JPH0498200A - Liquid metal storage tank - Google Patents

Abstract

PURPOSE:To obtain a structure which will not bring buckling at the time of an earthquake by providing a tank main body installed in a pit chamber and a pot part for seal provided on an upper outside surface of it. CONSTITUTION:A tank main body 1 is mounted and fixed on a base seat 3 for a floor part in a pit chamber 2, and an upper end aperture of the chamber 2 is closed with a roof part 4. A circular pot part 6 for seal where liquid metal 5 for seal is filled is provided on an upper outside surface of the main body 1. A partition cylinder 7 is provided immersed at a lower end part at a lower positron in time metal 5 in the pot part 6 and suspended from the underside surface of the roof part 5. A cover gas space 8 in the main body 1 and a pit chamber gas space 9 in the chamber 2 are separated by the cylinder 7, so cover gas in the main body 1 is prohibited from flowing into the chamber 2, and gas in the chamber 2 from flowing into the main body 1. For the liquid metal, liquid metal sodium 10, for example, is contained in the main body 1, and a steam generator 11 is provided immersed in the sodium 10 at a lower part and fixed at the roof part 4 at art upper part. A thinner structure less likely to produce a thermal stress can thus be achieved, and buckling at the time of an earthquake can be prevented.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a liquid metal storage tank used in a fast breeder reactor (hereinafter referred to as fast reactor) plant.

(Prior Art) The main vessel tank of a fast reactor houses therein a reactor core consisting of nuclear fuel for causing a nuclear reaction and a neutron reflector necessary to continue the reaction.

In a loop type fast reactor, the reactor core is located inside the main vessel, or tank.
It houses structures such as piping and partition walls that do not cause large thermal stress, and liquid metal sodium as a coolant that efficiently cools the reactor core. On the other hand, in a tank-type fast reactor, in addition to these, there is also an intermediate heat exchanger (hereinafter referred to as IHX) for transferring thermal energy from primary sodium to secondary sodium, and a reactor core that is a heat source for primary sodium. Equipment such as a primary pump for circulating the flow between the IHXO section and the heat sink, a passage structure for the primary coolant, etc. are housed. This large amount of equipment or the main vessel containing the sodium coolant will increase the thermal output of the reactor;
Alternatively, the larger the number of storage devices, the larger the device tends to become.

On the other hand, by storing as many devices as possible in the tank and omitting the routing of numerous pipes and space, it is possible to simplify the reactor equipment, which leads to a reduction in the cost of the entire reactor facility, resulting in high reliability. , and there is a tendency for proposals to be made that accommodate a large number of devices. That is, a proposal is being considered in which the tank is doubled and devices such as a steam generator and a pump are placed inside the secondary container in the annular portion. In such a case, if you aim for high output, the tank will become even larger. Furthermore, in order to prevent buckling of the tank during an earthquake, the larger the diameter of the tank, the thicker the plate thickness of the tank becomes.

On the other hand, tanks usually have a roof section (also called a roof slab) or a lid structure (also called a shielding plug) at the upper opening; the former is formed in one piece, and the latter is sealed with an O-ring. Sealed and flanged configuration. Both are installed on concrete pedestals that make up the pit chamber, which is a reinforced concrete structure, and these heavy structures are supported. Concrete and sealed structures generally have low operating temperatures, and the upper part of the tank is usually kept at a low temperature near room temperature, taking into account the accessibility of the upper part and the lower operating temperature of electrical components above. Therefore, a temperature gradient occurs above the tank due to a large temperature difference ranging from the sodium temperature of the coolant to near room temperature, and this generates thermal stress. This thermal stress increases as the tank diameter and plate thickness increase. This makes it easy to buckle during an earthquake, and due to the creep temperature, it can cause thermal ratchet when used at a high temperature.

In addition, in the case of a double tank, the steam generator is the primary tank and the secondary tank.
Since it is installed in the annular part between the tanks, if a large-scale leak of water or steam occurs in the heat exchanger tube of the steam generator, the pressure of the cover gas will increase due to the hydrogen gas generated by the reaction of water or steam with sodium. There is a concern that it may rise rapidly and cause buckling of the primary tank.

(Problem to be solved by the invention) In the tank structure used in conventional fast reactors, when the tank becomes large, thermal stress due to the longitudinal temperature gradient of the tank is severe and can cause buckling in the event of an earthquake. .

In addition, in the case of a double-tank fast reactor, there is a problem in that if a large-scale leak of water or steam occurs from the steam generator, the primary vessel may buckle.

The present invention was made to solve the above problems, and it reduces the thermal stress that occurs when the tank becomes large, prevents buckling even in the event of a large-scale earthquake, and reduces the pressure of the cover gas. It is an object of the present invention to provide a storage tank for liquid metal that has excellent structural reliability and soundness and has a structure that can avoid a sudden rise in temperature.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes a tank body installed in a pit chamber, a sealing tub portion provided on an upper outer surface of the tank body, and an upper opening of the pit chamber. A sealing partition tube that is suspended from the lower surface of the roof portion and has a lower end extending into the tub portion, and a sealing liquid metal filled in the tub portion. It is characterized by

(Function) The tank body is kept at a high temperature by liquid metal, and the roof installed above the pit chamber is kept at a low temperature. Since the tank body and the inside of the pit chamber are sealed by the partition tube inside the sealing tub filled with liquid metal, no large thermal stress is generated on the tank body wall. If hydrogen gas is generated within the tank body, it can be released into the pit chamber through bubbling from the sealing tub, so the integrity of the tank can be maintained even if the pressure inside the tank body suddenly increases.

(Example) A first example of a liquid storage tank according to the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 1 indicates a tank body used, for example, as a main vessel of a fast breeder reactor. This tank body 1 is mounted and fixed in a pit chamber 2 with a pedestal 3 as a floor. The upper end opening of the pit chamber 2 is closed by a roof portion 4. A sealing annular tub portion 6 filled with a sealing liquid metal 5 is provided on the upper outer surface of the tank body 1 .

A sealing partition tube 7 is provided at a lower position within the sealing liquid metal 5 of the tub portion 6, with its lower end recessed and suspended from the lower surface of the roof portion 4. This partition tube 7 separates a cover gas space 8 in the tank body 1 and a pit chamber gas space 9 in the pit chamber 2, so that the cover gas in the tank body 1 flows into the pit chamber 2, and the gas in the pit chamber 2 is prevented from flowing into the tank body 1. Tank body 1
Inside is liquid metal, for example, liquid metal sodium 10
is housed therein, and a steam generator 11 whose lower part is immersed in the storium 10 and whose upper part is fixed to the roof part 4 is provided.

Therefore, in the liquid metal storage tank having the above structure, the temperature of the entire wall of the tank body 1 can be maintained close to the temperature of the sodium 10 within the tank body 1. Partition tube 7
reaches the roof part 4, which is close to room temperature, from the high-temperature sealing liquid metal 5, so thermal stress is generated near the connection part between the roof part 4 and the partition tube 7; Since the bow tension load on the bow is small and it receives almost no earthquake load, it is possible to create a thinner structure that is less likely to generate thermal stress, and it is also possible to avoid buckling during an earthquake.

The steam generator 11 is installed on the roof 4 as in the case of a double tank type nuclear reactor, and in the unlikely event that a large amount of water or steam leaks into the sodium 10 from the heat transfer tube inside the steam generator 11. When an event occurs, hydrogen gas generated by the reaction between sodium and water becomes bubbles and is released into the cover gas 8, increasing the pressure in this area. Then, the liquid level 12 of the sealing liquid metal 5 in the handle 6 on the tank 1 side decreases, and the liquid level 13 on the pit chamber 2 side rises, eventually causing gas bubbling to cover the cover gas 8 containing generated hydrogen gas. Air bubbles are generated from the lower end of the partition tube 7 and are discharged to the pit chamber 2 side. This can prevent the cover gas 8 from being abnormally pressurized.

FIG. 2 is a partially cross-sectional view of a second embodiment of the present invention in which the seal handle 6 and partition tube 7 in FIG. 1 are improved.

That is, the seal handle 6a in FIG.
1 has an inner diameter smaller than that of the lower part 22 of the tub, and the lower part 21 of the tub is filled with the liquid metal 5 for sealing. Further, lower and upper prevention plates 23 and 24 for preventing seal liquid from splashing out, which extend perpendicularly to the partition tube 7, are alternately installed in the partition tube 7 located in the lower part 22 of the tub.

When the pressure in the cover gas space 8 becomes high due to these prevention plates 2224 and bubbling is about to occur,
The liquid level on the pit chamber 2 side reaches a wide space and the rising speed becomes slow. Further, even when the hydrogen gas generation is abnormally large and the gas bubbling gas 38 is actively generated, the sealing liquid metal 5 collides with the prevention plate 23, 24 and then returns to the sealing handle 6a again. Therefore, it is possible to prevent a situation in which the sealing function is impaired.

FIG. 3 is a partial vertical sectional view showing a third embodiment of the present invention. The sealing handle 6b is mounted on a pedestal 31 extending from the middle of the pit chamber 2, and is maintained at room temperature. A bellows 32 connects the tank body 1 and the handle 6b.
The bellows 32 absorbs the difference in thermal expansion between the handle 6b at room temperature and the tank body 1 kept at a high temperature.

A second partition tube 34 having a multilayer wire mesh 33 is connected to the partition tube 7 in the handle 6b, and this partition tube 34 is connected to the second handle installed in the upper space of the handle 6b. 35.

Note that the sealing handle 6b in FIG. 3 consists of a tub lower part 22a and a tub lower part 21a having a smaller inner diameter than the tub lower part 22a, as in the embodiment shown in FIG.
A perforated plate 3 having discharge holes for bubbling gas 38 in a
9 is provided.

In the above embodiment, the sodium vapor and mist from the cover gas space 8 in the tank body 1 are transferred to the second handle 35.
Sodium is trapped within the handle portion 35, making it difficult for sodium to enter. The trapped sodium is filled and held in a dump tank 37 through a drain pipe 36. When the sealing liquid metal 5 is at room temperature as shown in FIG. 3, mercury or low-temperature solder is suitable. Further, in the case of high temperatures as shown in FIGS. 1 and 2, high temperature solders such as alloys of lead, tin, bismuth, indium, etc. are suitable. When high-temperature liquid metal is used, it has a high density, so it is desirable to construct a sealed tub that does not cause bubbling during normal pressure fluctuations.

[Effects of the Invention] According to the present invention, a structure that does not have the risk of buckling during an earthquake due to the severe thermal stress caused by the vertical temperature gradient of the tank body in the conventional example can be achieved.

In addition, in the case of a double tank, in the conventional example, there was a risk that the primary tank would buckle due to the pressure of a large amount of hydrogen gas generated due to water leakage from the steam generator, but with the present invention, this can be avoided by quickly releasing the gas. It can be prevented.

[Brief explanation of drawings]

FIG. 1 shows a first example of a liquid metal storage tank according to the present invention. FIGS. 2 and 3 are longitudinal sectional views showing main parts of the second and third embodiments of the present invention, respectively. 8...Cover gas space, 9...Pit chamber gas space 10...Sodium, 11...Steam generator, 12, 13...Liquid level, 21...Bottom part, 22...
Upper part of tub, 23... Lower prevention plate, 24... Upper prevention plate, 31... Pedestal, 32... Bellows, 33... Wire mesh, 34... Second partition tube. 35... Second handle portion, 36... Drain piping, 37...
... Dump tank 38 ... Bubbling gas, 39
...Perforated plate. (8733) Patent attorney Inomata (and 1 other person) 1...Tank body, 2...Pit room, 3.
...Pedestal 4...Roof part, 5...Liquid metal for sealing, 6°6a, 6b...Handle part for sealing, 7...
Partition tube 1.2

Claims (1)

[Claims] A tank body installed in a pit chamber, a sealing bucket part provided on the outer surface of the upper part of the tank body, a roof part that closes the upper end opening of the pit chamber, and a roof part suspended from the lower surface of the roof part. A liquid metal storage tank comprising: a sealing partition tube whose lower end extends to the bottom of the tub; and a sealing liquid metal filled in the tub.