RU2622408C1 - Emergency system of quick neutron reactor active zone power generation discharge - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: system contains an air heat exchanger circuit with internal bottom heat exchanger located directly in the reactor active zone, and external heat exchanger in the air exhaust duct outside the sealed envelope. At that, heat exchangers and connecting pipelines are filled with liquid sodium, and a magnetohydrodynamic pump connected to an additional thermocouple installed in the reactor active zone is included into the rupture of one of the external heat exchanger pipelines. The external receiver of excess heat energy where the external heat exchanger is installed, can be made from a ventilated duct connected to the station exhaust pipe or as an additional heat exchanger connected to the external heat exchanger pipeline.

EFFECT: increased reliability due to provision of a continuous mode of operation for energy releases removal from the reactor active zone, regardless of the state and operation of the existing active system for excess heat energy removal from the reactor, as well as for complete disconnections of the main and backup power sources of the nuclear power plant.

2 cl, 1 dwg

Description

The well-known "System of passive removal of residual heat of a nuclear reactor" [1], authors Berkovich VM, Tatarnikov VP and etc.

The system contains a nuclear reactor, a coolant circulation circuit, an air-cooled heat exchanger located in the exhaust pipe, and separators-heat exchangers for different loops of the circulation circuit connected through an ejector.

This system is intended for use in nuclear power plants with water-water reactors, as well as in emergency cooldown devices for pool-type nuclear reactors. The coolant in the system is water. All of the above equipment in the system, except for the heat exchanger in the exhaust pipe, is located inside the containment (pressure seal). This system is unsuitable for fast neutron reactors in which the liquid metal working fluid is sodium, which actively interacts with water and generates gaseous hydrogen. It is not possible to replace sodium with water in a passive heat removal system according to this scheme.

Also known is the "System for limiting the consequences of an accident at a nuclear power plant" [2], author Muravyov VP

The system comprises a sprinkler installation inside the reactor room, connected by a pressure pipe to a sprinkler water pump located outside the reactor room, connected by a suction pipe to the reactor water collection pit through a heat exchanger included in the non-reactor closed cooling circuit containing a pump. In addition, the system is equipped with a closed circuit of low-boiling liquid containing a turbine, a condenser pump, a check valve and a heat exchanger evaporator in the pit of the reactor.

This system is very difficult to implement due to the presence of an additional low-boiling liquid circuit. In addition, it is inoperative while simultaneously disconnecting the main and backup energy sources in emergency situations, as the cooling circuit pump will be de-energized.

It is also known “Device for removing excess thermal energy from the internal volume of the protective shell of a nuclear power plant”, authors Mustafin MR, Bumagin V.D. et al. [3].

This invention can be used in an emergency when the active power sources are completely turned off and allows passive removal of excess thermal energy into the atmosphere from the internal volume of the containment (containment).

The device comprises pipe-connected heat exchangers with a low-boiling coolant, the lower heat exchanger located in the water tank inside the protective shell, and the upper one on the outer surface of the dome wall of the protective shell.

The inclusion in the work of the passive system of low-boiling coolant is provided by a bellows servo drive.

The disadvantage of this system is that it cannot be used at nuclear power plants in fast neutron reactors using liquid metals as a working fluid, for example, sodium, which enters into an explosive reaction with water and type C freon used in this patent.

The disadvantage is also the standby mode of operation of this passive part of the system and the beginning of its operation only in the event of the termination of the active part due to disconnection of the main and backup power supply of the pumps. The reliability of the inclusion of the standby mode of the system should be provided by bellows having a high failure rate.

The objective of the present invention is to provide a highly reliable autonomous system for the emergency removal of energy releases from the fast-neutron reactor of a nuclear reactor with a liquid metal working fluid, for example, sodium in the reactor.

The closest analogue (prototype) of the present invention is the "Scheme of emergency heat removal of fast reactors (BR)", Fig. 36, p. 88 from the book of N.N. Oshkanova [4] (see the appendix to this application).

This device contains an air heat exchanger (WTO) with a sodium coolant, consisting of an autonomous lower circuit of the WTO located in the coolant of the reactor core, and an external heat exchanger installed in the air exhaust duct (exhaust pipe). The movement of molten liquid sodium between the internal and external heat exchangers is carried out by convection through pipelines due to natural circulation.

The heated sodium in the internal lower heat exchanger of the WTO circuit, due to natural circulation, rises and gives off heat in the external heat exchanger to the air in the exhaust pipe, and the cooled sodium is returned to the lower heat exchanger.

However, the disadvantage of this device is the relatively low amount of thermal energy, which is transferred by convection from the reactor core to an external heat exchanger and then to the exhaust pipe due to the natural circulation of the coolant.

The technical result of the invention is to increase the reliability of emergency heat removal due to the inclusion of a magnetohydrodynamic (MHD) pump in the pipeline of the upper air heat exchanger, placement of a thermal converter in the reactor core and its connection to the MHD pump, which ensures continuous autonomous operation as a passive safety system for nuclear power plants , and emergency removal of reactor energy releases, regardless of the state and operation of the existing active system for removing excess heat nergii beyond containment.

Thus, the proposed technical solution allows to maximize the safety of operation of nuclear power plants on a liquid metal working fluid.

As a result of an information search on the sources of patent and scientific and technical information, we did not find a set of features characterizing the described “Emergency removal system for energy release from the fast reactor core”.

The proposed technical solution can find application as an additional system of autonomous passive safety at existing and newly designed nuclear power plants with a liquid metal working fluid in the reactor.

Existing active safety systems for nuclear power plants are not considered in this description.

The drawing conventionally depicts elements of the proposed NPP safety system: reactor housing 1, in which the coolant 2 is located - a molten liquid metal working fluid of the reactor core, for example sodium, and a set of fuel assemblies, the lower heat exchanger 3 of the reactor air cooling circuit connected by pipelines 4 to an external heat exchanger 5 of the same circuit located in the air exhaust duct 6 of the exhaust pipe. Heat exchanger radiators and pipelines connecting them are filled with molten sodium.

A thermoconverter 7 is placed in the reactor core, and a magnetohydrodynamic pump 8 (MHD pump) is included in the rupture of the external heat exchanger pipeline, wires 9 from which are connected to the thermocouple 7. In this system, it is also advisable to use an additional heat exchanger connected to the pipeline of the external heat exchanger located behind pressurized shell and outside the pipe zone (not shown in the drawing). This will increase the reliability of the system in case of pipe collapse in case of emergency.

The system of emergency removal of energy releases from the reactor core on fast neutrons works as follows.

It is not possible to use thermosiphon and other types of water heat exchangers to cool the reactor at such stations, because if there is a defect in the heat exchanger and water leaks, an explosive reaction of the sodium melt with water can occur.

The most widely used are nuclear power plants with fast neutron reactors, in which sodium melt is used as a liquid metal working fluid in both reactors and heat exchangers.

Passive cooling in such reactors is carried out by air heat exchangers, the internal lower heat exchangers 3 of which are located directly in the reactor core 1, and their external external heat exchangers 5 connected by pipelines 4 are located in the air exhaust channel 6 of the exhaust pipe.

In the operating mode of the station, due to the presence of a high exhaust pipe, there is a significant air draft, which creates its intense movement and actively cools the external heat exchanger 5. Due to natural convection, the hot working fluid - liquid sodium - moves from the lower heat exchanger 3 upward through pipelines 4, and chilled sodium from the external heat exchanger 5 - down, circulating in a closed loop.

In this operating mode, passive cooling of the reactor due to sodium convection works in addition to the active safety system of nuclear power plants, operating from various external sources of energy supply.

However, in case of emergency (earthquake, hostilities, terrorist attack, etc.), all external sources of electrical energy that provide the active safety system can be disconnected, and the capacity for cooling the reactor only due to passive cooling by an air heat exchanger with natural convection is not enough.

To enhance convection and active circulation of the sodium melt in the air heat exchanger, it is proposed to include the MHD pump 8, which is powered by wires 9 from the newly introduced thermal converter 7 located in the reactor core 1, into the gap of one of the pipelines 4.

The electric energy generated by the thermoconverter 7, ensures the operation of the MHD pump 8, which guarantees enhanced circulation of liquid sodium between the lower and upper radiators of the air heat exchanger.

In addition, with increasing temperature inside the reactor core, the EMF of the thermal converter also increases and, accordingly, the productivity of the MHD pump, which intensifies the process of cooling the sodium melt, increases.

Thus, in a certain range, stabilization of the temperature of the reactor in automatic mode is ensured and no external energy sources are used.

It is advisable to place the external heat exchanger 5 of the emergency reactor cooling system at newly designed facilities not only in the exhaust duct of the pipe, but also in the form of an additional heat exchanger behind the containment outside the pipe of the nuclear power plant. This will eliminate the accident of the exhaust channel associated with the collapse of the pipe caused by emergency.

The proposed autonomous system, which improves and complements the passive safety of a fast neutron nuclear power plant, allows for continuous removal of energy releases from the reactor core, regardless of the operating conditions of the existing active safety system of nuclear power plants, which significantly increases the safety of operation of such plants.

INFORMATION SOURCES

1. Berkovich V.M., Tatarnikov V.P. etc. The system of passive removal of residual heat of a nuclear reactor. RF patent No. 2002321. IPC G21C 15/18 (analog).

2. Muravyov V.P. System for limiting the consequences of an accident at a nuclear power plant. RF patent No. 2030801. IPC G21C 13/10 (analog).

3. Mustafin M.R., Bumagin V.D. etc. A device for removing excess thermal energy from the internal volume of the protective shell of a nuclear power plant. RF patent No. 2504031. IPC G21C 15/00 (analog).

4. Oshkanov N.N. Physical and technological features of fast neutron reactors. Yekaterinburg, UrFU, 2011, Fig. 36, p. 88 (prototype).

5. US patent 6069930 A1, 05/30/2000 (analogue).

6. European patent 2096644 B1. 09/12/2012 (analog).

7. Kolykhan L.I., Naganov A.V. Passive safety system of a nuclear power plant. USSR copyright certificate No. 1829697. IPC G21C 9/00 (analog).

8. Berkovich V.M., Molchanov I.V. and others. Power plant. USSR copyright certificate No. 1681032. IPC F01K 13/12 (analog).

9. The patent of Germany No. 3129289, IPC G21C 15/18, 1982 (analogue).

10. French patent No. 2550371 A2, 02/08/1985 (analogue).

11. Andreev V.I., Zverev S.A., Upyrev V.N. Emergency cooldown system for a research nuclear reactor. USSR copyright certificate No. 1503047. IPC G21C 15/18 (analog).

12. Japan application No.2001188094 A. 07/10/2001 (analogue).

13. Bumagin V.D., Shirokov-Bryukhov E.F. etc. A device for air cooling of a system for passive heat removal from the protective shell of a nuclear power plant. RF patent No. 2450375. IPC G21C 9/00 (analog).

Claims (2)

1. The system of emergency removal of energy releases from the active zone of a fast neutron reactor, consisting of an autonomous air-cooling circuit with its own liquid metal coolant, which includes a lower heat exchanger connected by pipelines installed in the reactor core coolant and an external heat exchanger located in the air exhaust channel the fact that an MHD pump is included in the pipeline of the external heat exchanger, and a thermal converter is introduced into the reactor core, the latter with single with MHD pump. 2. The system for emergency removal of energy releases from the fast neutron reactor core according to claim 1, characterized in that an additional heat exchanger connected to the pipeline of the external heat exchanger of the system is introduced outside the zone of the reactor’s pressurized shell.

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