Isotopic evidence of plutonium release into the environment from the Fukushima DNPP accident

TLDR

The Fukushima Daiichi nuclear accident released large amounts of radioactivity, with volatile fission products widely distributed, yet the release of non‑volatile actinides such as plutonium remains uncertain a year later. We present isotopic evidence that plutonium was released into the atmosphere and deposited on the ground within 20–30 km of the plant. The unusually high 241Pu/(239+240)Pu activity ratio (>100) indicates significant 241Pu release and ingrowth of 241Am, underscoring the need for long‑term dose assessment and informing reactor damage estimates and decontamination strategies.

Abstract

The Fukushima Daiichi nuclear power plant (DNPP) accident caused massive releases of radioactivity into the environment. The released highly volatile fission products, such as (129m)Te, (131)I, (134)Cs, (136)Cs and (137)Cs were found to be widely distributed in Fukushima and its adjacent prefectures in eastern Japan. However, the release of non-volatile actinides, in particular, Pu isotopes remains uncertain almost one year after the accident. Here we report the isotopic evidence for the release of Pu into the atmosphere and deposition on the ground in northwest and south of the Fukushima DNPP in the 20-30 km zones. The high activity ratio of (241)Pu/(239+240)Pu (> 100) from the Fukushima DNPP accident highlights the need for long-term (241)Pu dose assessment, and the ingrowth of (241)Am. The results are important for the estimation of reactor damage and have significant implication in the strategy of decontamination.