JPS6330598B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid metal cooled nuclear reactor that prevents liquid coolant from scattering (sloshing) during an earthquake or the like.

As shown in FIG. 1, a cold metal-cooled nuclear reactor has a reactor core 2 installed in a reactor vessel 1, and the reactor core 2 is cooled by a coolant 3.
There is a cover gas space 5 between them, and the coolant 3 has a free liquid level 6.

For this reason, the coolant 3 leaving the core 2 forms a jet at the free liquid level 6 due to its velocity potential, and this jet entrains the cover gas into the coolant 3, causing it to enter the primary cooling system. There were concerns that there was a risk of damage to the primary cooling system equipment and core 2.

Also, the free liquid level 6 of the coolant 3 oscillates during an earthquake,
Since the temperature of the coolant is high, there are disadvantages such as severe thermal shock being applied to the inside of the upper in-furnace mechanism or surrounding structures, and excessive sloshing load being applied to surrounding structures.

Therefore, conventionally, a dip plate 9 of a single plate structure was installed by suspending the entire range below the free liquid level 6 from the shield plug 4 that closes the upper part of the reactor vessel 1 by means of a shell structure 8. This prevents the entrainment of the cover gas and also prevents the liquid level from fluctuating.

By the way, in the above means, the dip plate 9 is a single plate suspended from the lower surface of the shield plug 4 by the shell structure 8 and fixed around it, and is It is installed in a coolant and is exposed to severe thermal stress conditions at steady state. Also, the start-up of the nuclear reactor,
Because they are subjected to thermal cycles due to temperature changes in the coolant due to shutdowns, etc., they are subject to severe creep, fatigue damage, etc.

In addition, the deep plate 9 and the deep plug 4
Since it is suspended from the bottom of the reactor, it cannot be repaired during the life of the reactor, and in order to improve the reliability of the equipment, it is necessary to limit thermal stress to a small level, prevent gas entrainment, and reduce the liquid level during earthquakes. It is desirable to have a structure that is as simple as possible and can sufficiently perform functions such as preventing rocking.

However, as the output of nuclear reactors increases, or when adopting a tank-type reactor type, which is considered as a different concept of reactor type, the diameter of the reactor vessel becomes 10 m or 21 m according to design examples, so this With the dip plate method, extremely large and heavy parts are brought into the reactor vessel, making repairs extremely difficult and increasing the amount of material needed. Moreover, since it is a large-diameter flat plate, a one-piece structure would generate large thermal stress, so a multi-segment structure is required, but due to the large diameter, the number of parts increases considerably and the structure becomes complicated. do.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and is capable of overcoming the above-mentioned drawbacks while sufficiently maintaining the functions of conventional dip plates. is intended to provide.

That is, the present invention is a nuclear reactor characterized in that a plurality of baffles are provided below the free liquid surface of a coolant that cools a reactor core housed in a reactor vessel.

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIG.

FIG. 2 shows only the essential parts of the present invention, and the same parts as those in FIG. 1 are shown as the same parts.

That is, FIG. 2 shows an example in which two ring-shaped buffles 10 and 11 are installed slightly below the liquid level 6 of the coolant 3 on the inner wall surface of the reactor vessel 1.
Note that the ring-shaped buffles 10 and 11 may be attached to the inner wall surface of the container 1 either horizontally or with a slight downward slope.

FIG. 3 shows another embodiment of the present invention, in which the buttfuls 10 and 11 are attached to a cylindrical support member 12 suspended from the upper flange 1a of the reactor vessel 1, and the buttfuls 10 and 11 are cooled. The material 3 is immersed below the free liquid level 6.

Here, in both FIGS. 2 and 3, the width dimension, number of stages, immersion depth below the liquid surface, etc. of the ring-shaped buffle 3 can be arbitrarily determined by design to suit the usage conditions.

However, during an earthquake, the free liquid level swings from the A-B plane 6 to the A'-B' plane 6a as shown in Figure 4, and sloshing develops, generating an excessive impact force. Since the ring-shaped buffle of the invention is located around the free liquid level, the development of this sloshing can be prevented.

Furthermore, regarding the phenomenon of gas entrainment from the free liquid level during normal times without earthquakes, which was a concern in the past, subsequent studies revealed that the velocity potential near the free liquid level is extremely small, and the nuclear reactor shown in Figure 1. It has become clear that this problem can be prevented to a practical degree by setting the height of the outlet nozzle 13 sufficiently away from the free liquid level. On the other hand, in general, when designing a fast reactor, it is necessary to ensure a sufficient l dimension in FIG. 1 for safety reasons in the event of pipe breakage, so the problem of cover gas entrainment is automatically resolved.

The ring-shaped baffle according to the present invention, which combines the above two facts, sufficiently maintains the functions of the conventional dip plate, overcomes the above-mentioned drawbacks, and has an extremely simple structure that increases reliability. It can be said that this is a reactor that prevents sloshing of the reactor coolant liquid level.

As explained above, the present invention prevents the development of sloshing of the coolant liquid level during an earthquake by installing the Batsuful at an appropriate position below the free liquid level of the reactor coolant, thereby preventing excessive shock to peripheral equipment. There is no need to apply any load, and the fluctuation of the liquid level prevents Nu from surrounding equipment.
There is no need to worry about severe thermal shock caused by temperature.

Furthermore, the aforementioned problems encountered with conventional dip plates associated with bringing extremely large diameter and heavy parts into the furnace are also eliminated.

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically showing a part of a conventional nuclear reactor, FIGS. 2 and 3 are sectional views showing only the main parts of each embodiment of the nuclear reactor according to the present invention, and FIG.
The figure is a conceptual diagram showing sloshing of the free liquid level for explaining the effects of the present invention. 1...Reactor vessel, 4...Shiyahei plug, 10,
11...Ring-shaped buttful, 12...Supporting member.

Claims (1)

[Claims] 1. A plurality of stages stacked vertically in the periphery of the reactor vessel directly below the free liquid level of the coolant that cools the reactor core housed in the reactor vessel and above the reactor outlet nozzle. A nuclear reactor characterized by being provided with a horizontal flat ring-shaped buttful. 2. The nuclear reactor according to claim 1, wherein the plurality of ring-shaped baffles are directly attached to an inner wall surface within the reactor vessel. 3. The nuclear reactor according to claim 1, wherein the plurality of stages of buttful plates are provided on a support member that hangs down from the lower surface of a ring-shaped plug.