APPENDIX A. FACILITY AND PROCESS DESCRIPTION
A.1 F-Canyon Facility Description
The Savannah River Site (SRS) F-Canyon (see Figure A-1) is a reinforced concrete structure, 255 meters (836.6 feet) long, 37 meters (308 feet) wide, and 20 meters (121.4 feet) high. It is named for the two areas, or "canyons" that house the large equipment (e.g., tanks, process vessels, evaporators, etc.) used in the chemical separations processes performed in the facility. These areas resemble a canyon in that they are long (170 meters or 557.7 feet), narrow (an average of 6 meters or 19.7 feet), and deep (20 meters or 65.6 feet). The canyons are parallel, and open from floor to roof. A center section, which is divided into four floors or levels, separates the canyons. The center section contains office space, the control room for all facility operations, and various support equipment such as ventilation fans. Figure A-2 is a cross-section view of the F-Canyon facility. The processing operations involving high radiation levels such as dissolution, fission product separation, and high-level radioactive waste evaporation (these processes are discussed below in greater detail) are performed in the "hot" canyon, which has thick concrete walls to shield people outside the facility and in the center section from radiation. The final steps of the chemical separations process, which generally involve lower radiation levels, are performed in the "warm" canyon. Services that are typical for a large industrial facility are also required to support F-Canyon operations. For example, steam is required to heat process vessels and is the motive force for transferring solutions through process cycles; lights, motors, control systems, etc. use electricity; compressed air provides pressure needed for various process monitoring systems (e.g., liquid level indicators) and powers some control systems; and a ventilation system provides conditioned air for the comfort of facility workers and for control of the environment for the operation of sensitive equipment. A special separate ventilation system serves portions of the facility that contain the radioactive process equipment, such as the hot and warm canyons. This special system ensures the air pressure in areas with the process equipment is below the pressure of the air outside the facility and the area occupied by workers. This design helps prevent the release of radioactive material outside the facility by ensuring air always flows from the outside of the facility to the inside of the process areas. Air in the process areas is exhausted from the facility through a large filter that is designed to remove 99.5 percent of any airborne radioactive material before the air is discharged to the atmosphere [via a 61-meter-tall (200-foot) stack behind F-Canyon]. This atmospheric discharge is the pathway for the airborne radionuclide emissions associated with the normal operation of F-Canyon. Figure A-1. F-Canyon and FB-Line facilities. Figure A-2. F-Area Canyon building sections. There are two pathways for liquid effluents from F-Canyon: - Condensates from secondary evaporators (A-Line Outside Facilities) containing low levels of radionuclides are discharged to the Effluent Treatment Facility (ETF) where there is further decontamination, if necessary, before discharge to Fourmile Branch. - The cooling water system provides cooling for the hot and warm canyon process vessels. Underground pipes carry water to the F-Canyon, where the cooling water system distributes it. The water passes through coils inside the vessels (Figure A-3 shows a standard canyon process vessel) and then flows back out of the F- Canyon. Constant monitoring would detect radioactivity in the water in the event of a cooling coil leak. If radioactivity were detected, the water would be diverted to a treatment facility where the radioactivity would be reduced below applicable limits before it was discharged to Fourmile Branch.
A.2 F-Canyon Chemical Separation Process (PUREX Process)
This section describes typical historic operations, not necessarily operations that DOE would resume in the alternatives discussed in this eis. The PUREX process consists of several major operations referred to as "unit operations," which yield two products, uranium-238 and plutonium-239 (in solution form). These unit operations are dissolution, head end, first cycle, second uranium cycle, and second plutonium cycle. Unit operations that support the product recovery process are high-activity waste, low-activity waste, and solvent recovery. Figure A-4 shows the general PUREX process flow. There are about 303,000 liters (80,000 gallons) of in process plutonium solutions stored in F- Canyon. No new material would be introduced to the process.
A.2.1 DISSOLUTION
Irradiated material, called targets, are brought into the south end of the hot canyon by rail car through an air lock. Each target consists of depleted uranium formed in the shape of a cylinder, which has been clad in aluminum. These targets have been irradiated in SRS production reactors to transform a portion of the depleted uranium into plutonium-239. Large water-filled casks, which are transported on rail cars, contain the targets (see Figure A-5). The targets are removed from the casks and loaded into a large tank called a dissolver. The aluminum cladding is removed from the targets with sodium hydroxide. The cladding solution is then transferred to the high-level waste tanks. Heated nitric acid in the tank dissolves the target, resulting in a solution containing depleted uranium, plutonium-239, and any fission products from the reactor irradiation process. Figure A-3. Standard canyon process vessel. Figure A-4. Historic PUREX Process Flow. Figure A-5. Rail car with cask.
A.2.2 HEAD END
The head end process is performed in two steps to prepare the target solution so that uranium and plutonium can be separated. First, gelatin is added to precipitate silica and other impurities. Then the solution is transferred to a centrifuge, where silica and other impurities are removed as waste. The clarified product solution from this process is adjusted with nitric acid and water in preparation for the first cycle unit operation in the PUREX process. The waste stream generated from the process is chemically neutralized and sent to the F-Area high-level waste tanks. The major components for this unit operation are a gelatin "strike" tank, a centrifuge feed tank, and a centrifuge.
A.2.3 FIRST CYCLE
First cycle operation, which occurs in the hot canyon, has two functions: (1) to remove fission products and other chemical impurities, and (2) to separate the solution into two product streams (i.e., uranium-238 and plutonium-239) for further processing. This separation process occurs as the product solution passes through a series of equipment consisting of a centrifugal contactor and mixer-settler banks. Before the introduction of the product solution, flows of solvent and acid solution are started through the equipment. When an equilibrium condition is established, the product solution is introduced. The chemical properties of the acid/solvent/product solutions in contact with each other cause the fission products to separate from the uranium and plutonium. Later in the first cycle process, the plutonium is separated from the uranium in a similar manner. The first cycle produces four process streams: plutonium-239 (with some residual fission products), which is sent to the second plutonium cycle; a uranium-238 solution (with some residual fission products), which is sent to the second uranium cycle; a solvent stream, which is sent to the solvent recovery cycle; and an aqueous acid stream, which is directed to the high-level waste tanks. This stream contains most of the fission products. The equipment for this unit operation consists of a centrifugal contactor, mixer-settler banks, decanter tanks, and hold tanks.
A.2.4 SECOND URANIUM CYCLE
The second uranium cycle (in the warm canyon) purifies the uranium solution coming from the first cycle and prepares the uranium for transfer to the A-Line. The purification process is a separation process that occurs in a manner similar to that described for first cycle. The uranium-238 product solution is transferred from the warm canyon to storage tanks in the A-Line facility, which is adjacent to the F-Canyon.
A.2.5 SECOND PLUTONIUM CYCLE
The second plutonium cycle (in the warm canyon) purifies the plutonium solution coming from the first cycle by removing residual fission products, and prepares the plutonium for transfer to FB-Line. The purification process is a separation process that occurs in a manner similar to the first cycle. The impurities are removed in an aqueous stream that goes to the low-activity waste unit operation for processing. The plutonium-239 product solution is transferred to hold tanks for use as FB-Line feed material.
A.2.6 HIGH- AND LOW-ACTIVITY WASTE
These unit operations reduce the volume of the aqueous streams containing fission products. The streams originate with the primary separation process unit operations, such as the first cycle. The fission products are separated and sent to the F-Area high-level waste tanks. The volume reduction process is accomplished using a series of evaporators in the hot and warm canyons.
A.2.7 SOLVENT RECOVERY
The primary purpose of this unit operation is to recover and recycle the solvent that is used in the first cycle. This operation reconditions and removes impurities from the solvent. The purified solvent is returned to the first cycle for reuse and the impurities are transferred to low-activity waste for processing.
A.3 FB-Line
The historic function of FB-Line was to convert plutonium-239 from a dilute nitrate solution stream to a high-purity, stable metal form or "button."
A.3.1 BUILDING DESCRIPTION
The FB-Line Facility is on the top of the F-Canyon structure (see Figure A-1). Its exterior walls and roof are poured reinforced concrete. The portion of the structure that contains process equipment is 39.3 meters (129 feet) long by 20.4 meters (67 feet) wide. The single-story extension to the north is about 10.6 meters (35 feet) wide by 6.1 meters (20 feet) long. The facility is designed such that a 0.3-meter (1-foot)-thick concrete wall provides radiation shielding for personnel working in the FB-Line. Tanks and reaction vessels are enclosed in engineered cabinets or gloveboxes to minimize the spread of contamination and to provide shielding from radiation (see Figure A-6).
A.3.2 FB-LINE PRIMARY PROCESSES
The FB-Line process includes purification and concentration of plutonium-239 by cation exchange, precipitation of plutonium as a trifluoride, conversion by heating in an oxygen atmosphere, and reduction with calcium to form plutonium buttons. The process has five steps: (1) cation exchange, (2) precipitation and filtration, (3) drying and conversion, (4) reduction, and (5) button finishing. Figure A-7 shows the typical process flow through the line.
A.3.2.1 Cation Exchange
The purpose of the cation exchange step is to concentrate the dilute plutonium product solution from the PUREX process second plutonium solvent extraction cycle. This is accomplished by transferring the solution from the storage tanks in the warm canyon to cation exchange feed receipt tanks and then to the cation exchange columns in FB-Line. The plutonium feed is then allowed to flow through the cation exchange column, where resin absorbs higher charge cations (e.g., Pu3+). After the plutonium is deposited on the resin, an acidic solution is used to flush the plutonium from the column. The solution containing the plutonium is filtered and transferred to a product hold tank for sampling and analysis, and then to a concentrate feed tank for subsequent precipitation. The primary cation exchange equipment consists of 14 process tanks; 4 ion-exchange columns (which are shielded to reduce radiation levels); and 4 filters. This equipment is inside engineered gloveboxes at the FB-Line facility.
A.3.2.2 Precipitation and Filtration
In this step of the process, hydrofluoric acid is added to the plutonium solution from the cation exchange process. This action causes plutonium trifluoride to form as a precipitate. The plutonium trifluoride precipitate is filtered out as a cake to remove excess nitrate. The plutonium trifluoride cake is then ready for the drying and conversion step. The 28 vessels associated with the precipitation and filtration process are in engineered gloveboxes in the FB-Line facility. Figure A-6. A glovebox. Figure A-7. FB-Line process Flow.
A.3.2.3 Drying and Conversion
When precipitation is complete, the filter cake of plutonium trifluoride is transferred to the FB-Line gloveboxes for drying and conversion to plutonium tetrafluoride. The cake is air-dried to remove residual moisture and then is placed in a conversion furnace. Residual water and other volatile materials vaporize at a low initial temperature; the vapors are drawn away by the vessel vent system. The temperature in the drying furnace is increased while the cake is blanketed in oxygen. This action converts the plutonium trifluoride to plutonium tetrafluoride powder. Moisture must be sufficiently removed in the air drying and conversion operations to ensure the converted cake is dry enough to be safely mixed with calcium and heated in the reduction pressure chamber.
A.3.2.4 Reduction
The plutonium tetrafluoride powder from the conversion step is placed in a mixing and weighing vessel and weighed. The prepared powder is then mixed with metallic calcium and placed in a prepared reduction vessel, which is 16.5 centimeters (6.5 inches) in diameter and 30.4 centimeters (12 inches) high. The material is heated to about 500-C (932-F), which initiates a chemical reaction that causes the plutonium powder to form molten plutonium metal. The heavier plutonium metal sinks to the bottom of the reduction vessel and forms a "button." After cooling to the ambient temperature, the reduction vessel is opened and the button removed. The reduction process is performed in the FB-Line gloveboxes.
A.3.2.5 Button Finishing
An acid solution rinse removes exterior impurities from the plutonium button. Next the button is rinsed in water to remove the acid. After water rinsing, the plutonium button is air-dried before it is sampled. After being sampled and weighed, it is placed inside a tinned steel can, which is crimp-sealed. The can is removed from the process cabinet in a plastic bag and placed in a second tinned steel can, which is also crimp-sealed. This package is then weighed and monitored for contamination and radiation. A leak test is performed and the canned buttons are placed in a shipping container and transferred to an FB-Line facility storage vault.
A.3.2.6 Bagless Packaging
The FB-Line would be modified for either the Processing to Metal or Processing to Oxide Alternative. To accomplish Processing to Oxide, DOE would install the appropriate chemical adjustment tanks and filters and chemical reduction equipment in the existing FB-Line. In addition, the facility would be modified to install a glovebox(es) that would provide (1) the capability to package the oxide in an inert or dry atmosphere and (2) a system to remove the material containers for storage without the use of plastic bags. To accomplish Processing to Metal, DOE would modify the FB-Line to provide (1) the capability to package the metal in an inert or dry atmosphere and (2) a system to remove the material containers for storage without the use of plastic tags.
A.4 F-Area Outside Facilities
The F-Area Outside Facilities are adjacent to the canyon facilities and provide direct support to building production operations. Process support operations include chemical storage, cold feed preparation, water handling, and acid recovery. The Outside Facilities also provide utilities, including the supply and distribution of water, electric power, and steam (see Figure A-8).
A.4.1 CHEMICAL STORAGE
The chemical storage facilities provide for the receipt, bulk storage, and transfer of fresh liquid chemicals, which are sampled and analyzed before being accepted for storage. The tanks that store nitric acid and aluminum nitrate are stainless steel; others are carbon steel. During receiving operations, personnel obtain samples, verify proper connections and valve lineup, operate transfer pumps, and confirm that the solution enters the correct tank. The building consists of a storage area and a mixing area. The storage area is enclosed; the mixing area has open sides. Access roads surround the building and a railroad spur is on one side. The grounds also include two tank truck stations, a truck dock, a railroad dock, and a small storage area used for hydrazine mononitrate storage. Figure A-8. F-Canyon, showing outside facilities. Stored chemicals are pumped from the storage facilities to points of use in buildings. Smaller quantities are distributed to other parts of the plant through the use of a drum loading and dumpster filling station. Organic solvents and caustics are pumped directly from their respective storage tanks.
A.4.2 WATER HANDLING FACILITIES
The water handling facilities receive and store water that forms from steam condensates that originate in the acid recovery unit reboiler and general-purpose evaporator heaters. Deionized water from the powerhouse is also received and stored for use as process water. The facilities also receive low-activity waste water such as condensate from evaporators in the FA-Line. This water is recycled and used to provide process water and acidified water streams for the canyons via the Effluent Treatment Facility. Some water is discharged to Fourmile Branch after treatment. Tanks in this facility are also used to retain water pending analysis to permit disposal or re-evaporation, if necessary. The cooling water system provides cooling for the hot and warm canyon process vessels. Underground pipes carry water to the F-Canyon, where it is distributed. The water passes through coils inside the vessels (Figure A-3 shows a standard canyon process vessel) and then flows back out of the F-Canyon. Constant monitoring detects radioactivity in the water in the event of a cooling coil leak. If radioactivity is detected, the water is diverted to a treatment facility where the radioactivity is reduced below applicable limits before it is discharged to Fourmile Branch. The primary equipment for water handling consists of hold tanks, skimmer tanks, and heat exchangers. Hold tanks are mounted on concrete saddles in shallow pits (concrete pads) that drain to a sump. Heat exchangers and skimmer tanks are rack-mounted.
A.4.3 ACID RECOVERY UNIT
The Acid Recovery Unit concentrates nitric acid condensates for reuse. The condensate comes from acidic evaporation processes in F-Canyon such as high- and low-activity waste unit operations. Each acid recovery unit is a fractional distillation column that has a straight shell height of 8.2 meters (27 feet) and an outside diameter of 2 meters (6.5 feet). A reboiler is attached to the bottom side of the column. The Acid Recovery Unit Feed Tank receives condensates from the high-activity waste continuous evaporators; the low-activity waste condensate is brought in directly from the continuous evaporator. Canyon sample results or in-line monitors determine if there is radioactivity in the condensate before it reaches the feed tank or distillation column. After recovery, the concentrated acid is pumped to a storage tank for transfer to the canyon as required.
A.4.4 GENERAL-PURPOSE WASTE TANKS
This facility consists of eight storage tanks that have been grouped in two sets of two and one set of four to collect various aqueous wastes. The first set collects solutions from various sumps and catch tanks in the F-Canyon. The second set collects wastes from chemical storage tank areas. The third set collects various wastewater from sumps and pits in the Outside Facilities. The aqueous waste in these tanks is transferred to other areas in the outside facilities for processing (e.g., the general-purpose evaporator).
A.4.5 GENERAL-PURPOSE EVAPORATOR
General-purpose evaporators concentrate aqueous waste (principally from the general-purpose waste tanks) that have radioactivity levels higher than disposal limits, but are low enough to enable evaporation in unshielded equipment. Each stainless-steel evaporator has a straight shell height of 4.8 meters (15.8 feet) and an outside diameter of 1.8 meters (6 feet). The evaporators are operated as flash evaporators with forced bottoms circulation. Evaporator bottoms are concentrated and retained for analysis before discharge to waste tanks.
A.4.6 WASTE HANDLING FACILITIES
The F-Area waste handling facilities are tanks used for the storage and transfer of high- and low-activity wastes, primarily from the F-Area laboratory facilities. Low-level wastes are transferred to the General-Purpose Evaporator for processing. High-level wastes are transferred to the laboratory waste evaporator in F-Canyon. The waste handling vessels and cells are enclosed by a concrete vault, which has a sloped floor and sump to collect leakage and a ventilation system consisting of two air heaters, eight roughing filters, eight high-efficiency particulate air (HEPA) filters, four dampers, and two exhausters.
A.5 New Facilities
A.5.1 F-CANYON VITRIFICATION FACILITY
The F-Canyon Vitrification Facility is partially constructed in
the F-Canyon building. This facility would vitrify actinides
such as plutonium (see Figure A-9). It would provide shielding,
remote handling and viewing capability, process area ventilation,
and removable rack/module type construction to allow the
installation of completely tested process modules. The facility
was originally designed to process californium-252. It consists
of:
- Eight shielded hot cells; six shielded process rack
positions; two shielded analytical [1.5 meters (5 feet) of
concrete/1.5 meters (5 feet) of leaded glass]
- Computer room and cation column stream monitor room
- Column process pump and general instrument room
- Cold feed makeup, storage and delivery tankage
- Rack hot and cold water systems
- Small equipment entry sphincter
- Canyon equipment consisting of feed tank, waste tank, feed
evaporator, and associated jumpers, samplers, etc.
- The hot canyon crane, which will be used as necessary for
solid waste removal, product package removal, and other
necessary work by removal of canyon cell covers over the rack
area.
The facility would be modified to perform vitrification
operations by removing some equipment, such as existing racks,
and installing new equipment modules in two cells. The new
equipment would include solution and glass feed systems, a
melter, an off-gas system, and a glass canister feed and cap
system. In addition, the existing in-cell crane, master-slave
manipulators, transfer equipment, services, and utilities would
be refurbished as necessary.
Figure A-9. F-Canyon Vitrification Facility process flow.
The following process descriptions for the vitrification of
plutonium solutions are based on the use of common vitrification
equipment in the F-Canyon facility. The process would be
accomplished by adjusting or preparing the material for
vitrification and then vitrifying the material.
- Feed Preparation. Plutonium solutions would be adjusted by
concentrating the plutonium to achieve greater processing
efficiency.
- Vitrification. The concentrated plutonium solutions would
be fed to the F-Canyon Vitrification Facility melter where
the solution would be evaporated and denitrated to an oxide.
The oxide would be combined with molten glass. The melt
would flow into stainless-steel canisters where it would
solidify. The cooled canisters would be sealed,
decontaminated, and overpacked for storage.
A.5.2 REPACKAGING AND VAULT FACILITY
The Repackaging and Vault Facility could include the capability to produce an oxide for a variety of nuclear materials, package the materials into primary containment vessels, and store them for an extended period (see Figure A-10). If this new facility were built, its area would be approximately 2,323 square meters (25,000 square feet); its location would be north of Building 235-F and east of Building 247-F. Figure A-10. Repackaging and Vault Facility process flow. The facility site would require approximately 14 acres during construction. The completed facility complex would take approximately 5 acres. An existing facility in F-Area could be modified to accomplish the APF heating and packaging functions. The facility would include the following: - Areas for loading and unloading shipping packages from trucks - Temporary staging and storage areas for packages - Gloveboxes for unloading material from the packages - A furnace to produce oxide when required - A bagless, inert, or dry atmosphere glovebox system for packaging or repackaging materials into primary containment vessels - Nondestructive analysis equipment to measure nuclear material for accountability - A vault area with equipment for remote handling, storage, and retrieval Other process areas in the facility would be for waste collection and handling, equipment maintenance, analytical testing and inspection, shipment preparation, and decontamination of packages or equipment.
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