Small PWR Secondary Side Residual Heat Removal System

Abstract

The present invention discloses a secondary side residual heat removal system for a small pressurized water reactor, which includes a first loop and a second loop that are independent of each other. The first loop and the second loop respectively include a steam generator, a main steam pipeline, redundantly provided main steam isolation valves, a condenser, a drain tank, redundantly provided condensate suction pumps and check valves, redundantly provided main feed water isolation valves, main feed water check valves and main feed water pipelines that are connected in sequence; and three independent power supply sequences A, B, and C. Among them, the power supply sequences A and B respectively supply power to the redundantly provided main steam isolation valves, the redundantly provided condensate suction pumps and check valves, and the redundantly provided main feed water isolation valves in the first loop and the second loop, and the power supply sequence C is a redundant power supply sequence shared by the power supply series A and B.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear power, and more specifically, relates to a secondary side residual heat removal system for a small pressurized water reactor. Background Art

[0002] After a nuclear accident, a nuclear power plant must utilize dedicated safety systems to ensure emergency shutdown of the reactor, removal of residual heat from the core, and the integrity of the containment vessel. This is to limit further development of the accident and mitigate its consequences. Traditional pressurized water reactor (PWR) nuclear power plants often utilize emergency residual heat removal systems, one of their dedicated safety systems, as a cooling method to remove residual heat from the core when normal heat removal pathways fail. Therefore, the design of these systems is a key technology in reactor design.

[0003] Currently, nuclear power plants generally utilize active emergency residual heat removal systems. For example, some reactor emergency residual heat removal functions utilize active auxiliary feedwater systems and steam-to-atmosphere venting systems. These systems typically have three loops and three corresponding steam generators. Each loop primarily consists of an auxiliary feedwater storage tank, an electric auxiliary feedwater pump, a pneumatic feedwater pump, and associated piping and valves. The auxiliary feedwater pumps supply desalted water from the auxiliary feedwater tanks to the secondary side of the steam generators, where the generated steam is discharged to the atmosphere, the ultimate heat sink, thereby removing the reactor residual heat. To meet the single failure criterion, active components (such as the auxiliary feedwater pumps) must be designed with redundancy to reduce the probability of system failure.

[0004] The aforementioned emergency residual heat removal system is characterized by high heat removal efficiency and sufficient cooling resources, enabling it to quickly remove residual heat from the core. However, it requires advanced water treatment equipment and a large auxiliary feedwater storage tank. Consequently, its configuration is complex, space-intensive, and water-intensive, limiting its use in offshore small pressurized water reactors (PWRs) located far from land.

[0005] In view of this, it is indeed necessary to provide a small pressurized water reactor secondary side residual heat removal system that can cooperate with the steam generator to remove the core residual heat under reactor accident conditions. Summary of the Invention

[0006] The object of the present invention is to overcome at least one defect in the prior art and provide a small pressurized water reactor secondary side waste heat removal system that can cooperate with the steam generator to remove the core waste heat under reactor accident conditions.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides a small pressurized water reactor secondary side residual heat removal system, which comprises:

[0008] A first circuit and a second circuit independent of each other, the first circuit and the second circuit respectively comprising a steam generator, a main steam pipeline, redundantly provided main steam isolation valves, a condenser, a drain tank, redundantly provided condensate suction pumps and check valves, redundantly provided main feed water isolation valves, main feed water check valves and a main feed water pipeline connected in sequence; and

[0009] Three independent power supply sequences A, B, and C;

[0010] Wherein, the power supply sequences A and B respectively supply power to the redundantly provided main steam isolation valves, the redundantly provided condensate suction pumps and check valves, and the redundantly provided main feed water isolation valves in the first circuit and the second circuit, and the power supply sequence C is a redundant power supply sequence shared by the power supply sequences A and B.

[0011] According to an embodiment of the secondary side residual heat removal system of the small pressurized water reactor of the present invention, a cooler is provided between the drain tank, the redundantly provided condensate suction pumps and check valves.

[0012] According to an embodiment of the secondary side residual heat removal system of the small pressurized water reactor of the present invention, the redundantly provided main steam isolation valves include two main steam isolation valve branches connected in parallel, and two motorized isolation valves are connected in series on each main steam isolation valve branch.

[0013] According to an embodiment of the secondary side residual heat removal system of the small pressurized water reactor of the present invention, in one of the main steam isolation valve branches of the main steam isolation valve branch, one motorized isolation valve is normally closed and is equipped with the power supply sequence A, and the other motorized isolation valve is normally open and is equipped with the power supply sequence C; in the other main steam isolation valve branch of the main steam isolation valve branch, one motorized isolation valve is normally closed and is equipped with the power supply sequence C, and the other motorized isolation valve is normally open and is equipped with the power supply sequence A.

[0014] According to an embodiment of the secondary side residual heat removal system of the small pressurized water reactor of the present invention, when the pressure on the secondary side of the steam generator is too high and the system is overpressured, either the power supply sequence A or the power supply sequence C can cause the two motorized isolation valves in the two main steam isolation valve branches connected in parallel to close simultaneously.

[0015] According to an embodiment of the secondary side residual heat removal system of the small pressurized water reactor of the present invention, the redundantly provided condensate suction pumps and check valves include two suction branches connected in parallel, and each suction branch includes a condensate suction pump and a check valve connected in series.

[0016] According to an embodiment of the secondary side residual heat removal system of the small pressurized water reactor of the present invention, the redundantly provided main feed water isolation valves include two main feed water isolation valves connected in parallel.

[0017] According to an embodiment of the secondary side residual heat removal system of the small pressurized water reactor of the present invention, the first loop is arranged on one side of the hull, and the second loop is arranged on the other side of the hull and is independent of the first loop.

[0018] According to an embodiment of the secondary side residual heat removal system of the small pressurized water reactor of the present invention, the steam generators of the first loop and the second loop are located inside the containment.

[0019] According to an embodiment of the secondary side residual heat removal system of the small pressurized water reactor of the present invention, the design pressure of the secondary side residual heat removal system of the small pressurized water reactor is less than the pressure of the primary loop.

[0020] Compared with the prior art, the secondary side residual heat removal system of the small pressurized water reactor of the present invention has the following advantages: The independent first loop and second loop make the system have sufficient redundancy. With two steam generators, the first loop and the second loop are distributed in two rows on the left and right sides of the hull. Among them, the first loop and the second loop adopt a closed secondary side circulation cooling loop, which does not consume demineralized water as the circulating medium during operation, reduces the demand for demineralized water, has 100% residual heat removal capacity, and is applicable to small pressurized water reactors in marine environments with scarce fresh water. In addition, the active components in the first loop and the second loop are redundantly arranged and equipped with an independent power supply sequence, which can realize the safety functions of automatic startup and isolation of the system, and solve the problem that the initiating event causing an accident makes one column of the system unavailable and the other column of the system loses the residual heat removal function due to a single fault. Brief Description of the Drawings

[0021] The following combines the drawings and specific embodiments to detail the secondary side residual heat removal system of the small pressurized water reactor of the present invention and its technical effects, where:

[0022] Figure 1 is a schematic diagram of the secondary side residual heat removal system of the small pressurized water reactor of the present invention.

[0023] Figure 2 is a schematic diagram of a working state of the secondary side residual heat removal system of the small pressurized water reactor of the present invention.

[0024] Figure 3 is a schematic diagram of another working state of the secondary side residual heat removal system of the small pressurized water reactor of the present invention.

[0025] In the figure:

[0026] 10 - First loop; 11 - First steam generator; 12 - First main steam pipeline; 13a, 13c, 14a, 14c - First main steam isolation valves; 15 - First condenser; 16 - First drain tank; 17 - First cooler; 18a, 18c - First condensate suction pumps; 19 - First check valve; 110a, 110b - First main feed water isolation valves, 111 - First main feed water check valve; 112 - First main feed water pipeline;

[0027] 20 - Second loop; 21 - Second steam generator; 22 - Second main steam pipeline; 23c, 24b, 23b, 24c - Second main steam isolation valves; 25 - Second condenser; 26 - Second drain tank; 27 - Second cooler; 28c, 28b - Second condensate suction pumps; 29 - Second check valve; 210c, 210b - Second main feed water isolation valves, 211 - Second main feed water check valve; 212 - Second main feed water pipeline. Detailed implementation manners

[0028] In order to make the object, technical solutions and technical effects of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and specific implementation manners. It should be understood that the specific implementation manners described in this specification are only for explaining the present invention and not for limiting the present invention.

[0029] Please refer to Figure 1 as shown in the figure, the present invention provides a secondary side residual heat removal system for a small pressurized water reactor, which includes:

[0030] The first loop 10, including a first steam generator 11, a first main steam pipeline 12, redundantly provided first main steam isolation valves 13a, 13c, 14a, 14c, a first condenser 15, a first drain tank 16, redundantly provided first condensate suction pumps 18a, 18c and a first check valve 19, redundantly provided first main feed water isolation valves 110a, 110b, a first main feed water check valve 111 and a first main feed water pipeline 112, which are connected in sequence;

[0031] The second loop 20, which is independently provided from the first loop 10, includes a second steam generator 21, a second main steam pipeline 22, redundantly provided second main steam isolation valves 23c, 24b, 23b, 24c, a second condenser 25, a second drain tank 26, redundantly provided second condensate suction pumps 28c, 28b and a second check valve 29, redundantly provided second main feed water isolation valves 210c, 210b, a second main feed water check valve 211 and a second main feed water pipeline 212, which are connected in sequence; and

[0032] Three independent power supply sequences A, B, and C;

[0033] Among them, the power supply sequences of A and B are respectively the first main steam isolation valves 13a, 13c, 14a, 14c / the second main steam isolation valves 23c, 24b, 23b, 24c redundantly arranged in the first loop 10 and the second loop 20; the first condensate suction pumps 18a, 18c / the second condensate suction pumps 28c, 28b redundantly arranged and the first check valve 19 / the second check valve 29; the first main feed water isolation valves 110a, 110b / the second main feed water isolation valves 210c, 210b redundantly arranged are powered. The power supply sequence of C is a redundant power supply sequence shared by the power supply series of A and B, and is used to supply power to the redundant active components in the first loop 10 and the second loop 20. Under the condition that the normal heat rejection path of the reactor fails, the active components corresponding to the three power supply sequences of A, B, and C are simultaneously started to perform the residual heat removal function.

[0034] According to an embodiment of the secondary side residual heat removal system of the small pressurized water reactor of the present invention, downstream of the first drain tank 16, that is, between the first drain tank 16 and the first condensate suction pumps 18a, 18c and the first check valve 19 redundantly arranged, a first cooler 17 is provided; downstream of the second drain tank 26, that is, between the second drain tank 26 and the second condensate suction pumps 28c, 28b and the second check valve 29 redundantly arranged, a second cooler 27 is provided. With such a setting, the subcooling degree of the water at the inlets of the first condensate suction pumps 18a, 18c / the second condensate suction pumps 28c, 28b can be increased, effectively preventing the system from failing due to cavitation of the condensate suction pumps under transient conditions, and improving the stability of the system operation.

[0035] According to an embodiment of the secondary side residual heat removal system of the small pressurized water reactor of the present invention, the redundantly provided first main steam isolation valves 13a, 13c, 14a, 14c include two main steam isolation valve branches arranged in parallel, and the motorized isolation valves 13a, 14c and 13c, 14a are respectively arranged in series on each main steam isolation valve branch; the redundantly provided first main feed water isolation valves 110a, 110b include two first main feed water isolation valves 110a, 110b arranged in parallel. The redundantly provided second main steam isolation valves 23c, 24b, 23b, 24c include two main steam isolation valve branches arranged in parallel, and two motorized isolation valves 23c, 24b and 23b, 24c are respectively arranged in series on each main steam isolation valve branch. The redundantly provided first condensate suction pumps 18a, 18c and the first check valve 19 include two suction branches arranged in parallel, and each suction branch includes the first condensate suction pumps 18a, 18c and the first check valve 19 arranged in series. The redundantly provided second condensate suction pumps 28c, 28b and the second check valve 29 include two suction branches arranged in parallel, and each suction branch includes the first condensate suction pumps 28c, 28b and the first check valve 29 arranged in series. The redundantly provided second main feed water isolation valves 210c, 210b include two first main feed water isolation valves 210c, 210b arranged in parallel. By arranging 2x2 motorized isolation valves at the inlet and 1x2 motorized isolation valves at the outlet, the safety functions of automatic system startup and isolation can be achieved, effectively preventing system overpressure.

[0036] According to an embodiment of the secondary side residual heat removal system of the small pressurized water reactor of the present invention, the first loop 10 is arranged on one side of the hull, the second loop 20 is arranged on the other side of the hull and is independent of the first loop 10. The first loop 10 and the second loop 20 have 100% residual heat removal capacity. When the system operates, it does not consume the demineralized water as the circulating medium, reducing the demand for demineralized water, and is applicable to the marine pressurized water reactor in the marine environment with scarce fresh water. The first steam generator 11 of the first loop 10 and the second steam generator 21 of the second loop 20 are located inside the containment. The design pressure of the secondary side residual heat removal system of the small pressurized water reactor is less than the pressure of the primary loop to improve the economy of the system.

[0037] The following is combined with Figures 2 to 3 as shown, taking the first loop 10 as an example for illustration, the working principle of the secondary side residual heat removal system of the small pressurized water reactor of the present invention is described in detail:

[0038] The motor-operated isolation valve 13a on one branch of the inlet main steam isolation valve is normally closed and powered by power supply A; the motor-operated isolation valve 14c is normally open and powered by power supply C; the motor-operated isolation valve 13c on the other branch of the inlet main steam isolation valve is normally closed and powered by power supply C, and the motor-operated isolation valve 14a is normally open and powered by power supply A. When the reactor loses the normal heat rejection path and the system is put into operation, any one of the two normally closed inlet motor-operated isolation valves 13a or 13c can be opened by any one of the power supply sequences (A or C), so as to realize the automatic operation of the system; when the secondary side pressure of the steam generator is too high and the system is overpressured, any one of the power supply sequences (A or C) can close two of the four inlet motor-operated isolation valves 13a, 14a or 13c, 14c simultaneously, so as to realize the automatic isolation of the system.

[0039] When the system is normally started, the active components corresponding to the power supply sequences of A and C are put into operation simultaneously, such as the first main steam isolation valves 13a, 13c, the first main feed water isolation valves 110a, 110b, the first condensate extraction pumps 18a, 18c. The water stored in the first drain tank 16 is injected into the secondary side of the first steam generator 11 through the first main feed water pipeline 112. The injected water is heated by the residual heat of the reactor to generate steam. The steam enters the first condenser 15 through the first main steam pipeline 12, and condenses into water on the shell side of the first condenser 15. The condensed water flows into the downstream first drain tank 16 by gravity, and after being further cooled by the first cooler 17, is transported by the first condensate extraction pumps 18a, 18c to the secondary side of the first steam generator 11 to generate steam, forming a closed cycle, continuously taking away the residual heat of the primary loop and discharging it to the equipment cooling water system, and then discharging it to the ultimate heat sink - seawater.

[0040] From the above detailed description of the embodiments of the present invention, it can be seen that compared with the prior art, the secondary side residual heat removal system of the small pressurized water reactor of the present invention has the following advantages:

[0041] The independent first loop 10 and second loop 20 endow the system with sufficient redundancy. Together with two steam generators 11 and 12, the first loop 10 and the second loop 20 are distributed in two columns on the left and right sides of the hull, enhancing the independence of the system. Among them, the first loop 10 and the second loop 20 adopt a closed secondary side circulation cooling loop, which does not consume demineralized water as the circulating medium during operation, reducing the demand for demineralized water. It has a 100% residual heat removal capacity and is applicable to marine pressurized water reactors in marine environments with scarce fresh water. In addition, the active components in the first loop 10 and the second loop 20 are provided with redundancy and are equipped with three independent power supply sequences A, B, and C. The combined method of A + C and B + C is used to supply power to the parallel active components in the two columns, avoiding the loss of the residual heat removal function due to power failure or active component failure in the system. The safety functions of automatic startup and isolation of the system can be realized, solving the problem that the initial event causing an accident makes one column of the system unavailable and the other column of the system loses the residual heat removal function due to a single fault, improving the reliability of the system.

[0042] According to the above principle, the present invention can also make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A secondary side waste heat removal system for a small marine pressurized water reactor, characterized in that: include: a first circuit and a second circuit that are independent of each other, wherein the first circuit and the second circuit respectively include a steam generator, a main steam pipeline, a redundant main steam isolation valve, a condenser, a drain tank, a redundant condensate suction pump and a check valve, a redundant main feedwater isolation valve, a main feedwater check valve, and a main feedwater pipeline that are connected in sequence; and Three independent power supply sequences: A, B, and C; The A and B power supply sequences are respectively used to power the redundant main steam isolation valve, the redundant condensate suction pump and check valve, and the redundant main feedwater isolation valve in the first and second circuits, and the C power supply sequence is a redundant power supply sequence shared by the A and B power supply sequences. The redundant main steam isolation valve comprises two main steam isolation valve branches arranged in parallel, and each main steam isolation valve branch is provided with two electric isolation valves in series; The redundantly arranged condensate suction pump and check valve include two suction branches arranged in parallel, and each of the suction branches includes a condensate suction pump and a check valve connected in series; The redundant main water supply isolation valve comprises two main water supply isolation valves arranged in parallel; Among them, one electric isolation valve on one main steam isolation valve branch at the inlet is normally closed and supplied with power A, and the other electric isolation valve is normally open and supplied with power C; one electric isolation valve on another main steam isolation valve branch at the inlet is normally closed and supplied with power C, and the other electric isolation valve is normally open and supplied with power A; when the reactor loses its normal heat dissipation path and the system is put into operation, the A or C power supply sequence can open one of the two normally closed electric isolation valves to realize automatic commissioning of the system; when the secondary side pressure of the steam generator is too high and the system is overpressured, the A or C power supply sequence can close two of the four electric isolation valves at the same time to realize automatic isolation of the system.

2. The secondary side waste heat removal system for a small marine pressurized water reactor according to claim 1, characterized in that: A cooler is provided between the drain tank, the redundantly arranged condensate suction pump and the check valve.

3. The secondary side waste heat removal system for a small marine pressurized water reactor according to claim 1, characterized in that: The first circuit is arranged on one side of the hull, and the second circuit is arranged on the other side of the hull and is independent of the first circuit.

4. The secondary side waste heat removal system for a small marine pressurized water reactor according to claim 1, characterized in that: The steam generator of the first circuit and the steam generator of the second circuit are located in a containment vessel.

5. The secondary side waste heat removal system for a small marine pressurized water reactor according to any one of claims 1 to 4, characterized in that: The design pressure of the secondary side waste heat removal system of the marine small pressurized water reactor is lower than the pressure of the primary circuit.

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