Induced nuclear reactions: processes – systems – and elements – Handling of fission reactor component structure within... – Fuel component
Reexamination Certificate
1998-06-11
2002-12-31
Carone, Michael J. (Department: 3641)
Induced nuclear reactions: processes, systems, and elements
Handling of fission reactor component structure within...
Fuel component
C376S260000, C376S264000, C376S266000
Reexamination Certificate
active
06501813
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control rod/fuel support grapple and, more particularly, a control rod/fuel support grapple which is capable of picking up simultaneously control rods and a fuel support in a boiling water reactor (referred to as a “BWR” hereinafter).
2. Description of the Related Art
FIG. 8
is a vertical sectional view showing a part of the core of the BWR. As shown in
FIG. 8
, a cylindrical core shroud
2
is provided in an inside of a reactor pressure vessel
1
and a plurality of fuel assemblies
3
are loaded in the core shroud
2
. A plurality of control rods
4
each having a cruciform lateral sectional shape are arranged vertically movable in clearances between the fuel assemblies
3
. Each of the control rods
4
has a hoist handle
4
d
at its top end. Core reactivity can be controlled by moving up and down these control rods
4
in the core.
A top end of the fuel assembly
3
is supported by an upper grid
5
. A bottom end of the fuel assembly
3
is supported by a core support plate
7
via a fuel support
6
.
FIG. 9
is a perspective view showing a part of the upper grid
5
of the BWR. As shown in
FIG. 9
, a plurality of grids into which the top ends of a plurality of fuel assemblies
3
are inserted respectively are formed on the upper grid
5
.
As shown in
FIG. 10
, a plurality of fuel support sustaining holes
7
a
are formed in the core support plate
7
, and the fuel supports
6
can be supported by the core support plate
7
by inserting their cylindrical bottom portions into the sustaining holes
7
a
respectively. As shown in
FIG. 11
, for example, sustaining holes
6
a
,
6
b
,
6
c
,
6
d
and a cruciform shaped through hole
4
a
are formed on a substantially square cylinder type upper surface portion of the fuel support
6
. Then, bottom portions of four fuel assemblies
3
can be inserted into the sustaining holes
6
a
,
6
b
,
6
c
,
6
d
respectively and then supported thereon. The cruciform control rod
4
can be moved vertically through the cruciform through hole
4
a.
The sustaining holes
6
a
,
6
b
,
6
c
,
6
d
of the fuel support
6
are connected to orifices
6
e
,
6
f
,
6
g
,
6
h
formed on a side peripheral wall of the fuel support
6
respectively such that coolant is supplied from the orifices
6
e
,
6
f
,
6
g
,
6
h
to the fuel assemblies
3
via the sustaining holes
6
a
,
6
b
,
6
c
,
6
d
respectively. In addition, a slot
6
i
into which a fixing pin
7
b
(provided on the core support plate
7
) is inserted is formed on an upper corner portion of the fuel support
6
. The fuel support
6
can be fixed to the core support plate
7
via the slot
6
i.
Also, as shown in
FIG. 8
, a plurality of control rod drive mechanisms (CRDs)
8
are provided so as to pass through a bottom portion of the reactor pressure vessel
1
vertically. The control rods
4
are detachably attached to the control rod drive mechanisms
8
respectively. Top ends of a plurality of control rod guide tubes
9
are coupled to the core support plate
7
. The fuel supports
6
are arranged on the top ends of the control rod guide tubes
9
respectively. The control rod
4
can be driven vertically by the control rod drive mechanism
8
such that the control rod
4
can be inserted into or withdrawn from the core through the inside of the control rod guide tube
9
and the cruciform through hole
4
a
of the fuel support
6
.
As shown in
FIG. 12
, the control rod
4
and the control rod drive mechanism
8
are coupled with each other by a spud coupling type coupling mechanism. More particularly, they are coupled via a spud coupling
10
. A coupling spud
11
whose periphery is divided by cuttings to form quartered latching pawls, for example, is pushed upward by a drive piston (not shown) of the control rod drive mechanism
8
. The coupling spud
11
can be tightly pushed into a clearance formed on the out side of a periphery of a lock plug
12
which is inserted into the fitting holes of a lower end
4
b
of the control rod
4
. As a result, the coupling spud
11
is supported by both an inner peripheral surface of the lower end
4
b
of the control rod
4
and an outer peripheral surface of the lock plug
12
, so that the control rod
4
and the control rod drive mechanism
8
can be coupled with each other.
There are two methods of uncoupling the control rod
4
and the control rod drive mechanism
8
, i.e., one is such a method that can be applied from a pedestal side of the bottom portion of the reactor and the other is such a method that can be applied from an upper side of the reactor. In the event that the releasing operation is applied from the pedestal side of the bottom portion of the reactor, as shown in
FIG. 12
, the lock plug
12
is pushed upward by an uncoupling rod
13
of the control rod drive mechanism
8
against a spring force of a spring
4
c
, whereby a coupled state of the control rod
4
and the control rod drive mechanism
8
are uncoupled.
In turn, in the event that a releasing operation is applied from the upper side of the reactor, at first the fuel assembly
3
is pulled up from the core. Then, the fuel support
6
can be pulled up from the core by means of a manipulating tool which can manipulate the fuel support
6
. Then, the manipulating tool can be replaced with a dedicated control rod latch tool which can hold the control rod
4
and then release the control rod
4
and the control rod drive mechanism
8
. They can be released by operating a release handle
20
(latching handle)
4
e
(see
FIG. 8
) of the control rod
4
by use of this control rod latch tool, and thereafter the control rods
4
can be pulled up from the core.
At any rate, during a periodical inspection of the BWR, both reduction in working time and reduction in operator's exposure are desired. An exchange operation of the control rods
4
is not an exception.
In the related art, in order to reduce a time required for the exchange operation of the control rods, at first an uncoupling operation (coupling releasing operation) of the control rod and the control rod drive mechanism is carried out from the pedestal side of the bottom portion of the reactor by using the control rod drive mechanism, and then the control rods and the fuel support are picked up simultaneously from the core from the upper side of the reactor by using the conventional control rod/fuel support grapple, whereby the exchange operation of the control rods is performed.
However, as described above, in the exchange operation of the control rods by use of the control rod/fuel support grapple method in the related art, since at first the uncoupling operation of the control rod and the control rod drive mechanism has been carried out from the pedestal side of the lower portion of the reactor by using the control rod drive mechanism and then the control rods and the fuel support have been picked up from the core simultaneously from the upper side of the reactor by using the conventional control rod/fuel support grapple, two stage operations have been required which causes a longer working term.
In addition, in the event that the uncoupling operation of the control rod and the control rod drive mechanism is applied from the pedestal side of the bottom portion of the reactor, there has been a problem of the operator's exposure in the related art. For this reason, it has been requested that the operator's exposure would be reduced by executing the exchange operation of the control rods without the operation conducted at the bottom portion of the reactor.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a control rod/fuel support grapple (abbreviated as a “CR/FS grapple” hereinafter) which is capable of pulling up simultaneously control rods and a fuel support and also carrying out an uncoupling operation of the control rod and a control rod drive mechanism.
In order to achieve the above object, according to the present invention, there is provided a control ro
Sakamaki Kazuo
Soma Koichi
Carone Michael J.
Foley & Lardner
Kabushiki Kaisha Toshiba
Keith Jack
LandOfFree
Control rod/fuel support grapple does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Control rod/fuel support grapple, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Control rod/fuel support grapple will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2925355