JP5089550B2 - Jet pump and reactor - Google Patents

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.

  A conventional boiling water reactor (BWR) has a jet pump installed in a reactor pressure vessel. The jet pump includes a nozzle, a bell mouth, a throat, and a diffuser. The recirculation piping is connected to the reactor pressure vessel. The cooling water whose pressure has been increased by driving a recirculation pump provided in the recirculation system pipe passes through the recirculation system pipe and is jetted from the nozzle into the jet pump as drive water. Due to the jetted driving water, the cooling water existing around the nozzle flows into the bell mouth and the throat as driven water. The cooling water led from the throat to the diffuser and discharged from the diffuser is supplied to the core through the lower plenum (see, for example, Japanese Patent Application Laid-Open No. 2005-233152).

  Japanese Patent Application Laid-Open No. 7-119700 describes a jet pump that generates a swirling flow using a porous nozzle. In this jet pump, the pressure loss in the diffuser and the throat is reduced for the purpose of improving the jet pump efficiency. In order to reduce pressure loss, it has been proposed to provide a fin or groove for generating a swirling flow on the inner surface of one of the diffuser and the throat. When a fin or groove resistor that swirls a straight fluid is provided, friction loss occurs at the installation location. For this reason, the pressure loss in a diffuser or a throat increases, and there exists a possibility of causing the fall of jet pump efficiency.

  Japanese Patent Application Laid-Open No. 8-135600 discloses a jet pump in which the throat friction loss is reduced in order to improve the jet pump efficiency. In this jet pump, a riblet is formed on the inner surface of the throat by arranging a plurality of narrow grooves formed along the fluid flow direction in the circumferential direction. In JP-A-8-135600, the riblet is defined as having a height equal to the thickness of the viscous bottom layer of fluid turbulence. The thickness of the viscous bottom layer of this fluid turbulent flow is usually 0.1 mm or less, and the thickness of the viscous bottom layer is smaller than this value at the throat portion at a high flow rate. Japanese Patent Laid-Open No. 8-135600 discloses equation (1) for obtaining the height of the riblet.

δ ₁ = 123 · (uD / ν) ^7/8 · δ (1)
Where δ ₁ is the thickness of the turbulent viscous bottom layer, uD / ν is the Re number (−), u is the fluid flow velocity, D is the inner diameter of the tube, ν is the viscosity coefficient, and δ is the radius of the tube.

In a BWR jet pump, the Re number is usually about 1 × 10 ⁶ and the minimum tube radius at the throat is about 80 mm. By substituting these into the equation (1), the bullet height δ ₁ is about 2 × 10 6. ⁶ mm (2 km). This is about 12,500 times the tube diameter, and the height of the bullet cannot be obtained from the equation (1).

JP-A-2005-233152 JP 7-119700 A JP-A-8-135600

  The performance of the jet pump is expressed by the M ratio, N ratio, and efficiency as shown below. The M ratio is a ratio of the flow rate Qb of the driven water (cooling water) to the flow rate Qa of the drive water (recirculation water), and is expressed by the equation (2).

M ratio = Qb / Qa (2)
The N ratio is the total head ratio of the driven water with respect to the driving water, and is expressed by equation (3).

N ratio = (Hc−Hb) / (Ha−Hc) (3)
Here, Ha is the total head at the driving water inlet of the nozzle, Hb is the total head at the driven water inlet of the jet pump, and Hc is the total head at the jet pump outlet. Efficiency is the ratio of driven water energy to driving water, and is expressed as the product of the M ratio and the N ratio.

Efficiency = M ratio x N ratio (4)
As a jet pump, it is desirable that the M ratio, the N ratio, and the efficiency be higher. If the flow rate of the cooling water discharged from the jet pump can be increased efficiently by using a small-capacity recirculation pump, the recirculation system can be made compact and the installation space of the recirculation system can be reduced.

  For example, when the power is improved in an existing nuclear reactor (for example, BWR), the increase in the reactor power can be expanded by increasing the core flow rate to increase the cooling capacity of the core. In order to increase the core flow rate in this way, the recirculation pump, feed water pump, and jet pump may be improved. In the modification of existing reactors for the purpose of improving power output, the improvement of the jet pump is more effective in terms of time compared to the modification and replacement of large equipment such as recirculation pumps and feedwater pumps. Since the performance of the jet pump largely depends on the shape of the mixing portion of the driving water and the driven water, the inventors paid attention to the reduction of the pressure loss at the throat. Furthermore, the inventors have found that the adhesion of the clad that occurs in the vicinity of the connection between the bell mouth of the jet pump and the straight pipe portion also causes a reduction in the jet pump efficiency.

An object of the present invention, it is possible to further improve the jet pump efficiency, and to provide a jet pump and reactor are Ru can suppress vibration of the jet pump.

A feature of the present invention that achieves the above-described object is that the throat is connected to the bell mouth and has an inner diameter smaller than the inner diameter at the open end of the bell mouth, than the inner diameter of the first straight pipe portion. The second straight pipe part having a large inner diameter and connected to the diffuser, and the first straight pipe part and the second straight pipe part are connected, and one end of the first straight pipe part side is connected to the second straight pipe part side. toward the other end have a coupling pipe portion whose inner diameter is increased, the inner surface of the second straight pipe portion of the inner surface and the diffuser at the lower end of the second straight pipe portion and the second straight pipe portion is inserted into the upper end portion of the diffuser and step is formed between, in Rukoto has a plurality of triangular grooves extending in the axial direction of the throat is formed on the inner surface of the second straight pipe portion in the circumferential direction of the second straight pipe portion.

Since the portion connected to the diffuser of the throat is the second straight pipe portion, the efficiency of the jet pump can be further improved. The axial direction of the throat with the second straight pipe portion inserted into the upper end portion of the diffuser and a step formed between the inner surface of the second straight pipe portion and the inner surface of the diffuser at the lower end of the second straight pipe portion Are formed in the inner surface of the second straight pipe portion in the circumferential direction of the second straight pipe portion, pressure fluctuations near the inner surface of the diffuser inlet portion are reduced, and vibration of the jet pump is suppressed. be able to.

According to the present invention, it is possible to further improve the efficiency of the jet pump, and Ru can suppress the vibration of the jet pump.

  The throat of a conventional jet pump is connected to a bell mouth that is opened in a trumpet shape that serves as an inlet for driving water ejected from the nozzle and driven water existing around the nozzle, and is located downstream of this. A first straight pipe part serving as a water mixing part, a taper pipe located downstream of the first straight pipe part, and an insertion pipe part serving as a connection part to the diffuser.

There are three possible causes of pressure loss at this throat.
(A) The substantial channel cross-sectional area is narrowed by the ring-shaped decompression region generated by the contraction flow in the vicinity of the connection portion between the bell mouth and the first straight pipe portion.
(B) There is a friction loss in the first straight pipe portion having the smallest flow path cross-sectional area and a backflow loss due to a vortex in the first straight pipe portion.
(C) There is an expansion flow loss due to a sudden expansion flow occurring at the connection portion due to the inflow of cooling water from the insertion tube portion which is a connection portion with the diffuser to the upper end portion of the diffuser.

  The inventors first studied a jet pump that can reduce the pressure loss of (a) and (b). The inventors conducted an experiment in order to confirm the pressure loss when the triangular grooves were formed on the inner surfaces of the bell mouth and the first straight pipe portion and the connecting portion of the throat. The result of this experiment will be described with reference to FIG. FIG. 11 shows a tube having an inner diameter of 55 mm (distance between triangular protrusions formed on the opposite side of the 180 ° formed between adjacent triangular grooves in a tube having a triangular groove), and the Reynolds number Re is made using water. The experimental result performed by 250,000 is shown. Here, the horizontal axis represents the depth of the triangular groove, and the vertical axis represents the friction loss coefficient λ of the pipe. The friction loss coefficient is defined by the following equation.

ΔP = λ · L / D · 1/2 · ρu ² (5)
Where ΔP is the friction loss, λ is the friction loss coefficient, L is the length of the tube, D is the inner diameter of the tube, ρ is the fluid density, and u is the flow velocity.

  As shown in FIG. 5, a plurality of triangular grooves are formed in the circumferential direction on the inner surface of the first straight pipe portion of the throat. Experimental results when water is caused to flow in the two first straight pipe portions each forming the triangular groove whose angle (bottom angle) formed by the two faces facing each other is 90 ° and 60 °, ie, the triangular groove FIG. 11 shows the relationship between the depth and the friction loss coefficient. In addition, experimental results for commercially available acrylic tubes and commercially available stainless steel tubes are also shown. Since there is only one point of experimental data for the first straight pipe part in which the 60 ° triangular groove is formed, the result obtained by simulation is indicated by a broken line.

  The friction loss coefficient of the first straight pipe portion in which the triangular groove having the bottom angle of 90 ° is formed is smaller than that of the first straight pipe portion in which the triangular groove having the bottom angle of 60 ° is formed. In the case where a triangular groove having a bottom angle of 90 ° is formed, the friction loss coefficient increases when the depth of the triangular groove is smaller than 1.0 mm. In the case of a triangular groove having a bottom angle of 90 °, when the depth of the triangular groove is 1.3 mm or more, the friction loss coefficient is reduced to be equal to the friction loss coefficient of commercially available acrylic pipes and commercially available stainless steel pipes. For this reason, in the case of forming a triangular groove having a bottom angle of 90 °, the depth of the triangular groove is 1.0 mm or more, preferably 1.3 mm or more.

  In the case where a triangular groove having a bottom angle of 60 ° is formed, the friction loss coefficient increases when the depth of the triangular groove is smaller than 1.5 mm. In the case where a triangular groove having a bottom angle of 60 ° is formed, when the depth of the triangular groove is 1.9 mm or more, the friction loss coefficient is reduced to be equal to the friction loss coefficient of commercially available acrylic pipes and commercially available stainless steel pipes. . For this reason, in the case of forming a triangular groove having a bottom angle of 60 °, the depth of the triangular groove is 1.5 mm or more, preferably 1.9 mm or more with a friction loss coefficient equivalent to that of a commercially available stainless steel pipe. Is preferred.

  The rectifying effect in the first straight pipe portion increases as the depth of the triangular groove increases. However, when the depth of the triangular groove is increased, the strength of the throat is reduced. Therefore, the depth of the triangular groove is determined in consideration of the rectification effect and the strength of the throat. The depth of this triangular groove is 5.0 mm or less. The thickness of the throat of the jet pump used in the nuclear reactor is about 10 mm. From the viewpoint of strength, the upper limit of the depth of the triangular groove is set to 5.0 mm, which is half the thickness of the throat.

  FIG. 12 shows the experimental results and simulation results shown in FIG. 11 in relation to the angle of the bottom of the triangular groove and the depth of the triangular groove. The characteristic curve B shows that the friction loss coefficient is small, the triangular groove depth is 1.0 mm in the triangular groove whose bottom angle is 90 °, and the triangular groove depth is 1.5 mm in the triangular groove whose bottom angle is 60 °. It is the curve obtained based on. Characteristic curve A shows the depth of the triangular groove 1.3 mm and the bottom of the triangular groove in a triangular groove having a bottom angle of 90 °, which is equivalent to the friction loss coefficient of a commercially available acrylic tube and a commercially available stainless steel tube having the most preferable friction loss coefficient. It is a curve obtained based on a triangular groove depth of 1.9 mm in a triangular groove having an angle of 60 °.

  As a result, the lower limit value of the triangular groove depth h (mm) is expressed by equation (6) based on the characteristic curve B.

h = −1.5767 · lnθ + 18.1629 (6)
Here, θ is the angle of the bottom of the triangular groove. lnθ is the natural logarithm of θ. A preferable lower limit value of the depth h (mm) of the triangular groove where the friction loss coefficient is equivalent to that of a commercially available acrylic tube and a commercially available stainless steel tube is represented by the equation (7) based on the characteristic curve A.

h = −1.7219 · lnθ + 9.0299 (7)
As a result, if the depth h (mm) of the triangular groove is within a range that satisfies the formula (8) obtained based on the formula (6), the friction loss coefficient of the first straight pipe portion is reduced. Can do.

−1.5767 · lnθ + 1.629 ≦ h ≦ 5.0 mm (8)
The depth h (mm) of the triangular groove preferably satisfies the expression (9) obtained based on the expression (7).

-1.7219 · lnθ + 9.0299 ≦ h ≦ 5.0 mm (9)
The position of the apex of the triangular protrusion formed between the adjacent triangular grooves is made to coincide with the inner diameter of the first straight pipe portion of the throat of the conventional example. As a result, a reduced pressure region generated by contraction in the vicinity of the connecting portion between the bell mouth and the first straight pipe portion is formed in the triangular groove. can do. Further, the cooling water flowing into the bell mouth flows into the triangular groove, and the triangular groove also serves as a guide for the cooling water. The triangular groove has such a rectifying function.

  In the jet pump, the friction loss of the first straight pipe portion having the smallest flow path cross-sectional area downstream from the upper end of the bell mouth is changed from a triangular groove having a depth h satisfying the equation (8) to the first straight pipe portion. It becomes smaller by forming. The backflow loss in the vicinity of the inner surface of the first straight pipe portion due to the vortex generated in the first straight pipe portion is caused by the vortex flowing in the triangular groove and the cooling water being rectified by the triangular groove. In the mainstream of cooling water flowing through

  You may form the triangular groove | channel which has the depth h which satisfies (8) Formula or (9) Formula in the inner surface of a bellmouth.

  The inventors also examined the above-mentioned (c). The expansion flow loss in the conventional structure that occurs when the cooling water flowing through the throat flows out of the insertion tube, which is the connection part of the throat with the diffuser, is a wide area where the cooling water has a step from the tapered part of the throat. It is generated by flowing into the (diffuser). In such a flow channel shape, the cooling water rapidly spreads from the lower end of the insertion tube portion toward the inner surface side of the diffuser whose diameter has been expanded, so that a sudden pressure change occurs near the inner surface of the lower end portion of the insertion tube portion. Occur. For this reason, random vortices are generated in the water stop region formed in the vicinity of the lower end of the insertion tube portion, and pressure loss (expanded flow loss) increases due to flow disturbance caused by the vortices. In order to reduce this pressure loss, the lower end portion of the insertion tube portion is not a tapered tube having a divergent inside, but is a second straight tube portion, and the inner surface of the second straight tube portion is represented by the formula (8) or (9) A plurality of triangular grooves having a depth h satisfying These triangular grooves are formed side by side in the circumferential direction on the inner surface of the straight pipe of the insertion pipe portion. Disturbances in the vicinity of the inner surface of the upper end portion of the diffuser of the cooling water flowing into the diffuser from the lower end portion of the insertion pipe portion are suppressed, and the flow of the cooling water is stabilized. For this reason, pressure loss can be reduced in the flow path area enlarged portion from the lower end of the insertion tube portion to the upper end portion of the diffuser. In particular, the efficiency of the jet pump is improved by forming a second straight pipe portion having the same inner diameter from the inlet toward the outlet at the lower end of the insertion pipe. The inner diameter of the second straight pipe portion is larger than the inner diameter of the first straight pipe portion. By forming a plurality of triangular grooves in the second straight pipe portion, vibration of the jet pump can be suppressed. This is because the cooling water is not jetted into the diffuser from the tapered pipe like the structure in which the inner surface of the tapered pipe outlet of the throat in the conventional jet pump is inclined to the lower end of the tapered pipe, The second straight pipe portion can form a cooling water flow that flows just below with little spread outward at the inlet portion of the diffuser, and can increase the pushing force of the cooling water into the diffuser. Further, the second straight pipe By forming a triangular groove on the inner surface of the part, the flow near the inner surface of the second straight pipe part becomes gentle, and by rectifying the flow, pressure fluctuations near the inner surface of the diffuser inlet part are reduced. is there.

  It is preferable that the triangular groove satisfying the expression (8) or the expression (9) is formed to extend from the upper end of the bell mouth to the lower end of the first straight pipe portion of the throat. In the vicinity of the connection portion between the bell mouth and the first straight pipe portion, as described above, a reduced pressure region generated due to the contracted flow is formed in the triangular groove. When the triangular groove is formed, the formed decompression region is not ring-shaped but has irregularities due to the triangular groove existing in the circumferential direction. The clad contained in the cooling water flowing into the bell mouth tends to adhere to the surface of the triangular groove facing the decompression region in the triangular groove. However, the flow rate of the cooling water flowing in the triangular grooves continuously connected from the bell mouth is slow because the flow resistance in the triangular grooves is large. As a result, the reduced pressure region formed in the triangular groove is reduced, and the adhesion of the clad to the surface of the triangular groove is suppressed.

  The place where the hydrodynamic vibration is generated in the jet pump is the first straight pipe section of the throat which is the mixing section and has the smallest pressure fluctuation of the jet flow from the nozzle and the cross-sectional area of the flow path. By forming a plurality of triangular grooves having a depth h satisfying the expression (8) or (9) on the inner surface of the first straight pipe portion, the rectifying effect of these triangular grooves and the first straight groove Since the pressure fluctuation due to the vortex in the pipe part can be absorbed in the triangular grooves, the main flow of the cooling water flowing in the first straight pipe part can be stabilized, and the fluid vibration Can be reduced.

  By forming the triangular groove described above, the pressure loss can be reduced, and accordingly, the total head Hc at the jet pump outlet, which is the discharge pressure of the diffuser, can be increased. For this reason, the efficiency of the jet pump can be improved by increasing the N ratio.

  Examples of the present invention reflecting the above examination results will be described below.

  A jet pump according to a first embodiment which is a preferred embodiment of the present invention will be described with reference to FIGS.

  A schematic structure of a boiling water reactor (BWR) to which the jet pump 13 of this embodiment is applied will be described first with reference to FIGS.

  The BWR has a reactor pressure vessel (reactor vessel) 1 and a reactor core shroud 3 is installed in the reactor pressure vessel 1. A core 3 loaded with a plurality of fuel assemblies (not shown) is surrounded by a core shroud 3. A steam separator 4 and a steam dryer 5 are disposed above the core 2 in the reactor pressure vessel 1. A jet pump 13 is disposed in an annular downcomer 6 formed between the reactor pressure vessel 1 and the core shroud 3. The reactor pressure vessel 1 is provided with a recirculation system having a recirculation system pipe 9 and a recirculation pump 10. A recirculation system pipe 9 provided with a recirculation system pump 10 has one end connected to the reactor pressure vessel 1 and connected to the downcomer 6, and the other end connected to a riser pipe 11 disposed in the downcomer 7. . The branch pipe 12 is connected to the upper end of the riser pipe 11, and the nozzle holders 18 of the two jet pumps 13 are connected to the branch pipe 12. A main steam pipe 7 and a water supply pipe 8 are connected to the reactor pressure vessel 1. Two jet pumps 13 each having a nozzle holder 18 connected to one branch pipe 12 are arranged on both sides of one riser pipe 11.

  The cooling water (driven fluid) existing in the upper part of the reactor pressure vessel 1 is mixed with the feed water 38 supplied to the reactor pressure vessel 1 from the feed water pipe 8 and descends in the downcomer 6. The cooling water 31 flows into the recirculation pipe 9 by driving the recirculation pump 10 and is boosted by the recirculation pump 10. The raised cooling water 8 is referred to as driving water (driving fluid) for convenience. The drive water 32 is ejected from the nozzle 14 of the jet pump 13 into the bell mouth 15 through the recirculation system pipe 9, the riser pipe 11 and the branch pipe 12. The cooling water 31 in the downcomer 6 existing around the nozzle 14 is sucked into the throat 16 from the bell mouth 15 by the ejection of the driving water 32. The cooling water 31 descends in the throat 16 together with the driving water 32 and is discharged from the diffuser 17. The cooling water (including the cooling water 31 and the driving water 10) discharged from the diffuser 17 is referred to as cooling water 33. The cooling water 33 is supplied to the core 2 through the lower plenum 21. The cooling water 33 is heated when passing through the core 2 and becomes a two-phase flow containing water and steam. The steam separator 4 separates steam and water. The separated steam is further dehumidified by the steam dryer 5 and discharged to the main steam pipe 7. This steam is guided to a steam turbine (not shown) to rotate the steam turbine. The steam discharged from the steam turbine is condensed into water by a condenser (not shown). This water is supplied into the reactor pressure vessel 1 from the water supply pipe 8 as water supply 38. The water separated by the steam separator 4 and the steam dryer 5 falls and becomes cooling water 31.

  The jet pump 13 having the nozzle 14 and the like effectively transmits the power of the recirculation pump 10 from the driving water 32 to the cooling water 31, and the flow rate of the cooling water 33 discharged from the jet pump 13 is larger than the flow rate of the driving water 32. Increase. Specifically, the driving water 32 is used to increase the flow rate of the cooling water 33 supplied to the core 2. When the kinetic energy of the driving water 32 given by the recirculation pump 10 acts on the cooling water 31 effectively, the cooling water 31 is driven and the flow rate of the cooling water 33 further increases. Therefore, the flow velocity of the drive water 32 at the outlet of the nozzle 14 is increased so that the kinetic energy of the drive water 32 increases, and the flow path cross-sectional area of the throat 16 is larger than that of the open end located at the upper end of the bell mouth 15. Also, the static pressure is reduced by increasing the speed of the cooling water 31. As a result, the cooling water 31 can be sucked into the throat 16 and a necessary core flow rate can be secured with a small amount of power.

  In FIG. 2, variables used in the above formulas (2) and (3) necessary for evaluating the performance of the jet pump 13 are shown together with corresponding portions.

  The jet pump 13 of the present embodiment will be described in detail with reference to FIGS. As shown in FIG. 3, the jet pump 13 includes a nozzle 14, a bell mouth 15, a throat 16, a diffuser 17, and a nozzle holder 18. Five nozzles 14 are attached to a nozzle holder 18 connected to the branch pipe 12 and extend downward from the nozzle holder 18. The bell mouth 15 is disposed below the nozzle 14. The nozzle holder 18 is supported by a plurality of fixing plates 19 (see FIG. 2) provided at the upper end of the bell mouth 15 and arranged in the radial direction of the bell mouth 15. The bell mouth 15 extends from the lower end toward the upper end. The jet pump 13 has a throat 16 and a diffuser 17 disposed below the bell mouth 15. The throat 16 is connected to the lower end of the bell mouth 14, and the diffuser 17 is connected to the lower end of the throat 16 at the slip joint portion 19.

  The throat 16 includes a first straight pipe portion 16A, a taper tube (coupling pipe portion) 16B, and an insertion pipe portion (second straight pipe portion) 16C which are mixing portions from the upper end toward the lower end. The first straight pipe portion 16A is connected to the lower end of the bell mouth 15 and has the smallest channel cross-sectional area below the upper end of the bell mouth 15 of the jet pump 13. The taper pipe 16B is connected to the lower end of the first straight pipe portion 16A, and the flow path cross-sectional area is expanded downward. The insertion pipe part 16C, which is the second straight pipe part, is connected to the lower end of the taper pipe 16B, inserted into the slip joint part 19 provided at the upper end part of the diffuser 17, and connected to the diffuser 17 (see FIG. 3). . The first straight pipe portion 16A and the insertion pipe portion 16C have substantially the same inner diameter from the inlet toward the outlet.

The jet pump 13 forms a plurality of triangular grooves 20A on the inner surface of the bell mouth 15, a plurality of triangular grooves 20B on the inner surface of the first straight pipe portion 16A, and a plurality of triangular grooves 20C on the inner surface of the insertion pipe portion 16C. ing. The triangular grooves 20A, 20B, and 20C are arranged in parallel at equal intervals in the circumferential direction at the corresponding locations. The triangular grooves 20 </ b> A, 20 </ b> B, and 20 </ b> C extend in the axial direction of the jet pump 13.

The plurality of triangular grooves 20 </ b> A are formed on the inner surface continuously from the upper end of the bell mouth 15 to the lower end thereof in the axial direction of the throat 16. FIG. 4 shows a state where the bell mouth 15 is viewed from above, and the triangular grooves 20 </ b> A are arranged side by side in the circumferential direction of the bell mouth 15. The triangular groove 20 </ b> A is also formed on a curved surface formed at the upper end of the bell mouth 15. A plurality of triangular grooves 20B are continuously formed in the axial direction of the throat 16 from the upper end of the first straight pipe portion 16B to the lower end thereof (see FIG. 3). As shown in FIG. 16 A is arranged in the circumferential direction. As shown in FIG. 7, each triangular groove 20B is also formed in a slight range of the upper end portion of the tapered tube 16B. Since the flow path cross-sectional area of the tapered tube 16 is expanded downward, the depth of each triangular groove 20B becomes shallower toward the lower end of the triangular groove 20B. As shown in FIG. 8, the plurality of triangular grooves 20 </ b> C are continuously formed in the axial direction of the throat 16 from the lower end portion of the tapered tube 16 to the lower end of the insertion tube portion 16 </ b> C. The depth of the groove at the upper end of each triangular groove 20C is shallower toward the upper end of the triangular groove 20C.

  The angle θ (see FIG. 6) at the bottom of the triangular groove 20B is 90 °. The angle θ at the bottom of the triangular grooves 20A and 20C is also 90 °. Triangular grooves 20A, 20B. Each depth h of 20C is 1.0 mm that satisfies the relationship of the equation (8).

  The inner diameter of the first straight pipe portion 16A is smaller than the inner diameter at the open end of the bell mouth 15 and the inner diameter of the insertion pipe portion 16C. These inner diameters are the diameters of circles formed by connecting the apexes of the respective triangular protrusions 22 (see FIG. 6) formed between adjacent triangular grooves.

  The driving water 32 having a flow rate Qa guided from the branch pipe 12 into the nozzle holder 18 is ejected from the five nozzles 14 as ejection flows 34, respectively. These jets 34 reach the first straight pipe portion 16 </ b> A through the bell mouth 15. By ejecting the jet stream 34 from each nozzle 14, the cooling water 31 existing around the nozzle 14 in the downcomer 6, that is, the driven water 36 passes between the nozzle 14 and the bell mouth 15 and bell bell mouth 15. Into the first straight pipe portion 16A. The flow rate of the driven water 36 sucked into the bell mouth 15 by the jet of the jet stream 34 is Qb. The flow rate Qb is larger than the flow rate Qa. The jetted driving water 32 and the driven water 36 are mixed in the first straight pipe portion 16A, guided to the diffuser 17 through the tapered pipe 16B and the insertion pipe portion 16C, and from the lower end of the diffuser 17 to the lower plenum. 21 is discharged as cooling water 33. This cooling water 33 is supplied to the core 2.

  In the jet pump 13 of this embodiment, since the insertion pipe portion 16C of the throat 16 is a straight pipe, the efficiency of the jet pump can be improved. The efficiency improvement of this jet pump will be described with reference to FIG.

  FIG. 9 shows an experimental result when water is flowed by changing the shape of the insertion tube portion of the throat inserted into the diffuser. The solid line in FIG. 9 indicates the jet pump efficiency in a jet pump (referred to as a first jet pump) having an insertion tube portion 16C in which the insertion tube portion is a straight tube. As in the first embodiment, a plurality of triangular grooves 20C having a bottom angle θ of 90 ° are formed on the inner surface of the insertion tube portion 16C. In the first jet pump, no triangular groove is formed on the inner surfaces of the first straight pipe portions of the bell mouth and the throat. An experiment using a jet pump (referred to as a second jet pump) in which the triangular groove 20C is not formed on the inner surface of the straight insertion tube portion 16C was performed with the first jet pump, and the solid line result shown in FIG. 9 was obtained. It was. The broken line in FIG. 9 indicates that a conventional jet pump, that is, the inner surface of the first straight pipe part of the bell mouth and the throat does not have a triangular groove, and the inner surface of the insertion pipe part of the throat extends to the lower end of the insertion pipe part. This shows the jet pump efficiency in a conventional jet pump (referred to as a third jet pump) which is widened at the end and has no triangular groove formed on the inner surface of the insertion tube portion.

  According to the above experimental results, the efficiency of the first and second jet pumps, in which the insertion tube portion is a straight tube, is higher than that of the third jet pump regardless of whether the inner surface of the insertion tube portion has a triangular groove. Will improve. As described above, the straight pipe insertion pipe portion can form a cooling water flow that flows underneath with little spread outward at the inlet portion of the diffuser, and the pushing force of the cooling water into the diffuser increases. Because.

  Since the triangular groove 20C is formed on the inner surface of the insertion tube portion 16C that is the second straight tube portion, vibration of the jet pump 13 can be suppressed. This vibration suppression will be described with reference to FIG.

FIG. 10 shows experimental results for confirming vibrations in the three types of jet pumps that obtained the experimental results shown in FIG. 9, that is, the first, second, and third jet pumps. The vertical axis shows the ratio of the fluctuating pressure at the throat outlet to the fluctuating pressure in the nozzle that is the source of pressure fluctuation. That is, the vertical axis represents the attenuation rate of the pressure fluctuation in the throat. According to the experimental results shown in FIG. 10, the third jet pump (insertion pipe portion: end spreading passage) has the largest pressure fluctuation at the throat outlet portion. The first jet pump (insertion pipe part: straight pipe (with 90 ° triangular groove)) and the second jet pump (insertion pipe part: straight pipe (without triangular groove)) are located at the throat outlet part more than the third jet pump. The pressure fluctuation is small, and the pressure fluctuation at the throat outlet in the first jet pump is the smallest.
In this embodiment, since the triangular groove 20A is also formed on the inner surface of the bell mouth 15, the efficiency of the jet pump 13 can be further improved. By forming the triangular groove 20 </ b> A in the bell mouth 15, the decompression region does not have a ring shape but becomes uneven. Since the flow resistance is large and the flow velocity is slow in the triangular groove 20A, the decompression area in the triangular groove 20A is reduced, the flow resistance is reduced, and further, adhesion of the clad is suppressed, and the performance can be maintained.

  In the present embodiment, since the triangular groove 20B is formed also on the inner surface of the first straight pipe portion 16A, a vibration reduction effect can be obtained.

  In the vicinity of the connecting portion between the bell mouth 15 and the first straight pipe portion 16A, a reduced pressure region generated due to the contracted flow is formed in the triangular groove 20B. The clad contained in the cooling water flowing into the bell mouth 15 tends to adhere to the surface of the triangular groove 20B facing the reduced pressure region in the triangular groove 20B. However, since the cooling water flows in the triangular groove 20B continuously connected to the triangular groove 20A formed in the bell mouth 15, the adhesion of the clad to the surface of the triangular groove 20B in the reduced pressure region is suppressed.

  Note that triangular grooves are not formed in most of the inner surface of the tapered tube 16B located downstream of the first straight tube portion 16A in the axial direction. This is because the cooling water flowing into the taper pipe 16B is caused by the effect of the triangular groove 20B formed on the inner surface of the first straight pipe portion 16A located upstream of the taper pipe 16B. This is because it is rectified and stabilized in the vicinity of the inner surface.

  At the connecting portion between the first straight pipe portion 16A and the tapered tube 16B, the depth of the triangular groove 20B becomes shallower toward one end on the tapered tube 16B side, and at the connecting portion between the tapered tube 16B and the insertion tube portion 16C, the depth of the triangular groove 20C. Is shallower toward one end on the tapered tube 16B side. In this manner, by reducing the depth h of the triangular grooves 20B and 20C toward one end, the pressure loss at the portion where the flow path cross-sectional area at the throat 16 changes can be reduced.

The jet pump 13 of the present embodiment in which the triangular mouth 20A, 20B and 20C are formed in the bell mouth 15, the first straight pipe portion 16A and the insertion pipe portion 16C and the jet pump in which none of the triangular grooves 20A, 20B and 20C is formed. FIG. 13 shows the relationship between the M ratio, the jet pump efficiency, and the pressure fluctuation in the throat for each of the above. Characteristics 41 and 42 indicated by solid lines are characteristics with respect to the jet pump 13 of the present embodiment having the straight pipe insertion pipe portion 16C and further forming the triangular grooves 20A, 20B and 20C. Characteristics 43 and 44 indicated by broken lines are characteristics for a jet pump that has an insertion pipe portion in which a diverging passage is formed inside and does not form triangular grooves 20A, 20B, and 20C. Characteristics 41 and 43 show changes in jet pump efficiency with respect to M ratio, and characteristics 42 and 44 show changes in pressure fluctuation in the throat with respect to M ratio.

  The maximum jet pump efficiency of the jet pump 13 having the straight pipe insertion pipe portion 16C and forming the triangular grooves 20A, 20B, and 20C is as follows. It becomes higher than that of the jet pump that does not form 20B and 20C. The former efficiency is about 2% higher than the latter efficiency. The maximum jet pump efficiency of the jet pump 13 is such that a triangular groove is formed on the inner surface of the bell mouth 15, so that the maximum jet pump efficiency provided by the straight pipe insertion pipe portion 16C can be further increased. The pressure fluctuation in the throat in the jet pump 13 having the straight pipe insertion pipe portion 16C and forming the triangular grooves 20A, 20B and 20C has an insertion pipe portion in which a diverging passage is formed, and the triangular groove 20A. , 20B and 20C are smaller than that of the jet pump. The hydrodynamic vibration of the jet pump 13 of this embodiment is reduced. The hydrodynamic vibration of the jet pump 13 takes into account the vibration reduction effect due to the triangular groove 20B formed on the inner surface of the first straight pipe portion 16A, so that it is even more than the reduction in vibration caused by the straight pipe insertion pipe portion 16C. Reduced.

  By replacing the throat of the jet pump with the throat 16 shown in FIG. 3 in the existing BWR, the jet pump installed in the reactor pressure vessel 1 of the existing BWR can be modified to the jet pump 13. By this modification, the efficiency of the existing BWR jet pump can be remarkably increased, and the flow rate of the cooling water 33 supplied to the core 2 in the existing BWR can be remarkably increased. The existing BWR having the modified jet pump 13 can easily realize output improvement with a large output increase range. The bell mouth and the throat can be easily exchanged for the bell mouth 15 and the throat 16 in which the triangular groove is formed on the inner surface by pulling out the throat from the slip joint portion 19.

  In the jet pump 13 of the present embodiment, the pressure loss of the throat 16 is further reduced by setting the depth h of each of the triangular grooves 20A, 20B and 20C within the range of the formula (9), for example, 1.5 mm. This contributes to further improvement in the efficiency of the jet pump 13.

  A jet pump according to embodiment 2, which is another embodiment of the present invention, will be described with reference to FIG. The jet pump 13A of the present embodiment has a structure in which the triangular groove 20B formed on the inner surface of the first straight pipe portion 16A in the jet pump 13 of the first embodiment is substantially removed. The other configuration of the jet pump 13A is the same as that of the jet pump 13.

  The angle of the bottom of each triangular groove 20A formed on the inner surface of the bell mouth 15 and each triangular groove 20C formed on the inner surface of the insertion tube portion 16C is 90 °, and their depth h is expressed by the equation (8). It is 1.0 mm that satisfies the range. Each triangular groove 20A formed on the inner surface of the bell mouth 15 is gradually formed at the lower end so that the depth h coincides with the inner surface of the first straight pipe portion 16A toward one end on the first straight pipe portion 16A side. It is shallow.

  The jet pump 13A of the present embodiment can obtain each effect produced by the jet pump 13 of the first embodiment, except for the effect obtained by forming the triangular groove 20B on the inner surface of the second straight pipe portion 16A.

  M ratio for each of the jet pump 13A of the present embodiment in which triangular grooves 20A and 20C are formed in the bell mouth 15 and the insertion tube portion 16C and the jet pump in which none of the triangular grooves 20A, 20B and 20C is formed. The relationship between the efficiency of the jet pump is shown in FIG. A characteristic 45 indicated by a solid line is a characteristic for the jet pump 13A in which the triangular grooves 20A and 20C are formed. A characteristic 46 indicated by a broken line is a characteristic for a jet pump in which the triangular grooves 20A, 20B and 20C are not formed. The maximum jet pump efficiency of the jet pump 13A is higher than that of the jet pump that does not form the triangular grooves 20A, 20B, and 20C.

  By replacing the throat of the jet pump with the throat 16 shown in FIG. 14 in the existing BWR, the jet pump installed in the reactor pressure vessel 1 of the existing BWR is modified to a jet pump 13A with improved jet pump efficiency. can do.

  In the jet pump 13A of the present embodiment, the triangular groove 20A formed on the inner surface of the bell mouth 15 may be removed. In this jet pump, a triangular groove 20C is formed on the inner surface of the insertion tube portion 16C, which is the second straight tube portion of the throat 16, and a triangular groove is formed on each inner surface of the bell mouth 15 and the first straight tube portion 16A. It has not been. In this jet pump, the triangular groove 20C is formed on the inner surface of the insertion pipe portion 16C which is the second straight pipe portion, so that the efficiency of the jet pump can be improved and vibration of the jet pump can be suppressed. it can.

It is a block diagram of a boiling water reactor. It is a block diagram of the jet pump of Example 1 which is one suitable Example of this invention shown in FIG. FIG. 3 is an enlarged longitudinal sectional view of an upper part of the jet pump shown in FIG. 2. It is the IV-IV arrow directional view of FIG.3 and FIG.14. It is VV sectional drawing of FIG.3 and FIG.14. FIG. 6 is an enlarged view of a VI part in FIG. 5. It is an enlarged view of the VII part of FIG. It is an enlarged view of the VIII part of FIG. It is a characteristic view which shows the change of the jet pump efficiency by the difference in the shape of the insertion pipe part of the throat of a jet pump. It is a characteristic view which shows the change of the fluctuation | variation pressure of the throat exit part by the difference in the shape of the insertion pipe part of the throat of a jet pump. It is a characteristic view which shows the change of the friction loss coefficient with respect to the depth of a triangular groove. It is a characteristic view which shows the relationship between the angle of the bottom part of a triangular groove, and the depth of a triangular groove. It is the characteristic view which showed the jet pump efficiency and pressure fluctuation of the jet pump shown in FIG. 3 in contrast with these of the conventional jet pump. It is a longitudinal cross-sectional view of the jet pump of Example 2 which is another Example of this invention. It is the characteristic view which showed the jet pump efficiency of the jet pump shown in FIG. 14 in contrast with this of the conventional jet pump.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Core, 3 ... Core shroud, 6 ... Downcomer, 9 ... Recirculation piping, 10 ... Recirculation pump, 13, 13A ... Jet pump, 14 ... Nozzle, 15 ... Bellmouth, 16 ... Throat, 16A ... first straight pipe part, 16B ... tapered pipe, 16C ... insertion pipe part, 17 ... diffuser, 18 ... nozzle holder, 19 ... slip joint part, 20A, 20B, 20C ... triangular groove, 31 ... cooling water 32 ... Drive water, 34 ... Jetted flow, 36 ... Driven water.

Claims (7)

A nozzle for ejecting a driving fluid, the driving fluid ejected from the nozzle, and a bell mouth, a throat and a diffuser in which a driven fluid sucked from the periphery of the nozzle flows,
The throat has a first straight pipe portion connected to the bell mouth and having an inner diameter smaller than an inner diameter at an open end of the bell mouth, and has an inner diameter larger than the inner diameter of the first straight pipe portion, and the diffuser A second straight pipe portion connected to the first straight pipe portion, and the first straight pipe portion and the second straight pipe portion, and from one end on the first straight pipe portion side to the other end on the second straight pipe portion side. have a coupling pipe portion whose inner diameter increases Te,
The second straight pipe portion is inserted into the upper end portion of the diffuser, and a step is formed between the inner surface of the second straight pipe portion and the inner surface of the diffuser at the lower end of the second straight pipe portion,
Jet pump, wherein that you have formed on the inner surface of the second straight pipe portion in the circumferential direction of a plurality of triangular grooves extending in the axial direction of the throat is the second straight pipe portion. 2. The jet according to claim 1, wherein the plurality of triangular grooves are formed substantially on an inner surface of the second straight pipe portion among an inner surface of the coupling pipe portion and an inner surface of the second straight pipe portion of the throat. pump. The jet pump according to claim 1 or 2, wherein the plurality of triangular grooves are formed on an inner surface of the bell mouth in a circumferential direction of the bell mouth. Jet pump according to claim 3 in which a plurality of the triangular groove is formed on the inner surface of the first straight pipe portion in the circumferential direction of the first straight pipe portion. When the angle of the bottom of the triangular groove is θ, the triangular groove depth h (mm) is
-1.5767 · lnθ + 8.1629 ≦ h ≦ claims 1 satisfies the 5.0mm to jet pump according to any one of 4. A depth h (mm) of the triangular groove is
The jet pump according to claim 5, satisfying −1.7219 · lnθ + 9.0299 ≦ h ≦ 5.0 mm. A reactor vessel, and a jet pump that is disposed in the reactor vessel and that supplies coolant to a core disposed in the reactor vessel;
A nuclear reactor, wherein the jet pump is the jet pump according to any one of claims 1 to 6.

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