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LEGAL NOTICE
This report was prepared as an account of
Government sponsored work. Neither the
United States, nor the Commission, nor any
person acting on behalf of the Commission:
A. Makes any warranty or representa-
tion, expressed or implied, with respect to
the accuracy, completeness, or usefulness
of the information contained in this report,
or that the use of any information, appa-
ratus, method, or process disclosed in this
report may not infringe privately owned
rights; or
B. Assumes any liabilities with respect
to the use of, or for damages resulting from
the use of any information, apparatus,
method, or process disclosed in this report.
As used in the above, “person acting on
behalf of the Commission” includes any em-
ployee or contractor of the Commission, or
employee of such contractor, to the extent
that such employee or contractor of the
Commission, or employee of such contractor
prepares, disseminates, or provides access
to, any information pursuant to his employ-
ment or contract with the Commission, or
his employment with such contractor.
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DITE
MICROCARD
ISSUANCE
DATE


8 / 19
1964
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-:' Co we published in the Prosecco od 0 Symposium on Podcalled Content
Jovica .cl Element, Worcester, cücizusetts, lovember 6, 1963.
ORAL-P- 123
JUL 1 5 1964
ع
کرے۔ اور ترسے
MASTER
EYECE IS DEPIC..C.? OF CELIU?!-233
A rz-302 ROIS LICITY
SHIELDED PICILITY OFIIL*
:-
-
J. . Var Cleve, Jr. and b. I. Lotts
metals and Ceramics Division
Oai Ridge rational Laboratory
Oak Ridce, Tennessee

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LEGAL NOTICE -
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WinessA A LÉ FILLEDER TA
OTH * # FANALERIST.
E AS WEL EEN
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The repurt mi preparado un account of Government .poa sored work. Nelder the called
suales, dor Llore Conaiscion, or any per80 ACUN wa beball of the Commimgica:
A. Kukes my warranty or representation, expressed or implied, with respec! l the score
racy, completeness, or usefulness of tbe taforma uon coolland is we report, or eat lire une
of any taforma uon, apparatus, althod, or procesi daclosed to as report may not lalringe
privately owned rigou; or
2. Asocany liablisttes med reeport to We un ', or for damages rrowUn frou we
Un of any tAlormativa, appurato, melod, or process delosed to do repori,
Au umed in the above, "person ac leg o behalf of the Commolon" includes any of
pioyee or navractor of the Commission, or employee of our contractor, lo he entent Hout
auch employee or contra lor of the Commission, or rapiopte of such contractor prepares,
disnuinamı, or provide acces, lo. any information purstant to do employmi or cogiruct
will be Comansion, or dis enployarct me old coalriclor.
A
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Facsimile Price $_
Microfilm Price $
.
*
Available from the
Office of Technical Services
Department of Commerce
Washington 25, D. C.
*Research bred by the U. S. Atomic Erezcy Cormission üraer contract
with trac üäica viewie Corporüüion.
INTRODUCTION
The potential of the thorium fuel cycle for achieving low nuclear
fuel costs is complicated by the presence of 232U associated with 233U formed
in the re utor. The decay of the 2320 daughters produces penetrating
radiation making the consideration of shielding and fast processing
times mandatory.
The construction and operation of a lightly shielded,
semiremote facility, known as the Kil.orod Facility, in which fuel rods
containing (Th~3 wt % 2330)O2 are fabricated, is the first step in
determining the technical feasibility and economy of the thorium
fuel cycle. This facility, which 16 presently operating at the Oak
Ridge National Laboratory, was designed to fabricate fuel rods that will
be used in zero-power, criticality experiments at the Brookhaven National
Laboratory. The fuel rods are produced by vibratory compaction of sol-
gel produced oxide in Zircaloy-2 tubes to near 90% of the theoretical
density of the powder. The facility was designed to produce 10 rods/ day;
however, the attainment of this production rate was secondary to
the collection of engineering data on the process itself.
The processing of the fuel may be divided into two distinct phases:
(1) preparation of the bulk oxide by the sol-gel process and (2) rod
fabrication. This paper is concerned with the operating experience of the
rod fabrication portion of the facility. The soi-gel process is presented
in another paper;l the engineering and development of the rod fabrication
process and equipment is available elsewhere.2
FUEL ROD DESIGN
The configuration of the reference fuel rod to be fabricated in the
facility for the BNL critical experiments is shown in Fig. 1.
The BNL
experiments requir900 of these rods and 200 rods identical in design
except that they are 18 in. in length instead of 46 1/16 in.
The nominal compaction density was not specified by BNL but will be
determined from the average density of the fuel rods fabricated.
It was
specified that the rods will have a fuel density of 12% of this determineu
average density and the density within a fuel rod will be +2% of the
average for that fuel rod. Based on experience with depleted (U, Th)o, in
the "cold" operation of the facility, an average density of 90% of
theoretical is expected.
The cone-shaped Zircaloy-2 bottom fitting, which will be used to
direct the rod in the critical lattice at BNL, is welded onto the tube
in a gas tungsten-arc welding operation, which is done outside
the facility. The annular groove in the bottom plug is used as a handling
aid during fabrication. In the facility, the top plug, ceramic spacer,
and spring are inserted into the fuel tube after compaction as a unit.
the fuel rod to prevent redistribution of the fuel during handling. The
Zircaloy-2 top end plug, joined onto the fuel tube by a fusion edge weld
in the facility, is threaded to accommodate the stainless steel hanger
fixture. This hanger fitting will be used to facilitate handling of the
fuel rod in the critical lattice.
PROCESS
The rod fabrication process (Fig. 2) starts with the delivery of
the bulk sol-gel oxide to the powder preparation equipment. The material
is first crushed in a jaw crusher and separated by a continuous screen
classifier into three size fractions: +6, 6+16, and -16. Through
recycling of the +ó fraction and judicious charging of the ball mill with
the 6+16 and -16, sufficient amounts of coarse and fine powders consisting
of 55% 6+16 and 45% unclassified fines are produced. The development of
the process to produce the fine fraction will be considered in the "cold"
operation section. The two fractions are then separately weighed out on
an automatic batch weigher, blended in a "v" blender, and, using a vibrating
feeder, fed into the rods. The powder 18 densified using an air driven
vibratory compactor during feeding followed by additional densification
with a weighted rider rod resting on top of the fuel colum. The end cap,
specer, and spring are then placed in the rod and the end-closure weld nade.
Next, the rod 16 ultrasonically cleaned and gamma scanned to determine the
density fluctuations along the long axis. The welds are then helium
leak checked and the rod smeared and cleaned until the smear count 15
< 2000 dis/min. Finally, the rod is loaded into the carrier for shipment.
FACILITY AND EQUIPMENT
The rod fabrication facility occupies the lower two levels of a three-
level facility shown in Fig. 3. The third level houses the sol-gel process.
The facility was constructed in an unused chemical-processing cell to take
advantage of the air-handling equipment and to use the existing cell walls
for secondary containment. Located in one corner of the first level and
extending to the top of the second level in the LX 7-ft powder preparation
shaft. Adjacent to this shaft, on the first level, are the three fabrica-
tion cubicles. The first cuticle contains the vibratory compaction apparatus
and the automatic welder, the second the ultrasonic cleaner, and the third
the gamma-ray densitometer and hellum leak detector vacuum chamber.
Directly over the first two cubicles on the second level is the glove
maintenance area. Access into the powder preparation shaft is through
a shielding door in the side of the shaft opening into the maintenance
area. Access to the fabrication cubicles 18 through roof hatches opening
into the same area,
The operation of the fabrication equipment is performed either by
castle joint manipulators or gloved hands. The powder preparation equip-
ment is operated by flexible shafts extending through seals at the
shielding wall. The facility is gamma shielded by 4 1/4-in. armor plate
and alpha sealed with an inner liner of il-gage mild steel. Three bag-
out ports are provided for the entry of small support equipment and
removal of debris and samples.
The powder preparation equipment (F18. 4), which is located in the
powder preparation shaft, utilizes gravity to transport the fuel through
pipes from one equipment unit to the next. All of the equipment in the
powder preparation shaft is remotely controlled either electrically or
by flexible shafts. Minor repairs are made in-place through glove-access
ports. To facilitate major repair, the equipment is mounted on movable
racks in the front half of the shaft. The defective piece of equipment
can be removed by pushing the equipment rack to the rear and lifting the
piece to the repair area with a hoist.
The vibratory compaction apparatus is shown in Fig. 5. An air driven
impact hammer is used as the compaction device.
The functions of the end-cap welding machine (Fig. 6) include evacuation
of the rod, backfilling with helium, seating the end pluk, and making the
fusion end-closure weld.
The ultrasonic cleaning device with its attendant power supply 16
shown in Fig. 7. This unit fills with water, ultrasonically cleans the
rod, drains, sprays the rod with fresh water, und dries the rod in a blast
of warm air. These operations are controlled from a console in the operating
area.
The gamma-ray densitometer is shown in Fig. 8. The variation in
compacted fuel density is measured by the attenuation of the radiation
from a 6oCo source as it passes through the fuel bed. The beam is collimated
by a 1/8- X 3/8-in. slot between the source and fuel rod.
OPERATING EXPERIENCE WITH STAND-IN OXIDE
During the initial operation of the fabrication equipment with stand-in
oxide (depleted (U,TH)22), it soon became evident that the powder-conditioning
equipment was the area oî najor concern. Despite efforts to contain dust
within the system, an unexpectedly large quantity of oxide dust accumulated
on the exterior of the equipment. Obviously, this very abrasive dust can
cause excessive wear of bearing and bearing surfaces. The abrasive nature
requirements of the mill to be rotated about three axes simultaneously
necessitated the use of several types of bearings. Extensive modifications
were essential to obtain a suitable working situation. Even after apparently
solving the bearing problem, other modifications were necessary because of
the wearing of bearing surfaces causing extraneous material to be introduced
into the fuel.
Before operation, there was concern that the classifier
screens might blind during operation; however, during the cold runs there
was no evidence of screen blinding. The remainder of the powder-conditioning
equipment has performed satisfactorily. In the complete system, a material
holdup of approximately 2 kg was observed during the cold runs.
During the operation of the vibrator system, several modifications
were necessary. The need to observe the feeding of the fuel into the
rod required the elimination of the dust boot over the end of the feeder
trough. Although the elimination of the boot increased the dusting, it
was felt that adequate feeder control could not be obtained without observe
ing the feeding. The chuck for holding the rod was designed to utilize a
slightly modified Swaggiok tube coupling. This coupling uses a standard
1/2-in. ps.pe 0 1/2-in. tube male connector with specially machined split
ferrule. During tụe "cold" operations, failure of the Swagelok chuck was
usually observed after 10 to 12 rods; therefore, it is planned to change
the Swagelok tube coupling after the compaction of six rods. Also, &
number of failures in the other components of the vibrator-chuck assembly
are anticipated because of the extremely high levels of acceleration
associated with the Branford* vibrator (reportedly as high as 20,000 to
100,000 times the acceleration due to gravity). Along with daily main-
tenance checks on all fasteners on the unit, spare components to the
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entire vibratory compaction assembly are considered absolutely essential.
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In operating the vibrator, it was found that the freedom of the
-
anvil, to which the rod to be filled is attached and upon which the
.
pneumatic hommer impinges, is a very important factor. The anvil must
be allowed to move a finite distance (in the order of 1/16 in.) to obtain
the desired compaction. If the anvil is not allowed to reciprocate, a
reduction in compacted density of from 8 to 10% 1.8 observed. Some diff!-
culties were experienced with the Branford vibrator due to component
failures within the vibrator unit.
*Manufactured by the Branford Co., New Britain, Connecticut.
After demonstrating the ability of the powder-preparation equipment
to produce powders of three size fractions for loading into the fuel tubes,
It was decided to modify the system to produce powders of a binary-size
distribution. The decision to operate the system with two size fractions
was based on two factors: (1) the binary system is equal to the ternary
in compaction density that is attainable and (2) the binary is much easier
to operate, especially with a remote systei. During the cold runs, the
binary-size distribution was optimized and now consists of a charge of
55% of a classified 6+16 mesh fraction and 45% of an unclassified ball
mill fraction. The ball mill fraction 18 controlled by the weight of
charge and the time spent in milling. A set of conditions was determined
which would result in the most practical use of the distribution pro-
duced by the jaw crusher and which would compact to acceptable densities.
The ball mill fraction has the following approximate composition:
20%
-16+50
--50+140
-140+200
--200+325
--325
30%
20%
5%
With this distribution, 20 cold samples were compacted that had an average
bulk density of 90% of theoretical with a deviation from rod to rod of
< 1%.
The density profile measured with the gamma scanner within the se
rods was well within the specified +2% with the majority showing a
deviation of
1 1/2. The results were most gratifying as results of this
nature had not been predicted from laboratory experience. Apparently, a
wider distribution range of powders can be utilized with the bottom-actuated
pneumatic device used in the facility than can be used with an electromechanical
device similarly or on a beam system. The greater breakup of powder
during compaction with the pneumatic device can account for this
observation.
HOT OPERATION
After developing the process and equipment to the point that a
sustained period of acceptable rod production with the stand-in oxide
was obtained, the entire system was dismantled, cleaned, and reassembled
before the introduction of the 233U-bearing fuel. The initial operation
with the 2330 fuel was not smooth as numerous difficulties aguin appeared.
The remotely operated hall mill continued to give trouble and was
replaced with one operated with gloved hands. After the se initial prob-
lems were solved, the equipment performed with minimin difficulties.
The reject-rod rate during the production of the first 100 rods was
25%; this was attributed to lack of experience in the operation and process.
After this initial operation, the rejection rate was greatly reduced and
is presently at the tolerable figure of 3% of the production. The rejection
rate is more accurately described as a reprocessing rate as neither the
hardware nor the fuel is lost. When a rod is rejectea, the fuel is simply
emptied from the rod and the tube reloaded.
In rod production, the most difficult specification to maintain has
been the 12% on the density profile. The bulk density and fuel bed heigiit
specification have not accounted for a single reject. The rejects on
density profile have been traced to either poor preparation of the fine
fraction or failure of some component oi. the vibrator system. Typical
traces produced by the densitometer of an acceptable and rejected rod are
shown in Fig. 10. The decision to accept or reject a rod is made 'oy com-
paring the extremes of the scan with the separation produced by a set of
stendards which are scanned with each rod. In Fig. 10, the trace of the
standards is shown to the right of the two roj traces.
Rod production has been divided into campaigns for fuel accountability
and criticality considerations. At the end of each campaign, a material
balance is made, the operation reviewed, and equipment alteration made, if
necessary. To date, 416 acceptable fuel rods containing over 390 kg of
.
fuel have been produced in four campaigns. A sustained production rate of
10 rods/day has been achieved over the last 100 rods with a maximum
production rate of 19 rods/day being accomplished on several occasions.
SUMMARY AND CONCLUSION
Through the design, construction, and operation of the Kilorod
Facility and its fabrication equipment, the practicability and economics
of refabrication of (2330, TM)02-bearing fuel rods are being assessed.
Although a complete assessment of the facility cannot be made at this time
because production is still in progress, the operation of the facility
has proven the feasibility of a bulk oxide vibratory compaction method
of fuel element fabrication. Using a binary powder-preparation system
developed in the facility in conjunction with a pneumatic-type vibrator,
it has been shown that 100% of the fuel produced can be utilized in the
fabrication of acceptable fuel rods.
The following conclusions have been made based on the operating
experience gained at approximately the half-way point in the project:
1. The engineering feasibility of the vibratory compaction method
for producing oxide-filled rods has been proven.
2.' Rods of (90 +29% of theoretical density, of +2% or less variation
10
along the long axis, And of 42 ft 11 in. fuel bed height have been
routinely produced.
3. A method of producing a fine fruction by control of operating
parameters has been devised and proven.
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REFERENCES
1. C. C. Haws, Jr., "Pilot Plant Preparation of 233U02-ThO2 Shards by
the Sol-Gel Method," paper presented at the Powder Filled Uranium
Dioxide Fuel Element Symposium held at Worcester, Massachusetts,
November 56, 1963.
2. J. D. Sease, A. L. Lotts, and F. C. Davis, Thorium-233u Oxide (Kilorod)
Facility — Rod Fabrication Process and Equipment, ORNL-3539 (April 1966).
LIST OF FIGURES
1. (ORNL-LR-DWG 6615383) Design Features of the BNL Fuel Rod.
2. (ORNL Dwg 6h-239) Fuel Rod Fabrication Flowsheet.
3. (ORNL-LR-DWG 76196A) Kilorod solide Preparation and Rod Fabrication
Facility.
h. (ORNL-LR-DWG 74597)
Powder Preparation Equipment and Mounting Pallets.
5. (ORNL-LR-DWG 75776) Vibratory Compaction Apparatus.
6. (ORNL Photo 58244-A) End-Cap Welding Machine.
7. (ORNL Photo 58683) Ultrasonic Cleaner, Power Supply, and Cleaning
Tank.
8. (ORNL Photo 59560-A) Gamma-Ray Densitometer.
9. (Photo 58687A) Remote Ball Mill.
10. (Y-55931) Ivo Typical Density Profiles Obtained from the Gamma-Ray
Densitometer,
UNCLASSIFIED
ORNL-LR-DWG 66153R3
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SECOND LEVEL EQUIPMENT
MAINTENANCE
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FIRST LEVEL ROD FABRICATION:
VIBRATORY COMPACTION - WELDING-
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