The Hanford site in Washington State houses ~56 million gallons of radioactive wastes historically stored in 177 underground tanks. The waste must be immobilized for a permanent disposition, and the plan since the 1990s has centered on the separation of the tank wastes into low activity waste (LAW) and high-level waste (HLW) streams. The U.S. Department of Energy (DOE) is building a Waste Treatment and Immobilization Plant (WTP) at Hanford site to separately vitrify these two waste streams in borosilicate glass using Joule-heated ceramic melters (JHCM).
The current strategy is separate the LAW fraction of select liquid supernates from the tank waste taking advantage of the Tank Side Cesium Removal (TSCR) facility. This Direct Feed LAW (DFLAW) process is fast approaching sustained operations.
This presentation will address the variety of vitrification technologies considered by the US DOE, as well as elsewhere treatment of reprocessing wastes are known to be undertaken.
Attention is turning to the treatment of the HLW solids in the tanks. Hanford HLW exists mostly in the form of sludge and salt cake, rich in sodium and aluminum oxides, nitrates and hydroxides along with the significant concentration of transition metal oxides, for example, Fe2O3, Cr2O3, NiO, Cr2O3, and MnO. Although the process of nuclear waste vitrification seems to be well established, in practicality, it is faced with complex problems starting from the design of glass compositions, to processing in melters and long-term performance of the final vitrified waste forms. The presentation is an overview of our current understanding of critical challenges related to the development and performance of HLW glasses. Though more importantly, this presentation reports on the significant advances delivered by the Office of River Protection Enhanced Waste Glass Program over the waste loading, processing efficiencies and flexibility since the WTP Contract was issued in the 1990s.