JP6272794B2 - Improved boiling water reactor - Google Patents

Description

  The present invention relates to an improved boiling water reactor that is a light water reactor, and more particularly to a method for supplying purge water to an internal pump.

  Patented to capture the clad and foreign matter that circulate in the reactor of the advanced boiling water reactor (ABWR) and reduce the amount of suction of the clad and foreign matter into the internal pump. Document 1 has been proposed. Patent Document 1 discloses a method of making a portion for depositing clad and foreign matter around the hydraulic part of an internal pump installed in a reactor pressure vessel and capturing the clad and foreign matter circulating in the reactor. Yes. As a result, the clad and foreign matter in the reactor pressure vessel are captured by the depositing site, and the equipment is damaged by the circulation and contact of the clad and foreign matter in the hydraulic part of the internal pump and the reactor pressure vessel. It is possible to reduce the risk of

Japanese Patent Laid-Open No. 2003-14879

However, although Patent Document 1 discloses a method for reducing clad and foreign matter that circulates in the reactor in ABWR, it is related to a method for reducing clad and foreign matter that flows from the outside such as a water injection line and a purge water line. Is not considered at all.
Accordingly, the present invention provides an improved boiling water reactor that can reduce the cladding flowing into the internal pump and enable safe operation of the reactor.

In order to solve the above problems, an improved boiling water reactor according to the present invention includes a plurality of internal pumps, a part of which is arranged in a reactor pressure vessel and circulates a coolant in the reactor pressure vessel. And a purge water supply source for supplying purge water to the internal pump, and each internal pump is connected to the purge water supply source via a branching section through a branch pipe, The lengths of the branch pipes to be connected are the same.
Further, another improved boiling water reactor according to the present invention, a part of which is arranged in the reactor pressure vessel, a plurality of internal pumps for circulating the coolant in the reactor pressure vessel, A purge water supply source for supplying purge water to the internal pump, a first pipe connected to the purge water supply source, and a plurality of branch portions arranged at predetermined intervals in the first pipe Each internal pump is connected to the purge water supply source via each branch pipe and the first pipe, and the flow resistance of each branch pipe is different from each other. Each of the branch pipes includes a flow path resistance member, and a support member that supports the flow path resistance member by connecting the outer peripheral surface of the flow path resistance member and the inner peripheral surface of the branch pipe. The flow resistance of each branch pipe connected to the other pipe is larger toward the upstream side. And wherein the decoction.
Further, another improved boiling water reactor according to the present invention, a part of which is arranged in the reactor pressure vessel, a plurality of internal pumps for circulating the coolant in the reactor pressure vessel, A purge water supply source for supplying purge water to the internal pump, a first pipe connected to the purge water supply source, and a plurality of branch portions arranged at predetermined intervals in the first pipe Each internal pump is connected to the purge water supply source via each branch pipe and the first pipe, and the flow resistance of each branch pipe is different from each other. The pipe diameter of the branch pipe connected to the first pipe via the branch portion is smaller in the branch pipe arranged on the upstream side .

  ADVANTAGE OF THE INVENTION According to this invention, the improved boiling water nuclear reactor which can reduce | hang the clad which flows into an internal pump and can enable the stable operation of a nuclear reactor can be provided.

  For example, in an improved boiling water reactor (ABWR), in order to prevent the coolant circulating in the reactor pressure vessel from entering each internal pump, Purge water is continuously supplied to each internal pump. If this purge water contains clad, it can be prevented from intensively flowing into a specific internal pump, improving the operability and maintainability of the internal pump and contributing to stable operation of the power plant. Become.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a schematic block diagram of an improved boiling water nuclear power plant. It is a longitudinal cross-sectional view of the internal pump shown in FIG. 1, and is an enlarged view near the lower mirror of the reactor pressure vessel. FIG. 3 is a schematic diagram of a clad flowing into the internal pump through the purge water supply piping system, showing the purge water supply piping system to the internal pump shown in FIG. 2. It is a purge water supply piping system diagram by Example 1 concerning one example of the present invention. It is a purge water supply piping system diagram by Example 2 which concerns on the other Example of this invention. It is a purge water supply piping system diagram by Example 3 which concerns on the other Example of this invention. It is the longitudinal cross-sectional view and cross-sectional view of branch piping shown in FIG.

  First, an improved boiling water reactor (ABWR) will be described. FIG. 1 shows a schematic configuration diagram of an improved boiling water nuclear power plant. As shown in FIG. 1, in the reactor building 40, a fuel exchanger 57, an operation floor (operating floor) 56 on the ceiling, a spent fuel pool 53, a dryer / separator pool 54, a nuclear reactor just below the operation floor 56. The containment vessel 50 and other safety devices (not shown) are provided. The reactor containment vessel 50 includes a reactor pressure vessel 1, a pressure suppression chamber (wet well) 51 having a pressure suppression pool 52, and a main steam pipe 48 for supplying steam generated from the reactor pressure vessel 1 to a turbine (not shown). The steam used for driving the turbine includes a water supply pipe 49 for supplying a coolant supplied from a condenser (not shown) or the like to the reactor pressure vessel 1. Here, as the coolant, for example, water, pure water, heavy water, boric acid water, or the like is used.

  Further, a cylindrical core shroud 44 is provided in the reactor pressure vessel 1, and a nuclear reactor 41 loaded with a plurality of fuel assemblies (not shown) is installed in the core shroud 44. . Further, in the reactor pressure vessel 1, a control rod guide tube 46 that allows a plurality of control rods to be inserted into the reactor 41 in order to control the nuclear reaction of the fuel assembly, and a gas disposed above the reactor 41. A steam dryer 43 is provided in the upper part of the water separator 42 and the steam separator 42. In the fuel assembly, fuel rods in which a plurality of fuel pellets (for example, MOX fuel) are filled in a stainless clad tube are arranged in a square lattice pattern in a channel box having a rectangular cross section.

  An internal pump 2 is installed in the lower mirror 47 which is the bottom of the reactor pressure vessel 1 so as to penetrate from the lower part to the inside of the reactor pressure vessel 1. A plurality of internal pumps 2 are arranged outside the outermost peripheral portion of the plurality of control rod guide pipes 46 and are annularly spaced from each other at a predetermined interval. Thereby, the internal pump 2 does not interfere with the control rod guide tube 46 and the like. The internal pump 2 supplies the coolant to the reactor 41 from the lower mirror 47 side through a downcomer 45 formed between the cylindrical core shroud 44 and the inner surface of the reactor pressure vessel 1. . The coolant flowing into the nuclear reactor 41 is heated by a nuclear reaction of a fuel assembly (not shown), becomes a gas-liquid two-phase flow, and flows into the steam-water separator 42. The gas-liquid two-phase flow flowing through the steam separator 42 is separated into moisture-containing steam (gas phase) and water (liquid phase), and the liquid phase again falls to the downcomer 45 as a coolant. On the other hand, the steam (gas phase) is introduced into the steam dryer 43 and moisture is removed, and then supplied to the turbine (not shown) via the main steam pipe 48. The coolant flowing into the reactor pressure vessel 1 from the water supply pipe 49 through the condenser or the like flows (lowers) downward in the downcomer 45. Thus, the internal pump 2 forcibly circulates the coolant to the reactor 41 in order to efficiently cool the heat generated in the reactor 41.

In the reactor building 40, a shield plug 55 is installed above the reactor containment vessel 50 that houses the reactor pressure vessel 1. A spent fuel pool 53 and a dryer / separator pool 54 are provided directly below an operation floor (operating floor) 56 with a shield plug 55 interposed therebetween. For example, when the fuel assembly loaded in the reactor 41 is replaced, the shield plug 55 is removed, and the upper cover (not shown) of the reactor pressure vessel 1 is removed, and then the spent fuel assembly is used by the fuel exchanger 57. The body is transferred from the reactor 41 to the spent fuel pool 53 filled with water. The dryer / separator pool 54 is used as a temporary storage place for in-reactor equipment such as the steam dryer 43 and the steam / water separator 42 installed in the reactor pressure vessel 1 at the time of fuel replacement or maintenance. Is done.
As shown in FIG. 1, a region RA indicated by a dotted line is present at the bottom of the reactor containment vessel 50 and in the space (dry well) below the internal pump 2. This area RA is used for installation of a device such as a control rod drive mechanism (not shown).

  Next, the structure of the internal pump 2 will be described. FIG. 2 is a longitudinal sectional view of the internal pump 2 shown in FIG. 1, and is an enlarged view of the vicinity of the lower mirror 47 of the reactor pressure vessel 1. As shown in FIG. 2, the internal pump 2 includes an impeller 3 that is a rotary blade, a diffuser 4 that is a fixed blade, a motor cover 5, an auxiliary cover 6, and a motor. A motor constituting the internal pump 2 is contained in a motor casing 7, and a stator 8, a rotor 9, and a motor cover 5 are attached to the lower part. The motor cover 5 is fastened and fixed to the motor casing 7 by stud bolts 10 and nuts 11. The rotor 9 transmits a rotational driving force to a pump shaft connected to the impeller 3. An auxiliary cover 6 is attached to the motor cover 5, and the motor casing 5 and the auxiliary cover 6 ensure the sealing performance of the motor casing 7.

  The motor is a fully closed water type, and the inside of the motor is filled with motor cooling water. The motor casing 7 is provided with a motor cooling water inlet 12 and a motor cooling water outlet 13. The heat exchanger 15 is connected to the motor cooling water inlet 12 and the motor cooling water outlet 13 by a motor cooling water circulation pipe 16. Has been. Here, for example, water or pure water is used as the motor cooling water. During operation of the reactor 41, the internal pump 2 is always operated, and as shown by the white arrow in FIG. 2, the coolant in the reactor pressure vessel 1 is sucked from above the impeller 3 and passed through the diffuser 4. And flow along the lower mirror 47. As a result, the coolant is forcibly circulated in the reactor pressure vessel 1 as described above. As described above, during operation of the nuclear reactor 41, the motor that transmits the rotational driving force to the impeller 3 that constitutes the internal pump 2 that is always operated generates heat through the pump shaft. By driving the heat exchanger 15 in synchronization with the driving of the motor, the motor cooling water circulation pipe 16 is used to drive the motor cooling water inlet 12, the motor inside, and the motor cooling water outlet as shown by arrows in FIG. The inside of the motor is cooled by circulating the motor cooling water.

  In addition, a purge water nozzle 14 is provided on the upper portion of the motor casing 7. The purge water flowing into the motor casing 7 through the purge water nozzle 14 flows through the gap between the pump shaft and the inner peripheral surface of the motor casing 7 to the diffuser 4 side. Thereafter, the purge water flows out into the reactor pressure vessel 1 near the lower portion of the diffuser 4. Thus, the reactor water can be prevented from entering the motor casing 7. When the internal pump 2 is in operation, the purge water is always supplied from the purge water nozzle 14 continuously.

A configuration for supplying purge water to a plurality of internal pumps will be described. FIG. 3 shows a purge water supply piping system to the internal pump shown in FIG. 2, and is a schematic diagram of the clad flowing into the internal pump through the purge water supply piping system. FIG. 3 shows a case where purge water is supplied to six internal pumps 21 to 26 as an example. The purge water supply piping system includes a purge water supply source 17 for storing the purge water 18, a purge water supply pump 19, a purge water supply pipe (main pipe) MP ₁ connected at one end to the purge water supply pump 19, a purge water supply a plurality of branch portions 6 provided on the pipe MP _1, and composed of the branch pipe _BP 1 to BP ₆ for connecting the respective branch portions 6 and internal pumps 21-26, respectively. The branch parts 1-6 are comprised by T type piping, for example.

The branch pipe BP ₁ connecting the purge water supply pipe MP ₁ and the internal pump 21 via the branch part 1 is connected to the branch parts 2 to 6 provided in the other pipe branched at the branch part 1. For the branched pipes BP _{2 to} BP ₆ , the purge water supply pipe MP ₁ is apparently equivalent to the state connected to the internal pump 21. Thus, the purge water supply pump 19, the flow rate of the purge water flowing through the purge water supply pipe MP ₁ (the flow rate in the upstream) Q, when the number of the internal pump is N, the purge water in the branch pipe BP ₁ The flow rate is Q / N, sequentially located on the downstream side, the flow rate of purge water after passing through branch 1 is (N-1) Q / N, the flow rate of purge water after passing through branch 2 is (N-2) Q / N, the flow rate of purge water after passing through branch part 3 is (N-3) Q / N, and the flow rate of purge water after passing through branch part 4 is (N-4) Q / N, after passing through branch part 5 The flow rate of the purge water is (N-5) Q / N, and the flow rate of the purge water after passing through the branch part 6 is (N-6) Q / N. That is, the flow rate of the purge water flowing through the branch pipe decreases as the downstream pipe is branched. Accordingly, the amount of purge water flowing into the branch pipe arranged on the downstream side is reduced. On the other hand, the purge water flowing through the pipe may contain a clad. Here, the clad is a metal oxide that is dispersed in the coolant without being dissolved in water, among the corrosion products generated by the corrosion of the piping metal material. As shown in FIG. 3, in the purge water supply piping system, the flow rate of the incoming purge water is higher, the amount of clad involved is larger, and the amount of incoming purge water is larger as the branch pipe is arranged upstream. Therefore, in proportion to this, the amount of clad flowing into the internal pump through the branch pipe also increases. In FIG. 3, the difference in the amount of clad flowing through each branch pipe and flowing into each internal pump is indicated by the size and number of clads. However, the size of the clad described here is expressed only as an alternative indicating the amount of clad, and the size itself is not important.

  As shown in FIG. 3, the clad flowing into the internal pump through each branch pipe flows through the gap between the pump shaft and the inner peripheral surface of the motor casing 7 together with the purge water as described above. Therefore, the clad adheres to or accumulates on the outer peripheral surface of the pump shaft and / or the inner peripheral surface of the motor casing 7. In order to manage the operation / maintenance of the pump, it is desirable to suppress the adhering or depositing cladding as much as possible. In order to remove the clad adhered or deposited on the pump, it is necessary to temporarily stop the operation of the nuclear reactor 41 and remove the clad adhered or deposited on the internal pump.

  Further, if the amount of clad flowing into a specific internal pump, that is, the internal pump connected to the upstream branch pipe, increases, the operation of this specific internal pump may be adversely affected. Therefore, in order to stably operate the power plant, it is important to equalize the amount of clad flowing into each internal pump connected via each branch pipe. If the clad inflow amount is made uniform, the frequency of stopping the operation of the reactor 41 can be greatly reduced.

  Hereinafter, embodiments of the present invention that make the amount of clad flowing into each internal pump uniform can be described in detail with reference to the drawings.

FIG. 4 shows a purge water supply piping system diagram according to the first embodiment of the present invention. As shown in FIG. 4, the purge water supply piping system of the present embodiment has a branch _{1 at} the other end of the purge water supply pipe MP ₁ , which is the most upstream pipe, connected at one end to the purge water supply pump 19. A branching section 2 is provided at each downstream end of the branch pipes BP ₁₁ and BP _{12 that} are provided and branch left and right from the branch section 1. Here, pipe length and the pipe diameter of the branch pipe _{BP 11} and _{BP 12} are equal. Branch pipes BP ₂₁ and BP ₂₂ branching left and right from one branch part 2 and branch pipes BP ₂₃ and BP ₂₄ branching left and right from the other branch part 2 are respectively provided at branch ends 3. All pipe length and the pipe diameter of the branch pipe _BP 21 _{to BP 24} are equal. Further, among the branch pipes branching left and right from the respective branch parts 3 which are the third stage branch parts, the branch pipe BP ₃₁ is connected to the purge water nozzle 14 of the internal pump 21, and the branch pipe BP ₃₂ is connected to the internal pipe 21. Connected to the purge water nozzle 14 of the null pump 22. The branch pipe BP ₃₃ is connected to the purge water nozzle 14 of the internal pump 23, and the branch pipe BP ₃₄ is connected to the purge water nozzle 14 of the internal pump 24. Similarly, the branch pipe BP ₃₅ is connected to the purge water nozzle 14 of the internal pump 25, and the branch pipe BP ₃₆ is connected to the purge water nozzle 14 of the internal pump 26. The pipe lengths and pipe diameters of the branch pipes BP _{31 to} BP ₃₆ are all the same.

As described above, the branching part 1 to the branching part 3 are provided with a purge water supply piping system that branches in a three-stage hierarchical structure, and the branching pipes in each stage have the same pipe length and pipe diameter. Thereby, for example, the piping length from the branching portion 1 to the purge water nozzle 14 of the internal pump 21 and the piping length from the branching portion 1 to the purge water nozzle 14 of the internal pump 26 have the following relationship.
_{BP 11 + BP 21 + BP 31} = BP 12 + BP 23 + BP 36
These relationships are the same in the other internal pumps 22 to 25, and the pipe lengths connecting the internal pumps 21 to 26 and the purge water supply source 17 are the same. As a result, the flow resistance in each flow path (pipe connected to each internal pump) becomes the same, the flow rate or flow rate of purge water becomes substantially the same in each pipe, and flows into each internal pump 21-26. The clad amount to be made uniform. Therefore, it is possible to prevent the clad from intensively flowing into the specific internal pump, and it is possible to suppress the adverse effect on the operation of the specific internal pump as described above.

Note that the number of branch portions having a hierarchical structure is appropriately set according to the number of internal pumps installed in the reactor pressure vessel 1. Also, if the number of installed internal pumps is an odd number (N), the internal pump is virtually regarded as (N + 1) units, and the branch portion having a hierarchical structure as described above is used. For example, the number of stages is set to M. Then, the N + 1-th branch pipe _{BPMN + 1} on the most downstream side (branching from the branch part at the final stage) returns to the purge water supply source 17 via a three-way valve or the like without being connected to the internal pump. By connecting to the piping, the same effect can be achieved.

  According to the present embodiment, the amount of clad flowing into each internal pump connected via each branch pipe can be made uniform. As a result, since the cladding adhering to or depositing on the internal pump is removed, the frequency at which the operation of the nuclear reactor is stopped can be greatly reduced.

  In addition, since the frequency of reactor shutdowns can be reduced, the operability and maintainability of the internal pump can be improved, which can contribute to safe operation of the power plant.

FIG. 5 shows a purge water supply piping system diagram according to Embodiment 2 of another embodiment of the present invention. In the first embodiment, the branch portion has a multi-stage hierarchical structure, whereas in this embodiment, one branch pipe BP ₁ branched from the branch portion 1 to which one end of the purge water supply pipe MP ₁ is connected, One purge water supply pipe MP ₂ (first pipe) extending from the branch part 1 to the opposite side of the branch pipe BP ₁ is provided, and the purge water supply pipe MP ₂ is directed to the downstream side at a predetermined interval. A difference is that a plurality of branch portions that are spaced apart from each other are provided, and an internal pump is connected to a branch pipe whose one end is connected to each branch portion provided on the downstream side.

As shown in FIG. 5, the purge water supply piping system according to this embodiment, one end is connected to the purge water supply pump 19, a branch unit 1 to the other end of the purge water supply pipe MP ₁ is the most upstream pipe And a branch pipe BP ₁ branched from the branch section 1 and a purge water supply pipe MP ₂ (first pipe) branched from the branch section 1 and extending to the opposite side with respect to the branch pipe BP ₁ . The purge water supply pipe MP ₂ (first pipe) is provided with a plurality of branch portions 2 to 6 spaced apart from each other at a predetermined interval, and a branch pipe BP ₂ having one end connected to the branch portion ₂ . branch pipe BP 3 having one end connected to the branch unit _3, the branch pipe BP 4 to be branched from the branch portion 4 is connected to the purge water nozzle 14 of the internal pump _21, branched from the branching unit 5 was purged of internal pump 22 branch pipe BP 5 is connected to the water nozzle _14, and has a branch pipe BP ₆ which is connected to the purge water nozzle 14 of the internal pump 23 is branched from the branching unit 6. As described with reference to FIG. 3, the flow rate of the purge water flowing through the branch pipe BP ₁ is the highest, followed by the purge water after passing through the branch portion 1, the purge water after passing through the branch portion 2, and the branch portion 3. The purge water after passing, the purge water after passing through the branching section 4, the purge water after passing through the branching section 5, and the purge water after passing through the branching section 6 are sequentially arranged downstream of the purge water supply pipe MP ₂ (first pipe). As it goes, the flow rate of purge water decreases. Here, the branch pipes BP _{1 to} BP ₆ have the same pipe length and pipe diameter. Each branch pipe BP _{1 to} BP ₆ is provided with a flow rate regulator (not shown) and adjusted so that the flow rate of the barge water flowing in each branch pipe BP _{1 to} BP ₆ is the same.

The higher the flow rate of the purge water that flows, the greater the amount of clad that is entrained. Therefore, the upstream branch pipes BP ₁ , BP ₂ , and BP ₃ are provided with three-way valves 31, 32, and 33, respectively. . The three-way valve 31 is configured to be connectable to the branch pipe BP ₁ and the return pipe RP ₁ having one end connected to the purge water supply source 17. The three-way valve 32 is configured to be able to connect the branch pipe BP ₂ and the return pipe RP ₂ having one end connected to the purge water supply source 17. Similarly, the three-way valve 33 is configured to be able to connect the branch pipe BP ₃ and the return pipe RP ₃ having one end connected to the purge water supply source 17. The three-way valves 31 to 33 are connected to the branch pipe BP ₁ and the return pipe RP ₁ , the branch pipe BP ₂ and the return pipe RP ₂ , and the branch pipe BP ₃ and the return pipe RP ₃ , respectively. By setting, the purge water containing a large amount of the clad can be returned to the purge water supply source 17 and prevented from flowing into the internal pump.

In addition, the amount of clad flowing into the branch pipes BP ₄ , BP ₅ , and BP ₆ connected to the branch parts 4 to 6 on the downstream side of the purge water supply pipe MP ₂ (first pipe) cannot be made uniform. The clad flowing into the internal pumps 21 to 23 can be reduced.

In this embodiment, the installation was purged water three-way valve, a branch pipe to return to the purge water storage tank 17 via a return pipe, but the three branch pipes BP ₁ to BP ₃ upstream, in which Without limitation, it may be set as appropriate according to the number of internal pumps installed in the reactor pressure vessel 1, and in this case, the flow rate and / or flow rate of purge water flowing in each branch pipe is measured in advance, It is desirable to determine in which branch pipe the three-way valve is installed. Alternatively, based on the length of each branch pipe and the length of the purge water supply pipe MP ₂ (first pipe) between the branch part to which the branch pipe is connected and the branch part 1, the branch where the three-way valve should be installed Piping may be determined.
Further, instead of a configuration in which purge water containing a large amount of cladding flowing through the return pipe RP ₁ , return pipe RP ₂ , and return pipe RP ₃ is returned to the purge water supply source 17, a drainage tank or the like is newly provided and returned. It is desirable to have a configuration.

  According to the present embodiment, compared to the first embodiment, the piping can be simplified and the cladding flowing into the internal pump can be reduced.

FIG. 6 shows a purge water supply piping system diagram according to Embodiment 3 of another embodiment of the present invention. One branch pipe BP ₁ branched from the branch part 1 to which one end of the purge water supply pipe MP ₁ is connected, and one purge water supply pipe MP ₂ extending from the branch part ₁ to the opposite side of the branch pipe BP _1. (first pipe) with a purge water supply pipe MP _2, are the same as in example 2 point of providing a plurality of branch portions is disposed spaced at a predetermined distance toward to the downstream side. In Example 2, it was set as the structure which has the flow volume regulator which adjusts so that the flow volume of the purge water which flows through each branch piping may become the same. On the other hand, in the present embodiment, such a flow rate regulator is not required, and each branch part and each internal pump are connected, and each branch pipe has a different flow path resistance. This is different from the second embodiment.

As shown in FIG. 6, the purge water supply piping system according to this embodiment, one end is connected to the purge water supply pump 19, a branch unit 1 to the other end of the purge water supply pipe MP ₁ is the most upstream pipe And a branch pipe BP ₁ branched from the branch part 1 and a purge water supply pipe MP ₂ (first pipe) branched from the branch part 1 and extending to the opposite side with respect to the branch pipe BP ₁ . The purge water supply pipe MP ₂ (first pipe) is provided with a plurality of branch portions 2 to 6 spaced apart from each other at a predetermined interval, and a branch pipe BP ₂ having one end connected to the branch portion ₂ . branch pipe BP 3 having one end connected to the branch unit _3, the branch pipe BP 4 having one end connected to the branch portion _4, the branch pipe BP 5 one bifurcation 5 is _connected, and, one end to the branching section 6 A branch pipe BP ₆ to be connected is provided. The branch pipe BP ₁ is connected to the purge water nozzle 14 of the internal pump 21, the branch pipe BP ₂ is connected to the purge water nozzle 14 of the internal pump 22, and the branch pipe BP ₃ is connected to the purge water nozzle 14 of the internal pump 23. The branch pipe BP ₄ is connected to the purge water nozzle 14 of the internal pump 24, the branch pipe BP ₅ is connected to the purge water nozzle 14 of the internal pump 25, and the branch pipe BP ₆ is connected to the purge water nozzle 14 of the internal pump 26. Each is connected. Here, the branch pipes BP _{1 to} BP ₆ and the purge water supply pipe MP ₂ (first pipe) have the same pipe diameter, and the branch pipes BP _{2 to} BP ₆ branching from the branch parts have the same pipe length. is there.

In general, the flow resistance acting on the fluid flowing through the pipe is inversely proportional to the pipe diameter and proportional to the pipe length. Further, as described with reference to FIG. 3, the flow rate of the purge water flowing through the branch pipe BP ₁ is the highest, followed by the purge water after passing through the branch part 1, the purge water after passing through the branch part 2, and the branch Purge water supply pipe MP ₂ (first pipe) in order of purge water after passing through section 3, purge water after passing through branch section 4, purge water after passing through branch section 5, and purge water after passing through branch section 6 The flow rate of the purge water after passing through each branch portion decreases as it goes downstream. Considering these, in the present embodiment, the flow rate regulators required in the second embodiment are made unnecessary by configuring the branch pipes BP _{1 to} BP ₆ to have different flow path resistances.

FIG. 7 shows a longitudinal sectional view of the branch pipe shown in FIG. 6 and an AA sectional arrow view in the longitudinal sectional view. In FIG. 7, as an example, a branch pipe BP ₂ branched from the branch portion 2 shown in FIG. 6 and connected to the purge water nozzle 14 of the internal pump 22 is shown. As shown in the left diagram of FIG. 7, the branch pipe BP ₂ includes a flow path resistance member 34 having a substantially vertical cross section and a support member 35 that supports the flow path resistance member 34. As shown in the right view of FIG. 7 (the cross-sectional view taken along the line AA in the left view), the flow path resistance member 34 has a substantially circular cross section. Further, support members 35 having both ends connected to the outer peripheral surface of the flow path resistance member 34 and the inner peripheral surface of the branch pipe BP ₂ are arranged at four locations. Accordingly, flow resistance member 34 is fixed to the substantially central portion of the branch pipe BP _2. Note that, as shown in the left diagram of FIG. 7, the cross-sectional area of the flow path resistance member 34 in the AA cross-sectional arrow view is maximized (hereinafter simply referred to as a cross-sectional area). As shown in the right view of FIG. 7, the two support members 35 adjacent to each other in the circumferential direction of the flow path resistance member 34 are arranged so as to be orthogonal to each other in the cross section. FIG. 7 shows an example in which the support members 35 are arranged at four locations. However, the present invention is not limited to this. For example, the support members 35 are arranged at three locations, and the flow resistance of the three support members 35 is determined. The two support members 35 adjacent to each other in the circumferential direction of the member 34 may be arranged so as to form an angle of approximately 180 ° in the cross section. Moreover, it is good also as a structure which arrange | positions the desired number of support members 35 suitably, such as two. Further, the longitudinal cross-sectional shape of the flow path resistance member 34 is not limited to the streamline shape, and may be set as appropriate.

Shown in the right diagram of FIG. 7, the cross-sectional area of the flow resistance member 34, the flow path resistance is defined which acts on the purge water flowing through the branch pipe BP _2. Although the support member 35 itself also acts as a flow path resistance, the area thereof is smaller than the cross-sectional area (S) of the flow path resistance member 34. Therefore, for the sake of easy understanding, the description will be ignored below. Of course, the flow path resistance of each branch pipe may be set in consideration of the sum of the cross-sectional areas of the plurality of support members 35.

In FIG. 7, the branch pipe BP ₂ is shown, but the other branch pipes BP ₁ and BP _{3 to} BP ₆ are similarly provided with a flow path resistance member 34 and a support member 35 in the branch pipe, and the flow path resistance member. 34 cross-sectional areas (S) are different between the branch pipes.

The flow rate (v) of the purge water flowing through the branch pipes BP _{1 to} BP ₆ has the following relationship.

Flow rate of purge water v: BP ₁ > BP ₂ > BP ₃ > BP ₄ > BP ₅ > BP ₆
Each flow path member 34 is formed so that the cross-sectional area (S) of the flow path resistance members disposed in the branch pipes BP _{1 to} BP ₆ has the following relationship, and each flow path member 34 is disposed in the corresponding branch pipe.

Cross-sectional area S of the flow path resistance member 34: BP ₁ > BP ₂ > BP ₃ > BP ₄ > BP ₅ > BP ₆
Here, the setting of the cross-sectional area of the flow path resistance member 34 arranged in each branch pipe is branched from the branch portion 1 and connected to the purge water nozzle 14 of the internal pump 21 in the case of the branch pipe BP _1. The pipe length of the pipe BP ₁ , and in the case of the branch pipe BP ₂ , the pipe length of the purge water supply pipe MP ₂ (first pipe) from the branch part 1 to the branch part 2 and the branch part 2 are branched. It is set based on the pipe length of the branch pipe BP ₂ connected to the purge water nozzle 14 of the internal pump 22. Similarly, in the case of the branch pipe BP ₃ , the purge length of the purge water supply pipe MP ₂ (first pipe) from the branch section 1 to the branch section 3 and the purge of the internal pump 23 branched from the branch section 3. It is set based on the pipe length of the branch pipe BP ₃ connected to the water nozzle 14. Thus, in this embodiment, the branch pipes BP _{1 to} BP are set so that the flow path resistances in the flow paths connected to the internal pumps via the branch pipes are the same, starting from the branch section 1. ₆ is set to the cross-sectional area (S) of the flow path resistance member 34 disposed in the position ₆ .

According to the present embodiment, in the respective flow paths connected to the internal pumps 21 to 26 from the purge water supply source 17 via the branch portions 1 to 6 and the branch pipes BP _{1 to} BP ₆ , The resistance becomes the same, and the amount of clad flowing into each internal pump can be made uniform.

  Further, according to the present embodiment, although it is necessary to arrange the flow path resistance member 34 and the support member 35 in each branch pipe, the piping can be further simplified as compared with the second embodiment. It becomes.

In this embodiment, by changing the cross-sectional area of the flow path resistance member 34 disposed in each branch pipe BP _{1 to} BP ₆ , the flow path resistance in each branch pipe is configured to be different from each other, thereby purging. It was set as the structure from which the flow path resistance in each flow path from the water storage tank 17 to each internal pump 21-26 becomes the same. Instead of this, the following effects can be obtained even with the following configuration.

Each branch pipe is formed such that the pipe diameter D of each branch pipe BP _{1 to} BP ₆ has the following relationship.

Pipe diameter D of branch pipe: BP ₁ <BP ₂ <BP ₃ <BP ₄ <BP ₅ <BP ₆
Here, setting the pipe diameter of the branch pipe (D) is branched in the case of pipe BP ₁ is pipe branch pipe BP ₁ to be connected to the purge water nozzle 14 of the internal pump 21 is branched from the branching unit 1 In the case of the branch pipe BP ₂ , the length of the purge water supply pipe MP ₂ (first pipe) from the branch section 1 to the branch section 2 and the internal pump 22 branch from the branch section 2. Is set based on the pipe length of the branch pipe BP ₂ connected to the purge water nozzle 14. Similarly, in the case of the branch pipe BP ₃ , the purge length of the purge water supply pipe MP ₂ (first pipe) from the branch section 1 to the branch section 3 and the purge of the internal pump 23 branched from the branch section 3. It is set based on the pipe length of the branch pipe BP ₃ connected to the water nozzle 14. That is, the pipe length and / or the correspondence of the branch pipe so that the flow path resistance is the same in each flow path connected to each internal pump from the purge water supply source 17 via each branch section 1-6. The pipe diameter D of each branch pipe is set based on the pipe length of the purge water supply pipe MP ₂ (first pipe) to the branching section.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace the configurations of other embodiments with respect to a part of the configurations of the embodiments.

4 ... Diffuser 51 ... Reactor pressure vessel 2 ... Internal pump 3 ... Impeller ... Motor cover 6 ... Auxiliary cover 7 ... Motor casing 8 ... Stator 9 ... Rotor 10 ... Stud bolt 11 ... Nut 12 ... Motor cooling water inlet 13 ... Motor cooling water outlet 14 ... Purge water nozzle 15 ... Heat exchanger 16 ... Motor Cooling water circulation pipe 17 ... Purge water supply source 18 ... Purge water 19 ... Purge water supply pumps 21-26 ... Internal pumps 31-33 ... Three-way valve 34 ... Flow path resistance member 35 ... support member 40 ... reactor building 41 ... reactor 42 ... steam separator 43 ... steam dryer 44 ... core shroud 45 ... downcomer 46 ... control Bar guide tube 47 ... lower mirror 48 · Main steam pipe 49 ... feed water pipe 50 ... reactor containment vessel 51 ... pressure suppression chamber (wet well)
52 ... Pressure suppression pool 53 ... Spent fuel pool 54 ... Dryer / separator pool 55 ... Shield plug 56 ... Operation floor (operating floor)
57 ... Fuel changer

Claims (9)

A plurality of internal pumps, a part of which is arranged in the reactor pressure vessel and circulating the coolant in the reactor pressure vessel;
A purge water supply source for supplying purge water to the internal pump,
Each of the internal pumps is connected to the purge water supply source by a branch pipe through a branch portion, and the length of the branch pipe connected to each internal pump is the same. Type reactor. The improved boiling water reactor according to claim 1,
Between each internal pump and the purge water supply source, having a plurality of branch portions arranged in multiple stages,
An improved boiling water reactor characterized in that the lengths of the first branch pipe and the second branch pipe branching in two directions from the branch portion arranged in each stage are the same. The improved boiling water reactor according to claim 2,
Of the branch portions arranged in multiple stages, the ends of the branch pipes branching in two directions from the branch portions arranged in the final stage are connected to the purge water nozzles of the internal pumps,
Improved boiling water, characterized in that the length of the pipe from the branch section arranged in the first stage to the purge water nozzle of each internal pump through the branch section arranged in the last stage and the branch pipe is the same Type reactor. In the improved boiling water reactor according to claim 3,
The number of stages of the plurality of branch portions arranged in multiple stages is set in accordance with the number of the internal pumps. In the improved boiling water reactor according to claim 4,
The internal pump includes at least an impeller that rotates as the pump shaft rotates, a diffuser that is a fixed blade, a motor that transmits rotational driving force to the pump shaft, and a motor casing that houses the motor in a watertight manner. ,
The purge water nozzle is an upper part of the motor casing and is provided outside the reactor pressure vessel,
The purge water flowing in from the purge water nozzle flows through the gap between the pump shaft and the motor casing to the diffuser side, and flows out into the reactor pressure vessel near the lower portion of the diffuser. Boiling water reactor. A plurality of internal pumps, a part of which is arranged in the reactor pressure vessel and circulating the coolant in the reactor pressure vessel;
A purge water supply source for supplying purge water to the internal pump;
A first pipe connected to the purge water supply source;
A branch pipe connected to a plurality of branch portions arranged at a predetermined interval in the first pipe, and
Each internal pump is connected to the purge water supply source via each branch pipe and the first pipe, and the flow resistance of each branch pipe is different from each other.
Each of the branch pipes includes a flow path resistance member, a support member that supports the flow path resistance member by connecting an outer peripheral surface of the flow path resistance member and an inner peripheral surface of the branch pipe,
An improved boiling water reactor characterized in that the flow resistance of each branch pipe connected to the first pipe is larger toward the upstream side . A plurality of internal pumps, a part of which is arranged in the reactor pressure vessel and circulating the coolant in the reactor pressure vessel;
A purge water supply source for supplying purge water to the internal pump;
A first pipe connected to the purge water supply source;
A branch pipe connected to a plurality of branch portions arranged at a predetermined interval in the first pipe, and
Each internal pump is connected to the purge water supply source via each branch pipe and the first pipe, and the flow resistance of each branch pipe is different from each other.
An improved boiling water reactor characterized in that a branch pipe connected to the first pipe via a branch portion has a smaller pipe diameter as the branch pipe arranged on the upstream side . The improved boiling water reactor according to claim 6 ,
The improved boiling water nuclear reactor, wherein the maximum cross-sectional area of the flow path resistance member provided in each branch pipe connected to the first pipe is larger toward the upstream side . The improved boiling water reactor according to claim 8,
Each branch pipe is connected to a purge water nozzle of each internal pump,
The internal pump includes at least an impeller that rotates as the pump shaft rotates, a diffuser that is a fixed blade, a motor that transmits rotational driving force to the pump shaft, and a motor casing that houses the motor in a watertight manner. ,
The purge water nozzle is an upper part of the motor casing and is provided outside the reactor pressure vessel,
The purge water flowing in from the purge water nozzle flows through the gap between the pump shaft and the motor casing to the diffuser side, and flows out into the reactor pressure vessel near the lower portion of the diffuser. Boiling water reactor.

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