Workers at the US Hanford Site’s Waste Treatment & Immobilisation Plant (WTP) have launched the second of two 300-tonne melters that has now reached the operating temperature of 2,100 degrees Fahrenheit as part of US Department of Energy (DOE) Office of Environmental Management (EM) Direct-Feed Low-Activity Waste programme. EM said this represents significant progress toward starting plant operations to immobilise in glass millions of gallons of radioactive and chemical waste from large underground tanks.

“Heating up the second melter is an important achievement for our Hanford team and represents another critical step in our journey to safe and efficient tank waste immobilization and disposal,” said Brian Vance, EM Office of River Protection & Richland Operations Office manager. “This success is the culmination of years of effort by our talented workforce, past and present, representing our commitment to advancing our cleanup mission and delivering taxpayer value.”

WTP personnel began heating up the melter in March by turning on 18 temporary startup heaters. The melter temperature was then gradually raised, reaching the operating temperature of 2,100 degrees. WTP personnel will allow the melter to stabilise at this temperature before small glass beads, known as frit, are loaded into the melter to establish a molten pool of glass. Crews will then remove the startup heaters in the top of the melter and replace them with bubblers that circulate air in the molten glass and help maintain an even temperature.

EM Hanford contractor Bechtel National Inc. is commissioning the WTP. "We are immensely proud of the heat-up of Melter 2," said Brian Hartman, Bechtel Senior Vice President and project director for WTP. “This milestone reflects the dedication, expertise and collaborative spirit of our employees, contractors and partner, the Department of Energy. By incorporating the lessons learned from the first melter, we have reached this historic milestone safely and efficiently, underscoring our commitment to excellence and safety."

After running clean glass through the second melter, both melters and facility systems will go through several months of testing using simulated waste. Plant personnel will then run tests on the facility’s exhaust systems that remove contaminants.

When hot commissioning begins in 2025, tank waste treated to remove radioactive caesium and solids will be fed to the melters and mixed with the molten glass. That mixture will be poured into stainless steel containers to cool prior to transporting them the short distance to Hanford’s Integrated Disposal Facility.

For more than 30 years, EM has remained focused on addressing the environmental legacy of nuclear weapons development and nuclear energy research during World War II and Cold War. Hanford is home to 177 underground waste storage tanks: 149 single-shell tanks (SST), and 28 double-shell tanks (DST), ranging from 55,000 to 1.265m gallons in capacity. Those tanks are organised into 18 different groups called farms. Currently, the site's underground tanks store approximately 56m gallons of radioactive and chemical waste. As part of an agreement regulating Hanford cleanup, crews must remove at least 99% of the waste in every tank on the Site, or at least as much waste as can be removed based on available technology. The final stage for the tank farm waste is treatment at the WTP.

Image: Workers at the Hanford Site’s Waste Treatment and Immobilization Plant inspect one of the plant’s large melters during its heatup process (courtesy of DOE-EM)