JP4392412B2 - Channel forming device and natural circulation boiling water reactor - Google Patents

Description

  The present invention relates to a natural circulation boiling water reactor, and more particularly to a flow path forming device in a chimney of a nuclear reactor.

  In natural circulation boiling water reactors, the coolant circulation path in the reactor pressure vessel is formed by using a cylindrical chimney cylinder provided at the top of the core and a core shroud surrounding the core. ing. The coolant is lowered to a descending passage called a downcomer between the outer peripheral surface of the core shroud and chimney and the inner surface of the reactor pressure vessel, and the coolant is placed on the inner passage of the core shroud and inside the chimney. And the coolant is circulated in the reactor pressure vessel by naturally circulating the coolant.

  Since the natural circulation boiling water reactor is equipped with such a circulation channel in the reactor pressure vessel, the coolant heated by the heat from the nuclear reaction in the reactor core is a gas-liquid two-phase liquid and vapor. Ascending in the ascending flow path from the core through the chimney as a phase flow, the gas-liquid two-phase flow is separated into liquid and steam by the steam separator, and the steam is sent to the turbine outside the reactor pressure vessel Supplied and liquid is sent to the downflow channel.

  In the descending flow path, the coolant is colder than the coolant in the chimney and does not contain steam, so the density is large, and the coolant descends by natural circulation force based on this density difference. The descending coolant flow begins to rise at the bottom of the reactor pressure vessel, and the coolant enters the core again from below and is heated and raised. Thus, the coolant can be naturally circulated without using a pump (see, for example, Patent Document 1 and Patent Document 2).

  In order to improve the natural circulation force of the coolant, the ascending flow path in the chimney is divided into a plurality of upright lattice flow paths by a flow partition wall in the chimney, and rises from the core into the multiple lattice flow paths. There is also an example in which the gas-liquid two-phase flow is flowed to raise the coolant (see, for example, Patent Document 3).

Japanese Patent Laid-Open No. 08-094793 Japanese Patent Laid-Open No. 06-265665 Japanese Patent Publication No. 07-027051

  When a plurality of upright grid channels partitioned in a grid pattern are provided in the chimney, when a gas-liquid two-phase flow flows in the grid channels, a pressure fluctuation load is applied to the channel partition walls constituting the grid channels. I understood it.

  The gas-liquid two-phase flow that flows as a mixture of liquid and vapor develops as it rises, and the central part of each lattice channel is occupied by vapor in the vapor phase. An annular flow is generated in which the vapor and the liquid flow in a separated state so that there is a liquid that is in the liquid phase. Before and after this annular flow, like the bamboo node, the liquid fills the cross section of the flow path and divides the vapor developed at the center. Such a gas-liquid two-phase flow becomes a flow pattern close to a churn flow, and a pressure fluctuation load is applied to the flow path partition wall.

  And it turned out that a flow path partition may vibrate by this pressure fluctuation load. This vibration may have a long-term adverse effect such as damage on the joint between the flow path partition walls for partitioning the lattice flow paths by the flow path partition walls.

  In order to suppress this vibration, it is only necessary to disperse the pressure fluctuation load. Therefore, it is conceivable to configure the channel partition so that the cross-sectional size of the lattice channel is uniform. Causes an increasing problem.

  Accordingly, an object of the present invention is to provide a flow path forming device and a natural circulation boiling water reactor capable of suppressing vibration of a flow path partition wall while reducing the volume of the flow path partition wall.

The basic requirements of the flow path forming apparatus and the natural circulation boiling water reactor of the present invention are arranged in a chimney installed above the core in the reactor pressure vessel and provided above the center of the core. A first flow path through which the coolant from the core flows, and a cross-sectional area disposed in the chimney and provided above the periphery of the core, the coolant flowing from the core flows and perpendicular to the flow direction of the coolant There have a said first flow path is greater than the second flow path, the cross section perpendicular to the flow direction of the coolant of the first flow path is a first rectangular, of the coolant of the second flow path The cross section perpendicular to the flow direction is the second rectangle, and the length of the longest side of the first rectangle is shorter than the length of the longest side of the second rectangle .

  ADVANTAGE OF THE INVENTION According to this invention, the flow path formation apparatus and natural circulation boiling water reactor which can suppress a vibration of a flow path partition can be provided, reducing the quantity of a flow path partition.

(Outline of natural circulation boiling water reactor)
Next, a natural circulation boiling water reactor 1 according to an embodiment of the present invention will be described in detail with reference to FIG. In general, there are two ways to drive coolant (light water) in boiling water reactors, one is forced circulation using a recirculation pump, and the other is natural without using a recirculation pump. It is a method by circulation. This embodiment is the latter method based on natural circulation.

  In the natural circulation method, the coolant is accommodated in the reactor pressure vessel 6, and the coolant is heated in the core 7 accommodated in the reactor pressure vessel 6 to generate steam from the liquid. Thus, the driving force necessary for natural circulation is obtained by the specific gravity difference between the mixed low density coolant and the liquid coolant mixed with the feed water supplied from the feed water pipe 16b.

  In the natural circulation boiling water reactor 1, a core shroud 8 is provided in a cylindrical shape in a cylindrical reactor pressure vessel 6 in a concentric cylindrical shape. The core shroud 8 forms an annular space in the gap between the outer surface thereof and the inner surface of the reactor pressure vessel 6, and this is referred to as a downcomer 9. Further, the core 7 in which a large number of fuel assemblies 21 are arranged is housed inside the core shroud 8.

  Above the downcomer 9, the coolant supplied from the feed water inlet nozzle 17 into the reactor pressure vessel 6 after being heated by the feed water heater 5 from the condenser 3 through the feed water pump 4 is not shown. A water supply sparger is provided in an annular shape. The core shroud 8 is supported by a shroud leg 8a. The coolant descending the downcomer 9 is introduced from the flow path between the shroud legs 8 a into the core lower plenum 10 below the core 7.

  A core support plate 22 is provided at the lower part of the core 7 and an upper lattice plate 23 is provided at the upper part to determine the lateral arrangement of the fuel assemblies 21 and the control rods 24. The core support plate 22 is provided with circular through holes (not shown) at predetermined intervals. A control rod guide tube 25 is inserted into the through holes, and the lower portion of the control rod guide tube 25 is the bottom of the reactor pressure vessel 6. And a control rod drive mechanism housing 26a that accommodates a control rod drive mechanism 26 that moves the control rod 24 in the vertical direction.

  The fuel assembly 21 is placed on a fuel support bracket (not shown) attached to the upper end of the control rod guide tube 25, and the load is applied to the reactor pressure via the control rod guide tube 25 and the control rod drive mechanism housing 26a. It is transmitted to the bottom of the container 6.

  The fuel support fitting has a coolant inlet on a side surface, and an orifice (not shown) is provided therein to regulate the coolant flow rate. An opening is provided in the side surface of the control rod guide tube 25 corresponding to the coolant inlet of the fuel support bracket, and the coolant guided to the core lower plenum 10 is guided into the fuel assembly 21 through the fuel support bracket. Each fuel assembly 21 is surrounded by a rectangular tube channel box (not shown) to form individual flow paths in the axial direction, and the channel box is configured to reach the upper surface of the upper lattice plate 23. The control rod 24 has an effective portion containing a neutron absorbing material (not shown), and the effective portion is inserted between the surrounding four fuel assemblies 21 using the outer surface of the channel box as a guide.

  Further, an LPRM (Local Power Range Monitor) detector assembly 33 that includes a plurality of neutron detectors and measures the neutron flux in the output region is arranged in the core 7. The lower part of the LPRM detector assembly 33 is accommodated in an in-core nuclear instrument housing 33a that passes through a through hole provided in the bottom of the pressure vessel 6, and a signal cable extends from the lower end of the in-core nuclear instrument housing 33a.

  Provided on the core 7 is a chimney 11 that secures a flow path that guides the gas-liquid two-phase flow coolant flowing out from the core 7 upward, promotes convection of the coolant, and increases the natural circulation driving force. ing. The chimney 11 has a cylindrical chimney cylinder 11d concentric with the reactor pressure vessel 6, and has a flow path forming device 11a for forming lattice flow paths C0 and C1 by partitioning with a flow path partition wall R therein. is doing. In addition, the upper plenum 11c is provided in the upper part of the chimney 11 so that the coolant flowing upward through the individual lattice channels C0 and C1 merges in the upper part of the chimney 11. The upper lattice plate 23 and the lower end of the chimney 11 have a combined structure in which the coolant that descends the downcomer 9 and the coolant that rises from the core 7 are not mixed.

  The upper end of the chimney 11 is closed by the shroud head 12a. The shroud head 12a is provided with a predetermined number of coolant passage holes, and the holes are provided in the steam / water separator 12 for separating the steam / saturated water and the steam / steam from the gas / liquid two-phase flow through the stand pipe 12b. linked. A steam dryer 13 is provided above the steam / water separator 12 to remove moisture contained in the saturated steam exiting the steam / water separator 12, and the steam dome 14, steam outlet nozzle 15, main steam pipe 16a. Then, saturated steam is sent to the turbine 2. Note that the shroud head 12a, the stand pipe 12b, and the steam / water separator 12 are integrally assembled, and can be integrally removed from the upper end of the chimney 11 when the fuel is changed.

  In the natural circulation boiling water reactor 1, the coolant supplied from the feed water inlet nozzle 17 is mixed with the saturated water separated by the steam separator 12 and descends the downcomer 9 in the direction A. The coolant flows into the core shroud 8 from a flow path formed by a gap (not shown) of the shroud leg 8 a and is heated by the core 7. By heating from the core 7, the coolant becomes a saturated gas-liquid two-phase flow flowing in the directions B1 and B2. This gas-liquid two-phase flow reaches the steam-water separator 12 via the lattice channels C0 and C1, the upper plenum 11c, and the stand pipe 12b. The steam-water separator 12 causes the saturated steam flowing in the direction C and the direction D to flow. Separated into flowing saturated water. The separated saturated steam passes through the steam dryer 13 and is led from the steam outlet nozzle 15 to the turbine 2 through the main steam pipe 16a to be used for power generation.

  On the other hand, the separated saturated water is mixed with the coolant in the reactor pressure vessel 6, further mixed with the coolant supplied from the feed water inlet nozzle 17, descends the downcomer 9 again, and the reactor pressure vessel 6. Circulate inside.

(Chimni structure)
As shown in FIGS. 2A and 2B, the chimney 11 includes a chimney cylinder 11d and a flow path forming device 11a. The chimney cylinder 11d has a cylindrical shape, and a flow path forming device 11a having rectangular lattice flow paths C0, C1, and C2 as viewed from above is disposed in a space in the cylinder.

  As shown in FIG. 2A and FIG. 3, the flow path forming device 11a is set with column lines R1 to R9 that are parallel at equal intervals and row lines L1 to L9 that are parallel at equal intervals. it can. The intervals between the column lines R1 to R9 are equal to the intervals between the row lines L1 to L9. The column lines R1 to R9 and the row lines L1 to L9 intersect at right angles. The column line R5 and the row line L5 pass through the vicinity of the center of the cylinder of the chimney cylinder 11d.

  Then, a plurality of square areas A1 to A15 surrounded by two adjacent column lines and two adjacent row lines and having a congruent relationship can be set. Note that the chimney 11 has a cylindrical shape, and if only a quarter circle is considered, other regions can be analogized by the symmetry of the circle, so the regions A1 to A15 having the same sign are arranged symmetrically.

  One lattice channel C0 is formed in each of the regions A1, A2, A5, A6, A11, A12, and A15. One lattice channel C1 is formed in a region extending over the four regions A3, A4, A7, and A8. One lattice channel C2 is formed in a region extending over the four regions A9, A10, A13, and A14.

  First, in order to form the lattice flow path C0, flow path partition walls R1 to R9 are arranged in the flow path forming device 11a so as to be parallel to each other at equal intervals on the column lines R1 to R9. . In the flow path forming device 11a, flow path partition walls L1 to L9 are arranged on the row lines L1 to L9 so as to be parallel to each other at equal intervals. For convenience, the column lines R1 to R9, the row lines L1 to L9, and the flow path partitions R1 to R9 and L1 to L9 have a one-to-one correspondence. The interval between the channel partition walls R1 to R9 is equal to the interval between the channel partition walls L1 to L9. The channel partitions R1 to R9 and L1 to L9 are metal plates, and the lattice channel C0 is formed by joining the channel partitions R1 to R9 and the channel partitions L1 to L9 by welding or the like. . The flow path forming device 11a has a welded structure.

  Next, in order to form the lattice channel C1, the channel partition walls that separate the regions A3, A4, A7, and A8 from each other are removed. Specifically, the channel partition L4 between the channel partition walls R1 and R3 and between the channel partition walls R7 and R9 is removed, and between the channel partition walls R1 and R3 and between the channel partition walls R7 and R9. The flow path partition L6 between the flow path partition walls L3 and L7 is removed, and the flow path partition wall R8 between the flow path partition walls L3 and L7 is removed.

  Further, in order to form the lattice channel C2, the channel partition walls separating the regions A9, A10, A13, and A14 from each other are removed. Specifically, the flow path partition L2 between the flow path partition walls R3 and R7 is removed, the flow path partition wall L8 between the flow path partition walls R3 and R7 is removed, and between the flow path partition walls L1 and L3, The channel partition R4 between the channel partition L7 and L9 is removed, and the channel partition R6 between the channel partition L1 and L3 and between the channel partition L7 and L9 is removed.

  As described above, the regions A1 to A15 in the chimney 11 are partitioned in a lattice shape, and a plurality of lattice channels C0, C1, and C2 having different sizes upright above the core 9 are formed. The coolant from the core 7 flows through the lattice channels C0, C1, and C2.

  The lattice channel C0 is provided in the central portion of the chimney 11. The center part may include a region A1 and a region adjacent to the region A1. The lattice channels C1 and C2 are provided in the periphery of the chimney 11. The peripheral part is located outside the central part. The cross-sectional area perpendicular to the coolant flow direction B2 in FIG. 1 of the lattice channels C1 and C2 is larger than the cross-sectional area perpendicular to the coolant flow direction B1 of the lattice channel C0. The cross section perpendicular to the coolant flow direction B1 in the lattice channel C0 is rectangular, and the cross section perpendicular to the coolant flow direction B2 in the lattice channels C1 and C2 is also rectangular. The length of the longest side of the rectangle of the lattice channel C0 is shorter than the length of the longest side of the rectangles of the lattice channels C1 and C2.

  The coolant flow in the reactor pressure vessel 6 is divided into a downward flow in the direction A of FIG. 1 at the downcomer 9 and an upward flow in the directions B1 and B2 inside the core 7 and chimney 11, and the upward flow is Since the steam generated in the core 7 is included, the density is smaller than that of the downflow. Therefore, there is a head pressure difference between the downcomer 9 and the inside of the chimney 11, and the coolant descends the downcoma 9, reverses and rises from the core lower plenum 10, and flows into the core 7. Thus, the natural circulation boiling water nuclear reactor 1 causes convection using the density difference of the coolant, and naturally circulates the coolant. The density of the coolant in the chimney 11 is not uniform in the radial direction of the chimney 11 although it is lowered by the steam. This is because the amount of heat generated in the core 7 is high in the central part of the core 7 and low in the peripheral part. Due to the temperature distribution in the cross section of the core 7, the coolant is heated from the peripheral part at the central part. And a coolant produces more vapor | steam than a peripheral part in a center part, and a density becomes low. The difference in water head pressure with the downcomer 9 is greater in the center than in the periphery. The flow rate of the coolant is higher in the upward flow in the center direction B1 than in the peripheral direction B2.

  That is, as shown in FIG. 4, in the chimney 11, the flow rate of the coolant is the fastest at the center and becomes slower as it goes from the central part to the peripheral part. Thus, if there is a slow distribution in the flow velocity, the direction of the directions B1 and B2 is bent and the upward flow is disturbed in the absence of the channel partitions R1 to R9 and L1 to L9, and the upward flow velocity is increased. It will decline. By providing the flow path partition walls R1 to R9 and L1 to L9 in the chimney 11, the flow velocity in each of the flow paths C0, C1, and C2 partitioned by the chimney 11 is determined by the flow path partition walls R1 to R9 and L1 to L9. The slow speed distribution becomes smaller and the flow velocity of the upward flow does not decrease.

  On the other hand, even if the flow velocity has a slow distribution, if the flow velocity is slow as a whole, turbulence in the upward flow can be suppressed. If attention is paid to the peripheral part of the chimney 11, it is considered that the entire peripheral part has a low flow velocity. Therefore, in the peripheral portion, the turbulence of the upward flow is small even without the flow path partition walls R1 to R9 and L1 to L9. Therefore, the peripheral partition walls R1 to R9 and L1 to L9 can be omitted. The lattice channels C1 and C2 arranged in the peripheral part can be set to have a larger cross-sectional area than the lattice channel C0 arranged in the central part.

  As described above, when the lattice channels C0, C1, and C2 are provided in the chimney 11, the upward flow is a gas-liquid two-phase flow, so that the flow pattern is close to the churn flow, and the channel partition walls R1 to R9. , L1 to L9 are distributed loads due to pressure fluctuation loads.

  As shown in FIG. 5, the distributed load is the largest in the chimney 11 at the center where the amount of generated steam is large, and becomes smaller as it goes from the central part to the peripheral part. When the distributed load is large, the flow path partition walls R1 to R9 and L1 to L9 vibrate greatly. If the vibration is large, there is a possibility that the joints between the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 may be adversely affected such as damage in the long term. In order to eliminate damage to the joint, it is only necessary to reduce the distance between the flow path partitions R1 to R9 and the distance between the flow path partitions L1 to L9 to reduce the load applied to the joint. On the contrary, if the distance between the flow path partition walls R1 to R9 and the distance between the flow path partition walls L1 to L9 are set to such an extent that the load applied to the joint portion can be sufficiently reduced, Since the load applied to the joint portion is further lower than the central portion, the mutual distance between the flow path partition walls R1 to R9 and the mutual distance between the flow path partition walls L1 to L9 can be increased from the central portion. That is, in the peripheral part, even if the mutual distance between the flow path partition walls R1 to R9 and the mutual distance between the flow path partition walls L1 to L9 are increased from the central part, the load applied to the joint part is about the same as that in the central part. It can be set smaller. Therefore, the peripheral partition walls R1 to R9 and L1 to L9 can be omitted, and the lattice channels C1 and C2 arranged in the peripheral part have a cross-sectional area larger than the lattice channel C0 arranged in the central part. Can be set large. Further, the length of the longest side of the rectangular cross section of the lattice channels C1 and C2 can be set longer than the length of the longest side of the rectangular cross section of the lattice channel C0.

  As shown in FIG. 6, the arrangement of the flow path partition walls R5 to R9 and the flow path partition walls L1 to L5 is related to the layout of the fuel assemblies 21 and the control rods 24 in the core 7. FIG. 6 shows the arrangement of the fuel assemblies 21 and the control rods 24 in the cross section of the core 7 and the arrangement of the flow path partitions R5 to R9 and the flow path partitions L1 to L5 in the cross section of the chimney 11. It is.

  Four fuel assemblies 21 are arranged in a 2 × 2 arrangement, and a cross-shaped control rod 24 is inserted into a cross-shaped gap formed by the four fuel assemblies 21. A control rod cell having the four fuel assemblies 21 and the inserted fuel rods 24 as unit cells is configured. In the areas A1 to A15, four control rod cells are arranged in a 2 × 2 array. That is, 16 fuel assemblies 21 are arranged in a 4 × 4 arrangement in each of the regions A1 to A15. Further, the fuel assemblies 21 and the control rods 24 are arranged in accordance with the arrangement of the control rod cells also in the region surrounded by the chimney cylinder 11d and the flow path partition walls R5 to R9 and L1 to L5. Since the channel partition walls R5 to R9 and the channel partition walls L1 to L5 are arranged so as to divide the regions A1 to A15, the channel partition walls R5 to R9 and the channel partition walls L1 to L5 are connected to the fuel assembly 21. The arrangement is such that it does not cross over the control rod 24. By arranging in such a manner not to cross, the fuel assembly 21 and the control rod 24 of the core 7 can be carried out of the reactor pressure vessel 6 through the lattice channels C0, C1, and C2. That is, when the fuel assemblies 21 and the control rods 24 are loaded and withdrawn from the core 7, there is no need to take out the flow path partition walls R 1 to R 9 and the flow path partition walls L 1 to L 9 from the reactor pressure vessel 6.

  Therefore, according to the embodiment of the present invention, the cross-sectional areas of the lattice channels C0, C1, and C2 in the chimney 11 are non-uniform, and the areas of the peripheral lattice channels C1 and C2 are set to the central lattice. By making the area larger than the area of the flow path C0, the amount of metal members of the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 can be reduced without increasing the fluid vibration due to the pressure fluctuation load, and the material / manufacturing cost can be reduced. Can be reduced. Since the number of joints between the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 is also reduced, the time required for processing / welding / assembly can be reduced.

(Modification 1 of arrangement of flow path partition walls R1 to R9, L1 to L9)
FIG. 7 shows a modified example of the arrangement of the channel partition walls R1 to R9 and L1 to L9. The difference from the arrangement in FIG. 3 is that the lattice channel C3 is newly formed in a region extending over the three regions A11, A12, and A15.

  Then, in order to form the lattice flow path C3, the flow path partition walls that separate the regions A11, A12, and A15 from each other are removed. Specifically, the flow path partition walls L2 and L8 between R2 and R3 and between R7 and R8 are removed, and the flow path partition wall R2 between L2 and L3 and between L7 and L8. R8 is removed.

  As described above, the lattice channel C3 is newly formed, and the coolant from the core 7 flows into the lattice channel C3. The lattice channel C3 is provided in the peripheral portion of the chimney 11 in the same manner as the lattice channels C1 and C2. The cross-sectional area perpendicular to the coolant flow direction B2 in FIG. 1 of the lattice channel C3 is larger than the cross-sectional area perpendicular to the coolant flow direction B1 of the lattice channel C0. Further, the length of the longest side of the hexagon in the cross section of the lattice channel C3 is longer than the length of the longest side of the rectangle of the lattice channel C0. In the peripheral part of the chimney 11, the flow velocity is generally slow throughout the peripheral part, and the turbulence of the upward flow is small even without the flow path partition walls R1 to R9 and L1 to L9. Therefore, the peripheral partition walls R1 to R9 and L1 to L9 can be omitted, and the lattice channels C1, C2, and C3 disposed in the peripheral portion are crossed from the lattice channel C0 disposed in the central portion. The area can be set large.

  In addition, the gas-liquid two-phase flow that flows through the lattice channels C0, C1, C2, and C3 has a flow mode close to a churn flow, and a distributed load due to a pressure fluctuation load is applied to the channel partition walls R1 to R9 and L1 to L9. Since the load applied to the joint between the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 is lower in the peripheral portion than the central portion, the distance between the flow path partition walls R1 to R9 and the flow path partition wall The distance between L1 to L9 can be increased from the center. Therefore, the peripheral partition walls R1 to R9 and L1 to L9 can be omitted, and the lattice channels C1, C2, and C3 arranged in the peripheral portion are more transverse than the lattice channel C0 arranged in the central portion. The area can be set large. Further, the length of the longest side of the figure of the cross section of the lattice channels C1, C2, and C3 can be set longer than the length of the longest side of the rectangle of the cross section of the lattice channel C0. Further, the fuel assembly 21 and the control rod 24 of the core 7 can be carried out of the reactor pressure vessel 6 through the lattice channel C3.

  Therefore, according to the first modification of the embodiment of the present invention, the cross-sectional areas of the lattice channels C0, C1, C2, and C3 in the chimney 11 are non-uniform, and the lattice channels C1, C2, and By making the area of C3 larger than the area of the grid flow path C0 in the central part, the quantity of the metal members of the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 without increasing the hydrodynamic vibration due to the pressure fluctuation load Can be further reduced, and the material / manufacturing cost can be further reduced. Since the joints between the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 are further reduced, the time required for processing / welding / assembly can be further reduced.

(Modification 2 of arrangement of flow path partition walls R1 to R9, L1 to L9)
FIG. 8 shows a modified example of the arrangement of the channel partition walls R1 to R9 and L1 to L9. 7 differs from the arrangement of the modification 1 of FIG. 7 in that the lattice channel C3 combines the lattice channel C3 and the lattice channel formed between the lattice channel C3 and the chimney cylinder 11d. In the description on FIG. 8, the lattice channel C3 is eliminated.

  Then, in order to enlarge the lattice flow path C3 in FIG. 7, the flow path partition walls that separate the areas A12 and A15 from the outer area are removed as shown in FIG. Specifically, the flow path partition L1 between R2 and R3, between R7 and R8 is removed, the flow path partition L2 between R1 and R2, and between R8 and R9 is removed, and R1 Between R2 and R2, between R8 and R9, the flow path partition L8 is removed, between R2 and R3, between R7 and R8, the flow path partition L9 is removed, and between L2 and L3. , The flow path partition R1 between L7 and L8 is removed, the flow path partition R2 between L1 and L2, and the flow path partition R2 between L8 and L9 is removed, between L1 and L2, and between L8 and L9. The flow path partition R8 between them is removed, and the flow path partition R9 between L2 and L3 and between L7 and L8 is removed. As a result, the lattice channel C3 in FIG. 7 is consequently expanded to the chimney cylinder 11d in FIG.

  Therefore, according to the second modification of the embodiment of the present invention, since the area of the lattice channel C3 in the peripheral portion is further enlarged, not only the effect of the first modification is obtained but also the flow path partition walls R1 to R1. The amount of metal members of R9 and the flow path partition walls L1 to L9 can be further reduced, and the material / manufacturing cost can be further reduced. Since the joints between the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 are further reduced, the time required for processing / welding / assembly can be further reduced.

(Modification 3 of arrangement of flow path partition walls R1 to R9, L1 to L9)
FIG. 9 shows a modified example of the arrangement of the flow path partitions R1 to R9 and L1 to L9. A difference from the arrangement of FIG. 3 is that lattice channels C4 to C7 are newly formed instead of the lattice channels C1 and C2. The lattice channel C4 is formed across two adjacent regions A4. The lattice channel C5 is formed in a region extending over two regions A8 and A12. The lattice channel C6 is formed in a region extending over the two regions A14 and A15. The lattice channel C7 is formed over two adjacent regions A13. A lattice channel C0 is formed in each of the other regions A1 to A3, A5 to A7, and A9 to A11.

  And in order to form the lattice flow path C4, the flow path partition which separates two adjacent area | regions A4 from each other is removed. Specifically, the flow path partition L5 between R1 and R2 and between R8 and R9 is removed.

  In order to form the lattice channel C5, the channel partition that separates the region A8 and the region A12 from each other is removed. Specifically, the channel partition walls L3 and L7 between R1 and R2 and between R8 and R9 are removed.

  In order to form the lattice channel C6, the channel partition that separates the region A14 and the region A15 from each other is removed. Specifically, the channel partition walls R3 and R7 between L1 and L2 and between L8 and L9 are removed.

  In order to form the lattice channel C7, the channel partition that separates the two adjacent regions A13 from each other is removed. Specifically, the flow path partition R5 between L1 and L2 and between L8 and L9 is removed.

  As described above, the lattice channels C4 to C7 are newly formed, and the coolant from the core 7 flows into the lattice channels C4 to C7. The lattice channels C4 to C7 are provided in the peripheral portion of the chimney 11 in the same manner as the lattice channels C1 and C2. The cross-sectional area of the lattice channels C4 to C7 is larger than the cross-sectional area of the lattice channel C0. The cross sections of the lattice channels C4 to C7 are rectangular, and the length of the longest side of the rectangle is longer than the length of the longest side of the rectangle of the lattice channel C0. In the peripheral part of the chimney 11, the flow velocity is generally slow throughout the peripheral part, and the turbulence of the upward flow is small even without the flow path partition walls R1 to R9 and L1 to L9. Therefore, the peripheral flow partition walls R1 to R9 and L1 to L9 can be omitted, and the lattice flow paths C4 to C7 arranged in the peripheral portion can be separated from the lattice flow path C0 arranged in the central portion in a cross-sectional area. Can be set large.

  In addition, the gas-liquid two-phase flow that flows through the lattice channels C0, C4 to C7 has a flow pattern close to that of the churn flow, and distributed loads due to pressure fluctuation loads are applied to the channel partition walls R1 to R9 and L1 to L9. Since the load applied to the joint portion between the partition walls R1 to R9 and the flow path partition walls L1 to L9 is lower in the peripheral portion than the central portion, the distance between the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9. The space | interval of L9 can mutually be expanded from a center part. Therefore, the peripheral partition walls R1 to R9 and L1 to L9 can be omitted, and the lattice channels C4 to C7 arranged in the peripheral part have a cross-sectional area larger than the lattice channel C0 arranged in the central part. Can be set large. Further, the length of the long side of the rectangular cross section of the lattice channels C4 to C7 can be set longer than the length of the longest side of the rectangular cross section of the lattice channel C0. Further, the fuel assembly 21 and the control rod 24 of the core 7 can be carried out of the reactor pressure vessel 6 through the lattice channels C4 to C7.

  Therefore, according to the third modification of the embodiment of the present invention, the cross-sectional areas of the lattice channels C0, C4 to C7 in the chimney 11 are made non-uniform, and the areas of the peripheral lattice channels C4 to C7 are By making it larger than the area of the lattice flow path C0 in the central part, the amount of metal members of the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 can be reduced without increasing the hydrodynamic vibration due to the pressure fluctuation load, Material / manufacturing costs can be reduced. Since the number of joints between the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 is also reduced, the time required for processing / welding / assembly can be reduced.

(Modification 4 of arrangement of flow path partition walls R1 to R9, L1 to L9)
FIG. 10 shows a modified example of the arrangement of the channel partition walls R1 to R9 and L1 to L9. A difference from the arrangement of FIG. 3 is that lattice channels C8 and C9 are newly formed instead of the lattice channels C1 and C2. The lattice channel C8 is formed in a region extending over the three regions A4, A8, and A12. The lattice channel C9 is formed in a region extending over the three regions A13, A14, and A15. A lattice channel C0 is formed in each of the other regions A1 to A3, A5 to A7, and A9 to A11.

  Then, in order to form the lattice channel C8, the channel partition walls that separate the regions A4, A8, and A12 from each other are removed. Specifically, the flow path partitions L3, L4, L6, and L7 between R1 and R2 and between R8 and R9 are removed.

  In order to form the lattice channel C9, the channel partition walls that separate the regions A13, A14, and A15 from each other are removed. Specifically, the flow path partition walls R3, R4, R6, and R7 between L1 and L2 and between L8 and L9 are removed.

  As described above, the lattice channels C8 and C9 are newly formed, and the coolant from the core 7 flows into the lattice channels C8 and C9. The lattice channels C8 and C9 are provided in the peripheral part of the chimney 11 like the lattice channels C1 and C2. The cross-sectional area of the lattice channels C8 and C9 is larger than the cross-sectional area of the lattice channel C0. The cross sections of the lattice channels C8 and C9 are rectangular, and the length of the longest side of the rectangle is longer than the length of the longest side of the rectangle of the lattice channel C0. In the peripheral part of the chimney 11, the flow velocity is generally slow throughout the peripheral part, and the turbulence of the upward flow is small even without the flow path partition walls R1 to R9 and L1 to L9. Therefore, the peripheral partition walls R1 to R9 and L1 to L9 can be omitted, and the lattice channels C8 and C9 arranged in the peripheral part can be separated from the lattice channel C0 arranged in the center by a cross-sectional area. Can be set large.

  In addition, the gas-liquid two-phase flow flowing through the lattice channels C0, C8, and C9 has a flow pattern close to that of the churn flow, and distributed loads due to pressure fluctuation loads are applied to the channel partition walls R1 to R9 and L1 to L9. Since the load applied to the joint portion between the partition walls R1 to R9 and the flow path partition walls L1 to L9 is lower in the peripheral portion than the central portion, the distance between the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9. The space | interval of L9 can mutually be expanded from a center part. Therefore, the peripheral flow partition walls R1 to R9 and L1 to L9 can be omitted, and the lattice flow paths C8 and C9 arranged in the peripheral part have a larger cross-sectional area than the lattice flow path C0 arranged in the central part. Can be set large. Further, the length of the long side of the rectangular cross section of the lattice channels C8 and C9 can be set longer than the length of the longest side of the rectangular cross section of the lattice channel C0. Further, the fuel assembly 21 and the control rod 24 of the core 7 can be carried out of the reactor pressure vessel 6 through the lattice channels C8 and C9.

  Therefore, according to the fourth modification of the embodiment of the present invention, the cross-sectional areas of the lattice channels C0, C8 and C9 in the chimney 11 are made non-uniform and the areas of the peripheral lattice channels C8 and C9 are By making it larger than the area of the lattice flow path C0 in the central part, the amount of metal members of the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 can be reduced without increasing the hydrodynamic vibration due to the pressure fluctuation load, Material / manufacturing costs can be reduced. Since the number of joints between the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 is also reduced, the time required for processing / welding / assembly can be reduced.

(Modification 5 of arrangement of flow path partition walls R1 to R9, L1 to L9)
FIG. 11 shows a modified example of the arrangement of the channel partition walls R1 to R9 and L1 to L9. A difference from the arrangement of the modification 2 of FIG. 8 is that lattice channels C10 and C11 are newly formed instead of the lattice channels C1 and C2. The lattice channel C10 is formed in a region extending over two regions A4 and A8. The lattice channel C11 is formed in a region extending over two regions A13 and A14. A lattice channel C0 is formed in each of the other regions A1 to A3, A5 to A7, A9, and A10.

  Then, in order to form the lattice channel C10, the channel partition walls that separate the regions A4 and A8 from each other are removed. Specifically, the flow path partitions L4 and L6 between R1 and R2 and between R8 and R9 are removed.

  In order to form the lattice channel C11, the channel partition that separates the regions A13 and A14 from each other is removed. Specifically, the flow path partitions R4 and R6 between L1 and L2 and between L8 and L9 are removed.

  As described above, the lattice channels C10 and C11 are newly formed, and the coolant from the core 7 flows into the lattice channels C10 and C11. The lattice channels C10 and C11 are provided in the peripheral part of the chimney 11 like the lattice channels C1 and C2. The cross-sectional area of the lattice channels C10 and C11 is larger than the cross-sectional area of the lattice channel C0. The cross sections of the lattice channels C10 and C11 are rectangular, and the length of the longest side of the rectangle is longer than the length of the longest side of the rectangle of the lattice channel C0. In the peripheral part of the chimney 11, the flow velocity is generally slow throughout the peripheral part, and the turbulence of the upward flow is small even without the flow path partition walls R1 to R9 and L1 to L9. Therefore, the peripheral partition walls R1 to R9 and L1 to L9 can be omitted, and the lattice channels C10 and C11 disposed in the peripheral portion can be separated from the lattice channel C0 disposed in the center by a cross-sectional area. Can be set large.

  In addition, the gas-liquid two-phase flow flowing through the lattice channels C0, C10, and C11 has a flow pattern close to a churn flow, and distributed flow due to pressure fluctuation load is applied to the channel partition walls R1 to R9 and L1 to L9. Since the load applied to the joint portion between the partition walls R1 to R9 and the flow path partition walls L1 to L9 is lower in the peripheral portion than the central portion, the distance between the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9. The space | interval of L9 can mutually be expanded from a center part. Therefore, the peripheral flow partition walls R1 to R9 and L1 to L9 can be omitted, and the lattice flow paths C10 and C11 disposed in the peripheral portion have a larger cross-sectional area than the lattice flow path C0 disposed in the central portion. Can be set large. Further, the length of the long side of the rectangular cross section of the lattice channels C10 and C11 can be set longer than the length of the longest side of the rectangular cross section of the lattice channel C0. Further, the fuel assembly 21 and the control rod 24 of the core 7 can be carried out to the outside of the reactor pressure vessel 6 through the lattice channels C10 and C11.

  Therefore, according to the fifth modification of the embodiment of the present invention, the cross-sectional areas of the lattice channels C0, C10 and C11 in the chimney 11 are non-uniform, and the areas of the lattice channels C10 and C11 in the peripheral portion are By making it larger than the area of the lattice flow path C0 in the central part, the amount of metal members of the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 can be reduced without increasing the hydrodynamic vibration due to the pressure fluctuation load, Material / manufacturing costs can be reduced. Since the number of joints between the flow path partition walls R1 to R9 and the flow path partition walls L1 to L9 is also reduced, the time required for processing / welding / assembly can be reduced.

(Modification 6 of arrangement of flow path partition walls R1 to R9, L1 to L9)
FIG. 12 shows a modified example of the arrangement of the channel partition walls R1 to R9 and L1 to L9. A difference from the arrangement of the first modification shown in FIG. 7 is that lattice channels C101 to C104 are newly formed in the area A1 instead of the lattice channel C0. The four lattice channels C101 to C104 are arranged 2 × 2 in the region A1. Referring to region A1 in FIG. 6, control rod cells each including four fuel assemblies 21 and fuel rods 24 inserted therein are disposed at each one of the grid channels C101 to C104. Is arranged.

  Then, in order to form the lattice channels C101 to C104, channel partition walls R10 and L10 that further divide the region A1 are formed. Specifically, a flow path partition R10 positioned between the flow path partition walls R4 and R5 and between the flow path partition walls R5 and R6 is added between L4 and L6. Between R4 and R6, a flow path partition L10 located between the flow path partition walls L4 and L5 and between the flow path partition walls L5 and L6 is added.

  As described above, the lattice channels C101 to C104 are newly formed, and the coolant from the core 7 flows into the lattice channels C101 to C104. The lattice channels C101 to C104 are provided at the center of the chimney 11. The cross-sectional areas of the lattice channels C101 to C104 are smaller than the cross-sectional area of the lattice channel C0. The cross sections of the lattice channels C101 to C104 are rectangular, and the length of the longest side of the rectangle is shorter than the length of the longest side of the rectangle of the lattice channel C0.

  In the central part of the chimney 11, the flow velocity is high, and as the speed increases further, the turbulence of the upward flow is large even with the flow path partition walls R1 to R9 and L1 to L9. Therefore, channel partition walls R10 and L10 are further added to the central region A1. The lattice channels C101 to C104 arranged in the central part are arranged further than the lattice channels C1, C2 and C3 arranged in the peripheral part, and further in the intermediate part between the central part and the peripheral part. From C0, the cross-sectional area can be set smaller.

  In addition, the gas-liquid two-phase flow that flows through the lattice channels C0, C1, C2, C3, C101 to C104 has a flow pattern close to a churn flow, and distributed loads due to pressure fluctuation loads are applied to the channel partitions R1 to R9 and L1 to L9. However, the load applied to the joint portion by the flow path partition walls R10 and L10 can be made as low as the intermediate portion and the peripheral portion in the central portion. This is because the length of the long side of the rectangular cross section of the lattice channels C101 to C104 is set shorter than the length of the longest side of the rectangular shape of the cross section of the lattice channels C0, C1, C2, and C3. It is. Further, the fuel assembly 21 and the control rod 24 of the core 7 can be carried out to the outside of the reactor pressure vessel 6 through the lattice channels C101 to C104.

  Therefore, according to the sixth modification of the embodiment of the present invention, the cross-sectional areas of the lattice channels C0, C1, C2, C3, C101 to C104 in the chimney 11 are non-uniform, and the lattice channels in the peripheral portion By changing the area of C1, C2, and C3 to be larger than the area of the intermediate lattice flow path C0 and making the area of the central lattice flow paths C101 to C104 smaller than the area of the intermediate lattice flow path C0, pressure fluctuations Although the quantity of the metal members of the flow path partition walls R10 and L10 increases without increasing the hydrodynamic vibration due to the load, the total amount of the metal members of the flow path partition walls R1 to R10 and the flow path partition walls L1 to L10 can be reduced. , Material / manufacturing costs can be reduced.

1 is a longitudinal sectional view of a natural circulation boiling water reactor 1 according to an embodiment of the present invention. (A) is a top view of the chimney 11, and (b) is a longitudinal sectional view in the II-II direction of (a). It is an arrangement drawing of a lattice channel and a channel partition of channel formation device 11a concerning one embodiment of the present invention. It is a graph which shows the flow rate of the coolant which flows through the lattice flow path arrange | positioned in area | region A1 thru | or A4 between flow-path partition L4 and L5. It is a graph which shows the distributed load applied to the flow path partition L5 of area | region A1 thru | or A4, when a coolant flows into a lattice flow path. FIG. 3 is an arrangement view showing the arrangement of fuel assemblies 21 and control rods 24 in the cross section of the core 7 and the arrangement of the flow path partition walls of the flow path forming device 11a in the cross section of the chimney 11. FIG. It is an arrangement drawing of a lattice channel and a channel partition of channel formation device 11a concerning one embodiment of the present invention. It is an arrangement drawing of a lattice channel and a channel partition of channel formation device 11a concerning one embodiment of the present invention. It is an arrangement drawing of a lattice channel and a channel partition of channel formation device 11a concerning one embodiment of the present invention. It is an arrangement drawing of a lattice channel and a channel partition of channel formation device 11a concerning one embodiment of the present invention. It is an arrangement drawing of a lattice channel and a channel partition of channel formation device 11a concerning one embodiment of the present invention. It is an arrangement drawing of a lattice channel and a channel partition of channel formation device 11a concerning one embodiment of the present invention.

Explanation of symbols

6 reactor pressure vessel 7 core 8 core shroud 9 downcomer 11 chimney 11a flow path forming device 11d chimney cylinder 21 fuel assembly 24 control rods A1 to A15 regions C0 to C11, C101 to C104 grid flow paths R, R1 to R10, L1 To L10 Channel bulkhead

Claims (7)

A first flow path disposed in a chimney equipped above a core in a reactor pressure vessel, provided above a central portion of the core, and through which a coolant from the core flows;
A second flow that is disposed in the chimney and is provided above the periphery of the core, the coolant flows from the core, and a cross-sectional area perpendicular to the flow direction of the coolant is larger than the first flow path. Road and
A cross section perpendicular to the coolant flow direction in the first flow path is a first rectangle, a cross section perpendicular to the coolant flow direction in the second flow path is a second rectangle, and the first rectangle The length of the longest side is shorter than the length of the longest side of the second rectangle, and the flow path forming device in the chimney of the nuclear reactor .   The coolant is provided above the central portion and the peripheral portion of the core, the coolant flows from the core, and the cross-sectional area perpendicular to the flow direction of the coolant is larger than the first flow path. The flow path forming apparatus according to claim 1, further comprising a third flow path smaller than the flow path. The cross section perpendicular to the flow direction of the coolant in the third flow path is a third rectangle, and the length of the longest side of the first rectangle is shorter than the length of the longest side of the third rectangle. The flow path forming device according to claim 2. A reactor pressure vessel capable of containing coolant;
A reactor core disposed within the reactor pressure vessel to heat the coolant and generate steam from a liquid;
In a natural circulation boiling water reactor having a chimney disposed above the core in the reactor pressure vessel and promoting convection of the liquid,
The chimney is
A first flow path provided above a central portion of the core and through which coolant from the core flows;
Provided above the periphery of the core, the coolant flows from the core, and has a second flow path whose cross-sectional area perpendicular to the flow direction of the coolant is larger than the first flow path,
A cross section perpendicular to the coolant flow direction in the first flow path is a first rectangle, a cross section perpendicular to the coolant flow direction in the second flow path is a second rectangle, and the first rectangle length of the longest sides, natural circulation boiling water reactor and being shorter than the length of said second rectangular longest side of.   The coolant is provided above the central portion and the peripheral portion of the core, the coolant flows from the core, and the cross-sectional area perpendicular to the flow direction of the coolant is larger than the first flow path. The natural circulation boiling water reactor according to claim 4, wherein the chimney further has a third flow path smaller than the flow path. The cross section perpendicular to the flow direction of the coolant in the third flow path is a third rectangle, and the length of the longest side of the first rectangle is shorter than the length of the longest side of the third rectangle. The natural circulation boiling water nuclear reactor according to claim 5, The fuel assembly of the core can be carried out of the reactor pressure vessel through the first flow path or the second flow path. The natural circulation boiling water reactor described in 1.

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