CA1094127A - Extension shaft latching mechanism for a nuclear reactor control rod lift rig - Google Patents
Extension shaft latching mechanism for a nuclear reactor control rod lift rigInfo
- Publication number
- CA1094127A CA1094127A CA309,925A CA309925A CA1094127A CA 1094127 A CA1094127 A CA 1094127A CA 309925 A CA309925 A CA 309925A CA 1094127 A CA1094127 A CA 1094127A
- Authority
- CA
- Canada
- Prior art keywords
- latch member
- latch
- recited
- cylinder
- lifting rig
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C19/00—Arrangements for treating, for handling, or for facilitating the handling of, fuel or other materials which are used within the reactor, e.g. within its pressure vessel
- G21C19/02—Details of handling arrangements
- G21C19/10—Lifting devices or pulling devices adapted for co-operation with fuel elements or with control elements
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Load-Engaging Elements For Cranes (AREA)
- Monitoring And Testing Of Nuclear Reactors (AREA)
Abstract
EXTENSION SHAFT LATCHING MECHANISM FOR
A NUCLEAR REACTOR CONTROL ROD LIFT RIG
ABSTRACT
A lift rig for lifting control rods from a nuclear reactor prior to its refueling. The lift rig includes a plurality of latching mechanisms which automatically latch to a control rod when the mechanism is lowered down around its top. Once latched, the mechanism will not release until an unlatching step is in-tentionally performed. The mechanism includes two concentric cy-linders moveable relative to each other with a latch pivotally suspended therebetween. Relative movement of the cylinders causes the latch to move between a projecting, latched position and a retracted, unlatched position.
A NUCLEAR REACTOR CONTROL ROD LIFT RIG
ABSTRACT
A lift rig for lifting control rods from a nuclear reactor prior to its refueling. The lift rig includes a plurality of latching mechanisms which automatically latch to a control rod when the mechanism is lowered down around its top. Once latched, the mechanism will not release until an unlatching step is in-tentionally performed. The mechanism includes two concentric cy-linders moveable relative to each other with a latch pivotally suspended therebetween. Relative movement of the cylinders causes the latch to move between a projecting, latched position and a retracted, unlatched position.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a lifting apparatus for engaging and lifting control rods out of the core of a nu-clear reactor. More specifically~ the present invention relates to a lifting rig for simultaneously lifting all of the control rods out of the core of a nuclear reactor prior to core refueling or other fuel removing operations.
It has been standard practice in the art of nuclear reactor power plant operation to annually remove and replace at least one third (1/3) of the fuei assemblies in a nuclear core.
This operation perforce is performed while the reactor is shutdown.
Refueling operations may thus represent a significant loss in . _. .
': .: :: ~ : ,,~' , . . ~ `. ' -...
revenue to the operating utility since not only is power not being generated for the utility's own use and for sale to other utilities, but it is also often the case that during such a shutdown, the utility must buy power from other utilities to supply its own cus-tomer's needs.
In order to expose the nuclear fuel assemblies in the core for their withdrawal and replacement, it is necessary to re-move all obstructions From above the core including the reactor pressure vessel head, control rod drive mechanisms and other upper support structures, as well as the protective shrouds and calandria found in some reactors. Li-Ft rigs have usually been designed to perform much of this apparatus removal. In addition, conventional procedure includes the removal of all of the control rods from the core prior to refueling after borating the coolant in the core to prevent criticality. Obviously, the longer these steps each take, the longer will be the refueling outage and the larger will be the economic loss experienced by the utility. There is therefore a significant need for apparatus and techniques for accomplishing each step as expeditiously as possible withou-t creating the posi-bility of error.
In previous procedures and with prior Icnown apparatus, an operator would manipulate each of the control rods individually and either remove each control rod one by one or individually at-tach each control rod to an attachment device on the bottom plate of the lift rig. Not only was this procedure laborious and time consuming, but it also unnecessarily exposed the personnel in the plant to a significant man rem radiation exposure which should desirably be minimized or, if at all possible, eliminated.
~UMMARY '~F THE'INVEN~ION
The present invention addresses the problems inherent in the refueling control rod removal procedure by providing a lit rig with a plurality of self actuating latch mechanisms attached to its floor plate. With the lift rig and latching mechanisms of the present i,nvention, the control rod removal procedure includes t~e step of lowering the lift rig until each control rod has been inserted into its respectïve latching mechanism, at ~h.~ch. point each control rod is automatically 1~ g.rasped by the respective mechanism, and the step of lifting the lift rig a~a~ from the core to thereby withdraw all of the control rods from the core.
Thls simpli~i.ed control rod removal procedure is made possible b~ the li~t rig of the present invention which comprises a. a base plate oriented trans.versely of said contxol rods; and b. a plurality of latching mechanisms fixed to and depending ~rom sai.d bas:e plate, each.of sai.d latching mechanisms comprising:
1. a support member attached to said base plate;
The present invention relates to a lifting apparatus for engaging and lifting control rods out of the core of a nu-clear reactor. More specifically~ the present invention relates to a lifting rig for simultaneously lifting all of the control rods out of the core of a nuclear reactor prior to core refueling or other fuel removing operations.
It has been standard practice in the art of nuclear reactor power plant operation to annually remove and replace at least one third (1/3) of the fuei assemblies in a nuclear core.
This operation perforce is performed while the reactor is shutdown.
Refueling operations may thus represent a significant loss in . _. .
': .: :: ~ : ,,~' , . . ~ `. ' -...
revenue to the operating utility since not only is power not being generated for the utility's own use and for sale to other utilities, but it is also often the case that during such a shutdown, the utility must buy power from other utilities to supply its own cus-tomer's needs.
In order to expose the nuclear fuel assemblies in the core for their withdrawal and replacement, it is necessary to re-move all obstructions From above the core including the reactor pressure vessel head, control rod drive mechanisms and other upper support structures, as well as the protective shrouds and calandria found in some reactors. Li-Ft rigs have usually been designed to perform much of this apparatus removal. In addition, conventional procedure includes the removal of all of the control rods from the core prior to refueling after borating the coolant in the core to prevent criticality. Obviously, the longer these steps each take, the longer will be the refueling outage and the larger will be the economic loss experienced by the utility. There is therefore a significant need for apparatus and techniques for accomplishing each step as expeditiously as possible withou-t creating the posi-bility of error.
In previous procedures and with prior Icnown apparatus, an operator would manipulate each of the control rods individually and either remove each control rod one by one or individually at-tach each control rod to an attachment device on the bottom plate of the lift rig. Not only was this procedure laborious and time consuming, but it also unnecessarily exposed the personnel in the plant to a significant man rem radiation exposure which should desirably be minimized or, if at all possible, eliminated.
~UMMARY '~F THE'INVEN~ION
The present invention addresses the problems inherent in the refueling control rod removal procedure by providing a lit rig with a plurality of self actuating latch mechanisms attached to its floor plate. With the lift rig and latching mechanisms of the present i,nvention, the control rod removal procedure includes t~e step of lowering the lift rig until each control rod has been inserted into its respectïve latching mechanism, at ~h.~ch. point each control rod is automatically 1~ g.rasped by the respective mechanism, and the step of lifting the lift rig a~a~ from the core to thereby withdraw all of the control rods from the core.
Thls simpli~i.ed control rod removal procedure is made possible b~ the li~t rig of the present invention which comprises a. a base plate oriented trans.versely of said contxol rods; and b. a plurality of latching mechanisms fixed to and depending ~rom sai.d bas:e plate, each.of sai.d latching mechanisms comprising:
1. a support member attached to said base plate;
2. an elongated latch member having first and second ends pivotally mounted at said first end to said support member ~or pi,vo~al movement between a laterally :
projecting substantially horizontal position and a laterally retracted position, s-ai.d latch member having a porkion at said second end adapted to engage said nob of said control rod; and
projecting substantially horizontal position and a laterally retracted position, s-ai.d latch member having a porkion at said second end adapted to engage said nob of said control rod; and
3. actuati.on means operatively connected to said latch. member for yieldin~l~ urgi.ng s,ai,d latch.member into 3~ said laterally projecti.ng position.
~ 3-More particularly, the li.fting is. provided with seIf-latchin~ mechanis-ms that may ~e simply and remotely unlatched ~y an oper~tor only upon performance of an intentional act. Eac~ o~ the latching mechanisms. consists of a pair of concentri`c cylinders, one of ~hich ls removably fastened to the upper surface of the ~loor plate of the lift rig ~.y a $1ange. and the other of whlch'depends from the first.
The cylinders are`mova~le relative to one anothe,r and are ~.ridged at their lo~er ends by a plural~ty o~ toggle latch me~bers each p~votally connected to each of the cylinders. The `'!`
to~le latch~mem~ers are p~votally movable from the "down"
position in which the rod's engaging end projects radially in~ard to eng~ge a k.nob on the top o~ the control rod.
Relat.ive mo~ement bet~ee`n t~.e pair o~ cyli,nders causes the c~l~ndexs to .move the to~gle latch n~embers from their radially in~ard extended posit~on t~ a ral$ed, radi,ally retracted, di~engaged con~i~urat~,on i.n ~hi.ch the control rod is released.
Means is proY.~ded to e~ect reIatlve -3a-' ' movelnent between the cylinders when unlatching is desired. This means may be hydraulic, pneumatic, magnetic, mechanical or o-f any other character suitable For providing the remote unlatching function.
As the lift rig and the latching mechanisms are lowered down over the top end of the control rods, the lower portion of each toggle latch member is penetrated by the upper end of the control rod with the effect that it and the interior cylinder are monlentarily held vertically stationary as the exterior cylinder continues to descend. This action causes the toggle latch member to be pivoted to a semi-vertical position which withdraws the innermost end of the toggle latch member radially outward, thereby permitting the knob end of the control rod to pass by in the upward direction. After the control rod knob has passed, the toggle latch member descends under the influence of gravity to its radially inward projecting and latching position and the control rod is automatically grasped.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawings in which ~ike reference numerals refer to like elements in the several figures and in which:
Figure 1 is an elevational side view of a nuclear re-actor vessel with a portion broken away to show the uppermost ends of the control rods and to show a representation of the lif~
rig of the present invention about to engage the control rods;
Figure 2 is a broken away plan view of the latching mechanism of the invention taken along view lines 2-2 of figure 1;
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Figures 3, 4 and 5 are cross-sectional side elevations of the latching mechanism of the lift rig of the present invention showing imminent engagement of a control rod, complete latching engagement and disengagement respectively; and :
Figure 6 is a cross-sectional view of the latching mechanism of the invention taken along view lines 6-6 of figure 4.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In Figure 1 there is shown a general view of a nuclear reactor 10 consisting of a nuclear core 12 shown in phantom con-tained within a pressure vessel from which the head has been re-moved. As is well known, most nuclear reactors are controlled by the variable insertion and removal of neutron absorbing poison or control rods 22 into and out of the core. The control rods are or-dinarily grouped into a unit called a control element assembly 20 by a connecting spider 24. In at least one design of a nuclear reactor, the individual control rods 22 penetrate into the core through guide tubes 38 of the individual fuel assemblies and are protected above the core from coolant cross-flow forces to which they would otherwise be exposed by a calandria structure 14 con-sisting of upper and lower tube sheets connected by intermediate tubes through which the individual control rods 22 pass. Ordinarily the control element assembly 20 -further consists of a control rod extension 28 which terminates in an upper knob 26 adapted to be gripped by a control rod drive mechanism (not shown). For the purposes of this application, it should be understood that the broad terminology "control rod" is used to include not only the individual control rod elements 22 but also the grouping or gang-ing structures such as spiders 24 and any attached extension rods 28 which will all move in and out of the core as a unit.
.:- . . . : . .................................. .
:, , .: . ., , :
While in practical application there may exist a separate and dis-connectable control rod extension shaft connected to the control rod assembly, for the purposes of this description, the terminology "control rod" will be used -to generally include all of the struc-ture which remains after the control rod drive mechanism has been disconnected and removed with the removal of the pressure vessel head.:
As is apparent from figwre 1, access to the individual fuel assemblies which make up the core 12 of the reactor requires the complete removal o~ calandria 14. This requires the removal of all of the control element assemblies 20. Figure 1 shows a representation of a li-fting rig 30 provided for this purpose which consists of a plate 32 suspended from and lifted by support struts 34. Plate 32 includes a plurality of circular apertures 36 ~best seen in figures 3 and 5) through which the control rod latching mechanisms 40 are slideably inserted.
Control rod latching mechanisms 40 each have a pair of downwardly extending concentric first and second cylindrical mem-bers 50 and 60 with the first cylindrical member 50 mounted exter-ior to the second cylindrical member 60. First cylindrical mem-ber 50 includes an upper flange 58 which is larger in diameter than the opening 36 in plate 32 and which is fastened to plate 32 by means of shoulder bolts 42. The second cylindrical mem-ber 60 also includes an upper flange 68 whose diameter is greater than both the size of the opening 36 in plate 32 as well as the diameter of first cylinder flange 58. Flange 68 includes a plurality of positioning apertures 62 through which extend the plurality of shoulder bolts 42. Hence, shoulder bolts 42 orient : .
. ~. .. . . . .
the second cylindrical member 60 and flange 68 to the first cy-lindrical member 50 and its flange 58. These shoulder bolts also permit cylindrical cylinder 60 and its flange 68 to move up and down axially, the uppermost axial position of which is determined by the head height of bolt 42.
Turning now to an examination of the lower extremities of latching mechanism 40 (as best shown in figures 3, 4, 5 and 6) it can be seen that cylinder 50 incudes an annular inwardly ex-tending ring 51 which narrows the diameter of the interior passage 80 of the lower portion of cylindrical member 50 to a diameter which is slightly larger than the diameter of the upwardly extend-ing portion of control rod 22. Annular ring 51 has an inwardly and upwardly chamfered surface 48 adapted to guide the knob 26 of control rod extension 22 into the interior passage 80 of the latch-ing mechanism 40. Annular ring 51 also includes an upwardly facing support shoulder 52 for supporting the control rod engaging latches 70 in the horizontal position.
Cylinder member 50 further includes a plurality of angularly spaced apertures 56 through its cylindrical wall adapted to receive therewithin the first end of the elongated latch menlber 70. Elongated latch 70 is pivotally fixed to the cylin-drical member 50 by means of a dowel pin 72 which is secured in cylindrical passage 54 of the first cylindrical member 50 (as best seen in figure 6). With this arrangement, latch member 70 is per-mitted to pivot from a substantially horizontal position in which its second end laterally projects into cylindrical passage 80 to a vertically upward laterally retracted position in which the second end of latch 70 has been removed from cylindrical passage 80.
%~
The second cylindrical member 60 interior to the first cylindrical member 50, as seen in figures 3, 4 and 5 necks down to a reduced diameter so that it fits within the constricted por-tion o~ cylinder 50 horizontally adjacent to the position of mount-ing pins 72. Cylinders 60 also include apertures or latch slots 66 through which latoh 70 may extend into the interior cylindrical passage 80 of the latching mechanism 40. In a manner similar to that o~ the first cylindrical member 50, cylindrical member 60 in-cludes a plurality of mounting pins 74 secured in passages 64 for pivotally and slideably engaging the second end of latch 70.
Engagement is provided by means of elongated slot 76 in said second end of latch 70. With this construction, vertical upward movement of cylinder 60 causes pins 74 to cam in slots 76 of latch 70O
thereby lifting the second end of latch 70 and causing latch 70 to pivot in a manner which swings the second end of the latch up-ward and out of its horizontal intruding position in cylindrical passage 80 to a semivertical retracted position.
It is evident from the above description that as plate 32 of the lift rig is lowered down into its control rod engaging position, knobs 26 on the upper extremities of control rods 22 are guided by chamfered surface 48 into the interior passage 80 of the latching mechanism 40. As descent continues, the upper portions of knob 26 come in contact with the lower surFaces of pro-jecting latch members 70 so that latch members 70 are forced to swing upwardly and outwardly to their retracted positions permit-ting knob 26 to pass by. Movement of latches 70 in this manner causes the inner cylindrlcal members 60 to remain temporarily stationary as the outer cylindrical member continues to descend. After knob 26 has completely passed the latches 70, the weight of inner cy-lindrical member 60 causes the cylindrical member 60 and latches .
- : : ,... .. . -. . .
70 to fall down to their lowermost horizontal positions in which they once again project into passage 80, as shown in figure 4.
Subsequent raising of the lift rig 30 moves the upwardly facing bearing surFaces 78 of the horizontally projecting latch members 70 into contact with the lower engagement surface of knob 26. In this control rod engaging position, latch 70 is supported by the upwardly facing shoulder 52 of annular ring 51, so that continued upward movement of the lifting rig causes the control rod 22 to be raised.
After control rod 22 has been engaged and lifted for removal from the core, it is sometimes desirable to disconnect an individual control rod from the lifting mechanism for its inspec-tion and/or replacement. In addition, after the refueling pro-cedure has been accomplished, and the control rods have been re-inserted into the core, it is necessary to be able to cause the latching mechanisms 40 to unlatch from the control rods so that the lifting rig 30 may be removed while leaving the control rods in their core penetrating down positions. Both of these functions are provided by a means which permits the inner cylindrical member 60 to be vertically moved relative to the outer cylindrical member 50 thereby causing latch 70 to swing from its laterally projecting position to its laterally retracted position for control rod release. While any suitable mechanism for causing relative move-ment between cylinder 50 and cylinder 60 may be provided, -the preferred embodiment shown in the figures includes an inflatable torus 44 which is positioned around flange 58 and between floor plate 32 and flange 68. Inflatable torus 44 may be selectively inflated by means of inlet tube 46 through which pressurized air may be delivered. Accordingly, with this arrangement, all of the latching mechanisms 40 can be simulataneously disengaged from their g corresponding control rods 22 by simultaneously inflating all of the respective toruses 44. Alternatively, any selected one latch-ing mechanism 44 can be disengaged from the control rod 22 by the selective inflation of its respective torus.
The above described lift rig as illustrated in the drawings has been designed to include a self-latching latch mech-anism 40 for automatically latching the control rods to the lift rig 30 as the lift rig is lowered. This self-latching feature is activated by gravity alone so that no external power sources are required. Additionally~ the latches are arranged and sized in such a way as to self-center the control rod within the latching mechanisnl 40 to prevent the possibility of jamming or damaging the latches 70 during operation. The latching mechanism 40 can be secured in a locked or unlocked position by use of a simple locking device such as a toggle clamp or a slide bolt arrangement.
Finally, a simple switch or mechanical indicator may be provided to give a positive indication of the latched or unlatched con-dition of the latching mechanism.
--1 o--
~ 3-More particularly, the li.fting is. provided with seIf-latchin~ mechanis-ms that may ~e simply and remotely unlatched ~y an oper~tor only upon performance of an intentional act. Eac~ o~ the latching mechanisms. consists of a pair of concentri`c cylinders, one of ~hich ls removably fastened to the upper surface of the ~loor plate of the lift rig ~.y a $1ange. and the other of whlch'depends from the first.
The cylinders are`mova~le relative to one anothe,r and are ~.ridged at their lo~er ends by a plural~ty o~ toggle latch me~bers each p~votally connected to each of the cylinders. The `'!`
to~le latch~mem~ers are p~votally movable from the "down"
position in which the rod's engaging end projects radially in~ard to eng~ge a k.nob on the top o~ the control rod.
Relat.ive mo~ement bet~ee`n t~.e pair o~ cyli,nders causes the c~l~ndexs to .move the to~gle latch n~embers from their radially in~ard extended posit~on t~ a ral$ed, radi,ally retracted, di~engaged con~i~urat~,on i.n ~hi.ch the control rod is released.
Means is proY.~ded to e~ect reIatlve -3a-' ' movelnent between the cylinders when unlatching is desired. This means may be hydraulic, pneumatic, magnetic, mechanical or o-f any other character suitable For providing the remote unlatching function.
As the lift rig and the latching mechanisms are lowered down over the top end of the control rods, the lower portion of each toggle latch member is penetrated by the upper end of the control rod with the effect that it and the interior cylinder are monlentarily held vertically stationary as the exterior cylinder continues to descend. This action causes the toggle latch member to be pivoted to a semi-vertical position which withdraws the innermost end of the toggle latch member radially outward, thereby permitting the knob end of the control rod to pass by in the upward direction. After the control rod knob has passed, the toggle latch member descends under the influence of gravity to its radially inward projecting and latching position and the control rod is automatically grasped.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawings in which ~ike reference numerals refer to like elements in the several figures and in which:
Figure 1 is an elevational side view of a nuclear re-actor vessel with a portion broken away to show the uppermost ends of the control rods and to show a representation of the lif~
rig of the present invention about to engage the control rods;
Figure 2 is a broken away plan view of the latching mechanism of the invention taken along view lines 2-2 of figure 1;
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Figures 3, 4 and 5 are cross-sectional side elevations of the latching mechanism of the lift rig of the present invention showing imminent engagement of a control rod, complete latching engagement and disengagement respectively; and :
Figure 6 is a cross-sectional view of the latching mechanism of the invention taken along view lines 6-6 of figure 4.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In Figure 1 there is shown a general view of a nuclear reactor 10 consisting of a nuclear core 12 shown in phantom con-tained within a pressure vessel from which the head has been re-moved. As is well known, most nuclear reactors are controlled by the variable insertion and removal of neutron absorbing poison or control rods 22 into and out of the core. The control rods are or-dinarily grouped into a unit called a control element assembly 20 by a connecting spider 24. In at least one design of a nuclear reactor, the individual control rods 22 penetrate into the core through guide tubes 38 of the individual fuel assemblies and are protected above the core from coolant cross-flow forces to which they would otherwise be exposed by a calandria structure 14 con-sisting of upper and lower tube sheets connected by intermediate tubes through which the individual control rods 22 pass. Ordinarily the control element assembly 20 -further consists of a control rod extension 28 which terminates in an upper knob 26 adapted to be gripped by a control rod drive mechanism (not shown). For the purposes of this application, it should be understood that the broad terminology "control rod" is used to include not only the individual control rod elements 22 but also the grouping or gang-ing structures such as spiders 24 and any attached extension rods 28 which will all move in and out of the core as a unit.
.:- . . . : . .................................. .
:, , .: . ., , :
While in practical application there may exist a separate and dis-connectable control rod extension shaft connected to the control rod assembly, for the purposes of this description, the terminology "control rod" will be used -to generally include all of the struc-ture which remains after the control rod drive mechanism has been disconnected and removed with the removal of the pressure vessel head.:
As is apparent from figwre 1, access to the individual fuel assemblies which make up the core 12 of the reactor requires the complete removal o~ calandria 14. This requires the removal of all of the control element assemblies 20. Figure 1 shows a representation of a li-fting rig 30 provided for this purpose which consists of a plate 32 suspended from and lifted by support struts 34. Plate 32 includes a plurality of circular apertures 36 ~best seen in figures 3 and 5) through which the control rod latching mechanisms 40 are slideably inserted.
Control rod latching mechanisms 40 each have a pair of downwardly extending concentric first and second cylindrical mem-bers 50 and 60 with the first cylindrical member 50 mounted exter-ior to the second cylindrical member 60. First cylindrical mem-ber 50 includes an upper flange 58 which is larger in diameter than the opening 36 in plate 32 and which is fastened to plate 32 by means of shoulder bolts 42. The second cylindrical mem-ber 60 also includes an upper flange 68 whose diameter is greater than both the size of the opening 36 in plate 32 as well as the diameter of first cylinder flange 58. Flange 68 includes a plurality of positioning apertures 62 through which extend the plurality of shoulder bolts 42. Hence, shoulder bolts 42 orient : .
. ~. .. . . . .
the second cylindrical member 60 and flange 68 to the first cy-lindrical member 50 and its flange 58. These shoulder bolts also permit cylindrical cylinder 60 and its flange 68 to move up and down axially, the uppermost axial position of which is determined by the head height of bolt 42.
Turning now to an examination of the lower extremities of latching mechanism 40 (as best shown in figures 3, 4, 5 and 6) it can be seen that cylinder 50 incudes an annular inwardly ex-tending ring 51 which narrows the diameter of the interior passage 80 of the lower portion of cylindrical member 50 to a diameter which is slightly larger than the diameter of the upwardly extend-ing portion of control rod 22. Annular ring 51 has an inwardly and upwardly chamfered surface 48 adapted to guide the knob 26 of control rod extension 22 into the interior passage 80 of the latch-ing mechanism 40. Annular ring 51 also includes an upwardly facing support shoulder 52 for supporting the control rod engaging latches 70 in the horizontal position.
Cylinder member 50 further includes a plurality of angularly spaced apertures 56 through its cylindrical wall adapted to receive therewithin the first end of the elongated latch menlber 70. Elongated latch 70 is pivotally fixed to the cylin-drical member 50 by means of a dowel pin 72 which is secured in cylindrical passage 54 of the first cylindrical member 50 (as best seen in figure 6). With this arrangement, latch member 70 is per-mitted to pivot from a substantially horizontal position in which its second end laterally projects into cylindrical passage 80 to a vertically upward laterally retracted position in which the second end of latch 70 has been removed from cylindrical passage 80.
%~
The second cylindrical member 60 interior to the first cylindrical member 50, as seen in figures 3, 4 and 5 necks down to a reduced diameter so that it fits within the constricted por-tion o~ cylinder 50 horizontally adjacent to the position of mount-ing pins 72. Cylinders 60 also include apertures or latch slots 66 through which latoh 70 may extend into the interior cylindrical passage 80 of the latching mechanism 40. In a manner similar to that o~ the first cylindrical member 50, cylindrical member 60 in-cludes a plurality of mounting pins 74 secured in passages 64 for pivotally and slideably engaging the second end of latch 70.
Engagement is provided by means of elongated slot 76 in said second end of latch 70. With this construction, vertical upward movement of cylinder 60 causes pins 74 to cam in slots 76 of latch 70O
thereby lifting the second end of latch 70 and causing latch 70 to pivot in a manner which swings the second end of the latch up-ward and out of its horizontal intruding position in cylindrical passage 80 to a semivertical retracted position.
It is evident from the above description that as plate 32 of the lift rig is lowered down into its control rod engaging position, knobs 26 on the upper extremities of control rods 22 are guided by chamfered surface 48 into the interior passage 80 of the latching mechanism 40. As descent continues, the upper portions of knob 26 come in contact with the lower surFaces of pro-jecting latch members 70 so that latch members 70 are forced to swing upwardly and outwardly to their retracted positions permit-ting knob 26 to pass by. Movement of latches 70 in this manner causes the inner cylindrlcal members 60 to remain temporarily stationary as the outer cylindrical member continues to descend. After knob 26 has completely passed the latches 70, the weight of inner cy-lindrical member 60 causes the cylindrical member 60 and latches .
- : : ,... .. . -. . .
70 to fall down to their lowermost horizontal positions in which they once again project into passage 80, as shown in figure 4.
Subsequent raising of the lift rig 30 moves the upwardly facing bearing surFaces 78 of the horizontally projecting latch members 70 into contact with the lower engagement surface of knob 26. In this control rod engaging position, latch 70 is supported by the upwardly facing shoulder 52 of annular ring 51, so that continued upward movement of the lifting rig causes the control rod 22 to be raised.
After control rod 22 has been engaged and lifted for removal from the core, it is sometimes desirable to disconnect an individual control rod from the lifting mechanism for its inspec-tion and/or replacement. In addition, after the refueling pro-cedure has been accomplished, and the control rods have been re-inserted into the core, it is necessary to be able to cause the latching mechanisms 40 to unlatch from the control rods so that the lifting rig 30 may be removed while leaving the control rods in their core penetrating down positions. Both of these functions are provided by a means which permits the inner cylindrical member 60 to be vertically moved relative to the outer cylindrical member 50 thereby causing latch 70 to swing from its laterally projecting position to its laterally retracted position for control rod release. While any suitable mechanism for causing relative move-ment between cylinder 50 and cylinder 60 may be provided, -the preferred embodiment shown in the figures includes an inflatable torus 44 which is positioned around flange 58 and between floor plate 32 and flange 68. Inflatable torus 44 may be selectively inflated by means of inlet tube 46 through which pressurized air may be delivered. Accordingly, with this arrangement, all of the latching mechanisms 40 can be simulataneously disengaged from their g corresponding control rods 22 by simultaneously inflating all of the respective toruses 44. Alternatively, any selected one latch-ing mechanism 44 can be disengaged from the control rod 22 by the selective inflation of its respective torus.
The above described lift rig as illustrated in the drawings has been designed to include a self-latching latch mech-anism 40 for automatically latching the control rods to the lift rig 30 as the lift rig is lowered. This self-latching feature is activated by gravity alone so that no external power sources are required. Additionally~ the latches are arranged and sized in such a way as to self-center the control rod within the latching mechanisnl 40 to prevent the possibility of jamming or damaging the latches 70 during operation. The latching mechanism 40 can be secured in a locked or unlocked position by use of a simple locking device such as a toggle clamp or a slide bolt arrangement.
Finally, a simple switch or mechanical indicator may be provided to give a positive indication of the latched or unlatched con-dition of the latching mechanism.
--1 o--
Claims (14)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A lifting rig for lifting a plurality of vertically extending control rods out of a nuclear reactor prior to refueling, each of said control rods having attached thereto a nob capable of being gripped, wherein said lifting rig comprising:
a.) a base plate oriented transversely of said control rods; and b.) a plurality of latching mechanisms fixed to and depending from said base plate, each of said latching mechanisms comprising:
1. a support member attached to said base plate;
2. an elongated latch member having first and second ends pivotally mounted at said first end to said support member for pivotal movement between a laterally projecting substantially horizontal posi-tion and a laterally retracted position, said latch member having a portion at said second end adapted to engage said nob of said control rod; and 3. actuation means operatively connected to said latch member for yieldingly urging said latch member into said laterally projecting position.
2. an elongated latch member having first and second ends pivotally mounted at said first end to said support member for pivotal movement between a laterally projecting substantially horizontal posi-tion and a laterally retracted position, said latch member having a portion at said second end adapted to engage said nob of said control rod; and 3. actuation means operatively connected to said latch member for yieldingly urging said latch member into said laterally projecting position.
2. The lifting rig as recited in claim 1 further in-cluding means engaging said actuation means for causing said actuation means to move said latch member from said laterally projecting position to said laterally retracted position.
3. The lifting rig as recited in claim 1 wherein said elongated latch member is pivoted to rotate in a vertically oriented plane and wherein said support member includes an upwardly facing substantially horizontal stop surface for supporting said latch member in its laterally projecting position.
4. The lifting rig as recited in claim 2 wherein said latch member includes an elongated slot at its second end extending in the direction of elongation of said latch member and wherein said actuation means is adapted to reciprocate in the vertical direction and includes means for engaging said elongated slot and for moving along said slot as said actuation means is vertically reciprocated to move said latch member from its laterally projecting position to its laterally retracted position.
5. The lifting rig as recited in claim 2 wherein said support member includes a vertically disposed first cylinder and wherein said actuation means includes a second cylinder coaxially mounted relative to said first cylinder.
6. The lifting rig as recited in claim 5 wherein said second cylinder is movably mounted on the interior of said first cylinder.
7. The lifting rig as recited in claim 6 wherein said second cylinder includes an upper flange from which said second cylinder depends.
8. The lifting rig as recited in claim 7 wherein said means for causing said actuation means to move said latch member includes means operatively disposed vertically under said upper flange of said second cylinder for raising said flange and said second cylinder.
9. The lifting rig as recited in claim 8 wherein said means for raising said flange and said second cylinder includes inflatable means for inflation from a deflated, compressed, vertically down position to an inflated, expanded, vertically up position in which said flange and said second cylinder are vertically raised.
10. The lifting rig as recited in claim 2 wherein said means for causing said actuation means to move said latch member includes an inflatable means for inflation between a deflated, compressed, latch projecting configuration and an inflated, expanded, latch retracted configuration.
11. The lifting rig as recited in claim 6 wherein said latch member is pivoted to rotate in a vertically oriented plane and wherein said support member includes an upwardly facing substantially horizontal stop surface for supporting said latch member in its laterally projecting position.
12. The lifting rig as recited in claim 11 wherein said latch member includes an elongated slot at its second end extend-ing in the direction of elongation of said latch member and wherein said actuation means is adapted to reciprocate in the vertical direction and includes means for engaging said elongated slot and for moving along said slot as said actuation means is vertically reciprocated to move said latch member from its laterally projecting position to its laterally retracted position.
13. The lifting rig as recited in claim 12 wherein said means for causing said actuation means to move said latch member includes an inflatable means for inflation between a deflated, compressed, latch projecting configuration and an inflated, expanded, latch retracted configuration.
14. The lifting rig as recited in claim 5 wherein said base plate includes a plurality of circular openings through which said latching mechanisms pass, and wherein said first cylinder is removably bolted to said base plate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US84257677A | 1977-10-17 | 1977-10-17 | |
| US842,576 | 1986-03-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1094127A true CA1094127A (en) | 1981-01-20 |
Family
ID=25287690
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA309,925A Expired CA1094127A (en) | 1977-10-17 | 1978-08-24 | Extension shaft latching mechanism for a nuclear reactor control rod lift rig |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS6032839B2 (en) |
| CA (1) | CA1094127A (en) |
| DE (1) | DE2842756C2 (en) |
| SE (1) | SE427974B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4551299A (en) * | 1982-09-15 | 1985-11-05 | Westinghouse Electric Corp. | Multiple fuel rod gripper |
| EP0133173B1 (en) * | 1983-06-21 | 1987-11-19 | ACEC, Société Anonyme | Dismountable fixing arrangement for a throttle closure |
| US4651400A (en) * | 1983-12-21 | 1987-03-24 | Westinghouse Electric Corp. | Multiple fuel rod gripper |
| US4973443A (en) * | 1988-10-26 | 1990-11-27 | Westinghouse Electric Corp. | System for removing and installing a control rod drive |
| US5019325A (en) * | 1988-10-26 | 1991-05-28 | Westinghouse Electric Corp. | Method for removing and installing a control rod drive |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH478057A (en) * | 1967-08-07 | 1969-09-15 | Sulzer Ag | Gripping tool |
| US3857899A (en) * | 1968-10-05 | 1974-12-31 | Sumitomo Chemical Co | Process for selective methylation of phenols |
| US3604746A (en) * | 1968-11-20 | 1971-09-14 | Combustion Eng | Nuclear reactor control element gripper and drive apparatus |
| US3853699A (en) * | 1970-07-08 | 1974-12-10 | Westinghouse Electric Corp | Nuclear reactor having control-rod retaining means |
| US3977939A (en) * | 1973-10-15 | 1976-08-31 | Westinghouse Electric Corporation | Nuclear reactor internals arrangement |
-
1978
- 1978-08-24 CA CA309,925A patent/CA1094127A/en not_active Expired
- 1978-09-30 DE DE2842756A patent/DE2842756C2/en not_active Expired
- 1978-10-16 SE SE7810774A patent/SE427974B/en unknown
- 1978-10-16 JP JP53126304A patent/JPS6032839B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6032839B2 (en) | 1985-07-30 |
| DE2842756A1 (en) | 1979-04-19 |
| JPS5467194A (en) | 1979-05-30 |
| SE7810774L (en) | 1979-04-18 |
| DE2842756C2 (en) | 1983-03-24 |
| SE427974B (en) | 1983-05-24 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |