JPH0434392A - Tank type fast breeder - Google Patents

Abstract

PURPOSE:To control lateral bending vibrations of a reactor core vessel to ensure the easiness of control rods insertion when there is an earthquake by applying a fluid vibration control effect between the reactor core vessel and a thin cylinder part of an upper partition in the case where acceleration is applied horizontally when the earthquake occurs. CONSTITUTION:A reactor core 2 supported by the use of a core support structure 6, a main circulation pump 3 and an intermediate heat exchanger 4 set through a roof slab 12 are arranged in a nuclear vessel end plate part 1a and liquid sodium is stored up to the liquid level indicated on the righthand figure. An upper partition 13 and a lower partition 10 for adiabatically separating the liquid sodium into low temperature sodium 7 and high temperature sodium 8 are formed and the upper partition 13 is shaped in a core vessel 5 and a concentric circular thin cylinder part 13a. Since the cylinder part 13 is formed almost up to the same height as the core vessel 5 through a narrow gap at the outside of the core vessel 5, its end is connected to the core internal support structure 6.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to a tank-type fast breeder reactor that uses liquid metal as a coolant, and particularly relates to a tank-type fast breeder reactor that has a core allocation function. Regarding furnaces.

(Prior Art) Fast breeder reactors that use liquid metal sodium as a coolant can be broadly classified into tank type and loop type depending on the reactor type. Among these, the tank-type fast breeder reactor is one in which a reactor core 2, a main circulation pump 3, and an intermediate heat exchanger 4 are installed in a reactor vessel 1, as shown in FIG. 4, for example.

In the tank-type fast breeder reactor shown in FIG. 4, a core 2 in which a large number of fuel assemblies are loaded in a core tank 5 is supported by a core support structure 6 connected to a head plate 1a at the bottom of the reactor vessel 1. has been done. Furthermore, the reactor vessel is provided with a conical upper partition wall 9 and a toroidal lower partition wall 10 that adiabatically separate the liquid metal sodium into low temperature sodium 7 and high temperature sodium 8. The fuel is pumped by the pump 3 to a pressure plenum 11 provided at the bottom of the core 2, circulates inside the core 2 from the bottom to the top, and is heated to a high temperature. On the other hand, the high-temperature sodium 8 exchanges heat with the secondary coolant in the intermediate heat exchanger 4, becomes low-temperature sodium 7 again, is sucked into the main circulation pump 3, and circulates within the reactor vessel 1. Note that the upper end of the reactor vessel 1 is a roof slab 12.
is blocked by.

(Problems to be Solved by the Invention) In the tank-type fast breeder reactor configured as described above, the core tank 5 is a thin-walled cylindrical structure supported by the core support structure 6 from the lower end plate 1a of the reactor vessel 1. Therefore, when horizontal acceleration due to an earthquake is applied, there is a risk that control rod insertion may be hindered by localized lateral bending vibrations. Conventionally,
In order to suppress local lateral bending vibrations during earthquakes and ensure control rod insertability, the core barrel 5 must be made thicker to increase its rigidity, or the lateral Countermeasures such as providing a steady rest structure for suppressing bending vibrations may be taken, but these are undesirable because they cause an increase in the amount of material.

The present invention has been made in response to these problems, and aims to provide a tank-type fast breeder reactor that does not cause large lateral bending displacement in the core barrel even when a large seismic load is applied, without increasing the amount of material. purpose.

[Configuration of the Invention (Means for Solving the Problems) In other words, the tank-type fast breeder reactor of the present invention has a reactor core in which a part of the upper partition wall formed in the reactor vessel is supported by a core support structure. It is characterized by a thin cylinder that stands upright from the core support structure concentrically with a gap around the tank.

(Function) In the tank-type fast breeder reactor of the present invention, even when acceleration is applied in the horizontal direction due to an earthquake, the sodium flow structure between the thin-walled cylinder serving as the upper partition provided around the core tank and the core tank remains stable. The vibration effect suppresses lateral bending vibration.

In particular, since the sodium between the core barrel and the thin-walled cylinder is sealed from below by the core support structure, the only escape route for the sodium during an earthquake is above the core barrel, and the fluid vibration effect is significant.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

1 to 3 show an embodiment of the tank-type fast breeder reactor of the present invention, and the same parts as in FIG. 4 are denoted by the same reference numerals. In FIG. 1, there is a reactor vessel mirror plate 1 inside the reactor vessel 1, almost the same as in the case shown in FIG.
In a, a core 2 supported by a core support structure 6, a main circulation pump 3 and an intermediate heat exchanger 4 provided through a roof slab 12 are arranged, and liquid metal sodium is also used as a liquid as shown in the figure. It has been stored up to a certain level. An upper partition wall 13 and a lower partition wall 10 are formed to adiabatically separate this liquid sodium into low-temperature sodium 7 and high-temperature sodium 8. The toroidal lower partition wall 10 is the same as the conventional example, but the upper partition wall 13 is Unlike the conventional upper partition wall 9 shown in FIG. 4, it is formed in a thin cylindrical portion 13a concentric with the core barrel 5 around the core barrel 5. This thin cylindrical portion 13a is formed at approximately the same height as the core barrel 5 through a narrow gap outside the core barrel 5, and its end is connected to the core support structure 6.

In the tank-type fast breeder reactor configured as described above, when acceleration due to an earthquake is applied in the horizontal direction, the core tank The lateral bending vibration is suppressed by the fluid vibration effect of the sodium in the gap between the cylindrical portion 5 and the thin cylindrical portion 13a. In particular, since the sodium in the gap between the core barrel 5 and the thin cylindrical portion 13a is sealed from below by the core support structure 6, and the height of the core barrel 5 is approximately 4 m, the vibration damping effect of the fluid is is quite large.

FIG. 3 shows another embodiment, in which a convex portion is formed on the upper gap side of the thin cylindrical portion 15a of the core barrel 14 and the upper partition wall 15, respectively.

By forming a fluid labyrinth in this manner, the upward escape path for sodium between the caps is further narrowed, and the damping effect of the fluid is further strengthened.

[Effects of the Invention] As is clear from the above description, according to the present invention, even if acceleration is applied in the horizontal direction during an earthquake, the fluid vibration between the core barrel and the thin cylindrical portion of the upper bulkhead is prevented. As a result, the lateral bending vibration of the reactor core barrel is suppressed, ensuring ease of insertion of control rods in the event of an earthquake.

Furthermore, the present invention utilizes a modified version of the existing upper partition wall,
There is no need to increase the thickness of the core barrel or install a new core barrel steady rest structure, and an increase in material volume can be prevented.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG.
FIG. 3 is an enlarged sectional view of the main part showing another embodiment of the present invention, and FIG. 4 is an enlarged sectional view of a conventional tank-type fast breeder reactor. FIG. 1... Reactor vessel, 1a... End plate, 2... Reactor core,
3... Main circulation pump, 4... Intermediate heat exchanger, 5.1
4... Core barrel, 6... Core support structure, 7... Low temperature sodium, 8... High temperature sodium, 9.13.1
5... Upper bulkhead, 10... Lower bulkhead, 11... Pressure blemish, 13a, 15a... Thin cylindrical portion of upper bulkhead FIG. 4

Claims (1)

[Claims] (1) The upper part accommodates the reactor core supported by the lower head plate of the reactor vessel via the core support structure and the liquid metal coolant in the reactor vessel, and adiabatically separates the liquid metal coolant into a high temperature side and a low temperature side. In a tank-type fast breeder reactor equipped with a partition wall and a lower partition wall, the upper partition wall has a thin cylindrical portion that stands upright from the core support structure in a concentric circle with a gap provided outside the core tank constituting the reactor core. A tank-type fast breeder reactor characterized by: