Improving the Recovery Process by Defining Simulant Composition for Hazardous Waste

The United States Department of Energy’s Hanford Site in Washington state was built in 1943 to house the nuclear reactors used to produce plutonium for atomic weapons (1944 to 1987). When the nuclear reactors were shut down, the irradiated fuel rods were removed to processing facilities at Hanford so they could be dissolved and the plutonium retrieved. Dissolving the metal of the fuel rods required powerful chemicals that became radioactive and extremely hazardous afterwards and could not be reused. They needed to be contained.

Tank Farms

To hold these hazardous chemicals, the USDOE built a series of massive underground storage tanks ranging in capacity from 55,000 to more than a million gallons. Between 1943 and 1986 a total of 177 tanks were built on these “tank farms.” In recent years, no new waste has been added, but some of the waste originally put in them is still there. This waste consisted of liquids, gases, semi-solids and solids. Over the years, most of the liquid in the earlier-built, single shell tanks was pumped out to more secure double-shell tanks, leaving waste which resembled peanut butter, small broken icebergs, foam, whitish crystals, or semi-solid and solid sludge called saltcakes. None of these wastes is easily removed.

The Challenge

Today, 56 million tons of solid waste must be removed from these tanks and remediated. Crews must remove at least 99% of the material in every tank or as much waste as can be removed based on available technology. If new technology becomes available, more waste can be removed, lowering costs and speeding up the vitrification process.

The vitrification operation cannot process the waste unless the formula defining the composition of waste and glass forming materials is known and consistent. Because the composition and even the consistency of the tank waste is often unknown, the challenge was to design and develop the technology for a mixing process that would deliver the waste from the tanks in batches with consistent composition. By developing a “recipe” to produce a vitrified waste product that meets accepted regulatory requirements, the waste could be processed more speedily and at lower cost.

Energy Solutions, an international company responsible for safe recycling, processing and disposal of nuclear materials, designed the smaller scale simulated tanks in which to safely mix benign materials simulating the size and density distributions of the hazardous materials. To analyze the samples, they needed a laboratory that was located nearby and would produce accurate results on quick turnaround all the while being flexible to an increasingly demanding schedule. Based on previous positive experience, Energy Solutions retained RJ Lee Group to analyze the mix of components extracted from the tanks, from the first to last extraction, so that when they transported the waste to the plant, they were secure in knowing the content of the mixture and how it would react during the process.

Once we completed development of the requested analytical procedure, we transferred the technology to our NQA1-certified Center of Laboratory Sciences (CLS) in Pasco, WA. Such a local presence allowed us to provide the quick turnaround and flexibility that was a major requirement of the client in this significant undertaking. The fact that Energy Solutions had previous working experience with RJ Lee Group satisfied them that the crucial requirements of the current project could be met. By assisting in the development of simulants that matched the composition and consistency of hazardous waste, we were able to help our client satisfy DOE requests to process more waste in a shorter time period on a more economic basis.