NMoARCH.420218

T h e IRSN m a g a z i n e

INSTITUT DE RADIOPROTECTION
ET DE SÛRETÉ NUCLÉAIRE

SPECIAL ISSUE

Fukushima Daiichi

What progress 10 years later?
SAFETYHEALTHEMERGENCYOn the cover: Color-enhanced satellite image of the Fukushima Daiichi nuclear power plant (Japan), September 2013.
An IRSN expert at the Cruas-Meysse nuclear power plant (Ardèche department, France) during the Complementary
Safety Assessments in 2011.
Measuring radioactivity using a Safecast device in the Fukushima region.
Estimating post-accident zoning during an exercise in Chinon (Indre-et-Loire department, France), December 2020.

P.4

JAPAN 2011

The accident at Fukushima Daiichi

What happened?
P.6

irsn.fr/R48-EN

OnlineWEBMAG
READ

JAPAN 2021

© EDF

Contents
Ten years later

What is the state of affairs?

P.8

SAFETY

Extreme risks

Enhanced protection for nuclear facilities
Station blackout diesel generator

SafetyLocal emergency centersto stand firm during extreme
situations

Assessments made during design

READ

Severe accidents

Ultimate heat sink performance
Tricastin nuclear power plant

Dike reinforcements follow assessment
ResearchInnovative materials
P.14 EMERGENCY

Research

Understanding
and modeling the accident

Emergency management and recovery

READ

Defining new zoning
P.18 HEALTH
Population protection

What progress has been made in ten years?
P.20 ENVIRONMENT
Environmental contamination

Emergency

Three questions for Patricia
Dupuy on IRSN’s Emergency
CenterModels are progressing
2011-2021

IRSN’s actions© France 3 Normandie

P.22 IRSN

READ

Emergency

Post-accident management
should include social
consequences
Page 2 - Repères No. 48 - March 2021

Dialogue, independence,shared expertise© EDF - Gaëtan Bouvier

READ

Emergency

What human resources to callupon in extreme situations?

READ

Environment

A mapping tool to help local
stakeholders prepare

About Repères
Enhancing nuclear safety is the main
driver behind IRSN’s every action.
As such, the Institute takes its commitment
to making the results of its research, studies
and reports accessible to all professionals
involved in nuclear safety, security andradiation protection, as well as the generalpublic and civil society, very seriously.
This is why the Institute publishes aquarterly French newsmagazine, Repères,which provides information on IRSN’s
activities in the fields of research,radiological surveillance, nuclear safety andsecurity, and reflects the broad extent of
its expertise. The international significanceof the Fukushima Daiichi accident is what
has prompted publication of an English
version of this special issue focused on theaccident and on the lessons learned by
IRSN ten years on regarding nuclear safety.

Ten years have passed since the Fukushima Daiichi disaster.
This accident, like those before it, has led IRSN to conduct
extensive research and take action to enhance safety at nuclear
facilities and radiological protection of people and theenvironment. We must do everything within our power toprevent accidents, even though there are no guarantees
that they will not occur. In this special edition of Repères,we review the situation.
One of the key findings resulting from the Fukushima Daiichi
accident has been that decisions made during the emergency
response stage have had a major impact on managing
the long‑term consequences. To ensure that environmental,social, health, and radiological aspects are factored into
decisions made with a view to post-accident management,
the wider public—including citizens, elected officials,
and associations—must be involved in the choices made; thisis especially true since such accidents entail a loss of confidence
in authorities and experts. In such a complex situation, it
is essential to ensure that citizens have the resources necessary
to make their choices, notably, by encouraging radioactivity
monitoring initiatives or sharing expertise more widely.
To conclude, I firmly believe that experts’ involvementin these types of situations must be based on
ethical principles: respect for other people’s
right to freedom and independence,transparent communication on the risks,and honesty regarding the limits of what
we can do and the uncertainties inherent
in our knowledge. As experts, we musthave faith in citizens.

Jean-Christophe Niel
IRSN Director General

MEMBER OF

REPÈRES – Publisher: Institut de radioprotection et de sûreté nucléaire – 31, avenue de la Division-Leclerc, 92260 Fontenayaux-Roses, France – Tel.: +33 (0)1 58 35 88 88 – Website: www.irsn.fr/EN/– Email: reperes@irsn.fr – Executive Editor: Jean‑Christophe Niel
– Director of Communications: Marie Riet-Hucheloup – Editor-in-Chief: Catherine Roulleau – Assistant Editor: Isabelle Cussinet –Contributors: Agnès Dumas, Octavia Veny, Pascale Monti – Review Committee: Louis-Michel Guillaume – Editing and production, art
direction and layout of French version: ABG Communication – Translation: AWS, Caupenne, Provence Traduction – Copyediting: AMC
Communication – Layout and production of English version: Studios Menthe&Chocolat – Iconography: Sophie Léonard – Coverphotography: © National Land Image Information (Color Aerial Photographs); bottom, left © Grégoire Maisonneuve/IRSN Media Library;bottom, center © Noak/Le Bar Floréal/IRSN Media Library; bottom, right © contributors to OpenStreetMap; above © Antoine Devouard/
Drone Press/IRSN Media Library – Printed by: Handiprint (50) – Printed on paper sourced from sustainably-managed forests –ISSN: 2103‑3811 and 2491‑8776 (Web) – March 2021.

INSTITUT DE RADIOPROTECTION
ET DE SÛRETÉ NUCLÉAIRE

Page 3 - Repères No. 48 - March 2021

JAPAN 2011
The accident at Fukushima Daiichi

What happened?

On Friday, March 11, 2011, at 2:46 p.m. local time, a 9.0 magnitude earthquake
struck 130 kilometers off the coast of Honshu Island in Japan. This knocked out off‑site
power at the Fukushima Daiichi nuclear power plant. The reactors shut down, andthe emergency generators started up.
Less than an hour later, a tsunami wave with a run-up height of 14 meters flooded
over the seawall protecting the plant and submerged the emergency generators.
The water intakes needed for reactor cooling were damaged.
Japanese
nuclearfacilities

Tomari© Hervé Bouilly/Médiathèque IRSNPACIFICOCEAN

KashiwazakiOnagawa
KariwaShika
Ohi
Fukushima I
MihamaFukushima IITokaïTakahama
Tokyo
ShimaneHamaoka
Genkai
Monju
Tsugura
Ikata
Fugen
0
200 kmSendai

4

3

2

1

100 m
0

March 11, 2011

Core melt. The earthquake caused theautomatic shutdown of units 1, 2 and 3, as
well as the loss of off-site power. The plant’s
emergency diesel generators took over.
Forty minutes later, the tsunami wave
triggered by the earthquake reached thecoast. The site was hit by seven waves, thehighest measuring fourteen meters high.
It damaged the seawater intakes and shut
down the emergency diesel generators
supplying power to units 1 through 4. The
unit 2 and 3 emergency backup systems
continued to function for a few days,
thereby delaying core melt in these reac‑
tors. The core damage in units 1, 2 and 3
led to radioactive releases into the envi‑
ronment. The decision was made to vent
the reactor containments in order to reducepressure.
Page 4 - Repères No. 48 - March 2021

March 12, 2011

Unit 1. An explosion occurred at 3:36 p.m.
in the upper part of the reactor building,an hour after containment venting began.
Given the loss of cooling systems, the plant
manager decided to inject seawater into
the reactor coolant system as a last resort.

March 14, 2011

Unit 3. The upper section of the reactor
building also exploded, even though it had
been vented 24 hours earlier. Seawater was
injected to cool down the reactor core.

Unit 4. An explosion occurred inside thereactor building, probably caused by an
inflow of combustible gas via the pipes
shared with unit 3.
Unit 2. The operators failed to vent thecontainment. On March 15, in the morn‑ing, the high pressure level caused a break,resulting in significant radionuclide
releases. Seawater was injected to cool thereactor core. n

JAPAN 2011
The Fukushima Daiichi nuclear power plant© 2020 Maxar Technologies

Reactor units 1‑4 at Fukushima Daiichi on March 18, 2011.

5

6

Marine contamination
The marine environment suffered significant
radioactive contamination. This was primarily due
to contaminated water being discharged fromthe plant, which continued up to April 8.
To a lesser extent, the sea was also contaminatedby fallout from some of the radionuclides(e.g. cesium-137) released to the atmospherebetween March 12 and 22.

Units 5 and 6
These reactors were built more
recently and as they are situatedabout ten meters higher up than theother four, they were consequently
able to better withstand theexternal load. One of the emergency
generators for unit 6 was used
to cool the spent fuel storage poolsof units 5 and 6, which were shut
down for maintenance.

Units in operation
Units shut down for maintenanceDifferent reactor technologies

146,520
residents of Fukushima
Prefecture were evacuatedfollowing the accident in 2011,
as ordered by the government.
Source: The Fukushima Nuclear Accident
Independent Investigation Commission
official report (2012).

Although all nuclear power reactors makeuse of fission energy* to generate electricity,
their design differs. The units at Fukushima
Daiichi plant are equipped with boilingwater reactors (BWR), whereas the nuclear
power plants in the French fleet housepressurized water reactors (PWR). The
main difference between these technologies
lies in the type of cooling system:• In a BWR, the water used to cool the reac‑
tor core turns to steam at the top of thereactor vessel before being channeled to theturbine. The steam is then condensed toliquid state in a condenser (cooled by sea‑water at the Fukushima Daiichi plant) before© Hervé Bouilly/Art Presse/ABC Communication/IRSN Media Library/Repères magazine

Atmospheric contamination
The series of decompressions andexplosions resulted in significant
releases of radioactive fission products
to the atmosphere, such as iodine-131
and cesium-137. In the hours
following the accident, the Japanese
authorities decided to evacuate
80,000 people within a 20 km radiusof the site and ordered those living
within a 20-30 km radius to shelterindoors. The most hazardous releases
occurred over a period of three weeks.

The Fukushima Daiichi nuclear
power plant (Daiichi means“Number One”) is made up of
six American-designed Boiling Water
Reactors (BWRs). Built in the 1970s,
it is operated by Tokyo ElectricPower Company (TEPCO). Unit grosspower capacity ranges between
460 and 1100 MWe dependingon the reactor.

being recirculated back into the core.
• The core of a PWR is cooled by a systemcalled the primary circuit in which thewater is pressurized so that it remains inliquid form. The heat from this circuit istransferred to the secondary circuit, an
independent system in which the water
evaporates and drives the turbine.
Both of these technologies are equippedwith various backup emergency systems
which, in the event of an accident, aredesigned to inject water to cool the reac‑
tor core.
* During fission, the nucleus of an atom splits,
releasing a very large quantity of energy.

Page 5 - Repères No. 48 - March 2021

JAPAN 2021

Defueling, environmental contamination, returnof 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 driftedaway primarily towards the ocean, and toa lesser extent towards land, depositing on
vegetation and on the ground (80% of theseterrestrial deposits were on forests).
Furthermore, these radionuclides havedecayed—between 2011 and 2020, iodine‑131
for instance has disappeared, whereas theradioactivity of cesium‑137 has decreased
by 20%—and were partly absorbed by plants.
As early as 2011, IRSN launched theAMORAD research project in collabora‑tion with the University of Tsukuba (Japan)and Andra1 (see p. 20). Four field experi‑ments in Japan, examining 5,000 samples
from trees and soils, have provided insight
into the cesium transfer cycle through thevarious forest compartments (leaves,branches, bark, wood, roots, humus, litter,soil and mineral). “In 2020, 75% of initialcesium deposit in the forest is now in the5%

Landing value of fish andfishery 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 costof managing contaminatedterritories, 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 toprotect people.
nCorium in all its forms

The priority for dismantling operations isto 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 forhuman intervention, the Tokyo-based
utility, TEPCO, deploys robots. The robots
are used to explore the site and collectsamples of the corium, in order to char‑acterize its hardness and granularity, etc.
The ultimate goal of this operation is toselect 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 toassess the characteristics of the various
forms of corium and minimize the risks ofdispersion inherent in cutting them up,”explained Didier Vola, Head of severe acci‑
dents department (see p. 11 and 13). The
dismantling program is expected to last
thirty years.
n

An interim disposal facility for bags of contaminatedsoil 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, calledkariokiba. This waste will be sorted, incin‑erated or possibly reconditioned, and thentransferred to a single temporary storagesite in Fukushima Prefecture in the caseof waste exceeding 8 kBq/kg. Studies are
ongoing to find other solutions for© Tepcon© 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.

JAPAN 2021n

© Noak/Le Bar Floréal/IRSN Media Library

Using an open data device to measure radioactivity
at a storage facility for contaminated soil.

“Breast cancer, thyroid cancer, leukemia...
it’s hard to say that these cancers are causedby radioactive fallout, because the doses
received by the population were generally
low, just a few millisieverts,” Klervi Leuraud
summed up, who specializes in radia‑
tion-induced risk. Among epidemiologists,
this has been the consensus.
It cannot be denied there have been indirect
health effects, including diabetes, kidney
and liver failure, obesity and alcoholism,
but these are thought to result from dis‑
ruption to healthcare services andpost-traumatic stress. Such stress is decreas‑ing, as its prevalence fell by 19% in men
and 27% in women2 between 2012 and 2014.
n© Noak/Le Bar Floréal/IRSN Media Library

In 2016, people displaced from the municipalityof Miharu, in Fukushima Prefecture, were still
living in temporary housing. Most of those who
remain are elderly, as many young people left
the region for good.

Decontamination work on a roadin Fukushima Prefecture, October 2016.

What about theradiation‑induced effects?

Four out of five residents have
not returned

Residents began to return to the area as ofApril 1, 2014. Their return has been slow
and partial. At the beginning of 2020, theaverage rate of return was below 20% for
all municipalities that had received orders
to evacuate, ranging from 2% to 75%.
n

The importance of “facilitators”“The measurements made the radioactivity visible.” According to Jean-François
Lecomte, an expert in radiation protection,
this was one of the key insights resulting
from Fukushima Dialogue, a project backed
by IRSN and that gave a voice to Japanesepeople affected by the accident since 2011.
Citizen initiatives developed to add to theofficial measurements. A farmer in Suetsugi
monitored the radioactivity in his fields,
associations sourced the equipment needed
to take measurements, and residents called
for personal dosimeters. Discussion withexperts help everyone to gain a better
understanding of the situation. That is how

the idea of co-expertise came into being.
Another takeaway was that standards are
not enough. They can even be detrimental.
From 2011, to reassure the population, thelimits relating to the contamination offoodstuffs were lowered. However, someconsumers believe that the limit is proof
of contamination.
What happened in Japan revealed the impor‑tance of “facilitators”, for example teachersand medical or administrative staff who act
as intermediaries between citizens and theauthorities.
nContaminated water,a real headache

In November 2020, there was 1,234,000
cubic meters of tritiated water stored in
1,040 tanks on the nuclear power plantsite. This radioactive water results fromten years of cooling the damaged reactors.
According to TEPCO, the limit of
1,370,000 m3 will be reached in 2022.
In 2016, Japanese experts were looking at
various options. Of these, two are still on
the table and being discussed with stake‑holders: discharge it into the sea (to dilute it)or vaporize it into the atmosphere (as water
vapor). The technical, radiological and soci‑ological advantages and disadvantages ofthese options are being examined.
According to Japanese authorities, theimpact that discharging this water into
the sea would have on people and the envi‑
ronment is comparable to the impact of
nuclear facilities currently in service. n
1.	The French National Radioactive Waste
Management Agency.
2.	Fukushima Health Management Survey.

Find out more:

The Fukushima Dialogue Initiative
irsn.fr/Kotoba-EN

Nearly 170 m3 of tritiated water
are produced every day.

Page 7 - Repères No. 48 - March 2021

© Kyodo/MAXPPP

recycling as well as for sites or disposal
facilities outside Fukushima Prefecture.
The last remaining kariokiba will be­emptied by the end of 2021.
Decontamination has now been completed
within the Intensive Contamination Survey
Area (ICSA). This encompasses the Special
Decontamination Area and the munici‑
palities where the estimated annual dose
was thought to be between 1 and 20 mSv.
“It will take many more years to manage
this waste, and it will be very costly,”
summed up Jérôme Guillevic, an expert
in radiation protection.

SAFETY
Extreme risks

Enhanced protection for nuclear facilities
Following the accident at Fukushima Daiichi, the decision was made to assess the robustness
of French nuclear facilities and their resistance to extreme natural events. IRSN experts
then developed the concept of the “hardened safety core”, whose aim is reinforcing controlof vital safety functions, preventing large-scale releases to the environment and improving
emergency response management.

“H

ow on earth could an accident
like this happen in Japan, acountry renowned for its reliable
technology, rigorous organization androbust construction?” recalled Patrick
Lejuste, post-Fukushima Project Manager,
as he thought back to how stupefied thenuclear community was in 2011.
At the time, ASN, the French Nuclear Safety
Authority, asked licensees to immediately

undertake Complementar y Safety
Assessments (CSAs). They had to assess therobustness of the facilities in the event of amajor earthquake or extreme flooding event.
Seventy-nine CSA reports were drawn up
by the licensees. They identified a numberof deviations/cases of noncompliance, points
for improvement, and presented calculations
on the length of time before releases to theenvironment were likely, etc. In the spaceof just a few months, IRSN had conducteda critical analysis of all these reports andexamined licensee proposals for making
their facilities more robust.
At the beginning of 2012, based on all thesedata and assessments, ASN concluded that
there was no need to close down any ofthe plants. It did, however, require theoperators to check conformity with thesafety requirements and decided to raise

FOCUS
What are the first key measures of the hardened safety core?
Preventing accidents with core melt or slowing down their progression, reducing massive releases of radioactivity and making it
possible for the operator to manage emergency response—these are the three objectives of the hardened safety core program.
It is being deployed across the French nuclear power plant fleet in the wake of Fukushima Daiichi in order to equip it to withstandextreme hazards. Having developed the initiative, IRSN is assessing its design and implementation. After 72 hours, the Nuclear
Rapid Response Force (FARN) takes over to assist on-site. Here, we take a look at the first key measures of the concept.

1 Emergency diesel generators (EDG)
These are used to restore electric power to the hardened
safety core equipment and systems. It is designed to operate
for 72 hours without requiring human intervention.
Implementation expected to be complete in February 2021*

12
3

3 Ultimate heat sink
Sourced from deep groundwater, existing pools or new reservoirs,
the ultimate makeup water supply must ensure site autonomy
for 72 hours in the event of severe natural events leading
to conditions beyond the scope of the original design basis.
It will be used to supply the steam generators, the reactor pooland the spent fuel pool.
Implementation expected to be complete in 2021** Source: EDF

Page 8 - Repères No. 48 - March 2021

Implementation expected to be completein 2026
Commissioned in 2020* at Flamanville
NPP (Manche department)© Art Presse/ABG Communication/IRSN Media Library/Repères magazine

2 Local emergency center (CCL)This must be designed to withstand extreme
natural hazards. It houses emergency
response equipment and can accommodate a staff of about a hundred people
deployed as part of the on-site mobilization
plan and mobile response forces. These
teams carry out diagnostics to assess
facility condition, evaluate releases andadvise public authorities.

SAFETY

Based on feedback from the accident at
Fukushima Daiichi—loss of water supply,
loss of power, not enough manpower—the
aim of the hardened safety core is to “retain
control of the situation and, if necessary, beable to contain severe accidents, no matterthe circumstances,” Lejuste explained.
The concept relies on two key measures:the Emergency Diesel Generator (EDG)
and the Ultimate Heat Sink, designed,
respectively, to ensure electric power for
72 hours and makeup water (see p. 10 and
11). Technical dialogue with EDF1 has beenongoing since 2012. ASN required EDGs
to be installed at all reactors by 2018. The
design of certain parts of the facilities has
also been under review; these must be mademore robust to withstand extreme weather
events: flooding (see p. 12), lightning, tor‑
nados, violent winds, etc.
To improve emergency response manage‑
ment, EDF proposed, within the frameworkof the CSAs, building a Local emergency
center (CCL 2) on every site, designed towithstand extreme hazards (see webmag).
The following year, again on its own initi‑
ative, EDF set up the FARN, the Nuclear
Rapid Response Force (see opposite).
All new equipment is designed withextreme hazards in mind from the very
start. Full implementation of the hardened
safety core measures will be completed inline with the ten-yearly reviews, withexpected completion set for 2038. n
1.	Électricité de France/French national
power company.
2.	Centre de crise local.

WEBMAGAZINE
READ
Local emergency
centers to standfirm during
extremesituations
irsn.fr/R48-EN

Have the ways in whichpeople can participatechanged?

What improvements
could be made?

MB: ASN’s standing
groups are now open to
non‑institutional experts.
YM: The amount of dialogue
We have gotten involved inon technical issues has
a number of these committees,increased. Local informationin particular those pertaining
committees (CLI) holdto facility safety and waste
discussions with the experts
management.
at IRSN, the French Nuclear
YM: Such openness serves
Safety Authority (ASN) and the to enrich the assessment
operators on what are often very process. We often bring
controversial issues, such as
different views to the table.
the anomalies in the Flamanville On reactors, we stress the need
EPR (Manche department)
to stick to the safety margins,reactor vessel. IRSN now
keep a close eye on whether
publishes more information.
the deadlines for implementing
It consults with citizens prior
ASN recommendations are met,
to conducting assessments
and so on.
instead of toward the endof the process. A good exampleof this is the project to createa centralized spent fuel pool.

4 questions for…

MB: Some information should
be made public, such as
monitoring implementationof commitments madeby operators.
YM: We need to get to the point
where the concerns of civilsociety have a real impact ondecisions.

What topics are not being
discussed?

YM: Security. It’s only naturalthat certain aspects, likeanti-terrorist surveillance,
should be classified for defense
purposes. But other subjects,
such as whether civilengineering structures arerobust enough to withstandan aircraft crash, or the ability
to maintain cooling after certain
types of attack, etc., should be
addressed through dialogue
with society.

Manon Besnard
and Yves Marignac© Coll. part ; © B. Runtz

72-hour autonomy vital on site

In what ways has theaccident at Fukushima
Daiichi changed relations
between key players
in the nuclear industry
and civil society?

Independent experts at the Institut négaWatt
Nuclear and Fossil Fuel Energies Unit
© EDF - Bruno Bony/Sipa

the required safety baselines relative tonatural hazards. IRSN proposed a newconcept, that of the hardened safety core.
Every facility has since been required tohave at its disposal the human and organ‑
izational resources and the “last resort”
equipment designed to withstand severe
hazards that go beyond the design-basis
scenarios set out in the safety reference
documentation in force.

The FARN is staffed by 300 trained employees.
Its fleet is composed of 52 all-terrain vehicles
as well as air and river transport craft.

FOCUS

Taking over to deliver a hardened
safety core within 24 hours

As an additional safety measurethat has been in place since 2013,
the FARN (for Force d’action
rapide nucléaire) provides humanresources and equipment in the eventof accident. In 2019, IRSN noted
in a notice that–for a given accident
scenario—the FARN must, without
fail, take action within 24 hours(Notice 2019-00051 on the deploymentof ultimate cooling measures). The FARN
is tasked with maintaining reactor coolingand ensuring supply of water, powerand compressed air.
It takes over to deploy the hardened
safety core measures to keep the situation
under control and prevent core melt or,
failing that, mitigate the consequences.
Page 9 - Repères No. 48 - March 2021

SAFETY
Station blackout diesel generator
Emergency diesel generators(EDG) constitute one of thepillars of the “hardened safetycore”. They supply power
to the vital components ofthe facility in the event that
all other sources of electricity
are lost. IRSN has evaluatedthe design of this additional
equipment, designed towithstand extreme hazards.
EDF1 has announced thatthe system will be fully
operational for all its reactors
by late February 2021.

W

At 24 meters long, 12 meters wideand 25 meters high, the EDG building has
an unmistakable silhouette.

Page 10 - Repères No. 48 - March 2021

© Laurent Zylberman/Graphix-Images/IRSN Media Library

ith a relatively small footprintof 288 m2, the buildings known
as the EDG house the emergency
diesel generators and are erected in close
proximity to the nuclear island. And withgood reason, because in extreme situations,these diesel engines have to take over topower the hardened safety core systems
and components to prevent core melt. If
this fails, they are needed to mitigate theconsequences by preventing large-scalereleases to the environment (see p. 8). How
were safety experts involved in overseeing
the design process?
These bunkered buildings must withstandextreme situations. “Made of reinforced
concrete, with 50 centimeter-thick walls,© Grégoire Maisonneuve/IRSN Media Library

Assessments made during design

Safety experts carry out inspections at the Cruas nuclear power plant (Ardèche department) as partof the Complementary Safety Assessments (CSAs) held in the wake of the Fukushima Daiichi accident.

they built to withstand extreme natural
phenomena and the resulting effects, forexample lightning, hail, tornados andearthquakes,” explained Marie-Hélène
Bonhomme, a civil engineering expert.
Beginning in 2016, IRSN examined thereliability of the station blackout emergency
diesel generator (SBO-EDG), designed tooperate for 72 hours, checking its output
capacity to supply the electric power
required (3 050 kW). It subsequently pub‑lished an initial technical report 2. “IRSN
found the initial design-basis scenarios
satisfactory,” Patrick Lejuste, post-Fukus‑
hima Project Manager shared.
The electrical power distribution system
for the hardened safety core supplied by
the SBO-EDG and the measures imple‑
mented to protect it were also assessed 3.
More recently 2, they assessed whether the
power provided by the diesel generator isadequate to meet the requirements of theequipment it is intended to supply.

Recommendations onearthquake-resistant design

In addition to the generator, the EDG
buildings also house lubrication pumps,
fuel oil tanks, a ventilation system, batteries,
a circuit breaker panel and a fire detection
system. No human intervention is required.

In the event of a power outage, the gener‑
ator starts up automatically. “The anchoring
systems on each part of the equipment
are designed to withstand the effects of ahardened safety core-level earthquake,”
explained Lejuste.
In 2016 2, IRSN made a recommendation
regarding the seismic resistance, assump‑
tions and methods for the design basis of
structures housing the EDGs. Operators
are required to ensure adequate safetymargins.
In 2012, ASN, the French Nuclear Safety
Authority set a delivery deadline for the
56 station blackout EDGs for 2018. By theend of 2018, two were operational, both at
the Saint-Laurent-des-Eaux site in the Loiret-Cher department. Since then, the otherreactors in the French fleet have beenequipped gradually. According to EDF, allwere scheduled to be operational by
February 2021. n
1.	Électricité de France/French national powercompany.
2.	IRSN notice 2016‑00187, plus five additional
reports on commissioning the EDGs: 2017‑00042(P4 subseries, 1300 MWe plant series),
2017‑00131 (CPY plant series), 2017‑00318(P4 subseries, 1300 MWe plant series),
2017‑00344 (N4 plant series) and 2018‑00109(Bugey CP0 plant series).
3.	IRSN notice 2017‑00058.

SAFETY
Severe accidents

Ultimate heat sink performance
The containment heat removal system, as part of the “hardened safety core”,
plays a key role in the event of a severe accident. IRSN has examined its performanceand made some recommendations for additional improvements.
c­ onnected to the heat sink by the FARN, theRapid Nuclear Response Force,” (see p. 9)
explained Estelle Dixneuf, an expert in thefield of safeguard systems design.
According to IRSN’s calculations, that isthe potential source of any problems. Julien
Chambarel, an expert on severe accidents,
explained: “Thanks to our calculations,­performed using ASTEC code, we have identified a risk in the event of an accident inwhich design-basis pressure in the containment is exceeded in the first 24 hours, requiring containment venting. That is precisely
the amount of time needed for the FARN toconnect the heat sink to the UCHRS heatexchanger.”
This has led to an IRSN recommendationin the event of a severe accident. Now, an
additional step must be added to the listof necessary actions, which is to resupply
the external borated water tank and inject
its contents into the reactor building as
quickly as possible. n

The Tricastin plant heat exchanger shown hereis the centerpiece of an ultimate heat sink.
It measures 7 meters long and weighs around9 metric tons.

© EDF - Cyril Crespeau (08/2020 all rights reserved)H

ow effective is the ultimate contain‑
ment heat removal system (UCHRS)?
That is the question put to theexperts at IRSN regarding this part of thehardened safety core system. Its role is toremove residual heat from the contain‑
ment, including under severe accident
conditions. The ultimate containment heatremoval system is called upon when thesafety injection system and the contain‑
ment spray system both fail.
It is required in order to prevent any open‑
ing of the containment venting and filtra‑tion system which would result insignificant releases to the environment.
Since 2015, IRSN experts have assessed thedesign, reliability and performance of thesystem proposed by EDF to mitigate theconsequences of an accident with core melt.
“The ultimate containment heat removal
system injects borated water 1 contained ina tank into the reactor vessel and into thesumps at the bottom of the containment. Once
this tank is empty, the system draws waterfrom the sumps to recirculate it and cool it.
It is cooled by a UCHRS heat exchanger

1.	Boric acid is added to the water in the reactor
coolant system due to its neutron-absorbing
capabilities.

RESEARCH

Containment

BasematCreating a more robust basemat
uring the accident at Fukushima Daiichi,
molten fuel penetrated through the reactor
vessels and flowed down onto the basemat.
The basemat, made of reinforced concrete, acts as
the foundation supporting the reactor containment.
To maintain containment integrity, ablationof basemat by the corium must remain limited.
How is this risk managed in France? In 2019,
IRSN published a notice1 that addresses this issue.
As part of the studies on extending the service lifeof its 900 MWe reactors, EDF is developing astrategy for managing the flow of corium following
melt-through, often referred to as “ex-vessel
corium”. The principle behind this entails allowing
the corium to spread at the base of the reactor
where it is then stabilized under water.
The experts at IRSN have thirty years of researchon which to base their analysis of this strategy.

Experiments are carried out to study how
depleted uranium, replicating the actual fuel,interacts with the types of concrete (limestoneor siliceous) used in reactor units.
Computer simulation is then used to study
conditions at full scale. “When siliceous concreteis used, as is the case in fourteen reactors in France— Corium
our experts recommend making the base of thereactor thicker, to minimize the risk of melt‑through,”explained Gérard Cénérino, an expert on
severe accidents. This research complements
other international post-Fukushima projects 2(see p. 13 and the Webmag).
Basemat1. IRSN/Notice 2019‑00051.
2.	PreADES, ARC-F and TCOFF,
under the auspices of the OECD.

© J.-Y. Pipaud/EPSIM/IRSN Media LibraryD

Illustration of a core melt accident with thecorium flowing down and starting to interact
with the basemat concrete.

Page 11 - Repères No. 48 - March 2021

SAFETY
Tricastin nuclear power plant

Dike reinforcements follow assessment
monitoring plan will ensure that thedike remains stable in the event of a safe
shutdown earthquake (SSE). The monitoringplan developed by EDF is based on
piezometric 2 level measurements.
Nonetheless, assessment experts highlighted“the absence of a design margin for an earthquake exceeding the SSE baseline.” They
recommended overall reinforcement of thedike. It must now withstand a “hardened
safety core design basis earthquake”3. IRSN
also stated that the specific features of thesite must be taken into account, primarily
because of the soil characteristics.
In 2020, EDF drew up a file detailing its
planned measures and works, which will
be examined by IRSN. n
1.	Électricité de France/French national
power company.
2.	Measurements taken of the water levelin the dikes.
3.	Extreme earthquake used forthe hardened safety core design baseline
for facilities, as specified following
the Fukushima Daiichi accident.

FLOODING
SOFIA simulator

Simulating flooding“Taking seismic risk into account as
it has been up to now is notenough anymore,” explained
Olivier Loiseau, Safety expert. He goes on
to say that “the accident at Fukushima
Daiichi showed us that nature can be much
more powerful than the hazard levels usedby design engineers in facility design.”
As a result of IRSN’s recommendations,
EDF1 has had to meet higher safety require‑ments at all its facilities. This applies to a
precise list of existing protective equipment
and systems, which are part of the hard‑
ened safety core, since they are necessary
for carrying out safety functions (see p. 8).
These new requirements apply to the dikethat protects the Tricastin nuclear power
plant. Here, we look back at the timelineof events and the assessment conducted.
On September 27, 2017, ASN ordered EDF
to temporarily shut down all four reactors
at Tricastin, in order to reinforce a sectionof gravel dike measuring a few hundred
meters. In the event of an earthquake, it
could collapse. EDF conducted additional
geotechnical investigations and reinforced
the section.
IRSN analyzed the data submitted by EDF
and drew up its own design calculations.
IRSN believed that the works and thePage 12 - Repères No. 48 - March 2021

Robin Dorel, a specialist in charge of the SOFIA simulator, presents the schematic control pannelof the main feedwater system of the steam generator for the 900 MWe reactors.

Is safety assured at the Tricastin nuclear power
plant (Drôme department) while work
to reinforce the Donzère‑Mondragon canaldike is ongoing? To find out, IRSN safety experts
used the SOFIA1 simulation tool.
The following critical situation is considered,in which an earthquake has destroyed theweakened part of the dike, the site is flooded
and must deal with the total loss of power supply
and cooling water. SOFIA was used to model
the consequences of such an event withthe aim of facilitating analysis of the measures
implemented by EDF to manage it2.
Starting from the initial state of the facility
as selected by EDF, which considered residual heatequivalent to that of a reactor in shutdown state
for fourteen days, the tool calculated the physicalparameters of the reactor in real time. It simulatedchanges in pressure, core outlet temperature,and the flowrate in the reactor coolant system, etc.
These calculations gave an estimate of 37 hours
for the steam generators to drain, and the time
to core uncovery as 62 hours. That means© Laurent Zylberman/Graphix-Images/IRSN Media Library

Since the accident at
Fukushima Daiichi, nuclear
facility design had to be
improved to ensure that itwithstand exceptional events.
This led to the “hardened
safety core”, which includes
assessing the strengthof infrastructure built
to protect sites, such as
the Donzère‑Mondragon
canal dike that borders
the Tricastin nuclear power
plant (Drôme department).
IRSN recommended
reinforcing it.

that the Nuclear Rapid Response Force (FARN),
which can reach the site in 12 hours, has enoughtime to respond.
More recently 3, SOFIA has been used to validate
operating a 900 MWe reactor following an extreme
hazard. Robin Dorel, who manages the simulator,
pointed out that “the new ‘hardened safety core’equipment and systems must be taken into account.
Simulation demonstrated that the facility wasstrong enough to resist.”
1.	Simulator for Observation of Functioning
during Incident and Accident.
2.	EDF memo dated October 9, 2017 –“Measuring resilience with regard
to the conditions considered for shutdownof the four reactors in the event of flooding
on the NPP platform.”
3.	Supporting the assessment of operating
strategies in the event of extreme loads
for reactors in service.
For more information:
The SOFIA simulator
irsn.fr/sofia-EN

SAFETY
ResearchInnovative materials
Research was launched after the Fukushima Daiichi accident in order to better protect
the population. Case in point with two programs, MIRE, focused on limiting radioactive
releases, and PreADES, which studies the recovery of fuel debris to prepare fordismantling in Japan.

Iodine filtering in containment
venting lines

To improve filtration system efficiency incase of containment venting, research is
focusing on innovative materials. “Zeolites[minerals mainly composed of aluminumand silica] enriched with silver very significantly improve the trapping of volatile
iodine, with good resistance to heat andradiation,” said Laurent Cantrel, Project
Lead. He goes on to say, “We are working
on the aging of these materials and theirperformance in severe accident conditions.
Our recommendations could be used as
input by EDF, whose role is to decide which© Francesco Acerbis/IRSN Media LibraryT

en years after the accident, knowledge
and safety are improving throughnumerous research projects under‑
taken in France and internationally. Bybringing to light how vulnerable facilities
are to extreme natural hazards, the 2011accident led to a review of priorities andstimulated preliminary safety research.
It is essential that radioactive releases in
the form of aerosols or gases be limited
during a core meltdown in the event of an
accident. Characterizing the chemical
species released is also important because
their impact on humans and the environ‑ment differs according to their physi‑
co-chemical form. These objectives are at
the heart of the MIRE1 collaborative pro‑
ject, led by IRSN.

The PERSEE facility is devoted to studying iodine traps in nuclear facilities.

s­ olution to deploy to mitigate iodine releases.”Scientists began by deepening their knowl‑edge of the nature of iodine releases with
IRSN’s CHROMIA 2 platform. Then, they
compared the trapping capacities ofthe existing filtration systems on anotherfacility, PERSEE 3. Two zeolites wereselected for the final studies. When mod‑ified, these porous materials can increase
their chemical affinities with gaseousiodine to selectively trap it. The additionof silver proved most effective.

Debris analysis

The purpose of the OECD PreADES 4­project is “to prepare for dismantling
Fukushima Daiichi. The Japanese asked us toinventory the debris formed by the accident
and their properties, explained Marc
Barrachin, specialist in severe a­ ccidents.
IRSN provided its knowledge on core melt‑
down accidents, “acquired
through the Phébus PF 5
program, based on fivesmall-scale core meltdown
tests c­ arried out under the
program,” he continued.
Lessons were learned on
Understanding
the degradation of theand modelingcore and fission productthe accident
behavior. Debris analysis
campaigns were con‑
irsn.fr/R48-EN

WEBMAGAZINE

READ

ducted. PreADES focuses on the boilingwater reactors involved in the accident inJapan which “are made of the same materials, but in different proportions. We think
we will find more metal in Fukushima
Daiichi debris,” Barrachin concludes.
Examining the debris will provide useful
information to design the robots intended
to recover it and the protection needed toevacuate it.
Analysis of the composition of the corium
collected, resulting from the core melt‑
down, will provide information on what
happened in March 2011.
With this information and the ASTEC
software developed for the simulation ofa reactor core meltdown, it will be possible
to gain a better understanding of what
happened in the accident (see Webmag). n
1.	Mitigation of releases to the environment
in the event of a nuclear accident,with the participation of EDF.
2.	Experimental platform for fission productchemistry and radiochemistry.
3.	Experimental research platform on purificationof radioactive effluents.
4.	Preparatory Study on Analysis of Fuel Debris,project under the auspices of the OECD,
started in 2017.
5.	International project (1998‑2010)
irsn.fr/phebusEN
Find out more:

MIRE project irsn.fr/Mire-EN
PreADES program irsn.fr/news-20180522

Page 13 - Repères No. 48 - March 2021

© Célia Goumard/IRSN Media Library© Contributors to OpenStreatMap

EMERGENCY

Relocation perimeter

Estimation of post-accident zoning during an exercise
in Chinon (Indre-et-Loire department) in December 2020.

IRSN’s Emergency Center (Centre technique de crise/CTC),
located in Fontenay-aux-Roses (Hauts-de-Seine department),
was mobilized for a national drill.

Emergency management and recovery

Defining new zoning

Implementing consumption bans starting from the emergency phase, improving calculation
tools that predict the atmospheric dispersion of contaminants... Emergency management
is changing, drawing on the lessons learned from Fukushima Daiichi. The goal: better protect
the population in the event of radioactive releases.

“We are at a turning point,”
Philippe Dubiau, Executive
Director for emergency pre‑paredness and response at IRSN affirmed
as he described the development of the
post-accident (PA) doctrine developed by
the CODIRPA1 chaired by the French
Nuclear Safety Authority (ASN). And withgood reason, since the new version
expected in 2021 will finally incorporate

feedback from Fukushima Daiichi. In thisupdated version, an important provision
has been added to better protect the pop‑
ulation. Some measures hitherto reserved
for the post-accident phase will be taken
earlier. Making recommendations on what
is and is not possible to consume cannot
wait until the releases have stopped, as has
been the case up to now.
The 2012 doctrine was published too early
on to assimilate the les‑sons learned from man‑aging the accident inJapan. In it, releases are
assumed to continue for
one to three days, as wasThree questions
case for Chernobyl.
for Patricia Dupuy the
However, in Japan, theyon IRSN’slasted for several weeks.
Emergency Center “When releases continue
irsn.fr/R48-EN
for a long period of time,
action needs to be taken

WEBMAGAZINE

READ

Page 14 - Repères No. 48 - March 2021

immediately. Otherwise, it poses population
exposure problems–linked to the consumption of contaminated foodstuffs–and economic issues relating to the conditions ofmarketing products,” explained Damien
Didier, specialist in modeling radioactivity
transfers in the environment.
At IRSN, this difference entails operationalchanges, as from the emergency phase, its
experts must assess foodstuff consumption
and marketing issues.

Changes to zoning

Zoning is based on modeling future pop‑
ulation exposure and food chain contam‑
ination. The radiological emergency
management platform 2, C 3X, is used,which “combines data from Météo France,
the national meteorological service, andthat of radioactive releases. It simulates
the transport of contamination in theatmosphere and assesses the doses likely

EMERGENCY

Optimized models

Fukushima Daiichi required the C3X plat‑
form’s modeling capabilities to be expanded.
“This accident shook the scientific and operational community. We have learned from
this,” said Denis Quélo. “We realized that
our atmospheric dispersion models wereinsufficient for an initial approach,” heexplained. In 2011, they did not include
dispersion calculations over long distances;priority was given to the first ten, twenty,
or thirty kilometers. However, for this
accident, it was crucial to be able to covergreater distances.
Developed in research and development,
ldX software overcomes this shortcoming
and has been included in the C3X platform.
Calculation tools are constantly improved.
“We now take better account of the phenomenon of scavenging 4 of aerosol particles
by rain to predict soil contamination. Ourmodels also integrate fogwater deposition,”
described modeler Arnaud Quérel.

Measuring more quickly
and accurately

In metrology, too, practices are adapting
and mobile resources being developed.
The Ulysse airborne measurement system,comprising detection devices on board
helicopters or aircraft, was launched inlate 2011. It provides an initial overall
assessment of radioactive fallout in theevent of an emergency.
Faster protocols are also emerging in labo‑
ratories to allow the analysis of the hazard‑
ous nature of the samples taken from theenvironment to guide decisions. “After
Fukushima Daiichi, we realized that we were
too slow for the needs of emergency manage-

TECHNICAL TOOLS
MethodInverse modeling improves
understanding of releases“Inverse modeling [IM] combines
measurements made in the environment
with atmospheric dispersion models. It helps
to accurately deduce a source term [ST], namely
the composition of a radioactive release froma facility and its chronology,” summarized Olivier
Saunier, specialist in atmospheric dispersion.
IRSN was the first to implement an IM method
based on gamma dose rate measurements
to estimate the Fukushima Daiichi’s source
term in 2013*.
How was IM developed? In 2011, this wasa research project. When the accident
in Japan occurred, the atmospheric dispersion
model used failed to accurately reconstruct
the contamination. “At the time, this model
required input data on the weather, to simulate
March 15, 2011 6 a.m.

Activity
�Bq/m3�

the cloud’s path, and the ST,” Saunier explained.
These were not sufficiently accurate, as
the results did not correspond to the field surveys
that poured in during the accident.
To improve knowledge of releases and help
assess environmental and health consequences,
experts use dose rate measurements basedon networks of beacons. These are dense
and provide fine temporal resolution—
10 to 60 minutes in the case of Fukushima Daiichi.
Validated during the accident in Japan,
IM is now useful in the event of abnormal
detection of radionuclides.
In 2020, it helped assess releases from forest fires
in the Chernobyl power plant exclusion zone.
*O. Saunier et al. Atmos. Chem. Phys., 2013.

March 20, 2011 8 p.m.

© BMCA/SESUC/PSE-SANTÉ/IRSN

to be received by humans,” explained Denis
Quélo, specialist in atmospheric disper‑sion models.
Zoning 3 contours are also changing.
In 2012, there were three zones: a relocation
perimeter, a population protection zone
and an enhanced territorial surveillancezone.
The doctrine now defines two perimeters:a relocation zone defined according to
the ambient radioactivity and a dietary
restriction zone which connotes the nonconsumption of fresh produce as well as
monitoring and management of agricultural
production, livestock farming, andconsumer goods. “Rather than defining an
overall zone, the plan works by sector,”
Dubiau added.

Simulated cesium-137 plume, obtained from the source term reconstructed by inverse modeling,
during the two main contamination events in March 2011.

ment,” said Béatrice Boulet, Radiochemist.
“You can’t wait six weeks before determining
the presence of strontium 90, plutonium,or something else. We have developed protocols that produce an answer in a day,” sheadded. IRSN is also working on other topics(see p. 16).

Special Intervention Plans

Following interministerial discussions on
feedback from Fukushima Daiichi, theFrench Prime Minister adopted the new
doctrine relating to Special Intervention
Plans (PPI) in 2016. By 2022, it should
include the French national response planfor major nuclear or radiological accidents.
This large-scale plan emerged in 2014, after
the accident in Japan, because the publicauthorities wished to improve the safetyof the population in the event of accidents
of exceptional magnitude. “PPIs define
an organization that allows to be ready toact in the event of an accident,” summarizedErik Leclerc, specialist in the managementof emergency s­ ituations. Coordinated by
the prefects at the French department level,
they provide for three actions to protect
the population: sheltering in place andcounseling, stable iodine administration,and evacuation. The latter is triggered when
exposure forecasts for the population
exceed 50 mSv in effective dose for thewhole body. “Fukushima Daiichi haschanged these measures.”Among the accident scenarios considered,
the possibility of a rapid release was taken
into account in the 2000s with the establish‑
ment of an automatic shelter-in-place radius,
Page 15 - Repères No. 48 - March 2021

*SPECIAL INTERVENTION PLAN

for example, 2 km around power plants.
These plans are now supplemented by thepossibility of immediate evacuation within
a 5 km radius if the rapid releases are longterm, as was the case for Fukushima Daiichi.
The disaster in Japan also showed that the
impact of an accident can extend overdozens of kilometers. PPIs therefore
increased their perimeter from 10 to 20 km
around the power plant, within whichstable iodine tablets are distributed inadvance (see p. 18) and public awarenesscampaigns are carried out. n
1.	Steering committee for managing
the post‑accident phase of a nuclear accident
or radiological emergency situation/
Comité directeur pour la gestion de la phasepost-accidentelle.
2.	Calculation of consequences and mapping.
3.	Predictive modeling of future exposureof the population to ambient radioactivity
in inhabited areas and of food chain
contamination due to radioactive deposits.
4.	During precipitation, raindrops carryaway the radioactivity collected during
cloud formation.
Find out more:

National doctrine for nuclear post-accident
management, October 2012www.french-nuclear-safety.fr => Information =>News releases => National doctrine for nuclear
post-accident management

WEBMAGAZINE
READ
Post-accident
management
shouldinclude social
consequences
irsn.fr/R48-EN

READ
What humanresources to callupon in extreme
situations?
irsn.fr/R48-EN

Page 16 - Repères No. 48 - March 2021

What is IRSN’s role
within the CODIRPA?

The Institute provides
technical information on many
topics. It presents accident
scenarios including releasecalculations and dose maps
used as input for reflections
on the post-accident (PA)doctrine. After Fukushima
Daiichi, it studied a serious
accident scenario withlong-term releases.
IRSN also contributes toactions carried out in favorof or in interaction withlocal stakeholders.

What are the CODIRPA’s
directions?
We need to assess whether
the population protection
doctrine, drawn up in
consideration of releases
from nuclear power plants,
is suitable for other facilities.
For example, plutonium isless irradiating than radioactive
releases from power plants
but can be highly dangerous
if ingested. Another issue isreleases into aquatic, marine,or fluvial environments.
At Fukushima Daiichi, there
were releases into the sea andconcerns about their impact.
This is a concern in France,
too, as its power plants arelocated on river banks or on
the coast.

What about remediation?
Contaminated soil
management will be dealt
with in more detail.
This involves defining
contamination reduction
strategies and remediation
recommendations forthe public authorities.
This includes managing
the waste produced.
Decontaminating soil,
for example, can involve

removing 10 or 20 centimetersof topsoil. Dependingon the desired clean-up target
levels, the costs and volumesof waste generated may
significantly differ.
We assess the pros andcons of the various options.
It is essential that the
population and elected
representatives be more
involved in these issues.
The resilience of contaminatedareas relies on upstream
preparation and stakeholder
involvement in the decisionmaking process regarding
the measures to be put
in place.

© Noak/Le Bar Floréal/IRSN Media Library

PPI* EXTENDED FROM
10 TO 20 KM AROUNDFRENCH NUCLEAR
POWER PLANTS

3 questions for...
Philippe Dubiau
Executive Director for emergency
preparedness and response

ECONOMY

Cost calculation has improvedL

oss of business, devaluation of
housing, health-related costs, andcontamination remediation expenses,
these are four modules that will be
added to ARPAGON in 2021. This
software program assesses the economic
consequences of a nuclear accident.
It was created in 2012 by the IRSN’s
Nuclear Risk Economics Laboratory (LERN).
The feedback from 2011 helped identify
several improvements in methods
and tools for calculating the economic
costs of an accident. The Instituteprovides support in the event of an
emergency. Its objective is “to be able
to offer the public authorities, at the endof the emergency phase, technicaloptions for managing contaminated areas,
including cost assessments,” explained
Ludivine Pascucci-Cahen, Economist
at IRSN. In addition, the costs ofaccidents are compared with the costof preventing them.

Another new feature: under the AMORAD
research program (improving models
used to predict dispersion and assess theimpact of radionuclides on the environment)(see p. 20), ARPAGON will estimate
the losses of forest and aquatic resources.
© Noak/Le Bar Floréal/IRSN Media Library© Ljcom.net/distribution-iode.com

EMERGENCY

Ludivine Pascucci-Cahenstudies the economic
consequences of accidents.

EMERGENCY
MEANS AND PROVISIONS
What means are deployed to map a contaminated area?
To protect the population in the event of a nuclear accident with releases, the priority is to quickly and reliably identify
the affected areas requiring protection measures, in order to advise the authorities. IRSN’s strategy is based on
the successive deployment of measurement resources in the field, in constant contact with its Emergency Center (CTC)
in Hauts-de-Seine department. Some means have been developed as a result of the Fukushima Daiichi accident.

1 Aircraft: rough out
the impacted area

5 Staff in the field and• 4 gamma detectors

laboratory vehicle:
characterize, from theground, the contaminatedzones that are invisible
from the air• 40 km x 40 km area,
6-hour overflight of a wide
area around the plant• Speed 300 kmph,
height 300 m• Sampling (water, grass,soil, agricultural production,etc.)• Analysis in laboratory
vehicles2 Helicopter:

identify the relocation
perimeter!

• 4 gamma detectors• 10 km x 10 km area
• Speed 150 kmph,
height 50-300 m• Measurement of groundcontamination levels byin situ gamma spectrometry

3 Vehicles:

4 Aircraft and helicopter:

confirm the relocation
perimeter

identify contaminatedzones from the air• In situ gamma spectrometry• 4 gamma detectors• Measures at the edgeof the relocation perimeterto clear villages• Overflight of a wide area
following the directionof releases• Manual or quad measurements
in inaccessible zones• Guided by the CTC
according to modelingD3 D4 D5

D1 D2

Two types of zones impacted by protection measures
By comparing the measurements and the results obtained
from modeling, IRSN defines the zoning.
Relocation perimeter (PE)The population is informed on a daily basis
The authorities, informed by IRSN, decide on protection measures: sheltering in place, relocation of the population,
dietary restrictions (self-consumption, gathering, hunting, fishing, etc.) and control of products before sale.
End of releases
D0

D1

Relocation perimeter map
D2

D1-D2: establishing
the relocation perimeterin support of theprefect’s decision.

D3

D4

Dietary restriction zone

Map of the control
and restriction zones
D5
Establishing zones
where control and foodrestrictions are in place,in support of the prefect’s
decision.

© Art Presse/ABG Communication/IRSN Media Library/Repères magazine

The IRSN Emergency Center (CTC) in constant liaison
IRSN’s CTC is based in Fontenay-aux-Roses (Hauts-de-Seine
department).
• It provides technical information on the accident(type of release, approximate quantity, weather conditions, etc.).
• It uses the measurements taken in the field and establishesa diagnosis of the effective doses in the impacted zone
in the form of a map to refine modeling.
• It provides the authorities with the information required
to protect the population.

Page 17 - Repères No. 48 - March 2021

© Philippe Dureuil/IRSN Media Library© Philippe Dureuil/IRSN Media Library

HEALTHFollowing a nuclear accident, people
may have ingested or inhaledradioelements. Whole body counting
measures internal contamination.

An IRSN Emergency Response Officer reassures a person and collects
information while screening for internal contamination with X- andgamma-emitting radionuclides.

Population protection

What progress has been madein ten years?
Preventive iodine intake, health monitoring... Radiation protection measures in the eventof a nuclear accident are implemented since 2011. In addition, one major recommendation
for health surveillance is that national cancer registries be maintained for all categoriesof the population.

Preventive intake of stable iodine, inthe form of potassium iodine (KI), is
one of the population protection strat‑egies used during the emergency phase of
a nuclear threat or accident with releases.
By saturating the thyroid with stableiodine, this countermeasure prevents thegland from uptake and fixation of radio‑
active iodine, and limits the occurrenceof thyroid cancer.
Its implementation in France has been
recommended since 1997. As soon as there
is an alert, an adult should take two 65 mg
tablets. Intake may be repeated once if
exposure exceeds 24 hours. The dosage forchildren is adapted according to their age.
Fukushima Daiichi showed that this meas‑
ure is insufficient for people awaiting evac‑
uation or who cannot be evacuated in theevent of prolonged or repeated releases. In
2014, the Institute initiated the PRIODAC1
project, funded by the French Investments
for the Future Program (PIA). “We needed
Page 18 - Repères No. 48 - March 2021

to find a KI dosage allowing repeated intake
and verify its effectiveness and safety,”
explained Marc Benderitter who specializes
in radiopathology. He has been in chargeof this major project, which includes pre‑clinical studies of pharmacokinetics, ther‑apeutic effectiveness, and toxicology.
Rat pups model newborns, while female
rats in gestation represent pregnant women,
and young, adult, and aged rats cover the
rest of the population. Preclinical regula‑tory toxicology studies complete the pro‑gram. PRIODAC aims to change the KI
dosage for repeated intake by all categoriesof the population and to modify the mar‑keting authorization by 2022.

Questioning screening practices

How can the risk of thyroid cancer beassessed in the event of releases? Japan
opted for systematic screening. “The World
Health Organization (WHO) now advises
against this type of monitoring,2” reported

Dominique Laurier, expert in the biologicaleffects of radiation. This recommendation
follows on from long-term feedback.
After the Chernobyl accident, studies
showed an increase in thyroid cancer, espe‑
cially in young people exposed to releases.
In 2011, Japan wanted to reassure its pop‑
ulation. Without precise estimates of theextent of the accident, that summer it
launched a vast screening campaign using
ultrasound scanning, a very sensitive tech‑nique. Three hundred thousand boys andgirls were screened. The fifth screening
campaign is currently underway. What
are the results? For every thyroid nodule
discovered, a biopsy is taken. In case of
malignancy, the gland is either fully or
partially removed. In ten years, two hun‑dred surgical procedures have been carriedout. Is this world record due to the accident
or a result of this uncommon strategy ofoperating even before symptoms appear,
criticized more and more? “This screening

HEALTH

1.	Repeated prophylaxis with stable iodine
in an accident situation/Prophylaxie répétéepar l’iode stable en situation accidentelle.
2.	WHO (2018), Thyroid Health Monitoring
after Nuclear Accidents.
Find out more:

PRIODAC irsn.fr/priodac-EN

INTERNATIONAL
Shamisen project

In favor of a radiation protection culture© Kyodo/MAXPPP

gives the impression that there are morecases and that they are due to radioactivity.
The occurrence of cancer is actually stable.
Most of these nodules are not radiation-induced,” explained Laurier.
This proactive choice is gradually revealing
its flaws. Screening leads to overdiagnosis,
causes worry, causes more ablation, andexposes people to unnecessary hormone
therapy. Ultimately, there is no clinicalbenefit; therefore, the experts issued newrecommendations. There is now consensus
on waiting and monitoring the tumor
nodule without operating on it. Japan isadopting this strategy for its final screening
campaigns. Japan’s experience is instruc‑tive. In 2011, the Fukushima prefecture
did not have a cancer registry. If it had had
one, it could have used it to identify a pos‑sible resurgence of thyroid cancer.
France has a national childhood cancer
registry but does not cover the entire
country for adults. Such registries helpto evaluate the health risk and develop
dialogue with civil society. The Shamisen
project recommends implementing them(see opposite). n

The Shamisen project recommends developing a radiation protection culture.
In Tokyo, local authorities received training on iodine tablet distribution to residents in 2014.

T

wenty-eight recommendations to improvedosimetric, health, and epidemiologicalsurveillance after a nuclear accident are thetakeaways from the European Shamisen project
initiated in 2015 that included IRSN as aparticipant. One principle conditions all the others:
to do more good than harm. Health surveillancemust respect the independence and dignityof populations. The project encourages trainingof personnel—medical or not—according
to the different phases of an accident, developing
evacuation and shelter-in-place protocols,and supporting populations who desire to take theirown measurements of radioactivity
in the environment, in food, etc. The authors
recommend developing, with the help of experts,
mobile applications and easy-to-use dosimetry
devices. Nineteen European and Japanese partners
are involved in Shamisen, representing aroundsixty specialists in radiation protection, dosimetry,sociology, medicine, psychology, and more.
Find out more:

Shamisen irsn.fr/Shamisen-EN

IN A NUTSHELL
Internal contamination: measuring equipment that adapts to everybody

Versatile
Portik works in all positions,unlike boxers that require theperson to be seated.

The Portik detector
is transportable
Disassembled for transport, it
can be ready in just a few hours
to round out the array of mobile
resources already on site: lab
trucks and light whole bodyradiometry vehicles (boxers).
* IRSN patent FR3050281

gamma
rays

thyroid

Portik is equippedwith telescopic legs
to adjust it to eachindividual.

Freestanding
Combined with alaptop computer, it canbe used without anexternal power source.

USB cable

Spectrometry
software acquires
and analyzes
gamma spectra.
lungs

Rapid triage
Set up as close as possible
to operational emergency
centers to facilitate prompt
treatment of contaminatedindividuals, who are placed
in private rooms or a tent.

© Art Presse/ABG Communication/IRSN Media Library/Repères magazine

The Portik detector is suitable for both a child and a wheelchair user and measures internal contamination.
This portable* whole body counter can be deployed quickly to a disaster area so that people requiring medical attention are
identified without delay.

Page 19 - Repères No. 48 - March 2021

ENVIRONMENT
Environmental contamination

Models are progressingHow can the medium- and long-term
consequences of a radioactive releaseon humans and the environment beassessed? They can be assessed by optimiz‑ing the models that predict their dispersion
and estimate their dosimetric impact.
Coordinated by IRSN, the AMORAD1
project is developing three lines of research:
the cesium2 cycle in forests, erosion-runoff
flows from watersheds to rivers and thento the sea, and the impact of releases on
the marine environment (water, sediments,organisms).

© PRP-ENV/SESURE/LERCM/IRSN Media Library

When an accident occurs, forests, marine and agricultural environments are contaminated.
The long-term effects of this contamination are being studied.
In ten years, research has provided knowledge on the transfer of radionuclides
to ecosystems, the quantification of uncertainties in models, etc.

Cesium transfer in forest
ecosystems

Page 20 - Repères No. 48 - March 2021

IRSN researcher Sabine Charmasson takes samples and cores on the coast and at sea to assess
the contamination of water and marine sediments along the coast, north of the Fukushima Daiichi plant.

© PSE-ENV/SEREN/LEREN/IRSN

As a vulnerable biotope, forests capture more
atmospheric contamination than agricul‑
tural and urban environments. They thencontaminate other environments, via ero‑sion, runoff, fires, etc. It is therefore essential
to predict the evolution of contaminationin the various compartments—soil, tree andforest understory. In 2011, the existing
empirical model proved insufficient, as it
had not been well tested, due to the lack ofdata immediately following Chernobyl.
With AMORAD, cesium transfer is spec‑
ified after validation of the new TREE4
model on data from forty Japanese forestsites. “TREE4 calculates the levels of contamination and predicts their short- tolong-term evolution, from several months
to thirty years,” explained Marc-André
Gonze, terrestrial ecosystem modeling andrisk assessment expert.
The tool makes it possible to estimate, in
microsievert per hour (μSv/h), how theresulting external dose rates evolve over timein a forest environment and to assess theefficiency of decontamination efforts likeremoving part of the soil, tree felling, etc.
“How quickly will we be able to restart forestry? How can we shorten this time?” Gonze
comments. He goes on to say, “If a nuclear
accident were to occur in France, these

Sampling campaign in French forests as part of Dina
Okhrimchuk’s thesis. Pierre Hurtevent, Engineer, takes
samples from the roots of a beech tree.

ENVIRONMENTTaking an ecosystem-based
approachMarine models also revealed shortcomings
in 2011. Improvements must be made inradionuclide dissemination predictions
and simulations of transfers to fish andshellfish consumed by humans. Afterten years of research, dispersion modeling,based on marine current calculations, isoperational and ready to be used by the
IRSN Emergency Center (see Webmag).
Another model, regarding transfer to bio‑
logical species, has also been perfected.
“In the event of an emergency, the tools must
make it possible to quickly issue recommendations: bans on fishing, consumption, etc.
Based on the estimated levels in the water,
they assess the radionuclide concentrations
expected in fish,” explained Céline Duffa,
specialist in radionuclide transfer inmarine systems. “The accident in Japanshows that species contamination varies
according to habitat and diet. Benthic
organisms—living on the seabed, such as
the olive flounder—are the most affected.
Their diet is linked to sediment, which traps
radioactivity,” she added.
AMORAD offers a new ecosystem-based
approach and considers transfers acrossthe entire trophic chain. It considers therelationships between various organisms
according to their eating habits.

Quantify uncertainties

In the agricultural field, post-Chernobyl
models on market gardening (cabbage,
spinach, etc.), field crops, and livestock
products (milk, meat, etc.) were alreadypresent in operational tools like Symbiose4,
and these remain valid. The lack of a modelfor orchard fruit (apples, cherries, etc.) has
been remedied thanks to data acquiredby the Japanese authorities.
The Fukushima Daiichi accident high‑lighted the need to know how to quantify
the level of accuracy of forecasts andtheir uncertainties. “Post-accident zoning[see p. 14] is defined by comparing predictedvalues with a benchmark. For safe zoning,
we seek to quantify the uncertainties ofmodels,” concluded Marie Simon-Cornu,
specialist in risk assessment. n

EUROPE
Territories projectManaging the post-accident phaseat the local level© Département Girondec­ alculations would help decision making.”
The model, parameterized with theJapanese dataset, needs to be transposedto the French context, according to thenature of its vegetation, soil, and climate.
A thesis is currently exploring this issue3.

The local nuclear information commission (CLIN) of the Gironde department hosted a delegationof Japanese and Belarusian stakeholders as part of the Territories program in December 2018.

H

ow can land affected by long-term
contamination be managed? This question isat the heart of the Territories project led by IRSN.
“We make thirteen recommendations on how
to model the long-term evolution of contamination,
include uncertainty in decision-making, develop
co-expertise in radiation monitoring, and so forth.
Citizens, experts, and institutions all work together
on this project,” said Marie Simon-Cornu,
coordinator of the project involving eleven
European partners.
Ties with Japan are strong. In late 2018, during
a workshop with Le Blayais (Gironde department)
local nuclear information commission (CLIN),
several Japanese stakeholders shared their

1.	Improvement of models for predicting
the dispersion and assessing the impact
of radionuclides in the environment.
2.	Radioactive cesium isotopes are among
the major radioelements in accidental releases
from power plants.
3.	Study of the long-term behavior of atmosphericfallout of cesium-137 in French forests,
Dina Okhrimchuk, in progress.
4.	Platform for simulating the transfer ofradionuclides to ecosystems and calculating
the dosimetric impact on humans.

experience with wine makers. The testimonialfrom a persimmon producer was particularly
memorable. “He explained how the trees and fields
were cleaned and how each piece of fruit wasmonitored for radiation,” recalled Xavier Paulmaz,
Project Manager for the CLIN. A fictitious
accident was envisaged, and consideration wasgiven to the following questions: How could
business be revived? Should the vines be pulled up?
What financial support would be available?
Since then, a working group has made local
stakeholders aware of these issues.
Find out more:
Territories.eu

BIBLIOGRAPHY
Gonze M.-A. et al. (2021a) Sci. Total Environ.
Gonze M.-A. et al. (2021b) Sci. Total Environ.
(submitted)
Gonze M.-A. and Calmon P. (2017) Sci. Total
Environ.

Find out more:

AMORAD
irsn.fr/Amorad-EN

WEBMAGAZINEREAD

A mapping tool
to help local
stakeholders
prepareirsn.fr/R48-EN
Page 21 - Repères No. 48 - March 2021

IRSN

The Institute has monitored developments in Japan since
March 11, 2011. It has deployed its multi-disciplinary expertiseto assist in guiding national and international discussions
on safety, and supports civil society by responding to theirquestions and concerns.
2011: Handling the emergency
in Japan and France

From March 11, IRSN deployed its
Emergency Center (CTC) based in the
Hauts-de-Seine department (see Webmag).
Expert Olivier Isnard accompanied theFrench civil security rescue mission sec‑
onded to Japan.
Through dose rate measurements, heensured that there was no radiological risk
for the team members. “The Institutesupported us before, during, and on our
return from our clearance mission,” attested
Bertrand Domeneghetti, lieutenantcolonel of the fire brigade at the General
Directorate for Civil Protection andEmergency Management, in 2012. Witharound twenty rescuers, IRSN conducted
a radiological risk assessment at the Lycée
Français in Tokyo and then informed
parents and staff.
The expert stayed in Japan for five weeks,
analyzing the situation and the stakes.
A daily news bulletin was published on
the embassy’s website. At the Pompidou
Center’s request, he screened the 170 works
exhibited at the National Art Center,
Tokyo, for contamination before theirreturn to France.
In France, the Vésinet Center (Yvelines
department) deployed specialists in radi‑
ological measurements. They carried out
whole-body counting on personnel return‑ing from Japan, from Air France andRadio France as well as Cybernetix, who
dismantled a power plant south of thedamaged one.
At the end of 2011 and then in April 2012,
the Institute took part in contamination
measurement and mapping campaigns
near Fukushima Daiichi. Its specialists
carried out in situ readings and measured
the dose rate in cars, using the Ulysse
system (see p. 17). Over 100,000 gamma
spectrometry measurement points were
read, including in the evacuated zone.
Page 22 - Repères No. 48 - March 2021nFour weeks of non-stop workat the CTC

The Institute’s CTC was very involved inhandling the accident in Japan. For fourweeks straight, its experts were constantly
at work. A force of at least 30 experts wereon hand during the day and 20 at night,
totaling 200 of the Institute’s 1,700 staff atthat time.
It’s the full breadth of IRSN’s expertise,in support of this team of experts, which
made it possible to provide estimates of
the consequences in Japan and France.
nThriving safety policies in action

In the aftermath of the accident, theInstitute got organized to respond to thePrime Minister’s request for complemen‑tary safety assessments on nuclear facilities
to examine their resistance to high-inten‑
sity loads. Karine Herviou, Safety Expert,
remembered that “although we had notfinished managing the emergency, we werealready getting organized to make a decision
as to how to manage the impact on Frenchfacilities. The request for a ‘hardened safety
core’ is the result.”nAnalysis and explanations

A few months after the accident, the FrenchHigh Committee for Transparency andInformation on Nuclear Safety (HCTISN1)
and several local information commissions(CLI) asked the Institute for an interpre‑
tation of the events that occurred at theJapanese plant. Between September 2011
and January 2012, IRSN and the French
National Association of Local Information
Committees and Commissions (ANCCLI 2)
co-organized three seminars to monitor
complementary safety assessments andpresent IRSN’s conclusions from them.
This would include introducing the hard‑
ened safety core concept which aims to
improve the safety of facilities in the eventof exceptional hazards (see p. 8).

© Antoine Devouard/IRSN Media Libraryn© Geneviève Baumont/IRSN Media Library

2011-2021: IRSN’s actions

Expert Olivier Isnard speaking at the 2011 Eurosafe forum.

IRSN© Dean Calma/IAEAIn February 2013,
IRSN measured the contamination level of aschool that was evacuated and thendecontaminated in Kawamata, Japan.

n© Olivier Seignette/Mikaël Lafontan/IRSN Media Library

Gilles Compagnat at the ANCCLI-IRSN seminaron post-Fukushima safety issues.

Ten years of monitoring...

Since 2011, the Institute has been involved
in monitoring developments in the situa‑tion in Japan, ranging from emergency
management, impacts on the environmentand health to facility condition, disman‑tling, social consequences, and so on.
Eight annual news bulletins have been
published on irsn.fr. Locally, IRSN is
involved in several technical projects suchas dismantling, as well as community­projects, such as the Fukushima Dialogue
initiative (see p. 6).
n2018 saw the renewal of the IRSN and IAEA
cooperation agreement. Jean‑Christophe Niel, theInstitute’s Director General (left), and Juan Carlos
Lentijo, IAEA Deputy Director General and Head of the
Department of Nuclear Safety and Security (right).

An international presence

The Institute participated in the peer reviewof the conclusions of European stress tests,
an international action similar to France’s
complementary safety assessments. It also
participated in several IAEA 3 activities.
In 2013, a request was made to IRSN toorganize a seminar in Japan on serious
accidents, during which it presented theFrench hardened safety core initiative. It
took part in ETSON 4 network safety
discussions.
“We are present in all the major international organizations to share our experienceon the accident, the lessons learned, andto compare safety improvements,” Herviou
concluded.

into place following commission member
Gilles Compagnat’s trip to Japan in 2014.
During his stay, he met with the former
director of the Fukushima Daini plant,
located 11 km south of the damaged facil‑
ity, where the disaster was averted.
“Employees managed to pull 9 km of electric
cables to restart the pumps. This prevented
the hydrogen from exploding,” he explained.
In 2015, CLI set up a technical commission
on organizational and human factors,
which studies all significant safety eventsfrom this perspective. n

1.	Haut Comité pour la transparence
et l’information sur la sécurité nucléaire.
2.	A ssociation nationale des comitéset commissions locales d’information.
3.	International Atomic Energy Agency.
4.	European Technical Safety Organization
Network.
5. Plan particulier d’intervention.

Find out more:

Involvement: Understanding Fukushima
in France irsn.fr/fuku-lessons
Complementary safety assessments:
The condition of nuclear facilities
post-Fukushima irsn.fr/ECS-EN
IRSN briefs on the Fukushima Daiichi
accident irsn.fr/fukushima-EN
OpenRadiation openradiation.org/en

Vigilant local commissions

Since the Fukushima Daiichi accident, theGolfech (Tarn-et-Garonne department)
CLI’s actions have been inspired by the
feedback from it.
When the special intervention plans (PPI 5)
were applied to a radius of 20 km aroundFrench power plants, an awareness cam‑paign was organized, targeting 130,000
additional residents. Weekly ambient radi‑
oactivity measurements are carried out
using the OpenRadiation sensor suppliedby IRSN. This tool, connected to a smart‑phone, allows volunteer citizens and com‑munities to share these measurements ona website thereby contributing to improving
knowledge on the local environment.
Regarding safety, “commission members
have been visiting the Golfech power plantsince 2016 to monitor the deployment of thehardened safety core,” (see p. 8) reported
Véronique Auguste, Project Manager forthis CLI. This level of vigilance was put© Susanna Lööf/IAEAn

Two IRSN experts measure radioactivity during
an IAEA exercise near Fukushima Daiichi.

Page 23 - Repères No. 48 - March 2021

Research projects, safety assessment reports,
environmental monitoring…

Credit: iStock/Farknot_Architect…follow us online

We hope that you have enjoyed reading this special issue of Repèresdevoted entirely to the Fukushima accident and its aftermath.
Would you like to learn more about managing severe accidents, thecomplementary safety assessments performed in France, the Fukushima
Dialogue initiative and other topics related to nuclear safety and radiation
protection research?

IRSN has more for you online. Visit
www.irsn.fr/EN/

INSTITUT DE RADIOPROTECTION
ET DE SÛRETÉ NUCLÉAIRE