Abstract: Monitoring program and quality assurance measures of ¹³⁷Cs activity concentrations in the seawater near the Tianwan nuclear power station were described, and emission amounts of ¹³⁷Cs through gaseous and liquid pathways since commercial operation and monitoring results in 2004—2015 were given. The monitoring results were compared with background survey results and the reference value for seawater quality. It showed obvious difference in ¹³⁷Cs activity concentrations between monitoring results and the background survey results, and the monitoring results were far below the reference value for the seawater quality standard.

Key words: nuclear power station, Tianwan, surrounding waters, ¹³⁷Cs