CH2M HILL Technology for Waste Treatment
Bulk Vitrification
Through a series of scaled tests, we are evaluating Bulk Vitrification as a supplemental technology for treating Hanford’s low-activity tank waste. Bulk Vitrification is primarily attractive because of its potential to expedite treatment of Hanford tank waste. Additionally, it offers minimized worker exposure; efficient handling for long-term, on-site disposal using 20% less space; and support for mission safety objectives.
As originally planned and designed, the Waste Treatment Plant alone will not be able to meet the TPA schedule requirements. However, if testing confirms the technology’s feasibility and it is approved by the Washington State Department of Ecology and the U.S. Environmental Protection Agency, DOE will proceed with design and construction of a Bulk Vitrification facility. The Supplemental Treatment Plant will have the capacity to immobilize the balance of waste not immobilized in the Waste Treatment Plant, thus providing needed additional capacity to meet TPA requirements.
With Bulk Vitrification, a mixture of waste and soil is placed in a container resembling a shipping container. Electrodes inserted into the waste/soil mixture deliver an electrical current that melts the mixture into a durable glass brick. When cooled, the container and its contents are placed in an onsite, permitted disposal facility.
Testing of the Bulk Vitrification technology is well under way and construction has started on a pilot plant where full-scale process tests will use up to 200,000 gallons of actual tank waste. We are working closely with DOE and Ecology to ensure operations comply with regulations and include rigid controls and procedures for protecting workers and the environment. In full operation, Bulk Vitrification has the potential to immobilize approximately 25 million gallons of Hanford’s low-activity radioactive waste for permanent disposal.
Fractional Crystallization
A simple and proven industrial process may be able to assist in pretreatment of Hanford tank waste. CH2M HILL is exploring the use of fractional crystallization as a pretreatment technology to separate high-activity and low-activity waste for more efficient waste retrieval and processing. The science is well understood and the process has an established track record in industries including salt and sugar refining, pharmaceutical production, and potash mining.
Applied to Hanford’s tank waste, the process would dissolve solid tank waste in water and then, through filtration and evaporation, separate the waste into low-activity and high-activity waste streams. Highly radioactive isotopes such as cesium and technetium (i.e., the high-activity waste) would be maintained in the liquid portion, which could be pumped out and transferred to the double-shell tanks for eventual glassification in the Waste Treatment Plant. The remaining low-activity waste, in the form of salt crystals and sludge, could be further dissolved and retrieved for processing to immobilize the waste.
A successful pretreatment process, such as fractional crystallization, could help the site increase its capacity for waste treatment and thus accelerate cleanup. Although the Waste Treatment Plant was designed to handle all types of Hanford tank waste, the plant will not have the capacity to process the entire volume of waste by the TPA milestone in 2028. As much as 90% of the low-activity waste from fractional crystallization could be eligible for processing through Bulk Vitrification or another immobilization technology. CH2M HILL has been testing the process on both simulated waste and actual tank waste. Construction of a pilot plant will provide scaled-up testing to determine the feasibility of using fractional crystallization for Hanford applications.