[en] This new pulsed EPR method is providing data on H-atom reaction rates in water, which are important in radiation chemistry of aqueous solutions, eg, corrosion in reactor cooling systems, H2 production in high-level radioactive waste, and spread of radioactive iodine following the Chernobyl accident. This AECL-Argonne collaborative effort was undertaken to investigate fundamental aqueous H-atom chemistry for the purpose of developing predictive models of iodine transport that will be used by the nuclear power industry to enhance plant safety. Reactions of (H)_aq with many representative organic and inorganicmolecules have already been investigated. Radiolysis of aqueous solns with 3-MeV electrons produces H atoms in high yield; in the free induction decay method, a powerful 30 ns microwave pulse is applied immediately following pulse radiolysis, creating a phase coherence of the H-atom electron spins that is detected in the pulsed EPR spectrometer as a damped cosine free induction decay (FID). Natural decay time of the spin coherence is many microseconds, but if a reaction partner for the H atoms is introduced, the FID becomes shorter, revealing the H reaction rate. Results of H atom reaction with benzene, methanol, periodate and periodic acid are discussed briefly