The invention relates to systems, apparatus and methods for the removal of cesium and other radionuclides from liquid waste contained in a high level waste tank. The invention includes transporting a stream of the liquid waste from the high level waste tank to one or more ion-exchange column assemblies to remove the cesium therefrom using a sorbent, such as, crystalline silico-titanate. The ion-exchange column assemblies include an ion-exchange column and an integrated shield. The column is concentrically positioned within the shield and an air gap is present between the column and the shield to provide passive cooling.