Investor Presentaiton
Summary
In this presentation, we summarizes mass balance of the Fukushima-derived
137Cs released to the atmosphere and ocean prior to 2018 as well as the 137Cs
inventories on land and in the ocean, biota, and sediment. We propose that
the consensus value of the total amount of 137Cs released to the atmosphere
was 15-21 PBq; atmospheric deposition of 137Cs on land was 3-6 PBq;
atmospheric deposition of 137Cs on the North Pacific was 12-15 PBq; and
direct discharge of 137Cs to the ocean was 3-6 PBq. We also evaluated the
movement of 137Cs from one domain to another for several years after the
accident. We calculated that the amount of 137Cs transported by rivers might
be 40 TBq. The annual deposition of 137Cs due to resuspension at Okuma
during the period 2014-2018 was 4-10 TBq year-1. The 137Cs discharged to
the ocean was 0.73-1.0 TBq year-1 in 2016-2018. The integrated amount of
FNPP1-derived 137Cs that entered the Sea of Japan from the Pacific Ocean
from 2011 until 2017 was 0.27 ± 0.02 PBq, 6.4 % of the estimated amount of
FNPP1-derived 137Cs in Subtropical Mode Water in the North Pacific. The
integrated amount of FNPP1-derived 137Cs that returned to the North Pacific.
Ocean through the Tsugaru Strait from the Sea of Japan was 0.11 ± 0.01 PBq.
Decontamination efforts removed 0.134 PBq of 137Cs from surface soil prior to
February 2019, an amount that corresponded to 4 % of the 137Cs deposited on
land in Japan.View entire presentation