JP2012251977A - Reactor internal structure and nuclear reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reactor internal structure which makes flow distribution of a fuel assembly stable and uniform by preventing local flow reduction of a coolant.SOLUTION: The reactor internal structure includes: a reactor core barrel 3 provided between a nuclear reactor pressure vessel 1 installed with its axis in a perpendicular direction and a fuel assembly 2; a porous member 14 which is installed under the reactor core barrel 3 and has a plurality of inflow ports 14a formed therein to adjust the flow distribution to the fuel assembly 2 of a primary coolant 12 flowing in through an inlet nozzle 4 of the nuclear reactor pressure vessel 1; and a positioning member 15 for positioning the reactor core barrel 3 in its radial direction. The positioning member 15 is disposed on the downstream side of flow of the primary coolant 12 relative to the porous member 14.

Description

  The present embodiment relates to a reactor internal structure and a nuclear reactor provided with the reactor internal structure.

  In a pressurized water nuclear reactor, the primary coolant introduced to the nuclear reactor is heated by the thermal energy of the fuel assembly of the nuclear reactor and led to the steam generator. In this steam generator, heat exchange is performed between the primary coolant and the secondary coolant heated by the heat energy of the fuel assembly. The secondary coolant boils and generates steam. This steam is guided to the turbine to generate electricity.

  FIG. 13 is a vertical sectional view showing a conventional pressurized water reactor.

  As shown in FIG. 13, a conventional pressurized water reactor mainly includes a reactor pressure vessel 1, a fuel assembly 2 installed in the reactor pressure vessel 1, and a reactor core 3 surrounding the fuel assembly 2. And an inlet nozzle 4 into which the primary coolant 12 flows and an outlet nozzle 5 from which the primary coolant 12 heated by the thermal energy of the fuel assembly 2 flows out.

  The fuel assembly 2 is supported by the lower core support plate 8. An annular channel downcomer 6 is formed between the reactor pressure vessel 1 and the reactor core 3. The downcomer 6 is provided with a radial support 9 for positioning the lower portion of the reactor core 3 in the radial direction with respect to the reactor pressure vessel 1. Further, the lower core support plate 8 is installed so that a cylindrical porous ring 10 is suspended vertically below the lower core support plate 8. A large number of inflow holes are formed in the porous ring 10. These inflow holes are used to adjust the flow distribution of the primary coolant 12 to the core constituted by the fuel assemblies 2. The radial support 9 is disposed in the vicinity of the porous ring 10 and upstream of the flow of the primary coolant 12 with respect to the porous ring 10.

  Next, the flow of the primary coolant 12 will be described with reference to FIG.

  The primary coolant 12 flows into the reactor pressure vessel 1 from a plurality of inlet nozzles 4 installed in the circumferential direction of the reactor pressure vessel 1 and then descends the downcomer 6 in the annular flow path. The descending primary coolant 12 passes through the inflow hole formed in the body portion of the porous ring 10 and joins at the lower plenum 7 formed at the lower portion of the fuel assembly 2 to reverse the flow direction upward. .

  The primary coolant 12 passes through the lower core support plate 8 and ascends the fuel assembly 2 in the core tank 3. The primary coolant 12 heated by the fuel assembly 2 joins and mixes above the fuel assembly 2, flows out from the outlet nozzle 5, and is guided to a steam generator (not shown).

  Next, the primary coolant 12 is heat-exchanged with the secondary cooling water in the steam generator, and the steam generated by boiling the secondary cooling water is guided to a turbine (not shown). On the other hand, the primary cooling water deprived of heat is returned again into the reactor pressure vessel 1 from the inlet nozzle 4 by a coolant circulation pump (not shown).

  In such a pressurized water reactor, if the flow rate and pressure of the primary coolant 12 become non-uniform during normal operation, the cooling effect on the fuel assembly 2 becomes non-uniform. Therefore, it is important to provide the primary coolant 12 evenly distributed in the fuel assembly 2.

  Therefore, in order to make the primary coolant 12 flowing into the fuel assembly 2 uniform in the circumferential direction, the technique described in Patent Document 1 uses an annular boundary flowing from the downcomer 6 into the lower plenum 7 as shown in FIG. A cylindrical perforated ring 10 is installed in a part so as to hang vertically downward from the lower core support plate 8.

  Moreover, although the primary coolant 12 descending the downcomer 6 passes through the radial support 9, a separation vortex is generated at this time. By promoting the separation vortex, the flow rate of the primary coolant 12 flowing into the fuel assembly 2 becomes unstable, and the flow rate distribution becomes uneven. In order to solve this, in the technique described in Patent Document 2, the radial support 9 is formed in a streamline and the vortex generation suppressing member 11 is installed.

JP-A-8-62372 Japanese Patent No. 4202200

  By the way, in the new type reactor, the instrumentation conduit does not penetrate the lower plenum, but is taken out of the reactor pressure vessel at a place other than the lower plenum, and the structure of the lower plenum is simplified. Also, in the new type of reactor, the volume of the lower plenum is smaller than before in order to reduce the size of the reactor pressure vessel. In such a nuclear reactor, there is a problem that the flow distribution of the primary coolant in the lower plenum is difficult to be made uniform, and the flow distribution to the fuel assemblies tends to be non-uniform.

  In the above-described prior art, the radial support 9 installed in the downcomer 6 is installed in the vicinity of the porous ring 10 and upstream of the flow of the primary coolant 12 with respect to the porous ring 10. There is also a problem that the flow rate to the fuel assembly 2 is locally reduced due to the influence of the peeling. Furthermore, in the lower plenum 7, the flow direction of the primary coolant 12 can be changed by 90 degrees. Therefore, there is a problem that the primary coolant 12 is difficult to flow, particularly at the outer peripheral portion of the fuel assembly 2, and the flow rate is likely to decrease.

  On the other hand, when four inlet nozzles 4 are installed in the circumferential direction of the reactor pressure vessel 1, for example, they are equally installed at a phase interval of approximately 90 degrees, and directly open to the space of the downcomer 6 without using a sparger or the like. ing. Therefore, conventionally, there is a problem that the descending flow velocity distribution in the circumferential direction of the downcomer 6 of the spreading flow of the primary coolant 12 flowing into the downcomer 6 from each inlet nozzle 4 is likely to change with time.

  That is, in the conventional configuration, as shown in FIG. 14, the primary coolant 12 entering through the openings of the four inlet nozzles 4 and descending the downcomer 6 is symmetrical in the circumferential cross section near the center between the inlet nozzles 4. As a surface, the flow velocity is high near the symmetry plane, and the flow velocity is low below the opening of the inlet nozzle 4. The flow velocity distribution is maintained up to the portion of the porous ring 10 and affects the circumferential distribution of the amount of inflow from the porous ring 10 to the lower plenum 7. FIG. 14 is a developed view of the downcomer circumferential direction showing the flow of the primary coolant 12 as seen from inside the reactor pressure vessel 1. Moreover, in FIG. 14, the change of the flow-velocity distribution of the primary coolant 12 is shown by the horizontal arrow.

  Further, in the conventional configuration, since the flow is plane-symmetric as shown in FIG. 14, the flow pattern tends to become unstable due to the perturbation of the flow rate of the inlet nozzle 4. As a result, the primary coolant 12 may change in the flow velocity distribution in the circumferential direction of the downcomer 6. If the change in the flow velocity distribution cannot be made uniform by the porous ring 10, the flow rate of the primary coolant 12 supplied to each fuel assembly 2 may change over time, and stable cooling may not be performed. was there.

  An object of the present invention is to provide a reactor internal structure and a nuclear reactor that prevent a local flow rate reduction of a coolant and achieve a stable and uniform flow distribution of a fuel assembly.

  In order to achieve the above object, an in-core structure according to an embodiment of the present invention includes a core tank provided between a reactor pressure vessel and a fuel assembly installed with a shaft as a vertical direction, and the core A porous member installed on the lower side of the tank and formed with a plurality of inflow holes for adjusting the flow distribution of the coolant flowing from the inlet nozzle of the reactor pressure vessel to the fuel assembly, and the radial direction of the core tank And a positioning member for positioning the positioning member, wherein the positioning member is arranged on the downstream side of the flow of the coolant with respect to the porous member.

  A nuclear reactor according to an embodiment of the present invention is provided with a reactor pressure vessel provided with an inlet nozzle for a coolant and having an axis as a vertical direction, a fuel assembly installed in the reactor pressure vessel, In a nuclear reactor comprising a reactor pressure vessel and an in-core structure provided between the fuel assemblies, the in-core structure includes a core tank provided to surround the fuel assemblies, and A porous member that is installed on the lower side of the reactor core and has a plurality of inflow holes for adjusting the flow distribution of the coolant flowing from the inlet nozzle of the reactor pressure vessel to the fuel assembly; and the diameter of the reactor core And a positioning member for positioning the direction, wherein the positioning member is arranged on the downstream side of the flow of the coolant with respect to the porous member.

It is a vertical section lineblock diagram showing a 1st embodiment of an in-furnace structure concerning the present invention. FIG. 2 is a partially enlarged sectional view showing the in-furnace structure of FIG. 1. It is a partial expanded vertical sectional view which shows the modification of the in-furnace structure of 1st Embodiment. It is a vertical section lineblock diagram showing a 2nd embodiment of an in-furnace structure concerning the present invention. FIG. 5 is a partially enlarged sectional view showing the in-furnace structure of FIG. 4. It is a partial expanded sectional view which shows the modification of the in-furnace structure of 2nd Embodiment. It is a vertical section lineblock diagram showing a 3rd embodiment of an in-furnace structure concerning the present invention. It is a horizontal sectional view shown by the inlet nozzle height of the reactor of FIG. It is a downcomer circumferential direction expansion | deployment elevation view which shows the flow of the primary coolant in 3rd Embodiment. It is a downcomer circumferential direction expansion | deployment elevation view which shows the flow of the primary coolant in the modification of 3rd Embodiment. It is a partial expanded sectional view which shows 4th Embodiment of the in-furnace structure which concerns on this invention. It is a partial expanded sectional view which shows the modification of the in-furnace structure of 4th Embodiment. It is a vertical cross-section block diagram which shows the in-core structure of the conventional pressurized water reactor. It is a downcomer circumferential direction expansion | deployment elevation view which shows the flow of the primary coolant in the conventional reactor internal structure.

  Below, each embodiment of the in-furnace structure which concerns on this invention is described with reference to drawings.

  In the following embodiments and modifications, a case where a pressurized water reactor is applied to a nuclear reactor will be described. In the following embodiments and modifications, the same or corresponding parts as those in the conventional configuration will be described with the same reference numerals.

(First embodiment)
(Constitution)
FIG. 1 is a vertical sectional view showing a first embodiment of an in-furnace structure according to the present invention. FIG. 2 is a partially enlarged sectional view showing the in-furnace structure of FIG.

  As shown in FIG. 1, the pressurized water reactor of the present embodiment includes a reactor pressure vessel 1 installed with the axis as a vertical direction, a fuel assembly 2 installed in the reactor pressure vessel 1, Heated by the thermal energy of the fuel assembly 2, the reactor core 3 provided between the fuel assembly 2 and the reactor pressure vessel 1, the inlet nozzle 4 for allowing the primary coolant 12 to flow into the reactor pressure vessel 1 And an outlet nozzle 5 for allowing the primary coolant 12 to flow out of the reactor pressure vessel 1. A plurality of the inlet nozzles 4 are arranged at substantially equal intervals in the circumferential direction of the reactor pressure vessel 1 and directly open to the space of the downcomer 6 that is an annular flow path.

  Further, the pressurized water reactor of the present embodiment includes a lower core support plate 13 that supports the fuel assembly 2 and a porous member as a porous member that is installed below the lower core support plate 13 and formed in a right cylindrical shape. A ring 14 and a radial support 15 as a positioning member that is installed on the lower side of the porous ring 14 and positions the core tank 3 in the horizontal direction are provided.

  A large number of circular inflow holes 14 a for adjusting the flow distribution of the primary coolant 12 to the core constituted by the fuel assembly 2 are formed in the cylindrical body of the porous ring 14. The lower core support plate 13 is fixed to the lower part of the core tank 3. The upper end of the porous ring 14 is fixed to the lower core support plate 13. The core tank 3 is positioned in the radial direction by the radial support 15 via the lower core support plate 13 and the porous ring 14. As a fixing method of each part, for example, there is a method by fastening bolts or welding.

  The radial support 15 is disposed downstream of the flow of the primary coolant 12 with respect to the porous ring 14. Further, as shown in FIG. 2, the radial support 15 has a support seat 16 having an upper end fixed to the porous ring 14 and a lower end fixed to the lower inner surface of the reactor pressure vessel 1, and a peripheral support 15 around the lower inner surface of the porous ring 14. A plurality of saddles 17 are installed along the direction, and a support key 18 is installed so as to fit between the saddle 17 and the support seat 16.

  The support seat 16 is formed in a cylindrical shape, and an annular gap is formed between the upper outer peripheral surface of the support seat 16 and the lower inner peripheral surface of the porous ring 14. A saddle 17 and a support key 18 are disposed in the annular gap. The support seat 16 is configured to be capable of positioning by supporting the core tank 3 via the porous ring 14 and the lower core support plate 13.

(Function and effect)
Next, the operation of the first embodiment configured as described above will be described.

  As shown in FIGS. 1 and 2, the primary coolant 12 flows into the reactor pressure vessel 1 from the inlet nozzle 4 and then descends the downcomer 6 in the annular flow path. The descending primary coolant 12 passes through the inflow hole 14a formed in the cylindrical body of the porous ring 14 and joins at the lower plenum 7 formed at the lower part of the fuel assembly 2 to change the flow direction. Flip upward. The primary coolant 12 passes through the lower core support plate 13 and ascends the fuel assembly 2 in the core tank 3.

  Here, in the present embodiment, the radial support 15 is disposed below the porous ring 14. That is, since the radial support 15 is disposed downstream of the flow of the primary coolant 12 with respect to the porous ring 14, smoothness is provided when the primary coolant 12 descends the downcomer 6 and flows into the porous ring 14. It becomes a flow.

  Further, in the present embodiment, the lower core support plate 13 is fixed to the core tank 3, and the porous ring 14 is fixed and integrated with the lower core support plate 13, so that the radial support 15 is provided below the porous ring 14. It is installed, and the radial support 15 supports the core tank 3 in the radial direction and enables positioning.

  As described above, according to the present embodiment, the radial support 15 is arranged on the downstream side of the flow of the primary coolant 12 with respect to the porous ring 14, so that the upstream portion of the primary coolant 12 flowing into the porous ring 14 is directly upstream. There is no flow separation due to obstacles. As a result, the local flow rate in the circumferential direction of the primary coolant 12 flowing into the fuel assembly 2 does not decrease, and the uniform flow distribution of the fuel assembly 2 can be promoted.

(Modification of the first embodiment)
FIG. 3 is a partially enlarged sectional view showing a modification of the in-furnace structure of the first embodiment. FIG. 3 shows a modification of the radial support 15. In the following embodiments and modifications, the same reference numerals are given to the same parts.

  As shown in FIG. 3, the radial support 15 according to the modification includes a support seat 19 that is partially fixed to the lower inner surface of the reactor pressure vessel 1 and formed with pin holes, and a circumferential direction of the lower surface of the porous ring 14. And a plurality of support pins 20 installed at intervals.

  The support pin 20 is screwed into the lower surface of the porous ring 14 or is fixed by welding. The support pin 20 is positioned by being fitted into a pin hole formed in the support seat 19. On the other hand, the support seat 19 is formed in a cylindrical shape, and an annular gap is formed between the outer surface thereof and the inner surface of the porous ring 14.

  According to this modification, a plurality of radial supports 15 are installed at intervals along the circumferential direction of the lower surface of the perforated ring 14 and the support seat 19 that is partially fixed to the lower inner surface of the reactor pressure vessel 1. The support pin 20 is provided, and the support pin 20 is fitted into a pin hole formed in the support seat 19, whereby the same effect as in the first embodiment can be obtained.

(Second Embodiment)
(Constitution)
FIG. 4 is a vertical sectional view showing a second embodiment of the in-furnace structure according to the present invention. FIG. 5 is a partially enlarged sectional view showing the in-furnace structure of FIG.

  In addition, the same code | symbol is attached | subjected to the part which is the same as that of the said 1st Embodiment and its modification, or it corresponds, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 4, in this embodiment, the porous ring 22 installed on the lower side of the lower core support plate 13 is formed in an inclined cylindrical shape. The inclined cylindrical body portion of the porous ring 22 is formed in a tapered shape that decreases in diameter toward the lower side. The porous ring 22 is formed with a large number of circular inflow holes 22 a for adjusting the flow distribution of the primary coolant 12 to the core constituted by the fuel assembly 2.

(Function and effect)
Next, the operation of the second embodiment configured as described above will be described.

  As shown in FIGS. 4 and 5, the primary coolant 12 flows into the reactor pressure vessel 1 from the inlet nozzle 4 and then descends the downcomer 6 in the annular flow path. The descending primary coolant 12 passes through an inflow hole 22 a formed in the inclined cylindrical body of the porous ring 22 and joins at the lower plenum 7 formed at the lower portion of the fuel assembly 2 to flow direction. Flip up. The primary coolant 12 passes through the lower core support plate 13 and ascends the fuel assembly 2 in the core tank 3.

  Here, in this embodiment, since the radial support 15 is arranged on the downstream side of the flow of the primary coolant 12 with respect to the porous ring 14 as in the first embodiment, the primary coolant 12 moves the downcomer 6. When it descends and flows into the porous ring 22, a smooth flow is obtained.

  Moreover, in this embodiment, since the trunk | drum of the porous ring 22 is formed in an inclined cylindrical shape, and the inclination direction is diameter-lowering, the flow path area of the downstream part of the downcomer 6 becomes large, and a flow pressure loss Less. The inclination angle of the body portion of the porous ring 22 is set such that the primary coolant 12 smoothly flows into the porous ring 22 and the flow pressure loss is reduced.

  As described above, according to the present embodiment, in addition to the effects of the first embodiment, since the body portion of the porous ring 22 is formed in a tapered shape with a diameter decreasing toward the lower side, the flow of the downstream portion of the downcomer 6 is reduced. Since the road area is widened, the flow pressure loss can be reduced.

(Modification of the second embodiment)
FIG. 6 is a partially enlarged sectional view showing a modification of the in-furnace structure of the second embodiment.

  As shown in FIG. 6, this modification is different from the modification of the first embodiment in that the first embodiment is the same as the first embodiment except that the diameter of the body of the porous ring 22 is reduced toward the lower side. Since the configuration and operation are the same as those of the embodiment, description thereof is omitted. A modification of the radial support 15 shown in FIG. 6 can be applied.

(Third embodiment)
(Constitution)
FIG. 7 is a vertical sectional view showing a third embodiment of the in-furnace structure according to the present invention. 8 is a horizontal sectional view showing the height of the inlet nozzle of the nuclear reactor shown in FIG. FIG. 9 is a developed view in the circumferential direction of the downcomer showing the flow of the primary coolant in the third embodiment.

  As shown in FIGS. 7 and 8, in this embodiment, in addition to the configuration of the first embodiment, partition plates 30 as flat plate rectifying plates are arranged in the vicinity of the openings of the four inlet nozzles 4. ing. As shown in FIG. 8, these partition plates 30 have a width direction along the vicinity of the extension line of each inlet nozzle 4 to the downcomer 6 in the horizontal cross section, and at the opening of each inlet nozzle 4 on the downcomer 6 side. They are arranged on the same side.

  Further, as shown in FIG. 7, each partition plate 30 is arranged so that its length direction extends in the vertical direction from the upper surface of the downcomer 6 to a portion exceeding the lower end of the opening on the downcomer 6 side of each inlet nozzle 4.

(Function and effect)
Next, the operation of the third embodiment configured as described above will be described.

  As shown in FIG. 8, the primary coolant 12 flowing from each inlet nozzle 4 is restricted by each partition plate 30 from flowing toward the entire circumference from the opening on the downcomer 6 side of each inlet nozzle 4. .

  Specifically, the primary coolant 12 that has collided with the respective partition plates 30 and the ceiling of the downcomer 6 space changes the direction of flow, and is circumferentially counterclockwise as seen from above the downcomer 6 space as shown in FIG. A flow rate component is obtained. The primary coolant 12 descends while turning around the annular flow path of the downcomer 6. Next, in the porous ring 10, the circumferential flow velocity distribution is made uniform due to the swirl component.

  In addition, since the primary coolant 12 becomes a swirl flow in this way, the flow lines of the primary coolant 12 flowing from the respective inlet nozzles 4 are symmetrical with respect to the vertical plane between the respective inlet nozzles 4 as shown in FIG. Since it does not take a balanced form, the flow in the downcomer 6 is stable, and the change in the flow pattern over time is less likely to occur.

  As described above, according to the present embodiment, the flat partition plates 30 are arranged in the vicinity of the openings of the respective inlet nozzles 4, and the lengths of the partition plates 30 extend from the upper surface of the downcomer 6 to the respective inlet nozzles 4. The downcomer 6 is arranged so as to extend in the vertical direction up to the portion beyond the lower end of the opening on the downcomer 6 side, so that the downward flow of the downcomer 6 is swirled between the partition plate 30 and the upper surface of the downcomer 6. It is possible to stabilize the flow pattern and make the flow rate uniform in the porous ring 14. As a result, the supply of the flow rate from the porous ring 14 to the lower core support plate 13 is stabilized, and the stabilization of the flow rate distribution of the fuel assembly 2 and the uniformization in the circumferential direction can be promoted.

  In addition, although this embodiment demonstrated the case where the porous ring 14 was formed like the said 1st Embodiment, not only this but the case where it forms like the said 2nd Embodiment is applicable.

(Modification of the third embodiment)
FIG. 10 is a development view in the circumferential direction of the downcomer showing the flow of the primary coolant in the modification of the third embodiment.

  As shown in FIG. 10, each partition plate 30 of the present modification is installed by being inclined by θ in the turning direction of the primary coolant 12 with respect to the vertical. That is, each partition plate 30 is installed to be inclined toward each inlet nozzle 4 with respect to the vertical direction of the downcomer 6.

  As described above, according to the modification, each partition plate 30 is inclined by θ in the swiveling direction of the primary coolant 12 with respect to the vertical direction of the downcomer 6, so that a stronger swirl component can be given to the primary coolant 12. Therefore, the circumferential distribution of the primary coolant 12 flowing into the lower plenum 7 from the porous ring 14 can be effectively uniformed.

  This modification can also be applied to the case where the porous ring 14 is formed in the same manner as the modification of the first and second embodiments.

(Fourth embodiment)
(Constitution)
FIG. 11 is a partially enlarged cross-sectional view showing a fourth embodiment of an in-furnace structure according to the present invention. The fourth embodiment shows another example of the porous ring 14 shown in the first embodiment.

  As shown in FIG. 11, the porous ring 14 of the present embodiment has a body portion formed in a right cylindrical shape, like the porous ring 14 of the first embodiment. A large number of circular inflow holes 14 a for adjusting the flow distribution of the primary coolant 12 to the core constituted by the fuel assembly 2 are formed in the cylindrical body of the porous ring 14.

  By the way, the inflow holes 14a of the porous ring 14 of the present embodiment are equally arranged in the circumferential direction, and are formed in a plurality of stages (three stages in the present embodiment) in the height direction. The upper inflow hole 14A in the height direction is formed obliquely upward from the downcomer 6 side to the lower plenum 7 side as shown in FIG.

(Function and effect)
Next, the operation of the fourth embodiment configured as described above will be described.

  Although the flow of the primary coolant 12 flowing down the downcomer 6 is changed in direction by the porous ring 14 and supplied to the core, the flow passage cross-sectional area becomes small at the portion of the inflow hole 14a of the porous ring 14, so that the flow velocity is low. It becomes faster and erupts below the core.

  In general, the primary coolant 12 flowing from the upper inflow hole of the porous ring 14 is supplied to the outer periphery of the core, and the primary coolant 12 flowing from the lower inflow hole is supplied to the center of the core. It tends to be. And since the primary coolant 12 which flows in from the upper inflow hole goes straight through the inflow hole in the horizontal direction, there is a problem that the primary coolant 12 is difficult to be supplied to the outermost core.

  However, in the present embodiment, the flow of the primary coolant 12 flowing into the upper inflow hole 14A of the porous ring 14 flows upward from the downcomer 6 side toward the lower plenum 7 side along the cross section of the opening. Therefore, the primary coolant 12 is more easily supplied to the outer periphery of the core.

  As described above, according to the present embodiment, the inflow holes 14 for adjusting the distribution of the core flow rate are provided in a plurality of stages in the height direction, and the inflow holes 14A in the upper stage in the height direction are connected to the lower plenum 7 from the downcomer 6 side. By being formed obliquely upward toward the side, the primary coolant 12 can be easily supplied to the outer periphery of the core that is difficult to flow, and the flow distribution of the fuel assembly 2 can be more evenly distributed.

(Modification of the fourth embodiment)
FIG. 12 is a partially enlarged sectional view showing a modification of the in-furnace structure of the fourth embodiment.

  As shown in FIG. 12, in this modification, the body portion of the porous ring 22 is formed in an inclined cylindrical shape as in the second embodiment, and the direction of the upper inflow hole 22A in the height direction is the first. Similar to the fourth embodiment, it is formed obliquely upward from the downcomer 6 side toward the lower plenum 7 side.

  With this configuration, according to the present modification, it is possible to obtain actions and effects that combine the second embodiment and the fourth embodiment.

  In the fourth embodiment and the modification thereof, only the upper inflow hole 14A of the porous ring 14 is formed obliquely upward from the downcomer 6 side to the lower plenum 7 side. The inflow holes of at least one of the middle and lower stages may also be formed obliquely upward from the downcomer 6 side toward the lower plenum 7 side.

  Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. 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 modifications thereof are included in the invention described in the claims and equivalents thereof in the same manner as included in the scope and gist of the invention.

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Fuel assembly, 3 ... Core tank, 4 ... Inlet nozzle, 5 ... Outlet nozzle, 6 ... Downcomb, 7 ... Lower plenum, 8 ... Lower core support plate, 9 ... Radial support, 10 ... porous ring, 12 ... primary coolant, 13 ... lower core support plate, 14 ... porous ring (porous member), 14a ... inflow hole, 14A ... upper inflow hole, 15 ... radial support (positioning member), 16 ... Support seat, 17 ... saddle, 18 ... support key, 19 ... support seat, 20 ... support pin, 22 ... perforated ring, 22a ... inflow hole, 22A ... upper inflow hole, 30 ... partition plate (rectifying plate)

Claims (9)

A reactor core tank provided between the reactor pressure vessel and the fuel assembly installed with the axis as a vertical direction;
A porous member that is installed on the lower side of the core tank and has a plurality of inflow holes for adjusting the flow distribution of the coolant flowing from the inlet nozzle of the reactor pressure vessel to the fuel assembly;
A positioning member for positioning the radial direction of the core tank, and a reactor internal structure comprising:
An in-furnace structure characterized in that the positioning member is arranged on the downstream side of the flow of the coolant with respect to the porous member.   The in-furnace structure according to claim 1, wherein the porous member is formed in a cylindrical shape.   The in-furnace structure according to claim 1, wherein the porous member is formed in an inclined cylindrical shape having a diameter reduced downward.   The positioning member includes a support seat having an upper end fixed to the porous member and a lower end fixed to the reactor pressure vessel, a plurality of saddles disposed in a circumferential direction on a lower inner surface of the porous member, and the saddle. And a support key provided between the support seat and the support seat.   The positioning member includes a support seat partly fixed to the reactor pressure vessel and formed with a pin hole, and a plurality of support pins installed in a circumferential direction below the porous member, and the support pin is supported by the support pin. The in-furnace structure according to any one of claims 1 to 3, wherein the inner structure can be fitted into a pin hole of the seat. A plurality of the inlet nozzles are arranged in a plurality of openings that open in an annular flow path formed between the reactor pressure vessel and the reactor core,
The in-furnace structure according to any one of claims 1 to 5, wherein a rectifying plate using a coolant flowing into the annular flow path as a swirl flow is disposed near each of the plurality of openings. object.   The in-furnace structure according to claim 6, wherein the rectifying plate is installed to be inclined with respect to a radial direction of the annular flow path.   In the porous member, inflow holes are formed in a plurality of stages in the height direction at equal intervals in the circumferential direction, and inflow holes in the upper stage in the height direction are formed in the lower part of the fuel assembly from the annular flow path side. The in-furnace structure according to any one of claims 1 to 7, wherein the in-furnace structure is provided obliquely upward toward the lower plenum side. A reactor pressure vessel provided with an inlet nozzle for coolant and installed with the axis in the vertical direction;
A fuel assembly installed in the reactor pressure vessel;
In a nuclear reactor comprising an internal reactor structure provided between the nuclear reactor pressure vessel and the fuel assembly,
The in-furnace structure is
A core tank provided to surround the fuel assembly;
A porous member that is installed on the lower side of the core tank and has a plurality of inflow holes for adjusting the flow distribution of the coolant flowing from the inlet nozzle of the reactor pressure vessel to the fuel assembly;
A positioning member for positioning the radial direction of the core tank,
A nuclear reactor characterized in that the positioning member is arranged on the downstream side of the flow of the coolant with respect to the porous member.

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