POOL-TYPE NUCLEAR REACTOR SYSTEM FEATURING A PARALLEL FLOW PATH FOR RESIDUAL HEAT REMOVAL

Abstract

The present invention discloses a pool-type nuclear reactor system comprising: a normal circulating coolant flow path configured such that, in normal operation, after low-temperature coolant pumped by a pump located in a low-temperature pool flows into a core inlet plenum, the coolant is heated by passing through the core and received into a high-temperature pool, and high-temperature coolant located in a high-temperature pool is cooled by passing through an intermediate heat exchanger and reintroduced into the low-temperature pool;an emergency coolant circulation flow path configured so that, in the event of a power failure, the high-temperature coolant in the core-heated high-temperature pool is cooled by passing through an auxiliary cooling system and then reintroduced into the core via the pump and core inlet plenum; and a parallel flow path for residual heat removal configured to connect the core inlet plenum and the low-temperature pool and to be connected in parallel to the normal coolant circulation flow path and the emergency coolant circulation flow path. Figure for abbreviation: Figure 1;

Description

Title of the invention: POOL-TYPE NUCLEAR REACTOR SYSTEM FEATURING A PARALLEL FLOW PATH FOR RESIDUAL HEAT REMOVAL REFERENCE TO A RELATED APPLICATION

[0001] The present application claims priority from Korean patent application No. 10-2024-0086814, filed on July 2, 2024. FIELD OF INVENTION

[0002] The present invention relates to a pool-type nuclear reactor system with a parallel flow path for residual heat removal, enabling the efficient removal of residual heat generated in a core in the event of a nuclear power plant accident.

[0003] Description of related art

[0004] In the event of an accident, including in the event of a power failure at a nuclear power plant, the nuclear reactor is shut down and the reactor coolant pump which requires a power supply may also be shut down.

[0005] Even after the nuclear reactor is shut down, decay heat continues to be generated inside the core. If all the residual heat, including this decay heat, is not removed, the temperature and pressure of the coolant, including in the core, increase and, in the worst-case scenario, the engineering safety barrier may fail, leading to an accident in which radioactive material leaks to the outside.

[0006] The removal of residual heat is therefore very important to ensure the safety of the nuclear reactor. A residual heat removal system (RHRS) is essential to release the residual heat outside the nuclear reactor after the reactor is shut down. The residual heat removal system must be highly reliable and use a natural circulation phenomenon that does not require a driving force such as a pump.

[0007] As a method for removing residual heat from the core, means for direct reactor auxiliary cooling systems (DRACS), which release the residual heat into the atmosphere using two heat exchangers, and means for reactor vessel auxiliary cooling systems (RVACS), which release the residual heat into the atmosphere through heat exchange by convection and radiation using an outer wall of the nuclear reactor vessel as a heat transfer surface without a heat exchanger, may be considered.

[0008] To release the residual heat generated in the core to the outside, it is necessary first to transfer the residual heat generated in the core to the heat exchanger of the residual heat removal system in the case of DRACS and to a wall surface of the nuclear reactor vessel in the case of RVACS.

[0009] If the nuclear reactor coolant pump is stopped following an accident, the pump's driving force disappears, and the natural circulation flow drive is generated by a density and height difference depending on the coolant's location within the nuclear reactor's main system. The natural circulation flow rate is determined by the balance between the driving force and the flow resistance of the core and the pump in the natural circulation flow path. To maximize the natural circulation flow rate, the nuclear reactor design can take into account factors such as reducing flow resistance, increasing the height difference between the core (the heat source) and the heat sink, and providing an additional driving force.

[0010] However, in the case of the existing concept, if a sufficient natural circulation flow rate through the core is not initially established, or if the fully developed total natural circulation flow rate is less than predicted, there is a problem that a quantity of heat released outside cannot keep up with the residual heat generated in the core, resulting in a continuous increase in the core outlet temperature. Summary of the invention

[0011] The first objective of the present invention is to provide a pool-type nuclear reactor system with a parallel flow path for the removal of residual heat, capable of efficiently establishing a natural circulation flow through a main system to control a rapid increase in maximum temperature at the level of a core outlet, by directly connecting the final heat sink and the core for the removal of residual heat at the beginning of a power failure (or electrical failure) accident in a nuclear power plant.

[0012] The second objective of the present invention is to propose a pool-type nuclear reactor system with a parallel flow path for the removal of residual heat, capable of efficiently reducing core inlet and outlet temperatures by simplifying a heat transfer path from the core to the final heat sink by reducing the time required for the full development of a natural circulation flow.

[0013] To achieve the aforementioned objectives, the present invention discloses a pool-type nuclear reactor system comprising: a normal flow path for circulating coolant configured such that, in normal operation, after low-temperature coolant pumped by a pump located in a low-temperature pool flows into a core inlet plenum, the coolant is heated by passing through the core and is received into a high-temperature pool, and high-temperature coolant located in a high-temperature pool is cooled by passing through an intermediate heat exchanger and is reintroduced into the low-temperature pool;an emergency coolant circulation flow path configured so that, in the event of a power failure (or electrical failure), the high-temperature coolant in the core-heated high-temperature pool is cooled by passing through an auxiliary cooling system and then reintroduced into the core through the pump and core inlet plenum; and a parallel flow path for residual heat removal configured to connect the core inlet plenum and the low-temperature pool and to be connected in parallel to the normal coolant circulation flow path and the emergency coolant circulation flow path.

[0014] The parallel flow path for the removal of residual heat may present a greater resistance to flow than that of the core and the pump.

[0015] According to one embodiment of the present invention, during normal operation, the coolant can separate at the core inlet plenum and flow parallel to the core and a parallel flow path for residual heat removal to flow into the low-temperature pool. In the event of a power failure, the coolant can separate at the low-temperature pool and flow parallel to the pump and the parallel flow path for residual heat removal to flow into the core inlet plenum.

[0016] To achieve the aforementioned objectives, the present invention also discloses a pool-type nuclear reactor system comprising: a normal flow path for circulating coolant configured such that, after low-temperature coolant pumped by a pump located in a low-temperature pool flows into a core inlet plenum, the coolant is heated by passing through the core and is received in a high-temperature pool, and, in normal operation, high-temperature coolant located in a high-temperature pool is cooled by passing through an intermediate heat exchanger and is reintroduced into the low-temperature pool temperature; an emergency coolant circulation flow path configured so that, in the event of an accidental power failure, after the high-temperature coolant located in the core-heated high-temperature pool is reintroduced into the low-temperature pool, the coolant flows into the core inlet plenum through the pump and is cooled during or after the reintroduction process;and a parallel flow path for the removal of residual heat configured to connect the core inlet plenum and the low-temperature pool so that, in normal operation, a portion of the low-temperature coolant located in the core inlet plenum flows to the low-temperature pool and, in the event of an accidental power (or electrical) failure, a portion of the low-temperature coolant located in the low-temperature pool flows to the core inlet plenum.

[0017] To achieve the aforementioned objectives, the present invention also discloses a pool-type nuclear reactor system characterized in that it comprises: a core unit including a core and a core inlet plenum; a high-temperature pool for receiving high-temperature coolant heated by passing through the core; an intermediate heat exchanger for heat exchange with the high-temperature coolant from the high-temperature pool in normal operation; an auxiliary cooling system for cooling the flowing high-temperature coolant in the event of a power (or electricity) failure accident; a low-temperature pool for receiving low-temperature coolant cooled by the intermediate heat exchanger or the auxiliary cooling system;a pump that provides a driving force for the flow of the low-temperature coolant located in the low-temperature pool into the core inlet plenum; and a parallel flow path for waste heat removal that connects the core inlet plenum and the low-temperature pool and permits the flow of the coolant, wherein the parallel flow path for waste heat removal has a predefined resistance to flow such that the coolant can flow from the core inlet plenum to the low-temperature pool in normal operation and flow from the low-temperature pool to the core inlet plenum in the event of a power failure (or electrical failure).

[0018] The present invention has the following effects obtained according to the aforementioned solution.

[0019] First, in the event of an electrical failure, a natural circulation flow is established due to a difference in the density of the coolant between the core and the heat exchanger. The naturally circulating coolant flows parallel to the emergency coolant circulation flow path, through which the coolant flows from the low-temperature pool to the core inlet plenum via the pump, and to the parallel residual heat removal flow path, through which the coolant flows directly from the low-temperature pool to the core inlet plenum. Because the flow resistances are connected in parallel, the total flow resistance is reduced. Therefore, the flow rate through the core increases compared to a single flow path, enabling a rapid increase in the maximum temperature at the core outlet during the initial stage.

[0020] Secondly, since the flow rate through the core increases, the fully developed natural circulation flow rate releases a greater amount of heat outside the nuclear reactor than the newly generated residual heat in the core, which makes it possible to effectively reduce the temperatures at the core inlet and outlet in the long term. Brief description of the drawings

[0021] Fig. 1 represents circuit diagrams showing a flow path of circulating coolant in a nuclear reactor system for the removal of residual heat according to an embodiment of the present invention, Fig. 1(a) represents a circuit diagram showing the flow path of circulating coolant in normal operation, and Fig. 1(b) represents a circuit diagram showing a flow path of circulating coolant in the event of an accident of power failure (or electricity).

[0022] Fig. 2 represents front views of a nuclear reactor comprising an RVACS type auxiliary cooling system according to an embodiment of the present invention, Fig. 2(a) is a conceptual diagram showing a flow of a coolant in normal operation, and Fig. 2(b) is a conceptual diagram showing a flow of a coolant in the event of a power failure (or electricity failure).

[0023] Fig. 3 represents front views of a nuclear reactor comprising an auxiliary cooling system of the DRACS type according to another embodiment of the present invention, Fig. 3(a) is a conceptual diagram showing a flow of a coolant in normal operation, and Fig. 3(b) is a conceptual diagram showing a flow of a coolant in the event of an accident of failure of supply (or electricity).

[0024] Figure 4 is a graph representing a change in the temperature of liquids cooling at the inlet and outlet of the core after a power failure accident (or power outage), which compares an embodiment of the present invention to an embodiment of a single flow path.

[0025] Fig. 5 is a graph representing a quantity of residual heat generated in the core and a quantity of heat released outside through the residual heat removal system after a power failure (or electrical failure) accident, which compares an embodiment of the present invention to a single-flow path embodiment.

[0026] Fig. 6 is a graph representing a change in the temperature of coolant at the inlet and outlet of the core according to a ratio of the area of ​​the parallel flow path for the removal of residual heat compared to the area of ​​the core of the present invention.

[0027] Figure 7 is a table representing a change in flow rate and pump speed. function of a ratio of the area of ​​the parallel flow path for the evacuation of residual heat of the present invention in normal operation.

[0028] Fig. 8 is a graph representing the amount of heat released outside through the waste heat removal system according to the air flow rate at the outer wall of the nuclear reactor vessel in a nuclear reactor comprising an RVACS type auxiliary cooling system, comparing an embodiment of the present invention to a single-flow path embodiment. Fig. 8(a) is a graph for a comparison when the air flow rate at the outer wall of the nuclear reactor vessel is 0.04 kg / s, and Fig. 8(b) is a graph when the air flow rate at the outer wall of the nuclear reactor vessel is 1.00 kg / s. DETAILED DESCRIPTION OF THE INVENTION

[0029] A pool-type nuclear reactor system with a parallel flow path for the removal of residual heat according to the present invention will be described in detail below with reference to the attached drawings.

[0030] In explaining the embodiments disclosed in this document, if it is considered that a detailed description of known related technologies burdens the presentation of the essentials of the embodiments disclosed in this description, then such a description is omitted.

[0031] The accompanying drawings are intended only to facilitate understanding of the embodiments disclosed in this description. The technical ideas disclosed in this description are not limited by the accompanying drawings and it is necessary to It is important to understand that they encompass all modifications, equivalences and substitutions that fall within the spirit and technical scope of the present invention.

[0032] In the present application, the term "includes" or "has" or "contains" is intended to designate the presence of features, numbers, steps, operations, components, parts or combinations thereof described in the description, and it is to be understood that it does not preemptively exclude the possibility of the presence or addition of one or more other numbers, features, steps, operations, components, parts or combinations thereof.

[0033] If it is stated that a certain component is "linked" or "connected" to another component, it should be understood that this component may be directly linked or connected to another component, but that there may be other components between them. Furthermore, if it is stated that a certain component is "directly linked" or "directly connected" to another component, it should be understood that there are no other components between them.

[0034] In this document, identical or similar reference numbers are assigned to identical or similar components in different embodiments, and their redundant description is omitted.

[0035] Fig. 1 represents a coolant circulation flow path in a nuclear reactor system for the removal of residual heat 100 according to an embodiment of the present invention; Fig. 1(a) represents a circuit diagram showing the coolant circulation flow path in normal operation; and Fig. 1(b) represents a circuit diagram showing a coolant circulation flow path in the event of a power failure (or electrical failure). Fig. 2 represents front views of a nuclear reactor comprising an RVACS-type auxiliary cooling system according to an embodiment of the present invention; Fig. 2(a) is a conceptual diagram showing a coolant flow in normal operation; and Fig.[Fig. 3](b) is a conceptual diagram showing the flow of a coolant in the event of a power (or electricity) failure. [Fig. 3] shows front views of a nuclear reactor including a DRACS type auxiliary cooling system according to another embodiment of the present invention; [Fig. 3](a) is a conceptual diagram showing the flow of a coolant in normal operation, and [Fig. 3](b) is a conceptual diagram showing the flow of a coolant in the event of a power (or electricity) failure.

[0036] With reference to Figures 1 to 3, the nuclear reactor system for waste heat removal 100 according to an embodiment of the present invention comprises a normal coolant circulation flow path, an emergency coolant circulation flow path, and a parallel flow path for the removal of residual heat 130.

[0037] The normal flow path of the circulating coolant 110 refers to a flow path through which the coolant flows and circulates sequentially to a pump 116, a core inlet plenum 112, a core 111, a high-temperature pool 113, an intermediate heat exchanger 114, a low-temperature pool 115, and the pump 116 on [Fig. 1](a). The emergency circulating coolant flow path 120 refers to a flow path through which the coolant flows and circulates sequentially to the core 111, the high-temperature pool 113, an auxiliary cooling system 122, the low-temperature pool 115, the pump 116, the core inlet plenum 112, and the core 111 on [Fig. 1](a). l](b).The parallel flow path for the residual heat removal 130 refers to a flow path connecting the core inlet plenum 112 and the low-temperature pool 115 in figures l(a) and l(b).

[0038] In normal operation, the coolant can flow along the normal flow path of the coolant circulation system 110. The normal flow path of the coolant circulation system 110 is located inside a nuclear reactor vessel 200, and its circulation process is as follows.

[0039] The low-temperature coolant is pumped from the pump 116 located in the low-temperature pool 115 and flows into the core inlet plenum 112 of the core unit. The core unit is located inside the low-temperature pool 115 and may consist of the core inlet plenum 112 and the core 111.

[0040] The coolant is subdivided at the core inlet plenum 112 so that a portion of it flows into the core 111 and the remaining portion flows into the parallel waste heat dissipation flow path 130, as will be described below. The remaining portion may be smaller than the aforementioned portion. The core 111 may be located above the core inlet plenum 112.

[0041] The coolant flowing into the core 111 is heated by the heat generated by nuclear fission and is received in the high-temperature pool 113 in a low-density, high-temperature state. The high-temperature pool 113 may be located inside the low-temperature pool 115.

[0042] The coolant received in the high-temperature pool 113 flows into the intermediate heat exchanger 114. An upper end portion of The intermediate heat exchanger 114 is located in the high-temperature pool 113, and a portion of its lower end is located in the low-temperature pool 115, thus 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 introduced from the high-temperature pool 113 can transfer heat to the coolant (second coolant) flowing inside the intermediate heat exchanger 114 and be cooled. The second coolant can then be directed to a secondary system that generates electricity.

[0043] The cooled, low-temperature, high-density coolant is received in the low-temperature pool 115 and can be put into circulation by being reintroduced into the pump 116 located in the low-temperature pool 115.

[0044] In the event of an accident involving a power supply failure (or electrical failure), the coolant can flow along the emergency coolant circulation flow path 120.

[0045] Pump 116 is stopped, which cuts off the drive force of pump 116, but the coolant obtains the drive force arising from a difference in density during heating and cooling.

[0046] The coolant passing through the core 111 passes into a state of high temperature and low density, and rises by buoyancy to flow into the high temperature pool 113.

[0047] The high-temperature coolant received in the high-temperature pool 113 is reintroduced into the low-temperature pool 115, and the coolant is cooled during or after the reintroduction process. The high-temperature coolant flows through the auxiliary cooling system 122 and is cooled to a low-temperature, high-density state.

[0048] The low-temperature coolant is subdivided at the low-temperature pool 115 so that a portion of it flows into the pump 116, and the remaining portion flows into a connecting flow path 130, as will be described below. The remaining portion may be smaller than the aforementioned portion.

[0049] The pump 116 is in a stopped state and can serve as a flow path through which the coolant flows. The coolant passing through the pump 116 is reintroduced into the core 111 through the core inlet plenum 112.

[0050] For example, as shown in [Fig. 2], the auxiliary cooling system 122 can use RVACS means which release residual heat into the atmosphere by heat exchange with the naturally circulating air on a wall surface of the nuclear reactor vessel. In this case, the driving force for the flow of the coolant is generated by a density difference in the coolant resulting from the heating of the coolant in the core 111 and the cooling of the coolant by heat exchange on the wall surface of the nuclear reactor vessel 200.

[0051] The high-temperature coolant passes through the intermediate heat exchanger 114, but flows into the low-temperature pool 115 without heat exchange.Next, after the coolant in the low-temperature pool 115 has been cooled by heat exchange with naturally circulating air through the wall surface of the nuclear reactor vessel 200, the coolant can flow into the pump 116 and the parallel flow path for the removal of residual heat 130, as will be described below, and be put into circulation.

[0052] In the case of RVACS, air cooling means in which the high-temperature coolant inside the nuclear reactor vessel 200 exchanges heat with the air circulating naturally over an external wall surface of the nuclear reactor vessel 200 by convection and radiation are used in an example of the present invention, but water cooling means in which a liquid such as water circulates over the external wall surface of the nuclear reactor vessel 200 and exchanges heat with the internal coolant can also be used.

[0053] In another example, as shown in [Fig. 3], the auxiliary cooling system 122 can use DRACS means that release waste heat into the atmosphere by means of a number of a plurality of heat exchangers of the waste heat removal system that are sequentially connected. In this case, the driving force for the flow of the coolant is generated by a density difference in the coolant resulting from the heating of the coolant in the core 111 and the cooling of the coolant by a heat exchanger 121 of the first waste heat removal system.

[0054] The high-temperature coolant received in the high-temperature pool 113 is cooled by heat exchange with the coolant (third coolant) flowing inside the heat exchanger 121 of the first waste heat removal system located in the pool 113, and then flows into the low-temperature pool 115 in the cooled state, in which the third coolant exchanges heat with the air through a heat exchanger of a second waste heat removal system located outside the nuclear reactor vessel 200 to release residual heat into the atmosphere. The heat exchanger of the second waste heat removal system can be connected to a heat exchanger of another waste heat removal system.

[0055] In the case of the intermediate heat exchanger 114, it can be connected to a configuration, such as a secondary system pump, which provides a driving force for a secondary coolant in the secondary system. In normal operation, the secondary coolant is circulated by the secondary system pump, and the coolant flows into the intermediate heat exchanger 114 to exchange heat with the secondary coolant.In the event of a power (or electrical) failure, the coolant flows into the heat exchanger 121 of the first waste heat removal system to perform heat exchange, thus generating the driving force for the coolant flow, while the intermediate heat exchanger 114 does not perform heat exchange, so the driving force for the coolant flow is lost. Therefore, most of the natural circulation flow paths are formed through the heat exchanger 121 of the first waste heat removal system.

[0056] The present invention is not limited to this. In another example, the auxiliary cooling system 122 may comprise both the RVACS and the DRACS.

[0057] Figure 4 is a graph showing the temperature change of coolant at the inlet and outlet of core 111 after a power failure, comparing an embodiment of the present invention to a single-flow path embodiment. Figure 5 is a graph showing the amount of residual heat generated in core 111 and the amount of heat released to the outside through the residual heat removal system after a power failure, comparing an embodiment of the present invention to a single-flow path embodiment.

[0058] In [Fig. 5], a quantity of heat removal in the conventional concept means a single flow path, and a quantity of heat removal in the new concept passes through a pool-type nuclear reactor system having a parallel flow path for the removal of residual heat according to the present invention. The x-axis represents time (s) based on the occurrence of a power (or electrical) failure accident, and the y-axis is a quantity of residual heat generation and a quantity (%) of heat removal relative to a quantity of initial residual heat generation, which are normalized to unity by dividing by a maximum value of the initial residual heat.

[0059] With reference to Figures 4 and 5 and Figures 1 and 2, the parallel flow path for the removal of residual heat 130 directly connects the core inlet plenum 112 and the low temperature pool 115 and is provided in parallel with the normal coolant circulation flow path 110 and the emergency coolant circulation flow path 120.In the present, the expression "equipped in parallel" means that, from the point of view of the pump 116, which is the drive source, in normal operation, the flow of coolant through the core 111 and the flow of coolant through the parallel flow path for the removal of residual heat 130 are parallel, and that, from the point of view of the core 111, which is the drive source, in the event of an accident of power failure (or electrical failure), the flow of coolant through the pump 116 and the flow of coolant through the parallel flow path for the removal of residual heat 130 are parallel.

[0060] Although the parallel flow path for the removal of residual heat can be understood as a bonding flow path encompassing normal operation and the failure of power (or electricity), the objective of the present invention is to improve the efficiency and safety of the removal of residual heat, as will be described below, and it is therefore named the parallel flow path for the removal of residual heat from the point of view of the failure of power (or electricity).

[0061] The parallel flow path for the residual heat removal 130 has a greater resistance to flow than that of the core 111 and the pump 116, which allows the coolant to flow from the core inlet plenum 112 to the low temperature pool 115 and, vice versa, to flow from the low temperature pool 115 to the core inlet plenum 112.

[0062] In normal operation, the coolant branches out at the core inlet plenum 112 so that part of it flows into the core 111 and the remaining part flows into the parallel flow path for the removal of residual heat 130 in order to form a parallel flow, which mix in the low temperature pool 115.

[0063] Part of the coolant can flow into the parallel flow path for the removal of residual heat 130 with a relatively high resistance value under the effect of the drive force of the pump 116, and the flow thus diverted can be determined according to a ratio of the resistance values ​​of the core 111 and the parallel flow path for the removal of residual heat 130.

[0064] In the event of a power (or electricity) failure, the coolant cannot flow from the core inlet plenum 112 to the parallel flow path for waste heat removal 130, which has a greater resistance than the core 111, since there is no driving force emanating from the pump 116. In this case, the coolant flows from the low-temperature pool 115 to the core inlet plenum 112 through the parallel flow path for waste heat removal 130.

[0065] The coolant is subdivided at the level of the low temperature pool 115 so that part of it flows into the pump 116 and the remaining part flows into the parallel flow path for the evacuation of residual heat 130 to form a parallel flow which merges into the core inlet plenum 112.

[0066] Part of the coolant can flow in the parallel flow path for the removal of residual heat 130 with a relatively high resistance value under the effect of the driving force caused by a difference in density of the coolant in the core 111 and in the auxiliary cooling system 122, and the subdivided flow can be determined according to a ratio of the resistance values ​​of the pump 116 and the parallel flow path for the removal of residual heat 130.

[0067] The operation and effect of the nuclear reactor system for the removal of residual heat 100 in such a configuration will be described.

[0068] In the event of a power (or electricity) failure, the main driving force of the coolant is generated by a density difference that occurs as it passes through the core 111. The coolant passing through the core 111 is received in a high-temperature pool 113 in a high-temperature state, is cooled by an auxiliary cooling system 122, and then branches out at the level of the low-temperature pool 115. The coolant can obtain the driving force under the effect of a density difference during the cooling process.

[0069] Based on the core 111, which is the main drive source, a portion of the coolant is subdivided at the level of the low-temperature pool 115 to flow into the parallel waste heat removal flow path 130, and the remaining portion of the coolant flows into the flow path through the pump 116, thus forming a parallel flow. Since the flow paths are configured in parallel, the total flow resistance decreases. With the reduction in total flow resistance, the natural circulation flow rate of the coolant through the core 111 increases compared to the single flow path under the same conditions, which increases the efficiency of residual heat removal.

[0070] With reference to Figures 4 and 5, which represent the experimental results of a nuclear reactor simulation device according to an embodiment of the present invention, it has been predicted that a maximum temperature at the inlet and outlet of the core 111 in the event of a power failure (or electrical failure) would be lower than the temperature in the case of the existing single flow path, and that the temperature at the inlet and outlet of the core 111 would decrease in the long term. Furthermore, the calculation results indicate that the amount of heat released to the outside by the waste heat removal system according to one embodiment becomes greater than the waste heat generated in the core 111 in the long term, whereas the existing single flow path cannot handle the waste heat under the same conditions and for the same duration.

[0071] In the aforementioned experiment, the auxiliary cooling system of the nuclear reactor corresponds to the RVASC means, and an air flow rate at the level of an outer wall of the nuclear reactor vessel was calculated to be 1.00 kg / s. This calculation was performed using the MARS-LMR computer code developed by the Korea Atomic Energy Research Institute.

[0072] In another embodiment of the present invention, the parallel flow path for waste heat removal 130 can perform the function of a coolant charge and discharge hole which charges the coolant before the nuclear reactor is started up and discharges the coolant at the end of the nuclear reactor's life.

[0073] The parallel flow path for waste heat removal 130 can exist separately from the coolant inlet and outlet. When the coolant is charged before the nuclear reactor is started up, the coolant is introduced from the top of the reactor, and the coolant inlet and outlet serves as a flow path to quickly fill the vessel. However, after the nuclear reactor is started up, it can no longer serve as a flow path for the coolant due to its high resistance.

[0074] The parallel flow path for waste heat removal 130 has a lower flow resistance value than that of the coolant inlet and outlet hole so that it can serve as a flow path through which the coolant can flow in normal operation and in case of an accident of power failure (or electricity).

[0075] Figure 6 is a graph representing a change in the temperature of the coolant at the inlet and outlet of core 111 according to Figure 7 shows a table representing a change in the flow rate and the pump 116 according to a ratio of the area of ​​the parallel flow path for the removal of residual heat 130 to the area of ​​the core 111 of the present invention.

[0076] With reference to Figures 6 and 7, it is preferred that the ratio of the area of ​​the parallel flow path for the removal of residual heat 130 to the area of ​​the core 111 be less than 0.85%.

[0077] If the coolant splits at the core inlet plenum 112 during normal operation and some of it flows into the low-temperature pool 115, the flow rate through the core 111 decreases compared to the existing single flow path, and the cooling efficiency of the core 111 may decrease. To maintain the flow rate through the core 111, the output of the pump 116 must be increased, but if the increase in flow rate (AP) is excessive, the efficiency of the nuclear reactor may decrease.

[0078] If it is calculated that the output of the pump 116 is equal to 110%, which does not exceed the operating margin of 10%, it is preferable that a ratio of the area of ​​the parallel flow path for residual heat removal 130 to the area of ​​the core 111 be less than 0.85%.

[0079] Fig. 8 is a graph representing the amount of heat released outside through the waste heat removal system according to an air flow rate at the outer wall of the nuclear reactor vessel in a nuclear reactor comprising an RVACS type auxiliary cooling system by comparing an embodiment of the present invention to an embodiment of a single flow path, Fig. 8(a) is a graph for a comparison when the air flow rate at the outer wall of the nuclear reactor vessel is 0.04 kg / s, and Fig. 8(b) is a graph for a comparison when the air flow rate at the outer wall of the nuclear reactor vessel is 1.00 kg / s.

[0080] On [Fig.8], a quantity of heat removal of the existing concept means a single flow path, and a quantity of heat removal of the new concept means a nuclear reactor system comprising the parallel flow path for the removal of residual heat 130 according to the present invention.

[0081] In this case, the ratio of the area of ​​the parallel flow path for the removal of residual heat 130 to the area of ​​the core 111 is 0.57%. The x-axis represents the time (s) based on the occurrence of a power (or electrical) failure accident, and the y-axis is a quantity of residual heat generation and a quantity (%) of heat removal relative to a quantity of the generation of initial residual heat, which are normalized to unity by dividing by a maximum value of the initial residual heat.

[0082] With reference to [Fig.8], in a nuclear reactor comprising an auxiliary cooling system of the RVACS means, it is preferable that an air flow rate at the outer wall of the nuclear reactor vessel 200 be 1.00 kg / s or more.

[0083] In the case where the air flow rate at the outer wall of the nuclear reactor vessel 200 is 0.04 kg / s, since the amount of heat released outside by the waste heat removal system is less than the amount of waste heat generated in the core 111 in an embodiment of the present invention and on the single flow path, the calculation result indicated that the inlet and outlet temperatures of the core 111 continue to increase.

[0084] In the case where the air flow rate at the outer wall of the nuclear reactor vessel 200 is 1.00 kg / s, the calculation result indicated that the amount of heat released to the outside by the waste heat removal system according to an embodiment of the present invention becomes greater than the amount of waste heat generated in the core 111 at approximately 40,000 seconds. Furthermore, in the case of the single flow path, the calculation result indicated that the waste heat generated in the core 111 had a value greater than the amount of heat released to the outside by the waste heat removal system, even if the coolant flow rate had increased.

[0085] In another embodiment of the present invention, the parallel flow path for evacuation of residual heat 130 can be provided in various quantities and in various shapes.

[0086] The parallel flow path for waste heat removal 130 reduces the overall flow resistance by allowing the coolant to flow parallel to both the normal coolant circulation flow path 110 and the emergency coolant circulation flow path 120. If multiple parallel flow paths for waste heat removal 130 are provided, the flow resistance can be adjusted according to their shape and arrangement. The flow and temperature distribution can therefore be defined by the designer for both normal operation and a power failure (or electrical failure).

[0087] In another embodiment of the present invention, the parallel flow path for waste heat removal 130 may be provided with a one-way flow restriction mechanism that blocks the flow of coolant through the parallel flow path for waste heat removal 130 in normal operation and allows the coolant Derived from the low-temperature pool 115, the water flows into the core inlet plenum 112 along the parallel flow path for residual heat removal 130 in case of a power supply (or electrical) failure. The one-way flow restriction mechanism can be a check valve.

[0088] 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, so as to be able to block the flow of the coolant from the core inlet plenum 112 to the low-temperature pool 115. In normal operation, the coolant does not flow from the core inlet plenum 112 to the low-temperature pool 115, which makes it possible to increase the flow rate of the coolant through the core 111 without increasing the output of the pump 116.

[0089] If the coolant flows from the low-temperature pool 115 to the core inlet plenum 112 in the event of an accident of power failure (or electricity), the one-way flow restriction mechanism opens so that the parallel flow path for residual heat removal 130 can function as a flow path.

[0090] Since the parallel flow path for waste heat removal 130 is blocked by the unidirectional flow restriction mechanism in normal operation so that there is no loss of coolant flow and therefore no loss of output from the pump 116, the area of ​​the parallel flow path for waste heat removal 130 can be defined to be larger in order to increase the natural circulation flow through the core 111.

[0091] The above description is purely illustrative, and various modifications may These modifications must be made by a person skilled in the art, without deviating from the scope of the technical concept of the implementation methods described. The implementation methods described above can be implemented individually or in combination.

[0092] [Symbol Description]

[0093] 100: Nuclear reactor system for waste heat removal

[0094] 110: Normal coolant circulation flow path

[0095] 111: Core

[0096] 112: Core inlet plenum

[0097] 113: High-temperature pool

[0098] 114: Intermediate heat exchanger

[0099] 115: Low-temperature pool

[0100] 116: Pump

[0101] 120: Emergency coolant circulation flow path

[0102] 121: First waste heat removal system heat exchanger

[0103] 122: Auxiliary cooling system

[0104] 130: Parallel flow path for residual heat removal

[0105] 200: Nuclear reactor vessel

Claims

Demands

1. Pool-type nuclear reactor system comprising: a normal circulating coolant flow path configured such that, in normal operation, after low-temperature coolant pumped by a pump located in a low-temperature pool flows into a core inlet plenum, the coolant is heated by passing through the core and received into a high-temperature pool, and high-temperature coolant located in a high-temperature pool is cooled by passing through an intermediate heat exchanger and reintroduced into the low-temperature pool;an emergency coolant circulation flow path configured so that, in the event of an accident involving a power or electrical failure, the high-temperature coolant located in the high-temperature pool heated by the core is cooled by passing through an auxiliary cooling system and then reintroduced into the core through the pump and the core inlet plenum; and a parallel flow path for residual heat removal configured to connect the core inlet plenum and the low-temperature pool and to be connected in parallel to the normal coolant circulation flow path and the emergency coolant circulation flow path.

2. Pool-type nuclear reactor system according to claim 1, characterized in that the parallel flow path for the removal of residual heat has a greater flow resistance than that of the core and pump.

3. A pool-type nuclear reactor system according to claim 2, characterized in that, under normal operating conditions, the coolant separates at the core inlet plenum and flows parallel to the core and the parallel flow path for residual heat removal to flow into the low-temperature pool, and in that, in the event of a power or electrical failure, the coolant separates at the low-temperature pool and flows parallel to the pump and parallel flow path for the removal of residual heat in order to flow into the core inlet plenum.

4. Pool-type nuclear reactor system according to claim 3, characterized in that the parallel flow path for the removal of residual heat is configured to perform the function of a hole which charges the coolant before the start-up of the nuclear reactor and discharges the coolant at the end of the nuclear reactor's life.

5. Pool-type nuclear reactor system according to claim 4, characterized in that a ratio of the area of ​​the parallel flow path for the removal of residual heat to the area of ​​the core is less than 0.85%.

6. Pool-type nuclear reactor system according to claim 5, characterized in that several parallel flow paths are provided for the removal of residual heat.

7. A pool-type nuclear reactor system according to claim 6, characterized in that the parallel flow path for waste heat removal is provided with a one-way flow restriction mechanism which blocks the flow of coolant through the parallel flow path for waste heat removal in normal operation and allows the coolant separated from the pool at low temperature to flow into the core inlet plenum on the parallel flow path for waste heat removal in the event of a power or electricity failure accident.

8. Pool-type nuclear reactor system according to any one of claims 1 to 7, characterized in that the auxiliary cooling system is a reactor vessel auxiliary cooling system (RVACS) which releases residual heat into the atmosphere by heat exchange with natural circulating air on a wall surface of the reactor vessel.

9. Pool-type nuclear reactor system according to any one of claims 1 to 7, characterized in that the auxiliary cooling system is a direct reactor auxiliary cooling system (DRACS) which releases waste heat into the atmosphere using a number of a plurality of heat exchangers of the waste heat removal system which are connected sequentially.

10. Pool-type nuclear reactor system characterized in that it comprises: a normal circulating coolant flow path configured such that, after low-temperature coolant pumped by a pump located in a low-temperature pool flows into a core inlet plenum, the coolant is heated by passing through the core and is received into a high-temperature pool, and, in normal operation, high-temperature coolant located in a high-temperature pool is cooled by passing through an intermediate heat exchanger and is reintroduced into the low-temperature pool;an emergency coolant circulation flow path configured so that, in the event of an accidental power failure or electrical failure, after the high-temperature coolant located in the core-heated high-temperature pool is reintroduced into the low-temperature pool, the coolant flows into the core inlet plenum through the pump and is cooled during or after the reintroduction process;and a parallel flow path for the removal of residual heat configured to connect the core inlet plenum and the low-temperature pool so that, in normal operation, a portion of the low-temperature coolant located in the core inlet plenum flows to the low-temperature pool and, in the event of an accident involving a power or electrical failure, a portion of the low-temperature coolant located in the low-temperature pool flows to the core inlet plenum.

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

12. Pool-type nuclear reactor system characterized in that it comprises: a core unit comprising a core and a core inlet plenum; a high-temperature pool to receive a high-temperature coolant heated by passing through the core; an intermediate heat exchanger for heat exchange with the high-temperature coolant from the high-temperature pool in normal operation; an auxiliary cooling system to cool the high-temperature coolant being flowed in the event of an accident, power failure or electrical failure; a low-temperature pool for receiving low-temperature coolant cooled by the intermediate heat exchanger or auxiliary cooling system; a pump that provides a driving force for the flow of the low-temperature coolant located in the low-temperature pool into the core inlet plenum; and a parallel flow path for the removal of residual heat that connects the core inlet plenum and the low-temperature pool and allows the flow of the coolant, in which the parallel flow path for the removal of residual heat has a predefined flow resistance so that the coolant can flow from the core inlet plenum to the low-temperature pool in normal operation and flow from the low-temperature pool to the core inlet plenum in the event of an accident of power failure or electrical failure.

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