JPH0498199A - Excessive heat elimination system for emergency of fast reactor - Google Patents

Abstract

PURPOSE:To set the total heat capacity as the whole system small by providing an auxiliary heat exchanger for cooling a reactor core which receives heat from primary cooling material in a primary cooling material entrance chamber at an installation trunk part of a middle heat exchanger. CONSTITUTION:Four middle heat exchangers 7 each including an auxiliary heat exchanger 11 for cooling a reactor core are provided at a roof slab 3, and a secondary side closed circuit is provided commonly for every two of the auxiliary heat exchangers 11 for cooling the reactor core. The core cooling auxiliary heat exchangers 11 cool a primary cooling material entrance chamber 8 of the middle heat exchanger 7 directly, and an auxiliary heat exchanger 12 for cooling a reactor vessel cools a high temperature side pool 5 of the reactor vessel 2 directly. Primary cooling materials cooled at the core cooling auxiliary heat exchanger 11 move down on the primary side of tube bundles in the middle heat exchanger 7 to be discharged to a low temperature side pool 4, go through a suction part and discharge part of a primary main circulation pump 9, flow into the reactor core 1, eliminate decay heat in the core, and be discharged to the high temperature side tool 5. The temperature of the high temperature side pool 5 is increased, and it is eliminated directly by the auxiliary heat exchangers 12 for cooling the reactor vessel, so its temperature rise is restricted. thereby overheating of the reactor vessel is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an emergency residual heat removal system for a liquid metal cooled tank-type fast reactor.

(Prior Art) Two systems conventionally known as emergency residual heat removal systems for tank-type fast reactors will be explained with reference to FIGS. 6 and 7, respectively.

In the tank-type fast reactor shown in FIG. 6, in the reactor vessel 2, a low-temperature side pool 4 serves as a low-temperature coolant area on the inlet side of the reactor core 1-, and a high-temperature side pool 5 serves as a high-temperature coolant area on the exit side of the reactor core 1-. An intermediate heat exchanger 7 and a primary main circulation pump 9 are suspended from the roof slab 3 through a partition wall 6 that partitions the roof slab.

The intermediate heat exchanger 7 is provided with a primary coolant inlet chamber 8 at the top of the tube bundle section, and an inlet for a low-temperature side secondary sodium 20 and an outlet for a high-temperature side secondary sodium 21 at the top of the body. Further, the primary main circulation pump 9 is provided with an auxiliary motor 10 on its upper part, which is powered by an emergency power source. In this emergency residual heat removal system for a tank-type fast reactor, the auxiliary heat exchanger 22 is suspended from the roof slab 3 and directly immersed in the high-temperature side pool 5, and the secondary side of the auxiliary heat exchanger 22 is filled with non-radioactive liquid metal. A closed circuit is formed, and an air cooler 23 is installed in a part of the closed circuit to dissipate residual heat inside the reactor vessel 1 to the outside air. An auxiliary pump 15 that is powered by an emergency power source is installed in this closed circuit, and the air cooler 23 has a blower 16 that is powered by an emergency power source, an inlet for intake air 18, and an outlet for exhaust air 19. It is provided. Additionally, a damper 17 is installed to stop air from flowing in to prevent wasteful heat radiation when the plant is normal. In the fast reactor shown in FIG. 7, in the reactor vessel 2, a roof slab 3 An intermediate heat exchanger 7 and a primary main circulation pump 9 are suspended from the tank. The intermediate heat exchanger 7 is provided with a primary coolant inlet chamber 8 at the top of the tube bundle section, and an inlet for the low temperature side secondary sodium 20 and an outlet for the high temperature side secondary sodium 21 at the top of the body. Also 1
The secondary main circulation pump 9 is provided with an auxiliary motor IO on its upper part that is powered by an emergency power source. Such an emergency residual heat removal system for a tank-type fast reactor is provided with an auxiliary heat exchanger 24 in the primary coolant inlet chamber 8 provided in the intermediate heat exchanger 7,
A closed circuit of non-radioactive liquid metal is formed on the secondary side of this auxiliary heat exchanger 24, and an air cooler 25 is installed in a part of the closed circuit to dissipate residual heat of the reactor into the outside air. An auxiliary pump 15 that is powered by an emergency power source is installed in this closed circuit, and the air cooler 25 has a blower 16 that is powered by an emergency power source, an inlet for intake air 18, and an outlet for exhaust air 19. It is set up. In addition, a damper 17 is installed to stop air from flowing in to prevent wasteful heat radiation when the plant is in normal operation.

In this specification, the system shown in Figure 6 is referred to as the "high temperature pool immersion residual heat removal system", and the system shown in Figure 7 is referred to as the "high temperature pool immersion residual heat removal system".
It is called ``Immersion Residual Heat Removal System in Intermediate Heat Exchanger''.

(Problem to be solved by the invention) The performance required for the emergency residual heat removal system of a fast reactor is as follows.
If some abnormality occurs in the main cooling system, including the steam generator that generates the steam that is supplied to the turbine generator, and the residual heat after the reactor shutdown cannot be removed using normal equipment, the reactor core and reactor vessel will be kept at appropriate temperatures. The purpose is to prevent the rise. In view of this required performance, the problems of the conventional emergency residual heat removal system will be explained below.

(1) In the "high-temperature pool immersion residual heat removal system," the auxiliary heat exchanger inside the reactor vessel cools only the high-temperature side pool during residual heat removal, preventing abnormal temperature rises in the reactor vessel. has immediate effect. On the other hand, in order to cool the reactor core, the natural circulation flow flows from the reactor core exit through the primary side of the intermediate heat exchanger to the low-temperature side pool, passes through the hydraulic section of the primary main circulation pump, and reaches the core inlet. need to be formed.

In this system, in order to form this flow, a wide area of the hot side pool must be cooled, and it takes time to form this natural circulation flow.

Therefore, the cooling capacity of the auxiliary heat exchanger is determined to prevent overheating of the reactor core, and in this case, the cooling capacity becomes excessive compared to the overheating prevention limit of the reactor vessel. In this system, the auxiliary heat exchanger is suspended independently from the roof slab.
An increase in the size of the auxiliary heat exchanger due to excess cooling capacity also leads to an increase in the diameter of the reactor vessel. That is, excessive cooling capacity is undesirable not only from the standpoint of the residual heat removal system but also from the economical point of view of the entire reactor structure.

(2) [Immersion residual heat removal system in intermediate heat exchanger]
In the reactor vessel during residual heat removal, the auxiliary heat exchanger exclusively cools the primary coolant inlet chamber of the intermediate heat exchanger passing through the bulkhead. This primary coolant chamber is a narrow area, and a natural circulation flow from the core outlet to the low temperature pool via the primary side of the intermediate heat exchanger is formed early, so it is immediately effective in cooling the core. There is. However, this system requires time to cool the high-temperature side pool enough to prevent abnormal temperature rises in the reactor vessel.

Therefore, the cooling capacity of the auxiliary heat exchanger is determined by overheating prevention of the reactor vessel, and in this case, the cooling capacity becomes excessive from the overheating prevention limit of the reactor core. In this system, the auxiliary heat exchanger is built into the primary coolant inlet chamber of the intermediate heat exchanger, so the size of the auxiliary heat exchanger increases due to excess cooling capacity, which increases the length of the intermediate heat exchanger and the accompanying atomic heat exchanger. This also leads to an increase in the length of the furnace vessel.

In other words, excessive cooling capacity is undesirable not only from the standpoint of the residual heat removal system but also from the economic standpoint of the reactor structure as a whole.

The present invention has been made to solve the above problems, and is a fast reactor system that eliminates the excessive cooling capacity that conventional emergency residual heat removal systems inevitably have and improves the economic efficiency of the entire reactor structure. The purpose of the present invention is to provide an emergency residual heat removal system.

[Structure of the invention] (Means for solving the problem) The present invention partitions the inside of a reactor vessel housing a reactor core with a partition wall,
A high-temperature coolant region is formed above the reactor core, a low-temperature coolant region is formed below the reactor core, an upper free liquid level of the high-temperature coolant region is covered with an inert gas, and the upper end of the reactor vessel is covered with a roof slab. a primary main circulation pump that circulates the primary coolant from the roof slab into the reactor vessel; and an intermediate heat exchanger that transfers the heat generated in the reactor core from the primary coolant to the secondary coolant. In the emergency residual heat removal system for a fast reactor in which a plurality of auxiliary heat exchangers are suspended, an auxiliary heat exchanger for core cooling that receives heat from the primary coolant is provided in the primary coolant inlet chamber of the installation body of the intermediate heat exchanger. The secondary coolant of this auxiliary heat exchanger for core cooling is made into a liquid metal and is taken out from the installation body of the intermediate heat exchanger to the outside of the reactor vessel through piping,
A core cooling air cooler is installed to dissipate the heat of the secondary coolant to the outside air to create a closed circuit, and an auxiliary reactor vessel cooling heat exchanger is installed in the high temperature coolant area to receive heat from the primary coolant. Suspended from the roof slab, the secondary coolant of the reactor vessel auxiliary heat exchanger is a liquid metal, and is taken out from the installation body of the reactor vessel auxiliary heat exchanger to the outside of the reactor vessel through piping, The air cooler for cooling the reactor vessel, which dissipates the heat of the secondary coolant to the outside air, is installed as a closed circuit.

(Function) The emergency residual heat removal system according to the present invention, which is configured by combining an auxiliary heat exchanger and an air cooler, has the necessary cooling capacity as a condition for preventing overheating of the reactor vessel at a temperature of the high-temperature side pool.
If the core outlet coolant temperature is determined to be 50℃ and 750℃ as the core overheat prevention condition, when the main cooling system is unable to remove heat, the temperature of each part of the coolant area in the reactor vessel will change as shown in Figure 3. Over-designing of cooling capacity is avoided.

That is, FIG. 3 shows the relationship between the temperature of the core outlet coolant region in the reactor vessel and the temperature of the high temperature side pool region with respect to the time after the reactor is shut down. As is clear from Figure 3, the temperature of the coolant in each area changes over time,
It is observed that the temperature decreases rapidly after a predetermined period of time.

(Embodiment) A first embodiment of the emergency residual heat removal system for a tank-type fast reactor according to the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 shows the configuration of an emergency residual heat removal system for a fast reactor in a first embodiment. That is, reactor vessel 2
The inside is partitioned by a partition wall 6 into a low-temperature side pool 4 which is a low-temperature coolant area on the inlet side of the core engineer, and a high-temperature side pool 5 which is a high-temperature coolant area on the exit side of the core 1 . An intermediate heat exchanger 7 is suspended from a roof slab 3 that closes off the upper end of the reactor vessel 3 . A primary coolant inlet chamber 8 is provided within the intermediate heat exchanger 7, and an auxiliary heat exchanger 11 for core cooling is provided within this inlet chamber 8.

A closed circuit of non-radioactive liquid metal is formed on the secondary side of this auxiliary heat exchanger for core cooling, and a core cooling air cooler 13 that radiates heat to the outside air is installed in a part of this closed circuit. In addition, an auxiliary heat exchanger 1 for cooling the reactor vessel is installed in a high temperature side pool 5 on the outlet side of the reactor core 1, which is formed with a partition wall 6 in the reactor vessel 2.
2 is suspended from the roof slab 3 and directly immersed in the high temperature side pool 5.

A closed circuit of non-radioactive liquid metal is formed on the secondary side of the auxiliary heat exchanger 12 for cooling the reactor vessel, and an air cooler 14 for cooling the reactor vessel that radiates heat to the outside air is installed in a part of this closed circuit. There is.

FIG. 2 shows a top view of the reactor vessel of the fast reactor in FIG. 1. That is, as is clear from FIG. 2, four intermediate heat exchangers 7 each having a built-in core cooling auxiliary heat exchanger 11 are installed on the roof slab 3, and the core cooling auxiliary heat exchanger 1 is installed in the roof slab 3.
A common secondary closed circuit is provided for every two units. In addition, an auxiliary heat exchanger 1 for cooling the reactor vessel is installed on the roof slab 3.
Two auxiliary heat exchangers 12 for cooling the reactor vessel are directly installed, and one secondary closed circuit is provided for each auxiliary heat exchanger 12 for cooling the reactor vessel.

Residual heat of the reactor during normal shutdown of the reactor and emergency shutdown due to factors external to the plant is removed by the main cooling system including the steam generator and the steam system of the turbine generator equipment. However, in the event of an abnormality in the system or loss of external power, the system cannot remove residual heat from the reactor. In such a case, the reactor will be automatically brought to an emergency shutdown and the emergency residual heat removal system will be activated.

In the emergency residual heat removal system of the above embodiment, when the emergency power supply equipment operates normally with the emergency shutdown of the nuclear reactor, the blower 16 and damper 17 of the air cooler, the auxiliary pump 15 of the secondary side closed circuit, and the primary main circulation The auxiliary motor 10 of the pump 9 is operated to forcibly dissipate the heat of the coolant taken by the auxiliary heat exchanger 11 for core cooling and the auxiliary heat exchanger 12 for cooling the reactor vessel to the outside air. If the emergency power supply equipment does not operate, only the damper 17 of the air cooler is opened by the uninterruptible power supply equipment to allow natural ventilation. Then, the primary coolant in the reactor vessel 2 and the secondary coolant in the secondary closed circuit flow in natural circulation and are removed by the auxiliary heat exchanger It for cooling the reactor core and the auxiliary heat exchanger 12 for cooling the reactor vessel. The heat of the primary coolant is naturally dissipated to the outside air. Under the operation of each part described above, the auxiliary heat exchanger 11 for core cooling directly cools the primary coolant inlet chamber 8 of the intermediate heat exchanger 7, and the auxiliary heat exchanger 12 for cooling the reactor vessel directly cools the primary coolant inlet chamber 8 of the intermediate heat exchanger 7. The high temperature side pool 5 of the furnace vessel 2 is directly cooled. The primary coolant cooled by the auxiliary heat exchanger 11 for core cooling directly descends through the primary side of the tube bundle of the intermediate heat exchanger 7, is discharged into the low temperature side pool 4, and is passed through the suction section of the primary main circulation pump 9 and It flows into the reactor core 1 via the discharge part, removes the decay heat of the reactor core, and is discharged to the high temperature side pool 5.

Although the temperature of the high-temperature side pool 5 rises as a result, the heat is directly removed by the reactor vessel cooling auxiliary heat exchanger 12, the temperature rise is suppressed, and overheating of the reactor vessel is prevented.

Of the cooling capacity required for the emergency residual heat removal system,
The most severe conditions are that if the emergency power supply is not activated due to an emergency shutdown of the reactor, the core outlet coolant temperature must be kept below 7,500C to prevent the core from overheating, and the high-temperature side pool temperature must be set to 650℃ to prevent the reactor vessel from overheating. It is to be suppressed to the following.

The auxiliary heat exchanger 11 for cooling the reactor core and the air cooler 13 for cooling the reactor core according to this embodiment share only the removal of residual heat to prevent overheating of the reactor core, and the auxiliary heat exchanger 12 for cooling the reactor vessel and the air cooler 13 for cooling the reactor The air cooler 14 is solely responsible for removing residual heat to prevent the reactor vessel from overheating. At that time, the temperature of each area of the reactor vessel coolant changes as shown in Figure 3, and the maximum temperature of both the core outlet coolant temperature and the high temperature side pool temperature should correspond to the respective allowable temperatures above. I can do it. Therefore, excessive design of the cooling capacity of the emergency residual heat removal system is avoided.

FIG. 4 shows the maximum temperature of the coolant during heat removal with respect to the total heat removal capacity of the present invention and the conventional example. The temperatures in FIG. 4 correspond to those in FIG.

FIG. 5 shows a second embodiment of the present invention, showing a top view of the upper part of the reactor vessel. That is, four intermediate heat exchangers 7 with built-in auxiliary heat exchangers for core cooling are installed on the roof slab 3, and one auxiliary heat exchanger 11 for core cooling is installed.
Each unit has an independent secondary closed circuit. In addition, an auxiliary heat exchanger 12 for cooling the reactor vessel is installed on the roof slab 3.
The auxiliary heat exchanger 12 for cooling the reactor vessel is installed directly on the
One secondary closed circuit is provided for each unit. Thereby, the system redundancy of the emergency residual heat removal device according to this embodiment can be strengthened.

The maximum required cooling capacity of the emergency residual heat removal system is determined.Under plant conditions in which the emergency power supply does not operate during an emergency reactor shutdown, the core outlet coolant temperature and high-temperature side pool temperature corresponding to the residual heat removal capacity are set to 100. million kWe
Taking a nuclear power plant as an example, the calculation is as shown in Figure 3.

Here, the allowable upper limits of the core outlet coolant temperature, which is a guideline for determining whether the reactor core is overheating, and the high-temperature side pool temperature, which is a guideline for determining reactor vessel overheating, are set at 750°C and 6508C. In this case, when the heat removal capacities of the conventional example and the present invention are compared based on the calculation results shown in FIG. 4, the results are as shown in the table.

Table Comparison of required heat removal capacity between the present invention and the conventional example [Effects of the invention] The effects of the present invention are as follows.

(1) The total heat removal capacity of the entire system can be smaller than any of the conventional examples.

(2) The number of auxiliary heat exchangers directly immersed in the high-temperature side pool can be reduced by half compared to the conventional example, and the heat removal capacity per unit can be increased by about 20. Therefore, the diameter of the reactor vessel is not only smaller than the conventional emergency residual heat removal system immersed in the high temperature side pool, but also the diameter of the reactor vessel in the conventional emergency residual heat removal system immersed in the intermediate heat exchanger. It becomes possible to install the roof slab in the remaining installation space on the top surface of the roof slab without increasing the dimensions of the roof slab.

(3) The heat removal capacity of the auxiliary heat exchanger installed in the primary side inlet chamber of the intermediate heat exchanger is approximately 30% of that of the conventional example, and the length of the intermediate heat exchanger is shorter than that of the conventional example. It is significantly shorter than the residual heat removal system.

Therefore, the structure of the nuclear reactor can be made smaller than any of the conventional examples, and its economical efficiency is improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the emergency residual heat removal system for a nuclear reactor according to the present invention, FIG. 2 is a top view of FIG. 1, and FIG. 3 is an emergency FIG. 4 is a graph showing the relationship between the maximum coolant temperature during heat removal and the total heat removal capacity of the present invention and the conventional example. FIG. A top view showing an embodiment of the present invention, FIGS. 6 and 7 are block diagrams showing a conventional emergency residual heat removal system for a nuclear reactor, respectively. 1... Furnace core 3... Roof slab 5... High temperature side pool 7... Intermediate heat exchanger 8... Primary coolant inlet chamber 9... Primary main circulation pump 10...・Auxiliary motor 1
1... Auxiliary heat exchanger for core cooling 12... Auxiliary heat exchanger for reactor vessel cooling 13... Air cooler for core cooling 2... Reactor vessel 4... Low temperature side pool 6. ... Bulkhead 14 ... Reactor vessel cooling air cooler 15 ... Auxiliary pump I6 ... Blower 17 ... Damper
18...Intake air I9...Exhaust air 20...Low temperature side secondary sodium 21...High temperature side secondary sodium 22...Auxiliary heat exchanger 23...Air cooler 2
4...Auxiliary heat exchanger 25...Air cooler (8733) Agent: Patent attorney Yoshiaki Inomata (and others)
1 person) Akisuhi 9N Diagram

Claims (1)

[Claims] The interior of the reactor vessel housing the reactor core is partitioned with partition walls, a high temperature coolant region is formed above the core, a low temperature coolant region is formed below the core, and the upper free liquid level of the high temperature coolant region is inert. a primary main circulation pump that is covered with gas, closes the upper end of the reactor vessel with a roof slab, and circulates a primary coolant from the roof slab into the reactor vessel;
In an emergency residual heat removal system for a fast reactor that suspends a plurality of intermediate heat exchangers that transfer heat generated in the core from the secondary coolant to the secondary coolant, the primary cooling of the installation body of the intermediate heat exchanger is performed. A core cooling auxiliary heat exchanger that receives heat from the primary coolant is provided in the material inlet chamber, and the secondary coolant of the core cooling auxiliary heat exchanger is liquid metal, and the intermediate heat exchanger is A core cooling air cooler is installed outside the reactor vessel via piping and dissipates the heat of the secondary coolant to the outside air to create a closed circuit, and the high-temperature coolant area is provided with the
An auxiliary heat exchanger for cooling the reactor vessel that receives heat from the secondary coolant is suspended from the roof slab, and the secondary coolant of the auxiliary heat exchanger for the reactor vessel is liquid metal, and the auxiliary heat exchanger for the reactor vessel is suspended from the roof slab. A nuclear reactor characterized in that an air cooler for cooling the reactor vessel is installed, which is taken out from the installation body of the reactor to the outside of the reactor vessel via piping and dissipates the heat of the secondary coolant to the outside air, forming a closed circuit. Emergency residual heat removal system.