Sodium titanate decontamination

Sodium titanate has been found to be very effective in removing Sr from defense waste typified by a 6m NaNO - 0.6m NaOH solution also containing the sodium salts of aluminate, nitrite, phosphate, carbonate, sulfate, and chromate in the range of O.lU to 0.007 N and Sr in the analytical concentration range of O.OU to O.U ppm ( ). Sodium titanate columns have provided a Sr decontamination factor of greater than io3 for 2500 column volumes of the waste at flow rates of 2 to 6 column volumes per hour. The material has also been shown to remove residual actinide contamination from the same and similar waste streams ( ). 

The baseline process, including the pressure sintering step, was demonstrated with both simulated high level waste and under hot cell conditions using a waste solution prepared from typical spent light water reactor fuel. A batch contacting method using sodium titanate was also evaluated, but the overall decontamination factor was much lower than obtained in the column process. 

The supemate would be transferred to a dedicated tank and decontaminated by adding tetraphenylborate causing the Cs, K, and Na to precipitate out of solution. Also, sodium titanate would be added to adsorb Sr, U, and Pu. This mixture of solids would than be concentrated by filtration forming a precipitate slurry and low level waste solution. The solution would be processed into grout at the Saltstone facility while the precipitate sluny would be transferred to the DWPF. 

The fixed bed ion exchange column provided a much higher level of decontamination and since the goal was to produce an effluent with mini mi im contamination, it was eventually considered to be the baseline process. In this approach, the waste solution which were approximately IM in HNOo, were adjusted to a pH of 0.5-1 by addition of sodium hydroxide and flowed through a titanate bed at one column volume per hour. The columns were subsequently washed with water to remove excess sodium. 

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