Direct injection safety system for a reactor pressure vessel

Abstract

The application discloses a reactor pressure vessel direct injection safety system, which comprises a first water injection pipeline and / or a second water injection pipeline; the first water injection pipeline is arranged in the upper head of the reactor pressure vessel, the input end of the first water injection pipeline is located outside the reactor pressure vessel and is connected to a coolant source, the output end of the first water injection pipeline is located inside the reactor pressure vessel and extends to the core region through the upper support plate of the core, and the output end of the first water injection pipeline can directly output the coolant to the core region, thereby improving the core cooling efficiency; the second water injection pipeline is arranged in the reactor pressure vessel, the input end of the second water injection pipeline is located outside the reactor pressure vessel and is connected to the coolant source, the output end of the second water injection pipeline is located inside the reactor pressure vessel and extends to the downcomer of the reactor pressure vessel at least, and the output end of the second water injection pipeline can directly output the coolant from the downcomer, thereby promoting more coolant to flow from the lower support plate of the core to the core region and playing a function of cooling the core.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear power plant safety facilities, and particularly relates to a reactor pressure vessel direct injection safety system. BACKGROUND

[0002] The primary system of a nuclear reactor mainly functions to transfer the heat generated in the reactor. A large amount of heat energy is generated in the nuclear fuel in the process of fission, and the primary system is responsible for taking the heat out of the reactor to prevent the nuclear fuel from overheating and to avoid damage or melting of the fuel elements. The loss of primary coolant accident of a nuclear reactor is the main condition that causes the fuel assemblies in the reactor core to heat up, melt and release a large amount of radioactivity. After the loss of coolant accident in the reactor core, the core can be exposed, the fuel cladding can be damaged, the core assemblies can heat up and melt, the core components can be degraded, and eventually the core can be melted. If the decay heat generated by the core melt cannot be removed in time, the lower head of the reactor pressure vessel can be melted through, thereby causing the risk of radioactive material being released into the environment.

[0003] The main function of the reactor safety injection system is to continuously supply water to the primary loop of the reactor when a break occurs in the primary loop pipe to lose coolant, cool the core fuel assemblies, reestablish the core water level, and limit the temperature rise of the fuel assemblies. The existing reactor safety injection system is usually connected to the cold and hot main pipes of the reactor pressure vessel to achieve the following functions: (1) when the break position is on the hot pipe side of the main pipe: the coolant of the safety injection system is injected from the cold pipe section of the main pipe, and then cools and flows through the process of the reactor pressure vessel descending section - reactor pressure vessel lower head - flow distributor - lower support plate - core fuel assembly - upper support plate - hot pipe section; (2) when the break position is on the cold pipe side of the main pipe: the coolant of the safety injection system is injected from the hot pipe section of the main pipe, and then cools and flows in the reverse direction through the process of hot pipe section - upper support plate - core fuel assembly - lower support plate - flow distributor - reactor pressure vessel lower head - reactor pressure vessel descending section - cold pipe section. In this flow path, a large amount of coolant directly bypasses the reactor pressure vessel without flowing to the core, resulting in a large amount of coolant not effectively performing the function of cooling the core, and the actual cooling efficiency is low. Especially when the break size is large, the core cannot be effectively cooled. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a reactor pressure vessel direct injection safety system to improve the efficiency of cooling the core in the event of a loss of coolant accident of the reactor.

[0005] The technical scheme adopted by the present application to solve its technical problems is: a reactor pressure vessel direct injection safety system is provided, which comprises a first water injection pipeline and / or a second water injection pipeline; the first water injection pipeline is arranged in the upper head of the reactor pressure vessel, the input end of the first water injection pipeline is located outside the reactor pressure vessel and is connected to a coolant source, and the output end of the first water injection pipeline is located inside the reactor pressure vessel and extends to the core region through the upper core support plate; the second water injection pipeline is arranged in the reactor pressure vessel, the input end of the second water injection pipeline is located outside the reactor pressure vessel and is connected to a coolant source, and the output end of the second water injection pipeline is located inside the reactor pressure vessel and extends to at least the lower section of the reactor pressure vessel.

[0006] In some embodiments, the first water injection pipeline comprises a closed pipe section and / or an open pipe section located in the core region.

[0007] In some embodiments, the material of the closed pipe section has a melting point less than or equal to the melting point of the material of the fuel rod cladding tube in the core region.

[0008] In some embodiments, at least part of the first water injection pipeline is arranged in a spacer grid for fixing fuel rod assemblies.

[0009] In some embodiments, the first water injection pipeline comprises a water injection main pipe, a first flow divider and a water injection pipe bundle; the first flow divider and the water injection pipe bundle are located inside the reactor pressure vessel, the water injection main pipe is arranged in the upper head of the reactor pressure vessel, one end of the water injection main pipe is located outside the reactor pressure vessel and is connected to a coolant source, the other end of the water injection main pipe is located inside the reactor pressure vessel, the first flow divider is connected between the other end of the water injection main pipe and the water injection pipe bundle, and the water injection pipe bundle extends to the core region through the upper core support plate.

[0010] In some embodiments, the second water injection pipeline is arranged in the side wall of the reactor pressure vessel, and the height of the interface of the second water injection pipeline on the side wall of the reactor pressure vessel is lower than the height of the cold pipe section and the hot pipe section on the side wall of the reactor pressure vessel.

[0011] In some embodiments, the second injection line comprises a first pipe and a second pipe connected together, the first pipe being located outside the reactor pressure vessel and connected to a coolant source, the second pipe being located inside the reactor pressure vessel; the second pipe comprises a first pipe section and a second pipe section, the first pipe section being connected between the first pipe and the second pipe section, the first pipe section being arranged on an inner wall surface of the reactor pressure vessel and extending along a downcomer section of the reactor pressure vessel to a lower head of the reactor pressure vessel, the second pipe section being arranged through a lower core support plate.

[0012] In some embodiments, along a circumferential direction of the reactor pressure vessel, the interface of the second injection line on the side wall of the reactor pressure vessel is located at an intermediate position between the cold pipe section and the hot pipe section.

[0013] In some embodiments, the second injection line is arranged through the lower head of the reactor pressure vessel, one end of the second injection line inside the reactor pressure vessel being arranged through the lower core support plate.

[0014] In some embodiments, the reactor pressure vessel direct injection safety system further comprises a first active injection unit and / or a first passive injection unit, the first passive injection unit comprising a plurality of first injection tanks, the input end of the first injection line being connected to the first active injection unit and / or the first injection tanks.

[0015] In some embodiments, the reactor pressure vessel direct injection safety system further comprises a second active injection unit and / or a second passive injection unit, the second passive injection unit comprising a plurality of second injection tanks, the input end of the second injection line being connected to the second active injection unit and / or the second injection tanks.

[0016] The present application has at least the following beneficial effects: since the output end of the first water injection pipeline is located inside the reactor pressure vessel and extends to the core region through the upper core support plate, in the event of a loss of coolant accident, the output end of the first water injection pipeline can be directly positioned to the core region and directly output coolant to the core region, which can ensure that most of the coolant can pass through the core to cool the core, reduce the temperature of the core in the first time, prevent the core from heating too fast, and thus improve the cooling efficiency of the core; since the output end of the second water injection pipeline is located inside the reactor pressure vessel and extends to the lower section of the reactor pressure vessel, the output end of the second water injection pipeline can directly output coolant from the lower section, and the output end of the second water injection pipeline is closer to the lower core support plate relative to the cold pipe section and the hot pipe section, which increases the power of the coolant flowing from the lower section to the lower core support plate, can promote more coolant to flow from the lower core support plate to the core region to cool the core, reduce the temperature of the core in the first time, prevent the core from heating too fast, and thus improve the cooling efficiency of the core. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the present application, the present application will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0018] Figure 1 is a structural schematic diagram of a reactor safety injection system in the prior art;

[0019] Figure 2 is a structural schematic diagram of another reactor safety injection system in the prior art;

[0020] Figure 3 is a structural schematic diagram of a reactor pressure vessel direct injection safety system of the first embodiment of the present application;

[0021] Figure 4 is a structural schematic diagram of a reactor pressure vessel direct injection safety system of the second embodiment of the present application;

[0022] Figure 5 is a top view structural schematic diagram of a reactor pressure vessel direct injection safety system of some embodiments of the present application;

[0023] Figure 6 is a structural schematic diagram of a reactor pressure vessel direct injection safety system of the third embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to have a more clear understanding of the technical features, objectives and effects of the present application, the specific embodiments of the present application will be described in detail with reference to the drawings.

[0025] Please refer to Figure 1 and Figure 2, shows the coolant flow path of two existing reactor safety injection systems. The space between the upper core support plate 16 and the lower core support plate 17 is the core region 19, which contains the core including a plurality of fuel assemblies. Under normal operating conditions, the coolant of the primary loop enters the reactor pressure vessel 1 from the cold leg section 11 of the main pipe, the coolant in the reactor pressure vessel 1 submerges the core, and the coolant after heat exchange with the core flows out from the hot leg section 12 of the main pipe to take away the heat of the core. In the event of a primary loop pipe break accident, the coolant flows out in large quantities from the break, the water level of the coolant in the reactor pressure vessel 1 will gradually decrease, and the core will gradually be exposed to cause its temperature to rise rapidly.

[0026] As shown in Figure 1 , one of the existing reactor safety injection systems is connected to the cold leg section 11 of the reactor pressure vessel 1. When a medium or large size break occurs in the reactor primary loop and the break position is on the hot leg side (left side in the figure) of the main pipe, the coolant of the reactor safety injection system is injected from the cold leg section 11 of the main pipe, and then flows through the downcomer 18 inside the lower head 14 of the reactor pressure vessel 1, the flow distributor, the lower core support plate 17, the core region 19, the upper core support plate 16, and the hot leg section 12 of the main pipe, as shown by the dashed line and arrow. Figure 1 As can be seen from the schematic coolant flow path, after the coolant is injected from the cold leg section 11 and reaches the position of the lower head 14 through the right side downcomer 18, only part of the coolant flows through the path of the lower core support plate 17, the core region 19, the upper core support plate 16, and the hot leg section 12 to perform the function of cooling the core; the other part of the coolant directly bypasses the left side downcomer 18 to flow to the hot leg section 12 without performing the function of cooling the core. Therefore, under accident conditions, part of the coolant injected by the reactor safety injection system into the reactor pressure vessel 1 does not perform the function of cooling the core, and the actual cooling efficiency is low.

[0027] As shown in Figure 2 , one of the existing reactor safety injection systems is connected to the hot leg section 12 of the main pipe of the reactor pressure vessel 1. When a medium or large size break occurs in the reactor primary loop and the break position is on the cold leg side (right side in the figure) of the main pipe, the coolant of the reactor safety injection system is injected from the hot leg section 12 of the main pipe, and then flows through the downcomer 18 inside the lower head 14 of the reactor pressure vessel 1, the flow distributor, the lower core support plate 17, the core region 19, the upper core support plate 16, and the cold leg section 11 of the main pipe, as shown by the dashed line and arrow. Figure 2As shown in the schematic coolant flow path, after the coolant is injected from the heat pipe section 12 and reaches the lower head 14 via the descending section 18 on the left, only a portion of the coolant flows along the path of lower core support plate 17 – core region 19 – upper core support plate 16 – cold pipe section 11, performing the function of cooling the core; the other portion of the coolant bypasses directly from the descending section 18 on the right to the heat pipe section 12, without performing the function of cooling the core. Therefore, under accident conditions, a portion of the coolant injected into the reactor pressure vessel 1 by the reactor safety injection system does not perform the function of cooling the core, resulting in a low actual cooling efficiency.

[0028] like Figure 3 As shown, an embodiment of the reactor pressure vessel direct injection safety system provided by the present invention includes a first water injection line 2 and a second water injection line 3. The first water injection line 2 and the second water injection line 3 can operate independently of each other, injecting coolant into the reactor pressure vessel 1 during a primary coolant loss-of-coolant accident to cool the reactor core. In other embodiments, the first water injection line 2 and the second water injection line 3 can be selectively provided; that is, only the first water injection line 2 or only the second water injection line 3 can be provided.

[0029] The first water injection pipe 2 passes through the upper head 13 of the reactor pressure vessel 1. The inlet of the first water injection pipe 2 is located outside the reactor pressure vessel 1 and is connected to a coolant source. The coolant source can be water, liquid metal, etc. The outlet of the first water injection pipe 2 is located inside the reactor pressure vessel 1 and extends through the upper core support plate 16 to the core region 19. That is, after passing through the upper head 13, the first water injection pipe 2 extends directly downward from the upper core support plate 16 to the core region 19. In this way, under the accident condition of coolant loss, the output end of the first water injection pipeline 2 can be directly located to the core area 19 and directly output coolant to the core area 19. The coolant first passes through the core area 19 and then flows from the lower support plate 17, lower end cap 14 and descending section 18 to the cold pipe section 11 and hot pipe section 12 of the main pipeline. Therefore, it can ensure that most of the coolant can pass through the core area 19, play the role of cooling the core, reduce the core temperature as soon as possible, prevent the core from heating up too quickly, and thus improve the cooling efficiency of the core.

[0030] After a loss-of-coolant accident occurs in a nuclear reactor, and the breach is relatively large, the water level in the core region 19 gradually decreases, and the upper region of the core heats up at a faster rate. Therefore, the output end of the first water injection pipe 2 can be located in the upper part of the core region 19, so that the coolant output from the first water injection pipe 2 can quickly reach the middle and upper parts of the fuel assemblies in the core region 19, providing rapid, effective, and timely cooling to the high-temperature fuel assemblies.

[0031] The second water injection pipeline 3 penetrates the side wall 15 or the lower head 14 of the reactor pressure vessel 1. The input end of the second water injection pipeline 3 is located outside the reactor pressure vessel 1 and is connected to the coolant source, and the output end of the second water injection pipeline 3 is located inside the reactor pressure vessel 1 and extends at least to the downcomer 18 of the reactor pressure vessel 1. In this way, the output end of the second water injection pipeline 3 can directly output the coolant from the downcomer 18, and the output end of the second water injection pipeline 3 is closer to the lower core support plate 17 than the cold leg 11 and the hot leg 12, which increases the power of the coolant flowing from the downcomer 18 to the lower core support plate 17, and can promote more coolant to flow from the lower core support plate 17 to the core region 19 in turn, and then from the core region 19 to the cold leg 11 and the hot leg 12 of the main pipe, thereby cooling the core, reducing the temperature of the core in the first time, preventing the core from heating too fast, and thereby improving the cooling efficiency of the core.

[0032] Further, in some embodiments of the second water injection pipeline 3, the output end of the second water injection pipeline 3 can extend at least between the lower core support plate 17 and the lower head 14. In this way, the output end of the second water injection pipeline 3 can be directly positioned near the lower core support plate 17, and directly output the coolant near the lower core support plate 17, so that most of the coolant flows from the lower core support plate 17 to the core region 19 in turn, and then from the core region 19 to the cold leg 11 and the hot leg 12 of the main pipe, thereby cooling the core, reducing the temperature of the core in the first time, preventing the core from heating too fast, and thereby improving the cooling efficiency of the core.

[0033] As Figure 3As shown, in the first embodiment of the second water injection pipeline 3, the second water injection pipeline 3 is arranged in the side wall 15 of the reactor pressure vessel 1. Moreover, the height of the interface of the second water injection pipeline 3 on the side wall 15 of the reactor pressure vessel 1 is lower than the height of the cold leg 11 and the hot leg 12 on the side wall 15 of the reactor pressure vessel 1, so as to shorten the path of the coolant flowing through the downcomer 18 and make the coolant flow quickly from the position lower than the cold leg 11 and the hot leg 12 to the output end of the second water injection pipeline 3 and enter the core region 19 from the lower core support plate 17. In the first embodiment, the second water injection pipeline 3 comprises a first pipeline 31 and a second pipeline 32 connected with each other, the first pipeline 31 is located outside the reactor pressure vessel 1 and connected to the coolant source, and the second pipeline 32 is located inside the reactor pressure vessel 1. The second pipeline 32 comprises a first pipe section 321 and a second pipe section 322, and the first pipe section 321 is connected between the first pipeline 31 and the second pipe section 322. The first pipe section 321 is arranged on the inner wall surface of the reactor pressure vessel 1 and extends along the downcomer 18 of the reactor pressure vessel 1 to the lower head 14. The second pipe section 322 is arranged in the lower core support plate 17. The end of the second pipe section 322 away from the first pipe section 321 is the output end of the second water injection pipeline 3. That is, the output end of the second water injection pipeline 3 is arranged in the lower core support plate 17 and can further extend into the core region 19. Thus, the coolant flows through the first pipeline 31, the first pipe section 321 and the second pipe section 322 in sequence and then enters the core region 19 from the lower core support plate 17 to directly cool the core of the core region 19. The coolant flowing through the core region 19 flows out from the hot leg 12 and the cold leg 11 above. In this embodiment, the flow path of the coolant is limited to the first pipe section 321 and the second pipe section 322 inside the reactor pressure vessel 1, so that the coolant directly flows along the inner wall surface of the reactor pressure vessel 1 and the lower core support plate 17 into the core region 19, and the coolant of the second water injection pipeline 3 can directly flow through the core region 19 to cool the core with high efficiency.

[0034] As Figure 4As shown, in the second embodiment of the second water injection line 3, similar to the first embodiment, the second water injection line 3 passes through the side wall 15 of the reactor pressure vessel 1. Furthermore, the height of the interface of the second water injection line 3 on the side wall 15 of the reactor pressure vessel 1 is lower than the height of the cold pipe section 11 and the hot pipe section 12 on the side wall 15 of the reactor pressure vessel 1. The difference between the second embodiment and the first embodiment is that the output end of the second water injection line 3 is located between the lower core support plate 17 and the lower head 14. That is, the output end of the second water injection line 3 may not pass through the lower core support plate 17. Since the output end of the second water injection pipe 3 is located between the lower core support plate 17 and the lower head 14, and the output end of the second water injection pipe 3 is also very close to the lower core support plate 17, it can directly output coolant to the vicinity of the lower core support plate 17. Although a small portion of the coolant flows sequentially from the area between the lower core support plate 17 and the lower head 14 to the descending section 18 and the hot pipe section 12 (cold pipe section 11), most of the coolant can flow sequentially from the lower core support plate 17 to the core area 19, and then from the core area 19 to the cold pipe section 11 and the hot pipe section 12 of the main pipe, thus achieving the function of accurately and effectively cooling the core.

[0035] like Figure 5 As shown, in some embodiments, when the second water injection pipe 3 passes through the side wall 15 of the reactor pressure vessel 1, the interface of the second water injection pipe 3 on the side wall 15 of the reactor pressure vessel 1 is located at the midpoint between the cold pipe section 11 and the hot pipe section 12 along the circumference of the reactor pressure vessel 1. That is, the circumferential distance H1 between the interface of the second water injection pipe 3 on the side wall 15 of the reactor pressure vessel 1 and the cold pipe section 11 is equal to the circumferential distance H2 between the interface of the second water injection pipe 3 on the side wall 15 of the reactor pressure vessel 1 and the hot pipe section 12. In this way, the interface of the second water injection pipe 3 on the side wall 15 of the reactor pressure vessel 1 is located at the position furthest from the cold pipe section 11 and the hot pipe section 12 in the circumferential direction, which can minimize the adverse impact on the in-core flow field during normal reactor operation.

[0036] like Figure 5 As shown, in some embodiments, the section of the second water injection pipe 3 located inside the reactor pressure vessel 1 includes a semi-circular pipe, which, together with the inner wall of the reactor pressure vessel 1, defines a pipe cavity. Alternatively, in other embodiments, the section of the second water injection pipe 3 located inside the reactor pressure vessel 1 includes a circular pipe, which is disposed in close contact with the inner wall of the reactor pressure vessel 1. For example, in the first embodiment, the first section 321 of the second pipe 32 may include a semi-circular pipe. In other embodiments, a portion of the second water injection pipe 3 may also be located on the outer wall of the reactor pressure vessel 1, extending along the outer wall to the lower end cap 14 and then penetrating into the interior of the reactor pressure vessel 1.

[0037] likeFigure 6 As shown, the difference between the third embodiment of the second water injection pipeline 3 and the first embodiment and the second embodiment is that the second water injection pipeline 3 is arranged in the lower head 14 of the reactor pressure vessel 1, and the end of the second water injection pipeline 3 inside the reactor pressure vessel 1 is arranged in the lower core support plate 17. That is, the second water injection pipeline 3 directly penetrates the lower head 14 from bottom to top, and the output end of the second water injection pipeline 3 penetrates the lower core support plate 17. Thus, the coolant output by the output end of the second water injection pipeline 3 directly flows through the core region 19, and then flows from the core region 19 to the hot pipe section 12 and the cold pipe section 11, thereby precisely and effectively cooling the core.

[0038] Any embodiment of the first embodiment, the second embodiment, and the third embodiment that is not described in detail can be arranged with reference to other embodiments, which will not be described here.

[0039] In some embodiments, the first water injection pipeline 2 includes a closed pipe section and / or an open pipe section inside the core region 19. That is, the first water injection pipeline 2 can include one or both of the closed pipe section and the open pipe section. The open pipe section refers to the output end of the first water injection pipeline 2 inside the core region 19 being open, and the coolant can directly flow out of the output end to cool the core. The closed pipe section refers to the output end of the first water injection pipeline 2 inside the core region 19 being closed, and only after the closed pipe section is melted by high temperature, the coolant can flow out. The advantage of arranging the closed pipe section is that when the coolant in the core region 19 is excessively lost in the accident condition, causing the temperature in the core region 19 to rise, the closed pipe section is automatically released after being melted, and the position where the closed pipe section is melted corresponds to the position with the highest temperature in the core region 19. Thus, the highest temperature area in the core region 19 can be automatically captured through the melting point of the closed pipe section, and the coolant is released to the highest temperature area in the first time, thereby achieving more precise cooling in the core region 19.

[0040] Further, the melting point of the material of the closed tube segment can be less than or equal to the melting point of the material of the fuel rod cladding tube in the core region 19. In this way, when the coolant in the core region 19 is excessively drained in an accident condition, causing the temperature in the core region 19 to rise, the closed tube segment in the core region 19 is melted through before the fuel rod cladding tube or at the same time as the fuel rod cladding tube, so that the coolant can be released in time and in advance to cool the core before the core melts, reducing the risk of high-temperature melting of the core. Specifically, the closed tube segment can be made of an alloy with a lower melting point (about 1000°C), such as an aluminum alloy. When the temperature of the high-temperature region of the fuel assembly in the core region 19 exceeds 1000°C, the closed tube segment in the corresponding region will melt, and the cooling water can quickly flow out of the melted closed tube segment and cool the surrounding high-temperature fuel assembly region, achieving rapid flooding of the core. Both the closed tube segment and the open tube segment can be made of the same material as the fuel assembly and the in-core component, typically zirconium alloy or stainless steel alloy. When the closed tube segment and the fuel rod cladding tube are made of different materials, if the material of the closed tube segment is a new material that has not been tested and verified, the material needs to be tested and verified before it can be used in the core region 19. When the material of the closed tube segment is the same as that of the fuel rod cladding tube, the melting point of the closed tube segment is equal to that of the fuel rod cladding tube in the core region 19, and the closed tube segment and the fuel rod cladding tube melt at the same time, which can accurately capture the location with the highest temperature in the core region 19, and the material of the closed tube segment (i.e., the material of the fuel rod cladding tube) does not need to be verified before use.

[0041] When the first water injection pipeline 2 includes the open tube segment and the closed tube segment, the open tube segment can directly release the coolant to the core region 19 without distinction, while the closed tube segment automatically locates the highest temperature region in the core region 19 through its melting point to release the coolant. The combination of the open tube segment and the closed tube segment can more comprehensively and accurately cool the core in the core region 19.

[0042] In some embodiments, at least part of the first water injection pipeline 2 is fixed by being passed through a positioning grid for fixing the fuel rod assembly. That is, only part of the tube segment of the first water injection pipeline 2 can be passed through the positioning grid for fixing, or all of the tube segments of the first water injection pipeline 2 can be passed through the positioning grid for fixing. That is, part of the fuel rod assembly on the existing positioning grid in the reactor pressure vessel 1 can be replaced by the tube segment of the first water injection pipeline 2. In this way, the first water injection pipeline 2 can be fixed by being limited by the existing positioning grid in the reactor pressure vessel 1, preventing the first water injection pipeline 2 from vibrating greatly under normal operating conditions of the reactor.

[0043] Furthermore, the first water injection pipe 2 can be located in the middle area of ​​the support plate 16 on the reactor core. The fuel rod assemblies are located around the first water injection pipe 2. The first water injection pipe 2, which is fixed by the positioning grid, will occupy part of the placement space of the fuel rod assemblies. However, under normal design conditions, the number of fuel rod assemblies can be as high as tens of thousands. As long as the number of pipe segments of the first water injection pipe 2 is much smaller than the number of fuel rod assemblies, and the diameter of the pipe segments of the first water injection pipe 2 is much smaller than the diameter of the fuel rod assemblies, then the space occupied by the first water injection pipe 2 is relatively small, and the impact is not significant.

[0044] like Figure 3 As shown, in some embodiments, the first water injection line 2 includes a water injection header 21, a first distributor 22, and a water injection tube bundle 23. The first distributor 22 and the water injection tube bundle 23 are located inside the reactor pressure vessel 1. The water injection header 21 passes through the upper head 13 of the reactor pressure vessel 1. One end of the water injection header 21 is located outside the reactor pressure vessel 1 and connected to the coolant source, while the other end of the water injection header 21 is located inside the reactor pressure vessel 1. The first distributor 22 is connected between the other end of the water injection header 21 and the water injection tube bundle 23, which extends through the core support plate 16 to the core region 19. The water injection tube bundle 23 includes multiple closed and / or open pipe sections located within the core region 19. The different pipe sections may be made of the same or different materials. The water injection header 21 is connected to the coolant source, and the coolant can flow sequentially through the water injection header 21, the first distributor 22, and the water injection tube bundle 23 to reach the core region 19. The coolant is distributed through the first distributor 22, which uniformly or proportionally distributes the coolant in the water injection header 21 into multiple output pipes of the water injection tube bundle 23. In this way, only one water injection header 21 needs to pass through the reactor pressure vessel 1, minimizing the number of pipes crossing the reactor pressure vessel 1. Using the water injection tube bundle 23 to inject coolant into the core region 19 in multiple sections effectively avoids situations where partial pipe blockage prevents effective water injection.

[0045] In some embodiments, there can be multiple second pipe sections 322. Providing multiple second pipe sections 322 penetrating the core support plate 17 to inject coolant into the core region 19 can effectively prevent partial pipe blockage from hindering effective water injection. The second water injection pipeline 3 may also include a second distributor (not shown), located between the first pipe section 321 and the second pipe section 322 of the second pipeline 32, for uniformly or proportionally distributing the coolant in the first pipe section 321 into the multiple second pipe sections 322.

[0046] like Figure 3As shown, in some embodiments, the reactor pressure vessel direct injection safety system further includes a first active water injection unit 41 and / or a first passive water injection unit 42. That is, the first active water injection unit 41 and the first passive water injection unit 42 can be selected individually or simultaneously. The first passive water injection unit 42 includes a plurality of first water injection tanks 420 and a first valve 421 connected to the first water injection tanks 420. When the first active water injection unit 41 and the first passive water injection unit 42 are selected simultaneously, the input end of the first water injection pipeline 2 is connected to the first active water injection unit 41 and the first water injection tank 420, respectively. When only the first active water injection unit 41 is selected, the input end of the first water injection pipeline 2 is connected to the first active water injection unit 41. When only the first passive water injection unit 42 is selected, the input end of the first water injection pipeline 2 is connected to the first passive water injection unit 42. Specifically, as Figure 3 In the illustrated embodiment, the first passive water injection unit 42 may include two first water injection tanks 420. One of the first water injection tanks 420 is a medium-pressure water injection tank, and the other is a low-pressure water injection tank. The water pressure inside the medium-pressure water injection tank is greater than that inside the low-pressure water injection tank. When the pressure after the primary circuit of the nuclear reactor loses water and drops below the water pressure inside the medium-pressure water injection tank (generally around 4.0 MPa), the cooling water in the medium-pressure water injection tank will be rapidly injected into the core region 19 through the first water injection pipeline 2 to passively cool the core. The water injection flow rate can exceed 100 m³ / h. 3 / h. Under extremely severe loss-of-coolant accident conditions, even after the intermediate-pressure injection tank is filled with water, the reactor core may still be unable to be cooled, and some fuel assemblies may melt down over a large area. When the pressure in the primary circuit of the nuclear reactor drops below the water pressure inside the low-pressure injection tank after loss of coolant, the cooling water in the low-pressure injection tank will be rapidly injected into the core region 19 through the first injection pipe 2. At this time, the injection flow rate can exceed 50 m³ / h. 3 / h. The first active water injection unit 41 has a water pump that can actively inject coolant fluid at a higher pressure (e.g., exceeding 4 MPa) into the first water injection line 2 to actively cool the reactor core.

[0047] like Figure 6 As shown, in some embodiments, the reactor pressure vessel direct injection safety system further includes a second active water injection unit 51 and / or a second passive water injection unit. The second passive water injection unit includes a plurality of second water injection tanks 520 and a second valve 521 connected to the second water injection tanks 520. One end of the second water injection pipeline 3 located outside the reactor pressure vessel 1 is connected to the second active water injection unit 51 and / or the second water injection tank 520. More specific details regarding the second active water injection unit 51 can be found in the configuration of the first active water injection unit 41, and more specific details regarding the second passive water injection unit can be found in the configuration of the first passive water injection unit 42, and will not be repeated here.

[0048] It can be understood that the above embodiments only express the preferred embodiments of the present application, which are described more specifically and in detail, but cannot be understood as a limitation to the patent scope of the present application; it should be pointed out that the above technical features can be freely combined without departing from the concept of the present application for those skilled in the art, and several modifications and improvements can be made, which all belong to the protection scope of the present application; therefore, any equivalent transformation and modification made to the patent claim scope of the present application shall belong to the coverage of the patent claim of the present application.

Claims

1. A reactor pressure vessel direct injection safety system characterized by, The first water injection pipeline (2) and the second water injection pipeline (3) are provided. The first water injection pipeline (2) penetrates the upper head (13) of the reactor pressure vessel (1), the input end of the first water injection pipeline (2) is located outside the reactor pressure vessel (1) and is connected to a coolant source, and the output end of the first water injection pipeline (2) is located inside the reactor pressure vessel (1) and extends to the core region (19) through the upper core support plate (16). The second water injection pipeline (3) penetrates the reactor pressure vessel (1), the input end of the second water injection pipeline (3) is located outside the reactor pressure vessel (1) and is connected to a coolant source, and the output end of the second water injection pipeline (3) is located inside the reactor pressure vessel (1) and extends at least to the lower section (18) of the reactor pressure vessel (1). The first water injection pipeline (2) comprises a water injection main pipe (21), a first flow divider (22) and a water injection pipe bundle (23). The first flow divider (22) and the water injection pipe bundle (23) are located inside the reactor pressure vessel (1), the water injection main pipe (21) penetrates the upper head (13) of the reactor pressure vessel (1), one end of the water injection main pipe (21) is located outside the reactor pressure vessel (1) and is connected to a coolant source, the other end of the water injection main pipe (21) is located inside the reactor pressure vessel (1), the first flow divider (22) is connected between the other end of the water injection main pipe (21) and the water injection pipe bundle (23), and the water injection pipe bundle (23) extends to the core region (19) through the upper core support plate (16). The second water injection pipeline (3) comprises a first pipe (31) and a second pipe (32) connected in series, the first pipe (31) is located outside the reactor pressure vessel (1) and is connected to a coolant source, and the second pipe (32) is located inside the reactor pressure vessel (1). The second pipe (32) comprises a first pipe section (321) and a second pipe section (322), the first pipe section (321) is connected between the first pipe (31) and the second pipe section (322), the first pipe section (321) is arranged on the inner wall surface of the reactor pressure vessel (1) and extends along the lower section (18) of the reactor pressure vessel (1) to the lower head (14) of the reactor pressure vessel (1), and the second pipe section (322) is a plurality of pipe sections and penetrates the lower core support plate (17).

2. The reactor pressure vessel direct injection safety system in accordance with claim 1, characterized in that, The first water injection pipeline (2) comprises a closed pipe section and / or an open pipe section located in the core region (19).

3. The reactor pressure vessel direct injection safety system in accordance with claim 2, characterized by, The closed pipe section is made of a material whose melting point is less than or equal to the melting point of the material used for the fuel rod cladding tube in the core region (19).

4. The reactor pressure vessel direct injection safety system in accordance with claim 1, characterized by, At least part of the first water injection pipeline (2) is fixed by penetrating a positioning grid for fixing fuel rod assemblies.

5. The reactor pressure vessel direct injection safety system in accordance with claim 1, characterized by, The second water injection pipeline (3) is arranged in the side wall (15) of the reactor pressure vessel (1), and the height of the interface of the second water injection pipeline (3) on the side wall (15) of the reactor pressure vessel (1) is lower than the height of the cold pipe section (11) and the hot pipe section (12) on the side wall (15) of the reactor pressure vessel (1).

6. The reactor pressure vessel direct injection safety system in accordance with claim 5, characterized in that, Along the circumference of the reactor pressure vessel (1), the interface of the second water injection pipeline (3) on the side wall (15) of the reactor pressure vessel (1) is located in the middle position between the cold pipe section (11) and the hot pipe section (12).

7. The reactor pressure vessel direct injection safety system in accordance with claim 1, characterized by, The second water injection pipeline (3) is arranged in the lower head (14) of the reactor pressure vessel (1), and the end inside the reactor pressure vessel (1) is arranged in the lower core support plate (17).

8. The reactor pressure vessel direct injection safety system of any one of claims 1 to 7, wherein, The reactor pressure vessel direct injection safety system further comprises a first active water injection unit (41) and / or a first passive water injection unit (42), the first passive water injection unit (42) comprises a plurality of first water injection tanks (420), and the input end of the first water injection pipeline (2) is connected to the first active water injection unit (41) and / or the first water injection tank (420).

9. The reactor pressure vessel direct injection safety system of any one of claims 1 to 7, wherein, The reactor pressure vessel direct injection safety system further comprises a second active water injection unit (51) and / or a second passive water injection unit, the second passive water injection unit comprises a plurality of second water injection tanks (520), and the input end of the second water injection pipeline (3) is connected to the second active water injection unit (51) and / or the second water injection tank (520).

Images