JP2016080578A - Boiling-water reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiling water reactor capable of suppressing the pressure loss of a cooling water flow passage by the use of a flow velocity detector using a strain gauge and reducing manufacturing cost and management cost.SOLUTION: A boiling-water reactor comprises: a differential pressure detector 19 into which a reference pressure corresponding to a reference water level Hwithin a condensation tank 16 is introduced via a reference pressure duct 17, into which a water level pressure corresponding to a water level Hwithin a reactor pressure vessel 1 is introduced via a water level pressure duct 18, and which outputs a differential pressure between the reference pressure and the water level pressure; a water level arithmetic unit 20 which calculates the water level Hwithin the reactor pressure vessel 1 on the basis of a detection signal from the differential pressure detector 19; a flow velocity detector 21 having a metal pipe the strain amount of which changes with a flow velocity of cooling water and a strain gauge which detects the strain amount of the metal pipe; and a core flow volume arithmetic unit 22 which calculates a core flow volume on the basis of a signal from the strain gauge. The flow velocity detector 21 is inserted from an insertion port provided in the water level pressure duct 18.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a boiling water reactor, and more particularly to a boiling water reactor that measures a core flow rate using a flow velocity detector using a strain gauge.

  In a boiling water reactor, the cooling water is evaporated by the heat generated in the core in the reactor pressure vessel, the generated steam is supplied to the turbine, the turbine is rotated, and the generator is driven by the rotation of the turbine. At this time, a water level that is a boundary between cooling water and steam is formed above the core in the reactor pressure vessel. In addition, a steam separator and a steam dryer are installed on the upper side of the reactor core, and it is important to monitor whether or not the above-mentioned water level is appropriate in order to ensure the performance.

  The water level in the reactor pressure vessel is generally measured using a differential pressure type water level measuring device. This water level measuring device is, for example, a condensing tank connected to a gas phase part of a reactor pressure vessel through a pipe, a reference pressure conduit connected to the lower part of the condensing tank, and a liquid phase part of the reactor pressure vessel. The water level pressure conduit is connected, a reference pressure conduit, a differential pressure detector connected to the water level pressure conduit, and a water level calculator. The condensing tank forms a reference water level. The differential pressure detector introduces a reference pressure corresponding to the reference water level in the condensing tank via the reference pressure conduit, and introduces a water level pressure corresponding to the water level in the reactor pressure vessel via the water level pressure conduit, The differential pressure between the reference pressure and the water level pressure is detected. The water level calculation unit calculates the water level in the reactor pressure vessel based on the detection signal from the differential pressure detector.

  In a boiling water reactor, it is also important to monitor whether the flow rate of cooling water flowing into the core (hereinafter referred to as the core flow rate) is appropriate in order to stably maintain the core temperature, pressure, and the like. In addition, it is necessary to measure the core flow rate for power monitoring and thermal margin evaluation.

  In the forced circulation method, which is one of the cooling water circulation methods, the cooling water is fed into the core by a recirculation pump. In general, a method of measuring the core flow rate using a detector that detects a differential pressure before and after the recirculation pump is employed.

  In addition, a method for measuring the core flow rate using a flow velocity detector using a strain gauge has been proposed (see, for example, Patent Document 1).

JP 62-191729 A

  As a cooling water circulation system, a natural circulation system is known in addition to the above-described forced circulation system. In the natural circulation system, cooling water is fed into the core by a flow generated by a difference in density of cooling water inside and outside the core, that is, by a natural circulation flow. In order to increase the amount of heat extracted from the core, it is necessary to increase the core flow rate. Therefore, it is desirable to reduce the pressure loss in the cooling water flow path as much as possible.

  Therefore, it is conceivable to employ a method of measuring the core flow rate using a flow velocity detector using a strain gauge. This flow velocity detector can be easily miniaturized and can suppress the pressure loss of the cooling water channel.

  However, in order to place at least a part of the flow velocity detector in the cooling water channel in the reactor pressure vessel and output the flow velocity detector signal to the outside of the reactor pressure vessel, the inside and outside of the reactor pressure vessel are penetrated. A penetrating part is required. The reactor pressure vessel has a function of maintaining the state where the core is submerged. Therefore, if a through-hole is provided in the reactor pressure vessel itself, the manufacturing and management costs increase from the viewpoint of leakage prevention.

  An object of the present invention is to provide a boiling water reactor that can suppress a pressure loss of a cooling water flow path by using a flow velocity detector using a strain gauge and can reduce manufacturing and management costs. .

  In order to achieve the above object, the present invention provides a condensing tank that is connected to a gas phase portion of a reactor pressure vessel through a pipe to form a reference water level, a reference pressure conduit that is connected to a lower portion of the condensing tank, A water level pressure conduit connected to the liquid phase part of the reactor pressure vessel, a reference pressure corresponding to a reference water level in the condensing tank is introduced via the reference pressure conduit, and the water level pressure conduit Introducing a water level pressure corresponding to the water level in the reactor pressure vessel and detecting a differential pressure between the reference pressure and the water level pressure; and the atomic pressure based on a detection signal from the differential pressure detector. A water level calculation unit that calculates the water level in the reactor pressure vessel, and a strained body that is arranged so that at least a part thereof faces the cooling water flow path in the reactor pressure vessel and the amount of strain changes according to the flow rate of the cooling water And a strain gauge for detecting a strain amount of the strained body. And a core flow rate calculation unit that calculates a core flow rate based on a detection signal from the strain gauge, wherein the flow rate detector is connected to the water level pressure conduit. It is inserted from the provided through part.

  According to the present invention, since a small flow rate detector using a strain gauge is used, the pressure loss of the cooling water passage can be suppressed. In addition, at least part of the flow rate detector is placed in the cooling water flow path in the reactor pressure vessel, and the water level pressure conduit for water level measurement is passed through to output the flow rate detector signal to the outside of the reactor pressure vessel. Therefore, the manufacturing and management costs can be reduced as compared with the case where the through-hole is provided in the reactor pressure vessel itself.

It is a figure showing the structure of the boiling water reactor of the natural circulation system in the 1st Embodiment of this invention. It is the elements on larger scale of the II section in FIG. It is sectional drawing showing the internal structure of the flow velocity detector in the 1st Embodiment of this invention. It is sectional drawing showing the internal structure of the flow velocity detector in one modification of this invention. It is a figure showing the structure of the boiling water reactor of the natural circulation system in the 2nd Embodiment of this invention. It is sectional drawing by the cross section VI-VI in FIG.

  A first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of a natural circulation boiling water reactor in the present embodiment. FIG. 2 is a partially enlarged view of a part II in FIG. 1 and shows an installation structure of the flow velocity detector. FIG. 3A is a side sectional view showing the internal structure of the flow velocity detector in the present embodiment. 3B is a cross-sectional view taken along a section AA in FIG. 3A, and FIG. 3C is a cross-sectional view taken along a section BB in FIG. 3A. ) Is a sectional view taken along a section CC in FIG.

  The boiling water reactor includes a reactor pressure vessel 1. A shroud 2 is provided inside the reactor pressure vessel 1, and a core 3 and a chimney 4 are provided inside the shroud 2. A steam / water separator 5 is provided above the shroud 2, and a steam dryer 6 is provided above the steam / water separator 5.

  The core 3 is composed of a plurality of fuel assemblies (not shown) and is supported by a core support plate 7. A plurality of control rod drive mechanisms 8 (only one is shown for convenience in FIG. 1) are provided in the lower part of the reactor pressure vessel 1, and each control rod drive mechanism 8 inserts a control rod 9 between the fuel assemblies. It is possible. Then, by adjusting the neutron absorption amount of the fuel assembly by the control rod 9, the heat generation amount of the fuel assembly (that is, the output of the core 3) is controlled.

  The cooling water (coolant) in the shroud 2 is heated in the core 3 to be in a gas-liquid two-phase state, rises and passes through the chimney 4. The gas-liquid two-phase coolant that has passed through the chimney 4 is separated into steam and water by the steam separator 5. Water vapor is removed from the steam separated by the steam separator 5 by the steam dryer 6 and supplied to the turbine (not shown) via the main steam pipe 10. Thereby, a turbine rotates and a generator (not shown) drives.

  The steam discharged from the turbine is condensed into water by a condenser (not shown), and this water is supplied to the downcomer 12 (in other words, the reactor pressure vessel 1) in the reactor pressure vessel 1 through the water supply pipe 11. And a cooling water passage formed between the shroud 2 and the shroud 2. Note that the water separated by the steam separator 5 and the steam dryer 6 is also discharged to the downcomer 12 and merges with the water supplied from the water supply pipe 11.

  The density of cooling water in the downcomer 12 (in other words, outside the shroud 2) is larger than the density of cooling water in the core 2 and chimney 3 (in other words, inside the shroud 2). Therefore, a natural circulation flow is generated by the difference in density between them. That is, the cooling water in the downcomer 12 flows downward and flows into the core 2 from the core support plate 7.

Boiling water reactor, further measures a water level measuring device 13 which measures the water level H ₁ in the reactor pressure vessel 1, the core flow (i.e., flow rate of the cooling water flowing from the downcomer 12 to the core 3) core A flow rate measuring device 14 is provided.

  The water level measuring device 13 includes a condensing tank 16 connected to a gas phase part (in other words, a part where steam exists) of the reactor pressure vessel 1 via a pipe 15, and a reference pressure conduit connected to a lower part of the condensing tank 16. 17, a water level pressure pipe 18 connected to a liquid phase part (in other words, a part where cooling water exists) of the reactor pressure vessel 1, and a differential pressure detector connected to the reference pressure pipe 17 and the water level pressure pipe 18. 19 and a water level calculation unit 20.

Condensing tank 16 forms a reference water level _{H 0.} The differential pressure detector 19 introduces a reference pressure corresponding to the reference water level H ₀ in the condensing tank 16 through the reference pressure conduit 17 and introduces a water level pressure corresponding to the water level H ₁ in the reactor pressure vessel 1. The differential pressure between the reference pressure and the water level pressure is detected. The water level calculation unit 20 calculates the water level H ₁ in the reactor pressure vessel 1 based on the detection signal from the differential pressure detector 19.

  The core flow rate measuring device 14 includes a flow rate detector 21 that detects the flow rate of the cooling water in the downcomer 12 and a core flow rate calculation unit 22 that calculates the core flow rate based on the detection signal from the flow rate detector 21. Yes.

  The flow velocity detector 21 is made of, for example, a stainless steel deformable metal tube 23 (a strained body) and the tip side of the metal tube 23 (left side in FIG. 2, left side in FIGS. 3A and 3B). The strain gauge 24 housed in the metal tube 23 so as to be positioned at a position, a pair of lead wires 25 connected to the strain gauge 24, and the strain gauge 24 and the lead wire 25 are filled in the metal tube 23. And an insulator 26. The metal tube 23 has a tube structure having a bottom portion on the distal end side and an opening portion on the proximal end side (right side in FIG. 2). An adapter 27 is provided in the opening on the proximal end side of the metal tube 23, and the lead wire 25 and the cable 28 are connected via the adapter 27.

  Here, as a major feature of the present embodiment, an insertion port 29 (through portion) is provided in the water level pressure conduit 18 for measuring the water level, and the above-described flow velocity detector 21 is connected to the insertion port 29 of the water level pressure conduit 18. Has been inserted. More specifically, the guide tube 30 is inserted from the insertion port 29 of the water level pressure conduit 18 and fixed by the weld 31. The flow velocity detector 21 is inserted into the guide tube 30 and guided, and the distal end portion of the metal tube 23 protrudes from the opening on the distal end side (left side in FIG. 2) of the guide tube 30 so that the downcomer in the reactor pressure vessel 1 is inserted. 12 are arranged so as to face 12. A removable sealing member 32 (specifically, for example, an annular ferrule) is attached to the opening on the proximal end side (right side in FIG. 2) of the guide tube 30 so as to seal the cooling water. It has become.

  The metal tube 23 of the flow velocity detector 21 has a circular cross section (see FIG. 3 (d)) on the most part on the base end side, but the cross section of the distal end portion is flat (in other words, the vertical width dimension is The shape is smaller than the width dimension in the horizontal direction) (see FIG. 3C). Thereby, it becomes easy to receive the stress of the flow direction (downward) of the cooling water in the downcomer 12. The tip of the metal tube 23 has a taper structure as shown in FIGS. 2 and 3A.

  As with the metal tube 23 of the flow velocity detector 21, the guide tube 30 has a circular cross section at the most proximal side, but a flat cross section at the distal end. Further, as shown in FIG. 2, the distal end portion of the guide tube 30 has a tapered structure, and the taper angle α is the same as the distal end portion of the metal tube 23.

  The distal end portion of the metal tube 23 protruding from the opening on the distal end side of the guide tube 30 is deformed by receiving stress in the flow direction of the cooling water in the downcomer 12, and the amount of distortion changes according to the flow rate of the cooling water. To do. Since the strain gauge 24 is also deformed along with the deformation of the distal end portion of the metal tube 23, the resistance value of the strain gauge 24 changes according to the strain amount of the distal end portion of the metal tube 23. Therefore, the flow rate of the cooling water in the downcomer 12 is detected as the current value of the strain gauge 24, and the detection signal is output to the core flow rate calculation unit 22 via the lead wire 25, the adapter 27, and the cable 28. Yes.

  Although not shown, the core flow rate calculation unit 22 includes an analog-digital conversion unit and a storage unit. The analog / digital converter converts the detection signal (electric signal) input from the strain gauge 24 of the flow velocity detector 21 into the strain amount (digital value) of the metal tube 23 of the flow velocity detector 21. The storage unit stores a correlation equation between the strain amount of the metal pipe 23 of the flow velocity detector 21 and the flow velocity of the cooling water, which is created in advance by a test or analysis, and the flow velocity detector in the downcomer 12 that is created in advance by a test or analysis. Correlation data between the flow rate of the cooling water at the position 21 and the flow rate of the cooling water in the downcomer 12 is stored. The core flow rate calculation unit 22 then determines the position of the flow rate detector 21 in the downcomer 12 based on the strain amount of the metal tube 23 of the flow rate detector 21 converted by the analog-digital conversion unit and the correlation equation stored in the storage unit. Calculate the cooling water flow rate at. Further, the flow rate of the cooling water in the downcomer 12 (that is, the core flow rate) is calculated based on the calculated flow rate of the cooling water and the correlation data stored in the storage unit.

  In the present embodiment configured as described above, since the small flow velocity detector 21 using the strain gauge 24 is used, the pressure loss of the downcomer 12 can be suppressed. Therefore, the core flow rate can be increased, and the amount of heat extracted from the core 3 can be increased. Further, a water level pressure conduit for measuring the water level is provided so that the tip of the flow rate detector 21 is disposed on the downcomer 12 in the reactor pressure vessel 1 and the signal of the flow rate detector 21 is output to the outside of the reactor pressure vessel 1. Since the through portion (insertion port 29) is provided in 18, the cost of production and management (specifically, inspection, etc.) can be reduced as compared with the case where the through portion is provided in the reactor pressure vessel 1 itself.

  Moreover, in this embodiment, by providing the guide tube 30 and the sealing member 32, the flow velocity detector 21 can be easily removed when the flow velocity detector 21 needs to be replaced or repaired.

  Moreover, in this embodiment, the front-end | tip part of the metal tube 23 of the flow velocity detector 21 and the front-end | tip part of the guide tube 30 are made into a taper structure, and those taper angles (alpha) are made the same. Thereby, when the flow velocity detector 21 is fixed to the guide tube 30 by tightening the sealing member 32, the tip of the metal tube 23 and the tip of the guide tube 30 are in surface contact. Support strength can be increased. Further, the tip of the metal tube 23 in the downcomer 12 can be easily positioned.

  In the first embodiment, the case where the flow velocity detector 21 has the metal tube 23 as an example of the strained body has been described as an example. However, the present invention is not limited to this, and the scope and spirit of the present invention are not deviated. It can be deformed. FIG. 4A is a side sectional view showing the internal structure of the flow velocity detector 21 in a modification of the present invention. 4 (b) is a cross-sectional view taken along the line DD in FIG. 4 (a), and FIG. 4 (c) is a cross-sectional view taken along the line EE in FIG. 4 (a). ) Is a cross-sectional view taken along a cross-section FF in FIG. In this modification, as the strained body of the flow velocity detector 21, the double-structured metal tubes 23A and 23B are provided. Thereby, even if only the outer metal tube 23A is broken, the measurement of the core flow rate can be continued.

  Next, a second embodiment of the present invention will be described with reference to FIGS.

  FIG. 5 is a diagram showing a configuration of a natural circulation boiling water reactor in the present embodiment. FIG. 6 is a sectional view taken along section VI-VI in FIG. 5 and shows the arrangement of the flow velocity detectors. In addition, in this embodiment, the part equivalent to the said 1st Embodiment attaches | subjects the same code | symbol, and abbreviate | omits description suitably.

  In the present embodiment, four (only two are shown for convenience in FIG. 5) water level measuring devices 13 are provided so as to correspond to the four circumferential positions of the reactor pressure vessel 1, respectively. That is, four water level pressure conduits 18 are provided so as to correspond to the four locations in the circumferential direction of the reactor pressure vessel 1 (see FIG. 6).

  The four water level pressure conduits 18 are respectively provided with insertion ports 29 (see FIG. 2 described above), and four guide tubes 30 are inserted and fixed from the corresponding insertion ports 29, respectively. The four flow velocity detectors 21 are inserted into the corresponding guide tubes 30 and guided, and the distal end portion of the metal tube 23 protrudes from the opening on the distal end side of the guide tube 30 to the downcomer 12 in the reactor pressure vessel 1. It is arranged to face. A removable sealing member 32 (see FIG. 2 described above) is attached to the opening on the proximal end side of each guide tube 30.

  Although not shown, the core flow rate calculation unit 22A has an analog-digital conversion unit and a storage unit. The analog-digital converter converts the detection signal (electric signal) input from the strain gauge 24 of each flow rate detector 21 into the strain amount (digital value) of the metal tube 23 of each flow rate detector 21. The storage unit stores a correlation equation between the strain amount of the metal tube 23 of the flow velocity detector 21 and the flow velocity of the cooling water, which has been created in advance by a test or analysis, and the cooling water in the downcomer 12 that has been created in advance by a test or analysis. Correlation data between the flow velocity distribution and the flow rate of the cooling water in the downcomer 12 is stored. Then, the core flow rate calculation unit 22 is based on the strain amount of the metal tube 23 of each flow velocity detector 21 converted by the analog-digital conversion unit and the correlation equation stored in the storage unit, and each flow velocity detector 21 in the downcomer 12. The flow rate of the cooling water at the position is calculated. Further, out of the cooling water flow velocity distribution in the downcomer 12 stored in the storage unit, the flow velocity distribution closest to the cooling water flow velocity at the position of the four flow velocity detectors 21 is extracted, and the extracted flow velocity distribution and correlation data are extracted. Based on the above, the flow rate of the cooling water in the downcomer 12 (that is, the core flow rate) is calculated.

  In the present embodiment configured as described above, similarly to the first embodiment, the pressure loss of the downcomer 12 can be suppressed by using the flow velocity detector 21 using the strain gauge 24, and the manufacturing can be performed. Management costs can be reduced. Moreover, in this embodiment, since the several flow velocity detector 21 is provided and a core flow rate is calculated based on those detection signals, the precision of a core flow rate can be improved.

  In the first and second embodiments, the case where the distal end portion of the metal tube 23 and the distal end portion of the guide tube 30 of the flow velocity detector 21 have a taper structure has been described as an example. Modifications can be made without departing from the spirit and technical idea of the present invention. That is, the tip of the metal tube 23 and the tip of the guide tube 30 of the flow velocity detector 21 do not have to have a tapered structure.

  In the first and second embodiments, the case where the guide tube 30 and the sealing member 32 are provided has been described as an example. However, the present invention is not limited to this, and the scope and spirit of the present invention are not deviated. It can be deformed. That is, without providing the guide tube 30 and the sealing member 32, for example, the flow velocity detector 21 may be directly inserted from the insertion port 29 of the water level pressure conduit 18 and fixed by the welded portion.

  In the above description, a natural circulation boiling water reactor has been described as a preferred application target of the present invention. However, the present invention is not limited to this, and may be applied to a forced circulation boiling water reactor. .

1 Reactor pressure vessel 12 Downcomer (cooling water flow path)
DESCRIPTION OF SYMBOLS 15 Piping 16 Condensing tank 17 Reference | standard pressure conduit 18 Water level pressure conduit 19 Differential pressure detector 20 Water level calculating part 21 Flow velocity detector 22, 22A Core flow rate calculating part 23, 23A, 23B Metal pipe (distorted body)
24 Strain gauge 26 Insulator 29 Insertion slot (through)
30 Guide tube 32 Sealing member

Claims (4)

A condensing tank connected to the gas phase part of the reactor pressure vessel via a pipe to form a reference water level;
A reference pressure conduit connected to the bottom of the condensing tank;
A water level pressure conduit connected to the liquid phase of the reactor pressure vessel;
A reference pressure corresponding to a reference water level in the condensing tank is introduced via the reference pressure conduit, and a water level pressure corresponding to a water level in the reactor pressure vessel is introduced via the water level pressure conduit, and the reference A differential pressure detector for detecting a differential pressure between the pressure and the water level pressure;
A water level calculator that calculates the water level in the reactor pressure vessel based on a detection signal from the differential pressure detector;
A strained body that is arranged so that at least a part thereof faces the cooling water flow path in the reactor pressure vessel and changes the strain amount according to the flow rate of the cooling water, and a strain gauge that detects the strain amount of the strained body A flow rate detector having:
A core flow rate calculation unit for calculating a core flow rate based on a detection signal from the strain gauge, and a boiling water reactor comprising:
The boiling water reactor is characterized in that the flow velocity detector is inserted from a through portion provided in the water level pressure conduit. The boiling water reactor according to claim 1,
A guide tube inserted and fixed from the penetrating portion of the water level pressure conduit;
A sealing member removably attached to the opening on the proximal end side of the guide tube;
The flow velocity detector is inserted into the guide tube and guided so that at least a part of the strained body protrudes from the opening on the distal end side of the guide tube and faces the cooling flow path in the reactor pressure vessel. Boiling water reactor characterized by being arranged. The boiling water reactor according to claim 2,
The strained body is a tubular structure having a bottom portion on the tip side, and at least the tip portion has a flat cross-sectional shape,
The boiling water nuclear reactor characterized in that the strain gauge is housed in the strained body so as to be positioned at a tip portion of the strained body, and an insulator is filled around the strain gauge. The boiling water reactor according to claim 3,
The boiling water reactor according to claim 1, wherein the distal end portion of the strained body and the distal end portion of the guide tube have a tapered structure and have the same taper angle.

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