Since August 24, 2023, the process of releasing treated water accumulated
at the Fukushima Daiichi Nuclear Power Plant operated by Tokyo Electric Power Company into the Pacific Ocean commenced.
Consequently, in December 2023,
seawater samples were collected and compared with seawater samples from before July in terms of cesium-137 concentration.
※Each measurement was conducted for 259,200 seconds using a germanium semiconductor detector (GCD-70200).
To measure tap water and seawater, extremely low detection limits are required. Tap water is not nondetectable (ND).
Before 3/11, tap water had an average of 0.04 mBq/kg nationwide (Japan Analysis Center: Analysis of FY 2008).
According to the environmental radiation monitoring surveyaround nuclear facilities,
seawater at any location (except Fukushima) shows measurement results of approximately 1 to 3 mBq/kg.
At our measurement facility, with the cooperation of the Nuclear Material Information Office, we employ a concentration method called the AMP method.
Using a chemical called ammonium phosphomolybdate, we concentrate samples of 40 to 50 liters over about three days.
These samples are then measured for an extended period using a germanium semiconductor detector.