Repères - N°48 / March 2021 - The IRSN magazine - 6

JAPAN 2021

Defueling, environmental contamination, return
of inhabitants, decontamination... What is the situation now,
ten years after the accident? What are the consequences
for people and the environment?
Lower doses measured in forests

The radionuclides released in 2011 drifted
away primarily towards the ocean, and to
a lesser extent towards land, depositing on
vegetation and on the ground (80% of these
terrestrial deposits were on forests).
Furthermore, these radionuclides have
decayed-between 2011 and 2020, iodine-131
for instance has disappeared, whereas the
radioactivity of cesium-137 has decreased
by 20%-and were partly absorbed by plants.
As early as 2011, IRSN launched the
AMORAD research project in collaboration with the University of Tsukuba (Japan)
and Andra1 (see p. 20). Four field experiments in Japan, examining 5,000 samples
from trees and soils, have provided insight
into the cesium transfer cycle through the
various forest compartments (leaves,
branches, bark, wood, roots, humus, litter,
soil and mineral). " In 2020, 75% of initial
cesium deposit in the forest is now in the

5%

Landing value of fish and
fishery products in 2016,
compared to pre-accident
figures*.

220 billion euro

The direct cost of the accident**.
This figure includes compensation
for damage and losses to farming,
fishing, tourism, the cost
of managing contaminated
territories, etc.
* Source: T. M. Nakanishi et al. (eds.),
Agricultural Implications of the Fukushima
Nuclear Accident (III), 2019.
** Sources: Various: Japan, IAE, EIA.

Page 6 - Repères No. 48 - March 2021

soil, and 5% is still in the trees. As it migrates
through the soils, this progressively reduces
the exposure of anyone entering the forest, "
explained Frédéric Coppin, Geochemist.
This research feeds into models used to
protect people.
n	

Corium in all its forms

The priority for dismantling operations is
to remove the corium formed by the molten
fuel still inside the reactor vessels or mixed
with concrete at the bottom of the reactor
buildings. This is also the most complex
part of the dismantling program.
Given the radiation levels, far too high for
human intervention, the Tokyo-based
utility, TEPCO, deploys robots. The robots
are used to explore the site and collect
samples of the corium, in order to characterize its hardness and granularity, etc.
The ultimate goal of this operation is to
select the most suitable technology for
detecting, cutting and collecting the many
tons of this highly-radioactive material.
" IRSN, which has devoted extensive work
to such severe accidents, is now involved to
assess the characteristics of the various
forms of corium and minimize the risks of
dispersion inherent in cutting them up, "
explained Didier Vola, Head of severe accidents department (see p. 11 and 13). The
dismantling program is expected to last
thirty years.
n	

An interim disposal facility for bags of contaminated
soil from Fukushima Prefecture in 2016.

A mountain of waste

To protect the population from exposure,
Japan has set an additional dose limit at
1  mSv/year and launched a proactive
cleanup program. This has generated
around 20 million cubic meters of waste.
At the start, this waste was grouped
together at temporary storage sites, called
kariokiba. This waste will be sorted, incinerated or possibly reconditioned, and then
transferred to a single temporary storage
site in Fukushima Prefecture in the case
of waste exceeding 8 kBq/kg. Studies are
ongoing to find other solutions for

© Tepco

n	

© Kyodo/MAXPPP; © Noak/Le Bar Floréal/IRSN Media Library

State of affairs: Ten years later

A robot collects the corium from inside
the Reactor 2 containment. The aim is to assess
its characteristics prior to dismantling.
Repères - N°48 / March 2021 - The IRSN magazine

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