Processes, systems, and methods for selectively regenerating an ion exchange resin generally comprises washing the ion exchange resin with an elution agent that encourages only selected contaminants, and especially selected radioactive isotopes, to disengage or decouple from the resin and enter solution in the elution agent, which thereafter is identified as the elution agent solution. The elution agent solution is then passed through a column of isotope-specific media (ISM). When the selected radioactive isotopes within the elution agent solution come into contact with the constituent media isotopes of the ISM, the selected radioactive isotopes are retained on the reactive surface areas of the ISM or within the interstitial spaces of the porous structures of the constituent media isotopes of the ISM. In some embodiments, the constituent media isotopes of the ISM are embedded, impregnated, or coated with the specific radioactive isotope that the particular ISM are adapted to separate.