REPORT

Methodology used in IRSN
nuclear accident cost estimatesin France

PRP-CRI/SESUC/2014-132

Radiation Protection Division
Emergency Response Organization Department

Direction de la sûreté des réacteurs

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ABSTRACTThis report describes the methodology used by IRSN to estimate the cost of potential nuclear accidents inFrance. It concerns possible accidents involving pressurized water reactors leading to radioactive releases
in the environment. These accidents have been grouped in two accident families called: severe accidents
and major accidents. Two model scenarios have been selected to represent each of these families.
The report discusses the general methodology of nuclear accident cost estimation. The crucial point is that
all cost should be considered: if not, the cost is underestimated which can lead to negative consequences
for the value attributed to safety and for crisis preparation. As a result, the overall cost comprises many
components: the most well-known is offsite radiological costs, but there are many others. The proposed
estimates have thus required using a diversity of methods which are described in this report.
Figures are presented at the end of this report. Among other things, they show that purely radiologicalcosts only represent a non-dominant part of foreseeable economic consequences.

KEY WORDS
Severe accidents, accident costs, methodology

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Table of contents
1. Historical overview of IRSN studies

9

2. Presenting global results

11

2.1. The nature of global accident costs figures11

2.2. Global figures suggest a picture of the different components of a nuclear crisis

12

2.3. Global figures offer a basis for public decisions concerning safety

13

3. Model accidents and associated radioactive releases

15

3.1. Range of accidents considered in IRSN PSA2 studies

15

3.2. Releases of aerosols by accident families

16

3.3. Model accidents intended to represent accident families

17

4. Cost estimation methodology

194.1. The “consequences” approach

19

4.2. The economic approach

21

4.2.1. Listing all costs

23

4.2.2. The need to estimate corresponding costs

23

4.2.3. For each identified effect, estimate all costs

24

4.2.4. Breaking down a cost into components

26

4.3. The cost items

27

4.4. Radiological and economic costs

28

4.5. Costs are estimated from the point of view of France

30

4.6. “Median” costs

30

4.7. Future progress of research on accident costs

31

5. Modeling radiological consequences

33

5.1. The computer chain

33

5.2. Climatic data

34

6. Costs related to contaminated territories

35

6.1. Two categories of contaminated territories

35

6.2. Unit costs of exclusion zones

35

6.3. Unit costs of other contaminated territories

36

6.4. The extent of contaminated areas37

6.4.1. The severe accident

37

6.4.2. The major accident

38

7. Offsite radiological costs

39

7.1. The cost of classic consequences

39

7.2. Psychological costs

41

7.3. Relocation costs

43

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8. Image costs

45

8.1. Agricultural image effect45

8.2. Impact on tourism

46

8.3. Industrial image effect47

9. Impact on the cost of electricity production

49

9.1. Effect of a major accident on the French fleet of reactors

49

9.2. Fleet effect after a severe accident

51

9.3 On-site costs

51

10. Synthesis of results and prospects

5310.1. Synthesis of results

53

10.2. Prospects

54

Appendix 1. The DCH accident scenario

57

Appendix 2. The Cosyma dispersion model

59

Appendix 3. The C3X platform

61

Table of legends
Table 1: 2007 estimates (median values in billion euros) .................................................................... 10
Table 2: Releases and accidents in the IRSN PSA2............................................................................. 15
Table 3: Five main components, 14 detailed cost items ..................................................................... 27
Table 4: Euro equivalents of annual public aid in Belarus.................................................................... 36
Table 5: Cost of contaminated territories for a major accident (billion euros) ........................................... 38
Table 6: Health and agricultural costs of the severe accident .............................................................. 40
Table 7: Health and agricultural costs of the major accident ............................................................... 41
Table 8: Agricultural image cost (billion euros) ............................................................................... 46
Table 9: Tourism image cost (billion euros) .................................................................................... 47
Table 10: Industrial image cost (billion euros)................................................................................. 48
Table 11: Estimation of accident costs in France (billion euros) ............................................................ 53
Figure 1: Accident families and aerosol releases for 900 MWe reactors ................................................... 17
Figure 2: The radiological consequences approach ........................................................................... 21
Figure 3: The economic approach ............................................................................................... 22
Figure 4: Differences between the consequences approach and the economic approach ............................... 22
Figure 5: All the impacts of an accident should be estimated............................................................... 24
Figure 6: Estimating a cost item ................................................................................................. 25
Figure 7: Radiological costs and economic costs .............................................................................. 28
Figure A8: Scheme of a Gaussian puff dispersion model...................................................................... 64

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1. HISTORICAL OVERVIEW OF IRSN STUDIESIn 2005, the French nuclear safety authority requested IRSN to appraise a cost-benefit tool proposed by the utility,
Électricité de France (EDF). With decennial visits in mind1, EDF aimed at ranking by decreasing efficiency thesafety modifications under consideration by experts. The objective was to ensure the best safety performance foreach euro invested in safety.
As a first step, S3 type modifications and S1 type modifications were distinguished. Indeed, according to EDF, allsafety modifications could approximately be allocated to these two categories:
S3 type modifications are essentially capable of reducing the probability of S3 type accidents. In theconventional S3 accident scenario, the core of the reactor melts; it is impossible to control this core melt
and avoid radioactive releases (contrary to the Three Mile Island accident, USA, 1979); operators are led
to release the pressure which has accumulated inside the confinement in order to safeguard it. Thisventing is a controlled operation, releases pass through a metallic filter and a sand filter designed to thiseffect which significantly reduce the quantity of released radioactivity. The venting is performed 24 to 48
hours after the onset of the core melt which leaves time to evacuate persons which could be most
exposed.



S1 type modifications are essentially aimed at reducing the probability of S1 type accidents. This scenario
is considered to be an upper bound, i.e. the worst possible case on a French reactor; at one time it wasconceived as the release of 100% of the core inventory, but given the very unrealistic character of thishypothesis, the S1 scenario considered here implies releasing one third of the activity of the core2 — avery high proportion.

In practice, all possible core melt accidents followed by releases fall between S3 and S1, S3 being a lower boundand S1 an upper bound (see table 1 hereafter).
In each of these two categories of safety modifications, safety gains were measured by the reduction they
achieved in the probability of the said accidents, viz. dp3 and dp1. The safety-efficiency indices proposed by EDF
were:
ௗ௣య
௖

and

ௗ௣భ
௖

where c is the cost of the safety modification.

Modifications belonging to two different categories were compared by considering accident costs. Safety-efficiency
indices were then reformulated as:
ௌయௗ௣య
௖

and

ௌభௗ௣భ
௖

where S3 and S1 were the costs of the corresponding accidents.

IRSN then undertook estimating the cost of these accidents. The result of this work is summarized in table 1
hereafter.

1

For the third decennial visit on 900 MWe reactors.

2

Conventional scenario, release of all rare gases and of 33% of the remainder of the core.

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The cost of accidents S3 and S1 was estimated taking into account all identified consequences whether theycorresponded to direct radiological contamination or to economic and social consequences less directly material innature such as, for example, retail stores refusing to commercialize foodstuffs with low levels of contamination or
consumers simply boycotting them. In this way, these estimates innovated compared to the great majority ofprevious publications3 by taking into consideration, alongside radiological costs, other economic costs which arebound to materialize (see section 4 below).
These estimates have shown that S3 and S1 are of different natures to such an extent that they should not becompared on the sole basis of the ratio of their costs, S3 type accidents featuring relatively mild radiologicalconsequences and significant economic costs whereas S1 type accidents would confront the country to aradiological crisis of major dimensions.
Studies have been continued after 2007 to refine these preliminary results. In particular, the computer code used
to calculate radiological consequences was acceptable to estimate effects at short distances, but inadequate toreliably assess the long distance effects an S1 type accident can imply. On the basis of differences identified
between the conventional S3 and S1 scenarios, two accident families were distinguished: severe accidents andmajor accidents. An intermediate S3D accident materialized the limit between the two families and featured 100
times more releases in cesium 137 than the S3 and 100 times less than the upper bound S1 (the ratio between S1and S3 is indeed close to 10,000 in terms of rejected cesium 137). Model accidents for these two families were
evaluated, especially by improving knowledge of image effects4 and of effects on the production of electricity5
Table 1: 2007 estimates (median values in billion euros)

Severe Accidents

Major Accidents

S3 = 70 b€

S1 = 760 b€
Intermediate Accident
S3D = 150 b€

Source: Examen de la méthode d’analyse coût-bénéfice pour la sûreté, Rapport DSR N°157, annexe 4, Réunion du Groupe
Permanent chargé des Réacteurs nucléaires du 5 juillet 2007, available in French on the IRSN website.

3

See for example, OECD-NEA, Methodologies for Assessing the Economic Consequences of Nuclear Reactor Accidents, 2000

4

See section 8 below. In general, an image effect occurs when the public turns its back on a product because of more or lessunfounded fears which globally constitute the loss of reputation of the product.
5

See section 9 below.

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2. PRESENTING GLOBAL RESULTS
Nuclear accident costs continued to be analyzed; results tended to confirm the general results obtained in 2007:
the nature of the severe and major accidents, as well as the order of magnitude of their costs, did confirm
differences previously identified between the limit case scenarios S3 and S1. This led to global figures being
published in 2012-13. This section explains what are global results and how their implications should beunderstood.

2.1. The nature of global accident costs figures
By global figure we mean a cost which aims at being representative, at covering a large number of circumstancescharacterized by numerous parameters. These parameters can be grouped in broad families:

The source term, i.e. the composition and kinetics of the release. A radioactive release from anelectricity producing reactor contains dozens of different components, gases and particles (aerosols), themost important for our subject being cesium (cesium 134 and 137) and iodine (in gaseous or molecularform). More severe releases should take place within short episodes while more limited releases could lastfor several days6.



Climatic conditions play a determining role since the wind direction and its possible changes during thecourse of plume dispersion will determine which zones are affected and those which are sparedradioactive fallout. Precipitations may wash the plume along its route and cause larger fallout in someplaces.

The geographical location of the site influences consequences in various ways. For example, a site locatedon a sea shore should a priori entail less severe consequences because the wind can blow the plume onto
the sea with minimal consequences compared to radioactive fallout on land. This is precisely what
happened several times during the sequence of events which took place during the Fukushima accident.
Site location also matters because of the greater or lesser density of population around the site, inparticular the presence of large cities liable to be contaminated. Lastly, human activities can be more orless profitable, notably within the agricultural sector, and therefore have larger or smaller potentials forlosses.



Reactions of the general public, businesses and other economic players can aggravate or minimize theextent of losses due to a nuclear accident. These phenomena are often grouped under the term
resilience, i.e. the greater or lesser capacity to bounce back. Some observers have suggested that theresilience of French people would be lower than that of the Japanese confronted to the Fukushima
accident7; however, nothing solid substantiates such an opinion. Similarly, efficient responses from the

6

In Chernobyl, quite to the contrary, the release was very large but continued over some ten days, a scenario which seems
impossible on the present French fleet of reactors.
7« Un accident nucléaire, c'est la fin de la démocratie », Antonio Pagnotta, photojournalist, Le Monde, 10/03/2013

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authorities, in particular concerning the most prominent subjects such as the defense of agriculturalactivities, of tourism or of the existing fleet of nuclear reactors can help reduce accident costs.
The proportion of nuclear electricity and therefore the date at which the accident occurs in relation withthe demography of the fleet of nuclear reactors is also important, particularly as regards the impact of
the accident on electricity production. If electricity production is less intensely nuclear, or if thereplacement of reactors is largely on its way, consequences may be less drastic and the increase inelectricity bills of French consumers more limited.

Providing masses of results corresponding to the endless combinations of these many parameters would beparticularly unhelpful. The reader would not know what to think. For this reason, one accident was chosen withineach accident family as a model intended to represent the family and thus make it possible to understand themany possible variations within the family.
As indicated above, it was clear as early as 2007 that presenting one accident, as opposed to two as done here,
would conceal essential differences. The two accident families mentioned in section 1 have very different
characters which were deemed essential to explain. Two accident families have thus been distinguished; one setof results is given for the “severe” accidents and one for the “major” accident. Each one is intended to represent:

all possible releases within the family;

all meteorological conditions;

all relevant sites; andall possible accident dates within the lifetime of the fleet of nuclear reactors.

One therefore realizes that one specific scenario may deviate from the representative figures, and possibly
significantly so. This in no way questions the value of publishing global figures, a value which is now detailed andshould clarify why they were published.

2.2. Global figures suggest a pictureof the different components of a nuclear crisis
A global and quantified understanding of the overall picture of a nuclear crisis can provide crisis managers with an
ex-ante vision of the major issues to be addressed. For some non-specialist observers, a nuclear accident is firstand foremost a public health challenge. Cost estimates performed by IRSN show this to be inaccurate, especiallyfor severe accidents. In such a case, releases being delayed in time and filtered by appropriate devices, economic
aspects largely dominate radiological costs. Cost estimates offer a quantitative vision of the phenomenon andadvocate addressing these economic aspects at the preparation stage in accordance with their probable costs; thisallows crisis management to take the necessary steps at an early stage and thus protect citizens from having tobear costs heavier than necessary.

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2.3. Global figures offer a basis for public decisions concerning safety
Global costs for nuclear accidents also shed light on the extent of losses, i.e. on the value of safety.
Figures offered in this report exceed previous estimates which generally only consider radiological costs (seesections 4.1 à 4.4 below). With higher accident costs, the value of safety appears higher than expected previously.
The willingness to invest in the prevention of nuclear accident must then be revised upwards. All things equal,
underestimating accident costs leads to retain residual risks above the optimum. A better knowledge of accident
severity allows better adjusting the level of safety.
In addition, results show that severe and major accidents are of different natures. This should also bear on
decisions. It no longer appears feasible to address these two categories of accidents in the same fashion8. In
particular, one of the important conclusions of global figures is that the lower probability of major accidents may
not necessarily compensate for their catastrophic character. Working for safety while ignoring, because of theirextremely low probabilities, the catastrophic character of the most severe accidents would, again, imply
deviations from decisions taken with the benefit of full information.

8

In the future, it may be necessary to distinguish more than two categories of accidents.

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3. MODEL ACCIDENTS AND ASSOCIATED RADIOACTIVE RELEASES
3.1. Range of accidents considered in IRSN PSA2 studies
Considered releases are based on the PSA level II studies conducted by IRSN, i.e. the in-depth study of possible
radioactive releases from a French electricity production reactor. Cause and event trees are established startingfrom all possible internal initiators leading to 44 large accident families. Releases are identified for both the
production and shutdown states of the reactor. The following table lists these states (acronyms used by specialists
are explained below the table).
Table 2: Releases and accidents in the IRSN PSA2
Type of release

Accident family

Production
states

Shutdown
statesLimited releases

Limited fuel damagex

x

Successful in vessel reflooding; confinement is
not breachedxx

No basemat penetration 15 days after ARTx

Releases through naturalconfinement leaks
Loss of confinement
before 24 hours

Heterogeneous dilutionx

Small breach, beta mode/phase B

x

Induced SGTRx

Large breach, beta mode/phase Bxxx

Small breach, beta mode/phase DxEquipment hatch initially openx

Large breach, beta mode/phase Dx

In vessel steam explosionx

Ex vessel steam explosionx

Alpha modex

Heterogeneous dilutionsx

U5 filtered containment venting phase DxInitial SGTRx

Consequences not evaluated(STR, ATWS – PPO)x

Small breach, beta mode/phase DxCombustion/pressurization phase B

x

V-LOCA
Loss of confinement before 24
hours after ART; releases greater Small breach, beta mode/phase B
than the S3 source term
Containment ruptured by pressurization, CCB

x

x
x

x

x

x

Equipment hatch initially openx

Small breach, beta mode/phase DxLarge breach, beta mode/phase Bxx

Initial SGTR
Ex vessel steam explosion
Induced penetration leak phase Dxx

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Large breach, beta mode/phase D

Loss of confinement after 24hours after ART ; releases lower
than the S3 source termx

Direct containment heatingx

x

Combustion/pressurization phase Bx

In vessel steam explosionx

Inappropriate operation (water supply)x

Induced penetration leak phase B

xAlpha modesx

Small breach, beta mode/phase Dx

U5 filtered containment venting phase Dxx

Basemat penetrationxx

In vessel reflooding succeeds,
loss of confinement

x

x

x
x

Source : EPS2/REP900 Version 4.0, Rapport de synthèse, Tome 2, Résultats en conséquences radiologiques, Rapport
IRSN/DSR/SAGR No. 41, Rapport EPS2/NS1/2009-01
AAR: Automatic Reactor Trip
SGTR: Steam Generator Tube Rupture
TAM : tampon d’accès matériel(SPR, ATWS - PPO) secondary pipe rupture, Anticipated Transitory without scram – Primary Pump Overpressure)
V-LOCA: Loss Of Coolant Accident; mode V refers to the bypass of the containment through pipes leading outside theconfinement.
CCB : Corium Concrete Interaction
U5: venting procedure through a metallic filter and a sand filter designed to reduce radioactivity by a factor 10000.
Mode β: isolation failure (small or large), initial or rapidly induced; the Rasmussen report, published in 1975 under the reference
WASH 1400 and NUREG 75-014, was the first to propose a classification of containment failure modes including five main modes
designed by Greek letters. It is still in use today.
Phase B and D: the evolution of the accident inside the containment is divided into several phases. The progression towards thecore melt corresponds to phase A, the progression of the accident inside the vessel after the core melt to phase B, phase C to
the instant when the vessel ruptures and phase D to the long term phase after this rupture.

3.2. Releases of aerosols by accident families
Released aerosol activity is a physical indicator of the severity of releases. The IRSN PSA2 for 900 MWe reactors,
the most common in the French fleet of reactors, establishes that this indicator can vary between 1015 Bq or less,up 1019 Bq and possibly more, i.e. a ratio of more than 1 to 10,000. This indicator appears to be the most relevant
for the estimation of health consequences and land contamination.
As indicated in section 1, as early as the preliminary 2007 estimates, it appeared that the least severe accidents(S3 accident, with aerosol releases in the range of 1015 Bq) were very different in nature from the most severe
accidents (aerosol releases in the order of 1019Bq). For the sake of economic studies, two accident families havebeen distinguished:

accidents called “severe”: releases are more or less controlled, as in the conventional S3 scenario
described above; this accident family corresponds to releases with aerosol activities between 1015 Bq and1016 Bq;

accidents called “major”: releases are massive, typically relatively concentrated in time; this accident
family corresponds to releases with aerosol activities between 1016 Bq and 1019-1020 Bq in the case of
900 MWe reactors.

This is graphically represented on figure 1 hereafter.

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Figure 1: Accident families and aerosol releases for 900 MWe reactors

Releases withno significant
consequences
E+14

Controlled
releases

E+15

Massive releases

E+16

Severe accident model(median accident)

E+17

E+18

E+19

E+20
Aerosol releases (Bq)

Major accident model(median accident)

3.3. Model accidents intended to represent accident families
Having distinguished these families to give a simplifies sketch of the spectrum of possible nuclear accidents, theobjective is to offer as realistic a picture as possible of each family while avoiding any focus on extreme cases.
Focusing on the most extreme (and least probable) release and on its most severe expression (due to exceptionallyunfavorable climatic conditions), would misguide the decision-maker9, promote suboptimal decisions, cause publicfunds to be wasted and therefore mean unnecessary costs for all French people.
Ideally, one should estimate median costs for each family, i.e. costs having 50% chances of being below the cost of
any particular randomly chosen case, and 50% chance of being above it. To achieve this, one would have to know
the entire statistical distribution of these costs with respect to all their parameters. This is out of reach today.
Therefore, for each family, a median release scenario was established as a first step, a “median” cost then being
pursued for this type of release. A model accident is thus defined for each family; describing this model provides
an understanding of the major features of accidents in the family.
As far as releases are concerned, the median character within the family is determined on the basis of the IRSN
level II PSA for 900 MWe10 reactors. It is the entire set of results of this PSA which allows defining medianreleases11. The set of all possible releases results from the detailed study of very numerous possible scenarios12;

9

The wording decision maker is used in decision theory but does not necessarily represent a person. To be entirely rigorous, itwould be advisable to refer to the “decision process”. This will generally involve many persons. In this sense, misguiding thedecision maker means misguiding many people taking part in the decision process.
10

EPS2/REP900 Version 4.0, Rapport de synthèse, Tome 2, Résultats en conséquences radiologiques, Rapport IRSN/DSR/SAGR No.
41, Rapport EPS2/NS1/2009-01
11

Knowing 101 values drawn randomly and ordered (in increasing or decreasing order), the median corresponds to the 51 st point;
modifying points different from this one can modify the ordering and thus the point representing the median and therefore themedian itself.
12

For example, with 44 aggregated families the distribution of each family being represented by 5 points (with probabilities 1%,
5%, 50%, 95% and 99%), the distribution of releases is defined by 220 points.

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strictly speaking, the median point has no reason to correspond to one of the points which make up the
distribution curve but is generally positioned between two such points. It is thus understood that what is relevant
is the release itself, not the scenarios which imply releases of that order. In general, future progress could consist
in estimating the cost of a finer set of release13.
The model accident for the family “major accidents” corresponds to releases with aerosol activities of 1018 Bq.
This by itself is sufficient to run the simulations; however, a precise accident scenario is concerned, Direct
Containment Heating. A description of this accident is given in appendix 1 although, as just explained, thisdescription is in no way essential for an economic estimation.
The model accident for the family “severe accidents” was determined on the basis of an upper bound for thefamily14 and lower bound approached by the conventional S3 scenario15.
The position of the model accidents within the range of possible releases is indicated on figure 1.

13

For example, E+14 Bq, E+15 Bq, E+16 Bq, E+17 Bq, E+18 Bq, E+19 Bq, E+20 Bq.

14

The size of the release which acts as limit between severe and major accidents, namely E+16 Bq, is approximated by the actual EVHC scenario meaning Steam Explosion outside the Vessel (explosion de vapeur hors cuve).
15

The activity of releases is the most important indicator but their kinetics can also play a role. While major releases occur
rather rapidly (for example, within 2 hours), severe releases can extend over several days, most of the activity being released
during the first 24 hours.

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4. COST ESTIMATION METHODOLOGY

4.1. The “consequences” approach
The first accident studies adopted a “consequences” approach; they mainly focused on radiological effects ofreleases and had in mind the emergency management of a hypothetical nuclear crisis involving radioactive
releases. Here is a short historical account of the development of these studies.
In 1975, the Rasmussen report (WASH-1400) offers accident probabilities for civilian nuclear activities in the
United States; it also suggests accident costs; they range from $1 million to $14 billion. The report is based on
probabilistic safety assessments (PSAs), techniques which were advanced for the time and had been developed in
the framework of military nuclear activities. The figures are quickly criticized despite their novel character. Only
four years afterwards, the Three Mile Island accident occurs in the United States and the safety authority requests
a new report. This is published in 1982 and estimates that the cost could amount to $314 billion in the worst case
(CRAC-216). The computer code used for this exercise gives rise to MACCS; this code is used afterwards for a study
dated 1990 (NUREG-115017) still considered today based on good methodology. In parallel, Europeans conduct the
MARIA project (Methods for Assessing the Radiological Impact of Accidents) which gives rise to the Cosyma code
(Computer system for MARIA); the first PC version of the code is documented as early as 199418.
These two codes essentially calculate radiological consequences; they can be seen as tools pertaining to a thirdlevel of PSAs. Level I PSAs study failure modes leading to core melt; one of their emblematic results is a core melt
probability. After the Three Mile Island and Chernobyl accidents, this appears insufficient because the possibilityof releases must be seriously considered. Level II PSAs aim at characterizing phenomena arising after a core melt;
they calculate the probability and nature of possible radioactive releases. Consequence codes go beyond suchprobabilities and aim at quantifying consequences of a radioactive release, essentially radiological consequences.
One can thus use the term level III PSAs.
A level III PSA includes a code19 which calculates the dispersion of radioactive releases from the site of theaccident and the deposition of radioactive particles onto the ground depending on climatic conditions; a code forthe transfer of radioactivity within the food chain; and a code which calculates health effects by combining
exposure to the radioactive plume, ingestion of contaminated foodstuffs and residual ground shine on the people
who live in contaminated areas.
A probabilistic PSA3 code includes an input interface for “fixed” data such as meteorological data of the year; itcalculates consequences by randomly drawing within these meteorological data. For example, the PC version of

16

CRAC-2 report by U.S. NRC & Sandia National Lab, 1982 ; NUREG/CR-2239

17

Severe Accident Risks: An Assessment for Five U.S. Nuclear Power Plants, December 1990, NUREG-1150

18

PC COSYMA: An Accident Consequence Assessment Package for Use on a PC, final report. Jones, J. A. Luxembourg Office for
Official Publ. of the Eur. Communities, 1994, VII, 63 S; EUR 14916 : Radiation protection.
19

The term “code” is employed by professionals and designates a series of computer programs.

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the European Cosyma code, PC Cosyma 1995, draws 144 sequences equally spaced within one year of data20 whichallows estimating a probability distribution of estimated consequences.
Other fixed data are needed such as land-use, population distribution, etc.
Finally an interface takes into account the intervention of emergency squads and the management by governmentof the post-accidental phase. Such “countermeasures” are taken to reduce the impact of accident consequences.
Emergency countermeasures essentially consists in: evacuating people closest to the accident site when there isenough time; confinement (at home or inside buildings) which concerns people affected by the radioactive plume
but residing further away from the site and therefore a priori less exposed; and the distribution of stable iodine
tablets. Another essential countermeasure consists in banning consumption and sale of foodstuffs beyond a given
level of contamination. The more demanding the ban (the lower the limit concentration), the larger the quantityof banned foodstuffs, the lower the doses ingested by the people and the lower the health consequences;
however, costs can become very high for agriculture.
From an economic point of view, the most important cost items are sanitary consequences and agricultural losses.
The consequences approach, as exemplified by a level III PSA code, provides a probability distribution ofconsequences with respect to climatic conditions. These distributions can be detailed or summarized by theirmeans or their medians.
Given the quantities, it is relatively easy to multiply them by prices (or unit costs) to obtain accident costs.
However, with such an approach, there can be no costs when there is no radiological contamination:
zero Becquerel = zero cost
Therefore this approach only covers part of the costs, namely those linked to the presence of excess radioactivity.
It thus underestimates the severity of the accident for the economy and therefore the value of prevention as
explained hereafter.

20

Approximately every 60 hours, i.e. every 2.5 days.

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Figure 2: The radiological consequences approach
Population exposureRadioactive
release=>Contamination of thefood chain=>

Quantities

=>

nb
nb
nb

Costs

€€
€

4.2. The economic approach
Contrary to the previous approach, the economic approach considers all possible effects, including radiologicaleffects, but also all other possible effects leading to costs. It aims at comparing a situation without accident and asituation where the accident has taken place.
In the course of such a comparison, all costs must be taken into account — a crucially essential point. Indeed an
economic accident cost is bound to be compared, sooner or later, with the cost of the prevention of the concerned
accident. If therefore the cost of the accident is underestimated, so will be the value attributed to its prevention.
As a result, prevention expenses will be lower than they should have been, all other things equal, and the residual
risk retained will be higher than what it should have been, all other things equal.
Thus, the economic approach starts with listing the entire set of all possible effects of the crisis generated by anuclear accident, without any preconception about these effects. The objective is to be descriptive and ascomprehensive as possible.
After having established this list, it is necessary to evaluate the cost of each item in the list. Three aspects should
be underlined at this point:

whether such an estimate is difficult to provide or not cannot justify disregarding the corresponding
effect; indeed, neglecting one type of impact amounts to ascribing it a zero value, i.e. to underestimate,in fine, the value of the accident and therefore the value of its prevention;

in a very general fashion, the method is always the same: estimate all costs, everywhere, for all parties;

besides and very generally, any estimation process is clarified and refined by breaking down the cost
under consideration into components.

The method can thus be illustrated by the following figure.

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Figure 3: The economic approach

The next figure details the differences which have just been spelled out with the consequences approach.

Figure 4: Differences between the consequences approach and the economic approach

Consequences approach (PSA3)

Economic approachzero Becquerel = zero cost

zero Becquerel = possible costs

Physical and medical phenomena which
can be replicatedModeling of physical phenomena,
based, as far as possible, on experimentsIncludes, in addition, social phenomena
not amenable to an experimental
approachEconomic modeling

These points are now detailed.

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4.2.1. Listing all costs
This task should be comprehensive. This is perfectly clear from a methodological point of view but in practice,cost items are always necessarily omitted. Indeed it is impossible to enter into all details, regional and local oreven finer; estimating costs does not consist in writing the saga of all individual stories of all the victims — even if
it were possible.
One should actively look for all possible cost items and ensure that those disregarded remain small relative toother cost items and to the total cost. For example, in the present case, one can pursue the reasonable objectivethat all costs of above €1 billion are considered and estimated.
Even thus, a difficulty remains: how can one guarantee before having appraised it, that a given cost item is
actually below such a threshold? One can only rely on a more or less implicit estimation exercise based on
professional expertise.
In conclusion, whatever the attention given to this phase of the estimation process, it contains a bias towards
underestimation because, while identifying cost items, one can only, in practice, miss one or two21. Remaining
conscious of this bias should limit its extent.

4.2.2. The need to estimate corresponding costs
When one type of impact has been identified, it is imperative to estimate it. Accepting not to provide a figure forsuch or such cost item is tantamount to ascribing it a zero cost. It is impossible to commit a larger
underestimation! No other estimate however imprecise will ever underestimate the corresponding costs by a larger
gap22…

21

There exists a comparable risk in engineering: the costs of a project generally feature a final cost item called contingencies; itis generally expressed as a percentage of costs estimated without contingencies; such percentages vary from sector to sector andare the object of a professional consensus based on experience.
22

Granted, there remains a possibility for costs to be overestimated by a larger amount (i.e. more than doubling the true cost).
Therefore, the methodological requirement to provide a figure by no means allows indulging in large overestimations …

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Figure 5: All the impacts of an accident should be estimatedEffect 1
Radioactive
release=>

Nuclearcrisis=>=>

Effect 2
Effect 3
Effect 4

Effect nnon-estimated effect=>

Effect n-1

Non-listed impact or

Maximum under-estimationof this effect

Under-estimationof the total cost

As examples of identified effects which are a priori difficult to estimate one can mention the impact on tourism
and psychological effects.

4.2.3. For each identified effect, estimate all costs
Having recognized the need to estimate all impacts, all types of consequences, it is again necessary to strive atbeing comprehensive while individually estimating each cost items. From an economic point of view, for example,
it is recognized that a “direct” effect has “indirect” implications.
For instance, as far as tourism is concerned, the image effect of a nuclear accident will directly imply adecrease in tourist arrivals in France. Thus, hotels, restaurants, camping grounds, tourist attractions,etc., will experience lower levels of activities. This constitutes the direct effect (in economic terms).
In the normal course of their activities, the corresponding businesses purchase goods from otherbusinesses. For example, a hotel may use the services of an industrial laundry factory; a tourist attraction
may subcontract cleaning and place orders with a print shop for its leaflets. A direct reduction in tourist
activity (hotel nights for example) causes an indirect reduction in the activity of these providers (lesslaundry, cleaning or printing activity). These indirect effects cascade within the economy (for instance,
the industrial laundry factory reduces its purchases of chemical products and its reliance on transport anddelivery services). Globally all these effects constitute the indirect cost (in economic terms).
Finally, all the declines just mentioned, direct and indirect, affected the earnings of households. For
example, the hotel hires some employees part-time instead of full-time. As a result, households earnlower revenues, they reduce their consumption, which in turn generates further reductions in businessactivity. This is called the induced effect.
For each cost item, it is therefore necessary to perform a triple estimation including direct, indirect and induced
effects.

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Calculating direct effects requires a scenario detailing the way the concerned quantities would be affected; such a
scenario is an essential input. In the framework of the studies conducted by IRSN, scenarios have been establishedon the basis of internationally available data for similar phenomena, for example for image effects. These
scenarios may be refined in the future by specialized studies of the concerned activity sectors.
Indirect effects are classically calculated based on exchanges between economic sectors as reflected in thenational accounts (the so-called input-output tables or the input-output matrix of the economy). In the short or
medium run, it is difficult to see how an economy could escape such indirect effects; in the long run, it is possiblethat national economic activities would find other forms of expression and that compensating activities would
emerge. Estimates computed by IRSN do not enter into this level of refinement. Besides, calculating indirect
effects must also take into account “leakage” outside the national economy; indeed, some indirect effects arebound to materialize in the accounts of foreign providers; they should not be taken into account in an estimate
with a perimeter limited to France.
In quantitative terms, indirect effects depend, strictly speaking, on the sector initially impacted. Indeed, thecoefficients of input-output matrices, i.e. the rates at which sectors in the economy purchase goods produced byother sectors, do vary from one sector to another. However, the impact on the global multiplier is not spectacularand taking an indirect effect of 80% is a quick way to derive an indirect cost. Thus, taking into account the indirect
effect, the overall reduction raises to 180% of the direct impact. The induced effect is taken around 10% of thisamount. In total, considering indirect and induced effects approximately amounts to doubling the effect of theinitial direct reduction. For global estimates, this level of precision is sufficient since probabilistic values are
estimated; in other words, the refinement which could be provided by a precise computation would not modify
practical implications of the estimates for the concerned people and decision-makers.
The estimation method for a cost item is illustrated on figure 6 which also features the breakdown mentioned in
the following section.

Figure 6: Estimating a cost item

Effect 1
Radioactive
release=>

Nuclearcrisis=>

Effect 2
Effect 3
Effect 4
Effect n1
Effect n

Breakdown into
simpler components

Indirect effects(scenarios)——> Need to estimate
the corresponding cost

Indirect andinduced effects
et induits

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4.2.4. Breaking down a cost into components
Breaking down a quantity into simpler elements is not specific to economy estimation, but the method appears
particularly efficient for this type of exercise.
For instance, having identified the existence of image effects, one could provide a global image effect, with nodetails, no structure by activity type, and therefore no explicit vision. This could for example be estimatedsummarily by a reduction in percentage applied to GDP. On the contrary, it was deemed useful to study thephenomena more in depth; the main identified components are:

image effects concerning uncontaminated food products, due to precautionary attitudes on the part ofintermediaries (foreign importers or national retailers) or a simple refusal to buy on the part of consumers
themselves;the reduction in tourist activity;

the impact on other French products, especially exports from the nuclear power sector.

This is a notable improvement compared to an approach without any breakdown. Again, one could be content with
providing a global estimate for each of these components; on the contrary, analyzing things more in depth, main
cost items were distinguished within each component thus leading to a structured picture of the effect underconsideration. For instance, in the case of the impact of a nuclear accident on the French tourism sector, thefollowing components have been distinguished:domestic tourism, i.e. the tourism of French people in France;European tourism, i.e. European tourists visiting France;and international tourism which refers to all other tourists coming to France.

Structuring the phenomena in this way provides an understanding; for example it is possible to point out that
substituting another tourist destination to France is much easier and less costly for international tourists than fordomestic tourists.
A greater understanding of elementary components obviously allows better quantitative estimates. Ideally,
subheadings being fairly well sketched out, their estimation can be more precise; reconstructing the global effectfrom its components is more accurate; with the additional advantage that residual errors can compensate fromone component to another.
It is now necessary to give a detailed description of the cost items retained in the study.

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4.3. The cost items
The following table gives the list of cost items considered in the IRSN study.
Table 3: Five main components, 14 detailed cost items
Item

Comments

Contaminated territories
Exclusion zones

Costs related to radiological refugees (people who lived in
exclusion zones); cost of land considered as capital (nowillingness to pay for a “value of motherland” is included)

Other contaminated territories

Based on feedback from Belarus; takes into account the actual
costs of contamination and the financial support provided to
victims, such transfers acting as proxy for the detriment ofpeople living in such territories.

Offsite radiological costs
Emergency countermeasures

Cost is marginal within this component.

Health costs (radiological)

In addition to exposure to the radioactive plume, they strongly
depend on the quantity of contaminated food ingested by the
population. A boycott by consumers and retailers is considered
possible.

Psychological costs

Mainly lost workdays and costs of long-term treatment. No
allowance for the suffering of patients (i.e. no willingness to pay
beyond purely economic costs).

Agricultural losses

They strongly depend on acceptable concentration limits or on a
boycott by consumers/retailers.

Cost of relocation

Depends on the number of people concerned and on the distance
between housing built for refugees and existing networks

Image costs
Impact on food and agricultural products

Affects marketable foodstuffs fit for consumption; based on the
feedback from events such as the mad cow crisis, the bird flu or
the Spanish cucumber crises in 2011 in Europe.

Impact on tourism

Based on crises having affected tourism worldwide during thepast 15 years.

Reduction in other exports

Based on experience gained from the Fukushima accident,
adapted to the French situation.

Costs related to electricity production

The most plausible scenario, given the French situation, is areduction in the lifetime of reactors.

On-site costs
Decontamination and decommissioning

Based on the feedback from Three Mile Island, as reported by theAmerican consultancy ABZ Inc.

Replacement electricity

Corresponds to the ex-ante production of the lost reactor and ofother reactors on site which could be stopped for several years.

Other on-site costs

Marginal compared to the preceding items

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4.4. Radiological and economic costs
Within the cost items listed above, one can distinguish radiological and economic costs as follows:
Figure 7: Radiological costs and economic costs

Complete costs
RADIOLOGICAL COSTS
Offsite radiological costs
emergency countermeasures
health costs (radiological)
agricultural losses
Psychological costs
Relocation costs
Contaminated territories
exclusion zones
other contaminated territories

ECONOMIC COSTS+

On-site costs
decontamination and decommissioning
on-site electricity production foregone
other on-site costs
Image costs

Classical
consequences
approachfoodstuffs and agricultural produce
tourismindustrial goods
Costs related to electricity production

Observe that the classical PSA level III approach only covers part of possible costs. The quantification given below
shows that it generally represents a relatively low proportion of costs.
These two types of costs are clearly of different nature:Emergency countermeasures, beyond costs borne by the authorities, imply disturbances and income losses
for the people concerned during the time of their (temporary) evacuation.



Health costs relate to people. They essentially correspondent to cancers, lethal or not, which occur
several years after the accident (for thyroid cancers) or several decades after (for the majority of othercancers, according to present knowledge). They are due to exposure to the radioactive plume, toingestion of contaminated foodstuffs and to residual ground-shine in contaminated zones.



Agricultural losses will be felt immediately and very painfully so for the concerned producers. They willentail income losses, clearly, but also, in some cases, the profound modification of an entire way ofliving.



Psychological costs essentially correspond to ensuing sick-leave and to long term psychiatric treatment.
Affected persons will suffer from these ailments, an aspect not accounted for in present economic costs.
These persons are clearly victims of the accident.

Strongly contaminated territories will represent a national loss but will also give rise to potentially highnumbers of radiological refugees; these will have to experience the hardship of emergency shelters, therigors of temporary housing in locations which they will not necessarily have chosen and, finally, the needto reestablish a new life in potentially difficult conditions.

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Finally, moderately contaminated areas do not necessarily imply relocation but force inhabitants tomodify their lifestyle as is the case in Belarus. There is no return to normal, to the status quo ante, but
the need to adapt to a new life; this may sometimes be viewed as degraded, possibly as stigmatizing.

In all these instances of radiological costs, human suffering underlies estimates quantified in monetary terms. This
is not the case with economic costs; such costs are not marked by the same sort of overtone; they do not carry thesame human significance, in any case not in the same proportions:

costs related to the production of electricity will give rise, in the course of time, to increased electricity
bills for the French people; a comparable rise in the cost of fossil energy has already occurred several
times in the past and does not lead to unsurmountable difficulties, particularly because the cost is spreadout over a large number of people. To help picture the situation, if the corresponding costs were €65
billion over 10 years, the bill would amount to about €100 per Frenchman and per year for 10 years which
is not directly comparable to the variety of suffering previously described for “human” costs; it is not
negligible, but remains tolerable by many French homes while schemes could be devised to protect themost fragile households.

Image costs would first be borne by the businesses directly affected. But because of the cascading effects
so will the entire economy, it is likely that corresponding costs would, as those mentioned above, belargely spread out among all Frenchmen.

It is thus not only legitimate but necessary to distinguish these costs because of they are of different natures.

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4.5. Costs are estimated from the point of view of France
To take into account all costs means: all costs, all the time, everywhere and for all involved parties. It is howevernecessary to determine the estimation perimeter: in the present case, costs are estimated from the point of viewof France. More precisely:Radiological costs are estimated independently of the location where they occur; for example,
agricultural losses are not localized, they can affect French agriculturalists or agricultural businesses
located outside the national territory but affected by the contamination23.



Economic costs are estimated from the only point of view of France. Thus, effects on the productionof electricity are limited to the French nuclear fleet of reactors whereas substantial costs would
probably be borne by other fleets of reactors24. The same is true for negative image effects which
could affect areas neighboring the French territory whose agricultural productions and tourism could
experience non-negligible losses. It is also the case for positive image effects or, in other words thesubstitution effect which countries other than France could take advantage of. For example, wine
producers of other countries could benefit from better sales; competing tourist destinations in Europe
or elsewhere could benefit from the transfer of tourists fleeing France25.

4.6. “Median” costs
The considered accidents correspond, as pointed out earlier (3.2 and 3.3), to releases which are median withrespect to the spectrum of possible radioactive releases. The corresponding estimates aim at being median in thefollowing sense.
As far as radiological costs are concerned, the median is essentially located by realizing random drawings within
meteorological data. One observes that distributions — for example the distribution of contaminated areas or of
the population of radiological refugees — are very asymmetrical, with important distribution tails. The mean isthus notably higher than the median. Favoring the mean rather than the median would lead to over represent
extreme cases with respect to their probability and thus suggest a biased picture of the phenomenon26.
For other costs such as for example costs related to foreseeable reductions in tourism activity, it is not possible in
the present state of our knowledge, to rely on a statistical distribution. Such phenomena are unquestionable; they
benefit from modeling, but not in the way physical phenomena undoubtedly give rise to a statistical distribution
with respect to their main parameters. For this reason, we establish a favorable case and an unfavorable case23

One could illustrate this choice by saying that radiological costs would be borne by France, even when occurring abroad, i.e.
that France would compensate affected victims. This is only an illustration which says nothing of hypothetical compensations.
The choice thus made considerably simplifies calculations. It seems more legitimate than excluding everything located beyond
the borders.
24

As was observed after the Fukushima accident.

25

These choices again arise from the need to simplify; the other alternative would mean horrendous complications.

26

Heavy distribution tails is a phenomenon which should be accounted for, but in the framework of a more ambitious study thanthe mere estimation of costs representing median accidents.

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which allow us to provide both an estimation bracket and to check that the suggested estimate is close to a
median value.

4.7. Future progress of research on accident costs
The figures provided here improve upon 2007 estimates, particularly with respect to two important aspects:All economic costs have been revised. All are estimated in more detail, backed by more precise
arguments, using more explicit methodologies.
These are applied to scenarios for example those describing reductions in tourism activity. Such
scenarios result from a careful study of accumulated knowledge, in the present instance relative totourism crises in different countries and different areas of the world. Scenarios are based on actual
meaningful cases and in no way on exceptional events with no established representativeness.
However, IRSN not being a specialist, for example in matters of tourism, it is possible that moredetailed studies reveal more appropriate scenarios in the future, for example due to the particularcharacter of tourism in France or to the specifics of a nuclear crisis.
All economic costs are treated in the same fashion.



As far as radiological costs are concerned, contaminated areas have been estimated on the basis ofsimulation runs on three French sites representative of the diversity of the nuclear fleet; these werecarried out with the computer chain C3X (see section 5). Other radiological cost are based oncomputations carried out for the 2007 report.

Future progress is thus envisaged today in essentially three directions:

confronting the scenarios used for estimating economic costs to the expertise of specialists capable ofimproving them;

implementing a PSA3 study up to the best standards;



studying in detail the contamination of territories.

In addition, indirect costs described above (section 4.2.3) are addressed individually for each type of cost. A more
ambitious approach could envisage grouping all direct costs, and studying indirect costs globally in a second stage.
The advantage of such an approach would be the possibility to resort to more sophisticated macroeconomic tools,
for instance general computable equilibrium models, and to take into account impacts on the financial aspect of
the economy.
The sequel of this report is dedicated to describing the methods used to estimate each cost item mentioned (table
3 or Figure 7). Radiological costs are addressed first, economic costs afterwards.

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5. MODELING RADIOLOGICAL CONSEQUENCES
As indicated in section 4.4 above, a number of components of the complete cost of a nuclear accident are directly
related to radiological consequences of the accident for the people (health risk), for the environment (more orless contaminated territories and natural resources) and for property (particularly agricultural production).
Estimating these cost items thus requires an assessment of radiological effects consecutive to the model accidents
selected to describe each of the two families of accidents. This assessment requires modeling the atmosphericdispersion of releases and their fallout in the form of surface deposits.

5.1. The computer chain
Preliminary estimations conducted in 2007 used the European code Cosyma (PC Cosyma 1995); this is not adequate
to model dispersion over long distances (see appendix 2). Presently, estimates for contaminated areas are basedon the IRSN platform C3X; this is an operational computer chain for radiological consequences (atmosphericdispersion, radioactive fallout and doses potentially received by exposed persons) intended to be used in an
emergency situation.
This platform relies on two distinct atmospheric dispersion codes:
a Gaussian model (called pX) intended to calculate dispersion over limited distances (a few dozen
kilometers); it is comparable to Cosyma in this respect;a Eulerian model (called ldX) dedicated for long distances (several hundreds to thousands of kilometers).

Appendix 3 provides technical details.
Like all Gaussian models, pX is based on the analytic solution of the advection-diffusion equation obtained undersimplifying hypotheses (see appendices 2 & 3). This Gaussian solution features standard deviations which model
the spread of the plume as a function of time. Classically, their time-evolution is modeled by empirical laws derived from experiments carried in situ. Several such laws exist and are, essentially, taken into account by pX. Suchmodels have the advantage of being fast and able to operate with limited input data. However, contrary to Gaussian model Cosyma, pX is a so-called puff diffusion model. Breaking down the plume into independent puffs makes
it possible to provide a fine rendering of the complex kinetics of a release and, more importantly, of a flow which
is not homogeneous in space and time. In contrast, plume models such as Cosyma assume homogeneous wind fields
which de facto limits their validity. IRSN considers that pX used with a tridimensional wind field is valid up to 80
km from the site, an empirical appreciation.
Eulerian model ldX resolves the advection-diffusion equation on a grid. Such models are frequently used torepresent atmospheric pollution, for example relative to road traffic. ldX is a cutting edge code for practicalapplications27. Contrary to Gaussian models, ldX is capable of simulating the dispersion of a pollutant over long27

In a purely scientific framework, unconcerned with applicative considerations, other modelling possibilities exist, notably
Lagrangian models. However, theoretical advantages of these models can be limited by practical considerations of representativity. The superiority of one type of model over the other is not established today.

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distances, up to the entire globe. However, by its very principle, this type of model provides an average
concentration per elemental cell of the grid, which limits its utilization to areas removed from the site of theaccident by more than 5 to 10 times the size of a grid cell.

5.2. Climatic data
The rendering of climatic conditions is considerably more detailed in C3X than in Cosyma. As explained above, thisis due to the very nature of the modeling approach. Cosyma represents climatic conditions over the entire
computation domain by a few parameters pertaining to the site (hourly meteorological data at the site). As every
plume model, it shifts the plume mechanically, in one block, hour by hour, in response to changes in the climaticconditions at the site.
In contrast, pX models the plume as a fine series of independent puffs which evolve in response to the climaticconditions they encounter as they travel. Meteorological conditions (wind, rain) vary in time and space; they areinterpolated from available meteorological data; these are typically provided by the French Meteorological
Institute (Météo France) on a 10 km grid and hourly. This approach is much more realistic than in Cosyma and isnotably capable of taking into account topography and orography.
On the other hand, Eulerian model ldX features even finer physical models, directly calling on more than 20
advanced meteorological parameters such as relative humidity or height of clouds. The size of its computation grid
generally corresponds to that of the meteorological data used as input, for instance, 211 x 141 grid elements of 10
km for a run over France with nine levels on the vertical up to about 3 km in altitude.

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6. COSTS RELATED TO CONTAMINATED TERRITORIESThe following sections detail the estimation procedure for the cost items listed in table 3. The aim is essentially topresent the main features of the methods adopted. Details will appear in technical notes to be published in the
future.

6.1. Two categories of contaminated territories
Contaminated areas are calculated as indicated above and are grouped in two categories depending on the extent
of cesium 137 contamination taking as a reference the decisions taken after the Chernobyl accident in Ukraine,
Russia and Belarus:
Exclusion zones, i.e. highly contaminated territories from which populations must leave for many years. In
reference to the Chernobyl accident, they corresponded to cesium 137 deposits above 555 kBq/m²28.
After the Fukushima accident, Japanese authorities based their decisions on dose limits which correspondto very similar levels of activity.



Other contaminated areas, where cesium 137 deposits are comprised between 37 and 555 kBq/km²29.

These two categories are each considered globally: a flat cost per square kilometer is applied to corresponding
areas resulting in an estimation of the costs of contamination. This approach may be refined in the future.

6.2. Unit costs of exclusion zones
The unit cost adopted in the absence of further detailed studies is 10 M€/km². This round figure — to be refined in
the future —, is acceptable since its contribution to the overall cost is minor30. Nevertheless, a few elements on
this topic can be suggested:
Two approaches can be considered for this figure: a utilitarian approach which estimates the value of corresponding
areas by the sum of revenues they can provide to their residents; and on the other hand, a willingness to pay approach
which estimates how much the people are ready to pay to avoid having one square kilometer of their territory
becoming an exclusion zone.
A utilitarian approach for rural areas can rely on the value of agricultural production; this leads to a value of
5.6 M€/km²31. The value of a territory being greater than its sole agricultural value, a figure of 10 M€/km² does notseem absurd32. In a willingness to pay approach, one could call upon estimates produced by health economists 33; a28

15 Curies/km², the previous unit for activity which was used by the soviet authorities.

29

That is to say between 1 Curie/km² and 15 Curies/km².

30

No effect on the severe accident for which exclusion zones are of negligible extent as a first approximation; about 3% for the
major accident (see table 5 of section 6.4 hereafter).
31

French agricultural value added amounts to about €72b for an agricultural area of 32 million hectares; this leads to an annual
mean value of 2,250 €/ha. Summarily discounting at 4% (social discount rate) results in a value of 5.6 M€/km².
32

A value of €1m per km² must be rejected if one wants to remain representative, as well as a value of €100m km².

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value of 10 M€/km² would then be equivalent to the loss of eight life years in rural areas34 which again appears
acceptable as a first approximation.

6.3. Unit costs of other contaminated territories
Unit costs of other contaminated territories amount to 5.23 M€/km²; this is based on experience of the
management of this type of area reported for Belarus35 which corresponds to the following figures:
Table 4: Euro equivalents of annual public aid in Belarus
Solidarity

2 000 € per ha and per year

Support to agricultural businesses
Environmental cost

650 € per ha and year
375 € per ha and per year

Source: CEPN, Note NTE/06/28

Here are a few comments on these figures which relate to rural areas.
Environmental costs to be envisaged after a nuclear accident particularly relate to the management ofcontaminated agricultural or forest products — more generally to the management of the environment. It could
vary widely with respect to land use. The feedback from Fukushima should make it possible to refine significantly
the global figure proposed; it may then appear low during the first few years, but may also turn out high 10 or 20
years after the accident.
Support to agriculture varies widely in France according to the type of agriculture; this has been the case for many
years without any nuclear accident occurring. A significant part of direct support originates from Europe’s common
agricultural policy which amounts to about €10 billion per year for French agriculture, i.e. on average slightly over
300 €/ha36. Given this partial indication, the above-mentioned figure does not appear totally unreasonable, atleast as long as the concerned areas are not huge.
Solidarity grants form the major part of the unit cost in Belarus; these grants are not all costs, strictly speaking,but largely correspond to transfers just as the diverse solidarity grants existing in France. Corresponding figures
provide a first approach (which will need to be refined) of the detriment relative to living in a contaminatedterritory; it is for this reason that they are used here37. This aid corresponds to expenses relative to health such as“clean meals” served twice a week in schools or holidays in non-contaminated areas offered to schoolchildren;
bonuses paid out to civilian servants; benefits granted to employees; etc. The unit cost of 2000 €/ha represents

33

To avoid wasting public funds in the health sector, i.e. avoid a performance inferior to what could be achieved at the same
cost, health economists I provide a monetary equivalent of a life-year saved. Estimates range from 20 000 €/year to 50 000€/year in various studies (see, for example, Le coût du cancer, Philippe Tessier, http://www.sgoc.fr/DU%20oncogeriatrie/20092010/007%20tessier.pdf)
34

Assuming a life-year at 35 000 € (see previous footnote) and using a rural population density of 35 per km².

35

A study performed by the CEPN in 2006 to help establish this estimate.

36

European Common Agricultural Policy in 2009 amounted to 9867 M€ for France with an agricultural area of 32 million hectares.

37

The same logic leads to use the support to agriculture as a proxy to measure its losses.

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about €5700 per person and per year38. In the future, this cost item should benefit from being broken down andanalyzed in the context of the French post-accidental doctrine.
In total, the unit cost retained is close to 300 000 €/km² per year (3025€/ha in the above table 4). The global
amount calculated (5.23 M€/km²) thus corresponds to 17.44 years whereas the lifetime of contaminated zones
would evidently be longer. The reduction thus operated is due to a discounting procedure at the rate of 4% over 30
years which calls for an explanation.
Several reasons favor simplifying by leaving unit costs constant over 30 years and neglecting residual costs:
radioactive decay reduces the pollution from cesium 137 by half in 30 years’ time;aid, for instance directed to agricultural businesses or to the management of the environment, must havea cumulative effect, improve conditions, and lead to stabilized situations over 30 years;



finally, it is likely that public support be reduced after a period of 30 years; this would reflect a “social
stabilization”: those who wished to live elsewhere are gone, those who remain on-site have adapted tothe situation…

Is it not illusory to attempt to model finely the diversity of such effects? Is it not, on the contrary, simpler andmore transparent to simplify as indicated? In order to refine, it would be necessary to model areas decreasing withtime as well as decreasing levels of public financial support. In any case, as a first approximation, brutally adding
30 additional years to the proposed estimate, with the same areas and the same unit costs, and discounting using adecreasing rate of discount would constitute a large overestimation39.

6.4. The extent of contaminated areas
The extent of contaminated areas has been estimated in 2007 using the Cosyma 1995 code. This code is only valid
at short distances from the site and remains, in this range, a rudimentary tool given what is possible to achieve
today. However, these estimates offered the advantage of not neglecting an element of cost (see section 4 above,
particularly figure 8), of pinpointing the problem in the case of large releases, and of pointing out the need toprogress on this question. Estimates relative to the severe accident, where the contamination of territory does notplay a crucial role, remain those of Cosyma; on the other hand, the contamination due to major accidents is
estimated with the computer chain C3X used at the IRSN crisis center (section 5.1). This is a cutting edge tool; it
was used to study three different sites representing the variety of all French sites; for each site, 100 simulations
were run based on random drawings from the actual meteorological data of year 2010.

6.4.1. The severe accident
For this accident, exclusion zones are very limited in extent (between zero and 20 km² median values). They are
therefore taken equal to zero in the present study. More detailed estimates will be proposed in the course of PSA3
studies which should not modify global cost estimates.

38

In rural areas, the average density of population amounts to 35 habitants/km² environ.

39

It would add about 40% to the proposed cost; this should probably be reduced by more than half, but the costs of the first 30
years should then also be reduced…

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Other contaminated territories spread over 2 100 km² (median value). The unit cost mentioned above(5.23 M€/km²) leads to an order of magnitude of €11 billion for the cost of “other contaminated territories”. The
cost for the first year would be 700 million (on the basis of 0.3 M€/km² per year, see 6.3 above) which appears
sustainable for the country’s budget, at least for several years.

6.4.2. The major accident
For the major accident, corresponding median areas (see 4.6) are:


1,300 km² of exclusion zones; and18,800 km² of other contaminated zones.

This implies a complete estimate of €110 billion as indicated in table 5 below.

Table 5: Cost of contaminated territories for a major accident (billion euros)
Areas withdrawn from production

13

1,300 km² of exclusion zones @10 M€/km²

Other contaminated areas

98

18,800 km² of other contaminated territories

Total (rounded)

110

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7. OFFSITE RADIOLOGICAL COSTSThis cost category includes five items:emergency countermeasures;

health costs (radiological);

agricultural losses;

relocation costs;



psychological costs.

The first three items correspond to the classic “consequences” approach (see 4.1, as well as figure 7 of 4.4).

7.1. The cost of classic consequences
As explained in section 4.1, the most immediate consequences are the health effects of radioactivity, essentiallyan increase in cancer risk. In order to reduce this risk, emergency countermeasures are in order such as
evacuation, confinement and ingestion of stable iodine tablets. They are temporary and their cost is relatively
low. Another measure appears very quickly: restrictions on the consumption of contaminated foodstuffs whether
this is decreed by the authorities as maximum admissible concentration levels or results from a rejection bysociety (a boycott initiated by consumers, or possibly due to retailers, or even a ban decided by the producers
themselves). The more severe the restriction, the more health costs are reduced. These three components are
therefore related and, in practice, their estimation can only be jointly calculated on the basis of a computer code.
The code used here is the European Cosyma code (see 4.1) which was the basis for the results obtained as early as
2007; these provide an order of magnitude for the cost of classic consequences; it can be used for calculating
global figures.
For severe accidents, these costs vary between a low estimate of €3.1 billion for the conventional S3 accident (seesection 1) which is a lower bound for accidents in this category; and an upper bound of €14.6 billion for the S3D
accident intermediate between S3 and S1. A mean figure of €9 billion was retained. This simplification appeared
legitimate for at least two reasons:Modifications which may result from future detailed estimates will only affect a few percentage points ofthe total cost40; they will not modify the global implications of the figures.



Detailed estimates need extensive computation capabilities and a refinement in analysis which will
require a few additional years of work.

These estimates assume that all contaminated foodstuffs are lost, particularly because of a boycott byconsumers41; this assumption appeared the most realistic in the case of a severe accident where contamination40

A 50% modification would only result in a 4% difference in global costs; this would not affect global conclusions…

41

The code uses the concentration beyond which food is lost as a parameter. The minimal figure accepted by Cosyma is
10 Bq/kg, a very low concentration which correctly represents the boycott assumption.

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remains limited in extent and in time. As a result, agricultural losses nearly represent the total offsite radiologicalcosts, consumers exercising extreme precaution. Health costs only represent a few percentage points of offsite
radiological costs. Consumers give priority to their health and that of their loved ones even at the cost of heavy
losses for the agro-industrial sector. This type of social trade-off, which needs to be confirmed and studied in
more depth in the future, shows how important are the reactions of society for the management of the crisis.
Incidentally, there is a link between social acceptance in France and the extent of image costs which are largely
due to a decrease in foreign demand (section 8.1 hereafter).
In case of a major accident, assuming a boycott of contaminated produce appeared excessive because quantities
concerned would be much higher (thus making substitution much more difficult), on the one hand, and because
the contamination of foodstuffs could last for several years thus allowing explanations provided by specialists toconvince at least part of the population. It is assumed that contaminated products would be consumed up to alevel of 100 Bq/kg, the concentration limit adopted in Belarus a few years after the Chernobyl accident, as well asin Japan since April 2012.
Given this less stringent rejection of agricultural production by society, offsite radiological costs of major
accidents vary between €48.4 billion for the upper bound S1 and €5.9 billion for the intermediate S3D accident
considered as the lower bound of the category42. The average cost then amounts to €27.1 billion. Again, future
modifications resulting from detailed estimates will only affect a few percentage points of the global cost43. They
will help better understand the variability of these costs within the category of major accidents.
In contrast with the severe accident, health effects significantly contribute towards costs, varying between 9% of
health and agricultural costs to more than 40% of these costs.
Table 6: Health and agricultural costs of the severe accident
S3

Severe accident

S3D(Billion euros)Billion euros

Short-term health effects

00Emergency countermeasures01Long-term health effects
Agro industrial losses
Total

0

0%

0,1

2%

0,5

3%

0,3

3%

3

98%

14

96%

8,5

96%

3

100%

15

100%

8,9

100%

Source: Cosyma, computations conducted for the GP 2007 report, concentration limit 10 Bq/kg, representing a boycott ofproducts, even slightly contaminated, by consumers and by the retail sector. The severe accident is the mean of S3 and S3D.

42

The intermediate S3D accident thus features offsite radiological costs of €14.6b with a concentration limit of 10 Bq/kg (section7.1), but only €5.9b, less than half, for a concentration limit of 100 Bq/kg which is nevertheless stringent according to a numberof radio protectionists. Moving from boycott to 100 Bq/kg increases the percentage share of health costs; this is mechanically
due to the reduction of the agricultural bill and, to a lesser extent, to ingestion of contaminated foodstuffs below 100 Bq/kg.
43

A modification of 50% in this figure, however substantial (€26b) would only represent 5% of the total cost of major accidents.

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Table 7: Health and agricultural costs of the major accident
S3D

Major accident(Billion euros)

S1
Billion euros

Short-term health effects

00Emergency countermeasures

0

6

13%

3,1

11%

Long-term health effects

0,6

9%

20

41%

10,3

38%

5

88%

22

46%

13,8

51%

6

100%

48

100%

27,1

100%

Agro industrial losses
Total

Source: Cosyma, computations conducted for the GP 2007 report, concentration limit of 100 Bq/kg

7.2. Psychological costs
Psychological disorders may arise from dramatic events in a person’s life; they can be experienced as disasters, forexample being diagnosed with cancer, losing a loved one, etc. Some accident victims can experience in this way
the personal upheaval implied by the accident (the need to leave one’s land, the loss of employment, separation,etc.). Psychological disorders such as depression, anxiety disorders and posttraumatic stress can then appear. War
conditions have triggered the study of these types of disorders, particularly when affecting soldiers returned tocivilian life. In general, psychological disorders affect the health of their victims, reduce their capacity and maylead to sick leave; corresponding costs are borne by the person, by the state through its health system and bybusinesses.
Disasters — whether natural, technological or sociopolitical —, are traumatic events at the collective level: they
produce a collective posttraumatic stress which causes a significant increase in psychological disorders — i.e.
ailments considered as such by health institutions. Their expression is globally the same as those of disorders not
related to a disaster.
Psychological disorders are considered as serious health consequences of catastrophes in general, of the Chernobyl
and Fukushima accidents in particular44. The cost must thus be estimated whatever the difficulty of the task45.
The proposed numerical estimate is limited to the most immediate costs, those which would directly affect theeconomy, i.e. the cost of healthcare extended to victims of psychological disorders, particularly the most seriously
affected persons, and corresponding sick leave. Ex-ante, society may be ready to spend more to avoid
psychological disorders as is the case for such ailments as cancer. As a first estimate of psychological costs, such a
direct approach to the willingness to prevent has been considered too ambitious, open to criticism, as well as
difficult to implement in practice. As a starting point, it was deemed preferable to limit the scope of the estimate
to direct costs; this first step nevertheless sheds light on a number of unknown features of this question. At a later44« A 25 Year Retrospective Review of the psychological consequences of the Chernobyl accident », E.J. Bromet, J.M. Havenaar,
L.T. Guey, 2011, Clinical Oncology n°23, p.297-305; “Fukushima: Fallout of fear”, Geoff Brumfiel,
http://www.nature.com/news/fukushima-fallout-of-fear-1.12194
45

Not estimating these costs would lead to underestimate the value of prevention (see section 4 above). To our knowledge, theproposed estimate is the first in this field.

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stage, the contribution of such costs to the value of preventing corresponding accidents will need to go beyond
direct costs.
Estimating the psychological cost requires scenarios depicting the increase in psychological disorders after anuclear accident; these remain schematic, but reflect existing studies worldwide46. These do suggest increases in
psychological disorders consecutive to a catastrophe and essentially distinguish between a proximate zone(“epicenter”) and a distant zone; psychological effects are naturally more acute in the proximate zone,
particularly among relocated persons. In the case of a nuclear accident, compulsory relocation zones seem toprovide the most natural definition of a proximate zone. This model implies important variations of psychologicalcosts with respect to accident location and climatic conditions.
Two types of economic consequences are implied by psychological disorders: the cost of healthcare and the cost ofcorresponding sick leave. The direct cost of healthcare has been estimated on the basis of French studies
dedicated to psychological costs after a disaster47. The total cost of sick leave includes the cost for the Health
Insurance and the direct and indirect costs for businesses48.
This first estimation exercise shows that psychological costs would not be negligible in case of a major accident:
between €12 and €22 billion depending on the location of the accident. It is composed of 45% healthcare,essentially (90%) extensive and prolonged treatment; 55% are due to the cost of lost workdays. This breakdown
varies dramatically during the course of the 25 years during which losses due to psychological disorders49 occur:
losses related to sick leave represent 75% of the total in the first year but decrease to 25% of this total at the endof the period.
Psychological costs thus represent about 4% of the total cost for the major accident. Therefore, they should beconsidered by crisis management. In contrast, they would represent less than 1% of the total cost of a severe
accident (less than €1 billion). These estimates are based on studies which will be proposed for publication in
peer-reviewed journals.

46

The prevalence of benign and moderate mental disorders is around 10 %, mean worldwide value, according to the WHO Studyon Mental Health Worldwide, 2000 edition. This could double and rise to about 20% after being exposed to a disaster as was thecase after the 2004 tsunami in Asia according to the study “Mental Health Assistance to the Populations Affected by the Tsunami
in Asia” published by WHO (2010). The prevalence of mental disasters would then decrease in the course of time to settle after a
few years around 15 % in the areas severely affected by the disaster. Thus in the long run, the excess in psychological disorders
could be 5 to 10 points above the initial situation before the disaster.
47

Studies conducted in France by the InVS after storm Xynthia and by the ‘Direction Générale de la Santé’ after the floods of theSomme and those experienced in the Gard area. According to these studies, the direct cost of psychological healthcare in France
amounts to € 2,000 per person and per year. The major part relates to the most severe cases which require a prolonged stay in
specialized facilities.
48

The total cost of sick leave in France would amount to some 315 euros per lost workday. Half this cost would be borne by the
Health Insurance, the other half by businesses according to a study by Aon Consulting (2008). When multiplied by the annual
number of lost workdays, this unit cost provides an estimate of the annual cost of sick leave.
49

Five years only in the event of a severe accident.

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7.3. Relocation costs
Relocation costs arise because it is necessary to provide housing to radiological refugees. Based on the Fukushima
experience, three stages must be considered: emergency sheltering which lasts up to a few months at most;
temporary housing in temporary shelters such as prefabs; and finally, permanent relocation after 2 to 5 years50.
Emergency sheltering costs represent less than 5% of total relocation cost. As far as other items are concerned,
housing standards comparable to what is observed elsewhere in the world have been assumed for permanent
relocation, while temporary sheltering conditions are based on Japanese post-Fukushima standards.
With this knowledge of standards, evaluating relocation costs in France requires unit costs for the three types of
housing. These were obtained from housing and construction professionals through private interviews, i.e.
unpublished data. The main factor for cost variations turns out to be the construction of water and electricity
distribution networks. To reduce relocation costs, one should therefore be careful to relocate refugees as close as
possible to existing networks and to build permanent housing, as far as possible, on the sites used for temporary
relocation so as not to duplicate the construction of the said distribution networks.
As a result, the cost of relocation is estimated around €100,000 per refugee with an uncertainty bracket of ± 30%.
The cost of relocation in case of a severe accident should therefore be lower than €1 billion, whereas it could
amount to some €10 billion in median terms in case of a major accident (about 2% of total accident cost). Theseestimates are based on studies which will be proposed for publication in peer reviewed journals.

50

The time span required for the construction sector to resorb excess demand consecutive to the nuclear accident.

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8. IMAGE COSTS
Image impacts can be very serious for affected economic entities: think about tourism in Tunisia or Egypt or thesad affair of the “Spanish cucumber” (Europe, 2011). Three image costs are considered here: the impact on safe
agricultural produce; the effects on tourism in France; and the effect on other French exports, notably those of
the nuclear power sector.

8.1. Agricultural image effect
The idea that lost agricultural productions are limited to those measured above maximum concentration limits
would lead to a sizable underestimation of the cost of a nuclear accident. The immediate effect of an image crisis
affecting food products is the reduction in demand for the products perceived as risky, including those free of any
contamination. Accounting for these losses therefore entails no double counting with those relative tocontaminated agricultural productions.
A recent emblematic example of a food image crisis is that of the “Spanish cucumber”. In the course of the 2011
summer, cucumbers produced in Spain were suspected of being contaminated by bacteria possibly causing serious
damage to human health, only to be exonerated of this charge afterwards. The suspicion of contamination was enoughto stop their consumption. The boycott extended beyond the mere Cucurbitaceae and all Spanish exports of fruits andvegetable plummeted during several weeks. Weekly losses were estimated around €200 million for the Spanish
economy. Being the second European producer of cucumber after Spain, and although located several hundreds ofkilometers from the suspected site of contamination, the Netherlands also suffered from the crisis with losses
estimated around €10 million per week.

In general, as soon as the first case of contamination is known, exports drop by more than 40%, dramatically andsuddenly51; the return to normal extends over a period of 2 to 3 years. In the meantime, 10% to 20% domestic
consumers turn away from the foodstuffs subject to this type of branding and substitute them with other products
considered healthier. Feedback from Fukushima is less clear than this general picture52.
Such percentage reductions in demand essentially concern the food industry, agriculture and food retailers. Whenapplied to the value added by these sectors, they provide an estimate of direct image effects.
Corresponding losses imply indirect effects and induced effects (see 4.2.3) which, globally, are not agriculturaland approximately amount to about the same level of losses as agricultural losses themselves.

51

These figures are based on the effects in France of crises having affected the meat sector reported in the study « Les effets
sanitaires de la filière viande » published in 2007 by INSEE (the French Statistical Institute). The food crises considered in France
are the foot and mouth disease in 2001 and the bovine spongiform encephalopathy (BSE) in 1996 and 2000. Outside France, thefollowing crises have been examined: the avian flu in 2005, the severe acute respiratory syndrome (SARS) in 2003, the Fukushima
accident in 2011.
52

In Japan, food exports for the first nine months of year 2011 (320 billion yen) are lower by 7 % in value compared to the same
period of year 2010 (344 billion yen).

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In total, the complete image effect on agricultural products is estimated at €13 billion for a severe accident and€60 billion in case of a major accident53 which amounts to 10% and 14% of total cost. These estimates are based onstudies which will be submitted for publication in peer reviewed journals.
The agricultural dimension thus appears of primary importance for nuclear crisis management and the image ofconcerned productions does represent the most critical problem.
Table 8: Agricultural image cost (billion euros)
Severe accident Major accident
Direct costs

1

2

Indirect costs

1

2

Induced costs

0

0

Total

1

5

8.2. Impact on tourism
Crises affecting tourism activity are numerous; they become more and more costly as international tourism
develops.
In order to establish scenarios for the reduction in tourist activity after a nuclear accident in France, it has
appeared essential to distinguish three components within the French tourist activity: domestic tourism, European
tourism and international tourism. Indeed, different tourists tend to behave differently.
The quality and the level of detail of the information they rely upon strongly depends upon their distancefrom France. In matters of image, a distant consumer tends to globalize; even if a limited portion of
French territory were affected, the distant consumer (American, Chinese, etc.) would nevertheless tend
to consider the entire country to be contaminated. In contrast, the French and European tourist has
better knowledge of France and is not as easily mistaken.



The distant tourist faces many more alternative possibilities. Granted, France is unique… but Italy is alsoa beautiful country and, for a distant tourist, choosing the latter practically implies no additional cost.

The extent of radiological consequences would necessarily influence the reduction in tourism activity; different
scenarios have therefore been sought for the severe and the major accident on the basis of more or less acutetourism crises reported through the statistics of the World Tourism Organization54.
Research on tourism crises indicates that about half of the reduction in tourism activity could be due to European
tourists regardless of the type of accident. This result should help managers to reduce corresponding costs.

53

These estimates represent sizeable increases over those proposed in 2007. Figures are computed at the date of the accident.

54

http://www2.unwto.org/fr

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In total, the complete impact of the reduction in tourism is estimated at €25 billion in case of a severe accident
and €75 billion for a major accident, these figures being calculated at the date of the accident. The order ofmagnitude of this image effect is therefore slightly below 20% of total accident cost. It is larger than the
agricultural image effect. Needless to say, it deserves full attention from crisis management. These estimates are
based on studies which will be proposed for publication in peer-reviewed journals.
Table 9: Tourism image cost (billion euros)
Severe accident
Direct costs
Domestic tourism

13

Major accident
36

2

5

European tourism

7

17International tourism

4

14

Indirect costs

928

Induced costs

3

11

Total cost

25

75

8.3. Industrial image effect
Effects on industry in general are distinguished from effects on the nuclear power industry.
An order of magnitude for the former has been sought on the basis of the Japanese experience. The March 11,2011 disaster caused a sudden reduction in final demand for manufactured products in Japan (both national andforeign); this was followed by a rapid return to normal, less than one year after the catastrophe55. Mechanically
duplicating the Fukushima experience would imply a reduction in demand for industrial products of 25%
immediately after a major accident and a relatively rapid return to normal within 3 to 6 months. However, Frenchindustry carries less weight than the Japanese56. Besides, accidents considered here should logically have less
impact than a combined natural disaster and nuclear accident as was the case in Japan. For this reason, thereduction consecutive to a nuclear accident in France has been considered lower, at about 10%; however, it would
affect the French economy for a longer time period, between 6 to 24 months after the accident; indeed, it would
not benefit from the economic stimulus resulting from the cleanup of debris and the re-construction effort
required by the earthquake and tsunami in Japan.

55

Statistics from the METI (Ministry for Economy, Commerce and Industry).

56

Industry represents 14 % of French GDP in 2011 compared to 27 % for Japan in 2010.

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As far as the French nuclear power sector is concerned, it would first and foremost be affected by worldwide
demand. IAEA conducts regular prospective studies. These reflect a reduction of the share of nuclear power inworldwide electricity production after Fukushima57. The shortfall related to the Fukushima accident is thus
estimated around 20% of world nuclear production in 2030. Such studies provide a first approach to estimatedlosses for French exports: a reduction of 20% following a major accident (and four times less after a severe
accident). One could argue that the market share of France could also be affected; this, however, would be moretheoretical than practical, because most French nuclear exports are composed of long-term contracts relative tonuclear fuel and maintenance of existing reactors.
These are the direct losses due to the reduction in demand; they produce indirect effects and induced effects
which approximately amount to the value of direct losses. The table below summarizes corresponding costs.
Table 10: Industrial image cost (billion euros)
Severe accident
Direct costs
Excluding nuclear power

6

Nuclear power

Major accident
22

3

11

3

10

Indirect costs

5

19

Induced costs

1

5

Total cost

12

46

With these assumptions, the industrial image cost is estimated at €12 billion for a severe accident and €46 billion
in case of a major accident; about 45% is relative to exports of the nuclear power sector. The importance of thisimage cost is therefore non-negligible, amounting to about 10% of the total cost of the accident.

57

Energy, Electricity and Nuclear Power Estimates for the Period up to 2050, AIEA, 2010 Edition and 2012 Edition

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9. IMPACT ON THE COST OF ELECTRICITY PRODUCTION
Worldwide experience shows that a nuclear accident causes modifications in energy policies. The Fukushima
accident has thus accelerated the exit from nuclear power in Germany; previously, the Chernobyl accident had
brutally put an end to Italian projects in this area58. While civilian nuclear has not been banned in the East after
the Chernobyl accident — other days other ways —, the Japanese situation is quite critical. Three years after theaccident, practically all nuclear sites in the country had stopped producing and the cost of the situation was
estimated at some $30 billion per year59. This clearly says how important this component is for the country while
no one knows for how long this standstill will last despite efforts by the government to put an end to it.
It is therefore essential to produce an order of magnitude for this cost component — which is often called the“fleet effect”, referring to the impact of a nuclear accident in France on the French fleet of nuclear reactors. It istherefore necessary to establish scenarios describing the changes which might affect the French reactor fleet after
a nuclear accident: end of nuclear? Status quo?
An intermediate path between these two extremes seems more likely:
doing nothing, openly or more or less covertly? This seems impossible given the present state of affairs,
even if in other circumstances, comparable for instance to the oil shock of the 1970s or even more
dramatic, the political world could decide to “do nothing”. This scenario would require further
examination because “doing nothing” would nevertheless imply numerous adjustments, revisions, controls
and reactor shutdowns — all of which would be costly.

closing down French nuclear sites as early as possible? Stopping nuclear production seems even moreunrealistic than doing nothing, but one could perhaps imagine circumstances, improbable today andcertainly extremely unfavorable, under which the politically world would decide to terminate nuclear
electricity production in France as fast as possible. Such a scenario would also necessitate further study
because delays implied in providing replacement solutions and the host of repercussions it would entail
are not simple to figure out.

This section addresses the estimation of the fleet effect — which is indispensable given the size of thecorresponding costs. It also addresses on-site costs, essentially because the computations required are of the same
type for the cost of replacing electricity production forgone on-site.

9.1. Effect of a major accident on the French fleet of reactors
In a context where a possible life extension of French reactors is under discussion, the adopted scenario considersa kind of “moving 10 year reduction” of the lifetime of nuclear reactors constituting the present French fleet. The
most serious difficult may not consist in a time schedule of shutdowns — which can be broken down, rendered

58

The Caorso nuclear site was brought to a sudden halt sine die and the work ongoing on the Montalto di Castro site was closed
down following a referendum in 1987.
59

World Nuclear News, 22 February 2013, Shikoku joins rate hickers. It refers to the excess cost of imports of fossil fuels in 2012:
3,000 billion yen (estimate by the Japanese authorities).

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more realistic and refined in many ways — but in estimating the production the nation would thus renounce to. In
other words: what would have happened without any accident? Would all reactors have seen their lifetime
extended for 20 years as requested by EDF thus extending their lifetime from 40 to 60 years? Or should one beeven more ambitious and consider, as the Americans do, that it is possible to extend the lifetime of reactors up to
80 years (which would increase the weight of the fleet effect because the accident would imply higher losses of
production)? Or should one consider, in the absence of any accident, a scenario where the share of nuclear in
French electricity production is reduced in line with the policy considered in 2013 (this would, on the contrary,
reduce the cost of the fleet effect)?
The practice of safety discussions has suggested a realistic scheme. In France, the nuclear fleet is subject to indepth “decennial visits” which constitute, for each reactor, an essential prerequisite for the pursuit — or not —, of
its activity for a further 10 year period. This feature has been the basis for the proposed scenario: in the absenceof accident the lifetime of reactors is extended by blocks of 10 years. But in case of a major accident, authorities
reconsider the previous decision to prolong in principle the lifetime by 10 years. A number of reactors are notdirectly affected; they had experienced their lifetime being extended by 10 years, at least in principle, less than
10 years back; this is now revised; they fall back to the status quo ante60. But a few reactors have already been in
production for longer than the revised reactor lifetime. In the scenario calculated here, these reactors are
immediately shut down which probably overestimates the corresponding costs.
The scenario then features the replacement of the forgone nuclear capacity by a mix of CCGT61 gas turbines andrenewable energies which moves in time towards more renewables as these become more competitive. A unit
replacement cost is thus estimated and applied to the structure of the French fleet of reactors resulting in a total
replacement cost. This is schematic because very large capacities must be installed within reduced time periods62.
In this simplified vision, the cost is nil at the end of the lifetime of the fleet which probably underestimates thecosts; except if the replacement of the fleet at the end of its lifetime was planned, before any accident occurred,
to take place by means of production entirely nonnuclear or at least sufficiently safe for the accident not to haveany effect on their commissioning.
This scenario raises a number of other questions, notably relative to the greenhouse effect, to safety of supplies,
to safety modifications and to effects in the very long term — and these have not been addressed63. Nevertheless,it offers a first vision of the effects of a nuclear accident on the French fleet of reactors and provides aquantification between €116 billion for an accident in 2010 and a zero cost in 204064. Indeed, the size of the fleet
effect is directly related to the number of reactors existing at the date of the accident. The mean value of the60

In a general context which would probably be extremely delicate, with notably reinforced controls, etc.

61

Combined Cycle Gas Turbine, today the most competitive alternative.

62

Today, due to the immense construction effort which took place in France in the 1970s and 1980s, a mechanical renewal ofreactors at the end of their lifetime would be confronted with a quite stiff “cliff effect”.
63

In addition, estimates assume constant electricity demand and constant nuclear production; alternative scenarios are theobject of endless controversies.
64

Commissioning date of the last reactor of the 2013 fleet plus 40 years. The life extension of French reactors is not enacted; itwould increase the value of the fleet effect.

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cost discounted to the date of the accident then amounts to €88 billion. This value is close to that for an accident
occurring in 2025.
It represents 20% of the total cost of the model major accident. It is therefore essential that crisis managers beconcerned with this aspect, address it in the most rational fashion possible and strive to reduce its costs for thenation.

9.2. Fleet effect after a severe accident
The above scenario seems plausible in the context of a major accident with widespread land contamination and, inall probability, profound political and social transitions. In the case of a severe accident, radiologicalconsequences being more limited, industrial constraints should be more prominent in decisions about the future ofenergy. In particular, commissioning the required electricity production capacities in replacement for nuclear
could prove difficult and reduce the rhythm and extent of these replacements. A reduced rate of replacement
would, in addition, allow smoothing out the age composition of the fleet of reactors. The French fleet has been
constructed at a very sustained pace, a particular feature which requires replacing sizable production capacities invery few years if one adopts a uniform replacement rule; this cliff effect reduces the flexibility of the national
electricity production system.
I the absence of a scenario with a “simple” structure, comparable the previous one, the above figure was simply
divided by half leading to a proposed estimate of €44 billion. Doing so, the weight of this component rises from
20% to 37% of the total cost meaning that the stakes appear more pressing than in the case of a major accident, atleast in relative terms. This phenomenon reinforces the likelihood of a marked reduction of the fleet effectcompared to the scenario adopted for the major accident65.

9.3 On-site costs
Three cost items have been identified as constituting economic costs on the site of the accident: decontaminationand decommissioning costs; the cost implied in replacing the electricity not produced on-site because of theaccident; and other costs.
In any case, the reactor which caused the accident is lost. In case of a severe accident with more or less controlled
releases, other reactors are stopped for several years before being started again as was the case after the Three
Mile Island accident. The damaged reactor is decontaminated immediately after the accident. Afterwards, itenters a phase of monitoring before being eventually deconstructed simultaneously with other site reactors at theend of the lifetime of the site.
In case of a major accident, the site is entirely closed and decontamination and decommissioning operations canstart immediately.
In both cases, the cost of decontamination and decommissioning is the discounted excess cost of these operations
compared to a situation without accident. It is composed up to 75% by decontamination costs and is estimated at

65

The lesser weight of the fleet effect in the event of a major accident essentially reflects the higher share of other challenges
because of the heavy radiological cost component.

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Methodology used in IRSN nuclear accident cost estimatesin France, report PRP‐CRI/SESUC/2014‐132€4.8 billion in case of a severe accident and at €5.4 billion in case of a major accident. These estimates are basedon feedback from Three Mile Island — which could be underestimated. Data which will come from Fukushima will
be of great interest, particularly unit costs of specific operations; aggregate figures should turn out significantly
higher than in Three Mile Island due to the wreckage caused by the strength of the tsunami, because four reactors
are affected and because explosions have occurred. Such scenarios are excluded from the present study which only
addresses the case of an accident affecting only one reactor. The global figures from Fukushima will thus have to
be used with caution.
The cost of the replacement electricity corresponds to the value of the lost reactor, on the one hand, to which isadded the cost of temporary shutdown of other reactors on site. In case of a severe accident, these replacement
costs are estimated at €5.6 billion at the date of the accident using the same methods as for the fleet effect(again the replacement is carried out by a mix of CCGT gas turbines and renewable energy according to the same
modalities and at the same prices as for the calculation of the fleet effect). This figure rises to €9.3 billion for the
major accident with the complete loss of the other reactors on site.
Finally other on-site costs include residual maintenance and the monetary value of doses on-site personnel might
be exposed to. These costs are negligible compared to other on-site costs.
In total, the proposed estimate of on-site costs at the date of the accident amounts to €10 billion for the severe
accident and €15 billion for the major accident.

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10.

SYNTHESIS OF RESULTS AND PROSPECTS

10.1. Synthesis of results
The outcome of the estimation of the 14 items detailed above is the following:
Table 11: Estimation of accident costs in France (billion euros)

Severeaccident

On-site costs

Rehabilitation

55

Replacement

6

9

Other on-site costs





TOTAL

Contaminated territories

15


13

Radiological control zones

11

98

11

110

Emergency
countermeasures3

Health effects

10

Psychological effects

017Agricultural losses

914

Relocation cost

0

10

TOTAL

Image costs

10

Exclusion zones

TOTAL (rounded)

Offsite radiological costs

Major
accident

954

Reduction in demand forFrench agricultural
products

1360

Reduction in tourism
demand25

75

Reduction in other exports

1246

TOTAL (rounded)

50

180

Effects on the electricity
production system

44

88

TOTAL (rounded)

120

450

ε means a cost which low, but only from a relative point of view: lower than €1 billion

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Accidents are taken as models of their families (see section 3.3); their estimates aim at being median (see 4.6).
The above figures are globally identical to those published in 2012, differences being due to work conducted since
which does not modify the conclusions to which they point, namely:
1. A major accident profoundly differs from a severe accidentsevere accidents lead to a crisis which is globally of economic nature, a great part of costs being borne by
the entire population;in contrast, major accidents would lead to massive radiological consequences, the number of victims
being potentially high and all kinds of population being potentially affected.

2. This information is of interest for crisis managers


they help elaborate a global vision of nuclear crises; they thus contribute to avoiding, in the early hoursof the crisis, mistakes which could be extremely costly in the long run;

they help prepare crisis management by showing that radiological consequences are only part ofanticipated difficulties, sometimes a minor part of costs; they suggest extending preparation to address
the other foreseeable cost items;

they open up the possibility of working on the reduction of these costs.

3. This information is of interest for safety

extreme accident cases face the nation with very high stakes;consequently, their lower probability does not necessarily compensate for their potential for disaster…

10.2. Prospects
Before moving on to actual prospects, such estimates require a few words of caution:

The proposed estimates describe the phenomena under consideration. Studying extreme cases would be
more demanding and this is the reason why it is not addressed at this stage. For illustrative purposes only,
studies suggest that the variable severity of releases within each of the two families (variable source
terms) is likely to imply costs varying in the order of -50% to +100%. Overall costs, otherwise median,could thus vary within the family of severe accidents between €50 and €250 billion; within the family ofmajor accidents, the median could vary between €200 and €1,000 billion.



One should keep in mind that the probabilities of such accidents are very low. Focusing attention on
nuclear accidents, in fairly great detail as this report does, bestows upon them a reality which can blurthe initial assumption i.e. that a radioactive release has occurred on the French soil — which remains
unlikely. Many persons, on electricity production sites and within control authorities specifically dedicate
all their efforts to avoid such accidents. The above estimates can only reinforce their dedication and theirlegitimacy.

Beyond the possible avenues for progress described at section 4.7, prospects which can be envisaged today for
improving this type of work are, in the order of the above-mentioned cost items:

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

on-site costs should benefit from lessons learned at the Fukushima decommissioning site. It is possiblethat the proposed estimates, based on figures arising from the Three Mile Island experience, turn out
somewhat optimistic;

the cost of contaminated territories should benefit from further studies of the unit costs per square
kilometer of contaminated territories; in particular, specific studies should detail the effects on specificeconomic activities of given territories as well as collateral effects on neighboring uncontaminatedterritories;

off-site radiological costs should, in the future be based on detailed PSA3 studies;

image costs could benefit from specific studies conducted outside IRSN which would lead to more precise
scenarios of the image impacts on one hand; and on the other hand, it would be desirable to conductmacroeconomic studies of indirect effects. Instead of addressing these item by item, they could thus bestudied globally at the level of the country which is expected to give better results. Financial impacts
could be included.

Such studies should provide a more detailed understanding of the corresponding phenomena thus moving beyond
the global pictures provided in this report.

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Appendix 1. The DCH accident scenario
The DCH accident scenario corresponds to a station blackout leading to a core melt. This occurs six hours after the
initiator; fission products are released inside the confinement until the vessel ruptures, about 11 hours after the
initiator. Up to this moment the confinement is considered intact and leaks from the confinement are normal(extremely limited). However, because of the loss of electricity supply, water sprinklers are unavailable inside theconfinement and air circulation systems are at a halt in auxiliary buildings. In this scenario, the vessel isinsufficiently depressurized when it ruptures; part of the melt fuel (corium) is thus projected into the confinementin the form of particles; this subjects the confinement to a very high pressure, beyond the design pressure. This
very improbable situation is called “direct containment heating” (DCH). It is assumed that this phenomenon causesa breach in the confinement; its representative section is taken equal to 27.5 cm². The end of the release occurs
after 30 days.
Table A1.1: Synthesis of rejected activities by isotope and by family

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Appendix 2. The Cosyma dispersion model
The description below figures in: EURATOM 18822, Probabilistic accident consequence uncertainty assessment
using Cosyma, Uncertainty from the Atmospheric dispersion and deposition module.

Atmospheric dispersion is modelled in COSYMA using a version of the Gaussian plumedispersion model, modified to allow for hourly changes in atmospheric conditions such as windspeed and direction, diffusion category and precipitation rate. The model assumes that theconcentration distribution within the plume of material is Gaussian both vertically and horizontallyat right angles to the mean wind direction.
The basic equation of the Gaussian plume dispersion model is‫ݔ(ܥ‬ǡ‫ݕ‬ǡ‫= )ݖ‬(‫ݖ‬െ ‫) ܪ‬ଶ(‫ݖ‬൅ ‫) ܪ‬ଶܳ଴‫ݕ‬ଶ
exp ቆ− ଶቇ[exp ቆ−
+
exp
ቇ
ቆ−
ቇ]
ʹߨߪ௬ ߪ௭
ʹߪ௭ଶ
ʹߪ௭ଶ
ʹߪ௬

Where
C(x,y,z) is the time integrated concentration at (x,y,z) [Bq s/m3],
Q0is the initial quantity of contaminant released [Bq],u is the (constant) windspeed (always in x direction) [m/s],
H is the height of the release [m]andσyand σzare the lateral and vertical plume spread, respectively [m].
‫ݍ‬ߪ‫ ݕ‬ൌ ‫ݕ ݔݕ݌‬ߪ‫ ݖ‬ൌ ‫ݖݍݔݖ݌‬Methodology for nuclear accident cost estimates , rapport PRP‐CRI/SESUC/2014‐132

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The standard deviation of the Gaussian distributions (σy and σz) are described in
COSYMA using power law functions.
For one set of atmospheric conditions, the target variables of the Gaussian plumedispersion model are py, qy, pz, qz. COSYMA considers dispersion in the six atmospheric stability
categories proposed by Pasquill, and designated A to F. Therefore 24 target variables wereidentified for the atmospheric dispersion model, namely the parameters py, qy, pz, qzin each of the 6stability categories. This was subsequently reduced to 16 target variables, as explained in Section
2.7.
The calculations consider both dry and wet deposition to the ground.
Dry deposition is calculated using the deposition velocity, where the deposition rate is the
product of the air concentration at ground level and the deposition velocity. The calculated air
concentration is modified to allow for the effect of plume depletion during its travel, using thesource depletion model. The deposition velocities for three forms of released material, namely
aerosols, elemental iodine and organic iodine were considered to be uncertain in this study. It was
assumed that all material released in particulate form has the same deposition velocity. The
deposition velocity for noble gases was assumed to be zero, with no uncertainty.
Dry deposition to skin was also considered, with different values of the deposition
velocity to skin for the three types of material identified above.
Wet deposition is calculated using the out coefficient, Λ, the fraction of dispersing
material deposited by rain in unit time. The washout coefficient is related to the rainfall rate, R, byΛ = a Rb
so the target variables are the quantities a and b. As with dry deposition, different values of theseparameters are used for material released as aerosols, elemental iodine and organic iodine. It was
assumed that all particulate material has the same values for these parameters. It was assumed that
noble gases do not deposit.
Therefore 12 target variables were identified for the deposition model, namely thedeposition velocities to ground and skin and the parameters of the expression for washout
coefficient for each of three types of material.

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Appendix 3. The C3X platform

The ldX model66
ldX originates from a chemistry transport model adapted for IRSN purposes. Such models are used to address anumber of environmental questions at the global scale (climate change, stratospheric ozone layer hole) or at aregional scale (cross boundary pollution, large-scale industrial accidents, quality of urban air). They have played afundamental role since the 1980s as a basis for scientific and technical expertise in the context of atmosphericpollution (for example, for understanding the hole in the ozone layer). For instance, the model EMEP67 was used by
the European Union as a decision making support in the context of country level emission limits for a large numberof pollutants (directive NEC, National Emissions Ceiling, 2001/81/EC).
The dispersion of pollutants into the atmosphere, at all spatial scales, mainly depends on meteorologicalconditions. It results from two major phenomena acting simultaneously: transportation by wind, or advection,
which carries the pollutant and affects the direction and dispersion of the plume; and turbulent diffusion whichmixes the pollutant with the surrounding air in a chaotic fashion. A large number of exchanges take place at
different scales; at the local scale, close to the source, effects related to the release itself and to neighboring
obstacles dominate; at the regional scale, the effects of topography play a major role; beyond, at the continental
scale, extending over several hundred to several thousand kilometers, the transport of pollutants is mainly
influenced by large-scale atmospheric dynamics (depression, anticyclone, etc.). ldX is particularly suitable tomodel flows at regional and continental scales.
ldX considers chemical species in gaseous phase or in the form of aerosols (matter condensed in the atmosphere);it aims at modeling their interactions and how they may transform under the action of different processes in theatmosphere. Pollutants rejected in the air are horizontally transported over long distances by large-scale air
movements and are dispersed under the action of turbulences which mix them with clean air. The period for which
they remain in the atmosphere is essentially determined by deposit processes, whether humid or dry. ldX describes
atmospheric dispersion in the three dimensions of space under a non-stationary regime. Being Eulerian, it
considers elementary volumes of space through which it models the flow of matter; in other words, theatmosphere is discretized and the equations of fluid mechanics are solved for each elemental volume. This allows
integrating complex flow conditions, such as obstacles or significant topography, and obtaining a refined analysis
of dispersion in time. At each time step, ldX calculates activity concentrations over the predefined tridimensional
grid. This type of modeling provides a natural rendering of complex meteorological fields such as provided byweather forecast models.
So-called “dry” deposits result from the interaction between products released into the atmosphere and theground; they are addressed through the notion of deposition velocity. On the other hand, so-called “humid”
deposits only result from scavenging of the released products by rain; they are calculated mainly based on the66

Extraits de Quélo et al., Validation of the Polyphemus platform on the ETEX, Chernobyl and Algeciras cases, Atmospheric
Environment, Volume 41, Issue 26, August 2007, Pages 5300–5315
67

Kevin Barrett and Erik Berge, July 1996. Transboundary air pollution in Europe. EMEP/MSC-W Report 1/96

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intensity of rain. Turbulence is addressed by a turbulent diffusion coefficient appearing in conservation equations
solved by the model. Lastly, filiation and radioactive decay phenomena are taken into account in the same fashion
as in pX.
In order to conduct a simulation, ldX requires the following input:data describing the different products released (decay and filiation of concerned radio elements, dry
deposition velocity, scavenging coefficients of particles, etc.);data describing the release: its location, its composition, the quantities of released products as a functionof time;

tridimensional meteorological data (wind speed and direction, temperature, rain, height of clouds, etc.)
as a function of time.

On the basis of this input data (and of a number of other parameters such as the space-time grid, and numerous
physical and/or numerical values), ldX calculates instantaneous activities in the air and deposits on the elemental
areas of the grid.

The pX model68
1.

General presentation of the model

Modeling turbulent dispersion of matter by Gaussian puffs addresses the transportation of pollutants in theatmosphere in a simplified fashion. The approach is well adapted for operational uses because computation times
are short and required input data fairly simple.

1.1 Analytic solution of the advection-diffusion equation
The theoretical foundation of the method is the advection-diffusion equation for an instantaneous release from apoint source. The principle of conservation of a scalar quantity allows expressing the instantaneous concentration
c of this quantity through the advection-diffusion equation:c uc  Dc  S
t

(1.1)

where u is the instantaneous speed, D the molecular diffusion coefficient and S the source term. The Reynolds
decomposition into mean and fluctuating values provides the advection-diffusion equation for the average
concentration C:

C UC  DC  uc  S
t

(1.2)

This equation is difficult to solve in the general case involving any given turbulent flow. But a few simplifying
assumptions make it possible to derive an analytic solution. It is thus supposed that:68

Abstracts from : Soulhac, L. et Didier, D. (2008). Projet pX, note de principe pX 1.0. Note technique IRSN/DEI/SESUC/08-39

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the turbulent flow u c  can be expressed using the gradient of average concentration as C , where
K is the tensor of turbulent diffusivity;the tensor of turbulent diffusivity is diagonal;molecular diffusivity D is negligible compared to turbulent diffusivities Ki ;

there is no mean flow;

turbulent diffusivities Ki are uniform and constant.

The distribution of concentration induced by an instantaneous release (at instant t0) of a mass Q of pollutant
issued from one point (with coordinates x0, y0, z0) is then given by the Gaussian relation:CQ
8   t  t0  32


  x  x0 2  y  y0 2  z  z0 2 
1
exp 
KyKz 
 4  t  t0   Kx
KxKyKz(1.3)

From the solution of this equation, it is possible to express the time evolution of the standard deviations i of the
distribution of concentration:

i  2K i  t  t0 

(1.4)

It has been known for a long time (Taylor, 1921) that the previous result only gives a good approximation of reality
for sizable diffusion periods. Indeed, in the neighborhood of the source, the assumption of a constant turbulent
diffusivity is not applicable because the dimension of the puffs has a filtering effect on the spectrum of turbulent
energy. The only eddies to contribute to the diffusion of the puff are those with sizes smaller than the dimensionof the puff whereas eddies of larger sizes cause a displacement of the center of mass of this puff. As a result, inthe neighborhood of the source, the standard deviations i increase proportionally to  t  t 0  .
In order to move forward without perfect knowledge of the time evolution of the standard deviations i, it ispossible to reformulate equation 1.3 to make them appear explicitly:C 1   x  x 2  y  y 2  z  z 2  
0
0
0
 

exp


3
2
2
2
2


2




2




  x y z
x
y
z



Q

(1.5)

Even if the theoretical assumptions supporting this relation are not generally verified, it has been experimentallyobserved that the previous equation describes the behavior of a puff of pollutant reasonably well. However, tocompute the standard deviations during the course of the growth of the puff, an adequate parameterization isnecessary.
In practice, a great number of phenomena control the growth of the standard deviations σi as the puff of pollutant
diffuses in the atmosphere. Many parameterizations have been developed in the past, empirical or theoretical.
They are more or less complex and generally all depend upon the degree of thermal stratification of theatmosphere. In pX, the user can choose between several parameterizations: the Doury model, the Briggs model,
the Pasquill model or else a definition of the coefficients for turbulent diffusivity.

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1.2 Dispersion models with Gaussian puffs
In an actual situation, meteorological conditions and quantities of pollutant frequently vary in the course of time.
The simple solution of equation 1.5 is not adequate to describe the dispersion of pollutants in such a situation. It isnecessary to develop more complex approach. In a puff model, this consists in representing the release ofpollutant as a succession of discrete instantaneous releases, each of which is modeled as a Gaussian puff diffusing
in the course of time. The center of mass of each puff is advected by a speed field which is supposed uniform but
evolves in time. At a given instant, the concentration in any point in space is obtained by adding the contributionsof all the puffs produced since the beginning of the release. The principle of this type of model is illustrated on
Figure A8.
Figure A8: Scheme of a Gaussian puff dispersion model

The black dot represents the location of the source. Circles illustrate the puffs used to discretize the plume.
The choice of the time step used to discretize the release must be adjusted in order to correctly represent:

the kinetics of the release;the evolution of meteorological conditions;an overlap of different puffs capable of giving the plume a sufficiently “continuous” aspect.

Numerical schemes used for the advection phase of the puffs must be consistent with the type of available
meteorological data (continuous or discretized according to given time step). It is generally not necessary to use
excessively complex methods, because of the many assumptions made otherwise.
The puff diffusion phase is based on empirical or theoretical parameterizations as already mentioned. In the pXmodel, computing the i is based on the transit time t of the puff from the source or on the distance traveled x.
During the advection-diffusion phase of the puffs, it is necessary to account for two phenomena: the presence ofthe ground which may capture part of the pollutants; and the temperature inversion at the top of the limit layer
which prevents the vertical diffusion of pollutants. Methods explained in section 1.1. would be used to this end.

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2.

The diffusion modelThis section explains the method used to calculate the diffusion of the puffs. It is based on the computation ofstandard deviations using empirical formulations (Doury, Briggs, Pasquill) which are adapted to account for
modifications over time in the stability conditions of the atmosphere.
The model uses a Gaussian model of atmospheric dispersion for an instantaneous release from a point source. The
distribution of concentration in space is modeled at any given time by an analytic Gaussian formula which features
the standard deviations x, y, z in the three directions x, y et z. Therefore, the dispersion process ― i.e. thespread of the pollution plume — is accounted for by the time evolution of these standard deviations. The time
variations in standard deviations are directly related to the turbulence of the atmospheric flow; this in turndepends upon two effects:

the state of thermal stratification;the shear of wind due to its friction with the ground.

Operational models of atmospheric dispersion generally use theoretical and/or empirical parameterizations whichlink the evolution of standard deviations to the dynamic and thermal characteristics of the flow. Two types ofparameterizations are generally distinguished:Parameterizations by classes. The data necessary to precisely qualify the state of thermal stability of
the atmosphere is not often available making it necessary to evaluate it from a few basic values (windspeed, presence or absence of clouds, etc.). A simpler and very widespread approach consists in using alimited number of stability classes, the most frequent being the Pasquill classes and, in France, the Douryclasses.

Continuous parameterizations. The similarity theory of Monin-Obukhov allows describing the thermal
stability of the atmosphere in a precise fashion through a parameter called the called the Monin-Obukhov
length. New parameterizations of the standard deviations have been proposed based on this formalism
which today tend to replace the approach by classes (such formulations are currently being developed forpX).

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3.

Modeling mechanisms involved in deposition

Pollutants transported by the flow can deposit onto the ground in two ways: through reactions between the groundsurface and pollutants present in the neighboring of the ground (dry deposit); and/or by scavenging of the entire
cloud by rain (humid deposit). These two phenomena lead to, on the one hand, a reduction in air concentrations
and, on the other and, to a transfer of pollution to the ground, vegetation or aquatic systems. It is therefore
important to take them into account when studying atmospheric dispersion.

3.1 Dry deposits
Dry deposits can take place through several mechanisms (whatever the nature of the ground) such as absorption,
dilution into water, particulate deposit. It is generally considered that the deposition flow (the mass of pollutant
deposited by unit of surface and unit of time) is proportional to the concentration of pollutant in the air in theneighborhood of the ground Sehmel69:

 dépotsec  x, y,t   Vd C  x, y, z  0, t (3.1)

where Vd is a speed of deposit. This is controlled by different mechanisms:


Aerodynamic resistance. This is the limited capacity of turbulent flows to diffuse pollutants from thecloud to the ground. If the flow is not turbulent (for instance in a stable atmosphere), the speed ofdeposit will be limited by the speed of diffusion of pollutants in the atmosphere.

Resistance of the sublayer. The air layer located close to the ground constitutes a limit to thedeposition of matter because the transport of species can only be performed by molecular diffusion forgases and by inertia for particles. This limiting mechanism is controlled by the roughness of the surface.

Resistance of the surface itself. This is related to the physicochemical affinity between the materials
present on the ground surface and the pollutant.

Sedimentation processes. In the case of particles, inertial phenomena induce a deposition velocity.

Sehmel69 provides a list of characteristic values for the total deposition velocity under different conditions (natureof the pollutants, of the surface, of wind, etc.). These values vary between 10-3 cm.s-1 and 180 cm.s-1. In the pXmodel, deposition velocities are defined for each isotope. It is supposed that they are constant in time anduniform in space, that is to say independent from the nature of the ground.
The quantity deposited by unit of surface during a time dt for an isotope endowed with deposition velocity Vd istherefore:

Q dépot sec  Vd . dt . C  x, y, z  z sol (3.2)

In order to model decreasing concentrations in the plume due to deposition, it is necessary to subtract depositedquantities from the mass of pollutants transported by the cloud. In the pX model, this is supposed to be uniformly
distributed among puffs (“decrease at the source”) and is simply represented by a decrease in the quantity ofpollutant contained in the puff:

69

Sehmel, G. A., 1984. Deposition and resuspension. In Atmospheric Science and Power Production, NTIS report.

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Methodology used in IRSN nuclear accident cost estimatesin France, report PRP‐CRI/SESUC/2014‐132dM    dépotsec  x, y,t  dx dy   Vd  C  x, y,z  0,t  dx dy
dt
sol
sol

(3.3)

Considering that concentration due to a puff can be written in the following form (equation 1.5):

C  x , y , z , t   M (t) . g a u s s x  x , t  . g a u s s y  y , t  . g a u s s z  z , t 
avec






ga u ss x x, t  d x  

g a u ss y  y , t  d y  z so lg a u s s z z , t  d z  1(3.4)

The evolution over time of the mass of pollutant transported by the puffs then writes:dM  M(t).Vd .gauss z  z  0,t 
dt

(3.5)

In the pX code, relation 3.5 is discretized with respect to time:M(t  dt)  M(t) 1  Vd .gauss z  z  0,t  dt 

(3.6)

3.2 Humid deposition (scavenging)
When rain falls through polluted air, pollutants (whether in gaseous or particulate form) are partly absorbed byraindrops and thus dragged down to the ground. These dissolved pollutants disappear from atmospheric air and are
eventually transferred to groundwater or water courses (as, for instance in the case of acid rains). This
atmospheric scavenging phenomenon is called humid deposition. It is important to account for these phenomena
because they contribute to reduce pollution in the atmosphere and increase it in other media.
In the pX model, scavenging by rain is considered to lead to a homogeneous reduction in pollutant concentration ineach puff. Rain is supposed homogeneous in space over the entire computation domain. Supposing that rain falls
vertically, the quantity deposited onto the ground by area and time unit can be modeled by: dépot humide  x, y,t    P 0

C  x, y,z,t  dz

(3.7)

where P represents the intensity of rain (in mm.h-1) and α a constant relative to each isotope. Using relation 3.4 todescribe the concentration field caused by a puff, the deposited quantity during time dt writes:

Q dépot humide  x, y, t    . dt .P . M(t) . gauss x  x, t  . gauss y  y, t (3.8)

Generally, the value of α is taken equal to 10-4 mm-1.h.s-1. The efficiency of scavenging is therefore uniform for a
puff; it only depends on the scavenging constant associated with the species transported the puff. As was the casepreviously, the value does not change during the computation; the rate of reduction of concentrations due toscavenging in a puff can be written as:dM    dépot humide  x, y,t  dx dy   P M(t)
dt
sol

(3.9)

In the pX model, the above equation is discretized by:M  t  dt   M  t  1   P . dt Methodology for nuclear accident cost estimates , rapport PRP‐CRI/SESUC/2014‐132(3.10)

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