JPH05119175A - Fast reactor - Google Patents

Abstract

PURPOSE:To lover a leakage value of a coolant by arranging upper and lower sealing mechanisms provided at a joint between upper and lower parts of an intermediate heat exchanger and an inner cylinder and a decompression mechanism to relax conditions of intensity working on a seal bellows. CONSTITUTION:A lover seal bellows 18 is compressed by the weight of an intermediate heat exchanger 9 so that a lower plate 19 and a lower bellows base 20 are welded under pressure to form a lower sealing mechanism 21. At the same time, an upper sealing mechanism 22 is welded under pressure and a lower plate 23 and an upper bellows base 24 are welded under pressure to form an upper sealing mechanism 25. A pressure reducing mechanism 26 comprising a lower tiny hole 27 and an upper tiny hole 29 is added near the sealing mechanism 21. With an electromagnetic pump 7, a primary sodium 6 is pressurized by suction with the heat exchanger 9 to be introduced to the bottom of a reactor core 2 so that a pressure works on the outside of the lower seal bellows 18. The sodium 6 flows toward the upper tiny hole 29 from the lower tiny hole 27 to be returned to an outlet plenum of a heat exchanger tube 11 of the heat exchanger 9. The sodium 6 flowing into the upper part of the inner cylinder 4 is sealed up with the upper sealing mechanism 25 and returned to the suction side of the electromagnetic pump 7 thereby reducing a pressure difference working on the lover sealing mechanism 21 and the upper sealing mechanism 25 significantly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fast reactor which is compact and does not require refueling for a long period of time, and more particularly to a fast reactor having a removable intermediate heat exchanger.

[0002]

2. Description of the Related Art A conventional nuclear reactor structure is shown in FIGS.
Note that FIG. 4 is a cross-sectional view taken along the line YY of FIG. This reactor has a core 2 in which a nuclear fuel is loaded in the center of a reactor vessel 1.
It is composed of A reflector 3 is provided so as to surround the reactor core 2. The reflector 3 is moved up and down by a reflector driving mechanism (not shown) installed on the upper part of the reactor vessel 1. Further, an inner cylinder 4 and a shield 5 are installed outside the reflector 3. In this reactor vessel 1, a core 2
The primary sodium 6 for cooling is contained. In the nuclear reactor, by gradually moving the reflector 3 that surrounds a part of the core 2, the unburned core 2 facing this reflector is irradiated with neutrons and burned little by little over a long period of 10 years or more. Can continue to burn. Primary sodium 6 which is a reactor coolant is sucked and pressurized by an electromagnetic pump 7 to cool the core 2, and then a decay heat removal coil 8
Is cooled by. The primary sodium 6 is further cooled by the intermediate heat exchanger 9, passes through the inside of the shield 5, and flows into the lower portion of the core 2 through the inflow holes 31 formed in the support structure 30 that supports the core 2. .. The primary sodium 6 is guided to the core 2 again through the outflow holes 32 formed in the support structure 30.
The intermediate heat exchanger 9 is composed of a plurality of heat transfer tubes 11 through which the primary sodium 6 flows and an outer cylinder 12 and an inner cylinder 13 for forming a circulation portion of the secondary coolant 10. For this reason, the secondary coolant 10 is guided through the coolant inlet 33 to the flow section including the outer cylinder 12 and the inner cylinder 13. The secondary coolant 10 cools the outside of the heat transfer tube 11 and flows out from the coolant outlet 34. still,
The secondary coolant 10 is sealed by the coolant seal portion 35. The intermediate heat exchanger 9 has a structure that can be taken out from the reactor vessel 1 in consideration of maintenance and inspection. Therefore, on the bellows pedestal 14 fixed to the side surface of the inner cylinder 4,
The lower plate 16 of the seal bellows 15 installed at the lower end of the intermediate heat exchanger 9 is placed. The seal bellows 15 is compressed by the weight of the intermediate heat exchanger 9, and the lower plate 16 fixed to the lower end of the seal bellows 14 and the bellows pedestal 14 are crimped. By this pressure bonding, the high temperature primary sodium 6 flowing out from the core 2 and the low temperature sodium 6 flowing out from the intermediate heat exchanger 9 are sealed.

[0003]

The lower plate 16 of the seal bellows 15 provided in the lower portion of the intermediate heat exchanger 9 and the bellows pedestal 14 provided on the side surface of the inner cylinder 4 are pressure-bonded to each other, so that the primary sodium 6 is removed. Partitioned. Therefore, the high pressure primary sodium 6 on the discharge side of the electromagnetic pump 7 fixed to the lower portion of the intermediate heat exchanger 9 directly contacts the seal bellows 15.
On the other hand, low pressure primary sodium 6 from the core 2 flows into the seal bellows 15. For this reason, a high pressure difference acts on the seal bellows 15, and the seal bellows 15 is subjected to severe strength conditions. Further, this high pressure difference acts on the seal portion by pressing the lower plate 16 of the seal bellows 15 and the bellows base 14 together. Therefore, the amount of primary sodium 6 leaking from the seal portion increases. That is, since the low temperature coolant is mixed in the high temperature coolant, thermal fatigue may occur in the liquid contact portion of the coolant.

The present invention has been made in consideration of the above points, and is a fast reactor capable of relieving the strength condition acting on the seal bellows and reducing the amount of coolant leakage from the seal portion to greatly reduce thermal fatigue. Is intended to provide.

[0005]

In order to achieve the above object, in the present invention, a reactor vessel containing a primary coolant, a reactor core in the reactor vessel, which is composed of nuclear fuel, An inner cylinder arranged concentrically with the core and arranged on the outer side thereof, a reflector moving vertically in an annular space between the inner cylinder and the core, and arranged in an annular space between the inner cylinder and the reactor vessel. A shield, an intermediate heat exchanger installed in the annular space above the shield and removable from the reactor vessel, and a decay heat removal coil installed on top of the intermediate heat exchanger, An electromagnetic pump installed in the lower part of the intermediate heat exchanger, a lower sealing mechanism provided in a joint part between the lower part of the intermediate heat exchanger and the inner cylinder, and a joint part between the upper part of the intermediate heat exchanger and the inner cylinder. Upper sealing mechanism provided on the bottom of the intermediate heat exchanger. It consists of a pressure reducing mechanism provided in fine the lower seal mechanism provides a fast reactor according to claim.

[0006]

With this structure, the intermediate heat exchanger is installed in the inner cylinder of the reactor vessel, and the weight of the intermediate heat exchanger causes the intermediate heat exchanger to be installed at the joint between the lower part of the intermediate heat exchanger and the inner cylinder. A lower sealing mechanism is formed. Further, an upper sealing mechanism provided at the joint between the upper part of the intermediate heat exchanger and the inner cylinder is formed. Further, the pressure reducing mechanism provided near the lower sealing mechanism works. As a result, the strength condition that acts on the seal bellows can be relaxed, and the amount of coolant leaking from the seal portion can be reduced to significantly reduce thermal fatigue.

[0007]

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

FIG. 1 is a vertical sectional view showing an embodiment of a fast reactor according to the present invention. Note that, in FIG. 1, the same parts as those in FIG. FIG. 2 shows a partially enlarged view of the X portion of FIG. An intermediate heat exchanger 9 removable from the reactor vessel 1 is installed in an annular space 17 between the reactor vessel 1 and the inner cylinder 4. Lower plate 19 of the lower seal bellows 18 fixed to the lower part of the intermediate heat exchanger 9
Is placed on the lower bellows pedestal 20 attached to the side surface of the inner cylinder 4. The lower seal bellows 18 is compressed by the weight of the intermediate heat exchanger 9, and the lower plate 19 fixed to the lower end of the lower seal bellows 18 and the lower bellows pedestal 20 are crimped to form a lower seal mechanism 21. At the same time, the lower plate 23 of the upper seal bellows 22 fixed to the upper portion of the intermediate heat exchanger 9 is placed on the upper seal bellows pedestal 24 attached to the upper end of the inner cylinder 4. The upper seal bellows 22 is compressed by the weight of the intermediate heat exchanger 9, and the lower plate 23 fixed to the lower end of the upper seal bellows 22 and the upper bellows pedestal 24 are pressure-bonded to each other to form the upper seal mechanism 25. The lower seal mechanism 21 has a pressure reducing mechanism 26
Is provided. The pressure reducing mechanism 26 is composed of a lower small hole 27 provided at the lower end of the lower seal bellows 18. Further, as a pressure reducing mechanism, a heat transfer tube of the intermediate heat exchanger 9 is used.
An upper small hole 29 is formed on the side surface of the outlet plenum 28 of 11.

Next, the operation of this embodiment having such a configuration will be described. The lower seal bellows 18 is compressed by the weight of the intermediate heat exchanger 9,
Lower plate 19 and lower bellows pedestal 20 attached to the side of the inner cylinder 4
Are pressed to form the lower sealing mechanism 21. At the same time, the upper seal bellows 22 is crimped,
22 Lower plate 23 and upper bellows pedestal mounted on top of inner cylinder 4
24 is crimped to form the upper sealing mechanism 25. In addition, a pressure reducing mechanism 26 including a lower small hole 27 and an upper small hole 29 is added near the lower seal mechanism 21. The electromagnetic pump 7 sucks and pressurizes the primary sodium 6 from the intermediate heat exchanger 9 and guides it to the lower portion of the core 2. Therefore, the pressure of the pressurized primary sodium 6 acts on the outside of the lower seal bellows 18.
By the way, the small hole above the lower small hole 27 forming the pressure reducing mechanism 26
The high pressure primary sodium 6 flows toward 29 and is returned to the outlet plenum 28 of the heat transfer tube 11 of the intermediate heat exchanger 9.
In addition, by the upper seal mechanism 25, it flows into the upper part of the inner cylinder 1.
The next sodium 6 stream is blocked. Primary sodium 6
Since the flow of is returned to the suction side of the electromagnetic pump 7 by the pressure reducing mechanism 26, the pressure difference acting on the lower sealing mechanism 21 and the upper sealing mechanism 25 is greatly reduced.

As described above, according to this embodiment, since the pressure difference acting on the lower seal mechanism 21 and the upper seal mechanism 25 is reduced, the strength conditions of the lower seal bellows 18 and the upper seal bellows 22 are greatly relaxed. To be done. Further, the pressure difference acting on the lower seal mechanism 21 and the upper seal mechanism 25 is reduced, the leakage amount of the primary sodium 6 through the seal portion is reduced, and the thermal fatigue can be greatly reduced.

[0011]

As described above, according to the fast reactor of the present invention, the strength condition acting on the seal bellows is relaxed, and the leakage amount of the coolant from the seal portion is reduced to greatly reduce the thermal fatigue. Can be planned.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a fast reactor according to the present invention.

FIG. 2 is a partially enlarged view showing an X portion of FIG. 1 in an enlarged manner.

FIG. 3 is a vertical sectional view showing a conventional fast reactor.

FIG. 4 is a sectional view taken along the line YY of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reactor vessel 2 ... Core 3 ... Reflector 4 ... Inner cylinder 5 ... Shield 6 ... Primary sodium 7 ... Electromagnetic pump 9 ... Intermediate heat exchanger 21 ... Lower sealing mechanism 25 ... Upper sealing mechanism 26 ... Decompression mechanism 27 … Lower hole 29… Upper hole

Claims (1)

[Claims] 1. A reactor vessel containing a primary coolant, and a reactor core in the reactor vessel, which is composed of nuclear fuel,
An inner cylinder arranged concentrically with the core and arranged on the outer side thereof, a reflector moving vertically in an annular space between the inner cylinder and the core, and arranged in an annular space between the inner cylinder and the reactor vessel. A shield, an intermediate heat exchanger installed in the annular space above the shield and removable from the reactor vessel, and a decay heat removal coil installed on top of the intermediate heat exchanger, An electromagnetic pump installed in the lower part of the intermediate heat exchanger, a lower sealing mechanism provided in a joint part between the lower part of the intermediate heat exchanger and the inner cylinder, and a joint part between the upper part of the intermediate heat exchanger and the inner cylinder. A fast reactor, comprising: an upper sealing mechanism provided in a lower part of the intermediate heat exchanger; and a pressure reducing mechanism provided in the lower sealing mechanism of the intermediate heat exchanger.