Pool type nuclear reactor system having parallel residual heat removal channel

Abstract

To provide a pool type nuclear reactor system provided with a parallel residual heat removal flow passage capable of efficiently forming a natural circulation flow rate circulating in a primary system and suppressing a rapid rise of a core outlet maximum temperature.SOLUTION: During normal operation, the coolant pumped by the pump located in the low temperature pool flows into the core inlet plenum, and then is heated through the reactor core and accommodated in the high temperature pool; Disclosed is a pool type nuclear reactor system including a normal coolant circulation path configured such that a coolant located in a high temperature pool is cooled through an intermediate heat exchanger and re-introduced into the low temperature pool, an emergency coolant circulation path configured such that the coolant located in the high temperature pool heated by a core is cooled through an auxiliary cooling system and then re-introduced into the core through a pump and a core inlet plenum when a loss of power accident occurs, and a parallel residual heat removal path connecting the core inlet plenum and the low temperature pool and provided by a parallel connection with the normal coolant circulation path and the emergency coolant circulation path.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pool-type nuclear reactor system equipped with parallel residual heat removal channels for efficiently removing residual heat generated in the reactor core in the event of an accident at a nuclear power plant. [Background technology]

[0002] In all cases of accidents at nuclear power plants, including loss of power, the reactor will shut down and the reactor coolant pumps that require power supply may also shut down.

[0003] On the other hand, decay heat continues to be generated within the reactor core even after the reactor has been shut down. If all residual heat, including this decay heat, is not removed, the temperature and pressure of the reactor core and coolant will rise, and in the worst case scenario, the engineered safety barriers may be breached, leading to an accident in which radioactive materials leak to the outside.

[0004] Therefore, to ensure the safety of nuclear reactors, it is very important to remove residual heat. A residual heat removal system (RHRS) is essential to release residual heat outside the reactor even after the reactor is shut down. The residual heat removal system must be highly reliable and utilize the natural circulation phenomenon, which does not require a driving force such as a pump.

[0005] Methods being considered for removing residual heat from the reactor core include the Direct Reactor Auxiliary Cooling System (DRACS), which uses two heat exchangers to release the residual heat into the atmosphere, and the Reactor Vessel Auxiliary Cooling System (RVACS), which does not use a heat exchanger but uses the outer wall of the reactor vessel as a heat transfer surface to release the residual heat into the atmosphere through heat exchange by convection and radiation.

[0006] In order to release the residual heat generated in the core to the outside, it is first necessary to transfer the residual heat generated in the core to the heat exchanger of the residual heat removal system in the case of DRACS, or to the wall of the reactor vessel in the case of RVACS.

[0007] When the reactor coolant pump stops after an accident, the driving force from the pump disappears, and the driving force for the natural circulation flow is generated by the density and height difference depending on the coolant's position in the primary system of the reactor. The natural circulation flow rate is determined by the balance between the driving force and the flow resistance of the core, pump, etc. in the natural circulation flow path. To achieve the maximum natural circulation flow rate, the reactor design can reflect factors such as reducing the flow resistance, increasing the height difference between the core (heat source) and the heat removal source, and configuring the reactor to provide additional driving force.

[0008] However, with the conventional concept, if sufficient natural circulation flow rate passing through the core is not formed initially, or if the total flow rate of fully developed natural circulation is less than predicted, the amount of heat released to the outside cannot keep up with the residual heat generated in the core, resulting in a continuous rise in the core outlet temperature. Summary of the Invention [Problem to be solved by the invention]

[0009] The first object of the present invention is to provide a pool-type reactor system equipped with a parallel residual heat removal flow path that can efficiently form a natural circulation flow rate circulating through the primary system and suppress a sudden rise in the maximum temperature at the core outlet by directly connecting the final heat sink for residual heat removal to the core in the early stage of a power loss accident at a nuclear power plant.

[0010] A second object of the present invention is to provide a pool-type reactor system equipped with parallel residual heat removal channels that can efficiently reduce the core inlet and outlet temperatures by shortening the time required for full development of natural circulation flow and simplifying the heat transfer path from the core to the final heat sink. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention discloses a pool-type nuclear reactor system including: a normal coolant circulation flow path configured, during normal operation, for low-temperature coolant pumped by a pump located in a low-temperature pool to flow into a core inlet plenum, then heated through the core and stored in a high-temperature pool, and for the high-temperature coolant located in the high-temperature pool to be cooled through an intermediate heat exchanger and re-flow into the low-temperature pool; an emergency coolant circulation flow path configured, during a power loss accident, for the high-temperature coolant located in the high-temperature pool to be cooled through an auxiliary cooling system and then re-flow into the core via the pump and the core inlet plenum; and a parallel residual heat removal flow path connecting the core inlet plenum and the low-temperature pool and connected in parallel to the normal coolant circulation flow path and the emergency coolant circulation flow path.

[0012] The parallel residual heat removal flow path may have a flow resistance greater than that of the reactor core and the pump.

[0013] According to one embodiment of the present invention, during normal operation, the coolant may branch at the core inlet plenum, flow in parallel to the core and connecting flow paths, and then enter the low-temperature pool; and during a loss-of-power accident, the coolant may branch at the low-temperature pool, flow in parallel to the pump and parallel residual heat removal flow paths, and then enter the core inlet plenum.

[0014] Furthermore, to achieve the above-mentioned object, the present invention discloses a pool-type reactor system including: a normal coolant circulation flow path configured so that low-temperature coolant pumped by a pump located in a low-temperature pool flows into a core inlet plenum, is heated through the core, and is stored in the high-temperature pool; and during normal operation, the high-temperature coolant located in the high-temperature pool is cooled through an intermediate heat exchanger and re-flows into the low-temperature pool; an emergency coolant circulation flow path configured so that, in the event of a power outage, the high-temperature coolant located in the high-temperature pool, heated by the core, re-flows into the low-temperature pool, and then flows into the core inlet plenum via the pump, thereby cooling the coolant during or after the re-flow; and a parallel residual heat removal flow path connecting the core inlet plenum and the low-temperature pool, configured so that during normal operation, a portion of the low-temperature coolant located in the core inlet plenum flows into the low-temperature pool, and during a power outage, a portion of the low-temperature coolant located in the low-temperature pool flows into the core inlet plenum.

[0015] and a parallel residual heat removal flow path connecting the core inlet plenum and the cold pool through which the coolant can flow, the parallel residual heat removal flow path having a flow resistance preset so that the coolant flows from the core inlet plenum to the cold pool during normal operation, and so that the coolant flows from the cold pool to the core inlet plenum during a loss of power accident. [Effects of the Invention]

[0016] The effects of the present invention obtained by the above-mentioned solution are as follows.

[0017] First, in the event of a loss of power accident, natural circulation occurs due to the difference in coolant density between the core and the heat exchanger. The naturally circulating coolant flows in parallel through the emergency coolant circulation path, which flows from the low-temperature pool via a pump into the core inlet plenum, and the parallel residual heat removal path, which flows directly from the low-temperature pool into the core inlet plenum. Because the path resistances are connected in parallel, the overall resistance of the paths is reduced. This increases the flow rate through the core compared to a single path, preventing a rapid increase in the maximum core outlet temperature in the initial stage.

[0018] Second, by increasing the flow rate through the core, fully developed natural circulation flow will effectively reduce the core inlet and outlet temperatures in the long term, since it will release more heat outside the reactor than the residual heat newly generated in the core. [Brief explanation of the drawings]

[0019] [Figure 1] This shows the coolant circulation flow path in a reactor residual heat removal system according to one embodiment of the present invention, and is a circuit diagram showing (a) the coolant circulation flow path during normal operation, and (b) the coolant circulation flow path during a power loss accident. [Figure 2] 1A and 1B are front views of a nuclear reactor including an RVACS-type auxiliary cooling system according to one embodiment of the present invention, and are conceptual diagrams showing (a) the flow of coolant during normal operation and (b) the flow of coolant during a loss of power accident. [Figure 3] 1A and 1B are front views of a nuclear reactor including a DRACS-type auxiliary cooling system according to another embodiment of the present invention, showing (a) the flow of coolant during normal operation, and (b) the flow of coolant during a loss of power accident. [Figure 4] 1 is a graph showing the change in core inlet and outlet coolant temperatures after a loss of power accident comparing one embodiment of the present invention with a single-passage embodiment; [Figure 5]10 is a graph showing the amount of residual heat generated in the core after a loss of power accident and the amount of heat released to the outside through the residual heat removal system, comparing one embodiment of the present invention with a single-passage embodiment. [Figure 6] 1 is a graph showing the core inlet and outlet coolant temperature variation as a function of the ratio of the area of ​​the parallel residual heat removal channels to the area of ​​the core of the present invention; [Figure 7] 10 is a table showing the change in flow rate and pump according to the area ratio of the parallel residual heat removal flow paths during normal operation of the present invention. [Figure 8] 1 is a graph comparing one embodiment of the present invention with a single-passage embodiment, showing the amount of heat released to the outside through the residual heat removal system depending on the air flow rate at the outer wall of the reactor vessel in a reactor including a RVACS-type auxiliary cooling system, (a) when the air flow rate at the outer wall of the reactor vessel is 0.04 kg / s, and (b) when the air flow rate at the outer wall of the reactor vessel is 1.00 kg / s. DETAILED DESCRIPTION OF THE INVENTION

[0020] A pool-type nuclear reactor system equipped with parallel residual heat removal channels related to the present invention will now be described in more detail with reference to the drawings.

[0021] When describing the embodiments disclosed in this specification, if it is determined that a specific description of related publicly known technology may obscure the gist of the embodiments disclosed in this specification, that detailed description will be omitted.

[0022] The accompanying drawings are merely intended to facilitate understanding of the embodiments disclosed in this specification, and should not be construed as limiting the technical ideas disclosed in this specification, but should be understood to include all modifications, equivalents, and alternatives included within the spirit and technical scope of the present invention.

[0023] In the following description, singular terms include plural terms unless the context clearly dictates otherwise.

[0024] In this application, the terms "comprise" or "have" and the like are intended to specify the presence of any feature, number, step, operation, component, part, or combination thereof described herein, and are to be understood as not precluding the possible presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0025] When a component is referred to as being "coupled" or "connected" to another component, it should be understood that it may be directly coupled or connected to the other component, but that there may be other components between them. On the other hand, when a component is referred to as being "directly coupled" or "directly connected" to another component, it should be understood that there are no other components between them.

[0026] In this specification, even in different embodiments, the same or similar components are denoted by the same or similar reference numerals, and redundant explanations thereof will be omitted.

[0027] FIG. 1 shows a coolant circulation flow path in a reactor residual heat removal system 100 according to one embodiment of the present invention, and is a circuit diagram showing (a) the coolant circulation flow path during normal operation and (b) the coolant circulation flow path during a power loss accident. FIG. 2 is a front view of a reactor including a RVACS-type auxiliary cooling system according to one embodiment of the present invention, and is a conceptual diagram showing (a) the flow of coolant during normal operation and (b) the flow of coolant during a power loss accident. FIG. 3 is a front view of a reactor including a DRACS-type auxiliary cooling system according to another embodiment of the present invention, and is a conceptual diagram showing (a) the flow of coolant during normal operation and (b) the flow of coolant during a power loss accident.

[0028] 1 to 3, a nuclear reactor residual heat removal system 100 according to one embodiment of the present invention includes a normal coolant circulation path, an emergency coolant circulation path, and a parallel residual heat removal path 130.

[0029] 1(a), the normal coolant circulation flow path 110 refers to a flow path through which the coolant flows and circulates in order through the pump 116, the core inlet plenum 112, the core 111, the high-temperature pool 113, the intermediate heat exchanger 114, the low-temperature pool 115, and the pump 116. The emergency coolant circulation flow path 120 refers to a flow path through which the coolant flows and circulates in order through the core 111, the high-temperature pool 113, the auxiliary cooling system 122, the low-temperature pool 115, the pump 116, the core inlet plenum 112, and the core 111. The parallel residual heat removal flow path 130 refers to a flow path connecting the core inlet plenum 112 and the low-temperature pool 115 in both FIGS. 1(a) and 1(b).

[0030] During normal operation, the coolant can flow along the normal coolant circulation channel 110. The normal coolant circulation channel 110 is located inside the reactor vessel 200, and the circulation process is as follows.

[0031] The cold coolant is pumped by pumps 116 located in a cold pool 115 and enters a core inlet plenum 112 in the reactor core section. The reactor core section is located within the cold pool 115 and may consist of the core inlet plenum 112 and the reactor core 111.

[0032] The coolant is branched at the core inlet plenum 112, with a portion flowing into the core 111 and the remaining portion flowing into a parallel residual heat removal channel 130 (described later). The remaining portion may be smaller than the aforementioned portion. The core 111 may be located above the core inlet plenum 112.

[0033] The coolant that flows into the core 111 is heated by the heat generated by nuclear fission and is contained in a low-density, high-temperature state in a high-temperature pool 113. The high-temperature pool 113 may be located inside a low-temperature pool 115.

[0034] The coolant contained in the high-temperature pool 113 flows into the intermediate heat exchanger 114. The upper end of the intermediate heat exchanger 114 is located in the high-temperature pool 113, and the lower end is located in the low-temperature pool 115, thereby forming a flow path through which the coolant can flow from the high-temperature pool 113 to the low-temperature pool 115. The high-temperature coolant flowing in from the high-temperature pool 113 may be cooled by transferring heat to a coolant (second coolant) flowing inside the intermediate heat exchanger 114. The second coolant may be sent to a secondary system that produces electricity.

[0035] The cooled, high density, low temperature coolant may be contained in a cold pool 115 and circulated back into a pump 116 located in the cold pool 115 .

[0036] On the other hand, in the event of a power outage, the coolant may flow along the emergency coolant circulation flow path 120 .

[0037] The pump 116 is stopped, the driving force from the pump 116 is lost, and the coolant receives driving force from the density difference during heating and cooling.

[0038] The coolant passing through the core 111 becomes hot and low density, and rises due to buoyancy and flows into the hot pool 113 .

[0039] The hot coolant contained in the hot pool 113 re-enters the cold pool 115, and the coolant is cooled during or after the re-entry process. The hot coolant flows through the auxiliary cooling system 122 and is cooled to a low temperature and high density state.

[0040] The low-temperature coolant is branched in the low-temperature pool 115, with a portion flowing into the pump 116 and the remaining portion flowing into a connecting flow path 130, which will be described later. Here, the remaining portion may be smaller in amount than the aforementioned portion.

[0041] The pump 116 is in a stopped state and can serve as a flow path for the coolant to flow through. The coolant that has passed through the pump 116 re-enters the core 111 via the core inlet plenum 112.

[0042] 2, the auxiliary cooling system 122 may use a RVACS method that releases residual heat to the atmosphere through heat exchange with naturally circulating air on the reactor vessel wall. In this case, the driving force for the flow of the coolant is generated by the difference in density of the coolant caused by heating of the coolant in the core 111 and cooling of the coolant by heat exchange on the reactor vessel wall.

[0043] The high-temperature coolant passes through the intermediate heat exchanger 114, but flows into the low-temperature pool 115 without heat exchange, where it is cooled by heat exchange with naturally circulating air through the wall of the reactor vessel 200, and then flows into the pump 116 and the parallel residual heat removal flow path 130 described later so that it can be circulated.

[0044] In the case of RVACS, the present invention cites an air-cooled type as an example in which the high-temperature coolant inside the reactor vessel 200 exchanges heat with the air naturally circulating on the outer wall surface of the reactor vessel 200 through convection and radiation, but it may also be a water-cooled type in which a liquid such as water circulates on the outer wall surface of the reactor vessel 200 and exchanges heat with the internal coolant.

[0045] 3, the auxiliary cooling system 122 may use a DRACS method in which residual heat is released into the atmosphere using multiple sequentially connected residual heat removal system heat exchangers. In this case, the driving force for the flow of the coolant is generated by the difference in coolant density caused by the heating of the coolant in the reactor core 111 and the cooling of the coolant by the first residual heat removal system heat exchanger 121.

[0046] The high-temperature coolant contained in the high-temperature pool 113 exchanges heat with the coolant (third coolant) flowing inside the first residual heat removal system heat exchanger 121 located in the high-temperature pool 113, and flows into the low-temperature pool 115 in a cooled state. The third coolant exchanges heat with air through the second residual heat removal system heat exchanger located outside the reactor vessel 200, thereby releasing residual heat into the atmosphere. The second residual heat removal system heat exchanger may also be connected to another residual heat removal system heat exchanger.

[0047] The intermediate heat exchanger 114 may be connected to a component in the secondary system, such as a secondary system pump, that provides a driving force for the secondary coolant. Therefore, during normal operation, the second coolant is circulated by the secondary system pump, and the coolant flows into the intermediate heat exchanger 114 to exchange heat with the second coolant. During a loss of power accident, the coolant flows into the first residual heat removal system heat exchanger 121, and heat exchange occurs, generating a coolant driving force. However, no heat exchange occurs in the intermediate heat exchanger 114, and therefore no coolant driving force is generated. Therefore, most of the natural circulation path is formed through the first residual heat removal system heat exchanger 121.

[0048] However, the present invention is not necessarily limited to this. As another example, the auxiliary cooling system 122 may include both a RVACS and a DRACS.

[0049] Figure 4 is a graph showing the temperature changes of the inlet and outlet coolant of the core 111 after a loss of power accident, comparing one embodiment of the present invention with a single-passage embodiment, and Figure 5 is a graph showing the residual heat generated in the core 111 after a loss of power accident and the amount of heat released to the outside through the residual heat removal system, comparing one embodiment of the present invention with a single-passage embodiment.

[0050] In Figure 5, the heat removal amount of the existing concept refers to a single flow path, and the heat removal amount of the new concept refers to a pool-type reactor system equipped with parallel residual heat removal flow paths of the present invention. The x-axis represents time (s) from the time of the power loss accident, and the y-axis represents the residual heat generation rate and heat removal rate (%) relative to the initial residual heat generation rate, normalized by dividing by the maximum initial residual heat value.

[0051] 4 and 5 together with FIG. 1 and FIG. 2, the parallel residual heat removal channel 130 directly connects the core inlet plenum 112 and the low-temperature pool 115, and is provided in parallel with the normal coolant circulation channel 110 and the emergency coolant circulation channel 120. Here, being provided in parallel means that during normal operation, from the perspective of the pump 116, which is the driving source, the flow of coolant passing through the core 111 and the flow of coolant passing through the parallel residual heat removal channel 130 are parallel, and in the event of a loss of power accident, from the perspective of the core 111, which is the driving source, the flow of coolant passing through the pump 116 and the flow of coolant passing through the parallel residual heat removal channel 130 are parallel.

[0052] From the perspective of both normal operation and power loss accidents, the parallel residual heat removal flow path may be understood as a connecting flow path, but as will be described later, the purpose of the present invention is to improve residual heat removal efficiency and safety, so it is referred to as a parallel residual heat removal flow path from the perspective of power loss accidents.

[0053] The parallel residual heat removal flow path 130 has a flow resistance greater than that of the core 111 and the pump 116, allowing coolant to flow from the core inlet plenum 112 to the cold pool 115, and conversely, allowing coolant to flow from the cold pool 115 to the core inlet plenum 112.

[0054] During normal operation, the coolant branches at the core inlet plenum 112 , with a portion flowing into the core 111 and the remaining portion flowing into the parallel residual heat removal channels 130 to form parallel flows, which then join together in the low temperature pool 115 .

[0055] The driving force of the pump 116 allows a portion of the coolant to flow into the parallel residual heat removal channel 130, which has a relatively large resistance value, and the branch flow rate can be determined according to the ratio of the resistance values ​​of the core 111 and the parallel residual heat removal channel 130.

[0056] In the event of a loss of power accident, there is no driving force in the pump 116, and therefore the coolant cannot flow from the core inlet plenum 112 to the parallel residual heat removal channel 130, which has a higher resistance than the core 111. In this case, the coolant flows from the cold pool 115 to the core inlet plenum 112 via the parallel residual heat removal channel 130.

[0057] The coolant is divided in the low temperature pool 115 , with a portion flowing to a pump 116 and the remaining portion flowing to a parallel residual heat removal channel 130 to form parallel flows, which then join at the core inlet plenum 112 .

[0058] Due to the driving force caused by the difference in coolant density in the core 111 and the auxiliary cooling system 122, part of the coolant can flow into the parallel residual heat removal channel 130, which has a relatively high resistance value, and the branch flow rate can be determined according to the ratio of the resistance values ​​of the pump 116 and the parallel residual heat removal channel 130.

[0059] The operation and effects of the reactor residual heat removal system 100 having such a configuration will be described below.

[0060] In the event of a loss of power accident, the main driving force of the coolant is generated by the density difference that occurs through the reactor core 111. The coolant that passes through the reactor core 111 is stored in a high-temperature pool 113, cooled through the auxiliary cooling system 122, and then branched off into the low-temperature pool 115. The coolant can obtain driving force by the density difference during the cooling process.

[0061] When viewed from the reactor core 111, which is the main driving source, the coolant branches off at the low-temperature pool 115, with a portion flowing into the parallel residual heat removal flow path 130 and the remaining portion flowing into the flow path passing through the pump 116, forming a parallel flow. Because the flow paths are configured in parallel, the overall flow path resistance is reduced. This reduction in overall flow path resistance increases the natural circulation flow rate of the coolant passing through the reactor core 111 under the same conditions compared to a single flow path, thereby improving the residual heat removal efficiency.

[0062] 4 and 5 showing experimental results of a nuclear reactor simulator according to an embodiment of the present invention, it was predicted that the maximum temperatures at the inlet and outlet of the core 111 during a power outage accident would be lower than those in the case of a conventional single flow path, and that the temperatures at the inlet and outlet of the core 111 would decrease in the long term. In addition, it was calculated that the amount of heat released to the outside through the residual heat removal system according to an embodiment would be greater than the residual heat generated in the core 111 in the long term, while the amount of heat released to the outside in the case of a conventional single flow path would not be able to keep up with the residual heat under the same conditions and for the same time.

[0063] In the above experiment, the reactor auxiliary cooling system was the RVASC type, and the air flow rate at the outer wall of the reactor vessel was calculated to be 1.00 kg / s. The calculation was performed using the MARS-LMR computer code developed by the Korea Atomic Energy Research Institute.

[0064] In another embodiment of the present invention, the parallel residual heat removal channels 130 can function as coolant fill and drain holes for filling the reactor with coolant before operation and draining the coolant after the reactor's life is over.

[0065] The parallel residual heat removal channel 130 may be separate from the coolant filling and draining holes. When filling the coolant before the reactor is operated, the coolant flows in from the top of the reactor, and the coolant filling and draining holes serve as channels to quickly fill the vessel. However, after the reactor is operated, the channels have a large resistance value and cannot serve as channels for the coolant to flow.

[0066] The parallel residual heat removal channels 130 have a smaller flow resistance than the coolant filling and discharging holes so that they can serve as channels through which the coolant can flow during normal operation and in the event of a power outage.

[0067] FIG. 6 is a graph showing the change in the temperature of the inlet and outlet coolant of the core 111 according to the ratio of the area of ​​the parallel residual heat removal channel 130 to the area of ​​the core 111 of the present invention, and FIG. 7 is a table showing the change in the flow rate and pump 116 according to the ratio of the area of ​​the parallel residual heat removal channel 130 during normal operation of the present invention.

[0068] 6 and 7, it is preferable that the ratio of the area of ​​the parallel residual heat removal channels 130 to the area of ​​the core 111 be less than 0.85%.

[0069] During normal operation, if the coolant branches at the core inlet plenum 112 and some of it flows into the low-temperature pool 115, the flow rate passing through the core 111 will be reduced compared to a conventional single flow path, which may reduce the cooling efficiency of the core 111. In order to maintain the flow rate passing through the core 111, the output of the pump 116 needs to be increased, but if the rate of increase (ΔP) is too large, the efficiency of the reactor may decrease.

[0070] When calculating so that the output of the pump 116 satisfies 110%, which does not exceed the operating margin of 10%, the ratio of the area of ​​the parallel residual heat removal channel 130 to the area of ​​the core 111 is preferably less than 0.85%.

[0071] FIG. 8 is a graph comparing one embodiment of the present invention with a single-passage embodiment, showing the amount of heat released to the outside through the residual heat removal system depending on the air flow rate at the outer wall of the reactor vessel in a reactor including a RVACS-type auxiliary cooling system, comparing (a) the case where the air flow rate at the outer wall of the reactor vessel is 0.04 kg / s and (b) the case where the air flow rate at the outer wall of the reactor vessel is 1.00 kg / s.

[0072] In FIG. 8, the amount of heat removal in the existing concept refers to a single flow path, and the amount of heat removal in the new concept refers to a nuclear reactor system including the parallel residual heat removal flow paths 130 of the present invention.

[0073] At this time, the ratio of the area of ​​the parallel residual heat removal channel 130 to the area of ​​the reactor core 111 is 0.57%. The x-axis indicates time (s) from the time of the power loss accident, and the y-axis indicates the amount of residual heat generated and the amount of heat removed (%) relative to the amount of initial residual heat generated, normalized by dividing by the maximum value of the initial residual heat.

[0074] Referring to FIG. 8, in a nuclear reactor including a RVACS type auxiliary cooling system, the air flow rate at the outer wall of the reactor vessel 200 is preferably 1.00 kg / s or more.

[0075] When the air flow rate at the outer wall of the reactor vessel 200 is 0.04 kg / s, calculations have shown that in both one embodiment of the present invention and the single flow path, the amount of heat released to the outside through the residual heat removal system is small compared to the residual heat generated in the core 111, so the inlet and outlet temperatures of the core 111 continue to rise.

[0076] When the air flow rate at the outer wall of the reactor vessel 200 is 1.00 kg / s, a calculation result was obtained that the amount of heat released to the outside through the residual heat removal system according to one embodiment of the present invention is greater than the residual heat generated in the core 111 at approximately 40,000 seconds. Meanwhile, in the case of a single flow path, a calculation result was obtained that the residual heat generated in the core 111 is greater than the amount of heat released to the outside through the residual heat removal system, even though the coolant flow rate is increased.

[0077] In yet other embodiments of the present invention, the parallel residual heat removal channels 130 may be provided in multiple and various shapes.

[0078] The parallel residual heat removal channels 130 are formed so that the coolant flows in parallel with the normal coolant circulation channels 110 and the emergency coolant circulation channels 120, reducing the overall flow resistance. By providing multiple parallel residual heat removal channels 130, the flow resistance can be adjusted by their shape and arrangement. Therefore, the flow rate and temperature distribution can be set as intended by the designer during normal operation and in the event of a power outage.

[0079] In another embodiment of the present invention, the parallel residual heat removal channel 130 may be provided with a one-way flow restriction mechanism that blocks the flow of coolant through the parallel residual heat removal channel 130 during normal operation and allows the coolant branched off from the low temperature pool 115 to flow into the core inlet plenum 112 through the parallel residual heat removal channel 130 during a loss of power accident. The one-way flow restriction mechanism may be a check valve.

[0080] The one-way flow restriction mechanism is provided in the direction in which the coolant flows from the low temperature pool 115 to the core inlet plenum 112, and can block the flow of the coolant from the core inlet plenum 112 to the low temperature pool 115. During normal operation, the coolant does not flow from the core inlet plenum 112 to the low temperature pool 115, so the flow rate of the coolant passing through the core 111 increases without increasing the output of the pump 116.

[0081] During a loss of power accident, when coolant flows from the cold pool 115 to the core inlet plenum 112, the one-way flow restriction mechanism opens, allowing the parallel residual heat removal channels 130 to serve as a flow path.

[0082] During normal operation, the parallel residual heat removal flow path 130 is blocked by the one-way flow restriction mechanism, so there is no loss in coolant flow rate and no resulting loss in output from the pump 116. Therefore, the area of ​​the parallel residual heat removal flow path 130 can be set larger to increase the natural circulation flow rate passing through the core 111.

[0083] The above content is merely an example, and various modifications may be made by a person skilled in the art to which the present invention pertains without departing from the scope and technical spirit of the described embodiments. The above-described embodiments may be realized individually or in any combination. [Explanation of symbols]

[0084] 100: Nuclear reactor residual heat removal system 110: Normal coolant circulation channel 111: Core 112: Core entrance plenum 113: Hot Pool 114:Intermediate heat exchanger 115: Low temperature pool 116: Pump 120: Emergency coolant circulation channel 121: First residual heat removal system heat exchanger 122: Auxiliary cooling system 130: Parallel residual heat removal channels 200:Reactor vessel

Claims

1. a normal coolant circulation flow path configured such that during normal operation, low-temperature coolant pumped by a pump located in the low-temperature pool flows into the core inlet plenum, is heated through the core, and is then received in the high-temperature pool, and the high-temperature coolant located in the high-temperature pool is cooled through an intermediate heat exchanger and re-flows into the low-temperature pool; an emergency coolant circulation flow path configured to allow high-temperature coolant located in the high-temperature pool heated by the reactor core to be cooled through an auxiliary cooling system and then re-flow into the reactor core via the pump and the core inlet plenum in the event of a loss of power accident; a parallel residual heat removal flow path connecting the core inlet plenum and the low temperature pool, the parallel residual heat removal flow path being connected in parallel to the normal coolant circulation flow path and the emergency coolant circulation flow path.

2. 2. The pool-type nuclear reactor system according to claim 1, wherein said parallel residual heat removal flow passage has a flow resistance greater than that of said core and said pump.

3. 3. The pool-type reactor system according to claim 2, wherein during normal operation, the coolant branches at the core inlet plenum, flows in parallel to the core and the parallel residual heat removal flow paths, and then flows into the low-temperature pool, and during a loss-of-power accident, the coolant branches at the low-temperature pool, flows in parallel to the pump and the parallel residual heat removal flow paths, and then flows into the core inlet plenum.

4. 4. The pool-type nuclear reactor system according to claim 3, wherein the parallel residual heat removal channels are configured to function as holes for filling with coolant before operation of the reactor and for discharging the coolant after the end of the reactor's life.

5. 5. The pool-type nuclear reactor system according to claim 4, wherein the parallel residual heat removal channels have an area such that the ratio of the area of ​​the parallel residual heat removal channels to the area of ​​the core is less than 0.85%.

6. The pool-type nuclear reactor system according to claim 5, wherein a plurality of parallel residual heat removal channels are provided.

7. 7. The pool-type reactor system according to claim 6, wherein the parallel residual heat removal flow passage is provided with a one-way flow restriction mechanism that blocks the flow of coolant through the parallel residual heat removal flow passage during normal operation, and that allows the coolant branched in the low-temperature pool to flow into the core inlet plenum through the parallel residual heat removal flow passage in the event of a loss of power accident.

8. 2. The pool-type reactor system according to claim 1, wherein the auxiliary cooling system is a reactor vessel auxiliary cooling system (RVACS) that releases residual heat into the atmosphere through heat exchange with naturally circulating air on the wall of the reactor vessel.

9. 2. The pool-type reactor system according to claim 1, wherein the auxiliary cooling system is a direct reactor auxiliary cooling system (DRACS) that releases residual heat into the atmosphere using a plurality of sequentially connected residual heat removal system heat exchangers.

10. a normal coolant circulation flow path configured such that low-temperature coolant pumped by a pump located in the low-temperature pool flows into the core inlet plenum, is heated through the core, and is then accommodated in the high-temperature pool, and during normal operation, the high-temperature coolant located in the high-temperature pool is cooled through an intermediate heat exchanger and re-flows into the low-temperature pool; an emergency coolant circulation flow path configured to allow high-temperature coolant located in the high-temperature pool heated by the core to re-flow into the low-temperature pool and then flow into the core inlet plenum via the pump in the event of a loss-of-power accident, and configured to cool the coolant during or after the re-flow; a parallel residual heat removal flow path that connects the core inlet plenum and the low-temperature pool, and that is configured so that during normal operation, a portion of the low-temperature coolant located in the core inlet plenum flows into the low-temperature pool, and that during a loss-of-power accident, a portion of the low-temperature coolant located in the low-temperature pool flows into the core inlet plenum.

11. 11. The pool-type nuclear reactor system according to claim 10, wherein the parallel residual heat removal flow path has a flow resistance greater than that of the core and the pump.

12. a core section including a core and a core inlet plenum; a high temperature pool containing high temperature coolant heated through the reactor core; an intermediate heat exchanger that exchanges heat with the high-temperature coolant in the high-temperature pool during normal operation; An auxiliary cooling system that allows high-temperature coolant to flow and cool in the event of a power loss accident; a low-temperature pool containing a low-temperature coolant cooled by the intermediate heat exchanger or the auxiliary cooling system; a pump that provides a driving force for causing the low-temperature coolant located in the low-temperature pool to flow into the core inlet plenum; a parallel residual heat removal flow path formed to connect the core inlet plenum and the low temperature pool so that coolant can flow therethrough; a parallel residual heat removal flow path having a flow resistance preset so that coolant flows from the core inlet plenum to the low-temperature pool during normal operation, and so that coolant flows from the low-temperature pool to the core inlet plenum during a loss-of-power accident.

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