In order to study the effect of 3H released from the commercial spent nuclear fuel reprocessing plant on 3H concentration in the local fresh water environment, river water and well water samples were collected at seventeen and nine points, respectively, around the plant. Concentrations of 3H were measured in the samples collected during the period of the final testing using actual spent fuel in the plant. The stable isotope ratios of hydrogen and oxygen in water samples were also measured for a hydrological study around the plant area. Concentrations of 3H in the river water samples were in the background level, and their variation among sampling locations was small. Although well water samples also did not have significantly high 3H concentrations originating from the 3H released from the plant, the variation in 3H concentration among sampling locations was larger than that in the river water samples. Comparison of D and 18O data with a local meteoric water line suggested that groundwater around the plant area is mainly recharged by precipitation in winter.