The present aim of this program is photochemical removal of the 7 ppM concentration of DTO in D2O that is presently found in active heavy water fission reactors (e.g., Savannah River). Though only T/D recovery is under present scrutiny at LLNL, T/H separation can also be performed using infrared laser multiple-photon dissociation (MPD). Laser-based tritium recovery from both light and heavy water may prove to be of great importance in fusion reactors. The overall cycle of the process under investigation entails initial tritiation of a fully deuterated working molecule by catalyzed chemical exchange with the contaminated heavy water, followed by isotopically-selective, room temperature, gas phase, pulsed infrared laser MPD of only the monotritiated molecules, among the transparent, majority fully deuterated specie. In the MPD interaction, the resonant molecule selectively absorbs 30 or more infrared quanta and then dissociates. The tritium-enriched photoproducts are easily removed from the reactant mainstream by physical separation means. Then the cycle continues with retritiation of the photochemically-detritiated working molecule.