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Stan Thompson

[ Uranium Fuel ] Breeding Pile ] Bad Shit ] SGT's Facilities ] SGT's Process ] Michele Gerber ]

by Michele Gerber, Ph.D. and is available to download

                                                   1.0  FUEL FABRICATION PROCESSES


1.1.1  Solid Uranium Metal Fuel Produced

          The nuclear fuel fabrication processes employed at the Hanford Site to manufacture plutonium (Pu) for defense purposes essentially produced solid uranium (U) metal fuel elements, jacketed in aluminum-silicon (later Zircaloy-2)a coats.  Although some variations were introduced, the solid metal fuel type was not replaced by powdered or pelletized fuel forms, nor by mixed oxide (MOX) fuel blends for the production of defense-grade Pu-239.  Moreover, the fuel-making processes used at the Hanford Site for defense production all were unique and prototypical at the time they were initiated.  Thus, they qualify under criteria of the National Historic Preservation Act (NHPA) as historic processes.  Original Fuel-Making Buildings.  The original fuel-making process employed at the Hanford Engineer Works (HEW- World War II name for the Hanford Site) was known as the "triple-dip" process.  It took place in two buildings in HEW's 300 Area, known as the 313 Metal Fabrication Building and the 314 Press Building (also known as the Metal Extrusion Building).  Both buildings were constructed of structural steel framing, had concrete block walls and concrete slab floors, and sat on reinforced concrete foundations.  The 313 Building had a precast concrete slab roof with tar and gravel surface, and interior partitions made of concrete block and concrete brick.  The 314 Building had a corrugated asbestos roof with a 36‑inch (91.44 centimeters) continuous roof ventilator extending nearly the entire length of the building.  Interior walls consisted of concrete block with 3/16‑inch asbestos board on some interior partitions.[i]

          The original 313 Building, completed in the Autumn of 1943, was rectangular in shape, with overall dimensions of 199.5 feet (60.8 meters) by 65 feet (19.8 meters) by 20 feet (6.09 meters) (high).  However, eight subsequent additions made in late 1943 and in 1944 brought the overall dimensions to 199.5 feet (60.8 meters) by 182.5 feet (55.6 meters) by 20 feet (6.9 meters) (high), with a total area of approximately 36,000 square feet (3,344.4 square meters).  The continual early additions were caused by process improvements and changes in the very new, untried, and unique uranium fuel fabrication activities being carried out in the facility.  According to prime construction contractor DuPont Corporation:  "In the construction of the 313 Building, the first equipment to go into operation was known as the experimental line.  This line was set up specifically for experimental purposes...[and] was dismantled and moved to other portions of the...Building."[ii]


          The first 313 Building addition, on the east side, provided additional space for furnaces and presses, and the second, on the west side, provided a tool room and shop.  The third addition ran the entire east side of the building, and allowed space for welding booths and jacket (can) washing.  The fourth addition, on the northwest corner, furnished an electrical control room, and the fifth addition, along the west side, included a locker room, women's rest room, and shower room.  (The locker and shower rooms later were eliminated in favor of a storeroom.)  The sixth addition was again on the northeast corner of the facility, and provided more space for can washing.  The seventh addition, on the southeast of the building, allowed for a second canning process section and for "recovery" (uranium scrap recycling) process equipment.  However, this latter equipment soon was moved to the nearby 314 Press Building.  The eighth and final addition of WWII was on the northeast corner, and furnished space for a third canning process section.[iii]  The 313 Building contained numerous electrical furnaces and metal presses; three fuel canning areas; a welding area; a can cleaning area; a control room; various supply tanks; a tool room and shop; and various offices, storerooms, and sanitary rest rooms.


          The 314 Press Building had original overall dimensions of 199.5 (60.8 meters) feet by 90.5 feet (27.58 meters) by 40 feet (12.19 meters) (high) with an area of about 17,000 square feet (1579.35 square meters).  It contained a 1,000‑ton extrusion press, electric furnaces, a rod-straightening machine, a 7.5‑ton overhead crane, an autoclave area, a control room, a shop and repair area, pumping units for the press, and various offices and sanitary rest rooms.  Outside, there was a 12‑foot (3.66 meter) by 18‑foot (5.49 meters) concrete and steel platform north of the building.  Gas cylinders were located outside along the north wall.[iv]



1.1.2  The Overall Process


          Hanford's original fuel-making processes can be summarized as follows:  It began in the 314 Building, where uranium that arrived as billets was heated in a muffle‑type furnace with an interior, inert gas atmosphere.  (The helium or argon atmosphere was used to reduce the oxidation of metal during heating.)  The uranium was then transferred through a closed passageway to the extrusion press, which also operated in an inert atmosphere.  After being extruded, the rods were outgassed, straightened, and sent to the 313 Building for machining and jacketing.  In the 313 Building, U fuel rods were machined into fuel cores in lengths of either 4 inches (10.16 centimeters) or 8 inches (20.32 centimeters), with 1.3-inch (3.3 centimeters) inner diameters.  Known as "slugs," these cores were "canned" or jacketed into finished elements, and then tested and inspected in this building.


          Details of the HEW fuel-making process provide valuable insights:  The earliest uranium for the fabrication of reactor fuel arrived at the HEW in October 1943 as extruded rods.  The rods were delivered to the Riverland Yards.  The Riverland Yards were an official part of HEW and were located just east of the Midway power substation (just west of the 100-B Reactor Area).  Because railroad track had not yet been completed to the 300 Area, the rods were taken by rail to the Hanford Construction Camp about 20 miles (32.19 kilometers) north of Richland, and then by truck to the 300 Area.  Once railroad service to the 300 Area was connected in January 1944, uranium was delivered to the fabrication area by rail.


          Newly arrived U rods were unpacked and visually inspected (in sample amounts) for cracks and for overall dimensions.  A random amount from each lot was taken to the 305 Test Pile Building just west of the 313 Building, and irradiated at a low level to check for warping, cracking, and embrittlement under irradiation.  If the sample withstood the process in good form, the entire lot was accepted.  Beginning in December 1943, the first uranium fabrication operation at HEW was machining, in which bare uranium rods were lathed down to specific core dimensions in the 313 Building.  The following month, operators began degreasing the machined cores before inspection, using a commercial product that contained primarily trichloroethylene, Detrexa, a solvent degreaser.  Core canning operations actually began in the 313 Facility in March 1944.


          In the 314 Building, autoclaves for fuel element testing started to operate in July 1944.  A scrap recovery process began the following month.  Outgassing and straightening operations started in the 314 Building in September 1944, but HEW's uranium rods still were being extruded offsite.  Beginning in November 1944, uranium was transported to HEW as billets, which were stored until the extrusion process began to operate in the 314 Building in January 1945.  The press testing phase lasted into mid‑spring, and then fuel operations commenced.  Greater confidence in personnel performance ended shift work in the metal preparation buildings in June 1945, and work proceeded on a straight, 6‑day-per-week schedule.  From that time until 1948, a complete cycle of metal preparation occurred at HEW.  The uranium billets went to the 314 Building for extrusion, outgassing, and straightening, then to the 313 Building for machining, canning, and initial inspection, and then back to the 314 Building for autoclave and radiograph testing.[v]



1.1.3  Canning


          The original fuel canning process tried at HEW involved the use of an electric heater press, known by workers as the "whiz‑bang," to heat and bond the uranium fuel cores to their aluminum jackets.  However, the heaters burned out frequently, did not heat the elements and cans to consistent temperatures, and did not produce a uniform bonding.  This problem was serious because nonuniform bonding caused thin places in the jacketing that, under irradiation, heated up more than other places.  These "hot spots" could cause fuel element ruptures in the reactors.  By August 1944, the uranium fuel cores were being jacketed in a triple‑dip method that consisted of bathing them in molten bronze, tin, and then a molten aluminum‑silicon mixture.  The bronze used in this process at HEW was relatively high in tin content (53% tin and 47% copper), and the bronze bath itself had a flux cover composed of barium chloride, potassium chloride, and sodium chloride.  As fuel cores were dipped into this mixture, they acquired trace coverings of all of these substances.


          Initially, the bare uranium cores were cleaned by passing them through a trichloroethylene vapor degreaser, then through a nitric acid tank, two rinse tanks, and a hot air dryer.  The nitric acid rinse was known as "pickling" the slugs.  Meanwhile, a steel "sleeve" that would surround each can during the dipping process was cleaned in sodium hydroxide, and aluminum end caps and cans were cleaned in a sodium dichromate solution followed by a methanol rinse.  The bare uranium cores were dipped in a bronze bath to heat them to a uniform temperature within the uranium beta phase (660 C to 770 C), and then placed in a tin bath to (1) cool them into the uranium alpha phase (less than 660 C) and (2) remove excess bronze.  Next they were centrifuged to throw off excess tin.  Then the cores were immersed quickly in an aluminum-silicon brazing bath (also in the uranium alpha phase), and water quenched.  The various heating and cooling procedures were done to randomize the uranium grains, thus inhibiting the uranium "growth" (expansion under irradiation) problem.  After water quenching, the steel sleeve was pulled away and cleaned with sodium hydroxide and soap to remove any remaining aluminum-silicon.  The sleeve then could be reused many times.  The thickness of the residual end cap on the element was then measured with a fluoroscope and marked with a punch to indicate the amount that needed to be removed in subsequent end machining.  Identification numbers were stamped on the can base end, and the braze line on the end cap was tungsten inert gas (TIG) welded to seal the porous braze to the end cap and can.  A final etching in nitric acid completed the procedures.



1.1.4  Canning Tests


          Three tests followed the canning process.  The first, the frost test, consisted of spraying the can with acenaphthene mixed with carbon tetrachloride (CCl4).  The canned element was then placed into an induction coil to heat its surface.  If there was a gas bubble or a nonbonded spot, this spot would become shiny, and the element then would be rejected and sent back through a recycling process.  If the bond was good, the acenaphthene was removed with trichloroethylene, and the element was inspected in one of several autoclaves located in the 314 Building.  In that inspection, the canned element was placed into a steam autoclave, which operated at about 100 pounds (45.36 kilograms) per square inch gauge (psig) at 175 C for more than 20 hours, to reveal any pinholes or incomplete welds.  Water from the steam would be conducted through any such openings, and the uranium core would expand rapidly, resulting from the formation of a uranium oxide (UO2) compound known as U3O8, and split the aluminum can.  If an element passed the autoclave test it then underwent a final radiograph (X‑ray) test in the 314 Building, to detect porosity in the end weld bead.  Any porosity could have become a pathway for water to contact the uranium fuel and cause the element to rupture.[vi]



1.1.5  Additional Chemical and Hazardous Components


          In addition to the above‑mentioned chemicals, other hazardous substances were used routinely in early HEW fuel fabrication processes.  Aluminum cans and caps were cleaned using first trichloroethylene, then Duponol-M-3a (an industrial soap), phosphoric acid, and various rinses including methanol.  Steel sleeves were cleaned in sodium hydroxide and soap.  Caustic cleaners popular at HEW included Aluminux and Diversey‑415b, both containing primarily sodium dichromate.  Sodium hydroxide and sodium nitrate were used to strip aluminum and braze off the rejected uranium cores.  An intermetallic compound layer of uranium and copper (specifically UCu5) on the rejected cores was removed by using hydrofluosilicic acid.  Acetone and methyl alcohol (methanol) were used as all‑purpose cleaning and drying agents.



1.1.6  Process Changes


          In 1948, the extrusion press in the 314 Building was excessed, and HEW began receiving rolled uranium rods from an offsite commercial mill.  The rolling process seemed to offer metallurgical advantages, because the uranium could be processed at lower temperatures, which induced less oxidization and produced smaller and more random grains within the metal.  This type of grain within the uranium avoided the "pimpling and dimpling" of fuel rods, a persistent problem in early fabrication efforts.  It was also a less expensive process.  From 1950 to 1951, a rolling mill was procured and installed in the 314 Building, to save the costs of shipment to offsite mills.  However, this mill was relatively small, and the rolling operation was transferred to a large facility constructed at the Feed Materials Production Center (FMPC), an Atomic Energy Commission (AEC) site in Fernald, Ohio, in 1952.  Thereafter, no extruding or rolling operations were conducted at the Hanford Works (HW - the peacetime name given to HEW in 1947 by the AEC) in connection with the fabrication of fuel elements for single‑pass reactors.  The 314 Building process continued to operate for the purposes of straightening uranium rods, providing autoclave and radiograph testing of canned elements, and providing uranium scrap processing operations.[vii]



1.1.7  313 Building Expansion Under Eisenhower/Switch to Lead-Dip Process


          In 1954, the 313 Building underwent a major remodeling and expansion, reaching a total size of 182.5 feet (55.63 meters) by 486 feet (148.13 meters), with a total area of 76,633 square feet (7119.44 square meters).  At that time, much contaminated equipment and other solid wastes from this building and its immediate surrounding area and from the 303 fresh fuel warehouses were buried.  The remodeling occurred at the time that fuel canning technology in the 313 Building switched from the triple‑dip process to the new lead‑dip process.  Lead‑dip consisted of immersing the uranium fuel cores in a duplex bath (molten lead covered with molten aluminum-silicon) to preheat the cores in the uranium alpha phase.  This step formed an intermetallic compound of uranium and lead (UPb or UPb3) on the core.  It was followed by a molten aluminum-silicon bath (also in the uranium alpha phase) to braze and bond the cores to the aluminum cans and caps.  This process allowed the first canning bath to occur at a lower temperature (lower than 660 C) because the uranium cores already had been beta heat treated in a molten salt bath at the FMPC.  However, the new method introduced a great deal more lead and other heavy metals into 313 Building waste streams, because approximately 30,000 fuel elements were canned per week during the years of peak single‑pass reactor operations at HW (1955‑1964).  At about the same time that the lead‑dip process replaced the triple‑dip method, an ultrasonic test replaced the frost test, which eliminated the use of acenaphthene and CCl4.  Concurrently, the majority of testing autoclaves were removed from the 314 Building and placed in the north end of the 313 Building.  Hot Die Size Process.  In the early 1960's, just before the eight single‑pass reactors at HW began to close, experiments were under way in the 304, 3716, and 313 Buildings with a new canning procedure known as the Hot Die Size Process.  Also termed the "nickel‑plate" procedure, this operation plated uranium fuel cores with nickel, using nickel sulfate, nickel chloride, and boric acid.  It included standard fuel fabrication cleaning, degreasing, etching, and testing chemicals and processes.  Although the Hot Die Size method was tested successfully, it was not implemented on a large scale, because of the impending closures of HW's eight original reactors.[viii]  Cored and Internally and Externally Cooled (I&E) Fuel Elements.  In the 313 Building, additional fuel fabrication process changes during the 1950's and early 1960's included the manufacture of cored fuel rods beginning in 1954, internally and externally cooled (I&E) fuel rods beginning in 1957, and projection fuel rods in the early 1960's.  The cored rods, hollow elements with an aluminum plug at either end, bonded to the uranium with an aluminum-silicon braze, were designed to give the uranium an inner space in which to expand during irradiation.  The early, solid fuel elements were experiencing a troublesome level of distortion, and subsequent rupture, in HW's production reactors.  However, the cored fuel elements frequently developed cracks in both the uranium and the aluminum plug areas, and they were discontinued in 1957.  The I&E fuel elements, tried next, had a tubular hole down the middle, allowing cooling water to run both around and through them in the reactors.  Projection fuel elements, with small fins protruding from their sides, were of two types:  the bumper type had six short projections for use in ribbed process tubes, and the self‑supporting type had eight projections for use in ribless process tubes.



1.1.8  Projection Fuel Elements


          The switch to projection fuel rods represented yet another attempt to solve the fuel element rupture problem then plaguing Hanford's eight single‑pass reactors.  Power and fuel exposure level increases throughout the late 1950's and early 1960's had brought reactor operating temperatures to a point that seriously augmented fuel rod ruptures, with resultant increases in contamination released to the Columbia River.  Post‑irradiation examinations of failed I&E fuel elements showed that only about 20% of the failures resulted from fuel element "quality deficiency," while 80% resulted from longitudinal corrosion attack caused by warp.  Known as "side hot‑spot" ruptures, these failures were caused by positioning of the fuel rods in the process tubes.  The new projection fuel elements, first tested in 1961 in reactors at HW, were manufactured in the 313 Building through the use of ultrasonic welding.  Canned fuel elements first were dipped in a tank to deposit an Ivorya soap film, useful in achieving a good weld.  After the projections were welded, the soap film would be rinsed off in a three‑compartment rinse using standard fuel fabrication chemicals and degreasers.[ix]



1.1.9  End of Single-Pass Reactor Fuel Making


          Fuel element preparation activities for the single-pass reactors ended in the 313 and 314 Buildings in 1971, when the last of these reactors closed.  The 314 Building was modified in the 1970's and was used for a variety of research projects and crafts services.  The majority of the fabrication equipment for single-pass reactor fuel elements was removed from the 313 Building between the mid‑1970's and the mid‑1980's.  However, the south end of the 313 Building continued to house major functions in support of N Reactor fuel production.  Among these functions were the receiving and inspection of uranium billets and other components used to make N Reactor fuel elements and the chemical passivation of spacers from N Reactor, the casting and machining of copper‑silicon preshape components used in N Reactor fuel elements (beginning in 1973), and the neutralization and handling of non‑uranium‑bearing acid wastes from N Reactor fuel fabrication processes in the 333 Building.  Finished N Reactor fuels and fabrication components, tools, and miscellaneous supplies were stored in the north end of the 313 Building from 1971 to 1987, and an Engineering Development Laboratory, including facilities for working with uranium, was established in the structure in the 1970's.  In 1983/1984, a Suttonb extrusion press was purchased and placed in the 313 Building as a backup for the extrusion press operating in the 333 Building performing N Reactor fabrication work.  However, the shutdown of N Reactor operations in December 1986 precluded use of the Sutton press.



1.1.10  Other 313/314 Building Processes


          Over the years, several other ancillary or off-shoot processes have taken place in the 313 and 314 Buildings.  Among these have been U scrap recovery operations, experimental and/or small-scale fuel making ventures, and waste treatment procedures.  From its earliest days, concern of the Manhattan Engineer District (MED - earliest federal management agency over HEW) about the adequacy of uranium supplies brought strict policies that mandated the reclamation of all possible uranium scraps at federal atomic sites.  During the earliest fuel fabrication operations at HEW, difficulties with early fuel canning techniques produced thousands of rejected cores, lathe turnings, metal oxides that formed when canned slugs failed in autoclave tests, and other scraps by mid-1944.  That June, Du Pont reported that "all available space" around the 313 and 314 Buildings was filled with cans of scrap, and the fabrication area fence had to be moved about 30 feet (9.14 meters) east of fresh fuel storage building 303‑J to allow for more storage space.  Several can fires occurred.  Beginning with the startup of extrusion press tests in January 1945, extrusion butt ends, oxides, and container residues collected, along with acids from the slug pickling process and from the slug recovery process.[x]


          At first, the various types of scrap were shipped to offsite reclamation processing centers.  By 1946, however, the volume of uranium scraps accumulating and the expense and fire and security hazards of shipment brought a change in policy at HEW.  A "chip recovery" operation began in the 314 Building.  It operated only a few days a month and involved collecting all chips and turnings from machining operations, sorting them, breaking them into small pieces, washing, drying, and then pressing them into briquettes.  At first the briquettes themselves were shipped offsite.  In May, however, the MED ordered briquetting to be discontinued, due to a number of uranium chip fires within the centrifuging step at other sites.  A "melt plant" was established in the 314 Building in late 1947.  In that process, "new" uranium could be made by combining uranium tetrafluoride (UF4 or "green salt") and either calcium chips or magnesium chips.  This mixture was placed in a dolomite-coated steel vessel, heated until free molten uranium separated from magnesium fluoride or calcium fluoride, and then allowed to cool.  The molten uranium settled into large buttons shaped like Derby hats (called "Derbies" by HW workers).  Slag was jackhammered off the Derbies, which were mixed with the recycled uranium scraps and briquettes, melted in a vacuum furnace, and cast into ingots.  These ingots were then rolled into new uranium rods, either offsite or at Hanford, and used to make additional fuel rods.


          In the spring of 1946, an additional scrap recovery operation known as the "oxide burner" began on the north side of the 314 Building.  All uranium‑bearing dust and particulate matter that could be collected from the fuel fabrication facilities, as well as the tailings or settlings from washes and quenches, was burned to convert it to oxide (powder) form.  The UO2 was then collected in 5‑gallon (18.93 liters) buckets for compact shipment offsite.[xi]


          From the outset of chip recovery operations in 1946, HW's Health Instruments (H.I.) Division detected serious radiological problems with this process.  Throughout 1946 and 1947, monitors reported that oxide burner operations were really spreading metal dust and oxide around the 314 Building, producing airborne contamination samples over tolerance.[xii]  In December 1947, the oxide burner operation moved to a separate building north of the 314 Building.[xiii]  Both melt plant and oxide burner operations were phased out at HW between 1952 and 1954.  The burnout of slag from used melt crucibles was completed, and the furnace was excessed to the 300 Area Burial Grounds by late summer 1954.  Thereafter, solid uranium scraps at HW continued to be collected, stored, and combined with solids collected from neutralized, uranium‑bearing waste acids and processed through a press‑and‑frame filter press in the south end of the 313 Building.  Together, all of these scraps were slurried into sodium diuranate, stored in the 303 Buildings area, and shipped in barrels to the FMPC.[xiv]


          From 1944 through the 1950s, bismuth fuel targets welded into nonbonded aluminum cans, irradiated to make polonium‑210 in 100 Areas production reactors, were fabricated in the 313 Building.  Polonium‑210 was the initiator in atomic (pre‑hydrogen and non-hydrogen) weapons explosions.  An even larger number of lead-cadmium fuel rods, also welded into nonbonded aluminum cans, were produced for use as "poison" elements in the 100 Areas reactors and in the 305 Test Pile.  The term "poison" refers to the ability of these neutron absorbing metals to slow down or even kill (control) nuclear chain reactions.  The production of lead‑cadmium fuel rods continued throughout the years of single‑pass reactor operations (through 1971).  Additionally, lithium-aluminum alloy fuel targets, manufactured for the P‑10 project at Hanford's 100‑B Area to produce tritium for the world's first hydrogen weapons tests, were canned in nonbonded aluminum cans in the 313 Building from 1949 to 1952.


          During the early 1950s, a number of attempts were made to fabricate and jacket metallic thorium fuel targets in the 313 Building to produce uranium‑233.  Many problems connected with the rapid formation of a thick coat of oxide on the thorium metal targets led to experiments with a variety of bonding methods and coatings.  Eventually, thorium oxide (ThO2) powder and wafer fabrication was carried out in the nearby 3722 and 3732 Buildings in the late 1960's.  Beginning in the late 1950s and continuing until 1971, a process to electrolytically anodize the aluminum "spacers" (dummy fuel elements) used in the single‑pass reactors (to create a protective aluminum oxide [Al203] coating) was added in the 313 Building.  The passivation of N Reactor steel spacers to reduce rust formation also took place in the 313 Building from the mid‑1960s through the mid‑1980s.[xv]  Also, highly enriched uranium-aluminum fuel cores, used as driver elements in the early tritium production program and in a mid‑1960's uranium‑233 production program in the N Reactor, were manufactured and canned in nonbonded aluminum cans in the 313 Building.


          Beginning in 1954, waste acids containing recoverable amounts of uranium from the 313 and 333 Buildings were routed to designated tanks in the 313 Building, neutralized, routed to another tank, and passed through a press-and-frame filter press.  The precipitate remaining on the filter press was known as "C‑6" sludge, and was collected and placed in barrels for shipment to the FMPC.  The centrifuging operation, along with waste acid storage tanks, anodizing tanks, and the filter press used to separate sodium diuranate from uranium‑bearing, neutralized wastes, was located in the south end of the 313 Building.  A process to recover uranium cores from rejected, lead‑dip canned fuel elements also began in the south end of the 313 Building in 1954.  Boiling sodium hydroxide was used to remove the intermetallic compound layer of lead and uranium from the elements.  Beginning in 1975, the 313 Building played a key role in a new Waste Acid Treatment System (WATS) process that was emplaced in connection with the nearby 333, 334 and 334A Buildings.  The WATS process operated until 1987.





          The fuel-making process for the New Production Reactor (N Reactor) was very different from that used to make fuel for Hanford's single-pass reactors.  Soon after funding was secured for N Reactor in 1958, a high pressure heat transfer apparatus was emplaced in the 189/190-D Building, a converted World War II pumphouse in the Hanford Site's 100-D Area.  Its purpose was to test a new, N Reactor fuel concept being developed in the 306 Metallurgical Pilot Plant, a 300 Area building dedicated to fuel manufacturing experimentation.  The concept first tried for N Reactor fuel was a wire-wrapped, seven-element cluster of long, thin fuel rods spaced together in a horizontal flow tube.  Each individual element was only 0.625 to 0.704 inches (1.59 to 1.79 centimeters) in diameter, and was 35 to 45 inches (88.9 to 114.3 centimeters) long.  As such, the heat transfer and flow properties of these elements were very different from those of the solid U or I&E fuel elements previously used at Hanford.  An understanding of every characteristic of the new elements, including subcooled and boiling burnout and pressure drop parameters, was essential if they were to be recommended for N Reactor use, so trials continued throughout 1959.[xvi]  However, attention soon turned to yet another new concept developed in the 306 Building.  This idea, of a co-extruded tube-in-tube fuel element design, eventually was adopted for N Reactor.  A full-scale, experimental heat transfer test section that simulated the downstream half of a tube-in-tube charge in N Reactor was built on the mezzanine of the 189/190-D "flow laboratory."[xvii]



1.2.1  The 333 Fuels Manufacturing Building


          In the meantime, construction of the new 333 Fuels Manufacturing Building, to produce N Reactor fuel elements on a plant scale, was being constructed just east of the 313 and 314 Buildings.  Building design itself did not depend on knowing exactly which manufacturing process would be used, but once the co-extrusion process was selected, the equipment eventually procured and constructed in the 333 Building was unique.  The 333 Fuels Manufacturing Building itself was constructed of steel frame with double metal insulated panel exterior walls and lightweight metal panels for interior partitions.  The foundation and floors were poured concrete.  The roof consisted of insulated metal paneling covered with felt and roll tarpaper and a tar and gravel surface.  The roof was refinished in 1962.  The structure was 300 feet (91.44 meters) by 140 feet (42.67 meters), with a total area of 48,817 square feet (4535.25 square meters).  In 1980, in response to anticipated increases in production, a small addition was placed on the northwest corner of the 333 Building.  It consisted of two stories; the ground level an open bay shop and the second story for offices.  The addition was 33 feet (10.06 meters) by 104 feet (31.70 meters), and runs from the HVAC (heating, cooling and ventilating) supply units on the west side of the building to the north exterior wall.


          A majority of the 333 Building was a large, one story, open bay housing large machinery for fuel-making, but the structure also contained two mezzanines.  The larger mezzanine ran along the east wall and housed distribution equipment and offices.  The smaller central mezzanine housed ventilation equipment for the chemical bay.  Air conditioning and heating of the building originally was accomplished with steam heat and evaporation cooling forced air equipment located in a 30-foot (9.14 meters) by 75‑foot (22.86 meter) enclosure adjoining the west side of the building.  During 1979-80, some energy conservation upgrades and cleanouts were made in this system.  New heat recovery systems were installed.  The 333 Building has always been equipped with electrical fire detection mechanisms and an automatic sprinkler system.  The co-extrusion process was carried out with various equipment pieces, but the most prominent and unique of these was a Loewy Press that actually pressed all of the fuel components (U core and all of the cladding components) together in one unit.  Each N Reactor fuel element was 26 inches (66.04 centimeters) long, weighed approximately 52 pounds (23.59 kilograms), and had a tube-in-tube configuration with a coolant channel running down the entire length of the element.  Projections also were welded onto each element, as the N Reactor process tubes were smooth or "ribless."  The co-extrusion process provided a better, more uniform bond between core and jacket that had been possible with older methods based on dipping.  The new method was beneficial in smoothly cladding the inner and outer tubes so that they would fit together without developing "hot spots."



1.2.2  Co-Extrusion Process


          The co-extrusion process began with inspection and cleaning of copper and copper-silicon pre-shapes and backing plates used in the process.  The cleansing agents were nitric acid, nitric hydrofluoric, and chromic nitric sulfuric acid.  Next, cladding components made from Zircaloy-2 were degreased, rinsed in nitric and hydrofluoric acid, and dried with forced-air heating.  In the meantime, U billets were degreased with perchloroethylene, etch with nitric acid, rinsed, dried and inspected.  Next, the copper, copper-silicon, Zircaloy‑2, and U components were assembled and welded into a billet assembly.  This assembly was evacuated of air, leak tested, sealed preheated, and then co-extruded (squeezed together) in the Loewy Press.  As the process specifications for this step emphasized:  "The quality of the extruded tube is dependent upon many things, not the least of which is skill, care, effort,and precision that are put into the co-extrusion operation."[xviii]


          The process of cleaning, degreasing, etching and drying components, then assembling and pressing them, was repeated for both the outer (larger) and inner (smaller) tubes that made up the tube-in-tube configuration.  The extruded tubes then exited the press to a roll-out table where they were rolled continuously for at least six minutes to prevent tube deformation and non-uniform cooling.  Next they were sectioned to the specified length, and the ends were machined to create fuel sections or elements.  Nitric acid was used to remove copper silicon residues, and nitric sulfuric acid was used to chemically mill (i.e., dissolve away) excess uranium on fuel element ends.  Elements then were etched with nitric hydrofluoric and nitric acid, and brazed with an etched braze ring material consisting of Zircaloy-2 alloyed with about five percent beryllium.  (This braze material previously had been degreased and etched.)  The brazed elements were heat-treated in a molten salt bath to randomize the U grain structure to prevent preferential grain growth that could rupture the elements in the reactor.


          The next step in the process was to weld projections or supports onto the fuel elements.  Eight lengthwise protrusions were attached to the outer surface of each fuel element, evenly spaced around its diameter.  This configuration allowed cooling water to circulate optimally around the elements, without creating hot spots where the sides of elements rested too close to the inner walls of the process tubes.  After projections were welded onto the elements, the two tubes (inner and outer) had to be attached together.  Support hardware was attached to the outer surface of the inner tube, and locking hardware was affixed to the inner surface of the outer tube.  The two tubes then were given a final nitric hydrofluoric acid etc, separately tested in autoclaves, inspected, assembled and interlocked, and stored as finished fuel.  The coextrusion process was carried out continuously in the 333 Building from 1960 until December 1986, reaching a peak volume of approximately 250 finished fuel elements per week in the mid-1980s.[xix]



1.2.3  Other Processes in the 333 Building


          From 1965 to 1967, the 333 Building performed autoclave testing, final etching with nitric‑hydrofluoric acid, and inspection of special lithium aluminate fuel targets made in the nearby 3722 Building for the production of tritium.  Highly enriched (2.1% uranium‑235) uranium driver fuel elements for tritium programs also were made in the 333 Building from 1965 to 1970.



1.2.4  The Waste Acid Treatment System (WATS) Process


          In 1971, a study of radioactive releases and special materials accounting practices identified several areas of concern in 333 Building operations.  Among these concerns were the amounts of contaminated gaseous, particulate and liquid discharges, and the need for expansion of monitoring and sampling systems.  Partly in response to these concerns, the Waste Acids Treatment System (WATS) process was developed, a new system to catch and neutralize waste acids from the structure's fuel-making processes.  In 1973, the WATS began partial operations to treat waste acids from 333 Building operations.  It operated for four months in 1973 and became fully operational in January 1975.  The 300 Area WATS process represented a method to prevent 333 Building fuel fabrication bulk waste acids from discharging to the 300 Area process sewer.


          Tanks and control instruments for the WATS system were located in and below the 334‑A Waste Acid Storage Facility, a small steel frame structure that was moved in close to the 333 Building, from Hanford's 200 Area.  The portion above grade was used for general storage of products and absorbents, and the portion below grade contained three tanks seated in a reinforced concrete pit 18.5 feet (5.64 meters) by 18.3 feet (5.58 meters) by 10 feet (3.05 meters) (deep).  Additional tanks and piping components for the WATS system were located in the 313 Building, the 333 Building, the 334 Chemical Handling Facility next door to the 333 Building, and in the nearby 311 Tank Farm.  The 303‑F Building, also nearby, served as the pumping station for the various liquid and slurry waste transfers in the WATS process.  During most of the years of WATS operation (1975 to 1988) the tanks in the 334‑A Building received approximately 210,000 gallons (794 936.492 liters) of waste acids per year.[xx]


          The waste acids treated in the WATS operation included nitric, sulfuric, hydrofluoric, and chromic‑nitric‑sulfuric acids bearing uranium, Zircaloy‑2 components, copper, beryllium, and other fuel fabrication materials.  Waste acids were collected in the 334‑A Building tanks and then pumped to the 313 Building for neutralization with sodium hydroxide.  Wastes containing recoverable amounts of uranium were routed directly from the 333 Building to the 313 Building and were not treated as part of the WATS process.  Waste acids containing nonrecoverable amounts of uranium were pumped to the 313 Building for neutralization and, beginning in 1985, were centrifuged to remove solids.  Solids from the centrifuge were placed in drums and transferred to the 303‑K Radioactive Mixed Waste Storage Facility or to the Central Waste Complex in Hanford's 200 West Area for eventual disposal.  Filter press effluent and centrifuge effluent from 313 Building operations then was pumped to the 311 Tank Farm for storage and transported to Hanford's 100-H Area for evaporation.  Beginning in 1985, some neutralized waste effluents from the 333 Building were shipped from to Hanford's 340 Retention and Neutralization Complex for transshipment to the 200 Areas or offsite for disposal.[xxi]




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