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Cleaning up legacy waste from the Hanford Site’s plutonium production facility offers design, construction and environmental challenges. It’s the largest construction project underway in the United States. by Clair D. Urbain If you think you have waste problems on your jobsite, then ponder the challenges faced by contractors on decommissioning the Hanford Site’s plutonium production facility. The 586-square-mile Hanford Site near Richland, Washington, is bordered by the fast-flowing Columbia River. Physical challenges include more than 53 million gal. of radioactive and hazardous liquid waste in 177 underground storage tanks, 2,300 tons of spent nuclear fuel, 12 tons of plutonium in various forms, about 25 million cu. ft. of buried or stored solid waste, and about 270 billion gal. of contaminated groundwater. This is spread over 80 square miles on more than 1,700 waste sites and in about 500 contaminated facilities. According to Department of Energy (DOE) reports, the site produced 64 metric tons of weapons-grade plutonium since 1945. The production process left a legacy of radioactive and other hazardous wastes that must be managed for thousands of years. The Hanford Environmental Restoration Project and Waste Treatment Plant construction are the key parts of the process to centralize and stabilize these wastes. The goal is to complete both programs before 2014 and 2011, respectively. Largest
government project Every phase of the cleanup effort is huge, but all are dwarfed by the construction of the plant that will process radioactive liquid waste and mix it with molten glass, which will then be poured into stainless steel vessels that will immobilize the waste and make it easier and safer to handle. “The vitrification plant’s Pretreatment Facility will separate the tank waste into high-level and low-activity waste, then mix it with silica and other components in a melter and turn it into molten glass. The glass will then be poured into stainless steel canisters, sealed, decontaminated and moved into storage,” says Alan Beckman, deputy project manager at the Waste Treatment Plant. This is no small plant. The size of four football fields and 120' tall, the hazardous wastes will be pumped from the tank farms into one of four 375,000-gal. tanks in the Pretreatment Facility. Analysts will identify the ingredients in the waste and separate them with filters, ion-exchange systems, evaporators and other methods. They will also formulate the additives to make the radioactive waste into glass. “About 80 percent of the tank waste is low-activity waste with 20 percent of the total radioactivity and the remaining 20 percent is high-level waste containing 80 percent of the radioactivity,” says Beckman. “We project the low-activity waste vitrification process will produce 1,100 canisters a year and will take almost 12 years to complete. The high-level waste process takes longer and will produce about 240 canisters a year. The High-Level Vitrification Facility will produce almost 8,000 canisters before the project is complete,” he says. The plant sits on 65 acres in the Hanford Site. “That’s not much space when you have the equivalent of two nuclear power plants being built at the same time and up to 2,000 workers on the site,” says Mel Hill, Bechtel National’s procurement manager for MRO and equipment. “There is more than 1 million ft. of piping and 5 million ft. of cable and wiring to be installed. The building will be constructed with more than 250,000 cu. yd. of concrete. The base mat for the various buildings is up to 8' thick. We are self-performing 90 percent of the work, and we have nearly 600 pieces of equipment on the job. “Our biggest challenge is staging and lay-down of supplies and equipment. The best way would be to have a 100-acre yard plus a 200,000 sq. ft. warehouse on the construction site. Instead, we have practically no lay-down space on the site and only a 30,000 sq. ft. warehouse. We have 140 acres of lay-down area off the Hanford site and use a GPS system to locate materials on that property,” he says. The complex system calls for design and construction to continue simultaneously to achieve a start date by 2011. “This is a design-procure-build project. We were able to save one year of construction time by having Chicago Bridge and Iron assemble the four 375,000-gal. pre-treatment tanks on the site, then flying them into the black cells after the 60'-high walls were built. There was only 3' of clearance between the tanks and the walls of the black cells, so the crane operator had to move the tanks only by instructions radioed from riggers. We had to use a $3 million, 600-ton crane to do it, but when you consider we spend $500,000 a day on this site, the crane cost was well worth it,” says Britton. It’s been decades since a nuclear-grade project has been built in the United States and finding nuclear-class workers and suppliers is difficult. “We must help workers and vendors develop these skills. We work with the building trades and other resources, like the local community college, to get people with these skills. We are also working with suppliers, helping them improve their quality assurance programs so they can provide us with nuclear-class quality materials,” says Britton. Cocooning
reactors takes innovation “The goal of the cocooning process is to reduce the footprint of the reactor by 80 percent. It involves demolishing the reactor buildings down to the 4'-thick shield walls that surround the highly radioactive reactor cores. All remaining openings are sealed with concrete or steel plate and a new roof is built over the remaining facility,” he says. The demolition work is labor-intensive. “Workers remove the walls block by block and put them into a skiff box that gets moved by a crane to the ground. The crane also lifts off roof portions and places them on the ground for disassembly. “We use a 150-ton Manitowoc 4000 crane with a 200' boom and 30' jib. This configuration allows us to reach the middle of the building,” Schilperoort says. Concrete portions are demolished with a hammer mounted on an excavator. A small utility room is built around the double doors that lead to the reactor core. “This houses the electrical panels and monitoring equipment. We weld the doors into the reactor shut, and once every five years, they are opened so the facility can be checked for any problems. We recently opened the C reactor, which was the first unit to be cocooned, and the area was just as it had been left,” he says. Schilperoort has been involved with cocooning three of the four reactors already completed. Lessons learned on the first reactor have streamlined the process. “We like to say we now can cocoon four reactors for the price of three,” says Schilperoort. Search
for technology “The program was designed to identify technologies that help us improve the baseline of the project from a cost, safety or scheduling perspective. We developed a needs statement, then looked for solutions. We first look for off-the-shelf solutions, but some were also engineered. The DOE wanted us to implement technologies that had wider applications, but we found that isn’t always possible,” he says. The program that formalized this process has been discontinued by the DOE, but Bechtel Hanford continues it as a best business practice. It also pegs a life-cycle cost savings from many of the technology deployments. “We have already achieved a life-cycle cost savings of $137 million,” says Koegler. Here is a short review of some of the problems and solutions their technology teams have developed: Oxy-gasoline cutting torch. Uses gasoline instead of acetylene as fuel and offers lower cost, higher temperatures and faster cutting of metal thicker than 1". From Petrogen Inc., the unit reduces airborne contamination and increases worker safety. It is readily available and less costly to use than an oxyacetylene torch. Body core temperature monitor. Workers in highly contaminated areas must wear several layers of protective clothing. Site temperatures can top 100 F and although workers wear cooling vests, it was not clear how long workers could remain in the suits before heat affected them. The Body Core Temperature system uses a pill-sized Cor-Temp monitor that the worker swallows. A palm-sized monitor tracks internal body temperature. This data can be downloaded for analysis. Data from the study indicated that workers could work up to one hour longer than originally allowed. This ensured personnel safety, reduced cost and improved scheduling by optimizing safe work times. Estimated lifetime cost savings/avoidance: $1.4 million Affixing contaminants. Dismantling tanks with radioactive sediment have a high risk that contaminants will become airborne. To affix the contaminants, Rust Doctor, a water-based latex paint, is applied inside the tank. The paint converts iron oxide into black magnetite, which captures and fixes the radioactive contamination to the tank walls for safer dismantling. Estimated life-cycle cost savings/avoidance: $1.254 million. Fogging system to settle demolition dust. While the Rust Doctor paint affixes contamination inside the tank, demolition could cause airborne contamination that could reach the Columbia River, which was only 200' away. To reduce airborne particles, a Mini-Pro fogging system that uses a 5 hp. Briggs engine, a 100 cfm Roots blower and a Fluid Metering Inc. pumping system sprays a glycerine coating that settles out airborne particles in the controlled area. The Mini-Pro fogging system can be positioned up to 50' away from the work area. Dust control on service roads. Some roads on the sites are unpaved and dusty. While watering roads helps control most dust, some areas require greater dust suppression. In these areas, crews apply Dust Bond, a cohesive resin, diluted with water. When sprayed on roadways, it penetrates the surface and attaches to fine dust particles. It offers less labor because less watering is needed and reduces road maintenance because it stabilizes roadways. It won’t get picked up by tires or shoes, is non-corrosive and will not leach or wash from the soil. Estimated life-cycle cost savings/avoidance: $51,000. Motorized cart simplifies lifting. Heavy, bulky items must be moved by hand in the decommissioning and demolition process. It sets workers up for back strains and other injuries. The Ultra Lift is a powered two-wheeled handcart that allows users to move heavy objects easily. It can traverse steps and can handle loads up to 1,500 lbs. and 36" high. Estimated life-cycle cost savings/avoidance: $61,000. Remediating
burial sites “There are not good records of where things are buried. Burial grounds and waste sites range in size from a few sqaure feet to the size of a football field. They contain everything from demolition debris, reactor parts, tubes of mercury used in tritium processing to gun barrels used in plutonium production. It’s a real junkyard,” says Rex Miller, task leader at the 100 B/C area burial ground remediation project. “Many parts are highly radioactive and could cause high-dose exposure.” Excavator operators digging up the burial grounds wear Level B protective equipment with supplied-air respirators. Sensors on excavator buckets monitor radioactivity and operators sort the excavated material by its level of radioactivity. When the excavator is not in use, the potentially contaminated bucket is cordoned off and posted with radiation hazard signs. The excavator operator cascades the soil onto piles of like materials. Suited workers sort out any metal or other parts with long-handled rakes or staffs. “In the burial grounds, we dig until we find native soil,” Miller says. “We have twice as much radioactively contaminated materials as we were expecting to find in some of the burial sites.” Once all contaminated material is removed on a portion of the site, the area is sampled remotely for radioactivity. “We file reports with the DOE. Once they confirm our findings, we can fill in the excavated areas,” Miller says. The radioactive material is placed in special containers that move it from the site to a transfer station. The containers are decontaminated and over-the-road trucks take them to the ERDF for disposal. The ERDF is made of up of four cells. Cells 1 and 2 are already filled and Cells 3 and 4 are nearly filled. Construction is nearly complete on Cells 5 and 6. The ERDF is designed to be expanded as needed, and the site could accommodate as many as 30 cells. Once the ERDF is no longer needed, a permanent cover will be designed and placed over the whole disposal site. Editor’s note: Find out more at www.waste2glass.com or www.hanford.gov. Published in the November/December 2004 issue of Contractor Tools and Supplies magazine. |
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