Identifying optimal agricultural countermeasure strategies for a hypothetical contamination scenario using the strategy model

doi:10.1016/j.jenvrad.2004.05.021

Journal of Environmental Radioactivity

Volume 83, Issue 3, 2005, Pages 383-397

https://doi.org/10.1016/j.jenvrad.2004.05.021 Get rights and content

Abstract

A spatially implemented model designed to assist the identification of optimal countermeasure strategies for radioactively contaminated regions is described. Collective and individual ingestion doses for people within the affected area are estimated together with collective exported ingestion dose. A range of countermeasures are incorporated within the model, and environmental restrictions have been included as appropriate. The model evaluates the effectiveness of a given combination of countermeasures through a cost function which balances the benefit obtained through the reduction in dose with the cost of implementation. The optimal countermeasure strategy is the combination of individual countermeasures (and when and where they are implemented) which gives the lowest value of the cost function. The model outputs should not be considered as definitive solutions, rather as interactive inputs to the decision making process. As a demonstration the model has been applied to a hypothetical scenario in Cumbria (UK). This scenario considered a published nuclear power plant accident scenario with a total deposition of 1.7 × 10¹⁴, 1.2 × 10¹³, 2.8 × 10¹⁰ and 5.3 × 10⁹ Bq for Cs-137, Sr-90, Pu-239/240 and Am-241, respectively. The model predicts that if no remediation measures were implemented the resulting collective dose would be approximately 36 000 person-Sv (predominantly from ¹³⁷Cs) over a 10-year period post-deposition. The optimal countermeasure strategy is predicted to avert approximately 33 000 person-Sv at a cost of approximately £160 million. The optimal strategy comprises a mixture of ploughing, AFCF (ammonium-ferric hexacyano-ferrate) administration, potassium fertiliser application, clean feeding of livestock and food restrictions. The model recommends specific areas within the contaminated area and time periods where these measures should be implemented.

Introduction

Following a nuclear accident, rural environments may be contaminated for many years. To protect the population, effective restoration strategies must be developed. To do this, decision makers must consider many factors, such as the radioecological, environmental, economic, and social conditions in the affected area. However, nuclear emergency planning often focuses on short-term (days–weeks) responses and does not consider longer term (months–years) restoration strategies. Ideally, these mid-long term strategies should be considered during the early phase after an incident, as decisions made then may have consequences for the future management of the affected area.

There are a number of alternative countermeasures that could be applied following a release and these vary in their effectiveness, mode of operation and cost. Moreover, environmental, agricultural, social and economic conditions can vary across an affected region. Therefore, selecting the optimal combination of countermeasures and determining when and where they are best applied is a complex task. The combination of Geographical Information Systems (GIS), radioecological models, and information about the effects of various radiological countermeasures presents the possibility of computationally assessing the consequences of restoration strategies. The aim of such a model should be to help select actions that reduce doses from radiation to ‘as low as reasonably achievable’ (ICRP, 1973) and produce a net benefit (i.e. the difference between the monetary value of the averted dose and the costs incurred by the action (ICRP, 1988)), while recognising that in reality decision makers will have to consider a wider range of social impacts of both contamination and the countermeasure strategy.

In this paper we describe a model which is designed to assist decision makers in identifying optimal agricultural countermeasure strategies under user-defined conditions. To illustrate the use of the model we present results of a case study application to a hypothetical scenario in Cumbria (NW England).

Section snippets

Model overview

The approach described here is fully described by Cox and Crout (2003) (available from www.strategy-ec.org.uk/output/outputs.htm) and is summarised here.

The overall spatial representation of radionuclide transfer is an evolution of the model for radiocaesium described by Gillett et al. (2001). The area under study is divided into a two dimensional array of grid squares so that the spatial variation in model inputs and outputs across the region can be represented using a raster-based GIS

Data sources for Cumbrian scenario

A grid square resolution of 25 km² (5 × 5 km) was used giving a total of 271 grid squares for the study area (the county of Cumbria).

A simple deposition pattern was created using a source term derived from Kelly and Clarke (1982) who described potential releases from a pressurised water reactor degraded core accident (Fig. 1). This provides a realistic, large-scale accident. However, it should be noted that this is deliberately hypothetical as this type of reactor site is not present in the study

Results

The model was used to investigate 3 remediation options:

•
“Do nothing”. No countermeasures were implemented.
•
“Food restrictions”. Food restrictions were implemented at the recommended CFILs. No other countermeasures were implemented.
•
“Optimal”. The implementations of selected countermeasures were optimised as outlined earlier. Food restrictions were also implemented at the recommended CFILs as above.

In each case, simulations were performed for a period of 0–10 years after the deposition event. This

Discussion

Countermeasure optimisation suggests a set of countermeasures which are an improvement over the sole use of food restrictions; the radiation protection outcome is similar but is achieved at a much lower cost. The countermeasures selected are focussed on reducing the activity concentrations of lamb and beef in particular.

These results suggest that ploughing is the agricultural countermeasure of first choice. It is relatively cheap and effective, and in the simulations presented here it is

Acknowledgements

The STRATEGY project was conducted under a contract (FIKR-CT-2000-00018) within the research and training programme (Euratom) in the field of nuclear energy, and this support is gratefully acknowledged. The paper is the sole responsibility of the authors and does not reflect Community opinion, and the Community is not responsible for any use that might be made of data appearing in this publication. We also wish to acknowledge the contribution of all the STRATEGY project members and the comments

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This cost-free experimentation is advantageous given the high cost and repercussions associated with certain strategies (e.g. changing agricultural practices or land use) (Fesenko et al., 2013). Coupled to spatially distributed agricultural and human diet data, radioecological models have extensively been used in Europe following the Chernobyl accident to predict long-term contamination of agricultural produce, identify areas with enhanced radionuclide transfer to food chains and propose remediation strategies (van der Perk et al., 2000, 2001; Cox et al., 2005; Gillett et al., 2001; Jacob et al., 2009; Gering et al., 2010; Fesenko et al., 2013). Decisions concerning the need of remediation and selection of the remediation strategy are quite complex because several factors such as the radiological relevance, technical feasibility, socio-economic factors (e.g. economical cost, cultural heritage, ecosystem services) have to be considered.
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Numerous radioecological models have been developed to predict radionuclides transfer from contaminated soils to the food chain, which is an essential step in preparing and responding to nuclear emergencies. However, the lessons learned from applying these models to predict radiocaesium (RCs) soil-to-plant transfer following the Fukushima accident in 2011 renewed interest in RCs transfer modelling. To help guide and prioritise further research in relation to modelling RCs transfer in terrestrial environments, we reviewed existing models focussing on transfer to food crops and animal fodders.
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Gillett et al. (2001) applied it to spatial predictions for England and Wales. Cox et al. (2005) used the model within an approach for the optimisation of long-term countermeasure management. Simon et al. (2002) found that the model was not applicable to the carbonate soils of the Marshall Island atolls and their vegetation, indicating that the model cannot necessarily be applied outside the range of conditions for which it was developed.
An existing model of radiocaesium transfer to grasses was extended to include wheat and barley and parameterised using data from a wide range of soils and contact times. The model structure was revised and evaluated using a subset of the available data which was not used for model parameterisation. The resulting model was then used as a basis for systematic model reduction to test the utility of the model components. This analysis suggested that the use of 4 model variables (relating to radiocaesium adsorption on organic matter and the pH sensitivity of soil solution potassium concentration) and 1 model input (pH) are not required. The results of this analysis were used to develop a reduced model which was further evaluated in terms of comparisons to observations. The reduced model had an improved empirical performance and fewer adjustable parameters and soil characteristic inputs.

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View full text

Identifying optimal agricultural countermeasure strategies for a hypothetical contamination scenario using the strategy model

Abstract

Introduction

Section snippets

Model overview

Data sources for Cumbrian scenario

Results

Discussion

Acknowledgements

J. Environ. Radioact.

J. Environ. Radioact.

Council Regulation (Euratom) No. 2218/89 amending Regulation (Euratom) No. 3954/87 laying down maximum permitted levels of radioactive contamination of foodstuffs and feedingstuffs following a nuclear accident or any other case of radiological emergency

Official Journal of the European Communities

Temporal and spatial prediction of radiocaesium transfer to food products

Rad. Environ. Biophys.

Sustainable restoration and long-term management of contaminated rural, urban and industrial ecosystems

Radioprotection Colloques

The land cover map of great britain: an automated classification of landsat thematic mapper data

Photogramm. Eng. Remote Sens.

Implications of commission recommendations that doses be kept as low as readily achievable. ICRP 22

Optimisation and decision-making in radiological protection. ICRP 55

Recommendations of the ICRP. ICRP 60

The monetary value of the averted dose for public exposure assessed by the willingness to pay

Health Phys.