Monte D. Crippen, P.E. and James A. Demiter
SGN Eurisys Services Corp.

Several non-radioactive sodium test loops were built at Hanford during the 1960s and 1970s to test components and system design and function for use in the Fast Flux Test Facility (FFTF). The deactivated systems have been in a lay-up condition since 1977. The collective published volume contained in the six Nuclear Energy Legacy loops and storage tanks was approximately 182,000 liters (48,000 gallons) of sodium. With the systems and loops no longer serving a useful purpose, the U.S. Department of Energy (DOE) elected to drain and dismantle the remaining six non-radioactive alkali metal test loops.

Three test loops and their storage tanks were drained and dismantled between May 1995 and October 1996: the Small Heat Transfer Loop (SHTL), the Prototype Applications Loop (PAL), and the Thermal Transient Loop (TTL). In addition, sodium tanks drained between May 1996 and August 1997 were the 1720-DR and the 3718-M tank of the High Temperature Sodium Facility (HTSF). The facilities housing the TTL and the 1720-DR tanks were also demolished and removed. Two tanks (containing approximately 750 liters [200 gallons] of sodium) need only be removed and shipped across the Hanford Site for reheating and draining.

The entire program to reactivate, drain, and demolish the six alkali metal systems/facilities was scheduled for seven years at a cost of $14.3 million ($5.1 million were construction craft costs). The work was conducted in three Hanford areas located 35 miles apart: the 100 Area, 200 Area, and 300 Area (the core work area). In 2.4 years, all of the systems were drained (except the two small tanks) and demolished, except one, at a cost of $2.8 million. In total, 186,000 liters (49,200 gallons) of sodium were drained from the loops and tanks (103% of the published inventory) and sold.

Newly installed stainless steel tubing was used to transfer the alkali metal product to shipping containers.

The sodium product was drained into U.S. Department of Transportation (DOT) approved containers ranging from 200 liter (55-gallon) drums to 76,000 liters (20,000-gallon) rail tankers. A small sodium-potassium (NaK) system was also drained into an approved DOT shipping containers. While the transfer was sometimes slow, this approach minimized costs, simplified physical operations and disposal issues, and allowed for completing each tank drain ahead of schedule. Hazardous wastes generated during the draining and demolition were packaged to applicable U. S. Environmental Protection Agency (EPA) standards.

The program activities were successfully conducted to design or reactivate, and modify inactive alkali metal systems for draining, dismantle drained systems, empty sodium tanks, clean tanks using a water vapor nitrogen system, recycle the nonradioactive sodium for commercial uses, dispose of the removed equipment and piping, and release 12,000 feet ² of building space and 30,000 feet ² of land to other uses.

Sodium and some sodium-potassium eutectic alloy, commonly known as NaK, originally procured in support of the Liquid Metal Fast Breeder Reactor (LMFBR) program, were contained in safe configurations within dormant test loops and storage tanks. The alkali metals and test loops were no longer needed. Decommission of the loops and their associated hardware included consideration for reuse/recycle, as well as for disposal of bulk alkali metal materials. The decommissioning process was consistent with the DOE commitment to minimize waste and comply with applicable federal and State of Washington regulations. Actual field work began in May 1995 with the removal of two small sodium loops in the 300 Area. Larger test facilities in the 300 and 100 Areas were dismantled, and the large storage tanks were drained of sodium.

The Nuclear Energy (N.E.) Legacy Sodium Disposition program was started in 1993. The goal of the program was to remove the nonradioactive sodium from the retired test facilities on the Hanford Site, transfer the sodium to commercial users, and properly dispose of the sodium systems and associated equipment. In June 1993, DOE directed the contractor to enter the bulk N. E. Legacy sodium into the Federal Facilities Excess Process. This process advertises the sodium to onsite and offsite government agencies. If a favorable response is received, the sodium would be transferred to the interested agency. Should no favorable response be received, the recycle group initiates sale of the sodium in the private sector. When response to this sale is positive, the sodium is sold. Three bids were received for this sodium inventory, with shipments to extend over a multi-year period.

Constructed in 1968 for support to the LMFBR Program, the 335 and 335A buildings housed the SHTL,

TTL, and the PAL sodium test loops used to study the behavior of sodium heat transport systems and mechanical components of the type to be operated in a sodium environment. These loops were shut down in 1977 and the sodium was either transferred to a loop storage tank or allowed to freeze within the loop piping.

The large sodium tanks were housed in the 1720-DR and 3718-M buildings. The 23,000 liters (6,000 gallon) 1720-DR sodium tank was received in 1971 from the Fermi Reactor Site. It contained 14,800 liters (3,900 gallons) of sodium and was anticipated for use in sodium aerosol burn tests. However, the tests were never conducted and the sodium remained stored in the deactivated facility. The 190,000 liters (50,000-gallon) 3718-M tank was the sodium storage tank for the High Temperature Sodium Facility (HTSF) and the Composite Reactor Components Test Activity (CRCTA). The CRCTA is a one-third size sector of the FFTF reactor that allowed full-size reactor vessel components to be tested in actual reactor conditions. In addition to supporting the development of the LMFBR programs and engineering studies, the HTSF facility was used to train FFTF operators prior to the FFTF becoming operational. The 3718-M tank contained approximately 169,000 liters (44,500 gallons) of sodium.

The SHTL and PAL contained approximately 570 liters (150 gallons) of sodium. The SHTL had a 340 liter (90-gallon) storage tank containing approximately 170 liters (45 gallons) of sodium. The PAL was not designed to be drained, therefore, approximately 50 liters (13 gallons) of sodium were frozen in the piping following shutdown of the system. The TTL contained approximately 2,300 liters (600 gallons) of sodium. The PAL vessel contained approximately 350 liters (90 gallons) of sodium. There were approximately 7.5 liters (2 gallons) of NaK contained in the cooling system for the PAL cold trap.

A major component in the safe disposition of N. E. Legacy facilities is to ensure compliance with applicable environmental regulations. Some of these regulations are the National Environmental Policy Act of 1969, the National Historic Preservation Act of 1966, and the State of Washington Department of Ecology, Washington Administrative Code (WAC) 173-303, "Dangerous Waste Regulations."

An early step in the sodium loop dismantling process for each of the N. E. Legacy sodium loops was to strip regulated asbestos-containing material (RACM) from the piping exterior. Since the sodium inside the piping would react violently if exposed to water, the removal of RACM from SHTL and PAL required the use of dry methods. In accordance with the asbestos portion of the National Emission Standards for Hazardous Air Pollutants, written approval is required to waive the requirement for wetting the RACM during renovation. It was decided to apply for this waiver on the basis that the dry removal would be performed inside a negative pressure enclosure. A portable collection and exhaust ventilation system was designed to capture particulate asbestos material produced by the stripping and removal operations.

Although RACM was removed from the loops prior to their transport offsite, bonded asbestos components (i.e., gaskets and manufactured products containing asbestos) were left in place in accordance with applicable DOT regulations. These regulations state, "Asbestos which is immersed or fixed in a natural or artificial binder material (such as cement, plastic, asphalt, resins, or mineral ore), and manufactured products containing asbestos are not subject to the requirements of this regulation."

During initial planning to demolish and ship SHTL components to a buyer, engineers identified that a substantial cost saving could be realized by shipping large sections of the loop piping and components intact within their structural framework, rather than dismantling the components separately. Both dismantling costs by construction forces and hazardous disposal costs would be saved. A DOT exemption was applied for and granted. The DOT Exemption authorized "the transportation in commerce of residual sodium metal contained in the piping of a test assembly, overpacked in a reinforced plywood box." The SHTL was separated into two enclosures, each free standing within its angle-iron framework, and overpacked into two reinforced plywood boxes per DOT requirements. The piping systems were filled with dry inert gas, and the ends of the piping sealed to preclude contact of sodium metal with moisture in the environment.

The baseline strategy for overall removal of the N. E. Legacy test loops was to package the alkali metals and associated loop hardware for shipment offsite as product, when possible. The loop materials not qualified for product were recycled internally for reuse, or disposed as salvage, scrap, or waste. Residual sodium-wetted (or sodium-filled) piping and associated equipment were included in the above groups, as appropriate. Ancillary tankage was cleaned in situ for residual sodium removal to the practicable extent, to facilitate potential reuse or disposal. The removal of these hazardous materials and test loops was anticipated to allow the associated facilities to be transferred to alternative sponsors for new uses.

Necessary portions of each loop were heated to bring the metallic sodium to a molten state (melting point 98 C, 208 F) to allow for draining and recovery. Existing heat trace systems and monitoring equipment was used where possible. Additional hardware (e.g., drain lines, power supplies, and instrumentation) were provided when necessary to support draining of the sodium into suitable containers. The larger tanks, 1720-DR and 3718-M, were drained into rail cars supplied by the buyers, while smaller tanks of the SHTL, PAL, and TTL were drained into DOT-approved containers for eventual transfer to the buyer.

Alkali metal-wetted test loop piping and components containing residual alkali metal not being sent off site as product were shipped to a privately operated Resource Conservation and Recovery Act treatment, storage, and disposal facility (TSD) under contract to Hanford.

Tanks and certain other large components were cleaned in situ by the technique of flowing a water vapor nitrogen mixture through the tanks. A portable cleaning station employing the water vapor nitrogen process was built and used for this purpose starting in 1996. The sodium residuals were slowly reacted with moist inert gas, resulting in a sodium hydroxide solution and hydrogen gas. The process was monitored until no further chemical reaction was detected. The equipment was flushed with water and air-dried. The caustic rinse solutions were shipped to an onsite facility for use in its water filtration system. The cleaned tanks were removed to storage for recycle or transfer to an appropriate facility on the Hanford Site.

Work to remove the SHTL, PAL, and TTL from Buildings 335 and 335A began on schedule in

May 1995. Careful attention was given to all phases of the dismantling operations where momentary exposure of frozen sodium to the atmosphere was necessary.

The SHTL was dismantled, removed from the 300 Area, and sodium drained from the system tank from May 1995 to December 1995. The tank was cleaned of residual sodium using the water vapor nitrogen cleaning station in March 1996.

The first operation performed in support of loop dismantling was to create a zero energy condition at the SHTL, including its ancillary equipment. This task consisted of isolating the loop from electrical power, argon supply, instrument air supply, and assuring that no other pressure-producing lines were piped into the SHTL.

Portions of the SHTL insulation and wiring that contained asbestos were removed prior to shipment offsite. This operation was performed by a specially trained crew using a large vacuum system coupled to a water spray and bagging device, enclosed in a plastic greenhouse. Installation of the equipment, insulation removal, post-removal cleanup and stabilization, and tear-down of the greenhouse required only two weeks. The operation was performed in June 1995.

Following insulation removal, the piping and structures were sectioned to divide the overall loop into three free-standing piping enclosures. One enclosure held only a few components (none containing sodium) and, following its disassembly, was sent to salvage. In the remaining two enclosures

the cold trap, vapor traps, and drain tank were separated from the piping systems and moved to storage. The piping in each enclosure was filled with inert gas and sealed with compression fittings. The electromagnetic pump and flowmeter were separated from the piping systems and resealed. After stripping the outer materials from the pump and flowmeter, the materials were excessed and the central pipe was treated the same as other sodium-wetted piping. Excessed components with no scrap value were dispositioned for appropriate land burial at the Hanford Site.

Each of the two remaining piping enclosures containing sodium-wetted materials were placed inside of large plywood boxes, in accordance with conditions of the DOT exemption authorization to transport sodium-containing materials, and shipped offsite to the buyer in September 1995.

Draining of sodium from the SHTL Dump Tank was scheduled for completion in 1998. However, due to favorable work progress, the operation was performed during December 1995. In order to facilitate the drain operation, the tank was first removed from the SHTL enclosure. A dip tube was installed inside the tank, as was and new transfer tubing, along with heaters and insulation. Using the original trace heating, which was not damaged during tank removal, the tank contents were heated and the sodium [approximately 170 liters (45 gallons)] was transferred by inert gas pressure into two new DOT 200 liter (55-gallon) drums for sale.

Dismantling of the PAL and its removal was completed December 1995. The PAL differed from the SHTL in that the loop piping was largely below the elevation of sodium in the process tank, and was sodium-filled rather than sodium-wetted. In addition, PAL contained a small NaK loop used for cold trap cooling that was estimated to contain approximately 7 liters (15 gallons) of NaK.

The first operation performed in dismantling the PAL was to create a safe energy work environment as was done prior to SHTL removal, except that electrical connections for heating the PAL tank were only disconnected rather than permanently removed. Work on dismantling and removal of non-sodium containing components began in June 1995. These components included three control and instrument panels, process ducting and blowers, and the chromatograph system, including several other control systems. The electrical and control circuits not required for vessel sodium melt-out or NaK drain were removed.

Following removal of PAL non-sodium components, the dismantling operation was suspended to drain the main loop tank. Electrical energy was restored for heating and control functions. Approximately

350 liters (90 gallons) of sodium in the tank were heated to a molten state between 120 - 150EC

(250 - 300EF), and transferred by inert gas pressure through a dip tube and piping system (similar to the approach used for SHTL) into new 200 liter (55-gallon) drums. The sodium transfer was completed in November 1995.

Prior to beginning the operation to drain NaK from the PAL cold trap cooling system, vapor-phase samples were taken to ensure that a gas blanket failure had not occurred during the long lay-up period (since 1977). Sample analyses confirmed that air in-leakage had not taken place, therefore, superoxide was not present in the system.

A fitting was welded to the NaK system low point. Liquid nitrogen was used to freeze the NaK, and a drill used to penetrate the jacket wall within the fitting. Valves were then quickly attached. The NaK was allowed to thaw and was subsequently drained from the surge tank, cold trap jacket, air cooler coil, and associated lines, into a DOT container.

Following the sodium and NaK tank drain operations, prior to performing alkali metal pipe cutting, the complete PAL facility was be electrically isolated. The electrical and control systems were dismantled. Heater elements and wiring, as well as thermal insulation were stripped from the piping and disposed as salvage or scrap.

Piping was cut into pieces suitable for shipment to and disposal by the TSD facility. The disposition of other materials was determined on an item-by-item basis. The disposition alternatives included direct recycle, cleaning for recycle/ salvage/scrap, direct disposal by the TSD, disassembly or section-by-section cutting for disposal by the TSD, long-term storage, or land burial on the Hanford Site.

The final phase of PAL demolition began with dismantling the loop control panel and the three peripheral test modules. Sodium-wetted/ filled piping in each enclosure was removed by cutting the pipe and capping ends, moving the pipe segments to the pipe lay-down area for further size reduction. The remaining module structures were dismantled and the components disposed of or recycled. In 1997, the empty PAL tank was cleaned using the water vapor nitrogen process.

The drained NaK system was removed from the PAL main loop for ease of disassembly. The NaK piping was reduced in length by cutting and capping ends, then shipped to the TSD. NaK-wetted components of larger diameter than accepted by the TSD are being held in storage pending future disposal. Loaded 200 liter (55-gallon) drums were moved to the Satellite Accumulation Area. Drums containing sodium waste were moved to the 90-day storage room for controlled storage en route to disposal.

The TTL was a considerably larger and more complex loop than either SHTL or PAL. The facility and support sodium systems are shown in Figure 1 before demolition and removal. Figure 2 shows the area after removal of all TTL sodium systems and facilities. The system was not contained in an enclosure as the other loops. The TTL spanned three facilities and consisted of a sodium flow and valve test loop in one facility and the main tank, pump, flowmeters, and electrical power systems in the other. A third facility held system instrumentation and controls. Support equipment for the TTL consisted of heat exchangers, large inert gas tanks, sodium reactor plenum, 30-foot heater, blower/cooler equipment, and associated piping among all support systems. These support systems were located outside the TTL facilities. Since the TTL contained larger and heavier systems, their removal required the use of cranes and heavy-duty equipment.

The TTL was dismantled from October 1995 to October 1996. After zero energy checks, the sodium piping and other equipment were removed. The original tank heating system was used to recover 2,300 liters (600 gallons) of sodium for sale.

After the sodium tank and metal pit liner were removed, the concrete pit (12 feet deep) bottom was drilled to allow for water drainage and backfilled with gravel. Eventually, all the 335A building was removed including the concrete floors and foundation. The area was covered with gravel and graded.

During the TTL tank draining operation, a non-sodium rated valve failed, resulting in a small sodium spill (less than five pounds) to the containment pit area. There was no release to the environment, no personnel injuries, and no equipment damage. An assessment was conducted that evaluated the safety of the drain. Drain line valves were replaced with new sodium valves, a larger vent line was installed, and the tank drain continued successfully.

During demolition of Building 335A, a jackhammer mounted on the front of the backhoe destroyed a live, 440-volt feed conduit to an adjacent building, despite a detailed drawing review, cable route marking, and Non-destructive Examination ground surveys. Because of careful work practices, there were no injuries or equipment damage, except to the cable itself. An accident evaluation pointed to the poor site drawings and indicated all pre-work activities that could have been done were conducted correctly.

Two large sodium tanks were reactivated, re-instrumented, and drained as part of the N. E. Legacy program. The 1720-DR tank contained 14,800 liters (3,900 gallons) of sodium and the 3718-M tank of the HTSF system contained liters 169,000 liters (44,500 gallons). The sodium inventories of both tanks were drained into three 76,000 liters (20,000 gallon )rail tankers and sold.

The 1720-DR tank was located in a building 35 miles distance from the core work area (the 300 Area). A cost and work structure assessment was conducted in September 1995 to evaluate the options of reactivating and draining the 1720-DR tank. The options were to reactivate and drain the tank in place or move the tank the 35 miles to the 300 Area. Several reasons existed to support moving the tank, which included improved construction crafts support, lower cost, the capability to conduct work in parallel, and an improved schedule for completing the drain.

The 1720-DR tank was moved October 1996 along with its 8,000-gallon metal catch-pan to the

300 Area. The building was demolished and sold for scrap. The concrete pit liner was filled with gravel and the site was leveled to grade.

The tank was repositioned in its catch pan 15 feet from an active rail spur line (Figure 3). A temporary weather enclosure was placed around the tank to support work during weather months. New heaters, wire runs, controls, and instrumentation were installed prior to testing the system. The tank was heated to 150E C, and a one-inch dip tube (drain line) was then inserted to the tank bottom and connected to the rail tanker. To drain the sodium, the rail tanker was put under full vacuum and the tank was pressurized with nitrogen to about five pounds. The tank was drained to the rail tanker in 13 hours in March 1997. After the drain was complete, the instrumentation and control panel were removed and reused for the 3718-M tank drain. The drained 1720-DR tank was removed from the catch pan and cleaned of its remaining sodium (approximately 57 liters [15 gallons]) using the water vapor nitrogen system. The catch pan was cut up and sold for scrap value.

Following the drain of the 1720-DR tank, the rail tanker was moved across the street into the High Bay facility (337 Building) to receive the drained sodium from the 3718-M tank. The reused instrumentation and control panel were positioned near the tanker (Figure 4) to control the new transfer line heaters and electrical and gas valves at the tanker. A new sodium transfer line was welded into the existing system four-inch sodium line and run approximately 100 feet to the rail tanker. The transfer line was insulated with one-inch of KaowoolÒ insulation. The other facility sodium systems were isolated from the tank drain line. The tank heaters, main four-inch line heaters, and tank systems were controlled from the main control panel in the facility basement. The inactive facility systems and instrumentation were reactivated and tested for the drain. Many unforseen activities were conducted to bring the inactive system to life following 20 years of dormancy.

The system was readied for drain in June 1997 and it was decided to commence the drain activities even though only two of the needed three rail tankers had been received from the buyer. The drain was conducted like the 1720-DR tank drain with the rail tanker under full vacuum and the tank pressurized with nitrogen to 10 pounds. After initial tank heat-up, the one-inch stainless dip tube was inserted to the tank bottom, connected to the drain line, and the sodium drain began in July 1997. The first two rail tankers were filled in July and the third by early August.

The cycle for each rail tanker was approximately one week. The tanker was spotted in the facility; sodium transfer, vacuum, and nitrogen lines were connected; the tanker was tested for vacuum and pressure tightness; filled; disconnected; and removed from the facility. The cycle was then repeated two other times.

After successful drain of the sodium from the 3718-M tank, all systems in the facility were returned to the pre-drain condition. The instrument and control panel were disconnected; the sodium drain line removed, cut up, and drummed as waste; and the empty 3718-M tank was returned to the passive nitrogen pressure condition. Approximately 100 gallons of sodium remain in the tank that may be cleaned from the tank by the WVN technique.

All materials recovered from, and produced by, the removal of SHTL, PAL, TTL, 1720-DR, and 3718-M tanks classified either as product, recycle, salvage, scrap, or waste. The sodium and NaK contained within the systems were managed as product for shipment offsite to a buyer. Sodium recovered from the loops was not degraded by its use in the test programs, and was sold with other nonradioactive sodium inventory from the N. E. Legacy program. Alkali metal contaminated piping and other loop components were treated as hazardous waste and loaded into DOT-approved containers, and shipped to the TSD for disposal.

Materials removed from the loops containing neither sodium, NaK, or other hazardous materials were dispositioned in accordance with their probable monetary impact. Materials, such as structural components, were recycled at Hanford as salvage/scrap. Tanks that were cleaned by the water vapor nitrogen process will be recycled locally as salvage/scrap.

Asbestos - Because the SHTL insulation contained a large percentage of asbestos, and piping was packed closely together within cramped working spaces, it was decided to treat all insulation as regulated asbestos containing material. A mechanical vacuum device operating together with a large plastic structure (greenhouse) was used for the removal. In June 1995, the particulate filtration and exhaust ventilation system collected asbestos materials produced by the stripping of insulation from the loop. Insulation and wiring that contained asbestos were sent to an asbestos landfill for permanent burial or conversion to a nonhazardous material. PAL asbestos insulation removal was different in that working space was conducive to hands-on removal using local bagging of the piping. Therefore, a large greenhouse was neither necessary nor practical.

Lead - In all loops, lead was present in the paint on the exterior of some enclosures or structures. Non-dusting tools were used in this work, where practicable. Also, the practice of taping the work area to suppress airborne contamination was commonly followed. Since the lead-painted enclosures would be sold to a company for containment, they were not considered waste and therefore not regulated under DOT.

Mercury - Many of the old electrical control switches in the loops contained mercury. It was thought extensive work by special hazardous materials workers would be needed to remove the switches prior to shipping the removed system enclosures to a buyer. But it was discovered that DOT had no regulations controlling the shipment of the mercury unless each switch contained more than 15 grams of mercury. Since the switches did not contain 15 grams, the switches were left in place and sold as part of the system.

A seven-year program, costed at $14.3 million (including $5.1 million for construction crafts), was outlined to reactivate, redesign, drain, and demolish the six non-radioactive N.E. Legacy alkali metal systems located in six buildings (35 miles apart) at the Hanford Site. In 2.4 years all sodium systems were drained, except one small system containing approximately 760 liters (200 gallons) in two tanks, and all systems except one were demolished (the extent to which it will be demolished is now in question) for $2.8 million. Each sodium system drain and demolition activity was completed from one to four years ahead of schedule and all substantially under budget.

BACK