Carbonization-cementation process for treatment of spent IX resins

The spent IX resins containing radioactive fission and activation products of reactor structural materials are highly active solid wastes generated during operations of nuclear reactors. Feasibility tests were conducted for carbonization of IX resins to achieve weight and volume reduction and destruction of functional groups so as to make them compatible for immobilization in cement matrix. Carbonization of non-radioactive resins was studied at 250 to 350 degC. Carbonization residues were 20 to 32 wt% depending upon the type of resin and temperature of carbonization. The release of 137Cs activity to off-gases was 0.004% at 300 degC and 0.05 % at 350 degC. Based on these tests, a 50 liter/batch capacity inactive resin carbonization pilot plant was set up. Carbonization residues could be immobilized into cement matrix with 60 wt % loading using vermiculite and precipitated silica as admixtures. The cumulative fraction of 137Cs leached from the selected cement matrix was 0.0066 in 200 days. Based on pilot plant studies and cementation tests, the swollen spent resins waste volume could be minimized by 2.7 times. (author)