U.S. patent application number 10/259529 was filed with the patent office on 2003-07-10 for device and method for repairing inside of reactor pressure vessel.
This patent application is currently assigned to HITACHI, LTD., BABCOCK-HITACHI K.K.. Invention is credited to Go, Shinji, Hirano, Katsuhiko, Kurosawa, Kouichi, Mahara, Youichi, Nagashima, Toshiharu, Nitta, Kazuhiro, Suzuki, Yoshitoshi.
Application Number | 20030128794 10/259529 |
Document ID | / |
Family ID | 18836516 |
Filed Date | 2003-07-10 |
United States Patent
Application |
20030128794 |
Kind Code |
A1 |
Kurosawa, Kouichi ; et
al. |
July 10, 2003 |
Device and method for repairing inside of reactor pressure
vessel
Abstract
An opening portion 3 is produced by cutting a recirculating
piping 72 connected to a recirculating nozzle 2 of a reactor
pressure vessel 1. A repairing device is brought into an annulus 10
of the reactor pressure vessel 1 from the opening 3, thereby
repairing the annulus 10.
Inventors: |
Kurosawa, Kouichi; (Hitachi,
JP) ; Mahara, Youichi; (Hiroshima, JP) ;
Nagashima, Toshiharu; (Kure, JP) ; Nitta,
Kazuhiro; (Kure, JP) ; Go, Shinji; (Hitachi,
JP) ; Suzuki, Yoshitoshi; (Takahagi, JP) ;
Hirano, Katsuhiko; (Hitachi, JP) |
Correspondence
Address: |
CROWELL & MORING, LLP
Intellectual Property Group
P.O. Box 14300
Washington
DC
20044-4300
US
|
Assignee: |
HITACHI, LTD., BABCOCK-HITACHI
K.K.
|
Family ID: |
18836516 |
Appl. No.: |
10/259529 |
Filed: |
September 30, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10259529 |
Sep 30, 2002 |
|
|
|
09951898 |
Sep 14, 2001 |
|
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Current U.S.
Class: |
376/260 |
Current CPC
Class: |
Y02E 30/30 20130101;
G21C 17/007 20130101 |
Class at
Publication: |
376/260 |
International
Class: |
G21C 019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2000 |
JP |
2000-365807 |
Claims
What is claimed is:
1. A method for repairing the inside of a reactor pressure vessel
for a boiling water reactor provided with a recirculating nozzle,
the method comprising steps of: draining coolant in said reactor
pressure vessel; cutting a recirculating piping connected to said
recirculating nozzle to produce an opening connected to said
recirculating nozzle; bringing a repairing device into an annulus
in said reactor pressure vessel from said opening; and using said
repairing device to repair the inside of said annulus.
2. A method for repairing the inside of a reactor pressure vessel
for a boiling water reactor provided with a recirculating nozzle,
the method comprising steps of: draining coolant in said reactor
pressure vessel; removing a recirculating piping connected to said
recirculating nozzle from a recirculating pump to produce an
opening connected to said recirculating nozzle; bringing a
repairing device into an annulus in said reactor pressure vessel
from said opening; and using said repairing device to repair the
inside of said annulus.
3. A method for repairing the inside of a reactor pressure vessel
according to claim 1 and claim 2, wherein at least either
inspecting a repaired part with a camera, installing monitoring
cameras during repairing, detecting flaws with ultrasonic, or
beveling for repairing with electrical discharge machining is
conducted from the top of said pressure vessel before the coolant
in said reactor pressure vessel is drained.
4. A method for repairing the inside of a reactor pressure vessel
for a boiling water reactor according to claim 1 and claim 2, the
method comprising further steps of: bringing said repairing device
into said reactor pressure vessel through said opening; lifting
up/down said repairing device with a jig for lifting-up/down;
separating said repairing device from said jig for lifting-up/down
after said repairing device reaches the height of a baffle plate;
installing said repairing device on said jig for lifting-up/down
again after repairing the inside of the reactor; and recovering
said repairing device from the inside of the reactor.
5. A method for repairing the inside of a reactor pressure vessel
according to claim 4, wherein said jig for lifting-up/down is
brought in by a straight or curved guide held by a jig for
bringing-in through said opening.
6. A device for repairing the inside of a reactor pressure vessel
comprising: an operation tool, which is used to repair an inside of
an annulus when coolant in a reactor pressure vessel of a boiling
water reactor provided with a recirculating nozzle is drained, a
recirculating piping connected to said recirculating nozzle is cut
to produce an opening connected to said recirculating nozzle, the
repairing device is brought into said annulus in said reactor
pressure vessel from said opening; and suction disk pads; wherein
said repairing device is constituted so as to stick to a wall face
inside said annulus to maintain an attitude.
7. A device for repairing the inside of a reactor pressure vessel
comprising: an operation tool, which is used to repair an inside of
an annulus when coolant in a reactor pressure vessel of a boiling
water reactor provided with a recirculating nozzle is drained, a
recirculating piping connected to said recirculating nozzle is cut
to produce an opening connected to said recirculating nozzle, the
repairing device is brought into said annulus in said reactor
pressure vessel from said opening; suction disk pads; and driving
rollers; wherein said repairing device is constituted so as either
to travel in the horizontal direction or to turn while maintaining
the attitude by sticking to a wall face inside said annulus.
8. A device for repairing the inside of a reactor pressure vessel
according to claim 7 further comprising: multiple joints for
changing the shape of said repairing device according to the
curvature of a wall face inside said annulus.
9. A device for repairing the inside of a reactor pressure vessel
according to claim 8 further comprising: encoders for detecting the
rotations of said driving rollers and the angles of said joints;
wherein said repairing device is constituted so as to calculate
either a position inside said reactor pressure vessel, the
curvature of the inner wall face, or a distance between the nuclear
pressure vessel and a jet pump diffuser.
10. A device for repairing the inside of a reactor pressure vessel
according to claim 8 further comprising: double-sided suction disk
pads for traveling on discontinued and separated wall faces such as
a wall face of the reactor pressure vessel to an outer face of the
jet pump diffuser.
11. A device for repairing the inside of a reactor pressure vessel
according to either one of claims 7 to 9 further comprising: an
operation tool driving mechanism conducting at least one type of
motion of traveling said operation tool up/down and rotationally,
and moving said operating tool while swinging it; wherein said
operation tool is either a welding torch, a laser head, an electric
discharge machining device, a camera, a grinder, a dust collector,
a device for applying liquid penetrant for detecting flaws,
cleaning, and inspecting, an ultrasonic probe, or a dimension
measuring device, and these tools are changed to conduct repairing
such as welding, laser machining, electric discharge machining,
visual inspection, polishing, grinding, collection dusts and chips,
detecting flaws with liquid penetration, detecting flaws with
ultrasonic, and measuring dimension.
12. A device for repairing the inside of a reactor pressure vessel
according to either one of claims 7 to 9, wherein the operation
tool installed on said repairing device is a cable/hose relay box,
said repairing device is brought inside the annulus after a first
repairing device including the operation tool to relay cables and
hoses for the first repairing device, and said repairing device
supports routing the cables and the hoses from the nozzle to the
first repairing device.
13. A device for repairing the inside of a reactor pressure vessel
according to either one of claims 7 to 12, wherein said repairing
device is constituted such that said repairing device extends arms
or cushions to a wall face on the opposite side for pushing the
wall face for fixing when said device is fixed on a part of a wall
face where the suction with the suction disks is difficult.
14. A device for repairing the inside of a reactor pressure vessel
according to claim 5, wherein said jig for bringing-in is provided
with a member for shielding radiation so as to add a function for
shielding radiation irradiated from the reactor pressure vessel
when an operator comes close to a cut part on a recirculating
piping, an outlet nozzle for recirculating water, or a safe end of
the outlet nozzle for recirculating water.
15. A device for repairing the inside of a reactor pressure vessel
according to claim 5, wherein said jig for bringing-in is provided
with a bendable self-traveling mechanism, and is constituted so as
to travel by itself to bring in said repairing device when said
repairing device is brought into the reactor pressure vessel
through a bent piping from said opening.
16. A device for repairing the inside of a reactor pressure vessel
according to claim 11, wherein said device for applying liquid
penetrant for detecting flaws, cleaning, and inspecting has an
airbag mechanism and a liquid suction nozzle, and an enclosed space
is formed around a part to be repaired by pressing said airbag
mechanism against the part to be repaired, thereby sucking the
liquid penetrant for detecting flaws and cleaning liquid without
diffusing, resulting in eliminating cleaning a wide area other than
the subject part.
17. A device for repairing the inside of a reactor pressure vessel
according to claim 11, wherein said electric discharge machining
device is provided with an airbag mechanism, a machining liquid
injection nozzle, a machining liquid suction nozzle, and an
electric discharge machining electrode, and an enclosed space is
formed around a part to be repaired by pressing said airbag
mechanism against the part to be repaired, the electric discharge
electrode is pressed on a face to be machined to conduct electric
discharge machining while the machining liquid is flowing from said
machining liquid injection nozzle, thereby sucking machining chips
without diffusing, resulting in conducting local electric discharge
machining under an aerial environment without water.
18. A method for repairing the inside of a reactor pressure vessel
according to either of claims 1 to 3, the method comprising further
steps of: inspecting a part to be repaired with a camera from the
top of the reactor pressure vessel, and beveling for repairing with
an electric discharge device brought to the part to be repaired
through a guide pipe installed in water from both the annulus side
and the inside of the nuclear reactor in a submersed state before
coolant in the reactor pressure vessel is drained; draining
coolant; bringing in the repairing device with said method from an
opening on recirculating piping, an outlet nozzle for recirculating
water, or a safe end of the outlet nozzle for recirculating water
in an aerial state; and bringing in another repairing device into
the nuclear reactor through said guide pipe from the top of the
reactor pressure vessel; wherein repairing operation is conducted
both from the annulus side and the inside of the nuclear reactor
side, and the same part is repaired from the both sides.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to repairing for a reactor
pressure vessel and structures inside the reactor pressure vessel
in service, particularly a method and a device for repairing an
annulus of the pressure vessel while nuclear fuel and coolant are
removed.
[0002] Though safety has a priority in any devices, the safety of a
reactor pressure vessel has the highest priority in a nuclear power
plant, and repairing the nuclear pressure vessel and structures
inside the nuclear pressure vessel during service period is
prescribed.
[0003] The repairing operation for the pressure vessel is usually
conducted while a repairing device is installed inside the vessel.
The prior art adopts an operation procedure, in which the repairing
device is inserted into the pressure vessel from the top of the
nuclear reactor, and the device is taken out after the repairing
operation.
[0004] During the repairing operation, usually the pressure vessel
is filled with water, and remote control devices with submersible
capability are used in order to reduce the exposure to nuclear
radiation of operators.
[0005] Usually a chain block is used for installing the repairing
device, and a method of lifting the repairing device, and inserting
it into and taking it out from the pressure vessel is adopted. When
the repairing device is being lift down to a baffle plate of the
annulus, it is difficult to check the position of lifting down from
the top of the nuclear reactor since the structures inside the
nuclear reactor stand together in the course.
[0006] Also, since this is a complicated operation requiring
monitoring with a submersible television camera for an interference
of the repairing device, the operation takes a long period.
[0007] Here, the annulus is a space in a toric shape formed in a
part surrounded by an inner wall face of the pressure vessel
outside a core shroud in the pressure vessel of a boiling water
reactor.
[0008] Thus, in the prior art, the situation described above is a
serious problem for reducing the exposure and shortening the
process.
[0009] In addition, since the remote control devices with
submersible capability require a waterproof seal structure or a
waterproof pipe to be installed, designing such a device is
demanding, and largely increases the cost.
[0010] In addition, welding and PT (liquid penetrant flaw
detection) inspection require making the inside of the pressure
vessel aerial. After the repairing device is installed, reactor
water is drained the for operation. After the operation, the
pressure vessel is filled with water to remove the repairing
device. This repeated filling/draining operation extends the
operation period, and increases the operation cost.
[0011] For instance, as described in Japanese Application Patent
Laid-open Publication Nos. Hei 09-159788, Hei 09-211182, and
2000-258587, devices are disclosed for allowing individual
operations of inspecting, repairing, and preventively maintaining
structures in the nuclear reactor such as a jet pump and an outer
surface of a shroud installed in the annulus while water is
filled.
[0012] In this case, since the operation is conducted under water,
it has a large effect on reducing the exposure of the repairing
device itself and operators when installing the device. However as
described before, the operation is conducted remotely, the
operation is extremely difficult, and the increase of cost is not
negligible. Further, the welding and the PT inspection in the
repairing operation should be aerial, and they require
filling/draining water in the reactor repeatedly, resulting in a
problem of the extended operation period as described before.
[0013] On the other hand, Japanese Application Patent Laid-open
Publication Nos. Hei 11-174192 and Hei 11-109082, for example,
disclose devices, which have access to the annulus in the water and
travel automatically on the baffle plate through remote operation
for nondestructive inspection. Even in this case, as described
before, since the remote operation under water is assumed, the
operation is extremely difficult, and if a repairing is required,
these devices cannot apply to the repairing and the repairing
device since the repairing should be aerial.
[0014] The prior art described before does not consider repairing
applied to an annulus of a pressure vessel, and has the problem of
difficult operation and extended work period.
[0015] If the prior art is applied to repairing of a reactor
pressure vessel in service, installing/removing the repairing
device are conducted in water, and operations such as welding and
PT inspection are conducted in air.
[0016] It takes a fairly long time to drain and to fill reactor
water in the pressure vessel.
[0017] Installing/removing the repairing device requires monitoring
with a submersible camera for an interference of the repairing
device with the structures in the reactor. Further, when the
repairing device is inserted into the annulus, since it is
difficult to determine the position of the repairing device, the
repairing operation becomes extremely difficult.
[0018] The previous art causes the problem of difficulty in the
repairing operation and the extended work period.
[0019] Also, since the repairing device should be installed/removed
under water, the repairing device should have waterproof
capability, resulting in a large cost in design and production.
[0020] Further, the previous art does not provide a technique for
repairing from the both sides when repairing is difficult for an
operation from one side of the pressure vessel.
SUMMARY OF THE INVENTION
[0021] The purpose of the present invention is to provide a method
and a device for repairing the inside of a pressure vessel of a
nuclear reactor, which conduct the repairing operation in an
annulus of the reactor pressure vessel easily in a short
period.
[0022] The purpose described before is achieved such that coolant
in a reactor pressure vessel of a boiling water reactor provided
with a recirculating nozzle is drained, a recirculating piping
connected to said recirculating nozzle is cut to produce an opening
connected to said recirculating nozzle, the repairing device is
brought into said annulus in said reactor pressure vessel from said
opening, and said repairing device repairs the inside of said
annulus.
[0023] The purpose described before is also achieved such that
coolant in a reactor pressure vessel of a boiling water reactor
provided with a recirculating nozzle is drained, a recirculating
piping connected to said recirculating nozzle is removed from a
recirculating pump to produce an opening connected to said
recirculating nozzle, the repairing device is brought into said
annulus in said reactor pressure vessel from said opening, and said
repairing device repairs the inside of said annulus Simultaneously,
the purpose described before is also achieved such that either
inspecting a repaired part with a camera, installing monitoring
cameras during repairing, detecting flaws with ultrasonic or
beveling for repairing with electrical discharge machining is
conducted from the top of said pressure vessel before the coolant
in said reactor pressure vessel is drained.
[0024] Simultaneously, the purpose described before is also
achieved such that said repairing device is brought into said
reactor pressure vessel through said opening, said repairing device
is lifted up/down with a jig for lifting-up/down, said repairing
device is separated from said jig for-lifting-up/down after it
reaches the height of a baffle plate, said repairing device is
mounted on said jig for lifting-up/down again after repairing the
inside of the reactor, and the repairing device is recovered from
the inside of the reactor.
[0025] The purpose described before is also achieved such that said
jig for lifting-up/down is brought in by a straight or curved guide
held by a jig for bringing-in through said opening.
[0026] This allows installing the repairing device to the annulus
to be repaired without interfering with constituting devices in a
nuclear reactor. Since the distance between a recirculating water
outlet nozzle and the annulus is short, and the repairing device
can pass while avoiding a reactor core area with high nuclear
radiation, the degradation of the repairing device due to the
nuclear radiation is avoided.
[0027] Also this allows traveling the repairing device in parallel
from said opening to the inner wall of the reactor pressure vessel,
and to travel the repairing device horizontally along the inner
wall of the reactor pressure vessel from the height of said opening
and to the application height for the repairing operation, thereby
minimize a driving part required for the repairing device and
reducing the seize of the repairing device, resulting in providing
a margin for traveling of the repairing device on the annulus. This
also allows inserting the repairing device into the nuclear reactor
after the repairing device is aligned to the direction for the
operation before hand, thereby making the travel in the reactor
easily.
[0028] The purpose described before is achieved by a repairing
device comprising an operation tool for repairing an inside of an
annulus when coolant in a reactor pressure vessel of a boiling
water reactor provided with a recirculating nozzle is drained, a
recirculating piping connected to said recirculating nozzle is cut
to produce an opening connected to said recirculating nozzle, the
repairing device is brought into said annulus in said reactor
pressure vessel from said opening, and suction disk pads for
maintaining the attitude by sticking to a wall face inside said
annulus.
[0029] The purpose described before is also achieved by a repairing
device comprising an operation tool for repairing an inside of an
annulus when coolant in a reactor pressure vessel of a boiling
water reactor provided with a recirculating nozzle is drained, a
recirculating piping connected to said recirculating nozzle is cut
to produce an opening connected to said recirculating nozzle, the
repairing device is brought into said annulus in said reactor
pressure vessel from said opening, and suction disk pads and
driving rollers for traveling in the horizontal direction or for
turning while maintaining the attitude by sticking to a wall face
inside said annulus.
[0030] Simultaneously, said repairing device may have multiple
joints for freely changing the shape according to the curvature of
the wall face inside said annulus, or said repairing device may be
simultaneously provided with encoders so as to detect the rotations
of said driving rollers and the angle of said joints, and is
constituted so as to calculate at least either a position inside
said reactor pressure vessel, the curvature of the inner wall face,
or a distance between the nuclear pressure vessel and a jet pump
diffuser.
[0031] Simultaneously, said repairing device may be simultaneously
provided with double-sided suction disk pads for traveling on a
discontinued and separated wall faces such as from a wall face of
the reactor pressure vessel to an outer face of the jet pump
diffuser.
[0032] Simultaneously, the purpose described before is also
achieved such that said repairing device is provided with an
operation tool driving mechanism conducting at least one type of
motion of moving said operation tool up/down, rotationally, and
while swinging it, said operation tool is either a welding torch, a
laser head, an electric discharge machining device, a camera, a
grinder, a dust collector, a device for applying liquid penetrant
for detecting flaws, cleaning, and inspecting, an ultrasonic probe,
or a dimension measuring device, and these tools are changed to
conduct repairing such as welding, laser machining, electric
discharge machining, visual inspection, polishing, grinding,
collection dusts and chips, detecting flaws with liquid
penetration, detecting flaws with ultrasonic, and measuring
dimension.
[0033] Simultaneously, the purpose described before is also
achieved such that the operation tool installed on said repairing
device is a cable/hose relay box, said repairing device is brought
inside the annulus after a first repairing device including the
operation tool to relay cables and the hoses for the first
repairing device, and said repairing device supports routing cables
and hoses from the nozzle to the first repairing device.
[0034] Simultaneously, said repairing device may be constituted
such that the repairing device extends arms or cushions to a wall
face on the opposite side for pushing the wall face for fixing when
the device is fixed on a part of a wall face where the suction with
the suction disks is difficult.
[0035] Simultaneously, the purpose described before is also
achieved such that said jig for bringing-in is provided with a
member for shielding radiation so as to add a function for
shielding radiation irradiated from the reactor pressure vessel
when a operator comes close to a cut part on a recirculating
piping, an outlet nozzle for recirculating water, or a safe end of
the outlet nozzle for recirculating water.
[0036] Simultaneously, the purpose described before is also
achieved such that said jig for bringing-in is provided with a
bendable self-traveling mechanism, and is constituted so as to
travel by itself to bringing in said repairing device when said
repairing device is brought into the reactor pressure vessel
through a bent piping from said opening.
[0037] Simultaneously, the purpose described before is also
achieved such that said device for applying liquid penetrant for
detecting flaws, cleaning, and inspecting has an airbag mechanism
and a liquid suction nozzle, and an enclosed space is formed around
a part to be repaired by pressing said airbag mechanism against the
part to be repaired, thereby sucking the liquid penetrant for
detecting flaws and cleaning liquid without diffusing, resulting in
eliminating cleaning a wide area other than the subject part.
[0038] Simultaneously, the purpose described before is achieved
such that said electric discharge machining device is provided with
an airbag mechanism, a machining liquid injection nozzle, a
machining liquid suction nozzle, and an electric discharge
machining electrode, and an enclosed space is formed around a part
to be repaired by pressing said airbag mechanism against the part
to be repaired, the electric discharge electrode is pressed on a
face to be machined to conduct electric discharge machining while
the machining liquid is flowing from said machining liquid
injection nozzle, thereby sucking machining chips without
diffusing, resulting in enabling local electric discharge machining
under an aerial environment without water.
[0039] Simultaneously, the purpose described before is achieved
such that inspecting a part to be repaired with a camera from the
top of the reactor pressure vessel and beveling for repairing with
an electric discharge device brought to the part to be repaired
through a guide pipe installed in water are conducted from both the
annulus side and the inside of the nuclear reactor in a submersed
state before coolant in the reactor pressure vessel is drained, the
repairing device is brought in with said method from an opening of
recirculating piping, an outlet nozzle for recirculating water, or
a safe end of the outlet nozzle for recirculating water in an
aerial state after coolant is drained, another repairing device is
brought in the nuclear reactor through said guide pipe from the top
of the reactor pressure vessel, repairing operation is conducted
both from the annulus side and the inside of the nuclear reactor
side, and the same part is repaired from the both sides.
[0040] With the mean described before, attaching the suction disk
pads to the repairing device easily holds the repairing device at a
certain position for repairing operation.
[0041] Attaching the driving rollers for traveling to the repairing
device provided with the suction disk pads allows the repairing
device to travel by rotating the driving rollers while the suction
force is maintained, thereby traveling rotationally while
maintaining the same height around the structures in the annulus,
resulting in having access to a part to be repaired.
[0042] Further, since the repairing device is constituted as a
symmetrical multiple joint structure and is provided with the disk
pads on the both sides, when the repairing device is installed the
annulus, folding said joint on one side move that side of the
repairing device to a neighboring structure in the reactor, and the
suction disk pad holds that side of the repairing device to said
neighboring structure. Folding the joint on the other side to the
structure to which the repairing device travels onto moves the
entire repairing device to the neighboring structure in the
reactor.
[0043] The position in the reactor and the curvature and the like
of the wall face of a structure to which the repairing device
sticks are obtained by detecting and calculating the rotations of
the driving rollers with the encoders, thereby obtaining precise
position information and shape information of the structure.
[0044] The design of the device is unified by mounting and changing
the operation tools for repairing according to the purpose on said
repairing device, thereby decreasing the cost for design and
production, and increasing the reliability, resulting in allowing
various repairing operations in the annulus.
[0045] The load on routing cables and hoses for the repairing
device is eliminated when the repairing device is reaching a part
far from the outlet nozzle by installing a cable/hose relay box on
a second repairing device, and bringing the second repairing device
into a nuclear reactor as an auxiliary carriage for handling
cables, thereby reducing trouble potential caused by the cable
handling, resulting in a reliable operation.
[0046] Said repairing device provided with the suction disk pads
are fixed by extending arms or cushions to a direction opposite to
the wall face to which the device sticks, thereby fixing the device
stably on a wall face with recesses and protrusions.
[0047] The opening has a high dose rate, and is a hard environment
for operators to approach since nuclear radiation from the reactor
pressure vessel is irradiated from the nozzle or the opening of the
piping.
[0048] Providing a shielding capability for a jig for bringing-in
to shield the radiation from the opening makes the environment easy
to approach.
[0049] If there is a bent part in a bringing-in path from the
opening to the annulus, using self-traveling bringing-in device as
a jig for bringing-in enables to bring in the repairing device to
the annulus.
[0050] When liquid penetrant flaw detecting inspection is
conducted, installing airbag mechanism and a liquid suction nozzle
to a liquid penetrant flaw detecting device enables to press the
airbags to a part to be repaired to form an enclosed space, thereby
sucking liquid penetrant for detecting flaws and cleaning liquid
without diffusing, resulting in eliminating cleaning a wide area
other than the subject part.
[0051] For an electric discharge machining for eliminating flaws
and beveling for repair, an electric discharge machining device is
provided with an airbag mechanism, a machining liquid injection
nozzle, and a machining liquid suction nozzle and an enclosed space
is formed by pressing said airbag mechanism against the part to be
repaired, and electric discharge machining is conducted in said
enclosed space thereby sucking machining chips and the machining
liquid without diffusing, resulting in local electric discharge
machining under an aerial environment without water while
maintaining the surrounded area clean.
[0052] For a method inspecting a part to be repaired and removing
flaws, inspecting and repairing simultaneously or alternately from
the annulus side and the inside of the reactor effectively applies
a highly reliable inspection and repair to a wide area.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] FIG. 1 is a flowchart indicating an embodiment of a
repairing method for a reactor pressure vessel with the present
invention.
[0054] FIG. 2 is a diagram describing a jig for bringing in a
device from a recirculating water outlet nozzle in an embodiment of
the repairing method for a reactor pressure vessel with the present
invention.
[0055] FIG. 3 is a diagram describing the jig for bringing in the
device from the recirculating water outlet nozzle in the embodiment
of the repairing method for a reactor pressure vessel with the
present invention.
[0056] FIG. 4 is a diagram describing the jig for bringing in the
device from the recirculating water outlet nozzle in the embodiment
of the repairing method for a reactor pressure vessel with the
present invention.
[0057] FIG. 5 is a diagram describing the jig for bringing in the
device from the recirculating water outlet nozzle in the embodiment
of the repairing method for a reactor pressure vessel with the
present invention.
[0058] FIG. 6 is a diagram describing an action to remove the
repairing device from a lift with an embodiment of the present
invention.
[0059] FIG. 7 is a diagram describing an embodiment of a repairing
device with the present invention.
[0060] FIG. 8 is a diagram describing an annulus of a nuclear
pressure vessel which is a subject of an embodiment of the
repairing device with the present invention.
[0061] FIG. 9 is a diagram describing an embodiment of the
repairing device with the present invention provided with a cable
support head.
[0062] FIG. 10 is a diagram describing a method moving between
walls for an embodiment of the repairing device with the present
invention.
[0063] FIG. 11 is a diagram describing a rotating motion of an
embodiment of the repairing device with the present invention.
[0064] FIG. 12 is a diagram describing a principle for calculating
a curvature radius of a structure for an embodiment of the
repairing device with the present invention.
[0065] FIG. 13 is a diagram describing a fixing motion with pushing
arms of an embodiment of the repairing device with the present
invention.
[0066] FIG. 14 is a diagram describing a motion for bringing in the
repairing device through a bent part of a piping with an embodiment
of the repairing device with the present invention.
[0067] FIG. 15 is a diagram describing an embodiment of the
repairing device with the present invention when the repairing
device is applied to detecting flaws with liquid penetrant.
[0068] FIG. 16 is a diagram describing an embodiment of the
repairing device with the present invention when the repairing
device is applied to electric discharge machining in the air.
[0069] FIG. 17 is a diagram describing one example of a pressure
vessel of a boiling water nuclear reactor which is an application
subject of a method and a device for repairing the inside of a
reactor pressure vessel with the present invention.
[0070] FIG. 18 is a diagram describing one example of an
arrangement of machines inside the reactor when the repairing is
conducted from the inside of the reactor.
[0071] FIG. 19 is a flowchart indicating another embodiment of a
repairing method for a reactor pressure vessel with this
invention.
[0072] FIG. 20 is a diagram describing an example of an arrangement
of devices in an embodiment of the present invention when repairing
is conducted from both the annulus side and the inside of the
reactor.
DETAILED DESCRIPTION OF THE INVENTION
[0073] The following section describes a repairing method and a
repairing device for the inside of a reactor pressure vessel
according to the present invention using embodiments described in
drawings.
[0074] First, an example of a reactor pressure vessel, which is an
application subject of the present invention is described using
FIG. 17.
[0075] FIG. 17 shows a reactor pressure vessel and structures
inside a nuclear reactor in a nuclear power plant using a boiling
water type light water reactor, and the entire reactor pressure
vessel is indicated as 1.
[0076] A dryer 43, a separator 44, a shroud support cylinder 40 and
a reactor core shroud 42 supported by the shroud support cylinder
40 are installed in this reactor pressure vessel 1. A nuclear fuel
assembly 96 is stored in the reactor core shroud 42.
[0077] As an example of the sizes of the reactor pressure vessel 1,
the inner diameter is about 6.5 m, and the outer diameter of the
reactor core shroud 42 is about 5 m.
[0078] An RPV head 95 for sealing the nuclear reactor, the nuclear
fuel assembly 96, and a nuclear reactor well 94, which is filled
with water when machines in the reactor are removed to serve as a
pool for transporting path for removed machines are provided on the
top of the reactor pressure vessel 1. Here, RPV stands for Reactor
Pressure Vessel.
[0079] A recirculating water outlet nozzle 2 is installed on the
bottom of the reactor pressure vessel 1. A jet pump 39 installed on
a baffle plate 41 exists in a cylindrical space surrounded by an
inner wall of the pressure vessel 1 and the reactor core shroud 42.
This toric narrow space in which this jet pump 39 is installed is
the annulus 10 described before.
[0080] A space inside the reactor core shroud 42 and below the
baffle plate 41 other than this annulus 10 is called an inside of
the reactor 91.
[0081] A drain piping 93 is provided on the bottom of the pressure
vessel 1 to drain the coolant in the vessel.
[0082] The present invention relates to a repairing method and a
repairing device for welded parts close to the annulus 10 such as a
welded part between the reactor pressure vessel 1 and the baffle
plate 41, a welded part between the baffle plate 41 and the shroud
support cylinder 40, a welded part between the shroud 42 and shroud
support cylinder 40, or a welded part between the baffle plate 41
and the jet pump in the annulus 10. The following part describes
the detail along with embodiments indicated in drawings.
[0083] FIG. 1 is a flowchart indicating a method for repairing the
inside of the annulus with an embodiment of the present invention.
According to FIG. 1 with reference to FIG. 17, a repairing
operation based on the steps in FIG. 1 begins with a process of
removing the RPV head 95 from the reactor pressure vessel 1, i.e.
nuclear reactor opening process S1.
[0084] The nuclear reactor well 94 is filled with water to reduce
radiation exposure (S2). The machines inside the reactor such as
the dryer 43 and the separator 44, and the nuclear fuel assembly 96
are removed from the reactor pressure vessel 1, and are taken out
from the top (S3). Depending on the condition, a process for
draining the water in the nuclear reactor well 94, i.e. well
draining S4 is conducted.
[0085] The annulus 10 is inspected with VT (visual inspection)
(S5). If a defect is found (S6), UT (ultrasonic flaw detecting
inspection) is used to check the position and the extent of the
defect. EDM (electric discharge machining) is employed to remove
the defect. Then, UT (ultrasonic flaw detecting inspection) is used
to check if the defect is removed (S7).
[0086] Monitoring cameras (not limited to one) are installed in
order to monitor the entire repairing operation for the annulus 10
(S8).
[0087] The cables for the monitoring cameras are pulled out from
the top of the reactor through a narrow gap left between the
reactor pressure vessel 1 and RPV head 95.
[0088] The installation of the monitoring cameras may be skipped,
and the number of the installed camera may be reduced. The detail
is described later.
[0089] The reactor water is drained from the pressure vessel 1
(S9). Any two parts of the recirculating water outlet nozzle 2, a
recirculating water outlet nozzle safe end 71, and a recirculating
piping 72 are cut (S10) to produce an opening 3.
[0090] From this opening 3, monitoring cameras and a prescribed
repairing device (described later) are sequentially brought into
the reactor pressure vessel 1. The repairing device, which has been
brought in is used to conduct prescribed PT inspection, welding,
polishing, PT inspection after welding, and the like (S11).
[0091] Then, the repairing device is brought out from the opening 3
(S12). The two parts of the recirculating water outlet nozzle 2,
the recirculating water outlet nozzle safe end 71, and the
recirculating piping 72, which are cut, are joined (S13). The
nuclear pressure vessel 1 is filled with water (S14). The nuclear
reactor well 95 is filled with water (S15). The removed machines
inside the reactor including the nuclear fuel assembly 96 are
returned to the pressure vessel 1, and are installed (S16). Water
is drained from the nuclear reactor well 96 (S17). The RPV head 95
is installed (S18).
[0092] The following section describes individual processes in FIG.
1 in detail.
[0093] FIG. 2 details the jig for a bringing-in 4, which is used
when the repairing device is brought in from the opening 3 after
the recirculating outlet nozzle 2 is cut and the piping 72 is
removed as a repairing method used in a state after the reactor
water is drained in the process from S9 to S11 in FIG. 1.
[0094] The jig for bringing-in 4 is provided with slide shafts 5
supported by slide bearings 6, and a chain for suspending device 11
(described later) lifted up/down by a pulley 8 on a remotely
operable electric lift. A lift member 9 is attached on the end of
the chain 11. The repairing device 7 is held while the repairing
device 7 is suspended to the lift member 9, as detailed later.
[0095] Fixing the jig for bringing-in 4 to an outer face of the
opening 3 provides a setup for bringing in the repairing device 7
into the annulus 10. The repairing device 7 is a device used in PT
inspection, welding, polishing, PT inspection after welding and the
like, and is an embodiment of the present invention as described
later.
[0096] Since radiation from inside the reactor leaks to the opening
3 coupled with the recirculating outlet nozzle 2, it is necessary
to reduce radiation exposure of operators during setup for
installing the jig for bringing-in 4. For that purpose, a shield
plate made of metal with high shielding efficiency against
radiation is provided on the jig for bringing-in 4, thereby
providing a radiation shielding capability corresponding to
estimated radiation dose.
[0097] A flange for socket and spigot mate is provided outside of
the opening 3 on the jig for bringing-in 4 as described in the
Fig., there by attaching to the opening 3 without a gap, resulting
in restraining the leakage-of the radiation sufficiently.
[0098] Since radioactivated machines in the reactor placed in a
reactor core area above the recirculating water outlet nozzle 2
also irradiate radiation, a shield plate 63 made of gamma ray
shield is attached above the opening 3 as needed.
[0099] The slide shafts 5 of the jig for bringing-in 4 are slid
manually or electrically as indicated by the arrow described in
FIG. 3, thereby the repairing device 7 attached to the lift member
9 of the jig for bringing-in 4 into the annulus 10 in the pressure
vessel 1.
[0100] The slide shafts 5 serve as a guide for bringing in the lift
member 9 from the opening 3. The slide shafts 5 are not limited to
a straight shape as indicated in the Fig. but they may be in
arbitrary shapes such as a curved shape according to the
bringing-in path.
[0101] The monitoring camera 97, which was brought in before hand
is used to monitor a series of operations such as bringing in/out
the repairing device 7, traveling the repairing device 7 described
later, and repairing.
[0102] The monitoring camera 97 is brought in the process of Step
S8 in FIG. 1. In place of this process, the monitoring camera 97
may be brought in with the jig for bringing-in 4 from the
recirculating water outlet nozzle 2 to the annulus 10 when
repairing.
[0103] The repairing device 7, which is suspended from the lift
member 9 of the jig for bringing-in 4 is lifted down while
suspended along the inner wall face of the reactor pressure vessel
1 until the repairing device 7 seats on a baffle plate 41 by
rotating the pulley 8 to extend the chain 11 downward as in FIG.
4.
[0104] Suction disk pads 12, which are not shown in this Fig. are
mounted on the repairing device 7 as described later.
[0105] The repairing device 7 sticks to the inner wall face of the
reactor pressure vessel 1 with the suction disk pads 12 as
indicated in FIG. 5. The lift member 9 is detached from the
repairing device 7 by slightly extending the slide shafts 5. The
repairing device 7 is retained in the annulus 10 by winding the
chain 11 with the pulley 8 to lift up the lift member 9.
[0106] FIG. 6 shows how to separate the repairing device 7 from the
lift member 9.
[0107] The Step 1 in FIG. 6 shows a state where the lift member 9
holds the repairing device 7. As described in the Fig., pins 45 are
provided at the top of the lift member 9, and holes 46 are provided
at the op of the repairing device 7. The pins 45 are inserted into
the holes 46 to hold the repairing device 7 to the lift member 9
while they are suspended.
[0108] After the repairing device 7 is stuck and held to the inner
face of the reactor pressure vessel 1 with the suction disk pads 12
in the Step 1, as indicated by an arrow, the lift member 9 is
lifted down by turning the pulley 8 to release the pins 4 of the
lift member 9 from the holes 46 of the repairing device 7 as
indicated in the Step 2.
[0109] In this Step 2, the slide shafts 5 of the jig for
bringing-in 4 are slightly slid toward the center of the reactor
pressure vessel 1. The repairing device 7 is completely detached
from the lift member 9 as indicated in the Step 3.
[0110] The repairing device 7 is retained in the annulus 10 by
winding up the chain 11 with the pulley 8 to lift the lift member 9
as indicated by an arrow, thereby returning the lift member 9 up to
the height of the recirculating water outlet nozzle 2.
[0111] The repairing device 7 is described in detail in FIG. 7.
[0112] This repairing device 7 relates to an embodiment of the
present invention as described before. The front view of the device
is indicated in (3) and the top views of the device are indicated
in (1) and (2).
[0113] The repairing device 7 is provided with double-sided suction
disk pads 12 for retaining the attitude of the entire device,
pneumatic ejectors 13 for generating negative pressure inside the
suction disk pads 12, and driving rollers 14 for traveling the
device while maintaining the attitude by sticking to the wall face
with the suction disks.
[0114] A suction device and a suction hose may replace the
pneumatic ejectors 13.
[0115] Driving motors for traveling 16 transmit rotation torque to
the driving rollers 14 through driving belts for traveling 15.
[0116] Total of eight driving rollers 14 are shown in (3) of FIG.
7. Among them, the motors drive four outer rollers on the top and
bottom of the double-sided suction disk pads 12, and top and bottom
driving rollers inside 14 are simple idle rollers to maintain the
traveling attitude.
[0117] The repairing device 7 is provided with driving gears for
folding 17 and driving motors for folding 18 to change the shape of
the device body. These mechanisms allow the repairing device 7 to
travel to a part to be repaired while taking required shapes. (1)
and (2) of FIG. 7 show control states of the folded shape of the
repairing device 7 with the driving motors for folding 18. As
indicated in (2), the repairing device 7 can take a shape where
parts on the both sides are folded at almost right angle with
shafts of the driving rollers 14 in inner side as joints. With
this, for example, the repairing device 7 can easily take a shape
along a cylindrical surface aligned with the inner wall face of the
reactor pressure vessel 1 as indicated in (1).
[0118] An operation tool for repairing loaded on the repairing
device 7 can be brought to a part to be repaired.
[0119] The operation tool is loaded on the repairing device 7 such
that the operation tool can take attitudes required for repairing,
which allows moving the operation tool in up/down, forward/reverse,
and left/right directions.
[0120] The forward/reverse direction here is the direction
perpendicular to the paper of FIG. 7, and is the up/down direction
in (3) in FIG. 7.
[0121] The up/down motion of the operation tool is provided by a
mechanism comprising slide rails 19 guiding an up/down travel, a
lead screw 20 changing a rotating motion to the up/down drive, and
a motor for up/down travel 22 rotating the lead screw 20 through
gears 21.
[0122] The forward/reverse motion of the operation tool is provided
by a mechanism where a motor for forward/reverse travel 23 rotates
a pinion 25 through a gear 24, thereby moving a rack 26 attached to
the operation tool in the forward/reverse direction.
[0123] The left/right motion of the operation tool is provided by a
mechanism where a motor for left/right travel 27 rotates a pinion
28, thereby moving a rack 29 attached to the operation tool in the
left/right direction.
[0124] This operation tool can be set to an optimal repairing angle
according to a part to be repaired, and a mechanism comprising a
motor for swinging the operation tool 30 and a gear 31 rotated by
this motor is provided.
[0125] FIG. 7 shows an embodiment of the repairing device where the
device is provided with a welding torch for repairing with welding.
The operation tool mounted on the repairing device 7 is not limited
to the welding torch indicated here, and any tool such as a
polishing grinder, a grinder, a camera for visual inspection, a
head for applying/cleaning liquid penetrant for liquid penetrant
flaw detecting inspection, and an observation head for liquid
penetrant flaw detecting inspection can be attached.
[0126] The repairing device 7 in this embodiment is easily applied
to different repairing operations such as polishing, grinding,
visual inspection, liquid penetrant flaw detecting inspection, and
ultrasonic flaw detecting inspection other than welding by
attaching different types of operation tools to be used.
[0127] The welding torch shown in (3) of FIG. 7 comprises a TIG
torch 32 including a tungsten electrode, a wire nozzle 33 serving
as a guide for feeding a welding wire, a CCD camera 34 for
observing the electrode, a part subject to welding, arc during
welding, and a weld pool, and a lamp 35 providing a part to be
welded with illumination, thereby enabling observation with the CCD
camera 34 while welding is not conducted.
[0128] The position and attitude of the TIG torch 32 is arbitrarily
controlled with individual mechanisms for driving the operation
tool provided on the repairing device 7, thereby applying TIG
welding to an arbitrary part to be repaired.
[0129] In (1) of FIG. 7, the TIG torch 32 in a state directed
toward the inner wall of a part to which the repairing device
sticks is shown as an example of the attitude.
[0130] FIG. 8 shows a state where the repairing device 7 inserted
from the recirculating outlet nozzle 2 has moved to a certain point
subject to repairing in the annulus 10. This Fig. shows a case
where the distance from the recirculating outlet nozzle 2 and the
part subject to repairing is long.
[0131] If this is the case, it may be difficult to route cables and
hoses to the repairing device 7.
[0132] To address this problem, a cable support head 36 indicated
in FIG. 9 is used, and is sequentially brought into the annulus 10
along with the repairing device 7 for relaying the hoses and
cables. This cable support head 36 is also indicated in FIG. 8.
[0133] The cable support head 36 is provided with the driving
mechanism for traveling, the driving mechanism for tuning, and the
double-sided suction disk pads as the repairing device 7, and is
provided with a relay box for cables and hoses 38 in place of the
driving mechanism for the operation tool.
[0134] Since the cable support head 36 and the repairing device 7
are connected with a cable duct 37, the repairing device 7 and the
cable support head 36 travel with maintaining a approximately
constant distance, resulting in eliminating a load on the repairing
device 7 caused by routing the cables.
[0135] With this embodiment, as indicated in FIG. 8, the repairing
device can move up to the 90-degree direction in the
circumferential direction in the annulus 10 from the recirculating
outlet nozzle 2 while avoiding the jet pump 39 and routing the
cables and hoses.
[0136] The repairing device 7 in this embodiment can change its
folded shape as described in (2) and (3) of FIG. 7.
[0137] This repairing device 7 can move to an outer face of a
shroud support cylinder 40 from the inner wall face of the reactor
pressure vessel 1 through a jet pump diffuser 39 in the annulus
10.
[0138] FIG. 10 describes this motion.
[0139] As described in the Step 1, the repairing device 7 sticks to
the inner wall face of the reactor pressure vessel 1.
[0140] From the state in the Step 1, those suction disk pads 12 in
one side of both the left and right side are released and the
repairing device folds as indicated in Step 2 to move the
double-sided suction disk pads 12 on the opposite side close to the
jet pump diffuser 39. The repairing device 7 activates the suction
disks on the rear side to stick to the jet pump diffuser 39,
thereby entering a state indicated in the Step 3.
[0141] The suction disk pads 12 left on the inner wall side of the
reactor pressure vessel 1 are released, are moved close to the jet
pump diffuser 39 as described before, and stick to the jet pump
diffuser 39, thereby moving over to the jet pump diffuser 39
completely as indicated in the Step 4.
[0142] The action of the pneumatic ejectors 13 generate the suction
force of the suction disk pads 12, and the driving rollers for
traveling 14 can receive a part of the suction force of the suction
disk pads 12 by separating the suction disk pads 12 slightly from
the face to stick to, thereby generating friction force between the
driving rollers 14 and the wall face, resulting in enabling the
travel.
[0143] The repairing device 7 travels around the jet pump diffuser
39 by driving the rollers 14 with the driving motors for traveling
16 as indicated in the Step 5. The repairing device 7 moves to the
side of the shroud support cylinder 40 as indicated in the Step
6.
[0144] After the Step 6, the suction disk pads 12 and the turning
mechanism are activated in a sequence reverse to that in the Step
2, and the repairing device 7 moves over from the jet pump diffuser
39 to the outer face of the shroud support cylinder 40, resulting
in the state in the Step 8.
[0145] Using the double-sided suction disk pads 12 enables to move
from one wall face to a neighboring wall face. With this moving
method, the repairing device 7, which enters from the recirculating
outlet nozzle, autonomously moves from the inner wall face of the
reactor pressure vessel 1 to which the repairing device 7 sticks to
the jet pump diffuser 39, and further to the shroud support
cylinder 40, resulting in easily having access to any parts in the
annulus 10 for the repairing operation.
[0146] The repairing device 7, which relates to this embodiment,
rotates the top and bottom driving rollers for traveling 14 in
directions opposite to each other to turn (rotate) the entire
repairing device 7 on the inner wall face of the reactor pressure
vessel 1 as in FIG. 11, resulting in providing a large degree of
freedom to the attitude of the operation tool.
[0147] The annulus of the reactor pressure vessel, which is the
subject of this embodiment, has an extremely strict dimensional
restriction. The structures inside the reactor, which are installed
in the annulus have large tolerances. Thus, it is highly provable
that the traveling distance and the position in the peripheral
direction of the repairing device 7 are not accurately obtained
unless they are corrected with actual curvature radii.
[0148] The repairing device 7, which relates to this embodiment,
takes advantage of the capability that it can take a folded shape
to calculate the curvature radius of a face to which it sticks with
the suction disk pads 12 from the folded angle. The following
section uses FIG. 12 to describe the principle of detecting
curvature radius.
[0149] The repairing device 7 is provided with encoders for
detecting angles of joints and detecting the rotations of the
driving rollers for traveling 14 respectively.
[0150] The joints here refer to parts where the repairing device 7
is folded as in (1) and (2) of FIG. 7. In this case they are shafts
for the driving rollers for traveling 14 on the inner side, and the
angles of joints are the angles formed with the folded parts.
[0151] In FIG. 12, the Point A is the shaft of the joint, which is
the center of the shaft of the inner driving rollers for traveling
14. The Point B and the Point C are the center of the shaft of the
inner driving roller 14. The Point B indicates the position before
folding, and the Point C indicates the position after folding.
[0152] The distance from the center of the device to the Point A is
D. The distance from the Point A to the Point B is (r). The angle
between the state where the device is in straight and the state
where the device sticks to the wall face is .theta.. The angle
.theta. can be read from the encoder, the distance D and the
distance (r) are the dimensions of the device and are constants.
The curvature radius is calculated using an equation indicated in
the Fig. using numerical values of .theta., D and (r).
[0153] The traveling distance of the repairing device 7 is obtained
by reading the rotation from the encoder provided on the driving
roller for traveling 14. Either the position the repairing device 7
in the peripheral direction of the RPV, in the peripheral direction
of the jet pump diffuser, or in the peripheral direction of the
shroud support cylinder is calculated accurately from the curvature
radius and the traveling distance.
[0154] FIG. 13 shows an embodiment of the repairing device 7 when a
subject to repairing has large protrusions and recesses such as a
welded part inside the reactor pressure vessel 1, the device is not
fixed stably only with the suction forces of the suction disk pads
12, and arms 47 extend toward a face opposite to the face to which
the device 7 sticks, and pushes them to fix the device 7.
[0155] Clad welding of anti-corrosion metal is usually applied to
the inner wall face of the reactor pressure vessel 1, and has
protrusions and recesses more or less. It is possible that the
suction capability of the suction disk pads 12 present a variation
when the repairing device 7 is on the inner face of the reactor
pressure vessel 1.
[0156] The repairing device 7 extends arms 47 to the opposing jet
pump diffuser 39, and pushes it to fix itself, resulting in
maintaining a stable attitude of the device in the case described
before.
[0157] In the embodiment in FIG. 1, though the opening 3 is
produced by cutting any two parts on the recirculating water outlet
nozzle 2, the recirculating water outlet nozzle safe end 71, and
the piping 72, the opening may be provided by removing the
recirculating piping 72 from a recirculating pump (not included in
the Fig.).
[0158] In this case, if the path for bringing-in from the opening
on the piping to the recirculating water outlet nozzle 2 is vent,
it is difficult to bring in the repairing device 7, and it is
hardly possible to use the jig for bringing-in 4 described in FIG.
2 to 5 to bring in.
[0159] FIG. 14 shows an embodiment of a device for bringing-in
proper for such a case. The embodiment indicated in this Fig. uses
a self-traveling bringing-in device 62 having wheels 61, which
bring in the repairing device 7 to the annulus 10 thorough a
recirculating piping 60 (=72).
[0160] The bringing-in device 62 constituted by coupling multiple
carriages, which are provided with the wheels 61. This constitution
allows bending the device freely, thereby smoothly passing through
bent parts in the recirculating piping 60, resulting in bringing
in/recovering the repairing device 7 to and from the recirculating
water outlet nozzle 2.
[0161] FIG. 15 illustrates an embodiment where a PT (liquid
penetrant flaw detection) device is installed on the repairing
device 7.
[0162] As described in FIG. 17, the annulus 10 is a space
surrounded by the shroud support cylinder 40 and the baffle plate
41 in a circular shape. Since the annulus 10 is not especially
provided with drain holes, tends to accumulate water, and is
narrow, it is extremely difficult to dispose solution resulting
from clearing the liquid penetrant for detecting flaws applied for
the PT.
[0163] In the embodiment described in FIG. 15, a circular airbag 48
including an air joint 49 is provided around an application nozzle
50 attached to the repairing device 7. A cleaning nozzle 51 and a
suction nozzle 52 are operated inside the airbag 48.
[0164] The airbag 48 is pressed to a part to be repaired, which
requires inspection, to form an enclosed space around the part to
be repaired, thereby eliminating the diffusion of liquid before the
PT inspection. When the applied liquid is removed or cleaned, the
suction nozzle 52 sucks the liquid to remove.
[0165] With this embodiment, the spatter and diffusion of the
liquid penetrant or cleaning liquid over a wide area other than the
part subject to repairing is prevented, thereby eliminating the
necessity for placing a cleaning device or the like in a separated
place.
[0166] FIG. 16 shows an embodiment where an electric discharge
machining device, which is operable in the air, is attached on the
repairing device 7 relating to the present invention.
[0167] As described before, it is difficult to operate the
repairing device in the water remotely from the top of the reactor
pressure vessel. Also, since it is difficult to suck to dispose
machining chips resulting from the electric discharge machining,
the machining chips left on the bottom of the vessel after draining
obstructs the operation.
[0168] In the embodiment in FIG. 16, the circular airbag 48 is
provided around an electrode for electric discharge machining 53 of
an electric discharge machining device as in the embodiment in FIG.
15, and a machining liquid injection nozzle 54 and a suction nozzle
55 are provided in the airbag 48. For electric discharge machining,
the airbag 48 is pressed on a part to be repaired to form an
enclosed space around the part to be repaired, machining liquid is
filled in the space, and a motor for adjusting electric discharge
gap 56 rotates a nut on a ball screw 58 through a belt 57.
[0169] Electric discharge operation is conducted while the motor
for adjusting electric discharge gap 56 drives a ball screw shaft
59, which has the electrode for electric discharge machining 53, to
maintain a required electric discharge gap. Simultaneously, the
suction nozzle 55 sucks and removes the machining chips and the
machining liquid, thereby enabling a local electric discharge
machining in the air while keeping the ambient area clean.
[0170] With another embodiment of the present invention, as
described later, a repairing operation from the inside of the
reactor at the top of the reactor pressure vessel in parallel with
the repairing operation from the annulus side as in the embodiment
described before.
[0171] FIG. 18 describes an example of arranging individual
machines for the repairing operation from the inside of the
reactor.
[0172] When the reactor water is drained from the reactor pressure
vessel, a shield is required for operators on the top of the
reactor, as described in the Fig. Preferably, a shield 81a is
installed on the RPV flange 82, and more preferably, a shield 81b
is installed on the RPV flange 82 and the shroud top flange 83. A
guide pipe 84 for installing the repairing device is installed on
the bottom of the reactor.
[0173] Up to now, the operation is conducted in well-drain state
(water is filled in the reactor pressure vessel). Now the reactor
water is drained, and the following installing operation is
conducted without water.
[0174] A cable handling device 86 is installed on an operation
carriage 87, and is moved over the reactor pressure vessel 1.
[0175] The cable handling device 86 is provided with a chain
winding-up machine and a cable handling machine. The chain
winding-up machine winds up/off a chain 85 for suspending a device.
The cable handling machine winds up/off a cable connected to the
device as the chain 85 moves up/down.
[0176] The chain 85 with strength required for supporting a load of
the device to be brought into the reactor is used. The cable is
connected to a control panel 88 on an operation floor.
[0177] A lift carriage 89, which is held for freely lifting up/down
in the guide pipe 84 is attached to the end of the chain 85. The
lift carriage 89 is used to bring the repairing device (not shown
in the Fig.) into the reactor, and to install it.
[0178] FIG. 19 is a flowchart showing typical steps for an
embodiment of the present invention for the repairing method for
the inside of the reactor pressure vessel allowing repairing from
the both the annulus side and the inside of the reactor. A
repairing device is brought in the opening either on the
recirculating piping, the recirculating water outlet nozzle or the
recirculating nozzle safe end. Also, another repairing device is
brought in from the inside of the reactor from the top of the
nuclear reactor through a guide pipe.
[0179] In FIG. 19, individual processes of S1 to S7, 59, S10, and
S13 to S18 are identical to the embodiment described in FIG. 1. The
description below also includes these processes.
[0180] The following section uses FIG. 19 with reference to FIG.
17.
[0181] A process of removing the RPV head 95 from the reactor
pressure vessel 1, i.e. nuclear reactor opening process S1
starts.
[0182] The nuclear reactor well 94 is filled with water to reduce
radiation exposure (S2). The machines inside the reactor such as
the dryer 43 and the separator 44, and the nuclear fuel assembly 96
are removed from the reactor pressure vessel 1, and are taken out
from the top (S3). Depending on the condition, a process for
draining the water in the nuclear reactor well 94, i.e. well
draining S4 is conducted.
[0183] The annulus 10 is inspected with VT (visual inspection)
(S5). If a defect is found (S6), UT (ultrasonic flaw detecting
inspection) is used to check the position and the extent of the
defect. EDM (electric discharge machining) is employed to remove
the defect. UT (ultrasonic flaw detecting inspection) is used to
check if the defect is removed (S7).
[0184] The all devices used in this step are brought in from the
top of the reactor.
[0185] The shield 81a and 81b are installed on the face of the RPV
flange 82 and the face of the shroud top flange 83 for repairing
from the inside of the reactor as described in FIG. 18 (S21). The
guide pipe 84 is installed in the water (S22).
[0186] The reactor water in the pressure vessel is drained (S9) to
enter an aerial state.
[0187] The process is divided into a process in the annulus side
identical to those in FIG. 1 (S10, S26, S27), and a process in the
inside of the reactor described to the right of the Fig. (S23, S24,
S25). As the result, these processes are conducted in parallel.
This is one characteristic of the embodiment of FIG. 19. However
these processes may be conducted in serial.
[0188] First, the process in the inside the reactor (S23, S24, S25)
is described. For this process, at least one monitoring camera is
installed for monitoring the entire repairing operation (S23).
[0189] This process for installing monitoring cameras may be
conducted in the process on the annulus side (S10, S26, S27). In
this case, the number of installations may be minimized or the
process may be skipped.
[0190] The repairing device is brought in from the inside of the
reactor through the guide pipe 84, and the repairing operation is
conducted (S24). After the operation, the repairing device is
brought out from the guide pipe 84 in the same manner (S25), and
the process continues to S13.
[0191] Now, the process in the annulus side (S10, S26, S27) is
described. An opening 3 is produced by cutting any two parts of the
recirculating water outlet nozzle 2, the recirculating water outlet
nozzle safe end 71, and the recirculating piping 72 (S10).
[0192] The monitoring camera and the prescribed repairing device
are sequentially brought into the reactor pressure vessel 1 from
the opening 3. The repairing device brought in is used to conduct
prescribed PT inspection, welding, polishing, and PT inspection
after welding (S26). The process of S26 is identical to S11 in the
embodiment in FIG. 1.
[0193] The repairing device is brought out from the opening 3
(S27). The process of S27 is also identical to S12 in the
embodiment in FIG. 1.
[0194] Also, the process continues to S13.
[0195] After the repairing on the annulus side and the inside the
reactor are completed, i.e. the process of S25 and the process of
S27 are finished, the recirculating water outlet nozzle 2, the
recirculating water outlet nozzle safe end 71, and/or the piping
72, which are previously cut are coupled (S13). The pressure vessel
1 is filled with water (S14).
[0196] The guide pipe described in FIG. 18 is removed (S28). The
shields 81a, 81b are removed (S29). The nuclear reactor well 95 is
filled with water (S15). Removed machines inside the reactor
including the nuclear fuel assembly 96 are returned to the pressure
vessel 1, and are installed (S16). Water is drained from the
nuclear reactor well 96 (S17). The RPV head 95 is installed
(S18).
[0197] With the embodiment in FIG. 19, as described before, the
repair operation is conducted almost in parallel in the annulus
side and inside of the reactor, thereby reducing the operation
period, and a repairing operation which is difficult to conduct
from only one side of the pressure vessel can be conducted from the
both sides.
[0198] FIG. 20 exemplifies a repairing operation when the baffle
plate 41, which is one of the structures in the reactor facing the
annulus 10, is repaired in accordance with the embodiment described
in FIG. 19. FIG. 20 is an example of an arrangement of the machines
when the repairing from the inside of the reactor described in FIG.
18.
[0199] As described before, the repairing device 7 brought in from
the recirculating water outlet nozzle 2 repairs on the annulus 10
side.
[0200] The repairing device in the inside of the reactor 92 through
the guide pipe 84 repairs on the inside of the reactor 91.
[0201] With this embodiment, the individual repairing devices 7,
92, which are brought in, repair from the both the annulus side and
the inside of the reactor alternately or simultaneously. This
enables to repair the same position from the both sides when
repairing from one side is difficult, such as a defect passing
through the annulus and the inside of the reactor, or a deep defect
on one side which is difficult to be repaired from that side.
[0202] When the repairing device 7 for the annulus side is brought
in from the top of the reactor through the guide pipe 84, which is
not described in a drawing, repairing is conducted in the device
arrangement identical to that described above.
[0203] The present invention especially reduces the number of
operations for raising/lowering water level when at least either a
reactor pressure vessel or a structure in the reactor is repaired
while the nuclear power plant is in service, thereby reducing the
operation period and facilitating the positioning for the
device.
[0204] The present invention also eliminates waterproof capability
for a repairing device, thereby simplifying the structure, and
simultaneously restraining a distance traveling in an area with a
high radiation dose to the required minimum when the repairing
device is installed in an annulus, thereby reducing the time for
installing the repairing device, resulting in minimizing the
capability degradation of the repairing device caused by
radiation.
[0205] The present invention allows repairing from both an annulus
side and an inside of a reactor, thereby repairing a wide area
reliably, efficiently and healthfully.
[0206] As the result, the present invention enables an efficient
repairing when repairing a structure in the annulus is required,
thereby maintaining the health of the plant, resulting in
contributing to the safety and the stability of the operation of
the nuclear power plant.
* * * * *