JPH0334834B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention is directed to absorbing displacement due to thermal expansion of a nuclear reactor vessel housing a reactor core cooled by circulation of liquid metal and related equipment therein. The present invention also relates to an earthquake-resistant support device for a nuclear reactor vessel that can safely support the reactor vessel during an earthquake.

[Technical background of the invention and its problems]

As is well known, in a nuclear reactor cooled by liquid metal, the reactor core 1, core support structure 2, etc. are housed in a reactor vessel 3, as shown in FIG. The upper flange 4 is placed on and supported by a pedestal 5 extending from the wall of the reactor building.

When the volume of a nuclear reactor vessel increases as power generation capacity increases, its natural vibration frequency decreases, making its seismic design extremely difficult. For example, if the structure is rigid, the horizontal seismic force for seismic design is 1000.
On the other hand, if the structure is not rigid and its natural vibration frequency is small, the value will be
5,000 to 6,000 ga, which is an extremely difficult design condition. For this purpose, in the conventional structure, for example, as shown in FIG. 5, an earthquake-resistant support device equipped with oil dampers 6 and the like is provided at several radial locations around the lower outer periphery of the reactor vessel 3, to reduce the natural frequency of the reactor vessel 3. Measures are being taken to reduce the seismic force acting on the reactor vessel 3 by increasing the earthquake force.

However, when a so-called seismic vibration isolator such as a mechanical snubber or an oil snubber is used as an earthquake-resistant support device, the following problems occur.

(1) As reactor vessels become larger, large-capacity snares that can withstand large earthquake reaction forces are required.

(2) A snubber that can cope with the increase in thermal displacement due to the increase in the size of the reactor vessel is required, which complicates the structure.

(3) It is necessary to perform maintenance and repair work such as inspecting moving parts and changing oil under high radiation levels.

[Purpose of the invention]

The present invention was made to solve the above problems, and its purpose is to have a simple structure that can withstand large earthquake reaction forces, absorb thermal displacement due to thermal expansion of the reactor vessel, and be able to operate under high radiation conditions. An object of the present invention is to provide an earthquake-resistant support device for a nuclear reactor vessel that can reduce maintenance and inspection work in a nuclear reactor vessel.

[Summary of the invention]

In order to achieve the above object, the present invention provides a radial key provided protruding from the lower outer periphery of a reactor vessel whose upper flange is placed and supported on a pedestal extending from the wall of the reactor building, and the radial key. a slit provided along the vertical direction on the protruding end surface of the radial key; and a radial key receiver attached to the inner surface of a guard vessel that faces both sides of the radial key at a predetermined interval and covers the outer periphery of the reactor vessel. It is equipped with the following.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 is a sectional view of a tank-type fast breeder reactor showing one embodiment of the present invention. The reactor vessel 3 of this tank-type fast breeder reactor is supported by placing its upper flange 4 on a pedestal 5 extending from the reactor building wall via a ring gutter 7. A roof slab 10 consisting of a fixed plug 8 and a rotating plug 9 is installed at the upper end opening of the reactor vessel 3, and closes the upper end opening of the reactor vessel 3.
The roof slab 10 is equipped with an intermediate heat exchanger 11, a circulation pump 12, a core upper air structure 13, a fuel exchanger 14, etc.
2 are alternately mounted along the circumferential direction of the roof slab 10. The core support structure 2 is suspended from the roof slab 10 via a cylindrical suspension shell 15, and accommodates and supports the core 1 made up of a large number of fuel assemblies. In addition, reactor vessel 3
The interior is partitioned into an upper high-temperature Na section (hot pool) 17 and a lower low-temperature Na section (cold pool) 18 by a partition wall 16 connected to the outer wall of the suspension shell 15 and the inner wall of the reactor vessel 3. reactor vessel 3
The coolant (liquid sodium) in the cold pool 18 is normally around 350℃,
The fuel is sucked in through the inflow holes 19 of No. 2 and sent into the high-pressure plenum structure 20 below the reactor core 1. The coolant fed into the high-pressure plenum structure 20 passes through the core 1 and rises.
The temperature rises to about 0.degree. C. and flows inside the hanging shell 15 to the hot pool 17. The coolant flowing out into the hot pool 17 flows through the flow hole 21 formed in the hanging body 15.
enters the inlet hole 22 of the intermediate heat exchanger 11 through the
After being cooled to about 350° C. by exchanging heat with the secondary coolant, it is returned to the cold pool 18 through the outlet nozzle 23.

Furthermore, an earthquake-resistant support device 10 according to the present invention is provided between the lower outer periphery of the reactor vessel 3 and the guard vessel 24.
0 is set. As shown in FIG. 2, a plurality of seismic support devices 100 are provided at equal pitches along the circumferential direction of the reactor vessel 3, and have a radial key structure. That is, this seismic support device 100
is the reactor vessel 3 as shown in Figures 3 and 4.
Radial key 1 protruding from the lower outer periphery of
01 and a radial key receiver 102 facing both sides of this radial key 101, this radial key 102 is attached to a guard vessel 24 that covers the outer periphery of the reactor vessel. Further, a plurality of slits 103 are provided on the protruding end surface of the radial key 101 along the vertical direction. Then, radial key 101 and radial key receiver 1
02 are L-shaped spacers 104, 104.
is inserted, and the side surface 101a of the radial key 101
The width g is maintained for a predetermined period. Note that the spacer 104 is fixed to the upper surface of the radial key receiver 102 with a mounting bolt 105.

Next, the effect will be explained. The reactor vessel 3 reaches a high temperature during operation, and thermally expands by several tens of millimeters in both the vertical and radial directions of the reactor vessel. If this thermal expansion is restricted, a large amount of stress will be generated in the reactor vessel 3, so the seismic support device needs to allow the reactor vessel 3 to thermally expand freely. In the seismic support device 100 according to the present invention, since the radial key 101 and the radial key receiver 102 are engaged with each other with a width g for a predetermined period, the vertical and radial thermal expansion of the reactor vessel 3 is prevented. Since it is not restrained, no thermal expansion reaction force is generated in the reactor vessel 3. Therefore, an increase in the amount of thermal displacement due to an increase in the size of the reactor vessel 3 can be sufficiently absorbed.

Next, the action during an earthquake will be explained with reference to FIG. When a horizontal seismic force acts in the direction shown by the arrow in FIG. 2 due to an earthquake, the entire reactor vessel 3 first moves in the 270° direction by the width g between the radial key 101 and the radial key receiver 102.
Radial keys 101a, 1 in 0° and 180° directions
01m and the radial key receivers 102a and 102m collide with each other, restraining the horizontal movement of the reactor vessel 3. As a result, the radial keys 101a, 101
When a reaction force is generated between m and the radial key receiver 102a, 102m, and the amount of displacement of the radial key due to the reaction force exceeds g/cosΔθ, the next radial key 101b, 101l and the radial key receiver 10
2b, 102l start hitting. From then on, the earthquake load will be distributed in order according to the mounting angle of the radial key. With conventional solid radial keys, the rigidity of the keys is extremely high, so it takes a huge force to displace the first key hit by g/cos Δθ, resulting in the effect of supporting the earthquake reaction force with a small number of keys. Ta.
On the other hand, in the radial key 101 provided with the slit 103 according to the present invention, the slit 103 reduces the rigidity of the radial key, and since the radial key can be displaced with a small force, the number of keys that share the earthquake load increases, and the number of keys that share the earthquake load increases. The seismic reaction force that the radial key is responsible for can be significantly reduced.

〔Effect of the invention〕

As explained above, according to the present invention, the seismic reaction force that should be shared by the radial key is flattened in order to disperse and support the reaction force during an earthquake without restricting the deformation of the reactor vessel due to thermal expansion. This makes it possible to significantly reduce the stress on the radial key part. Also,
The local stress generated in the reactor vessel where the radial key is installed is also significantly reduced, increasing the design margin for structural strength. It was necessary to take measures such as reducing the gap width between the key holder and the key receiver as much as possible and increasing the number of keys, but according to the present invention, such measures as described above are no longer necessary, and the installation work becomes easier. The amount of material can be reduced. Furthermore, since the structure is entirely mechanical and static, it is highly reliable and has fewer causes of failure. Therefore, there is no need for regular maintenance work, and only simple inspection work is required, which has great effects such as extremely short work times under radiation.

[Brief explanation of the drawing]

Figures 1 to 4 are diagrams showing an embodiment of the present invention, in which Figure 1 is a cross-sectional view of a tank-type fast breeder reactor, and Figure 2 is a horizontal cross-section of the reactor vessel showing the installation state of the seismic support device. Figure 3 is an enlarged sectional view showing part A in Figure 2, Figure 4 is a view taken along the - line in Figure 3, and Figure 5 is an enlarged sectional view showing part A in Figure 2.
The figure is a sectional view of a conventional fast breeder reactor. DESCRIPTION OF SYMBOLS 1...Reactor core, 3...Reactor vessel, 100...Seismic support device, 101...Radial key, 102...
...Radial key receiver, 103...slit.

Claims (1)

[Claims] 1. A radial key provided protruding from the outer periphery of the lower part of the reactor vessel whose upper part is placed and supported on a pedestal extending from the reactor building wall, and a radial key provided along the vertical direction on the protruding end surface of this radial key. and a radial key receiver that faces both sides of the radial key at a predetermined distance and is attached to the inner surface of a guard vessel that covers the outer periphery of the reactor vessel. Seismic support equipment.