The plant was located in the rural town of Fernald which is about 20 miles northwest of Cincinnati, Ohio and occupies 1,050 acres. This location was chosen because it was between the uranium ore delivery ports of New York and New Orleans, and it was accessible to the other main AEC sites. In addition, the site was close to Cincinnati’s large labor force, the landscape was level making the site’s construction easy, it was isolated which provided safety and security, and it was located 30 to 50 feet above the Great Miami Buried Valley Aquifer2, one of the nation’s largest drinking water aquifers, which supplied the large quantities of water needed to machine uranium metal.
From 1951 to 1989 Fernald converted uranium ore into metal, and then fabricated this metal into target elements for nuclear reactors that produced weapons-grade plutonium and tritium. Annual production rates ranged from a high in 1960 of 10,000 metric tons to a low in 1975 of only 1,230 metric tons.2 Making uranium metal was a very complex process requiring a series of chemical and metallurgical conversions that occur in nine specialized plants. The purpose of this document is to describe this very complicated process.
Releases from the Fernald site to the surrounding area resulted in exposure to community residents, including ionizing radiation, especially radon, soluble and insoluble forms of uranium, and various chemicals. The Centers for Disease Control and Prevention (CDC) has conducted a historical exposure characterization and developed dose estimation models through the Fernald Dose Reconstruction Project, with an endpoint of developing an algorithm to estimate doses to individual persons who lived within the exposure assessment domain (the area within a ten kilometer radius from the center of the plant site). In addition to radioactive materials, many other non-radiological toxic substances were present in the production area as materials, by-products or products. Workers were exposed to chlorinated and non-chlorinated solvents, metals and metal salts, and nuisance dusts.3-10 Community residents also may have been exposed to these substances through ground water pathways, soil contamination, and air dispersion of emissions from the site.
Two separate medical surveillance programs, for former workers and community residents, have been funded by settlements of class action litigation against National Lead of Ohio, a contractor for the DOE. These Fernald Settlement Funds are administered by the US Federal Court, which maintains oversight of the Fernald Medical Monitoring Programs. The Fernald (Residents) Medical Monitoring Program (FMMP) is a voluntary ongoing medical surveillance program for community residents living within five miles from the perimeter of the Fernald site, and the Fernald Workers Medical Monitoring Program (FWMMP) is a program for former workers who were employed when National Lead of Ohio was the contractor. Activities of the medical monitoring programs include both periodic medical examinations and diagnostic testing and yearly questionnaire data collection.
As of January 1, 2007 there are 9764 persons enrolled in the FMMP and 2716 former workers enrolled in the FWMMP. The FMMP has an extensive computer database available for research studies. Samples of whole blood, serum, plasma and urine were obtained from all FMMP participants at the time of the initial examination, and over 100,000 one-ml aliquots of these biospecimens have been stored at minus 80o C since then. For more information about the Fernald Medical Monitoring Program see their website:
Q-11 was received in 55-gallon drums. The drums were deheaded prior to processing and were conveyed through a thawing tunnel, which also provided surge capacity of deheaded drums. The drums were lifted to the top of the building by a skip hoist where they were emptied into a surge hopper that feeds the magnetic separator and jaw crusher. From the jaw crusher, the one-half inch material passes through a rotary drum dryer to a system of conveyors, which conveys the material to a surge hopper that feeds the ring roll mill. The particle size output from the mill was controlled to about 100 mesh by an air classifier mounted directly on the mill. The undersized material was blown to a cyclone separator that was mounted directly above the first Gallagher sampler. The three Gallagher samplers in series each took a 10% cut of the stream fed to it, producing a sample approximately 0.1% of the original lot size. The main stream was conveyed to a drumming station where it was packaged in 55-gallon or 30-gallon drums for use in the Refinery. The official weight was taken at this point.13
The INX line was similar to the Q-11 line except that the thawing tunnel has been omitted and a hammer mill and bucket elevator replaces the jaw crusher, rotary dryer, ring roll mill, air classifier, and cyclone separator.
In addition to sampling incoming ores this Plant reconditions 30 and 55 gallon drums which are used to transport and store radioactive materials onsite. It also contains a safe-geometry digestion system used to process enriched uranium materials assaying up to 5% 235U. This digester was so named because the piping was of such a diameter and distance between pipes making a criticality incident nigh impossible.14
The principal function of Plant 2/3 was uranium purification and conversion of uranium bearing materials into uranium trioxide (UO3), or orange oxide. There are three principal forms of uranium residues, each having a separate processing route for putting the uranium into solution. Uranium oxides are dissolved in 6000 gallon vats of pure nitric acid in the Oxide Digester (also known as the west metal dissolver), miscellaneous residues which required filtration were dissolved in the Slag Leach Digester21, and metals were dissolved in the Metal Dissolver. If the ore was poured too rapidly into the nitric acid vats a condition known as a “boilover” results. The acid literally generates so much gas that it becomes a foam and “boils over” the sides of the vat just like dropping Alka Seltzer into a glass of water. Many workers were told to not step in any puddles on the floor as they were probably nitric acid left from one of these “boilover” incidents. The site employed their own Cobblers just to repair work boots that had been exposed to too much acid. Another hazard was the Nitrous Oxide fumes coming off the nitric acid vats. There were so many fumes that on high humidity days during the Summer there appeared to be an orange cloud encasing this building and anyone just walking past would experience a sensation as if he had wandered into a swarm of bees; the fumes bonding with the water droplets from the humidity made a dilute nitric acid.
The resulting UNH (Uranium Nitrate Hexahydrate) material pumped out of the vats was then processed through extraction to purify the solution. The UNH solution was passed through a multi stage liquid-liquid counter current tower with TBP (tri-butyl phosphate) and kerosene to extract the uranyl nitrate. The impurities exit the tower as the raffinate stream for further processing. The extract solution was passed through another counter current extraction tower to re-extract the uranyl nitrate from the organic into deionized water. The organic was then processed through a wash to be recycled back through the extraction process. The resulting UNH solution was in a pure form for further concentrating and thermal denitration to UO3, named Orange Oxide by the plant workers because of its physical resemblance to Orange CoolAid drink mix.
The UNH solution was concentrated through a process known as Boildown. In this process heat was applied to the solution from steam coils inside the boildown tanks. As the boiling point of the solution was obtained the water was removed through evaporation thus concentrating the solution. The solution was concentrated from 90 grams uranium per liter to 1300 grams uranium per liter in two stages.
The concentrated solution now in 250 gallon batches was further heated, in a process known as Pot Denitration, to thermally denitrate the UNH to UO3. The UO3 material was then pneumatically removed from the denitration pots and packaged out in hoppers with a capacity of 3.6 metric tons or 55 gallon drums. This pneumatic transfer of the product was known as Gulping.22, 23
Orange oxide was received from the Refinery in five-ton mobile hoppers, which were mounted on seal hoppers to feed the reduction furnace at a rate of approximately 375 pounds per hour for producing metal grade UF4. The powder was agitated and carried through the reduction furnace by a ribbon flight screw. Dissociated ammonia was metered to the reduction reactors and passed counter-currently to the bed of uranium oxide within the reactor. Note: these were chemical reactors, not nuclear reactors. The off-gases from the reduction reactors were passed to a hydrogen burner where the excess hydrogen was burned and then passed through a dust collector to remove any entrained brown oxide [UO2] that might have been present. The brown oxide in the reduction furnace passed through a seal hopper and a feed screw to the first of the three hydrofluorination furnaces. The bed of brown oxide was moved through the hydrofluorination furnace by ribbon flight screws and contacted counter-currently by hydrofluoric acid vapors. The UF4 was removed from the third furnace and conveyed to a packaging station where the product was packaged in 10-gallon pails for use in the Metal Plant, or in 5-ton containers for shipment to the cascades. The off-gases containing water vapor formed in the reaction and excess hydrofluoric acid was removed from the first furnace and were sent to hydrofluoric acid recovery. The gases first passed to a partial condenser that removed all of the water in the form of 70% aqueous hydrofluoric acid. The remainder of the gases was then passed to a total condenser, which condenses the remainder of the acid as anhydrous hydrofluoric acid. The gases at this point contain only the nitrogen from seals and purge gases and small amounts of hydrofluoric acid that did not condense in the total condenser. These were passed through potassium hydroxide scrubbers to remove the last traces of acid and then discharged to the atmosphere.2, 25, 26
The primary hazard here was the HF acid. This acid is so potent that it is used to etch glass. As such, normal piping and Teflon seals would deteriorate resulting in several HF gas leaks which in turn caused the building to be evacuated with everyone making quick decisions on which way was upwind to get as far away from the fumes as possible. Those who were unfortunate enough to come into contact with HF spent the remainder of the shift soaking the injured body part in ice water to relieve the pain.
The conversion of UF4 to massive metal was accomplished by the thermite reduction of green salt with magnesium in a refractory lined steel reaction vessel or bomb. Four hundred and fifty pounds of green salt were blended with approximately 72 pounds of magnesium. The resulting mixture was uniformly packed into the reduction bomb, which has previously been lined with refractory slag in a jolting apparatus. Following these steps, the bomb was capped with refractory, sealed, and placed in one of 49 electric muffle furnaces. The furnace temperature was raised to approximately 1,225o F and after about four hours the thermite type reduction reaction occurs: UF4 + 2Mg → 2MgF2 + U (metal). The charge was then allowed to separate and cool in the furnace for 10 minutes, after which it was removed and cooled to room temperature. Finally, the solidified massive uranium metal (derby) was separated from the slag and liner materials in a sequence of manual and mechanical operations which take place at the breakout station. The yields expected from this operation were about 95%. There are many documented explosions of these furnaces due to improperly packed refractory lining or a magnesium flare. Whatever the cause, the building would fill with radioactive smoke along with a real probability that molten uranium metal would come pouring out of the bottom of the furnace.
The MgF2 slag from the breakout station was conveyed to the slag recycling plant, where it was stored awaiting processing for reuse as refractory liner. The slag recovery process consists of crushing, pulverizing, and classifying the slag, which was then transferred back to the reduction area for use.
The next step in the plant consists of melting massive uranium metal and casting an ingot. Graphite crucibles were loaded with a charge of derbies and solid recycle scrap. The loaded crucibles were then mechanically positioned in induction melting and casting furnaces that were designed to give a maximum of flexibility and a minimum of human exposure to radioactivity. The uranium metal was melted under high vacuum to minimize contamination of the melt with atmospheric gases and to permit purification of the metal by distillation of volatile contaminants. At approximately 2,550o F, the molten metal was poured into a graphite mold and the ingot was allowed to cool and solidify. Additional equipment was provided for the ingot to be removed from the mold, weighed, cropped, sampled, and stored for further processing in the Metals Fabrication Plant [Plant 6]. The ingot was approximately 7" in diameter, by 45" long, and weighs about 1,200 pounds.sup>2
Uranium ingots were charged into an automated ingot preheat furnace where they were lowered into a Li2CO3-K2CO3 molten salt to be heated to 1,150o - 1,200o F before being discharged singly to the mill table. The ingot was passed back and forth through the blooming mill until it was reduced to an oval billet approximately 2" to 2-1/2". The ends of the billet were then cut off by a cropping shear before it was pushed into an equalizing furnace. The billet was reheated to 1,150o - 1,200o F in the equalizing furnace and was then discharged into the finishing mill. The finishing mill consists of six stands which reduce the rod to the final diameter of 1.43" for Hanford rods, and 1.12" for Savannah River rods.29
The rods were cut into 22' lengths as they leave the last stand by means of a flying shear. The Savannah rods were air cooled to room temperature on the cooling bed and then were cold straightened in a Medart Straightener. Rods to be beta heat treated by-pass the cooling bed and were lifted into the beta heat treating furnace by means of a hoist, to be held at 1,320o - 1,365o F for 11-20 minutes and then quenched in cold water. After quenching, these rods were conveyed to the Medart straightener for straightening. The rods were located in 2-5/8" Acme-Gridley automatic screw machines where slugs were cut from the rods. The Hanford slugs were then placed in the Heald machine, which cuts the slugs to desired lengths and finishes and radiuses the ends. The Savannah River slugs were reduced to exact dimensions of size, surface, and straightness on a centerless grinder after which a contour was placed on the surface by a thread rolling machine. The slugs were numbered and put on a basket on a conveyor that passes through a degreasing tank, pickling tank, two rinse tanks and a hot air dryer before depositing the slug basket in the Inspection Department. The slugs were inspected for seams, striations, dimensions and handling defects with the good slugs being packed for shipment.2
In addition to the solid slugs produced in Plant 6, hollow fuel element production was started about January 1, 1956. Hollow slug blanks were produced over-size on a 2-5/8" RB-6 Acme-Gridley machine and were centerless ground before the drilling operation. The oversize slug blank was then loaded into a magazine loader on a 1-5/8" Acme and thence through a four step drilling operation making a hole halfway through the blank. The blank was then reversed and again placed in the magazine loader. After a four step drilling sequence produces a hole all the way through the blank, a reamer was passed through this hole in the final position. The oversize Outer Diameter was turned concentric with the finished Inner Diameter on an automatic Sundstrand lathe. Subsequent operations were the same as those for the solid slug.2
Bomb liner material received from Plant 5 in mobile hoppers was emptied at an unloading station and elevated to a surge hopper. Material as needed was sent from the surge hopper through a jaw crusher and into a shelf type oxidation furnace. Here the metallic uranium was oxidized to black oxide (U3O8). The material discharged from the furnace was lifted to a surge hopper and then as needed was sent through a roll mill and ground to -325 mesh size. It was then fed into carbon brick digestion tanks where the uranium was dissolved in hydrochloric acid containing a little sodium chlorate. The undissolved solids were filtered off and dumped into a truck which hauls the spent material to a scrap dump. Uranium in the filtrate was sent to a precipitation tank and precipitated with ammonium hydroxide (NH4OH), in presence of phosphoric acid to form UAP (uranyl ammonium phosphate). The resulting slurry was filtered and the uranium bearing cake was introduced to a drying furnace. The dried UAP was sent to the refinery. In addition to the wet system described, several furnaces were installed in the plant for massive metal oxidation, pyrohydrolysis, drying, chip and sludge combustion, etc. Most of the furnaces can be used for more than one of the above operations.2
During the summer of 1962, a new facility was started in Plant 8 for the production of UF4 by an aqueous precipitation technique known as the Winlo process.33 The Winlo process was developed for the low-cost chemical conversion of relatively pure uranium concentrates to green salt by a hydrometallurgical process.34 The feed to the plant Winlo system was made up of a combination of black oxide (U3O8) generated by burning metallic residues, uranyl chloride solutions generated by dissolving massive metal residues in hydrochloric acid, and uranyl pyrophosphate (UAP) produced from low-grade residues in the hydrometallurgical recovery system.35
A brief description of the Winlo process follows:
The Pilot Plant met the needs of development projects and special orders. Some of the equipment that was available for and had been used in enriched processing was as follows:22
CDC National Center for Environmental Health, Radiation Studies, Project Profiles, Fernald. Includes a description of the Fernald Dosimetry Reconstruction Project and the Fernald Risk Assessment Project.
A brief description of the history of the site was issued on the 50th anniversary of the opening of the plant:
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