JP5415701B2 - Reactor jet pump - Google Patents

Description

  The present invention relates to a nuclear reactor jet pump for circulating a coolant of a boiling water reactor.

  FIG. 5 is a cross-sectional view showing a schematic configuration of a boiling water nuclear reactor generally used conventionally as described in Patent Document 1 and the like. As shown in FIG. 5, the reactor pressure vessel 10 accommodates a core 11 composed of a plurality of fuel assemblies. In addition to the core 11, the reactor pressure vessel 10 contains a coolant 12 for cooling it.

  A steam / water separator 13 is disposed above the core 11, and a steam dryer 14 is disposed above the steam / water separator 13. The coolant 12 flows from the bottom to the top of the core 11 and is heated by the nuclear reaction heat of the core 11 to be in a two-phase mixed state of water and steam. Then, the coolant 12 in the two-phase mixed state in this way flows into the steam separator 13 and is separated into water and steam in the steam separator 13. The steam thus separated is dried by a steam dryer 14 to become dry steam, which is supplied to a turbine system (not shown) via a main steam pipe 20 connected to the upper part of the reactor pressure vessel 10, while water is a core. 11 flows into the lower coolant chamber 16 through the downcomer portion 15 formed around the periphery of the reactor 11, and flows again from the lower side of the core 11 to the upper side.

  Further, the reactor pressure vessel 10 is provided with a recirculation system 60 for recirculating the coolant 12 of the downcomer portion 15 to the core 11. The recirculation system 60 is constituted by a recirculation pipe 50 that connects the recirculation pump 30 and the jet pump 40 in addition to the recirculation pump 30 and the jet pump 40. A plurality of jet pumps 40 of the recirculation system 60 are provided in the downcomer portion 15 so as to surround the core 11, and a plurality of recirculation pumps 30 and recirculation pipes 50 are provided corresponding to the jet pumps 40. Yes.

  6 is an arrow view of the jet pump 40 of the recirculation system 60 as seen from the direction of arrow A in FIG. As shown in FIG. 6, the jet pump 40 includes a circular supply pipe 41 connected to the discharge port of the recirculation pump 30 and supplied with the coolant 12 from the recirculation pump 30. The downstream portion of the supply pipe 41 is bifurcated, and a nozzle 42 having a circular opening is formed at each of the branched downstream ends. Further, a substantially circular introduction pipe 43 for introducing the coolant 12 ejected from the nozzle 42 into the lower coolant chamber 16 is provided below the nozzle 42.

  The introduction pipe 43 is connected to the bell mouth 431 into which the coolant 12 ejected from the nozzle 42 flows, the throat 432 connected to the downstream end of the bell mouth 431, and the downstream end of the throat 432. A diffuser 433 is used. The bell mouth 431 has an opening area larger than that of the nozzle 42 b of the nozzle 42. The nozzle 42 is supported by the bell mouth 431 by the plurality of support members 42 a, so that the center of the ejection port 42 b of the nozzle 42 and the opening center of the bell mouth 431 are maintained to coincide with each other.

  Further, the bell mouth 431 has a shape in which the channel cross-sectional area is set to be smaller toward the downstream side of the bell mouth 431, and the flow direction of the coolant 12 flowing from the nozzle 42 is gradually changed to change it to the throat 432. Introduce. The throat 432 has a straight tube shape in which the flow passage cross-sectional area of the portion from the bell mouth 431 to the diffuser 433 is set to be constant, and introduces the coolant 12 flowing from the bell mouth 431 into the diffuser 433. On the other hand, in the diffuser 433, the flow passage cross-sectional area is set gradually larger from the upstream portion to the downstream portion, and the flow cross-sectional area is set constant in the most downstream portion connected to the lower coolant chamber 16. ing. The coolant 12 flowing into the diffuser 433 through the bell mouth 431 and the throat 432 is gradually recovered in pressure and introduced into the lower coolant chamber 16.

Further, when the coolant 12 is ejected from the nozzle 42 to the bell mouth 431, the coolant 12 of the downcomer portion 15 existing around the bell mouth 431 is entrained by the coolant 12 ejected from the nozzle 42 and is brought into the bell mouth 431. Inflow. Here, when the amount of the coolant 12 ejected from the nozzle 42 is “Qn”, and the amount of the coolant 12 that is caught by the coolant 12 and flows into the bell mouth 431 is “Qs”, the ratio of these flow rates (Qs / Qn) is generally called an M ratio, and is used as an index for evaluating the characteristics of the jet pump 40.
JP-A-2005-233152

  By the way, the amount of power consumed in the recirculation system accounts for several percent of the total power generation at the nuclear power plant. To increase the power generation efficiency of the nuclear power plant, the power consumption of this recirculation system is minimized. It is requested to do. In this respect, it is most effective to increase the efficiency of the jet pump by increasing the M ratio described above. Specifically, the normal jet pump set to "1.0 to 1.5" It is considered desirable to employ a high flow ratio type jet pump in which the M ratio is increased to “2.0” or higher.

  In general, however, the efficiency of the jet pump once improves as the M ratio is increased from about “0.8”. However, when the M ratio reaches an area of about “1.5” or more, the efficiency of the jet pump gradually increases. It begins to decline. This is because the flow rate of the coolant in the throat increases due to the increase in the M ratio, the static pressure inside the throat decreases, and the coolant pressure flows into the diffuser without fully recovering. It is estimated that.

  The present invention has been made on the basis of such a conventional situation, and an object of the present invention is a nuclear reactor jet pump that operates in a region of a relatively high flow rate ratio (M ratio). The purpose of this is to improve the pump efficiency by quickly recovering the pressure of the coolant flowing into the tank.

  In order to achieve such an object, according to the first aspect of the present invention, the coolant discharged from the recirculation pump is ejected from a nozzle having a plurality of nozzles, and flows into the bell mouth while enclosing the surrounding coolant. In the nuclear reactor jet pump that discharges the coolant to the diffuser through the throat, the throat has at least the inner wall of the most upstream side portion connected to the bell mouth inclined with respect to the axis of the throat, and the downstream side thereof It has a tapered shape that expands in diameter.

  According to this configuration, since the inner wall of the most upstream part following the bell mouth is tapered, the reactor is provided with a nozzle having a plurality of nozzles and operated in a relatively high flow ratio (M ratio) region. Even in the jet pump, the pressure of the coolant flowing into the throat from the bell mouth can be recovered quickly, and the pump efficiency can be improved.

In the first aspect of the present invention, the throat is connected to the first taper pipe including the most upstream portion thereof and the downstream side of the first taper pipe, and the inclination angle of the inner wall with respect to the axis is the first throat. second and a tapered pipe, such adopts a configuration that is set larger than the tapered tube.

Furthermore, in the invention according to claim 1, as before Symbol connection between the first tapered pipe and the second tapered pipe is the inclined angle is an inner wall is formed so as to continuously vary Yes.

  According to this configuration, when the coolant flows through the connection portion of the first taper pipe and the second taper pipe, the flow direction gradually changes along the inner wall. It is possible to suppress the occurrence of turbulence, and to suppress the pressure recovery of the coolant from being restricted due to the occurrence of the turbulent flow.

Further, the nozzle nozzle holes can be arranged at equiangular intervals around the coaxial line with the axis of the throat as the center, specifically as in the invention described in claim 2. As in the third aspect of the present invention, this can be set to five.

  According to the present invention, since the inner wall of the most upstream part following the bell mouth is tapered, even in a nuclear reactor jet pump that includes a nozzle having a plurality of nozzles and operates in a region with a relatively high flow ratio M. The coolant that has flowed into the throat from the bell mouth can be quickly recovered in pressure, and the pump efficiency can be improved.

  Embodiments of a nuclear reactor jet pump according to the present invention will be described below. The reactor jet pump in this embodiment is different in the shape of the nozzle and the throat, but the other shapes are the same as those shown in FIGS. 5 and 6, and the configuration relating to the boiling water reactor Since the same applies to, the explanation is omitted.

  FIG. 1 is a partial sectional view of a jet pump 40 according to this embodiment. As described above, the supply pipe 41 of the jet pump 40 has a shape in which the downstream portion is bifurcated, and the nozzles 42 are formed at the branched downstream ends. Only one nozzle 42 and the introduction pipe 43 for introducing the coolant 12 ejected from the nozzle 42 into the lower coolant chamber 16 are shown. The configuration of the other nozzle 42 and the introduction pipe 43 is the same, and the description thereof is omitted.

  As shown in FIG. 1, the throat 434 connected to the bell mouth 431 of the introduction pipe 43 is connected to the first taper pipe 434a including the most upstream portion thereof and to the downstream side of the first taper pipe 434a. The second tapered tube 434b. The first tapered tube 434a has an upstream portion connected to the bell mouth 431, and an inner wall inclined at a predetermined angle θ1 with respect to the axis C of the throat 434 (shown by a dashed line in FIG. 1). The side has a taper shape whose diameter is expanded. On the other hand, the second tapered tube 434b has a tapered shape in which the inner wall is inclined by a predetermined angle θ2 with respect to the axis C of the throat 434 and the diameter of the downstream side is increased. Here, the inclination angle θ2 of the second tapered tube 434b is set larger than the inclination angle θ1 of the first tapered tube 434a. Specifically, the inclination angles θ1 and θ2 are set such that the inclination angle θ1 is “0.644 °” and the inclination angle θ2 is “1.469 °”, respectively.

  FIG. 2 is a partially enlarged cross-sectional view showing an enlarged connection portion (part B in FIG. 1) between the first tapered tube 434a and the second tapered tube 434b. As shown in FIG. 2, the first taper tube 434a and the second taper tube 434b have shapes of connecting portions so that the inclination angles of the inner walls continuously increase from a predetermined angle θ1 to a predetermined angle θ2. Is set. Accordingly, when the coolant 12 flows from the first tapered tube 434a into the second tapered tube 434b, the flow direction of the coolant 12 in the vicinity of the inner wall gradually changes along the inner wall. For this reason, generation | occurrence | production of the turbulent flow and vortex | eddy_current of the coolant 12 in the vicinity of the connection part of each taper tube 434a, 434b will be suppressed.

  3 is a cross-sectional view taken along the line AA in FIG. As shown in FIG. 1 and FIG. 3, the nozzle 42 has a downstream portion branched into five, and these branched portions have five ejection portions 42d whose flow path cross-sectional area is set smaller toward the downstream side. Is configured. Further, at the downstream end portion of each ejection portion 42d, an ejection port 42c is formed that is located at equiangular intervals around the coaxial line with the axis C of the throat 434 as the center. The coolant 12 pumped from the recirculation pump 30 of the recirculation system 60 to the supply pipe 41 is ejected from the nozzles 42 c of the nozzle 42 to the bell mouth 431 while enclosing the surrounding coolant 12.

  FIG. 4 is a graph showing the pump efficiency of the jet pump 40 according to this embodiment. In FIG. 4, the plot point indicated by “◯” indicates the pump efficiency of the jet pump 40 when the flow rate ratio (M ratio) is changed in the range of “1.5 to 2.2”. As a comparative example, the plot points indicated by “” indicate the pump efficiency of the conventional jet pump in which the throat 432 connected to the bell mouth 431 has a straight tube shape as shown in FIG. As shown in FIG. 4, the jet pump according to the comparative example shows a relatively high pump efficiency when the M ratio is near “1.5”, but the pump efficiency gradually decreases as the M ratio increases. . On the other hand, in the jet pump 40 according to the present embodiment, even when the M ratio is increased, the pump efficiency is slightly reduced, and a high pump efficiency is maintained as compared with the comparative example. This is because the inner wall of the most upstream side portion of the throat 434 connected to the bell mouth 431, that is, the inner wall of the first taper tube 434a is inclined with respect to the axis C of the throat 434, and the diameter of the downstream side is increased. Therefore, it is estimated that the pressure of the coolant 12 that has flowed into the throat 434 from the bell mouth 431 can be recovered quickly. As described above, the jet pump 40 according to the present embodiment is operated with high pump efficiency even in a high M ratio region where the M ratio is increased to “2.0” or more as compared with the conventional jet pump. Can do.

As described above, according to the jet pump 40 according to the present embodiment, the following operational effects can be achieved.
(1) Even in the jet pump 40 operated in a relatively high flow rate ratio (M ratio) region of “2.0” or higher, the coolant 12 that has flowed into the throat 434 from the bell mouth 431 is quickly pressurized. It can be recovered and the pump efficiency can be improved.

  (2) Further, the inclination angle of the inner wall of the connecting portion of the first taper tube 434a and the second taper tube 434b is continuously increased from the predetermined angle θ1 to the predetermined angle θ2. For this reason, when the coolant 12 flows from the first taper tube 434a into the second taper tube 434b, the coolant 12 near the inner wall gradually changes its flow direction along the inner wall, and each taper. Generation of turbulent flow and vortex flow of the coolant 12 in the vicinity of the connection portion between the pipes 434a and 434b can be suppressed, and as a result, further improvement in pump efficiency can be achieved.

In addition to the above-described embodiment, the present invention can also be implemented in the following forms that are appropriately modified.
The inclination angle θ1 of the first taper tube 434a is set to “0.644 °” and the inclination angle θ2 of the second taper tube 434b is set to “1.469 °” with respect to the axis C of the throat 434. Can be appropriately changed within a range satisfying the relationship of (θ1 <θ2). Specifically, the inclination angle θ1 of the first taper tube 434a is in the range of “0.400 to 0.900 °”, and the inclination angle θ1 of the second taper tube 434b is “1.002”. It can be changed within the range of “.000 °”.

  The throat 434 is constituted by the first taper tube 434a and the second taper tube 434b, and the inclination angle of the inner wall thereof is changed in two stages, but at least the most upstream side portion connected to the bell mouth 431 is If it is a taper shape, the inclination angle may be constant or may be changed in three or more stages. Furthermore, the inclination angle may be continuously increased from the bell mouth 431 to the diffuser 433. In addition, a configuration in which a straight pipe portion whose inner wall extends in parallel with the axis C of the throat 434 may be employed in an intermediate portion of the throat 434.

  -Although the five nozzle holes 42c were formed in the nozzle 42, the nozzle 42 which has 2-4 nozzle holes 42c or six or more nozzle holes can also be employ | adopted.

The fragmentary sectional view of a jet pump. The partial expanded sectional view which expands and shows the part B of FIG. Sectional drawing along the AA line of FIG. The graph which shows the relationship between the pump efficiency of a jet pump, and a flow rate ratio. A partial cross-sectional view of a boiling water reactor. The fragmentary sectional view of the conventional general jet pump.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Reactor pressure vessel, 11 ... Core, 12 ... Coolant, 13 ... Steam separator, 14 ... Steam dryer, 15 ... Downcomer part, 16 ... Lower coolant chamber, 20 ... Main steam pipe, 30 ... Re Circulation pump, 40 ... jet pump, 41 ... supply pipe, 42 ... nozzle, 42a ... support member, 42b ... jet port, 42c ... jet port, 42d ... jet part, 43 ... introduction pipe, 431 ... bell mouth, 432 ... throat, 433 ... Diffuser, 434 ... Throat, 434a ... First taper tube, 434b ... Second taper tube, 50 ... Recirculation piping, 60 ... Recirculation system.

Claims (3)

Reactor jet pump that discharges coolant discharged from a recirculation pump from a nozzle having a plurality of nozzles and flows the coolant into a bell mouth while enclosing the surrounding coolant and discharges the coolant to a diffuser through a throat In
The throat has a tapered shape in which at least the inner wall of the most upstream side portion connected to the bell mouth is inclined with respect to the axis of the throat and the downstream side thereof is expanded in diameter .
The throat has a first taper tube including the most upstream portion thereof and a second taper connected to a downstream side of the first taper tube, and an inclination angle of an inner wall with respect to the axis is set larger than that of the first taper tube. Including a taper tube,
The reactor jet pump according to claim 1, wherein an inner wall of the connecting portion between the first tapered tube and the second tapered tube is formed so that the inclination angle changes continuously . In the nuclear reactor jet pump according to claim 1 ,
The plurality of nozzle holes are arranged at equiangular intervals around a coaxial line with the axis of the throat as a center. The nuclear reactor jet pump according to claim 2 ,
Five jet nozzles are arranged around the coaxial line. A nuclear reactor jet pump.

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