Removal of 90Sr and 241Am from concentrated Hanford chelate-bearing waste by precipitation with strontium nitrate and sodium permanganate

The Hanford Nuclear Site, near Richland, Washington, is developing a method to simultaneously remove chelated 90Sr and 241Am from the liquid phase of high-level nuclear waste using sodium permanganate and cold strontium nitrate. This method has been reported previously for treating diluted waste in the Hanford Waste Treatment and Immobilization facility (WTP) that is currently under construction. This method had not been verified previously for treating the more concentrated waste as it sits in the tank farm. There are a number of logistical advantages to performing this process in the tank farm. Therefore, the present study was undertaken to compare the removal of 90Sr and 241Am in diluted waste (WTP conditions) and more concentrated waste (tank farm conditions). Both diluted and more concentrated waste from Hanford tank AN-107 was treated with 3.0 M Sr(NO3)2 and 3.8 M NaMnO4, at a constant cold chemical to radionuclide ratio. The amount of 90Sr and 241Am removed was monitored through alpha and beta counting. The removal of 90Sr was essentially identical at both levels of dilution. The removal of 241Am was slightly better in the diluted sample than in the tank farm sample, but the difference was not large (77 % versus 67 % removed). These results indicate that it is reasonable to expect this 90Sr and 241Am removal process can be employed in the tank farm. (author)