap (part A in Figure 1), the furnace vessel body 1
The cover gas inside generates a circumferential flow, which causes the furnace vessel body 1 and the outer circumferential surface 51 of the shrink plug to
The wall temperature shows different values in the circumferential direction. According to the knowledge obtained so far, this temperature difference is 40~
It is estimated that it will be about the size of 50 degrees Celsius. If a temperature difference occurs in the circumferential direction of the reactor vessel body 1, thermal deformation causes bending with respect to the central axis, which may reduce the ability to insert control rods into the reactor core when shutting down the reactor. Therefore, in order to restrain this bending, the furnace vessel body 1 is generally designed to be fixed in the radial direction at an appropriate position at the bottom, but even so, if such a circumferential temperature difference occurs, the wall of the furnace vessel body 1 There is a risk of buckling due to compressive force on the colder side.

Since the thermal stress caused by the temperature distribution in the upper circumferential direction is also added, it becomes extremely difficult to design the strength of the upper part of the reactor vessel.

(2) Neutrons leak from the core through this annular gap, so in order to keep the radiation intensity above the shield plugs 5 and 6 below the specified value, install the necessary additional shields above. Otherwise, it is necessary to insert a shield into this gap.

(3) Because thermal plugs are required for radiation radiation, heat radiation, equipment mounting functions, etc., their thermal inertia is inevitably large as they are heavy devices. Since the reactor coolant temperature changes transiently during startup, shutdown, scram, and other transient states of the reactor, the wall temperature of the reactor vessel body 1 also changes accordingly. At this time, if the inside of the reactor vessel body 1 is facing the heat sink plug with large thermal inertia, the temperature on the heat sink side does not change rapidly, so this acts as a low-temperature heat sink, and the reactor vessel body The temperature gradient in the axial direction on the wall surface of the container body 1 increases compared to when the container body 1 is a single unit. For this reason, the thermal stress of the furnace vessel body 1 increases, making it extremely difficult to design the strength of the upper part of the furnace vessel body.

Due to the various problems mentioned above, regarding the structure of the fitting part of the upper part of the reactor vessel body and the shield plug, it is necessary to reduce the gap between them and suppress neutron streaming. It is desirable to have some degree of insulation effect between them. To this end, it may be possible to insert a heat insulator into the annular gap shown in part A in Figure 1, but this alone would still require a certain amount of gap due to constraints such as manufacturing tolerances for both shells and clearance for assembly. However, this does not fundamentally solve the problem and requires special countermeasures.

The present invention has been made to meet the above-mentioned needs, and solves the above-mentioned problems by inserting a heat insulator in consideration of the shape of the outer peripheral surface of the shield plug and the upper part of the furnace vessel body. The purpose is to provide a nuclear reactor vessel with

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows the entire conventional nuclear reactor vessel, and FIG. 2 shows the main parts of the present invention. That is, the reactor vessel main body 1 contains a coolant 3, a fixed hard plug 5 and a rotatable hard plug 6 are installed at the top to serve as a lid, and the inside is usually filled with inert gas such as argon. A cover gas 4 made of gas is sealed.

The upper part of the furnace vessel main body 1 is provided with an inclined surface to form a conical shape, and the conical surface is filled with a heat insulating material 7 such as stainless steel wool, and a stainless steel plate (included in 7) is placed on top of the conical surface. With the insulation support 8,
Attach with bolts, etc. The support 8 has a sector shape as shown in FIG. 3, for example, and is elastic. On the other hand, the lower end of the support 8 is connected to the furnace vessel main body 1
It is fitted into the inside of a stopper 11 provided in the.

A stiff plug outer circumferential surface 51 is installed at a position facing the conical surface formed by the support 8. In the figure, both bodies are conical, but it is also possible to make only one of them conical, depending on the design. Since at least one side of this surface is conical, the necessary work space is secured when installing the insulation plug 5, and the manufacturing tolerance of the two cylinders is such that the insulation body 7 and While absorbing the heat due to the elasticity of the heat insulator support 8 itself, both bodies can be brought into a light contact state.

As explained above, the reactor vessel of the present invention can be in a light contact state with almost no clearance between the gap and the outer shell of the thin plug. This can prevent the non-uniform situation, and is effective in reducing neutron streaming in item (2) by selecting the material for the heat insulator. Furthermore, since it is possible to limit the heat exchange between the heat exchanger plug and the furnace vessel, it is possible to sufficiently reduce the axial temperature gradient of the furnace vessel during the transient temperature change described in (3). It is possible to provide a nuclear reactor vessel with

In addition, by adopting a conical shape, we were also able to solve the problem of manufacturing tolerances for the furnace vessel body and securing gaps during assembly.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a part of a conventional reactor vessel from the side, FIG. 2 is a vertical cross-sectional view partially showing only the main parts of the reactor vessel according to the present invention, and FIG. It is a perspective view which expands and shows the A section in FIG. 1; Furnace vessel main body, 5; Shiyahei plug (fixed plug), 51; Shiyahei plug outer peripheral surface, 52; Plate, 7; Heat insulating body, 8; Heat insulating body support.

Claims (1)

[Claims] 1. A furnace vessel body, a shield plug that closes the upper opening of the furnace vessel body, a heat insulating body interposed between the outer peripheral surface of the cold plug and the furnace vessel body, and a heat insulating body that supports the heat insulating body. and a flexible support for the heating, and at least one of the contact surfaces between the heat insulator and the furnace vessel body and the contact surface between the heat insulator and the insulation plug is formed into a conical shape. A nuclear reactor vessel featuring: