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Environmental sensitivity as a tool for the risk assessment of the use of nuclear energy

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Abstract

Approaches to the management of risk in radioecology have to take into account geographic, climatic, living and dietary habit differences, as well as ecosystem differences. The understanding of the factors of sensitivity of different environments, populations or geographic areas is important for scientists and policy makers to set priorities for the allocation of limited resources in the preparedness phase and also to improve emergency and post-emergency management. In particular, the identification of vulnerable environments will be valuable in planning the locations of new nuclear facilities. A Task Group on Radioecological sensitivity was organized by the International Union of Radioecology (IUR) in 2007 on the basis of studies of the Radioecological Sensitivity Forum, 1998-2001. The objective was to discuss a standardization to represent the radiological state of the environment following accidental pollution and to develop a scale of radioecological sensitivity for use in emergency planning and preparedness. The work of the Group continued under the International Atomic Energy Agency (IAEA) EMRAS II Programme (Environmental Modelling for Radiation Safety), from 2009 to 2011, as Working Group 8 on Environmental Sensitivity. Three main categories of factors are of paramount importance in the decision process for the management of radiological emergencies: environmental, economic and social factors. The WG8 focused its studies on sensitive non-urban environments. The aim was to investigate which environments, which components of each environment, and which seasons of the year would be most sensitive to a major release of radionuclides. The concept of environmental sensitivity has been assumed by the participants to the WG8 as a -relationship among three elements: a set of effects or consequences A, an independent set of conditions B and a set of given stresses C. The exercises in this work were performed by accounting for such a definition of sensitivity. The overall aim was to aid the planning and response in case of emergency, as well as the long-term countermeasures following a nuclear accident.
Environmental sensitivity as a tool for the risk assessment of
the use of nuclear energy
Carini F.1, Barabash S.2, Berkovskyy V.3, Brittain J.E.4, Chouhan S.5, Eleftheriou G.6, Iosjpe
M.7, Monte L.8, Psaltaki M.6, Shen J.2, Tracy B. 9, Tschiersch J.10 and Turcanu C.11
1 Università Cattolica del Sacro Cuore, Via Emilia Parmense, 84, Piacenza, Italy
2 EcoMetrix Incorporated, 6800 Campobello Road, Mississauga, ON L5N 2L8, Canada
3 Division of Radiation, Transport & Waste Safety, IAEA, PO Box 100, 1400 Vienna, Austria
4 Natural History Museum, University of Oslo, Norway
5 Environmental Technologies Branch, AECL, Chalk River, ON, Canada
6 National Technical University of Athens, 15780 Zografou, Greece
7 Norwegian Radiation Protection Authority, Grini næringspark 13, Østerås, Norway
8 ENEA, Via P. Anguillarese, 301, 00100 Roma
9 Retired, formerly with Radiation Protection Bureau, Health Canada, Ottawa, Canada
10 Helmholtz Zentrum München, Institute of Radiation Protection, 85764 Neuherberg, Germany
11 Belgian Nuclear Research Centre, SCK•CEN Boeretang 200, B-2400 Mol, Belgium
E-mail contact: franca.carini@unicatt.it
1. Introduction
Approaches to the management of risk in radioecology have to take into account geographic, climatic, living
and dietary habit differences, as well as ecosystem differences. The understanding of the factors of
sensitivity of different environments, populations or geographic areas is important for scientists and policy
makers to set priorities for the allocation of limited resources in the preparedness phase and also to improve
emergency and post-emergency management. In particular, the identification of vulnerable environments will
be valuable in planning the locations of new nuclear facilities.
A Task Group on Radioecological sensitivity was organized by the International Union of Radioecology (IUR)
in 2007 on the basis of studies of the Radioecological Sensitivity Forum, 1998-2001. The objective was to
discuss a standardization to represent the radiological state of the environment following accidental pollution
and to develop a scale of radioecological sensitivity for use in emergency planning and preparedness. The
work of the Group continued under the International Atomic Energy Agency (IAEA) EMRAS II Programme
(Environmental Modelling for Radiation Safety), from 2009 to 2011, as Working Group 8 on Environmental
Sensitivity. Three main categories of factors are of paramount importance in the decision process for the
management of radiological emergencies: environmental, economic and social factors. The WG8 focused its
studies on sensitive non-urban environments. The aim was to investigate which environments, which
components of each environment, and which seasons of the year would be most sensitive to a major release
of radionuclides. The concept of environmental sensitivity has been assumed by the participants to the WG8
as a -relationship among three elements: a set of effects or consequences A, an independent set of
conditions B and a set of given stresses C. The exercises in this work were performed by accounting for
such a definition of sensitivity. The overall aim was to aid the planning and response in case of emergency,
as well as the long-term countermeasures following a nuclear accident.
2. Materials and methods
The models used in the exercises were CHERPAC [1], ECOSYS [2, 3], FDMT-RODOS [4], the Health
Canada model, IMPACT [5], MOIRA-PLUS [6], NRPA box model [7] and NTUA 3D model [8]. The following
environments located in different geographic areas were chosen for the analysis of sensitivity: temperate
agricultural and alpine (Europe and Canada), coastal marine (Nordic seas, North-East Aegean Sea,
Thermaikos Gulf Mediterranean Sea), temperate forest (Northern Saskatchewan and Ontario), freshwater
aquatic (Norway, Italy, Northern Saskatchewan and Ontario) and Arctic (Northern Canada). Each
environment was allocated the same initial single deposition (1000 Bq/m2) of two long-lived radionuclides -
137Cs and 90Sr - and one short-lived radionuclide - 131I. Deposition was considered under four different
seasonal conditions, corresponding roughly to winter, spring, summer, and autumn. The end points of the
exercise were the radionuclide concentrations in environmental media and food chain products leading to
humans as well as the radiation doses to an adult, a 10-year old child and a one-year old infant who receive
most or all of their food intake from the respective environments, during first, second, and 10th year following
the deposition. Sensitivity analysis was then performed to ascertain which components of each environment
are most responsible for ecosystem response and can thus lead to higher doses.
3. Results and discussion
Critical sensitivity factors were identified, regarded as responsible for the major radionuclide impacts on each
environment, such as: high aggregated radionuclide transfer rates to mushrooms and berries and to game,
high transfer factor of radiocaesium from contaminated feedstuff to lamb, long residence times, presence of
permafrost, high mass interception factors and long biological half-times in lichens. For lakes and coastal
environments: water depth, mean water retention times and sedimentation rates, ionic concentrations and
ecological factors that influence the transfer of radionuclide to biota.
Sensitivity is time dependent. Calculations comparing the sensitivity factors of an alpine (Øvre Heimdalsvatn,
Norway) and a lowland lake (Bracciano, central Italy) performed by MOIRA-PLUS show that the alpine lake
is more sensitive to 137Cs deposition than the lowland one, because of the low biomass, the low ionic
concentrations and high runoff over frozen ground in spring. However, the persistent levels of contamination
in the lowland lake give rise to continued high activity concentrations in biota, indicating its higher
vulnerability in the long term.
Climate is another important factor of sensitivity. In northern food chains there is no milk production and little
cultivation of leafy vegetables, that would lead to significant uptake of 131I for children in temperate zones.
Again, the impact of 90Sr is expected to be less than that of 137Cs, which is bio-accumulated in Arctic food
chains.
There are also interactions between environmental sensitivity factors. For instance, the models used for the
agricultural scenarios (CHERPAC and FDMT-RODOS) show the effect on the activity in animal products
(e.g. milk) of the pasture activity decreases because of weathering; the activity in such food products
increases again when feed is switched to harvested grass.
The doses to individuals and populations are not only associated with the environmental conditions but
depend also on factors of social and economic nature such as the population living habits, food consumption
preferences, and agricultural practices. A first comparison between model predictions shows that agricultural
scenarios produces the largest doses for 137Cs in most cases. However, 137Cs in the Arctic environment can
also produce significantly elevated doses. The doses in marine environments tend to be much lower, even in
shallow coastal areas.
Results of calculations show that doses for the first year dominate the doses of the second and tenth year
after deposition. Doses also depend on groups of age. For example in the agricultural environment
CHERPAC predicts that the ingestion dose for 137Cs is higher for adults than other age groups, while for 90Sr
and 131I, the ingestion dose is highest for infants. The same applies to FDMT-RODOS, which predicts doses
from 90Sr higher for infants, as compared to adults or to 10 years old children.
4. Conclusions
The assessment of the radiological state of the environment following pollution depends on those pathways
of highest environmental sensitivity, related to climatic area, as well as anthropic management, social and
economic factors. The present study has confirmed the importance of the agricultural environment for the
assessment of doses from an accidental release of long-lived radionuclide 137Cs. A scale of radioecological
sensitivity is under discussion for the further activities of the group.
5. References
[1] Chouhan S.L., N.W. Scheier, and S-R. Peterson. 2011. CHERPAC, an environmental transport code, and its
predictions of environmental sensitivities in agricultural and forest ecosystems. Radioprotection, vol. 46, n◦ 6 (2011)
S515–S520, EDP Sciences, DOI: 10.1051 / radiopro / 20116784s.
[2] Müller H, Pröhl G 1993. ECOSYS-87: A Dynamic Model for Assessing Radiological Consequences of Nuclear
Accidents. Health Physics 64(3), 232-252.
[3] Sdouz G, Pachole M. 2006. Food chain data customization for decision support systems in Austria. Second European
IRPA Congress on Radiation Protection, 15-19 May 2006, Paris, France, TA8, 1-4.
[4] Müller H., Gering F. and Pröhl G. (2006). Model Description of the Terrestrial Food Chain and Dose Module FDMT in
RODOS PV6.0. RODOS(RA3)-TN(03)06.
http://www.rodos.fzk.de/Documents/Public/HandbookV6/Volume3/FDM_Terra.pdf
[5] Jige Shen., Don Hart. (2009). IMPACT (Integrated Model for the Probabilitic Assessment of Contaminant Transport)
User’s Manual version 5.4.0.
[6] Monte, L., Brittain, J.E., Gallego, E., Håkanson, L., Hofman, D., Jiménez, A., 2009. MOIRA-PLUS: A decision
support system for the management of complex fresh water ecosystems contaminated by radionuclides and heavy
metals. Computers and Geosciences 35, 880-896.
[7] Iosjpe M., Brown J. & Strand P., 2002. Modified approach for box modelling of radiological consequences from releases
into marine environment, Journal of Environmental Radioactivity, 60, 91-103
[8] Psaltaki M., Florou H., Trabidou G.,and Markatos N.C. « Modelling and assessment of pollutant impact on marine
environments», 2nd WSEAS International Conference on Computer Engineering and Applications (CEA ’10)
Harvard University, Cambridge USA, (p.p.176-180, January 27-29, 2010).
Table 1 could look like this
... The work continued under the International Atomic Energy Agency (IAEA) EMRAS II Programme (Environmental Modelling for RAdiation Safety) with Working Group 8 on Environmental Sensitivity. A preliminary report of this work was presented at the Sixth SETAC World Congress (Carini et al., 2012) and a full report is available from the IAEA (in press). A summary of the more significant findings is presented here. ...
Article
This paper describes modelling calculations carried out to determine the sensitivity of various rural and semi-natural environments to radionuclide contamination by (137)Cs, (90)Sr, and (131)I released during a major nuclear accident. Depositions of 1000 Bq/m(3) were assumed for each radionuclide. Four broad types of environments were considered: agricultural, forest or tundra, freshwater aquatic, and coastal marine. A number of different models were applied to each environment. The annual dose to a human population receiving most or all of its food and drinking water from a given environment was taken as a broad measure of sensitivity. The results demonstrated that environmental sensitivity was highly radionuclide specific, with (137)Cs generally giving the highest doses during the first year, especially for adults, in terrestrial and freshwater pathways. However, in coastal marine environments, (131)I and (239)Pu were more significant. Sensitivity was time dependent with doses for the first year dominating those for the 2nd and 10th years after deposition. In agricultural environments the ingestion dose from (137)Cs was higher for adults than other age groups, whereas for (90)Sr and (131)I, the ingestion dose was highest for infants. The dependence of sensitivity on social and economic factors such as individual living habits, food consumption preferences, and agricultural practices is discussed.
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