A system and method for residual heat removal of a sodium-cooled fast reactor

Abstract

The present invention discloses a system and method for the decay heat removal of a sodium-cooled fast reactor. The water outlet of the steam-water separator is connected to the inlet of the heat-releasing side of the regenerative heat exchanger. The outlet of the heat-releasing side of the regenerative heat exchanger is connected to the inlet of the drain cooler. The outlet of the drain cooler is divided into two paths. One path is connected to the inlet of the heat-absorbing side of the regenerative heat exchanger through the condensate polishing system, and the other path is connected to one end of the temperature regulating valve. The other end of the temperature regulating valve is connected to the outlet of the heat-absorbing side of the regenerative heat exchanger through a pipe and then connected to the inlet of the deaerator. The gas outlet of the steam-water separator is connected to the inlet of the auxiliary steam header. The outlet of the auxiliary steam header is connected to the inlet of the deaerator. The outlet of the deaerator is connected to the inlet of the steam-water separator through the steam generator. The system and method can effectively ensure the qualified water quality of the feed water of the steam generator of the sodium-cooled fast reactor, reduce the fuel consumption, and avoid wasting a large amount of demineralized water.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear power, and relates to a system and method for removing residual heat from a sodium-cooled fast reactor. Background Art

[0002] After a nuclear power plant reactor is shut down normally, it will still generate a large amount of decay heat for a long time. It is necessary to rely on the continuous operation of the residual heat removal system to export the decay heat of the reactor and perform controllable cooling on the reactor. The general method is to continuously supply a small flow of water to the reactor steam generator (SG) through the feed water system to maintain the SG water level within a reasonable range. The saturated steam generated by the SG flows to the condenser through the bypass system.

[0003] The SG of a sodium-cooled fast reactor is a once-through type, and its operating parameters are higher than those of a pressurized water reactor. After the reactor is shut down, the SG is in a water condition, that is, the SG outlet is high-temperature and high-pressure water. It is necessary to heat and deoxygenate the deaerator with the steam generated by the steam-water separator and ensure the feed water temperature to reduce the thermal shock to the SG.

[0004] During the removal of residual heat from the reactor during normal shutdown and refueling of a sodium-cooled fast reactor, the deaerator pressure is maintained at 1.255 MPa(a), and the outlet water temperature is 190°C. The start-up feed water pump is used to supply feed water to the SG. The high-temperature water at the outlet of the evaporator enters the steam-water separator for steam-water separation. The expanded steam is transported to the auxiliary steam system as the heating steam source for the deaerator, and the drain water is cooled by the drain cooler and returned to the deaerator.

[0005] When the drain water quality at the outlet of the drain cooler meets the requirements of the SG, the drain water from the steam-water separator is directly returned to the deaerator after being cooled by the drain cooler. To maintain the deaerator outlet water temperature not lower than 190°C, only the flash steam from the steam-water separator is used to heat and deoxygenate the water in the deaerator without consuming auxiliary steam, and the drain water temperature at the outlet of the drain cooler should not be lower than 136°C.

[0006] When the drain water quality at the outlet of the drain cooler does not meet the requirements of the SG, it needs to be purified by the condensate polishing system and then returned to the deaerator. To meet the operating requirements of the condensate polishing system, the drain water temperature at the outlet of the drain cooler should not be higher than 50°C. To maintain the deaerator outlet water temperature not lower than 190°C, in addition to the flash steam from the steam-water separator, auxiliary steam provided by the auxiliary boiler is also required to heat and deoxygenate the deaerator.

[0007] For the second case mentioned above, there are certain disadvantages and risks. First, for a single-reactor power plant or the first-reactor project, after the reactor is shut down, the auxiliary boiler is the only steam source. If the auxiliary boiler fails and shuts down at this time, the deaerator heating steam is insufficient, the feed water temperature drops rapidly, which will cause a severe thermal shock to the SG, resulting in an uncontrollable decrease in the primary loop temperature and endangering the operation safety of the key equipment of the reactor; if the condensate polishing circuit is cut off, although the feed water temperature is guaranteed, the unqualified water quality may cause aggravated corrosion of the SG and the steam-water pipelines of the secondary loop. Second, when the auxiliary boiler supplies steam to the deaerator, on the one hand, it will consume a large amount of auxiliary boiler fuel, and on the other hand, the increased water volume in the secondary loop needs to be discharged to the conventional island waste water system, resulting in a large waste of demineralized water. Summary of the Invention

[0008] The purpose of the present invention is to overcome the above-mentioned disadvantages of the prior art, and provides a system and method for sodium-cooled fast reactor residual heat removal. The system and method can effectively ensure the qualified feed water quality, reduce the fuel consumption at the same time, and avoid causing a large waste of demineralized water.

[0009] To achieve the above purpose, the system for sodium-cooled fast reactor residual heat removal described in the present invention includes a steam-water separator, a regenerative heat exchanger, a drain cooler, a condensate polishing system, a temperature regulating valve, a deaerator, an auxiliary steam header and a steam generator;

[0010] The outlet of the steam-water separator is connected to the inlet of the heat release side of the regenerative heat exchanger, the outlet of the heat release side of the regenerative heat exchanger is connected to the inlet of the drain cooler, the outlet of the drain cooler is divided into two paths, one of which is connected to the inlet of the heat absorption side of the regenerative heat exchanger through the condensate polishing system, and the other is connected to one end of the temperature regulating valve. The other end of the temperature regulating valve is connected to the outlet of the heat absorption side of the regenerative heat exchanger through a pipe and then connected to the inlet of the deaerator. The steam outlet of the steam-water separator is connected to the inlet of the auxiliary steam header, the outlet of the auxiliary steam header is connected to the inlet of the deaerator, the outlet of the deaerator is connected to the inlet of the steam-water separator through the steam generator, and a temperature sensor is arranged at the inlet of the deaerator. The signal of the temperature sensor is used to control the temperature regulating valve.

[0011] It also includes a bypass pipeline. Among them, the bypass pipeline is connected in parallel with the heat release side of the regenerative heat exchanger, and a bypass valve is arranged on the bypass pipeline.

[0012] A first valve is arranged at the inlet of the heat release side of the regenerative heat exchanger, and a second valve is arranged at the outlet of the heat release side of the regenerative heat exchanger.

[0013] A third valve is arranged at the inlet of the condensate polishing system, a fourth valve is arranged at the outlet of the condensate polishing system, and a fifth valve is arranged at the outlet of the heat absorption side of the regenerative heat exchanger.

[0014] The auxiliary steam header is also connected to an auxiliary boiler.

[0015] The deaerator is connected to the steam generator via a start-up feed water pump.

[0016] A method for the decay heat removal of a sodium-cooled fast reactor includes the following steps:

[0017] When the quality of the drain water output from the drain cooler meets the requirements of the steam generator, all the isolation valves before and after the condensate polishing system are closed. The drain water output from the steam-water separator enters the drain cooler through a bypass pipeline for cooling, and then all flows through a temperature regulating valve into the deaerator. The water output from the deaerator enters the steam-water separator through the steam generator, and the flashing steam of the steam-water separator is used to heat and deaerate the water in the deaerator.

[0018] When the quality of the drain water output from the drain cooler does not meet the requirements of the steam generator, the water output from the deaerator enters the steam generator for heating. The water output from the steam generator flashes in the steam-water separator. The steam output from the steam-water separator enters the deaerator through the auxiliary steam header. The drain water output from the steam-water separator enters the heat release side of the regenerative heat exchanger to heat the drain water purified by the condensate polishing system. The drain water output from the heat release side of the regenerative heat exchanger enters the drain cooler to cool down. The drain water output from the drain cooler is divided into two paths. One path enters the condensate polishing system, and the drain water purified by the condensate polishing system absorbs heat and rises in temperature from the regenerative heat exchanger. The other path flows through a temperature regulating valve. The water temperature after the two paths converge is controlled by the temperature regulating valve and the temperature sensor. The drain water output from the two paths converges and then enters the deaerator, and is mixed and heat-exchanged with the steam output from the auxiliary steam header in the deaerator for deaeration.

[0019] The present invention has the following beneficial effects:

[0020] When the system and method for the decay heat removal of the sodium-cooled fast reactor according to the present invention are specifically operated, when the quality of the drain water at the outlet of the drain cooler does not meet the requirements of the steam generator, the regenerative heat exchanger is used to heat the drain water with the heat source of the system itself to make the temperature meet the inlet requirements of the deaerator, without relying on the auxiliary steam supplied by the auxiliary boiler, and at the same time avoiding the risk of thermal shock to the steam generator or the risk of equipment corrosion caused by the failure and shutdown of the auxiliary boiler in the original technical solution; and a large amount of auxiliary boiler fuel oil and demineralized water are saved, improving the economy of the power plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of the present invention.

[0022] Among them, 1 is a steam-water separator, 2 is a regenerative heat exchanger, 3 is a drain cooler, 4 is a condensate polishing system, 5 is a temperature regulating valve, 6 is a temperature sensor, 7 is a deaerator, 8 is a start-up feed water pump, 9 is a steam generator, 10 is a auxiliary steam header, 11 is an auxiliary boiler, and 12 is a bypass valve. Specific embodiments

[0023] The present invention will be further described in detail below with reference to the accompanying drawings:

[0024] Reference Figure 1 , the system for sodium-cooled fast reactor residual heat removal according to the present invention includes a steam-water separator 1, a regenerative heat exchanger 2, a drain cooler 3, a condensate polishing system 4, a temperature regulating valve 5, a deaerator 7, an auxiliary steam header 10 and a steam generator 9; the water outlet of the steam-water separator 1 is connected to the heat release side inlet of the regenerative heat exchanger 2, the heat release side outlet of the regenerative heat exchanger 2 is connected to the inlet of the drain cooler 3, the outlet of the drain cooler 3 is divided into two paths, one of which is connected to the heat absorption side inlet of the regenerative heat exchanger 2 through the condensate polishing system 4, and the other is connected to one end of the temperature regulating valve 5, the other end of the temperature regulating valve 5 is connected to the heat absorption side outlet of the regenerative heat exchanger 2 through a pipe and then connected to the inlet of the deaerator 7, the steam outlet of the steam-water separator 1 is connected to the inlet of the auxiliary steam header 10, the outlet of the auxiliary steam header 10 is connected to the inlet of the deaerator 7, the outlet of the deaerator 7 is connected to the inlet of the steam generator 9 through the steam generator 9 and then connected to the inlet of the steam-water separator 1, a temperature sensor 6 is provided at the inlet of the deaerator 7, and the signal of the temperature sensor 6 is used to control the temperature regulating valve 5.

[0025] The present invention further includes a bypass pipeline, wherein the bypass pipeline is connected in parallel with the heat release side of the regenerative heat exchanger 2, and a bypass valve 12 is provided on the bypass pipeline.

[0026] A first valve is provided at the heat release side inlet of the regenerative heat exchanger 2, and a second valve is provided at the heat release side outlet of the regenerative heat exchanger 2; a third valve is provided at the inlet of the condensate polishing system 4, a fourth valve is provided at the outlet of the condensate polishing system 4, and a fifth valve is provided at the heat absorption side outlet of the regenerative heat exchanger 2.

[0027] The auxiliary steam header 10 is also connected to an auxiliary boiler 11; the deaerator 7 is connected to the steam generator 9 through a start-up feed water pump 8.

[0028] The method for sodium-cooled fast reactor residual heat removal according to the present invention includes the following steps:

[0029] When the quality of the drain water output from the drain cooler 3 meets the requirements of the steam generator 9, all the isolation valves before and after the condensate polishing system 4 are closed. The drain water output from the steam-water separator 1 enters the drain cooler 3 through the bypass pipeline for cooling, and then all flows through the temperature regulating valve 5 and enters the deaerator 7. The water output from the deaerator 7 enters the steam generator 9 and then enters the steam-water separator 1, and the flash steam of the steam-water separator 1 is used to heat and deaerate the water in the deaerator 7;

[0030] When the quality of the drain water output from the drain cooler 3 does not meet the requirements of the steam generator 9, the water output from the deaerator 7 enters the steam generator 9 for heating. The water output from the steam generator 9 flashes in the steam-water separator 1. The steam output from the steam-water separator 1 enters the deaerator 7 through the auxiliary steam header 10. The drain water output from the steam-water separator 1 enters the heat release side of the regenerative heat exchanger 2 to heat the drain water purified by the condensate polishing system 4. The drain water output from the heat release side of the regenerative heat exchanger 2 enters the drain cooler 3 for temperature reduction. The drain water output from the drain cooler 3 is divided into two paths. One path enters the condensate polishing system 4, and the drain water purified by the condensate polishing system 4 absorbs heat and rises in temperature from the regenerative heat exchanger 2. The other path flows through the temperature regulating valve 5. The water temperature after the two paths converge is controlled by the temperature regulating valve 5 and the temperature sensor 6. The drain water output from the two paths converges and then enters the deaerator 7, and is mixed and heat-exchanged with the steam output from the auxiliary steam header 10 in the deaerator 7 for deaeration.

[0031] Embodiment 1

[0032] When the quality of the drain water output from the drain cooler 3 meets the requirements of the steam generator 9, the drain water output from the steam-water separator 1 enters the drain cooler 3 through the bypass pipeline for cooling, and then enters the deaerator 7. The water output from the deaerator 7 enters the steam generator 9 and then enters the steam-water separator 1, and the flash steam of the steam-water separator 1 is used to heat and deaerate the water in the deaerator 7. The temperature of the drain water output from the drain cooler 3 is greater than or equal to 136 °C, and in this process, there is no need for the auxiliary boiler 11 to provide steam;

[0033] When the quality of the drain water output by the drain cooler 3 does not meet the requirements of the steam generator 9, the water output by the deaerator 7 enters the steam generator 9 for heating. The water output by the steam generator 9 flashes in the steam-water separator 1. The steam output by the steam-water separator 1 enters the deaerator 7 through the auxiliary steam header 10. The 207°C drain water output by the steam-water separator 1 enters the heat release side of the regenerative heat exchanger 2 to heat the drain water purified by the condensate polishing system 4. The drain water output from the heat release side of the regenerative heat exchanger 2 enters the drain cooler 3 and is cooled to below 50°C. The drain water output by the drain cooler 3 is divided into two paths. One path enters the condensate polishing system 4, and the drain water purified by the condensate polishing system 4 absorbs heat and warms up from the regenerative heat exchanger 2. The other path flows through the temperature regulating valve 5. The drain water output from the two paths converges and then enters the deaerator 7, where it converges with the steam output by the auxiliary steam header 10 and is mixed and heat-exchanged for deaeration using the deaerator 7. Among them, the temperature of the drain water at the inlet of the deaerator 7 is detected by the temperature sensor 6, and the opening of the temperature regulating valve 5 is controlled according to the detected drain water temperature, so that the temperature after the convergence of the two paths of drain water is greater than or equal to 136°C. In this process, it is also not necessary for the auxiliary boiler 11 to provide steam. The drain water flow remains unchanged throughout the cycle. The 207°C drain water temperature at the inlet of the heat release side of the regenerative heat exchanger 2 can fully ensure that the drain water temperature at the inlet of the deaerator 7 is not lower than 136°C.

[0034] Calculated according to the minimum temperature rise of the outlet temperature of the drain cooler 3 being 50°C and the inlet drain water temperature of the deaerator 7 being 136°C, with a drain water flow of 101.31 t / h and the sodium-cooled fast reactor shutdown and refueling time being 7 days, theoretically, 6.148×10^12 J of heat can be recovered and utilized, and the amount of boiler fuel saved is equivalent to saving 209.1 t of standard coal and 2067.1 t of demineralized water.

Claims

1. A method for the decay heat removal of a sodium-cooled fast reactor, characterized in that, based on a system for the decay heat removal of a sodium-cooled fast reactor, the system for the decay heat removal of the sodium-cooled fast reactor includes a steam-water separator (1), a regenerative heat exchanger (2), a drain cooler (3), a condensate polishing system (4), a temperature regulating valve (5), a deaerator (7), an auxiliary steam header (10) and a steam generator (9); The water outlet of the steam-water separator (1) is communicated with the inlet of the heat release side of the regenerative heat exchanger (2), the outlet of the heat release side of the regenerative heat exchanger (2) is communicated with the inlet of the drain cooler (3), the outlet of the drain cooler (3) is divided into two paths, one path passes through the condensate polishing system (4) and is communicated with the inlet of the heat absorption side of the regenerative heat exchanger (2), the other path is communicated with one end of the temperature regulating valve (5), the other end of the temperature regulating valve (5) is communicated with the outlet of the heat absorption side of the regenerative heat exchanger (2) through a pipe and then is communicated with the inlet of the deaerator (7) after merging, the steam outlet of the steam-water separator (1) is communicated with the inlet of the auxiliary steam header (10), the outlet of the auxiliary steam header (10) is communicated with the inlet of the deaerator (7), the outlet of the deaerator (7) passes through the steam generator (9) and is communicated with the inlet of the steam-water separator (1), a temperature sensor (6) is arranged at the inlet of the deaerator (7), and the signal of the temperature sensor (6) is used to control the temperature regulating valve (5); It further includes a bypass pipe, wherein the bypass pipe is connected in parallel with the heat release side of the regenerative heat exchanger (2), and a bypass valve (12) is arranged on the bypass pipe; It includes the following steps: When the drain water quality output by the drain cooler (3) meets the requirements of the steam generator (9), all the isolation valves before and after the condensate polishing system (4) are closed, the drain water output by the steam-water separator (1) enters the drain cooler (3) through the bypass pipe and the bypass valve (12) for cooling, and then all flows through the temperature regulating valve (5) and enters the deaerator (7), the water output by the deaerator (7) is heated by the steam generator (9) and then enters the steam-water separator (1), and the flash steam of the steam-water separator (1) is used to heat and deaerate the water in the deaerator (7); When the quality of the drain water output from the drain cooler (3) does not meet the requirements of the steam generator (9), the water output from the deaerator (7) enters the steam generator (9) for heating. The water output from the steam generator (9) flashes in the steam-water separator (1). The steam output from the steam-water separator (1) enters the deaerator (7) through the auxiliary steam header (10). The drain water output from the steam-water separator (1) enters the heat-releasing side of the regenerative heat exchanger (2) to heat the drain water purified by the condensate polishing system (4). The drain water output from the heat-releasing side of the regenerative heat exchanger (2) enters the drain cooler (3) to be cooled down. The drain water output from the drain cooler (3) is divided into two paths. One path enters the condensate polishing system (4) for water quality purification. The purified drain water flows through the regenerative heat exchanger (2) to absorb heat and increase in temperature. The other path flows through the temperature regulating valve (5). The water temperature after the two paths converge is controlled by the temperature regulating valve (5) and the temperature sensor (6). The drain water output from the two paths converges and then enters the deaerator (7), and after converging with the steam output from the auxiliary steam header (10), the deaerator (7) is used for mixed heat exchange and deaeration.

2. The method for sodium-cooled fast reactor residual heat removal according to claim 1, characterized in that, a first valve is provided at the inlet of the heat-releasing side of the regenerative heat exchanger (2), and a second valve is provided at the outlet of the heat-releasing side of the regenerative heat exchanger (2).

3. The method for sodium-cooled fast reactor residual heat removal according to claim 2, characterized in that, a third valve is provided at the inlet of the condensate polishing system (4), a fourth valve is provided at the outlet of the condensate polishing system (4), and a fifth valve is provided at the outlet of the heat-absorbing side of the regenerative heat exchanger (2).

4. The method for sodium-cooled fast reactor residual heat removal according to claim 1, characterized in that, the auxiliary steam header (10) is also connected to an auxiliary boiler (11).

5. The method for sodium-cooled fast reactor residual heat removal according to claim 1, characterized in that, the deaerator (7) is connected to the steam generator (9) through a start-up feed water pump (8).

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