JP4080641B2 - Reactor pump seal device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a jet pump provided in a reactor pressure vessel of a boiling water reactor (hereinafter referred to as BWR), and more particularly to a sealing device for a reactor pump used for preventive maintenance of a jet pump riser pipe.
[0002]
[Prior art]
Conventionally, the BWR employs a so-called jet pump system in which a recirculation pump installed outside the reactor pressure vessel and a jet pump provided inside the reactor pressure vessel are combined in order to increase the power density. Hereinafter, a BWR jet pump employing this jet pump system will be described.
[0003]
A conventional example will be described with reference to FIGS. FIG. 5 is a longitudinal sectional view showing a schematic configuration of the BWR. As shown in FIG. 5, a reactor pressure vessel 1 contains a coolant 2 and a core 3. The core 3 is composed of a plurality of fuel assemblies and control rods (not shown). Is housed in.
[0004]
The coolant 2 flows upward through the core 3, and at that time, the coolant 2 is heated by the nuclear reaction heat of the core 3 and becomes a two-phase flow state of water and steam. The coolant 2 in the two-phase flow state flows into a steam / water separator 4 installed above the core 3 where it is separated into water and steam. Among these, the steam is introduced into a steam dryer 5 installed above the steam separator 4 and becomes dry steam.
[0005]
The dry steam is transferred to a steam turbine (not shown) via a main steam pipe 6 connected to the reactor pressure vessel 1 and is used for power generation. On the other hand, the separated water flows through the downcomer portion 7 between the core 3 and the reactor pressure vessel 1 and flows down below the core 3. A control rod guide tube 8 is installed below the core 3, and the control rod is inserted into or extracted from the core 3 through the control rod guide tube 8. A control rod drive mechanism 9 is installed below the control rod guide tube 8, and the control rod drive mechanism 9 controls the insertion and withdrawal of the control rod from the core 3.
[0006]
A plurality of jet pumps 11 are installed in the downcomer portion 7 at equal intervals in the circumferential direction, and a recirculation pump (not shown) is installed outside the reactor pressure vessel 1. A recirculation system is configured by the jet pump 11 and the recirculation pipe disposed between the two. Then, driving water is supplied to the jet pump 11 by the recirculation pump, and the coolant 2 is forcedly circulated in the core 3 by the action of the jet pump 11.
[0007]
The jet pump 11 has a riser pipe 12 as shown in enlarged views in FIGS. 6 and 7, and this riser pipe 12 is fixed to the inner surface of the reactor pressure vessel 1 via a riser brace. The coolant 2 supplied from the recirculation inlet nozzle 13 of the recirculation pump is introduced into the furnace. A pair of elbows 15 (15a, 15b) is connected to the upper portion of the riser pipe 12 via a transition piece 14.
[0008]
An inlet throat 17 (17a, 17b) is connected to each of these elbows 15a, 15b via a pair of mixing nozzles 16 (16a, 16b). Diffusers 18 (18a, 18b) are respectively connected below the pair of inlet throats 17a, 17b.
[0009]
Then, the coolant 2 is injected by the mixing nozzles 16a and 16b, and at that time, the reactor water is entrained from the surroundings, and the injected coolant 2 and the entrained water are mixed in the inlet throats 17a and 17b, respectively. . Thereafter, the hydrostatic head is recovered by the diffusers 18a and 18b.
[0010]
By the way, in said structure, fluid vibration generate | occur | produces with the flow of the coolant sent from a recirculation pump. In order to cope with this fluid vibration, the lower end of the riser pipe 12 is welded to the recirculation inlet nozzle 13 as described above, and the upper end is fixed to the reactor pressure vessel 1 via the riser brace 20.
[0011]
The inlet throats 17a and 17b are mechanically connected at their upper ends to the transition piece 14 via mixing nozzles 16a and 16b and elbows 15a and 15b, and their lower ends are inserted into the upper ends of the diffusers 18a and 18b. . As described above, both the riser pipe 12 and the inlet throats 17a and 17b are configured to sufficiently cope with fluid vibration.
[0012]
Next, the configuration above the mixing nozzles 16a and 16b will be described. A pair of ears 21 are formed on both sides of the transition piece 14, respectively, and these ears 21 protrude upward, and the inner side of the upper end thereof. A groove portion 22 is formed in the upper portion. A pair of jet pump beams 23 having a rectangular cross section that increases along the central portion in the length direction are fixed to the groove 22 by fitting both ends into the groove 22.
[0013]
A screw hole (not shown) is formed in the center of the jet pump beam 23 in the vertical direction, and a head bolt 24 is screwed into the screw hole. A hexagonal head is formed at the upper end of the head bolt 24, and a semi-round head is formed at the lower end. On the other hand, the elbows 15a and 15b are formed with a pedestal (not shown) having a horizontal upper end surface, and a counterbore (not shown) is formed on the pedestal. The semi-round head of the head bolt 24 is fitted into the counterbore through a spherical washer.
[0014]
Since the inlet throats 17a and 17b are not fixed to the reactor pressure vessel 1, the inflow water pressure of the driving water supplied via the riser pipe 12 acts on the upper end portions and the elbows 15a and 15b.
[0015]
Further, a reaction force such as an ejection pressure of driving water ejected from a nozzle (not shown) connected to the other ends of the elbows 15a and 15b into the diffusers 18a and 18b acts upward. A head bolt 24 is screwed into the jet pump beam 23 to face this load.
[0016]
Since the ear 21 is fixed at a fixed position, when the head bolt 24 is screwed, the jet pump beam 23 is moved upward, and both ends thereof are in contact with the upper wall surface of the groove 22. It becomes a state. As a result, an upward load is received.
[0017]
On the contrary, a downward load is applied to the upper ends of the elbows 15a and 15b via the head bolt 24, and the magnitude thereof is determined in relation to the upward load due to the reaction force of the driving water. A keeper (not shown) is detachably fitted to the hexagon head of the head bolt 24. This keeper is fixed to a support plate (not shown) by spot welding. This support plate has a rectangular shape and is fixed to the upper surface of the jet pump beam 23 by two bolts.
[0018]
The inlet throats 17 a and 17 b are attached to a riser blanket 25 fixed to the riser pipe 12. The diffusers 18 a and 18 b are fixed to a shroud support (baffle plate) 26 welded to the reactor pressure vessel 1.
[0019]
The jet pump 11 is used under harsh conditions compared to other equipment to circulate coolant. Therefore, a large load acts on each member, and severe stress acts particularly on the riser brace 20 that supports the riser pipe 12 in the middle thereof.
[0020]
The riser brace 20 controls the fluid vibration during the operation of the reactor generated in the riser pipe 12, and the thermal expansion difference between the reactor pressure vessel 1 made of carbon steel and the riser pipe 12 made of austenitic stainless steel. Absorbs. Therefore, during the operation of the nuclear reactor, the reactor is in a deformed state while absorbing the above thermal expansion difference.
[0021]
By the way, it is important to measure the flow rate of the jet pump during normal operation when controlling the output of the nuclear power plant. For this reason, measurement pipes 19 are provided above and below the diffusers 18a and 18b, and The difference in static pressure between the upper and lower parts of the diffuser 18 is measured, and the jet pump flow rate is calculated from the measured value and the calibration value measured before using the plant.
[0022]
This measurement pipe 19 is welded to the upper and lower holes of the diffuser 18, welded and supported by a support 27 fixed to the diffuser 18, and further arranged in a complicated state at the lower part of the jet pump 11. It is connected with the piping outside the furnace via.
[0023]
Two jet pump measurement nozzles are provided at the target position in the reactor pressure vessel 1. The jet pump 11 having such a configuration is used under severe conditions compared to other devices due to the flow of the coolant fed from the recirculation pump. For this reason, a large load acts on each member, and it receives influence of fluid vibration, and severe stress acts on it, Therefore It is fully anticipated that a pipe fracture will occur.
[0024]
[Problems to be solved by the invention]
By the way, in the above configuration, for example, when a crack or breakage occurs for some reason in the main body or welded portion of the jet pump system, the repair work needs to be performed remotely from directly above the core, which is a high radiation control area. Therefore, it is very difficult to approach the piping part.
[0025]
As a means for repairing the damaged jet pump 11 as described above, it is conceivable to perform welding. However, since the repair work is generally performed underwater, a large-scale repair device is required, and a long period of time is required. There is a problem that will be construction.
[0026]
In addition, if these works are left unattended, there is a possibility that the jet pump 11 will progress further and cracks may occur, and that the jet pump 11 that controls the output of the nuclear reactor will be in such a state, It may be possible to affect other structures, and there is a problem that it is not preferable.
[0027]
The present invention has been made to solve the above-described problems. When a crack occurs in a riser pipe of a jet pump, the nuclear power plant can be operated without replacing the shroud or a part of the shroud. To provide a sealing device for a pump.
[0028]
[Means for Solving the Problems]
The invention according to claim 1 lands on the opening of the transition piece connected to the upper part of the riser pipe of the jet pump installed in the downcomer between the reactor pressure vessel and the core, and seals the opening in a watertight manner. A sealing member, a base plate having the sealing member attached to the lower surface, a top plate having a convex portion that fits into a concave portion formed in the transition piece, one attached to the base plate and the other being the top plate And a stud attached to the reactor, wherein the seal member is pressed against the opening of the transition piece by rotating the stud .
[0029]
According to the first aspect of the present invention, the jet pump riser pipe is removably incorporated into the upper opening of the riser pipe after the inlet mixer of the jet pump provided in the reactor pressure vessel of the boiling water reactor is removed. As a sealing means for sealing, a mechanical tightening method that does not require a driving source can be reliably inspected and repaired in a short time.
[0030]
The invention of claim 2, wherein the sealing member has a characteristic that it has a flat seal for sealing the upper surface of continuously arranged in a tapered seal the tapered surface for sealing the tapered surface formed in the opening of the transition piece To do. According to the second aspect of the present invention, the sealing method is performed at two locations on the tapered surface of the riser tube upper opening and the upper surface of the riser tube. Further, the seal member has a separable structure, and only the seal portion is replaceable.
[0031]
The invention of claim 3 is characterized in that a foldable handle is attached to the top plate. According to the present invention, the handle portion has a handle portion that can be lifted by the gripping device, and the handle portion is inclined from the vertical state to the oblique state when the riser pipe sealing device is seated at a predetermined position, and is provided on the lower side of the handle. The structure is engageable with the head of the tightening screw.
[0032]
The invention of claim 4 is characterized in that a vent mechanism having a valve seal is provided on the base plate. According to the present invention, an air vent is incorporated in the upper part of the sealing device, and a mechanical air vent is incorporated so that the inside of the riser tube is not evacuated when the riser tube sealing device is removed.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of a sealing device for a reactor pump according to the present invention will be described with reference to FIGS. 1 to 3A and 3B.
In the present embodiment, the reactor internal pump is installed between the reactor pressure vessel and the shroud to forcibly circulate the reactor coolant. A riser pipe connected to the recirculation inlet nozzle, and a riser pipe The jet pump is composed of an inlet mixer made of an elbow provided on the upper end of each of the two, an inlet throat provided to the inlet mixer via a mixing nozzle, and a diffuser connected to the inlet throat.
[0034]
The reactor pump sealing device according to the present embodiment is detachably incorporated in the opening of the transition piece above the riser pipe after removing the jet pump inlet mixer, and seals the riser pipe.
[0035]
1 is an elevational view showing a partial cross section of a sealing device 30 according to the present embodiment, FIG. 2 is a plan view of FIG. 1, FIG. 3A is an enlarged view of a handle portion in FIG. 1, and FIG. ) Is a side view of FIG.
[0036]
1 and 2, reference numeral 31 denotes a seal member. The seal member 31 includes a taper portion seal 31 a and a flat portion seal 31 b, and the taper portion seal 31 a is formed on the inner surface of the opening of the transition piece 14. The flat surface seal 31b is sealed in watertight contact with the upper surface of the opening of the transition piece 14.
[0037]
The seal member 31 is fastened and fixed to the lower surface of the base plate 33 by mounting bolts 32 from above. The base plate 33 includes an upper plate 33a and a lower plate 33b, and the seal member 31 is attached to the lower plate 33b. A presser 35 for fixing the stud 34 is screwed to the upper plate 33a. A hex nut 34a is screwed into the upper end portion of the stud 34, a screw portion 34b is formed below the stud 34, and a large-diameter lower end locking portion 34c is provided at the lower end portion. The lower end locking portion 34 c is inserted into the presser 35. A top plate 36 is attached to the screw portion 34b by screwing.
[0038]
The upper plate 33 a is provided with a vent mechanism 37 and a valve seal 38, and a stud 39 is attached to the vent mechanism 37. A lower end locking portion 39a to be inserted into the presser 39b is attached to the lower portion of the stud 39. The valve seal 38 has a valve portion 38a, and the valve portion 38a opens and closes a through hole 38b formed in the base plate 33 up and down. As shown in FIG. 3 (a), a handle 40 is attached to the top plate 36 by pins 41 so as to be foldable to the left and right as shown in FIG. 3 (b).
[0039]
Therefore, in the above-described embodiment, the detachable seal member 31 is fixed to the base plate 33 by the mounting bolt 32 on the lower surface of the seal device 30. The seal member 31 has two seals, a taper portion seal 31a and a flat surface portion seal 31b. A stud 34 is assembled by a presser 35 so as to be rotatable above the center of the base plate 33.
[0040]
A top plate 36 is incorporated in the thread portion of the stud 34, and a convex portion is provided at a diagonal corner portion of the top plate 36, so that the top plate 36 is engaged with the concave portion of the transition piece 14. A hexagonal nut 34a is incorporated in the head of the stud 34 and can be rotated using a long wrench (not shown).
[0041]
By rotating the stud 34, the top plate 36 rotates, and rises at a position in contact with the transition piece 14, and has a mechanical structure that obtains a sealing effect by applying a reaction force to the sealing member 31 and pressing it. A vent mechanism 37 is provided on the top of the base 33, and the valve seal 38 is moved up and down by the stud 34 to perform opening and closing operations.
[0042]
A handle 40 that can be tilted to the left and right is provided above the stud 34. When the seal device 30 is installed, the handle 40 becomes vertical when the lift device is lifted and moved so that the riser pipe seal device 30 is placed at a predetermined position. It will be easy to move to. Next, after the riser pipe seal device 30 is installed at a predetermined position, the handle 40 is inclined to either the left or right, so that the operation can be easily performed when the stud 34 below the handle 40 is rotated. .
[0043]
The present embodiment has the following effects.
(1) After removing the jet pump inlet mixer installed in the reactor pressure vessel of the boiling water reactor, it is removably installed in the transition piece opening at the top of the riser pipe to seal the jet pump riser pipe be able to.
As a result, it is not necessary to drain the reactor water, so the radiation exposure of workers can be greatly reduced, the soundness of the reactor can be confirmed, and the operating rate of the nuclear power plant can be improved. it can.
[0044]
(2) By providing a seal member with a mechanical tightening method that does not require a drive source, a seal member that can be reliably and quickly installed is mounted on the tapered surface of the transition piece opening at the top of the riser tube and the top surface of the riser tube. Since the structure is sealed at two locations, the repair work can be performed safely, and the reliability of the worker can be greatly improved and the work can be performed reliably and in a short time.
[0045]
(3) It has a handle part that can be lifted by a gripping device, and this handle part tilts from a vertical state to an oblique state when the riser pipe sealing device is seated at a predetermined position, and is tightened on the lower side of the handle. Because of the structure that can be engaged with the screw head, the function of the riser pipe sealing device can be sufficiently exerted.
[0046]
(4) Since the air vent is built in the upper part of the seal device and the mechanical air vent is built in so that the riser tube is not evacuated when the riser tube seal device is removed, the riser tube seal device is removed. Can be carried out reliably and in a short time. Further, since the seal member has a separable structure and only the seal portion is replaceable, the soundness of the seal member can be improved.
[0047]
【The invention's effect】
According to the present invention, in combination with the effect of the above embodiment, when a crack or the like occurs in the riser pipe of the jet pump, the inspection is performed without replacing the shroud or a part of the shroud or discharging the reactor water. , Repair work can be done and the nuclear power plant can be operated continuously.
[Brief description of the drawings]
FIG. 1 is an elevational view showing a partial cross-section for explaining a first embodiment of a sealing device for an in-reactor pump according to the present invention.
FIG. 2 is a plan view of FIG.
3A is an enlarged view showing a handle portion in FIG. 1, and FIG. 3B is a side view of FIG.
FIG. 4 is a cross-sectional view showing a configuration of a general boiling water reactor.
FIG. 5 is a perspective view showing the jet pump in FIG. 4 with a part cut away.
6 is an enlarged view of a riser pipe of the jet pump in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Coolant, 3 ... Core, 4 ... Steam separator, 5 ... Steam dryer, 6 ... Main steam pipe, 7 ... Downcomer part, 8 ... Control rod guide pipe, 9 ... Control Rod drive mechanism, 10 ... core shroud, 11 ... jet pump, 12 ... riser pipe, 13 ... recirculation inlet nozzle, 14 ... transition piece, 14a ... recess, 15a, 15b ... elbow, 16a, 16b ... mixing nozzle, 17a, 17b ... Inlet throat, 18a, 18b ... Diffuser, 19 ... Measuring pipe, 20 ... Riser brace, 21 ... Ear, 22 ... Groove, 23 ... Jet pump beam, 24 ... Head bolt, 25 ... Riser blanket, 26 ... Baffle Plate, 27 ... Support, 28 ... Transition piece opening, 30 ... Sealing device, 31 ... Sealing member, 31a ... Taper seal, 31b ... Plate seal, 32 ... Mounting bolt, 33 ... Base plate, 33a ... Upper plate 33b ... lower plate, 34 ... Stud, 34a ... Hex nut, 34b ... Screw part, 34c ... Lower end locking part, 35 ... Presser, 36 ... Top plate, 36a ... Convex part, 37 ... Vent mechanism, 38 ... Valve seal, 38a ... Valve part , 38b ... through hole, 39 ... stud, 39a ... lower end locking portion, 39b ... presser, 40 ... handle, 41 ... pin.

Claims (4)

A seal member that lands on an opening of a transition piece connected to an upper portion of a riser pipe of a jet pump installed in a downcomer portion between a reactor pressure vessel and a core and seals the opening in a watertight manner, and this seal A base plate having a member attached to the lower surface, a top plate having a convex portion that fits into a concave portion formed in the transition piece, and a stud that is attached to the base plate and the other is attached to the top plate. A sealing device for an in- reactor pump, wherein the sealing member is pressed against an opening of the transition piece by rotating the stud . 2. The atom according to claim 1 , wherein the seal member includes a taper seal that seals a taper surface formed in an opening of the transition piece, and a flat surface seal that seals an upper surface continuous to the taper surface. In-furnace pump seal device.   2. The reactor internal pump sealing device according to claim 1, wherein a folding handle is attached to the top plate.   2. The sealing device for an in-reactor pump according to claim 1, wherein the base plate is provided with a vent mechanism having a valve seal.

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