JP2010169545A - Jet pump and nuclear reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a jet pump capable of shortening a time required for remodeling, and improving efficiency. <P>SOLUTION: This jet pump 10 includes a nozzle 11, a bell mouth 12, a throat 13 including an upper throat 13A and a lower throat 13B, and a diffuser 17. The upper throat 13A is bonded to the lower end of the bell mouth 12. In the lower throat 13B, a fitting part 28 is formed on the upper end, and a channel enlargement part 14 and a tapered part 15 are provided on the lower end. The tapered part 15 is connected to the lower end of the channel enlargement part 14, and a channel area is reduced gradually toward the lower end. In the diffuser 17, a fitting part 18 is formed on the upper end. The tapered part 15 is fitted into the fitting part 18 of the diffuser 17. The upper end of the fitting part 18 has a contact with the whole periphery of the tapered part 15, and the lower throat 13B and the diffuser 17 are sealed. A slip joint 16 is provided on the throat 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a jet pump and a nuclear reactor, and more particularly, to a jet pump and a nuclear reactor suitable for application to a boiling water reactor.

  In a boiling water reactor, a core loaded with a plurality of fuel assemblies is provided in a reactor pressure vessel. A core shroud disposed in a reactor pressure vessel (hereinafter referred to as RPV) surrounds the core. Cooling water for cooling the fuel rods in each fuel assembly is supplied to the core by a plurality of jet pumps arranged in a downcomer that is an annular space between the reactor pressure vessel and the core shroud.

  A jet pump used in a boiling water reactor includes a nozzle, a bell mouth, a throat, and a diffuser. The cooling water in the RPV boosted by the driving of the recirculation pump passes through the recirculation system piping and is jetted from the nozzle into the throat as driving water. The nozzle increases the speed of the driving water. The cooling water present around the nozzle in the downcomer is sucked into the bell mouth as driven water by the action of the jetted driving water, and flows into the diffuser through the throat. The cooling water discharged from the diffuser is supplied to the core through the lower plenum in the RPV.

  A slip joint having a gap is provided between the throat and the diffuser, and the slip joint absorbs a difference in thermal expansion between the riser pipe and the diffuser. Since the pressure in the slip joint is higher than the pressure in the downcomer, the cooling water flowing into the upper end portion of the diffuser leaks to the downcomer through between the throat and the diffuser. This leakage of cooling water reduces the M ratio (the ratio of the driven water flow rate to the driving water flow rate) and the efficiency (the product of the M ratio and the N ratio (the total head ratio of the driven water to the driving water)) of the jet pump. . Also, excessive leakage flow can cause vibrations in the slip joint, which is a source of harmful excitation for the jet pump.

  In order to reduce the amount of cooling water leaking from the slip joint of the jet pump, it is known that a labyrinth seal structure is formed on the outer surface of the lower end portion of the throat in the slip joint (for example, JP-A-56-27100). See the official gazette). In addition, it has also been proposed to form a slip joint in a throat whose internal pressure is lower than that of the outside in a jet pump (Japanese Patent Laid-Open No. 58-15798).

JP-A-56-27100 Japanese Patent Laid-Open No. 58-15798

  In the jet pump applied to the boiling water reactor, the throat of the slip joint is only inserted into the upper end of the diffuser. For this reason, the throat can be easily taken out from the diffuser after releasing the combined state of the nozzle portion and the riser pipe. For this reason, in an existing jet pump in a boiling water reactor, a labyrinth seal structure is formed on the outer surface of the lower end portion of the throat, and the throat having the labyrinth seal structure can be easily attached to the diffuser. However, even with the labyrinth seal structure, the gap between the throat and the diffuser cannot be eliminated, so that the leakage of cooling water from the gap occurs with a small amount.

  As disclosed in Japanese Patent Laid-Open No. 58-15798, the throat is divided into an upper throat and a lower throat, a slip joint is formed by the upper throat and the lower throat, and the lower end of the lower throat is welded to the upper end of the diffuser. It is possible to prevent leakage of the cooling water from the slip joint where negative pressure becomes negative. For this reason, the efficiency of the jet pump is improved.

  However, when the structure described in Japanese Patent Application Laid-Open No. 58-15798 is applied to an existing boiling water reactor jet pump, in the downcomer, which is a narrow annular space between the RPV and the core shroud, It is necessary to perform welding between the lower end of the lower throat and the upper end of the diffuser by remote control. For this reason, it takes a long time to modify the existing jet pump.

  An object of the present invention is to provide a jet pump and a nuclear reactor that can shorten the time required for remodeling and can improve efficiency.

A feature of the present invention that achieves the above-described object is that a nozzle for ejecting a driving fluid, a throat including a first throat and a second throat into which the driving fluid and a driven fluid sucked by the ejection of the driving fluid flow, A diffuser having a second end on the upstream side in which the first end on the downstream side of the two throats is detachably contacted,
The contact portion between the first end of the second throat and the second end of the diffuser is sealed, and a slip joint is formed by the third end on the downstream side of the first throat and the fourth end on the upstream side of the second throat. Is in the configuration.

  The contact portion between the first end of the second throat and the second end of the diffuser is sealed, and the slip joint is formed by the third end on the downstream side of the first throat and the fourth end on the upstream side of the second throat. Since it is comprised, it can prevent that an internal fluid leaks outside from between the contact parts of the 1st end part and the 2nd end part of a diffuser, and a slip joint. In particular, since the pressure in the third end portion of the first throat and the fourth end portion of the second throat is lower than that around the jet pump, the internal fluid can be prevented from leaking outside through the slip joint.

  Furthermore, since it is not necessary to weld the first end portion of the second throat and the second end portion of the diffuser, the time required for remodeling the existing jet pump can be shortened.

  According to the present invention, the time required for remodeling can be shortened, and the efficiency of the jet pump can be improved.

It is a block diagram of the jet pump of Example 1 applied to the boiling water nuclear reactor which is one suitable Example of this invention. It is an enlarged view of the II section of FIG. It is a longitudinal cross-sectional view of the boiling water reactor to which the jet pump shown in FIG. 1 is applied. It is a longitudinal cross-sectional view of the coupling | bond part of the lower throat and diffuser of the jet pump of Example 2 applied to the boiling water reactor which is another Example of this invention. It is a perspective view of the joint part of the lower throat and diffuser of the jet pump of Example 3 applied to the boiling water reactor which is another Example of this invention. It is a perspective view of the lower end part of the lower throat shown in FIG. It is a perspective view of the clamp shown in FIG. It is a longitudinal cross-sectional view of the coupling | bond part of the lower throat and diffuser shown in FIG. It is a perspective view of the upper end part of the diffuser shown in FIG. It is explanatory drawing which shows the state which suspended the clamp from the lower throat shown in FIG. It is explanatory drawing which shows the state which rotated 90 degrees the clamp hung by the lower throat shown in FIG. 5 from the state shown in FIG. It is explanatory drawing which shows the state which couple | bonds a lower throat and a diffuser with the clamp different from the clamp shown in FIG.

  Examples of the present invention will be described below.

  A jet pump according to a first embodiment which is a preferred embodiment of the present invention will be described below with reference to FIGS. Before describing the structure of the jet pump of the present embodiment, the schematic structure of a boiling water reactor to which the jet pump is applied will be described below with reference to FIGS.

  A boiling water reactor (BWR) has a reactor pressure vessel (reactor vessel) 1, and a reactor core shroud 3 is installed in the reactor pressure vessel 1. The reactor pressure vessel is hereinafter referred to as RPV. A core 2 loaded with a plurality of fuel assemblies (not shown) is disposed in a core shroud 3. A steam separator 4 and a steam dryer 5 are disposed above the core 2 in the RPV 1. A jet pump 10 is disposed in an annular downcomer 6 formed between the RPV 1 and the core shroud 3, and is installed on a shroud support 9. The recirculation system provided in the RPV 1 includes a recirculation system pipe 7 and a recirculation pump 8 installed in the recirculation system pipe 7. One end of the recirculation system pipe 7 is attached to the RPV 1 and communicated with the downcomer 6. The other end of the recirculation pipe 7 is connected to a lower end of a riser pipe 9 disposed in the downcomer 6. The riser pipe 9 is attached to a riser brace 23 installed on the inner surface of the RPV 1. The upper end of the riser pipe 9 is connected to an elbow (bent pipe) 20, and the elbow 20 is connected to the nozzle 11 of the jet pump 10. A main steam pipe 25 and a water supply pipe 26 are connected to the RPV 1. The nozzle 11 is attached to the bell mouth 12 by a plurality of ribs 22 and is integrated with the bell mouth 12.

  During the operation of the boiling water reactor, the cooling water (driven fluid, coolant), which is the driven water existing in the upper part of the RPV 1, is mixed with the feed water supplied to the RPV 1 from the feed water pipe 26 and is mixed in the downcomer 6. Descend. The cooling water is sucked into the recirculation system pipe 7 by the recirculation pump 8 that is being driven, and the pressure is raised by the recirculation pump 8. This boosted cooling water is referred to as driving water (driving fluid) for convenience. The driving water flows through the recirculation system pipe 7, the riser pipe 9, and the elbow 20, reaches the nozzle 11 of the jet pump 10, and is ejected from the nozzle 11. Driven water that is cooling water present in the downcomer 6 around the nozzle 11 is sucked into the throat 13 from the bell mouth 12 by the ejection of the drive water. This driven water descends in the throat 13 together with the driving water and is discharged from the lower end of the diffuser 17. Cooling water (including driven water and driving water) discharged from the diffuser 17 is supplied to the core 2 through the lower plenum 27. The cooling water is heated when passing through the core 2 and becomes a gas-liquid two-phase flow containing water and steam. The steam / water separator 4 separates the gas / liquid two-phase flow into steam and water. The separated steam is further dehumidified by the steam dryer 5 and discharged to the main steam pipe 25. This steam is guided to a steam turbine (not shown) to rotate the steam turbine. A generator connected to the steam turbine rotates to generate electric power. The steam discharged from the steam turbine is condensed into water by a condenser (not shown). This condensed water is supplied into the RPV 1 through the water supply pipe 26 as water supply. The water separated by the steam separator 4 and the steam dryer 5 falls and reaches the downcomer 6 as cooling water.

  The jet pump 10 of this embodiment includes a nozzle 11, a bell mouth 12, a throat 13 including an upper throat 13A and a lower throat 13B, and a diffuser 17. The nozzle 12 is disposed above the bell mouth 12 and is attached to the bell mouth 12 by the plurality of ribs 22 as described above. The channel cross-sectional area of the bell mouth 12 increases toward the upstream. The bell mouth 12 and the upper throat 13 are integrated, and the upper end of the upper throat 13 is connected to the lower end of the bell mouth 12. That is, the bell mouth 12 and the upper throat 13 are machined from one material by machining. The upper end of the upper throat 13 and the lower end of the bell mouth 12 can be joined by welding. The channel cross-sectional area of the upper throat 13 is the smallest between the bell mouth 12 and the diffuser 17.

  The lower throat 13B has a fitting portion 28 having an outer diameter increased at the upper end portion. Furthermore, the lower throat 13B has a flow channel expanding portion 14 and a taper portion (flow channel reducing portion) 15 at the lower end (see FIG. 2). The flow path expanding portion 14 gradually expands the flow path area toward the lower end of the lower throat 13B. As for the taper part 15, this upper end is connected with the lower end of the flow-path expansion part 14, and the flow-path area is reducing toward a lower end.

  The diffuser 17 installed on the shroud support 9 has a fitting portion 18 having an outer diameter increased at the upper end. Four guide protrusions 19 are provided at equal intervals in the circumferential direction on the outer surface of the upper end portion of the fitting portion 18. The outer diameter at the joint between the flow path enlarged portion 14 and the tapered portion 15 of the lower throat 13B is larger than the inner diameter at the upper end of the fitting portion 18. The tapered portion 15 is also an outer diameter reduced portion in which the outer diameter decreases toward the lower end of the lower throat 13B.

  The tapered portion 15 of the lower throat 13B is fitted into the fitting portion 18 of the diffuser 17. Since the guide protrusion 19 exists, the insertion property into the fitting part 18 of the taper part 15 improves. The upper end portion of the inner surface of the fitting portion 18 is in contact with the entire circumference of the tapered portion 15. In this state, the lower throat 13B is attached to a riser bracket 24 installed on the riser pipe 9.

  A lower end portion of the upper throat 13A is fitted into a fitting portion 28 formed at an upper end portion of the lower throat 13B. The slip joint 16 is configured by the lower end portion of the upper throat 13A inserted into the fitting portion 28 and the fitting portion 28 of the lower throat 13B. In the present embodiment, the slip joint 16 is provided in the throat 13.

  The jet pump 10 according to the present embodiment is configured by modifying an existing conventional jet pump installed in an existing boiling water reactor. The modification of the existing jet pump is executed as follows. The remodeling will take place during the periodical inspection after the boiling water reactor is shut down.

  Before the periodic inspection starts after the operation of the boiling water reactor is stopped, the lid 1A of the RPV 1 is removed. The steam separator 4 and the steam dryer 5 installed in the RPV 1 are removed and taken out of the RPV 1. The entire fuel assembly loaded in the core 2 is taken out from the RPV 1 and stored in a fuel storage pool (not shown). The existing jet pump inlet mixer includes an elbow 20, a nozzle 11, a bell mouth 12 and a throat. A bolt (not shown) connecting the elbow 20 and the riser pipe 9 is removed, and the connection state between the lower throat 13B and the riser bracket 24 is released. Thereafter, the inlet mixer is removed from the RPV 1 through the downcomer 6. At this time, the throat of the inlet mixer is taken out from the fitting portion 18 of the slip joint provided at the upper end portion of the diffuser 17. The inlet mixer is transported into a temporary storage pool filled with cooling water. The diffuser 17 is left in the existing jet pump in the RPV 1.

  The lower throat 13B is newly manufactured at the factory. Decontaminate the inlet mixer in the equipment temporary storage pool to remove adhering radioactive material. After this decontamination, the throat of the inlet mixer is machined, and the upper throat 13A having a reduced length is manufactured in a state of being integrated with the nozzle 11.

  The lower throat 13B newly manufactured at the factory is carried into the RPV 1 and transferred to the position of the fitting portion 18 of the diffuser 17 through the downcomer 6. The tapered portion 15 of the lower throat 13B is fitted into the fitting portion 18 of the diffuser 17 as described above. The lower throat 13 </ b> B in which the taper portion 15 is fitted in the fitting portion 18 is attached to the riser bracket 24. The inlet mixer 21 is carried into the downcomer 6 in the RPV 1. The inlet mixer 21 used in this embodiment includes an elbow 20, a nozzle 11, a bell mouth 12, and an upper throat 13A. The lower end portion of the upper throat 13A of the carried-in inlet mixer 21 is fitted into the fitting portion 28 of the lower throat 13B. The elbow 20 is fixed to the riser tube 9 with bolts. With the above operation, the assembly of the jet pump 10 is completed. In the boiling water reactor, ten jet pumps are installed in the RPV 1, but all existing jet pumps are modified to the jet pump 10 of the present embodiment.

  After the assembly and periodic inspection of all the jet pumps 10 are completed, the boiling water reactor is started. Drive water boosted by the recirculation pump 8 is sprayed into the bell mouth 12 from the nozzle 11. Driven water existing in the downcomer 6 around the nozzle 11 is sucked into the bell mouth 12 and the upper throat 13A. The driving water and the driven water that have reached the upper throat 13A are guided to the lower plenum 27 through the lower throat 13B and the diffuser 17, and are supplied to the core 2. The diffuser 17 is gradually enlarged toward the downstream side so that the flow does not cause separation, and the kinetic energy of the cooling water is converted into pressure by the diffuser 17. In the diffuser 17, the pressure of the driven water is higher than the pressure at the position sucked into the bell mouth 12.

  The static pressure in the upper throat 13A and the lower throat 13B becomes lower than the pressure in the downcomer 6 outside the upper throat 13A and the lower throat 13B by the action of the driving water sprayed from the nozzle 11. Therefore, the cooling water (driving water and driven water) flowing into the lower throat 13B leaks to the outside, that is, the downcomer 6 through the gap formed between the upper throat 13A and the lower throat 13B at the slip joint 16. Can be prevented. For this reason, the efficiency of the jet pump 10 is improved and the vibration of the jet pump 10 is also suppressed. Since the upper end portion of the inner surface of the fitting portion 18 is in contact with the entire circumference of the tapered portion 15, the lower throat 13B and the diffuser 17 are sealed by this contact portion. The cooling water flowing into the diffuser 17 can be prevented from leaking to the downcomer 6 through the space between the lower end portion of the lower throat 13B and the upper end portion of the diffuser 17 by the seal. For this reason, the efficiency of the jet pump 10 is further improved. The improvement in the efficiency of the jet pump can widen the upper and lower limits of the core flow rate that can be controlled, and the controllable range of the reactor power is expanded. Furthermore, the power consumption of the recirculation pump 8 is reduced. Further, since the leakage flow from the slip joint 16 does not occur, the vibration of the jet pump 10 is also suppressed.

  Since the slip joint 16 is provided in the throat 13, it is possible to absorb the difference in thermal expansion between the riser pipe 9 and the diffuser 17 during operation of the boiling water reactor.

  In the present embodiment, the taper portion 15 of the lower throat 13B is merely fitted into the fitting portion 18 of the diffuser 17 so that the taper portion 15 is brought into contact with the fitting portion 18. There is no need to weld with. For this reason, the time required for the modification of the existing conventional jet pump can be shortened. Furthermore, since the existing diffuser 17 of the jet pump can be used as it is without processing including the fitting part 18, the time required for the modification can be further shortened.

  In this embodiment, the inlet mixer 21 and the lower throat 13B can be removed, and they can be easily decontaminated when necessary.

  A jet pump according to embodiment 2, which is another embodiment of the present invention, will be described below with reference to FIG. The jet pump 10A of the present embodiment has a configuration in which the lower throat 13A is replaced with the lower throat 13C and the diffuser 17 is replaced with the diffuser 17A in the jet pump 10 of the first embodiment. The other configuration of the jet pump 10A is the same as that of the jet pump 10. Portions different from the jet pump 10 in the configuration of the jet pump 10A will be described below.

  A male screw 30 is formed on the outer surface of the lower end of the lower throat 13C. A fitting portion 28 is formed at the upper end of the lower throat 13C in the same manner as the lower throat 13B. The diffuser 17 </ b> A has a female screw 31 formed on the inner surface of the fitting portion 18 at the upper end. The lower end of the lower throat 13C is inserted into the fitting portion 18 of the diffuser 17A, and the male screw 30 of the lower throat 13C is engaged with the female screw 31 of the diffuser 17A. The lower throat 13C is attached to the riser bracket 24 in the same manner as the lower throat 13B. Although not shown, the lower end portion of the upper throat 13A is fitted into the fitting portion 28 of the lower throat 13B.

  The jet pump 10A of the present embodiment is a jet pump that is a modification of an existing conventional jet pump. About this modification, a different part from the modification of the conventional jet pump in Example 1 is demonstrated. The upper throat 13A is manufactured in the same manner as in the first embodiment. The lower throat 13C having the male screw 30 formed at the lower end is manufactured at the factory. In the periodic inspection period after the operation of the boiling water reactor is completed, a processing device in which a female screw 31 is carried into the downcomer 6 on the inner surface of the fitting portion 18 of the existing diffuser 17 installed in the shroud support 9 is used. Produced. The diffuser 17A is manufactured by forming the female screw 31 on the existing diffuser 17.

  During the periodic inspection period, the lower throat 13C is carried into the downcomer 6, and the male screw 30 of the lower throat 13C is engaged with the female screw 31 formed in the fitting portion 18 of the diffuser 17A. In this way, the lower throat 13C is attached to the diffuser 17A. The lower throat 13C is further attached to the riser bracket 24. The lower throat 13C and the diffuser 17A are sealed with each other by screw connection. The lower end portion of the upper throat 13A is fitted into the fitting portion 28 of the lower throat 13C, and the elbow 20 is fixed to the riser pipe 9 with bolts. A slip joint 16 constituted by a lower end portion of the upper throat 13A and a fitting portion 28 of the lower throat 13C is provided in the throat 13.

  In the present embodiment, the cooling water does not leak to the outside between the upper throat 13A and the lower throat 13C and between the lower throat 13C and the diffuser 17A, so that each effect produced in the first embodiment can be obtained. In this embodiment, since it is necessary to process the female screw 31 in the fitting portion 18 of the diffuser 17A, the time required for remodeling the jet pump is longer than that in the first embodiment. However, since it is not necessary to weld the lower end of the lower throat 13C and the upper end of the diffuser 17, the time required for remodeling the existing jet pump can be shortened. Since the lower throat 13C is screwed to the diffuser 17A, the lower throat 13C can be removed from the diffuser 17A. For this reason, decontamination of the lower throat 13C can be easily performed as needed.

  A jet pump according to embodiment 3, which is another embodiment of the present invention, will be described below with reference to FIG. The jet pump 10B of the present embodiment has a configuration in which the lower throat 13A is replaced with the lower throat 13D and the diffuser 17 is replaced with the diffuser 17B in the jet pump 10 of the first embodiment. The other configuration of the jet pump 10B is the same as that of the jet pump 10. Portions different from the jet pump 10 in the configuration of the jet pump 10B will be described below.

  As shown in FIG. 6, the lower throat 13 </ b> D is provided with a plate-like annular member 35 at the lower end. In the annular member 35, a pair of through holes 36A and 36B are formed at four positions every 90 ° in the circumferential direction. The diffuser 17B is provided with connecting projection members 38 at four locations on the outer surface of the fitting portion 18 located at the upper end. Each connecting projection member 38 forms a notch 39. As shown in FIG. 7, the U-shaped clamp 40 has a screw 41 formed at one end and a screw 42 formed at the other end. In the clamp 40, the length on the side where the screw 42 is formed is shorter than the length on the side where the screw 41 is formed.

  An annular member 35 of the lower throat 13D is placed on the upper end of the fitting portion 18 of the diffuser 17B. At this time, the part below the connection projection member 38 of the lower throat 13D is inserted into the fitting portion 18 (see FIG. 8). The clamp 40 is inserted into the notch 39 of the connecting projection member 38. An end portion of the clamp 40 on which the screw 41 is formed is inserted into the through hole 36 </ b> A and protrudes upward from the annular member 35. A nut 43 </ b> A is engaged with the screw 41 from above the annular member 35. An end portion of the clamp 40 where the screw 42 is formed is inserted into the through hole 36 </ b> B and protrudes upward from the annular member 35. A nut 43B meshes with the screw 42 from above the annular member 35. By tightening the nuts 43A and 43B, the lower throat 13D is coupled to the diffuser 17B. Similarly, clamps 40 are attached to the other three connecting projection members 38, and nuts 43 </ b> A and 43 </ b> B are engaged with both ends of the clamp 40.

  The jet pump 10B of the present embodiment is a jet pump obtained by modifying an existing conventional jet pump. About this modification, a different part from the modification of the conventional jet pump in Example 1 is demonstrated. The upper throat 13A is manufactured in the same manner as in the first embodiment. The lower throat 13D to which the annular member 35 in which the pair of through holes 36A and 36B are formed at four places is attached is manufactured at a factory. In the periodical inspection period after the operation of the boiling water reactor is stopped, an electrical discharge machining (EDM) apparatus is carried into the downcomer 6. Four guide protrusions 19 provided on an existing diffuser 17 provided on the shroud support 9 are processed using an electric discharge machining apparatus. That is, the guide protrusion 19 is cut at the upper end surface of the fitting portion 18 of the diffuser 17. Further, the guide protrusion 19 is processed by an electric discharge machining apparatus to form a notch 39. As a result, the production of the connecting projection member 38 in which the notch 39 is formed is completed, and the diffuser 17B having the connecting projection member 38 is completed (see FIG. 9).

  The lower throat 13D is carried into the downcomer 6 during the periodic inspection period. At the time of loading, the clamp 40 is suspended from the annular member 35 of the lower throat 13D (see FIG. 10). The end of the clamp 40 on which the screw 41 is formed is inserted into a through hole 36 </ b> A formed in the annular member 35, and the nut 43 </ b> A is engaged with the screw 41 from above the annular member 35. The screw 41 is not completely tightened. The end of the clamp 40 on which the screw 42 is formed is not inserted into the through hole 36 </ b> B formed in the annular member 35, and the nut 43 </ b> B is not attached to the screw 42. The clamp 40 is not inserted into the notch 39 and faces the radial direction of the lower throat 13D.

  The annular member 35 of the lower throat 13D in which the clamp 40 is suspended as shown in FIG. 10 is placed on the upper end of the fitting portion 18 of the diffuser 17B. The connecting projection member 38 provided on the diffuser 17B is located between the through hole 36A and the through hole 36B formed in the annular member 35. The clamp 40 is rotated 90 ° so that the end portion where the screw 42 is formed is directly below the through hole 36B (see FIG. 11). In this state, the nut 43A meshed with the screw 41 is tightened using a long tongue. The clamp 40 ascends and enters the notch 39, and the end where the screw 42 is formed is inserted into the through hole 36B. The nut 43A is completely tightened until the screw 42 comes above the annular member 35. The nut 43B is engaged with the screw 42 and completely tightened. Thus, the lower throat 13D is attached to the diffuser 17B. The lower end portion of the upper throat 13A is fitted into the fitting portion 28 of the lower throat 13D, and the elbow 20 is fixed to the riser pipe 9 with bolts. The annular member 35 and the fitting portion 18 are brought into close contact with each other to seal between the lower throat 13D and the diffuser 17B.

  In the present embodiment, the cooling water does not leak to the outside between the upper throat 13A and the lower throat 13D and between the lower throat 13D and the diffuser 17B, so that each effect produced in the first embodiment can be obtained. In this embodiment, since it is necessary to process the connecting projection member 38 having the notch 39, the time required for remodeling the jet pump is longer than that in the first embodiment. However, it is not necessary to weld the lower end of the lower throat 13D and the upper end of the diffuser 17B, and the connecting projection member 38 also processes the guide projection 19 originally installed on the diffuser, so that it takes time to modify the existing jet pump. It can be shortened. Since the lower throat 13D is detachably attached to the diffuser 17B by the clamp 40 and nuts 43A and 43B, the lower throat 13D can be removed from the diffuser 17B. For this reason, the lower throat 13D can be easily decontaminated as necessary.

  Instead of the clamp 40, as shown in FIG. 12, a clamp 40 </ b> A in which the end portion forming the screw 42 is shortened and the screw 42 is not formed may be used. Similar to the clamp 40, the clamp 40 </ b> A is inserted into the notch 39 of the connecting projection member 38, and the nut 43 </ b> A is engaged with the screw 41 formed on the clamp 40 from above the annular member 35. The lower throat 13D can be attached to the diffuser 17B by tightening the nut 43A.

  The present invention can be applied to a jet pump used in a boiling water reactor.

  DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Core, 3 ... Core shroud, 6 ... Downcomer, 8 ... Recirculation pump, 10, 10A, 10B ... Jet pump, 11 ... Nozzle, 12 ... Bellmouth, 13 ... Throat, 13A ... Upper throat, 13B, 13C, 13D ... Lower throat, 14 ... Flow path enlarged portion, 15 ... Tapered portion, 16 ... Slip joint, 17, 17A, 17B ... Diffuser, 18, 28 ... Fitting portion, 19 ... Guide protrusion, DESCRIPTION OF SYMBOLS 20 ... Elbow, 21 ... Inlet mixer, 30 ... Male screw, 31 ... Female screw, 35 ... Ring member, 38 ... Connection protrusion member, 39 ... Notch part, 40 ... Clamp, 43A, 43B ... Nut.

Claims (6)

A nozzle for ejecting a driving fluid; a throat including a first throat and a second throat into which the driving fluid and a driven fluid sucked by the ejection of the driving fluid flow; and a first end portion on the downstream side of the second throat And a diffuser having an upstream second end that is detachably contacted,
A contact portion between the first end of the second throat and the second end of the diffuser is sealed;
A jet pump characterized in that a slip joint is constituted by a third end portion on the downstream side of the first throat and a fourth end portion on the upstream side of the second throat. In the first end portion of the second throat, an outer diameter reduction portion is formed in which the outer diameter of the first end portion decreases toward the tip of the first end portion,
2. The jet pump according to claim 1, wherein the outer diameter reducing portion is inserted into the second end portion of the diffuser, and the sealing is performed at a contact portion between the outer diameter reducing portion and the second end portion. At the first end portion of the second throat, a flow path expanding portion in which the flow path cross-sectional area increases toward the tip of the first end portion, and the flow path expanding portion connected to the flow path expanded portion from the flow path expanded portion. A flow path reduction portion is formed in which the flow path cross-sectional area decreases toward the tip of the first end,
The outer diameter at the connection point between the flow channel expanding portion and the flow channel reducing portion is larger than the inner diameter at the tip of the second end of the diffuser,
2. The jet pump according to claim 1, wherein the flow path reducing portion is inserted into the second end portion of the diffuser, and the sealing is performed at a contact portion between the flow path reducing portion and the second end portion.   The first end portion of the second throat and the second end portion of the diffuser are screwed together, and the sealing is performed at a screw joint portion between the first end portion and the second end portion. Item 6. The jet pump according to Item 1. An annular member surrounding the first end is provided at the first end of the second throat, the annular member is brought into contact with the end surface of the second end of the diffuser,
2. The jet pump according to claim 1, wherein a plurality of clamps respectively hooked on a plurality of connecting projections provided on an outer surface of the second end are detachably attached to the annular member. A reactor vessel and a plurality of jet pumps installed in the reactor vessel and supplying coolant to a reactor core provided in the reactor vessel;
A nuclear reactor characterized in that the jet pump is the jet pump according to any one of claims 1 to 5.

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