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Shear Performance
Moscow, Idaho 83843
[email protected]
Dec. 11, 2006
Tom M. Pfeiffer
Idaho National Laboratories
Idaho Falls, ID 83415-6180
[email protected]
Dear Mr. Pfeiffer:
The report is a list of work up to now. We have broken down the problem into
individual steps which are used to accomplish the wire removal process. From these
individual steps ideas were formed to improve the current system as well as new ideas
which can be used. Sequentially after our brainstorming we integrated our individual
ideas to form possible solutions to automate the wire removal process. Two solutions
were developed but will need further enhancement prior to construction of each prototype
solution.
During winter break, we will develop concepts combining the stronger points of
the two integrated design, into a single functioning design. When we return on January
10th, the team will construct a prototype of the final design and begin testing. Please let
us know if there are certain concepts you would specifically like to see implemented.
If there are any further questions on this report feel free to contact us.
Sincerely,
Shear Performance
Enclosure: Final Report
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Nuclear Fuel Element Wire Removal:
The Design and Testing of an Automated System
Prepared for:
ME 424
Senior Capstone Design
Steve Beyerlein
Tom Pfeiffer
Prepared by (L-R):
Justen Bock
Richard Fries
Chris Johnson
Alberto Castro
December 11th, 2006
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Executive Summary
Team Shear Performance is designing an automated system of the wire removal
process to reduce labor and process time. The wire removal process is composed of five
steps: loading the fuel elements, orientating the wire’s position, shearing and separating
the wire, cutting the wire into smaller pieces, and cutting the fuel rod into smaller pieces.
The scope for this semester has restricted us to develop concepts for each step in the
removal process, save cutting the fuel rods into smaller pieces, and begin building some
prototypes of those concepts. Our two final integrated concept designs still need further
development prior to building prototypes and beginning testing because they both fail to
perform all five steps of wire removal process.
Our most significant achievement is the prototype Pacman wire shearing device
we created. Although it has not yet been hardened, we have cut softer materials such as
rubber and wood which demonstrates the effectiveness of the design. This device was
great step because we learned that the initial design shape of our shear was not sufficient
and had to be redesigned for functionality.
The next aspect of our project, performed over winter break, will be to each
design a mechanism which combines the best concepts of each integrated design into a
single, fully functional, design which performs all the steps of the wire removal process.
We must also consider that the fuel elements may have a significant bend in them.
Because of the critical tolerance values attributed to the shearing devices, a reliable
straightening apparatus will be mandatory.
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Table of Contents
1.0 Background……………….…………….…….1-2
2.0 Problem Definition………………......…….…....3
3.0 Concept Development……….……………....4-12
3.1 First Generation Prototype Design.............4-5
3.2 Double Shear Mechanism...........................5-8
3.3 Pacman Mechanism..................................9-12
4.0 Concept Selection………..……………...….12-14
4.1 Double Shear Mechanism............................13
4.2 Pacman Mechanism.....................................14
5.0 Project Plan.…………………………………...15
6.0 Future Work…………………………...………16
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1.0 Background
Idaho
National
Laboratory
(INL)
in
Southern
Idaho
performs
an
electrometallurgical treatment for used nuclear fuel elements so that the nuclear material
can be contained and reused in the future. The fuel elements have a 0.171 diameter
stainless steel wire wound around them four times in a helical pattern from one end to the
other, with the wire welded at each end. While the fuel elements are in use in a reactor,
the wire acts as a spacer separating each element from one another. In preparation of this
treatment the wire must be removed.
Presently, the used fuel elements must be manually loaded into a shearing device by a
trained technician using a master slave apparatus (Figure 1), and then the technician must
engage the shearing device by depressing a foot petal. To completely separate the wire
from the element this shearing process must be repeated twice, once for each end of the
fuel element. After both welds have been sheared, the technician again uses the master
slave apparatus to place the unattached wire as well as the fuel element into their
respective specialized chopping devices. These choppers will reduce both the wire and
the element into three inch long pieces, in preparation for the next phase of treatment.
Figure 1: Master–Slave Manipulator Diagram
The operator stands in the corridor and operates equipment located inside the hot cell.
Typical lifting capacity is 20 lbs. max straight up, and less the farther he has to reach.
Slave end effectors are two-fingers that pinch together.
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Figure 2: The figure above shows the shearing device (top left) and the wire chopper (bottom
right) that are currently being used.
The presently used fuel element treatment process requires the constant attention
of a technician to perform all movements and manipulations of the fuel element. This is
a tedious and frustrating process that could be improved by replacing the current system
with an automated one thereby reducing the required operator time and increasing
productivity. The current process results in approximately two and a half carrousels of
fuel elements refined within a work day. One of the requirements of the future automated
mechanism is that at least one entire carousel must be refined every two hours. This will
amount to a total of four or more carousels ready to advance in the treatment process per
day. Because of the large amount of fuel elements that need to be processed, an increase
of one and a half carousels per day will decrease the number of days spent on the process
from 190 to 119; a 37 percent improvement. In addition to increasing productivity the
new automated design will require no more than ten minutes time, per carousel, spent by
the technician for loading and unloading of fuel elements. This will allow the technician
to perform alternative duties for a majority of their work day thus increasing that person’s
overall productivity.
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2.0 Problem Definition
Approximately 40,000 fuel elements are still left which need to undergo the fuel
treatment process. The current wire removal mechanism enables the operators to only
prepare no more than 500 fuel elements in two weeks. The manual wire removal
mechanism usually takes several attempts until the wire is removed from the fuel element
tube. This causes much frustration to the operator and delays the entire process. An
automated mechanism needs to be designed so that a technician is no longer required to
manipulate the fuel element throughout the wire removal procedure as well as the wire
and element chopping processes.
Attempts have been made to automate the wire removal process but have failed to
meet demands. The automated process must meet the demands which INL believes is
satisfactory: being capable of decreasing the current wire removal time in half, keep
track or not loosing any radioactive material, and have limited or no intervention from the
operator to perform the wire removal tasks. The automated process must also perform
several operations to complete the wire removal task:
1. Load the fuel element into a wire shearing device
2. Orientate the fuel element to properly position the wire
3. Shear and separate the wire from the fuel element
4. Cut the wire into pieces of three inch length
5. Cut the fuel element into pieces of three inch length
No personnel are allowed inside the hot cell due to the high radiation
concentration therefore the mechanism must be easy to construct and repair. Once the
mechanism is put in place inside the hot cell any type of repair must be made using the
master-slave manipulators.
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3.0 Concept Development
Team Shear Performances developed two concept solutions for the wire removal
process. The ideas developed for the solutions can be integrated to both designs. Our
scope did not allow for complete prototypes to be made for testing purposes. Only a
single prototype was made.
3.1 First Generation Prototype Design
The second wire removal concept has been created from scratch. This concept
came from early brainstorming ideas. An early concept was made to demonstrate a
complete solution to the automation of the wire removal process. This early concept is
shown in figure 3.
Fuel Element Bin
Fuel element Shute
Fuel element
bin (under
chopper)
Rotating gears
Loading arms
Pacman
Spacing wire bin
Fuel element
chopper
Figure 3: First generation design concept illustrates each stage of the automation process.
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The early concept design was going to use a loaded bin to hold all the fuel
elements. The fuel elements would then drop down the chute into a rotating gear which
would hold a single fuel element in each groove. The loading arms would then hold to
both ends of the fuel element and load it into the Pacman. The Pacman would then shear
the spacing wire into sections off of the fuel element. The spacing wire would drop into
the spacing wire bin. The fuel element would be carried by the Pacman to the fuel
element chopper. The fuel element chopper would then chop the fuel element into
sections and the sections would fall into the fuel element bin below it. This was a great
initial concept because it gave the team a visual of each step which needed to be
accomplished before the electro-refiner.
This concept founded the present Pacman
concept.
3.2 Double Shear Mechanism
Figure 4: Double shear mechanism concept
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The first concept solution which was developed is the double shearing mechanism
as shown in figure 4. The first concept uses the existing wire removal mechanism design
with improved positioning mechanisms.
The fuel element orientating mechanisms
include the shackle, and the clapper. Besides using new positioning mechanism it will
also include a second shearing mechanism to shear the spacing wire from both ends of
the fuel element.
The Canister: The use of canister loading mechanism has been thought about to load
the fuel elements into this wire removal mechanism. The canister idea can be seen in
figure 5.
Figure 5: Canister to be used for loading fuel elements into wire removal mechanism
An operator loads the fuel elements into each of the dispenser shafts, and as the canister
revolves, a single fuel element is dropped though the exit port at a time. This individual
fuel element will load into the top of the first wire removal concept.
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The Clapper: The clapper is the positioning device which will be used on the current
wire removal design. The clapper concept design is shown in figure 6.
Figure 6: The Clapper used for positioning the fuel element and orientating the wire’s position.
The clapper will position the fuel element so that the spacing wire is orientated to the
positioned needed for the blades to shear the wire off the fuel element.
The Shackle: The shackle is a positioning concept that will be used to align the fuel
element for the top shearing mechanism. There are a few reasons why this first concept
needs the shackle concept. The first reason is that the fuel element usually is bent from
operator handling as they are removed from the sub-assemblies which are used inside the
reactor. Figure 7 shows how a shackle aligns the fuel element into a vertical straight
position.
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Figure 7: The Shackle device neutralizes the effects of bent fuel elements.
The shackle will allow the fuel element top end to be within the parameters needed for
the top shearing blades to work effectively.
Further development to the concept is still needed before a prototype can be
constructed. There also hasn’t been any ideas developed which will unload the fuel
element and wire from the wire removal mechanism. Due to our time constraint, our
team has agreed that further development of this concept will be developed during the
second semester of our school year.
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3.3 Pacman Mechanism
The second concept design was originated from its early design. The concept
shown in figure 8 involves the Pacman, shackle arm, T-bar, and the slotted pan.
Figure 8: The Pacman mechanism concept
The Pacman: The pacman has many advantages other than a wire removal mechanism.
The Pacman as shown in figure 9 allows for 180 degrees of spacing wire positioning
along with the capability of shearing the wire into sections.
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Figure 9: The pacman device shears the wire from the fuel element.
This has been the only concept idea which was constructed into a prototype. The
prototype was only constructed to shear only a small segment. It was to merely have a
visual and to make simple tests. The prototype shown in figure 10 proved that it has high
potential to be the solution to the automation of the wire removal process.
Spacing wire
Figure 10: Pacman Prototype
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The Shackle Arm: The shackle arm is used for the same reason that the shackle in the
first concept is used. The fuel elements maybe bent from operator handling. A few
shackle arms will be located on one of the sides of the Pacman and they will swing to
straighten the fuel element.
They will assure the fuel element will drop into the
designated grooves made in the Pacman.
The T-bar: The T-bar is a fuel element delivery system which will load the fuel
elements into the Pacman as can be seen in figure 8. The construction drawing of the Tbar is shown in figure 11.
Figure 11: The T-bar delivery system allows the fuel element to slide into place.
The T-bar will utilize the spade end of the fuel element. The opening in the spade end
will be used to introduce the retractable hook mechanism used in the T-bar.
The
retractable hook will enter the spade end opening. Once the retractable hook is inside the
spade opening it will spread out and hold the spade end. The T-bar will then carry the
fuel element. The T-bar will be used at an angle to use gravity to its advantage and
gravity feed the fuel element into the Pacman.
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The Slotted Pan: Once the Pacman has sheared the wire from the fuel element the fuel
element and wire sections will fall into the slotted pan. The slotted pan is shown in figure
12.
Figure 12: The Slotted Pan
The slotted pan will be constructed so that an initial hole small enough to allow
the spacing wire sections to fall in but not large enough for the fuel element. The fuel
element will then continue to the end of the tray in which they will fall into a separate
box.
4.0 Concept Selection
The selection process involved evaluating the strengths and weaknesses of the
two most recent mechanism designs. The best components will continue to be developed
into a third generation concept.
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The new design only needs to perform better than the device that is currently
being used to meet the client needs. If we only picked one small part of the process to
speed up and to reduce user input, then we are simply meeting the client’s expectations.
If we want to exceed our client’s expectations, then we need to look at the whole process
and improve every step, from fuel rod delivery to disposal. The following discussion will
develop a convincing case for each integrated design and its individual components,
showing how the overall design will exceed customer expectations.
4.1 Double Shear Mechanism
The double shear design saves the operator a lot of time and labor by eliminating
the eliminating the need to flip the rod 180 degrees. It does this by shearing both ends of
the wire simultaneously. The operator’s labor in this process is at least five seconds. Even
if the complexity of the double shear design (the top shear sliding into position and
orientating the wire) adds five or ten seconds to the shearing process, it has freed the
operators hands to perform other tasks (such as loading canister or wire chopper).
The next feature of the double shear that saves time, labor, and frustration is the
clapper. In the past, the operator would drop the rod into the funnel that leads into the
shearing device. The operator would then have to rotate the rod until it fell into position
for cutting. The operator consistently had to attempt the shear 3-5 times before
succeeding. After each cutting attempt, the operator had to remove the rod from the shear
and confirm that the wire was cut. The clapper may save between 5-20 seconds,
depending on the luck of the operator (operating the old device).
The canister is a delivery system. It is loaded by the operator and then it dispenses
the rods into the wire cutting device. In the original set-up, the operator would devote all
of his attention to one rod through the whole process. With some of the time saved by the
other components, the operator will be free to load the canister faster than the shearing
device can cut the wires.
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4.2 Pacman Mechanism
The Pacman design also eliminates the need for the operator to flip the fuel rod by
cutting the wire at both ends, as well as several other locations. By cutting the wire in
several spots, the Pacman design eliminates the wire chopping device. The operator no
longer has to transport the wires to the chopper, which saves a good deal of time. Also,
by eliminating the wire chopper, we will eliminate any maintenance to that particular
machine. So the Pacman shearing device, alone, attacks multiple steps in the process.
The Pacman design, like the double shear, will also be integrated with a delivery
system. The Pacman could probably use the same canister dispensing system that the
double shear uses. We have also considered the T-bar. Both, as mentioned before, allow
the operator to work while the shearing device is working. In the past, even if the
operator had spare time, he couldn’t do anything with that time between steps in the
process. These dispensing systems allow the operator to keep moving, thus keeping a
steady flow of processed fuel rods moving through the system.
The Pacman is currently integrated with the slotted pan to sort the wire segments
from the fuel rods. The operator no longer has to manually remove the rods from the
shearing device, as with the double shear and the original shear. Also, the slotted pan
could potentially guide the fuel rods into the cassette that feeds the rods into the fuel rod
chopper. The Pacman design is a more promising improvement to the overall process.
The only thing that would hold us back from pursuing it exclusively is the fact that it is a
completely new and completely different device from what the INL currently uses.
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6.0 Project Plan
Table 1: Work schedule breakdown for fall semester.
Our experience in the machine shop has led us to o greater understanding of what
the scope of our project consists of. We now take into consideration what it will take to
machine our product upon design. Because we are only allowed to use simple tools like
the drill press sander and band saw we are limited to what we can make with out the use
of the end mill and most importantly our mentor.
Our future plans require much more precise machining for this reason our mentor
must be present at much more of the machining than recently. This will require us to plan
further ahead so that we can reserve a time that will not only match our group members
schedule but the schedule of our mentor and the unreserved times of the mills and lathes.
One reason that we need to use the mills from now on is that the system that we
are perusing has five supports and interdependent planes that must be aligned. This
requires great accuracy because if these planes are not perfect the devise will bind up. If
the system is two sloppy the shear will not have a sharp edge and therefore not cut.
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7.0 Future Work
Our team has decided to take the more desirable concept components of each of
the two intergraded designs, and use them to create a single, complete and fully
functional design. This will utilized the strong points of each design while eliminating
each of their weak points. In collaboration with our client, we have isolated the design
components that will continue to the next stage of improvement.
Each team member will, over winter break, develop a design for the new
combined concept. Upon returning for spring semester, our team will begin constructing
simple prototypes of the previously selected design components. Using the physical
models and all the team member’s designs, we will construct the complete final design
prototype. Our team will again submit the final completed design to our client for
approval and/or suggestions before advancing the prototype to the testing phase. A
tentative schedule for spring semester is show as table 2.
The shearing edges of our design will need to be hardened to counteract the
repetitive wire cutting in the testing phase. The final prototype will need to be tested for
its reliability with not only straight fuel elements but also bent ones. Once completed to
the satisfaction of our team, the test results as well as the prototype and a final report will
be submitted to our client for approval and critiquing.
Table 2: Spring semester work outline.