JP2013104711A - Liquid metal cooled nuclear reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain holding function of reactor coolant and stably suppress excessive rise in temperature of the reactor coolant even in the face of assumed events such as a double container leakage accident.SOLUTION: A liquid metal cooled nuclear reactor 1 includes a reactor vessel 4, a containment vessel 6 and a containment dome 7 which hermetically contain the reactor vessel 4, an outer concrete structure 17 which surrounds the containment vessel 6 with a storage space surrounding the containment vessel 6 in between, a liner 16 provided on the storage space side of the concrete portion of the outer concrete structure 17, and a temperature rise easing mechanism provided between the liner 16 and the outer concrete structure 17. The temperature rise easing mechanism includes a heat storage section 18 with a heat storage material whose melting point is lower than the temperature of the reactor coolant during the output operation of the liquid metal cooled nuclear reactor 1, and a cooling section 19 for removing heat from the reactor coolant that has leaked from the reactor vessel 4 through the containment vessel 6.

Description

  The present invention relates to a liquid metal cooled nuclear reactor.

  FIG. 5 is an overall configuration diagram of a conventional liquid metal cooled nuclear reactor. As shown in the figure, the liquid metal cooled nuclear reactor has a nuclear fuel core 2 disposed in a reactor vessel 4 filled with a liquid metal 3 such as sodium or sodium potassium alloy as a reactor coolant. The nuclear reactor vessel 4 is stored in a sealed structure including a containment vessel 6 and a containment dome 7. The containment vessel 6 has a gap portion 5 filled with an inert gas therein. The containment vessel 6 is designed so that the leaked liquid metal 3a can be held in the containment vessel 6 even in such a case, assuming an accident in which the liquid metal 3 leaks from the reactor vessel 4.

  The storage container 6 is accommodated in the storage space 12 dug down below the ground surface. The storage space 12 is surrounded by a concrete structure 17 and has an annular space around the storage container 6 and a space below the storage container 6.

  Further, the concrete structure 17 has a liner 16 lining at a portion facing the storage space 12.

  In this liquid metal cooled nuclear reactor 1, it is necessary to stop the nuclear fission reaction in order to cope with an emergency situation during the operation of the reactor or to perform maintenance and inspection. However, since the residual decay heat continues to be generated from the core, it is necessary to remove the heat generated from the liquid metal cooled reactor 1.

  The auxiliary cooling system that removes the residual decay heat is required to have high reliability because of its importance. In the liquid metal cooled nuclear reactor 1, this heat removal method includes a method of cooling the secondary coolant by installing in a secondary cooling system (not shown), a method of cooling the coolant in the reactor vessel 4, and the reactor vessel 4 There is a method of cooling the reactor vessel 4 from the outside.

  FIG. 5 shows a case where, among these methods, the auxiliary cooling system is a reactor vessel auxiliary cooling system (hereinafter referred to as “RVACS”) that cools the reactor vessel 4 from the outside of the reactor vessel 4. .

  Heat from the reactor is transferred from the reactor vessel 4 to the containment vessel 6 by thermal radiation, the temperature of the containment vessel 6 rises, and the heat from the containment vessel 6 is inside the silo formed by the outer liner 16 and the concrete structure 17. And so on. In order to remove the heat of the storage container 6, an RVACS is provided in the annular space between the storage container 6 and the silo.

  Heat is removed by natural convection and air, that is, the atmosphere, is used as a cooling fluid, and the air rises to the outside of the containment vessel 6 and the air descends to the outside of the air rise channel 11. A cylindrical collector 9 is provided in the annular space between the storage container 6 and the silo so as to form the air descending flow path 10.

  As a result, the air in the air ascending channel 11 is heated by the heat of the containment vessel 6, rises through the air ascending channel 11, and is discharged to the outside via the duct 14 from the air discharge port 15.

  In addition, air is taken into the air descending passage 10 of the air cooling passage from the air intake port 13, and the air taken into the air descending passage 10 flows downward through the air descending passage 10 and becomes a silo. Into the storage space 12. Thereafter, the flow direction is changed to flow into the air ascending flow path 11 between the collector 9 and the storage container 6, to flow upward along the outer wall of the storage container 6, and during the heating, the heat of the storage container is released to the outside. .

  As described above, RVACS is a passive auxiliary cooling system that does not use active equipment such as a pump, and thus has higher reliability than the case where active equipment is used.

  In patent document 1, the technique about the air intake port for ensuring said flow path is disclosed.

Japanese Patent Laid-Open No. 6-174848 Japanese Examined Patent Publication No. 62-2277

  In the conventional liquid metal cooled nuclear reactor described above, a virtual event that is unlikely to occur at an extreme, for example, the reactor vessel is damaged, the high-temperature liquid metal in the reactor vessel leaks into the containment vessel, and the containment vessel is also damaged. It is assumed that an accident (hereinafter referred to as “double container leakage accident”) in which high-temperature liquid metal leaks from the containment vessel into the silo further occurs. In this case, the leaked liquid metal is stored in the air cooling channel between the storage container and the silo.

  This stored liquid metal hinders the flow of air in the air cooling flow path, thereby inhibiting the function of RVACS. In addition, since the liquid metal leaked in the silo stays without being removed, the surrounding concrete structure may deteriorate due to overheating, and may expand and crack.

  For example, in the case of sodium, the boiling point of the liquid metal is sufficiently high even at atmospheric pressure of 998 ° C., and remains liquid without boiling under reduced pressure even after leakage. Therefore, even in the case of occurrence of a virtual event such as a double vessel leakage accident, the liquid level in the nuclear reactor necessary for immersing the nuclear fuel core in the nuclear reactor is secured. However, if this state continues, the coolant temperature will gradually increase due to the decay heat generated from the core fuel. In this case, the temperature of the concrete structure around the space where the liquid metal as the coolant is stored also rises. If the concrete temperature rises, the concrete may deteriorate.

  The technology disclosed in Patent Document 2 is not a case of a double vessel leakage accident, but in a liquid metal cooled nuclear reactor of a type in which a concrete containment vessel is installed outside the reactor vessel, concrete in the case where sodium leaks It relates to measures against the temperature rise of the containment vessel. In other words, two types of thermal insulation materials are provided on the inner wall of a concrete containment vessel equipped with a cooling device and a lining. During normal operation, heat insulation is expected to prevent the concrete temperature from rising. It is intended to reduce the effect and improve the heat transfer coefficient for heat removal.

  However, with only the cooling function as disclosed in Patent Document 2, the concrete temperature rapidly rises due to heat input from high-temperature sodium in the initial stage of leakage or due to temporary loss of the cooling function while cooling continues. there is a possibility.

  The present invention has been made to solve the above-described problems. Even if a virtual event such as a double vessel leakage accident is assumed, the reactor coolant retention function is maintained and the reactor coolant is excessively excessive. The purpose is to be able to stably suppress the temperature rise.

  In order to achieve the above-described object, a liquid metal cooled nuclear reactor according to the present invention surrounds a reactor vessel filled with a reactor coolant made of liquid metal, and the periphery and bottom of the reactor vessel. A containment vessel that surrounds an upper part of the reactor vessel and seals and stores the reactor vessel together with the containment vessel, and outer peripheral concrete that surrounds the containment vessel via a storage space surrounding the containment vessel In a liquid metal cooled nuclear reactor comprising a structure and a liner provided to cover the inside of the outer peripheral concrete structure at a position facing the storage space, a temperature provided between the liner and the outer peripheral concrete structure The temperature rise mitigating mechanism is higher than the temperature of the liner during normal operation of the liquid metal cooling reactor, and the liquid A heat storage part having a heat storage material having a melting point lower than the temperature of the reactor coolant during normal operation of the metal-cooled reactor, and heat from the reactor coolant leaked from the reactor vessel through the containment vessel And a cooling part for removing.

  According to the present invention, even if the occurrence of a virtual event such as a double vessel leak accident is assumed, the retention function of the reactor coolant is maintained, and the excessive temperature rise of the reactor coolant is stably suppressed. Can do.

1 is an elevational sectional view showing the overall configuration of a first embodiment of a liquid metal cooled nuclear reactor according to the present invention. 1 is an elevational cross-sectional view showing an overall state of a liquid metal cooled nuclear reactor after a virtual double vessel leakage accident has occurred in a first embodiment of a liquid metal cooled nuclear reactor according to the present invention. It is an elevation sectional view showing the whole composition of a 2nd embodiment of a liquid metal cooling reactor concerning the present invention. It is an elevation sectional view showing the whole situation of a liquid metal cooling reactor after a virtual double vessel leak accident has occurred in the second embodiment of the liquid metal cooling reactor according to the present invention. It is a vertical section lineblock diagram showing the whole conventional liquid metal cooling nuclear reactor.

  Hereinafter, embodiments of a liquid metal cooled nuclear reactor according to the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
FIG. 1 is an elevational sectional view showing the overall configuration of a first embodiment of a liquid metal cooled nuclear reactor according to the present invention.

  In a liquid metal cooled nuclear reactor 1, a nuclear fuel core 2 is disposed in a nuclear reactor vessel 4 filled with a liquid metal 3 such as sodium or sodium potassium alloy as a coolant. The nuclear reactor vessel 4 is stored in a sealed structure including a containment vessel 6 and a containment dome 7. The storage dome 7 is provided in the road upper chamber 8.

  The containment vessel 6 has a gap portion 5 filled with an inert gas such as nitrogen therein. The containment vessel 6 is designed so that the leaked coolant can be held in the containment vessel 6 even in the event of an accident in which the coolant leaks from the reactor vessel 4.

  The storage container 6 is accommodated in the storage space 12 dug down below the ground surface. The storage space 12 is surrounded by a concrete structure 17, and a liner 16 lining is provided on a portion of the concrete structure 17 facing the storage space 12.

  The liner may be made of, for example, ceramics as long as it can store a high-temperature liquid metal in addition to steel and can secure a necessary strength.

  The storage container 6 is formed so as to form an annular air ascending channel 11 in which air rises and an annular air descending channel 10 in which air descends outside the air ascending channel 11 on the outside of the containment vessel 6. A cylindrical collector 9 is provided between the liners 16.

  The downstream side of the air ascending channel 11 is connected to the duct 14, and the upper end of the duct 14 is opened to the atmosphere at the air outlet 15. The duct 14 is provided with an air discharge shut-off valve 22 that is open during normal operation of the liquid metal cooling reactor 1 and is closed when a double vessel leakage accident occurs.

  The air that flows in from the air intake port 13 flows through the air descending flow path 10. The air intake port 13 is provided with an air intake stop valve 21.

  In a region sandwiched between the liner 16 and the concrete structure 17 outside the liner 16 and inside the concrete structure 17, first, a heat storage unit 18 is formed outside the liner 16, and a heat insulating material is formed outside the heat storage unit 18. A heat insulating part 20 is provided. A cooling medium flow path 19 is provided in a state surrounded by the heat insulating section 20 and in contact with the heat storage section 18.

A heat storage material having a melting point lower than about 100 ° C., which is a temperature at which concrete starts to deteriorate, is enclosed in the heat storage unit 18. As such a heat storage material, for example, as hydrated salts, NH ₄ Al (SO ₄ ) ₂ · 12H ₂ O, KAl (SO ₄ ) ₂ · 12H ₂ O, Sr (OH) ₂ · 8H ₂ O, _{Ba (OH) 2 · 8H 2} O, NaCH 3 COO · 3H 2 O , etc. can be used. As the organic _{material, n-Triacontane C 30 H 62} , n-Octacosan C 28 H 58, Propionamide, naphthalene, stearic acid, good in biphenyl.

(Function)
In the liquid metal cooled nuclear reactor 1 configured as described above, normally, the nuclear reactor vessel 4 is filled with the liquid metal 3 at a predetermined normal liquid level Ln, and the nuclear fission in the nuclear fuel core 2 is performed. The generated heat is taken out by circulating the liquid metal 3 as a coolant, and this thermal energy is finally supplied to power generation or the like.

  The cooling air taken in from the air intake port 13 flows downward in the air descending flow path 10, opens to the storage space 12, reverses the direction, and then enters the air rising flow path 11 and flows upward. . The air rising between the containment vessel 6 and the collector 9 in the air ascending flow path 11 rises in temperature by taking heat from the surface of the containment vessel 6 during this time, and the air is discharged from the air discharge port 15 to the outside through the duct 14. Discharge. Here, the flow of cooling air is based on natural convection in which air is heated on the outer wall surface of the containment vessel 6 and flows upward in the air ascending flow path 11.

  FIG. 2 is an elevational sectional view showing the entire state of the liquid metal cooled nuclear reactor after a virtual double vessel leakage accident has occurred in the present embodiment.

  In this case, the liquid metal 3 filled in the reactor vessel 4 up to the normal liquid level Ln leaks from the reactor vessel 4 and the containment vessel 6 into the storage space 12, and the reactor vessel 4 and the containment vessel 6. And accumulates in the storage space 12. As a result, the liquid level of the liquid metal 3 is lowered to the leakage level Lc that is lower than normal.

  On the other hand, when the liquid level of the leaking liquid metal 3a accumulated in the storage space 12 comes above the lower end of the collector 9, the cooling air flow path from the air descending flow path 10 to the air rising flow path 11 is blocked. As a result, the ability to cool the containment vessel 6 from the outside is lost.

  As a result, the liner 16 becomes hot due to the heat from the leaked liquid metal 3 a, and the heat is conducted to the heat storage unit 18. For this reason, when the temperature of the heat storage material of the heat storage unit 18 rises and reaches the melting point, a phase transition (melting) from solid to liquid occurs. During the phase transition, the conducted heat is absorbed by the heat storage material as heat of fusion, so that the temperature of the heat storage material is maintained at the melting point.

  If there is further heat input after all of the heat storage material of the heat storage unit 18 becomes liquid, the temperature of the heat storage unit 18 starts to rise due to the conducted heat, but the cooling medium flow path 19 provided in close contact with the heat storage unit 18. Heat is removed by the cooling medium flowing through it.

  The heat is removed by the cooling medium flowing through the cooling medium flow path 19 and the heat of fusion is released from the heat storage material of the heat storage unit 18 so that the heat storage material changes from liquid to solid, that is, solidifies. By repeating this melting and solidification, the temperature of the heat storage unit 18 can be maintained near the melting point of the heat storage material.

  As described above, the temperature of the heat storage unit 18 is maintained near the melting point of the enclosed heat storage material, and the heat transmitted to the concrete structure 17 is blocked by the heat storage unit 18 and the heat insulating material 20 covering the cooling medium flow path 19. The concrete structure 17 can be prevented from being heated to a temperature at which it begins to deteriorate.

  At this time, by closing the air intake shut-off valve 21 and the air discharge shut-off valve 22, the inflow of oxygen into the air descending flow path 10 and the air ascending flow path 11 is cut off. This prevents the sodium fire from continuing and prevents radioactive fission products and the like leaking from the reactor vessel 4 from leaking directly into the atmosphere.

  As described above, according to the present embodiment, even if a virtual event such as a double vessel leakage accident occurs, the liquid metal cooling reactor 1 is cooled by the cooling medium flowing through the newly configured cooling medium flow path. The heat of the concrete structure 17 can be removed by reliably removing heat from the heat storage part 18 and maintaining the temperature of the heat storage part 18 in the vicinity of the melting point of the heat storage material and blocking heat transmitted to the concrete structure 17 by the heat insulating material of the heat insulating part 20. Temperature rise can be suppressed.

  As a result, the function of holding the leaking liquid metal 3a in the storage space 12 can be maintained, and the temperature rise of the leaking liquid metal 3a and the liquid metal 3 in the reactor vessel 4 can be suppressed.

[Second Embodiment]
FIG. 3 is an elevational sectional view showing the overall configuration of the second embodiment of the liquid metal cooled nuclear reactor according to the present invention.

  The present embodiment is a modification of the first embodiment. In the first embodiment, the cooling medium flow path 19 is provided in close contact with the heat storage section 18, whereas in the present embodiment, the heat storage is performed. The heat pipes 30 are arranged in close contact with the outer periphery of the portion 18.

  Moreover, the heat insulation part 20 is provided so that the heat storage part 18 and the heat pipe 30 may be covered, and the heat storage part 18 and the heat pipe 30 are prevented from contacting the concrete structure 17 directly. The cooling part at the upper end of the heat pipe 30 is provided to be exposed outdoors.

  The working fluid sealed in the heat pipe 30 has a boiling point that is lower than the melting point of the heat storage material in the heat storage unit 18 and higher than the temperature at which it is exposed and cooled outdoors. Examples of such a working fluid include water having an operating temperature of 0 ° C. to 200 ° C., ethanol having an operating temperature of −10 ° C. to 130 ° C., and methanol having an operating temperature of −20 ° C. to 130 ° C.

(Function)
FIG. 4 is an elevational sectional view showing the entire state of the liquid metal cooled nuclear reactor after a virtual double vessel leakage accident has occurred in the present embodiment.

  When a double vessel leakage accident occurs, the liquid level of the liquid metal 3 in the reactor vessel 4 drops to a leakage level Lc that is lower than normal and the liquid level higher than the lower end of the collector 9 is stored in the storage space. 12 and the air flow path outside the storage container 6 is blocked, and the cooling function is lost.

  As a result, the liner 16 becomes hot due to the heat from the leaked liquid metal 3 a, and the heat is conducted to the heat storage unit 18. For this reason, when the temperature of the heat storage material of the heat storage unit 18 rises and reaches the melting point, a phase transition (melting) occurs from the solid to the liquid. During the phase transition, the conducted heat is absorbed by the heat storage material as heat of fusion, so that the temperature of the heat storage material is maintained at the melting point.

  If there is further heat input after all of the heat storage material of the heat storage unit 18 has become liquid, the temperature of the heat storage unit 18 begins to rise due to the conducted heat, but the heat in the heat pipe 30 provided in close contact with the heat storage unit 18 The heat storage unit 18 is deheated by the occurrence of a cycle in which the working fluid evaporates and the evaporated working medium releases heat at a portion where the heat pipe 30 is exposed to the outside and is cooled and returned to liquid.

  By removing heat, heat of fusion is released from the heat storage material of the heat storage unit 18 and the heat storage material is solidified. By this melting and solidification cycle, the temperature of the heat storage unit 18 is maintained near the melting point of the enclosed heat storage material. Thus, the temperature increase inside the heat insulation part 20 is suppressed by the heat storage part 18 and the heat pipe 30. Furthermore, by reducing the heat transmitted to the concrete structure 17 by the heat insulating portion 20 installed outside the heat pipe 30, it is possible to prevent the concrete structure 17 from being heated to a temperature at which it begins to deteriorate.

  Moreover, as a result of closing the air intake shutoff valve 21 and the air discharge shutoff valve 22, radioactive fission products and the like leaking from the reactor vessel 4 are prevented from leaking directly into the atmosphere.

  As described above, according to the present embodiment, even if a virtual event such as a double vessel leakage accident occurs, the cooling medium flowing through the newly configured cooling medium flow path causes the liquid metal cooling reactor to Heat can be reliably removed, and the temperature of the heat storage part is maintained near the melting point of the heat storage material, and heat transmitted to the concrete structure 17 is blocked by the heat insulating material of the heat insulating part 20, thereby overheating the concrete structure 17 Deterioration can be prevented.

  As a result, the function of holding the leaking liquid metal 3a in the storage space 12 can be maintained, and the temperature rise of the leaking liquid metal 3a and the liquid metal 3 in the reactor vessel 4 can be suppressed.

[Other Embodiments]
As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention.

  For example, the air flow paths connected to the air descending flow path 10 and the air rising flow path 11 partitioned by the collector 9 may be different, or may be applied to a nuclear reactor that uses another gas instead of air. Further, the storage space itself may not be an annular space but may have a planar shape such as a rectangle.

  The cooling place of the heat pipe 30 is not limited to the outdoors, and the cooling method may not be air cooling but may be an external reservoir, for example.

  Moreover, you may combine the characteristic of each embodiment. For example, the first embodiment and the second embodiment may be combined to include both cooling means for the cooling medium flow path and the heat pipe.

  Furthermore, these embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Liquid metal cooling reactor 2 ... Nuclear fuel core 3 ... Liquid metal 3a ... Leakage liquid metal 4 ... Reactor vessel 5 ... Gap part 6 ... Containment vessel 7 ... -Storage dome 8 ... Furnace upper chamber 9 ... Collector 10 ... Air descending flow path 11 ... Air rising flow path 12 ... Storage space 13 ... Air intake 14 ... Duct DESCRIPTION OF SYMBOLS 15 ... Air exhaust port 16 ... Liner 17 ... Concrete structure 18 ... Heat storage part 19 ... Coolant flow path (cooling part)
DESCRIPTION OF SYMBOLS 20 ... Heat insulation part 21 ... Air intake shut-off valve 22 ... Air discharge shut-off valve 30 ... Heat pipe (cooling part)
Ln ... Normal liquid level position Lc ... Leak liquid level position

Claims (8)

A reactor vessel filled with a reactor coolant made of liquid metal;
A containment vessel provided to surround the periphery and bottom of the reactor vessel;
A containment dome that surrounds an upper portion of the reactor vessel and hermetically stores the reactor vessel together with the containment vessel;
A peripheral concrete structure surrounding the containment vessel via a storage space surrounding the containment vessel;
A liner provided to cover the inside of the outer peripheral concrete structure at a position facing the storage space;
In a liquid metal cooled nuclear reactor comprising:
Comprising a temperature rise mitigating mechanism provided between the liner and the peripheral concrete structure;
The temperature rise mitigation mechanism is
A heat storage part having a heat storage material having a melting point higher than the temperature of the liner during normal operation of the liquid metal cooling reactor and lower than the temperature of the reactor coolant during normal operation of the liquid metal cooling reactor;
A cooling section for removing heat from the reactor coolant leaked from the reactor vessel through the containment vessel;
A liquid metal cooled nuclear reactor.   2. The liquid metal cooled nuclear reactor according to claim 1, wherein the temperature increase mitigation mechanism includes a heat insulating portion between the heat storage portion and the cooling portion and the outer peripheral concrete structure.   3. The cooling unit according to claim 1, wherein the cooling unit includes a cooling medium flow path that contains a cooling medium that is supplied from outside and absorbs heat from the reactor coolant and then returns to the outside. Liquid metal cooled reactor.   The said cooling part has a heat pipe arrange | positioned so that it may operate | move by the heat absorption from the said reactor coolant, and the heat discharge | release in external air atmosphere, The one of Claim 1 thru | or 3 characterized by the above-mentioned. The liquid metal cooled nuclear reactor according to the item.   5. The liquid metal according to claim 4, wherein a part of the heat pipe is installed in close contact with the heat storage part, extends upward from the contacted part, and has an upper end exposed to the outdoors. Cooling reactor.   The liquid metal cooled nuclear reactor according to claim 4 or 5, wherein a working fluid having a boiling point equal to or lower than a melting point of the heat storage material is enclosed in the heat pipe.   The liquid metal cooled nuclear reactor according to any one of claims 1 to 6, wherein the heat storage material has a melting point lower than a deterioration temperature of the concrete forming the outer peripheral concrete structure.   An air intake that is in a flow path that communicates between the storage space and the outside, is open except when the reactor coolant leaks, and is closed when the reactor coolant leaks to close the storage space The liquid metal cooled nuclear reactor according to any one of claims 1 to 7, further comprising a shut-off valve and an air discharge shut-off valve.

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