Chemistry in pyrolysis of spent organic ion exchange resins arising from nuclear power plants

Organic Ion Exchange (IX) resins used to purify primary coolant of nuclear power plants contain high 137Cesium and 60Cobalt activities. Pyrolysis of IX resins leads to release of radioactivity, SO2, styrene, toluene, ethyl benzene and trimethyl amine to the off gases. 137Cesium and 131Iodine release was found to be 0.009 and 17% respectively at 300 degC and 0.05 and 42% respectively at 350 degC. The organic matter in off gases could be successfully oxidised by using CuO.CuCr2O4, Cu0.15 Ce0.85O2+x and V2O5 catalysts above 475 degC and 22500 hr-1 space velocity. Catalytic combustor along with condenser, NaOH scrubber and an activated charcoal bed provide efficient off gas treatment system for IX resin pyrolyser. Such elaborate off gas treatment makes the process attractive on plant scale unlike incineration. (author)