Note: Descriptions are shown in the official language in which they were submitted.
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ANNULAR FOREIGN OBJECT SEARCH AND RETRIEVAL APPARATUS
CRO~S-RB~'BRENCB ~o RELa~ED APPLIC~TIO~B
This application is a continuation-in-part of
commonly assigned Application Serial No. < 7/303,2 =,
filed January 27, 1989, in the name of Robert A.S. Lee,
which is in turn a continuation in-part of commonly
assigned Application Serial No. 07/027,810, filed March
18, 1987, in the name of Ro~ert A.S. Lee, now U.S. Patent
4,827,953, both entitled "Flexible Lance for SteaM
Generator Secondary Side Sludge Removal." This
application is further a continuation-in-part of commonly
assigned Application Serial No. 07/314,091~ filed
February 22, 1989, in the names of Steven K. Ruggieri,
Stephen C. Jens and Robert Sykes, and entitled "Flexible
Lance and Drive System." This application is also a
continuation-in-part of commonly assigned Application
Serial No. 07/ , , filed February 27, 1991 in the
names of Stephen C. Jens, ~ichael W. Osborne, Paul F.
Viola, Christos Athanassiu and Robert A.S. Lee, and
entitled "In BundIe Foreign Object Search and Retrieval
-A~paratus."
BACKGROUND OF THE INVENTION
1. Field of the_Tnvention:
The present invention relates generally to a robotic
system that is useful in nuclear power plants and other
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structures with a difficult to access geometry. More
particularly, it relates to such a system which is
capable of locating and removing foreign objects that
have been accidentally introduced into such structures
with a difficult to access geometry, such as in the
annularspace surrounding tube bundles ofa nuclearpower
plantls steam generators.
2. Description of the Prior Art:
Nuclear power generation equipment consists of two
major parts, the reactor and the steam generator. The
steam generator includes a heat exchanger, which, in
simple terms, consists of a bundle of thin wall tubes,
which aré tightly spaced and arranged in a matrix-like
fashion. The spacing between the tubes is less than 0.5
inches, and the tube height extends to many feet. Hot
reactor coolant is pumped through the tubes, which in
turn heats water under pressure above the boiling point
to several hundred degrees, thus generating steam.
During reactor shut down for refueling or any other
reas~n, repair and maintenancetechnicians enter YariOUS
areas, one of which is the steam generator housing.
During such entry, accidental dropping of such items as
welding rods, washers, screws and the like is possible.
Such items can cause damage to the thin wall tubes if
they are not retrieved. Repairing, replacing orplugging
such damaged tubes is very expensive, both in terms of
the labor involved and required reactor shut down. To
date, it has been difficult to retrieve such items, due
to the physical constraints of the steam generator
geometry and the presence of radiation.
When a lance is introduced into the tube bundle,
the lance is laterally supported by the tube bundle, and
it can therefore be extended into the tube bundle
substantially further than it could be extended without
falling over in the absence of such lateral support.
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Such lateral support is not provided in the annular space
surrounding the tube bundle. A lance intended for
introduction into the annular space therefore requires
substantially more structural integrity while retaining
flexibility to move within the confines of the annular
space than a lance that is intended for introduction into
the tube bundle, such as the lance disclosed in the last
above mentioned parent application.
U.S. Patent 4,638,667, issued January 27, 1987 to
Zimmer et al. discloses a remote probe positioning
apparatus including a flexible tape which has an optical
fiber cable running the length of the tape and a
retractor tool at a distal end of the tape. However,
no details are given on the construction and operation
of the retractor tool. Further development is therefore
required in order to provide a system for removing
foreign objects which will meet the needs of nuclear
power plant steam generator genmetry and similar
difficult to access geometries, especially ~or use in
the annular space around the tube bundle in the steam
generator geometry.
SUMM~RY OF ~HE INVENTION
Accordingly, it is an object of this invention to
provide a system for finding and retrieving foreign
objects in a difficult to access geometry, such as the
annulus of a nuclear power plant steam generator.
It is a further object of the invention to provide
a flexible lance for accessing a difficult to access
geometry which has sufficient flexibility to negotiate
into the difficult to access geometry, but sufficient
structural integrity 50 that it can be extended for
substantial distances into the difficult to access
geometry without lateral support.
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The attainment of these and related objects may be
achieved through use of the novel annular foreign object
search and retrieval apparatus herein disclosed. An
annular foreign object search and retrieval apparatus
in accordance with this invention has a stiff, non-
buckling lance for accessing an assembly having a dif-
ficult to access geometry. The lance comprises a stiff,
non-buckling member having a distal encl. An optical
cable extendslengthwise along andwithin the stiff, non
buckling member for illuminating a portion of the
difficult to access geometry. A video cable also extends
lengthwise along and within the stiff, non-buckling
member. A video camera is connected to the video cable
at the distal end of the stiff, non-buckling member for
forming an image of a scene visible ~rom the distal end
of the stiff, non-buckling member for transmission by
the video cable. A retractor tool is mounted at the
distal end of the stiff, non-buckling member. At least
one actuating cable for the retractor tool extends
lenythwise along and is free to move within the stiff/
non-buckling member. The stiff, non-bucking member is
configured to be driven into the difficult to access
geometry. A rigid guide extends lengthwise of the stiff,
non-buckling member. The stiff, non-buckling member is
Z5 movably mounted along the rigid guide. The rigid guide
has an end positioned to turn the stiff, non-buckliny
member in a predetermined angle with respect to an
extending direction of the stiff, non-buckling member
as the stiff, non-buckling me~ber passes from the rigid
guide through the end. A drive means drives the stiff,
non-buckling member through the rigid guide. The atiff,
non-buckling member comprises separate segments strung
on at least one flexible cable which runs the length of
the stiff, non-buckling member. The stiff, non-buckling
member has sufficient flexiblility to curve laterally
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in the difficult to access geometry and sufficient
stiffness to extend suspended in cantilever fashion when
extended in the difficult to access geometry without
substantial lateral support.
The attainment o~ the foregoing and related objects,
advantages and features of the invention should be more
readily apparent to those skilled in the art, after
review of the following more detailed description of the
invention, taken together with the drawings, in which:
BRIEF DESCRIPTION OF T~E D~A~INGS
Figure 1 is a perspective view, partly in cross-
section of a portion of an annular foreign object search
and retrieval apparatus in accordance with the invention.
Figure 2 is an enlarged side view of the area 2 in
Figure 1.
Figure 3 is an enlarged perspective view of a front
portion of a flexible lance of the apparatus.
Figure 4 is an enlarged perspective view similar
to that of Figure 3, but with a portion of the flexible
lance in a different position.
Figure 5 is a perspective viewl partially in
phantom, showing positioning of the flexible lance of
Figures 3-4.
Figure 6 is a perspective view of a portion of the
flexible lance of Figures 3-5.
Figure 7 is a plan view showing details of a portion
of the apparatus of Figure 1.
Figure 8 is a perspect~ve view of a control panel
for the apparatus of Figure 1.
DETAILED DE8CRIPM ON OF T~E INVEN~ION
Turning now to the drawings, more particularly to
Figure 1, there is shown an apparatus 10 for foreign
object search and retrieval in annular space 12 around
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a tube bundle 14 of a nuclear power steam generator 16.
A lance drive 18 through which a stiff, nonbuckling lance
20 extends has a nose piece 22 extending into handhole
24 of the steam generator 16. The lance drive 18 is
mounted in front of the handhole 24 by a support rail
26 to which the lance drive 18 is mounted. A lance guide
28 is connected between rear 30 of the lance drive 18
and a lance takeup drum 32. The lance takeup drum 32
is mounted on one side of the lance drive 18, with
counterweights 33 for the takeup drum on the other side
of the lance drive 18. The lance drive 18 is as
described in the above predecessor Lee, Serial No.
07/303,268 application and Ruggieri et al. application,
the disclosures of which are hereby incorporated by
reference herein. In place of an internal guide member
in th~ lance drive as described in those applications,
the lance drive 18 has the external nosepiece 22 serving
as a guide for the stiff, nonbuckling lance 20 as it
exits from the lance drive 18. As is shown more clearly
in Figure 2, the nosepiece 22 has a series of roller
bearings 36 through which the stiff, nonbuckling lance
20 passes to curve it into the annular space 12. The
lance drive 18 provides two degrees of motion for the
stiff, nonbuckling lance Z0, i.e., forward and backward
translation by means of a sprocket drive 21 right behind
the nosepiece 22, and rotation about the handhole 24
centerline, by rotation of the lance drive 18 with an
enclosed gear drive (not shown)~
Details of the stiff, nonbuckling lance 20 are shown
in Figures 3-6. As in the case of the flexible lance
shown in the predecessor Ruggieri, Serial No. 07/314,091
application, the stiff, nonbuckling lance 20 consists
of a plurality of substantially vertically extending,
one piece hosebar supports38 strung on supporting cables
40 in a manner similar to beads on a string. As is best
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shown in Figure 6, each of the hosebar supports 38 has
a convex front surface 42 and a concave rear surface 44.
The convex front surface 42 of the hosebar supports 38
fits into the concave rear surface 44 of the next
adjacent hosebar support 38. With the surfaces 42 and
44 engaging in this manner, the sti~f, nonbuckling lance
20 has a substantially increased vertical stiffness, so
that it can extend for substantial distances ~rom the
nosepiece 22 into the annular space 12 without lateral
support. The interlocking feature of the hosebars 38
allows them to support the bending and twisting loads
when the lance 20 is extended 100 inches.
In addition to the support cables 40, a positioning
cable 46 (Figure 4) for gripper 48 extends through the
hosebar supports 38 and is attached to base 49 of the
gripper 48~ Pulling on the positioning cable 46 mo~ s
the gripper 48 from the position shown in Figure 4 to
the position shown in Figure 3. ~prings 50 (Figure 3)
oppose the upward motion of the gripper 48, so that the
position shown in Figure4 representsthe normalposition
of the gripper 48 when force on the positioning cable
46 is released. An actuating cable 52 for the gripper
48 also extends through the hosebar supports and is
attached to gripper fingers 54. The gripper fingers 54
are spring loaded in their closed position. Pulling on
the actuating cable 52 opens the fingers 54, and
subsequently releasing the actuating cable 52 allows the
fingers to close on an object to be grasped for remova:L
from the annular space 12.
Steering cables 56 for the stiff, nonbuckling lance
20 are provided on either side of the stiff, nonbuckling
lance, and are interwoven among khe first 18 hosebar~
38, i.e., pass alteratively in front of a portion of a
hosebar and behind the portion on an adjacent hosebar,
on the distal end of the stiff, nonbuckling lance, as
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best shown in Figure 4. Pulling on the steering cables
56 will move the distal end to the left and right, as
indicated in Figure 5.
In the stiff, nonbuckling lance 20, the hosebars
38 are made of different materials than in the Ruggieri
et al. application. A rigid nylon plastic was used ~or
the hosebars in the Ruggieri et al. application. The
hosebars 38 are made of aluminum and stainless steel.
Aluminum hosebars 38 are used for the first 48 inches
of the stiff, nonbuckling lance 20 from the distal end,
and for the last 42 inches, for both weight and cost
reasons. The remainingportion ofthe stiff, nonbuckling
lance 20, to give a total length extended from the
nosepiece 22 of 165 inches, is formed from stainless
steel hosebars 38 for added strength. The aluminum and
stainless steel construction provides the torsional
stiffness to support the loads when the lance 20 is fully
extended.
To allow visual inspection in the annular space 12,
a Welch Allyn Videoprobe minature video camera and light
source 60 is mounted in block 62 at the distal end of
the stiff, nonbuckling lance 20. Light for the light
source and electrical signals to and from the video
camera are transmitted by a fiber optic and electrical
cable 64.
Details of actuator package 70 inside the takeup
drum 32 for the stiff, nonbuckling lance 20 are shown
in Figure 7. The control of the lance sweep and end
effector tilt and grapple is performed by linear
actuators 72 and potentiometers 74 in take up reel 75.
As ~hown, there are four linear actuators 72 and two
potentiometers 74 used to actuate and control the lance
and end effector motion. The stiff, nonbucklin~ lance
is coiled around the take up reel 75 when it is not
extended into the annular space 12.
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Figure 8 shows a control panel 80 for the appaxatus
10. The control panel includes a knob 82 connected to
a rotary shaft encoder for controlling sweep of the lance
20 distal end from left to right by pulling on one of
the steering cables 56, as determined by xotation of the
knob 82. A pair of joysticks 84 and 86 respectively
control tilting of the gripper 48 upward and downward
and opening and closing of the fin~ers 54, by pulling
on, respectively, positioning cable 46 and actuating
cable 52.
In use, the lance 20 supports the gripper 48 above
the floor 49 ~called the tube sheet) of the annular space
12. The gripper 48 effectively hovers above the tube
sheet as the lance drive 18 pushes and pu115 the lance
around the annulus 12. The gripper 48 has three degrees
of freedom, i.e., side to side sweep of the lance 20 end,
up and down tilt of the gripper 48, and opening and
closing of the fingers 54.
It should now be readily apparent that an annular
foreign object search and retrieval apparatus capable
of achieving the stated objects of the invention has been
provided. ~he system will find and retrieve ~oreign
objects in a difficult to access geometry, such as the
annular space surrounding the in bundle area of a nuclear
power plant steam generator. The lance for accessing
a difficult to access geometry of this system has
sufficient flexibility to negotiate into the difficult
to access geometry, but sufficient structural integrity
so that it can be extended for substantial distances into
the difficult to access geometry without lateral support.
It should further be apparent to those skilled in
the art that various changes in form a~d details of the
invention as shown and described may be made. It i5
intended that such changes be included within the spirit
and scope of the claims appended hereto.
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