Reactor pressure vessel direct injection safety system

Abstract

The invention discloses a direct injection safety system for a reactor pressure vessel. The direct injection safety system comprises a first water injection pipeline and / or a second water injection pipeline, the first water injection pipeline penetrates through an upper seal head of the reactor pressure vessel, the input end of the first water injection pipeline is located outside the reactor pressure vessel and connected to a coolant source, and the output end of the first water injection pipeline is located in the reactor pressure vessel and penetrates through the reactor core upper supporting plate to extend to a reactor core area; the output end of the first water injection pipeline can be directly positioned to a reactor core area to output a coolant, so that the reactor core cooling efficiency is improved; the second water injection pipeline penetrates through the reactor pressure vessel, the input end of the second water injection pipeline is located outside the reactor pressure vessel and connected to the coolant source, the output end of the second water injection pipeline is located in the reactor pressure vessel and at least extends to the descending section of the reactor pressure vessel, and the output end of the second water injection pipeline can directly output coolant from the descending section. And more coolants are promoted to flow to the reactor core area from the reactor core lower support plate, so that the function of cooling the reactor core is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of safety facilities of nuclear power plants, and in particular to a direct injection safety system for a reactor pressure vessel. Background Art

[0002] The primary loop system of a nuclear reactor is mainly used to transfer the heat generated in the reactor. Nuclear fuel generates a large amount of heat energy during the fission process. The primary loop system is responsible for taking this heat out of the reactor to prevent the nuclear fuel from overheating and to avoid damage or melting of the fuel elements. The accident of a nuclear reactor losing primary loop cooling is the main condition that causes the reactor core fuel assemblies to heat up, melt, and release a large amount of radioactivity. After the nuclear reactor core loses cooling, the core may be exposed, the fuel cladding may be damaged, the core assemblies may heat up and melt, the core components may be degraded, and eventually the core may melt. In this process, if the decay heat generated by the core melt cannot be promptly discharged, the lower head of the reactor pressure vessel may be melted through, resulting in the risk of radioactive substances being released into the environment.

[0003] The main function of the reactor safety injection system is to continuously replenish water to the reactor primary loop when a reactor primary loop pipe breaks and loses coolant, cool the core fuel assembly, re-establish the core water level, and limit the temperature rise of the fuel assembly. The existing reactor safety injection system is usually connected to the cold and hot main pipes of the reactor pressure vessel in order to achieve the following functions: (1) When the rupture is on the hot pipe side of the main pipe: the coolant of the safety water injection system is injected from the cold pipe section of the main pipe, and then flows through 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 rupture is on the cold pipe side of the main pipe: the coolant of the safety water injection system is injected from the hot pipe section of the main pipe, and then flows through the 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 the opposite direction. In this flow path, a large amount of coolant will flow out of the reactor pressure vessel directly through the downcomer of the reactor pressure vessel without flowing to the core, resulting in a large amount of coolant failing to effectively perform the function of cooling the core, and the actual cooling efficiency is low. In particular, when the breach size is large, the core cannot be effectively cooled. Summary of the invention

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

[0005] The technical solution adopted by the present invention to solve its technical problems is: to provide a reactor pressure vessel direct injection safety system, which includes a first water injection pipeline and / or a second water injection pipeline; the first water injection pipeline is penetrated through 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 the coolant source, and the output end of the first water injection pipeline is located inside the reactor pressure vessel and extends to the core area through the upper support plate of the core; the second water injection pipeline is penetrated through 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, and the output end of the second water injection pipeline is located inside the reactor pressure vessel and extends to at least the descending section of the reactor pressure vessel.

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

[0007] In some embodiments, the melting point of the material used for the closed tube segment is less than or equal to the melting point of the material used for the fuel rod cladding tubes in the core region.

[0008] In some embodiments, at least a portion of the first water injection pipeline is passed through a spacer grid for fixing the fuel rod assembly for fixation.

[0009] In some embodiments, the first water injection pipeline includes a water injection mother pipe, a first diverter and a water injection tube bundle; the first diverter and the water injection tube bundle are located inside the reactor pressure vessel, the water injection mother pipe is penetrated through the upper head of the reactor pressure vessel, one end of the water injection mother pipe is located outside the reactor pressure vessel and connected to a coolant source, the other end of the water injection mother pipe is located inside the reactor pressure vessel, the first diverter is connected between the other end of the water injection mother pipe and the water injection tube bundle, and the water injection tube bundle extends to the core area through the upper support plate of the core.

[0010] In some embodiments, the second water injection pipeline passes through 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 heights 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 water injection pipeline includes a first pipe and a second pipe connected to each other, the first pipe is located outside the reactor pressure vessel and connected to a coolant source, and the second pipe is located inside the reactor pressure vessel; the second pipe includes a first pipe segment and a second pipe segment, the first pipe segment is connected between the first pipe and the second pipe segment, the first pipe segment is arranged on the inner wall surface of the reactor pressure vessel and extends along the descending section of the reactor pressure vessel to the lower head of the reactor pressure vessel, and the second pipe segment is penetrated through the lower support plate of the core.

[0012] In some embodiments, along the circumference of the reactor pressure vessel, the interface of the second water injection pipeline on the side wall of the reactor pressure vessel is located in the middle position between the cold pipe section and the hot pipe section.

[0013] In some embodiments, the second water injection pipeline is penetrated through the lower head of the reactor pressure vessel, and one end of the second water injection pipeline located inside the reactor pressure vessel is penetrated through the lower support plate of the core.

[0014] In some embodiments, the reactor pressure vessel direct injection safety system also includes a first active water injection unit and / or a first passive water injection unit, the first passive water injection unit includes a plurality of first water injection tanks, and the input end of the first water injection pipeline is connected to the first active water injection unit and / or the first water injection tank.

[0015] In some embodiments, the reactor pressure vessel direct injection safety system also includes a second active water injection unit and / or a second passive water injection unit, the second passive water injection unit includes a plurality of second water injection tanks, and the input end of the second water injection pipeline is connected to the second active water injection unit and / or the second water injection tank.

[0016] The present invention has at least the following beneficial effects: since the output end of the first water injection pipeline is located in the reactor pressure vessel and extends through the upper support plate of the core to the core area, under the accident condition of coolant loss of water, the output end of the first water injection pipeline can be directly positioned at the core area and directly output the coolant to the core area, which can ensure that most of the coolant can pass through the core to play the role of cooling the core, reduce the temperature of the core at the first time, and prevent the core from heating up too quickly, thereby improving the cooling efficiency of the core; since the output end of the second water injection pipeline is located in the reactor pressure vessel and at least extends to the descending section of the reactor pressure vessel, the output end of the second water injection pipeline can directly output the coolant from the descending section, and the output end of the second water injection pipeline is closer to the lower support plate of the core relative to the cold pipe section and the hot pipe section, which increases the power of the coolant flowing from the descending section to the lower support plate of the core, and can promote more coolant to flow from the lower support plate of the core to the core area to play the role of cooling the core, reduce the temperature of the core at the first time, and prevent the core from heating up too quickly, thereby improving the cooling efficiency of the core. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

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

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

[0020] Figure 3 2 is a schematic structural diagram of a reactor pressure vessel direct injection safety system according to a first embodiment of the present invention;

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

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

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

[0024] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0025] Please also read Figure 1 and Figure 2, showing the coolant flow paths of two existing reactor safety injection systems. The space between the core upper support plate 16 and the core lower support plate 17 is the core area 19, which accommodates the core, and the core includes many fuel assemblies. Under normal operating conditions, the coolant of the first circuit enters the reactor pressure vessel 1 from the cold pipe section 11 of the main pipeline, and the coolant in the reactor pressure vessel 1 submerges the core. The coolant after heat exchange with the core flows out from the hot pipe section 12 of the main pipeline to take out the heat of the core. In the event of an accident condition in which a first-circuit pipeline ruptures, a large amount of coolant will be lost from the rupture, the coolant water level in the reactor pressure vessel 1 will gradually drop, and the core will gradually be exposed, causing its temperature to rise rapidly.

[0026] like Figure 1 As shown, an existing reactor safety injection system is connected to the cold pipe section 11 of the reactor pressure vessel 1. When a medium or large-sized rupture occurs in the reactor primary circuit, and the rupture is located on the hot pipe side of the main pipeline (the left side in the figure), as shown by the dotted line and arrow, the coolant of the reactor safety injection system is injected from the cold pipe section 11 of the main pipeline, and then flows through the descending section 18 in the reactor pressure vessel 1 - the inner side of the lower head 14 of the reactor pressure vessel 1 - the flow distributor - the lower core support plate 17 - the core area 19 - the upper core support plate 16 - the hot pipe section 12 of the main pipeline. Figure 1 It can be seen from the schematic coolant flow path that after the coolant is injected from the cold pipe section 11 and reaches the position of the lower head 14 through the right descending section 18, only a part of the coolant flows to the path of the lower core support plate 17 - the core area 19 - the upper core support plate 16 - the hot pipe section 12, and performs the function of cooling the core; the other part of the coolant directly bypasses the left descending section 18 and flows to the hot pipe section 12, and does not perform the function of cooling the core. Therefore, under accident conditions, a part 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, and the actual cooling efficiency is low.

[0027] like Figure 2 As shown, an existing reactor safety injection system is connected to the hot pipe section 12 of the main pipeline of the reactor pressure vessel 1. When a medium or large-sized rupture occurs in the reactor primary circuit, and the rupture is located on the cold pipe side of the main pipeline (the right side in the figure), as shown by the dotted line and arrow, the coolant of the reactor safety injection system is injected from the hot pipe section 12 of the main pipeline, and then flows through the descending section 18 in the reactor pressure vessel 1 - the inner side of the lower head 14 of the reactor pressure vessel 1 - the flow distributor - the lower support plate 17 of the core - the core area 19 - the upper support plate 16 of the core - the cold pipe section 11. Figure 2It can be seen from the schematic coolant flow path that after the coolant is injected from the hot pipe section 12 and reaches the position of the lower head 14 through the left descending section 18, only a part of the coolant flows to the path of the lower core support plate 17 - the core area 19 - the upper core support plate 16 - the cold pipe section 11, and performs the function of cooling the core; the other part of the coolant directly bypasses the right descending section 18 and flows to the hot pipe section 12, and does not perform the function of cooling the core. Therefore, under accident conditions, a part 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, and the actual cooling efficiency is low.

[0028] like Figure 3 As shown, a reactor pressure vessel direct injection safety system according to an embodiment of the present invention includes a first water injection pipeline 2 and a second water injection pipeline 3. The first water injection pipeline 2 and the second water injection pipeline 3 can operate independently of each other, and inject coolant into the reactor pressure vessel 1 under a loss of coolant accident condition in a single-loop coolant, thereby cooling the core. In other embodiments, the first water injection pipeline 2 and the second water injection pipeline 3 can be selectively set, that is, only the first water injection pipeline 2 or only the second water injection pipeline 3 can be set.

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

[0030] After a loss of coolant accident occurs in the nuclear reactor, and the size of the breach is relatively large, the water level in the core area 19 gradually decreases, and the upper area of ​​the core heats up faster. Therefore, further, the output end of the first water injection pipeline 2 can be located in the upper half of the core area 19, so that the coolant output by the first water injection pipeline 2 can quickly reach the middle and upper parts of the fuel assembly in the core area 19, and quickly, effectively and timely cool the high-temperature fuel assembly.

[0031] The second water injection pipeline 3 is arranged through 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 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 descending section 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 descending section 18, and the output end of the second water injection pipeline 3 is closer to the lower support plate 17 of the core relative to the cold pipe section 11 and the hot pipe section 12, which increases the power of the coolant flowing from the descending section 18 to the lower support plate 17 of the core, and can promote more coolant to flow from the lower support plate 17 of the core to the core area 19 in sequence, and then flow from the core area 19 to the cold pipe section 11 and the hot pipe section 12 of the main pipeline, which plays the function of cooling the core, reducing the temperature of the core in the first time, and preventing the core from heating up too fast, thereby improving the cooling efficiency of the core.

[0032] Furthermore, in some embodiments of the second water injection pipeline 3, the output end of the second water injection pipeline 3 can extend at least to 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 the coolant is directly output to the vicinity of the lower core support plate 17, so that most of the coolant flows from the lower core support plate 17 to the core area 19 in sequence, and then flows from the core area 19 to the cold pipe section 11 and the hot pipe section 12 of the main pipeline, which plays the function of cooling the core, reducing the temperature of the core in the first time, and preventing the core from heating up too quickly, thereby improving the cooling efficiency of the core.

[0033] like Figure 3As shown, in the first embodiment of the second water injection pipeline 3, the second water injection pipeline 3 is arranged through 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 pipe section 11 and the hot pipe section 12 on the side wall 15 of the reactor pressure vessel 1, so that the path of the coolant flowing through the descending section 18 can be shortened as much as possible, so that the coolant can flow quickly from a position lower than the cold pipe section 11 and the hot pipe section 12 to the output end of the second water injection pipeline 3 and enter the core area 19 from the lower core support plate 17. In the first embodiment, the second water injection pipeline 3 includes a first pipe 31 and a second pipe 32 connected to each other, the first pipe 31 is located outside the reactor pressure vessel 1 and connected to the coolant source, and the second pipe 32 is located inside the reactor pressure vessel 1. The second pipe 32 includes a first pipe section 321 and a second pipe section 322, and 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 descending section 18 of the reactor pressure vessel 1 to the lower head 14. The second pipe section 322 is penetrated through the lower core support plate 17. The end of the second pipe section 322 away from the first pipe section 321 is also the output end of the second water injection pipeline 3. That is, the output end of the second water injection pipeline 3 is penetrated through the lower core support plate 17 and can further extend into the core area 19. Thus, the coolant flows through the first pipe 31, the first pipe section 321 and the second pipe section 322 in sequence, and then enters the core area 19 from the lower core support plate 17, and directly cools the core of the core area 19. The coolant flowing through the core area 19 flows out from the upper hot pipe section 12 and the cold pipe section 11. In this embodiment, inside the reactor pressure vessel 1, the flow path of the coolant is limited to the first pipe section 321 and the second pipe section 322, so that the coolant directly enters the core area 19 along the inner wall surface of the reactor pressure vessel 1 and the lower core support plate 17, and the coolant of the second water injection pipeline 3 can directly pass through the core area 19, thereby cooling the core with high efficiency.

[0034] like Figure 4As shown, in the second embodiment of the second water injection pipeline 3, the second water injection pipeline 3 is the same as the first embodiment in that it is arranged through 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 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 pipeline 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 pipeline 3 may not be arranged through the lower core support plate 17. Since the output end of the second water injection pipeline 3 is located between the lower core support plate 17 and the lower head 14, the output end of the second water injection pipeline 3 is also very close to the lower core support plate 17, and the coolant can be directly output to the vicinity of the lower core support plate 17. Although a small amount of coolant flows 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) in sequence, most of the coolant can flow from the lower core support plate 17 to the core area 19 in sequence, and then flow from the core area 19 to the cold pipe section 11 and the hot pipe section 12 of the main pipeline, thereby playing the role of accurately and effectively cooling the core.

[0035] like Figure 5 As shown, in some embodiments, when the second water injection pipeline 3 is provided through the side wall 15 of the reactor pressure vessel 1, 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 at the middle position between the cold pipe section 11 and the hot pipe section 12. That is, the circumferential distance H1 between the interface of the second water injection pipeline 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 pipeline 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 pipeline 3 on the side wall 15 of the reactor pressure vessel 1 is located at the position farthest from the cold pipe section 11 and the hot pipe section 12 in the circumferential direction, which can minimize the adverse effect on the flow field in the reactor during the normal operation of the reactor.

[0036] like Figure 5 As shown, in some embodiments, the pipe section of the second water injection pipeline 3 located inside the reactor pressure vessel 1 includes a semicircular tube, and the semicircular tube and the inner wall surface of the reactor pressure vessel 1 together define a pipe cavity. Alternatively, in other embodiments, the pipe section of the second water injection pipeline 3 located inside the reactor pressure vessel 1 includes a round tube, and the round tube is arranged to fit the inner wall surface of the reactor pressure vessel 1. For example, in the first embodiment, the first pipe section 321 of the second pipe 32 may include a semicircular tube. In some other embodiments, a portion of the second water injection pipeline 3 may also be arranged on the outer wall surface of the reactor pressure vessel 1, and it extends along the outer wall surface to the lower head 14 and then penetrates into the interior of the reactor pressure vessel 1.

[0037] like Figure 6 As shown, in the third embodiment of the second water injection pipeline 3, the difference from the first and second embodiments is that the second water injection pipeline 3 is penetrated through the lower head 14 of the reactor pressure vessel 1, and one end thereof located inside the reactor pressure vessel 1 is penetrated through the lower core support plate 17. That is, the second water injection pipeline 3 directly passes through the lower head 14 from bottom to top, and its output end is penetrated through the lower core support plate 17. As a result, the coolant output from the output end of the second water injection pipeline 3 directly passes 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, playing the role of accurately and effectively cooling the core.

[0038] The details not described in detail in any of the first embodiment, the second embodiment and the third embodiment can be set with reference to other embodiments and will not be described in detail here.

[0039] In some embodiments, the first water injection pipeline 2 includes a closed pipe section and / or an open pipe section located in the core area 19. That is, the first water injection pipeline 2 may include one or both of the closed pipe section and the open pipe section. The open pipe section means that the output end of the first water injection pipeline 2 located in the core area 19 is open, and the coolant can flow out directly from the output end to cool the core. The closed pipe section means that the output end of the first water injection pipeline 2 located in the core area 19 is closed, and the coolant can flow out only after the closed pipe section is melted through by high temperature. The advantage of setting a closed pipe section is that under accident conditions, when the coolant in the core area 19 loses too much water, causing the temperature in the core area 19 to rise, the closed pipe section automatically releases the coolant after being melted through, and the part where the closed pipe section is melted through corresponds to the position with the highest temperature in the core area 19, so that the area with the highest temperature in the core area 19 can be automatically captured through the melting point of the closed pipe section, and the coolant is released to the area with the highest temperature at the first time, so that more accurate cooling can be achieved in the core area 19.

[0040] Furthermore, the melting point of the material used for the closed tube section can be less than or equal to the melting point of the material used for the fuel rod cladding tube in the core area 19. In this way, under accident conditions, when the coolant in the core area 19 loses too much water, causing the temperature in the core area 19 to rise, the closed tube section located in the core area 19 is melted through before the fuel rod cladding tube or melted through 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 section 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 area of ​​the fuel assembly in the core area 19 exceeds 1000°C, the closed tube section of the corresponding area will melt, and the cooling water can quickly flow out from the melted area of ​​the closed tube section, cool the surrounding high-temperature fuel assembly area, and quickly flood the core. The closed tube section and the open tube section can be made of the same material as the fuel assembly and the internal components of the reactor, usually zirconium alloy and stainless steel alloy. When the closed tube segment and the fuel rod cladding tube are made of different materials, if the material used for the closed tube segment is a new material that has not been tested and verified, it needs to be tested and verified before it can be put into use in the core area 19. When the closed tube segment and the fuel rod cladding tube are made of the same material, the melting point of the closed tube segment is equal to the melting point of the fuel rod cladding tube in the core area 19, and the closed tube segment and the fuel rod cladding tube are melted through at the same time, and the position with the highest temperature in the core area 19 can also be accurately captured, and the material used for the closed tube segment (that is, 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 an open pipe section and a closed pipe section, the open pipe section can release coolant directly to the core area 19 without distinction, while the closed pipe section automatically positions itself through its melt-through point to the area with the highest temperature in the core area 19 to release coolant. The combination of the open pipe section and the closed pipe section can cool the core in the core area 19 more comprehensively and accurately.

[0042] In some embodiments, at least part of the first water injection pipeline 2 is passed through the spacer grid for fixing the fuel rod assembly for fixing. That is, only part of the pipe section of the first water injection pipeline 2 may be passed through the spacer grid for fixing; or, all the pipe sections of the first water injection pipeline 2 may be passed through the spacer grid for fixing. That is, part of the fuel rod assembly on the existing spacer grid in the reactor pressure vessel 1 may be replaced with the pipe section of the first water injection pipeline 2. In this way, the existing spacer grid in the reactor pressure vessel 1 may be used to limit and fix the first water injection pipeline 2 to prevent the first water injection pipeline 2 from vibrating significantly under normal operating conditions of the reactor.

[0043] Furthermore, the first water injection pipeline 2 can be arranged in the middle area of ​​the support plate 16 on the core. The fuel rod assembly is located outside the first water injection pipeline 2. The first water injection pipeline 2 that is fixed through the positioning grid will occupy part of the placement space of the fuel rod assembly, but under normal design conditions, the number of fuel rod assemblies is as high as tens of thousands. As long as the number of pipe sections of the first water injection pipeline 2 is much smaller than the number of fuel rod assemblies and the diameter of the pipe section of the first water injection pipeline 2 is much smaller than the diameter of the fuel rod assembly, the space occupied by the first water injection pipeline 2 is relatively small, and the impact caused is not significant.

[0044] like Figure 3 As shown, in some embodiments, the first water injection pipeline 2 includes a water injection main pipe 21, a first diverter 22 and a water injection tube bundle 23. The first diverter 22 and the water injection tube bundle 23 are located inside the reactor pressure vessel 1. The water injection main pipe 21 is arranged through 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 the coolant source, and the other end of the water injection main pipe 21 is located inside the reactor pressure vessel 1. The first diverter 22 is connected between the other end of the water injection main pipe 21 and the water injection tube bundle 23, and the water injection tube bundle 23 passes through the upper support plate 16 of the core and extends to the core area 19. Among them, the water injection tube bundle 23 includes a plurality of closed pipe sections and / or open pipe sections located in the core area 19. The materials of different pipe sections can be the same or different. The water injection main pipe 21 is connected to the coolant source, and the coolant can flow through the water injection main pipe 21, the first diverter 22 and the water injection tube bundle 23 in sequence to reach the core area 19. The coolant is distributed through the first flow divider 22, and the first flow divider 22 is used to evenly or proportionally distribute the coolant in the water injection main pipe 21 to multiple output pipes of the water injection pipe bundle 23. In this way, only one water injection main pipe 21 needs to be set to pass through the reactor pressure vessel 1, which can minimize the number of pipes passing through the reactor pressure vessel 1. The water injection pipe bundle 23 is used to inject coolant into the core area 19 in multiple pipe sections, which can effectively avoid the situation where some pipe sections are blocked and cannot be effectively injected.

[0045] In some embodiments, the number of the second pipe segments 322 can be multiple, and multiple second pipe segments 322 penetrating the lower core support plate 17 are provided to inject coolant into the core region 19, which can effectively avoid the situation where some pipe segments are blocked and cannot be effectively injected. The second water injection pipeline 3 can also include a second diverter (not shown), which is located between the first pipe segment 321 and the second pipe segment 322 of the second pipeline 32, and is used to evenly or proportionally distribute the coolant in the first pipe segment 321 to the multiple second pipe segments 322.

[0046] like Figure 3As shown, in some embodiments, the reactor pressure vessel direct injection safety system also 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 one by one or both. 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 at the same time, the input end of the first water injection pipeline 2 is respectively connected to the first active water injection unit 41 and the first water injection tank 420. 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 first water injection tank 420 is a low-pressure water injection tank. The water pressure inside the medium-pressure water injection tank is greater than the water pressure inside the low-pressure water injection tank. When the pressure of the nuclear reactor's primary circuit after water loss drops to a value lower than 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 area 19 through the first water injection pipeline 2 to cool the core in a passive manner. The water injection flow rate may exceed 100m 3 / h. Under extremely severe loss of coolant accident conditions, after the medium-pressure water injection tank is filled with water, the core cannot be cooled, and some fuel assemblies may melt to a large extent. When the pressure of the nuclear reactor's primary circuit drops to a level lower than the water pressure in the low-pressure water injection tank after the loss of water, the cooling water in the low-pressure water injection tank will be quickly injected into the core area 19 through the first water injection pipeline 2. At this time, the water injection flow rate can exceed 50m 3 The first active water injection unit 41 has a water pump, which can actively inject coolant fluid with a higher pressure (for example, more than 4 MPa) into the first water injection pipeline 2 to actively cool the 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, and 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. For more specific details about the second active water injection unit 51, refer to the setting of the first active water injection unit 41, and for more specific details about the second passive water injection unit, refer to the setting of the first passive water injection unit 42, which will not be repeated here.

[0048] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the scope covered by the claims of the present invention.

Claims

1. A reactor pressure vessel direct injection safety system, characterized in that: It comprises a first water injection pipeline (2) and / or a second water injection pipeline (3); The first water injection pipeline (2) is arranged through 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 passes through the upper core support plate (16) and extends to the core area (19); The second water injection pipeline (3) is arranged through 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; the output end of the second water injection pipeline (3) is located inside the reactor pressure vessel (1) and extends at least to a descending section (18) of the reactor pressure vessel (1).

2. The reactor pressure vessel direct injection safety system according to 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 area (19).

3. The reactor pressure vessel direct injection safety system according to claim 2, characterized in that: The melting point of the material used in the closed tube section is less than or equal to the melting point of the material used in the fuel rod cladding tube in the core area (19).

4. The reactor pressure vessel direct injection safety system according to claim 1, characterized in that: At least part of the first water injection pipeline (2) is passed through a positioning grid for fixing the fuel rod assembly for fixation.

5. The reactor pressure vessel direct injection safety system according to claim 1, characterized in that: 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 tube bundle (23) are located inside the reactor pressure vessel (1); the water injection main pipe (21) is arranged through 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 tube bundle (23); and the water injection tube bundle (23) passes through an upper core support plate (16) and extends to a core region (19).

6. The reactor pressure vessel direct injection safety system according to claim 1, characterized in that: The second water injection pipeline (3) is passed through 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 heights of the cold pipe section (11) and the hot pipe section (12) on the side wall (15) of the reactor pressure vessel (1).

7. The reactor pressure vessel direct injection safety system according to claim 6, characterized in that: The second water injection pipeline (3) comprises a first pipeline (31) and a second pipeline (32) connected to each other, wherein the first pipeline (31) is located outside the reactor pressure vessel (1) and connected to a coolant source, and the second pipeline (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) being connected between the first pipe (31) and the second pipe section (322), the first pipe section (321) being arranged on the inner wall surface of the reactor pressure vessel (1) and extending along the descending 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) being passed through the lower core support plate (17).

8. The reactor pressure vessel direct injection safety system according to claim 6, 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 at an intermediate position between the cold pipe section (11) and the hot pipe section (12).

9. The reactor pressure vessel direct injection safety system according to claim 1, characterized in that: The second water injection pipeline (3) is arranged through the lower head (14) of the reactor pressure vessel (1), and one end thereof located inside the reactor pressure vessel (1) is arranged through the lower core support plate (17).

10. The reactor pressure vessel direct injection safety system according to any one of claims 1 to 9, characterized in that: 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), wherein 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).

11. The reactor pressure vessel direct injection safety system according to any one of claims 1 to 9, characterized in that: 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, wherein 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).

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