Long-Term Monitoring of Tritium Concentration in Environmental Water Samples Collected at Tono Area, Japan

Abstract

A deuterium plasma experiment is being planned at the Large Helical Device (LHD) at the National Institute for Fusion Sciences (NIFS). To delineate the regional background tritium concentration level before initiation of the experiment, we evaluated tritium concentrations in environmental water samples (river water, pond water, well water, tap water, and rainwater) collected at Tono area, Japan since 1982. Tritium concentrations in environmental water samples ranged widely from N.D. (below the instrumental detection limit of 0.27 Bq L−1) to a maximum of 4.39 Bq L−1. Tritium concentrations at 9 continuous monitoring locations over the 15 years ranged from N.D. to 1.36 Bq L−1. This regional background concentration range will be used to evaluate environmental assessments after the initiation of the deuterium plasma experiment in LHD.