[M-AG34] Radioisotope migration: New Development of Environmental Dynamics Research on the 1FNPS Accident

[MAG34-04] Simulation of tritium releases into the ocean from the Fukushima Daiichi Nuclear Power Plant

★Invited Papers

*Alexandre CAUQUOIN¹, Maksym A Gusyev², Yoshiki Komuro³, Kei Yoshimura¹ (1.Institute of Industrial Science (IIS), The University of Tokyo, Kashiwa, Japan., 2.Institute of Environmental Radioactivity (IER), Fukushima University, Fukushima, Japan., 3.Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan.)

Keywords:tritium, FDNPP, ocean, climate model

Following the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011, large quantities of radioactive materials were released into the atmosphere and ocean. Since the FDNPP nuclear accident, Tokyo Electric Power Company (TEPCO) operators have been implementing measures to reduce groundwater inflow into the FDNPP damaged reactor buildings while pumping water to cool the nuclear reactors and fuel debris. The resulting huge water volume began the discharge into the ocean from August 2023, after being treated by an Advanced Liquid Processing System (ALPS) to remove radionuclides for acceptable discharge levels except tritium. Tritium releases from the FDNPP accident and the ALPS treated water raise questions about the concentration of tritium in Fukushima coast and its oceanic transport from the site.

In this study, we used the ocean general circulation model COCO4.9, which is the ocean component of the Model for Interdisciplinary Research on Climate, version 6 (MIROC6 [1]), to simulate tritium concentration in the ocean following the accident and due to ALPS treated water release planned by TEPCO in the coming decades. For the FDNPP accident, we applied a monthly estimate of tritium oceanic discharge inventory [2] as input to COCO4.9, which allows us to distinguish the influence between these FDNPP and atmospheric precipitation releases in the ocean. For ALPS treated water releases, we evaluate the spatial distribution and temporal evolution of projected tritium concentration in different parts of the Pacific Ocean according to the future discharge scenario from TEPCO.

[1] Tatebe et al., Geosci. Model Dev., 12, 2727–2765, doi:10.5194/gmd-12-2727-2019, 2019.
[2] Machida et al., Journal of Nuclear Science and Technology, 60(3), 258-276, doi:10.1080/00223131.2022.2093800, 2023.