Aomori Prefectural Government (Aomori Pref.) and Japan Nuclear Fuel Limited (JNFL) have been carrying out tritium monitoring of many kinds of environmental samples around the Rokkasho Reprocessing Plant (RRP) as part of environmental radiation monitoring. Similarly, Aomori Pref. and Tohoku Electric Power Co., Inc. have been carrying out monitoring around the Higashidori Nuclear Power Station. Results which exceeded the background levels of environmental tritium were observed in water vapor, some seawater samples and some fish samples (measured as tissue free-water tritium(TFWT)) since the final commissioning test using actual spent nuclear fuels (Active Test) was started at the RRP on March 31 2006. Therefore, we examined causes for these results by considering the operational status of the RRP and meteorological and hydrographic conditions. The committed effective dose estimated by using the results for the effect of the RRP was far below the annual dose limit for the public (1 mSv).