Risk Based Land Management and Sustainable Rehabilitation of Radioactive Contaminated Territories

Decision-Making Support within Risk Based Land Management and Sustainable Rehabilitation of Radioactive Contaminated Territories

B.Yatsalo *), I.Okhrimenko *), I.Pichugina *) O.Mirzeabassov *), V.Didenko *), D.Okhrimenko*), V.Golikov #), G.Bruk #) and V.Shutov #) 1) [email protected]

ABSTRACT Description of the applied Decision-Support System (DSS) PRANA for Risk Based Land Management (RBLM) and rehabilitation of radioactive contaminated territories is presented. PRANA is a unique DSS developed with the use of GIS technologies which comprises all the main territories of Russia subjected to radioactive contamination as a result of the Chernobyl accident (Bryansk region) and includes all the models and tools necessary for decision-making support on local and regional levels within RBLM and rehabilitation of contaminated territories. Examples of PRANA implementation for scientific and practical assessments are considered.

Keywords: radioactive contamination, radiation protection, risk based land management, rehabilitation, doses, countermeasures, GIS, decision support systems, PRANA DSS.

INTRODUCTION Despite improvement of the radiological situation for the 16 years after the Chernobyl accident, the latest monitoring data and assessments demonstrate that the situation on the contaminated territories of Bryansk region (Russia) is far from satisfactory. Fraction of milk for 5 districts of Bryansk region with contamination above formal action level exceeded in 2001 20% (for Novozybkov district - 60%); about 50% of the rural population live in settlements with a mean dose above 1 mSv/y (formal dose level for exemption from intervention). As a rule, contamination of private agricultural produce, which constitutes the majority of foodstuffs of the local population, substantially exceeds contamination of farm produce. This is caused by use of more contaminated lands for farming private production and fewer protective measures. Model estimations demonstrate that optimization of agroecological and administrative countermeasures along with enhancement of the skills of living on contaminated territory can considerably decrease contamination of agricultural production and doses to the local population. In this condition implementation of up-to-date information technologies for decision-making support on risk based land management (RBLM) and optimization of countermeasures (CMs) within the programs on rehabilitation and sustainable development of contaminated territories is more than actual [1-4].

PRANA DSS for RBLM and COUNTERMEASURE OPTIMIZATION Analysis of the current situation in contaminated farms and settlements of Bryansk region is based on the monitoring data and model estimates. Model assessments of agricultural produce contamination, doses to the local population, radiological risk and results of CMs implementation have been carried out with the use of PRANA GIS-DSS [3,4,9]. Applied Geographic Information System (GIS) PRANA is a DSS for rehabilitation of radioactive contaminated territories. The following versions of DSSs have being developed (family of PRANA systems, each of them is intended for analysis of the specific range of problems): - PRANA-P - GIS-DSS for practical use within decision-making support on rehabilitation of radioactive contaminated territories of Bryansk region on regional and local levels; PRANA-P consists of the following sub-systems, which may be used independently: PRANA-DB-Analysis, PRANA-Agro and PRANA-Dose; - PRANA-R - GIS-DSS for research and for scientific and practical estimations (this version of PRANA comprises all the possibilities of the systems indicated above along with some additional

1) *) Obninsk State Technical University of Nuclear Power Engineering, Obninsk, Russia #) Institute of Radiation Hygiene, St.-Petersburg, Russia 2 applications, including block of CMs optimization and uncertainty analysis and has completely new architecture); - PRANA-E/T GIS-DSS for education and training of students and experts. PRANA-P has been introduced for practical use in Bryansk (as well as for scientific and practical assessments at several institutes and centres) as a GIS-DSS for monitoring networking support, assessing radiation indices and countermeasure analysis. The main blocks of PRANA DSSs are: - libraries of digital maps, including different layers of vector maps of landuse for all contaminated districts of Bryansk region: Novozybkov, Klintsy, Gordeevsky, Krasnogorsky, Zlynkovsky and Klimovsky (more than 30000 polygons of vector electronic maps), Fig.1; - databases (radioecological, ecological, economic, demographic and other monitoring data and model parameters, including attributive information for each polygon of vector electronic maps); - model blocks for assessing: contamination of agricultural production, external and internal doses to the local population, radiological risks and corresponding results of CMs implementation; - evaluation of CMs effectiveness and decision-making support on protection of the population and rehabilitation of radioactive contaminated territories both on local and regional levels (from separate settlement/field up to group of settlements/farms and district/region as a whole), [4, 5].

FiFigg..1.1. LaLandndususee mmaapp Landuse types: ffoorr 66 ddiissttririccttss settlement ofof BBrryayansnskk rreegigionon arable natural lands forest fallow land bushes marsh reservoir Structure of other land agricultural lands % for 6 districts 80 70 70 60 50 40 30 18 12 20 10 0 Arable lands Pastures Hayfields

Klintsovsky district % 69,5 70 60 50 40 30 20,3 20 10,2 10 0 Arable lands Pastures Hayfields

The following (generic) ‘risk indices’ are considered within RBLM and decision-making support with the use of PRANA DSS: - surface density contamination of territory with radionuclides (137Cs, 90Sr); - contamination of agricultural production (plant growing and animal husbandry, including farm and private production); - external and internal doses to the local population (mean doses and doses for different age and occupational groups of each settlement for region under consideration); - radiological risks caused by irradiation of the population; - and expenses associated with CMs implementation and rehabilitation procedures along with corresponding criteria of effectiveness on the basis of CBA analysis. 3 Special attention is paid to estimation of agricultural produce contamination for each agricultural field, farm (farm production) and settlement (private production) taking into account farm specialization (real data on crop rotation and cattle stock) and particularity of private farming. Ranking fields, farms, settlements and districts has been carried out with the use of several criteria: surface density contamination (including separately for arable lands, pastures and hayfields), contamination of a given product, dose to the local population and percent of exceeding corresponding DILs/ILs by indicated values. Realization of radiological protection principles includes solving the following tasks within the work package on optimization of CMs structure. 1) (Research task) Analysis of effectiveness (for a given set of criteria) for each CM for various radiological, ecological, socio-economic and other conditions. 2) (Direct task) Determination of the specific territories/objects (fields, settlements, farms) for a given region where CMs can be or should be implemented according to a strategy of rehabilitation; determination of corresponding means (cost, materials, etc.); assessment of effectiveness for each CM and system of CMs for site-specific conditions; analysis of alternatives. 3) (Inverse task) Taking into account the set of available CMs and objects of possible implementation of CMs (agricultural fields, settlements), experts have to chose such their subset, that realization of the chosen CMs on chosen objects/polygons provides an optimal value for a given criteria and satisfies conditions of financial and other (ecological, economic, etc.) restrictions/constraints. Decision-making support on the basis of different versions of GIS-DSS PRANA on rehabilitation of radioactive contaminated territories (including managing farm production and decreasing doses to the local population using different agricultural and administrative countermeasures) can be carried out both on local and regional levels. Such an approach is realized through presentation of source data and various model estimates on the level of: - separate agricultural field (including each arable field, pasture/hayfield); - a set of agricultural lands (e.g., for fields under a given crop or for specific soil types, for pastures/hayfields, or for any group of agricultural lands indicated by user); - a settlement or a group of settlements; - farm or a group of farms; - specific administrative district, a group of districts or the whole contaminated territory (of Bryansk region). At that, for each level of decision-making support source/modelled information can be presented for users/experts/decision-maker as - electronic map(s); - table(s); - graphic(s)/diagram(s). On the basis of PRANA DSS all the main source and derived maps (along with corresponding statistical characteristics) which are used within agriculture managing, assessing the structure of doses to the local population, protective measures planning and, as a whole, within rehabilitation of radioactive contaminated territories, can be presented. The most claimed within the indicated problematic are the following source maps with corresponding statistical data: - landuse (see Fig.1); - surface density contamination (Fig.2); - soil types; - physical and chemical soil composition (contain of potassium, phosphorus, humus, pH); - previous, current and planned crop allocation on agricultural fields (crop rotation); - history of countermeasures (which, where and when CMs were implemented before); - internal, external and total doses to the local population (mean dose for a settlement in accordance with formal monitoring data); - some other maps with presentation of attributive information for different polygons of landuse map.

4 MODEL ASSESSMENTS The following model assessments can be carried out based on the use of PRANA DSS (as well as with the use of stand-alone computer systems associated with the PRANA DSS and intended for qualitative and quantitative analysis of risk indices): - estimations of agricultural produce contamination (for given years) for each field and thorough analysis of various scenarios of farming for all the critical farms; analysis of CMs structure which should be or can be implemented; - assessments of internal and external doses to the local populations for all the settlements of 5 contaminated districts of Bryansk region for a given year (mean doses and doses for critical groups); analysis of the dose structure; contribution of different foodstuff to internal/total dose; - ranking settlements and farms (fields) according to risk indices;

Fig.2 Surface density contamination for 5 districts of Bryansk region, 137Cs, 1999 (monitoring and modelled (with the use of geostatistics) data ). - analysis of polygons, where CMs can or should be implemented in accordance with the existing standards,

137 2 requirements and restrictions, and assessments of the Cs (Ci/km ) results of countermeasure implementation (contamination of agricultural produce and structure of doses for different scenarios and countermeasure effectiveness on the basis of CBA analysis); - analysis of produce contamination and doses in dynamics; - radiological risk analysis; - uncertainty analysis. All the results are presented as maps, histograms, graphics and tables for subsequent analysis and decision-making. Inhomogeneous character of surface density contamination of territories after the Chernobyl accident (see Fig.3) and tasks of assessing the realistic doses to the local population require using the overall information on contamination in and out of a settlement along with information on land use, soil types, population behaviour/habits and many other data. Effective integration of heterogeneous data for estimating contamination of agricultural produce, internal and external population doses and the results of countermeasure implementation can be achieved due to use of GIS. Such an applied GIS 137 Fig.3 Ratio of average weighted contamination of natural lands ( Cs) in can be used as an information a settlement vicinity to the average contamination in a settlement (data for support system (spatial all rural settlements (465) in 5 districts of Bryansk region). distributed database) and as a consisting part of a DSS

30 24 % 25 % intended for analysis of a wide range of tasks/scenarios on 25 19 % % of assessing the consequences of an settle ments 15 % 20 14 % accident and analysing corresponding protective 15 measures. An example of direct task 10 3 % analysis (see above) within CMs

5 optimization is presented in Fig.4 (location of CMs for 0 (0-0,7] (0.7-1] (1-1,3] (1.3-1,7] (1.7-3] >3 pastures and hayfields in accordance with requirements of the SanPin-2001 standard).

Fig. 4. Map, wheerre CMs should bebe impleemmeentnted: DIL=SanPin-2001 (Novozybkov district, Bryansk region, 2003)

CMs needed CMs on arable CMs on natural land

Landuse arable natural land other land

5656%% 44% No CMCMss oonn nanattuurraall lalandsnds DILL Cosstt AvAveerrttaabbllee ddososee Coosstt-e-effffeecctivtiv--ss ((PPcc),), [[k$k$]] ∆∆SS [[mamannSvSv]] ee== PPc //∆∆SS [[k$k$//mmaannSvSv]] CMss nneedeededed oonn c nanattuurraall lalandsnds SanSanPPiinn--22000011 10105050 3030 3535 (1(10000 BBqq/l)/l)

Dose block is a key component of the PRANA GIS-DSS on rehabilitation of radioactive contaminated territories after the Chernobyl accident. When estimating internal and external doses to the local population the following components of PRANA are used: - electronic maps for territories under investigation; - databases (including attributive information with polygons of vector electronic maps, and database for model and other input parameters); - updated and modified models for assessing external and internal doses to the local population (from 137Cs and 90Sr); - corresponding computer modules and user interface. The basic model of external exposure (from 134,137Cs) consists of four sub-models for the following issues [6-8]: - absorbed dose rate in air at a reference site; - conversion factor from absorbed dose rate in air to effective dose rate; - absorbed dose rate in air at various types of rural or urban locations relative to the reference site; and - occupancy times of different population groups at various types of locations. The basic model of internal exposure (from 137Cs and 90Sr) consists of sub-models for assessing contamination of the main foodstuffs. The following information (for the time period under consideration) is used for estimation of mean effective internal dose (reconstructed or forecasted) to the local population [3,5]: - monitoring data of internal doses, demographic data; - the structure of population diet for a given settlement; - monitoring data on surface density contamination (with radionuclides 137Cs and 90Sr) for a settlement and its neighbourhood (including contamination of pastures and hayfields and forests); - data on type of soil (first of all for pastures, hayfields and arable lands), animal rations and various transfer factors; - monitoring data or model estimates on contamination of the diet components (private and farm milk, meat, potato, mushrooms and berries, game and fish), and other radiological parameters and constants. Adjusting source dose models to elements of GIS considerably extents their possibility and creates in fact new updated and extended models. One of the key features of dose models indicated is an 6 active use of landuse map in combination with soil contamination map and the map of human behaviour in a vicinity of the settlement under consideration. Numerical values of inhomogeneity for contamination of rural settlements and vicinities are presented in Fig.3. This histograms reflects one of the possible discrepancies in dose assessing (including difference in estimating contamination of milk and other diet components) when using data on contamination for a settlement only and for entire vicinity. Integration of models and GIS allows estimating various scenarios of the local population behaviour, consumption of locally produced or gathered food and implementation of a wide range of CMs. The possibility of using distance function as well as direct connection of landuse polygons with a settlement is especially important when assessing contribution of milk and forest products into individual effective dose to the local inhabitants. Such an approach comprises also analysis of various scenarios of different CMs implementation for specific fields/pastures, including management on the use of contaminated territories (e.g., excluding pastures/hayfields with high contamination of grass for practical use, or use of previously abandoned fields, etc.).

Fig.5 Years when mean dose to the population in settlements becomes less then 1 mSv/y.

An example of model assessments is 47 % of rural population presented in Fig.5. According to the assessments average effective dose to the 15 15 137 10 11 2 population (from Cs) for more then 20% rural settlements will exceed 1 mSv/y (formal action level) during 20 forthcoming years (if no CMs are implemented). It Years should be noted that contribution of 90Sr in <= 2004 total dose does not exceed 2-3%. 2005 - 2010 Source dose models have been 2011 - 2015 2016 - 2025 extended to multilevel adaptive dose 2026 - 2040 models (the basic parameters can be 2041 - 2071 adjusted/localised using monitoring data for the settlement under investigation) and to probabilistic dose models (the basic 36 % of settlements parameters can be considered as 18 17 distributed/random values) for uncertainty 13 12 4 analysis (see, e.g., Fig.6).

Fig.6 Model assessments: dynamics of effective dose (mean dose with 90%-confidential interval) without countermeasures for the settlement Khalevichi, Novozybkov district (490 inhibitions, surface density contamination 735 kBq/m2).

External+Internal dose

4.5

3.5 ) /y

v 3 S m ( e

2.s 5 o D 2

1.5

0.5

2 005 2 010 2 015 2 020 2 025 2 030 2 035 2 040 2 045 2 050 Year (y) 7

CONCLUSION Based on the developed GIS-DSS PRANA all the main source data and model estimates which are necessary within risk based land management, optimization of the structure of protective measures and rehabilitation of radioactive contaminated territories can be presented for decision-making support both on local (field, settlement, farm) and regional (administrative district, region as a whole) levels for all the territories (6 districts) of Bryansk region, subjected to radioactive contamination after the Chernobyl accident. This includes: - maps and attributive information for all the elements of land use (including monitoring data of radiological, agroecological and other monitoring networks); - model assessments (various scenarios, including dynamics) of - agricultural and other produce contamination; - external and internal doses to the local population; - radiological risks; - results of countermeasure implementation (various scenarios for wide range of agricultural and administrative CMs application); - effectiveness of CMs for different criteria (radiological and economic indices, CBA); - decision-making support through preparation and corresponding presentation of source/modelled information for experts of local and regional levels. Different versions of PRANA GIS-DSS have been introduced for practical implementation, scientific and practical assessments and for education and training students and experts. This work has been carried out by a team of scientists from Russian Institutes (RRC KI, OINPE, IRH, BCAR) within an ISTC project.

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