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Ranking the sites for low- and intermediate-level radioactive waste disposal facilities in Croatia
Int. Trans. Opl Res. Vol. 4, No. 4, pp. 237-249, 1997
Pergamon
so969--6ol~97)oooo3-s
1997 IFORS. Published by EIsevi©rScience Ltd All rights reserved. Printed in Great Britain 0969-6016/97 $17.00 + 0.00
Ranking the Sites for Low- and Intermediate-Level Radioactive Waste Disposal Facilities in Croatia JOSIP C.E. PETRA~ University of Zagreb, Croatia This paper describes the procedure of identification and ranking of the potential sites for LILRW disposal facilities in Croatia. It presents preliminary results of the final phase of the site survey stage, i.e. preliminary comparison and ranking of potential sites. The potential sites were chosen on the basis of exclusionary (rejection) criteria, and the preliminary ranking of the sites was performed on the basis of comparative preference criteria by the multicriteria analysis approach PROMETHEE. The list of exclusionary and comparative criteria is given, and the weighting factors of comparative criteria are presented. © 1997 IFORS. Published by Elsevier Science Ltd.
Key words: Siting, radioactive waste disposal, procedure, exclusionary criteria, comparative criteria, weighting factors, preferences.
INTRODUCTION In the process of preparing the Urban and Land Use Plan (ULUP) of Croatia in the year 1990, among other study documentation, the study: "Site Survey Stage of the Siting Process for Low- and Intermediate- Level Radioactive Waste disposal facilities" (LILRW) was made. This study was a part of the bigger study: "Site Screening Investigation and Assessment of Site Suitability for Fossil Fuel Power Plants and Nuclear Facilities on the Territory of the Republic of Croatia" The author of this paper was a member of the team which made the LILRW study. The objective of the study was to identify suitable sites for the LILRW repository and make a preliminary ranking list of these sites. It was planned that the study would be discussed in the State Parliament twice: --for the approval of criteria and methodology, and --for the approval of its results, i.e. the proposed preferred sites to be included in the ULUP. The first discussion was held at the end of 1990, and in January 1991 the Government of Croatia published the booklet with the result of the work done by that time. The purpose of the publication was to inform the public on the proposed methodology and siting criteria. The proposed methodology and criteria for the LILRW repository were reviewed and positively assessed by the International Atomic Energy Agency (IAEA) Radioactive Waste Management Advisory Programme (RWAMAP) mission in Croatia and Slovenia, in April 1991. Further work on the study was interrupted because of the beginning of the war in Croatia. Now the war has ended, the activities are continuing.
THE PROCEDURE OF SITE SELECTION FOR LILRW REPOSITORY IN CROATIA The site selection for the LILRW repository in Croatia, a complex task, has to be in compliance with national and IAEA regulations. The basic law that regulates this subject as well as the conditions for using other legislation and standards is the"Act on Radiation Protection and the Safe Use of Nuclear Energy". According to this Act, all regulations relevant to LILRW repository siting were considered in the first phase of the selection process in Croatia. The process involves three basic steps: 1. Site survey stage, i.e. regional and site(s) screening studies, having as primary objective the inclusion of preferred sites in the "ULUP of Croatia"; 2. Modifications and supplements to the ULUP defined on the basis of the Parliament decisions on the inclusion of preferred sites in the ULUP;
Correspondence: Josip C.E. Petrag, Faculty of Civil Engineering, University of Zaffreb, Croatia
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THE WHOLE TERRITORY 3 OF CROATIA J
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Fig. 1. Procedureappliedin the LILRW repositorysite selectionCroatia.
3. Licensing procedures for site permits (including site evaluation and site confirmation stages of the siting process) on the basis of necessary investigations and studies. The first of these three steps is the subject of this paper. The procedure applied m this step is shown in Fig. 1. It is developed on the principles of"Problem solving technology" (Berakovi~ et al., 1986). In methodological sense, the procedure consists of two basic phases: Phase I: Regional Analysis of the Territory of the Republic of Croatia and Selection of Potential Regions (Areas) Phase II: Identification of Potential Sites and Selection of Preferred Sites. In Phase I, the whole territory of Croatia was analysed. This was performed by using the exclusionary (rejection) criteria method (exclusionary screening). The areas that were unacceptable on the basis of at least one characteristic were rejected. The remaining areas were designated as potential areas or further analysis. The bases for applying exclusionary criteria in this phase were appropriate topographic and other
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specialized maps of Croatia, mostly in the scale 1: 300,000, as well as the existing data corresponding to the selected scale. In Phase II, all the potential areas remaining after Phase I were checked on the compliance with the exclusionary criteria applied on the basis of more detailed data and maps (in the scale 1: 100,000). Comparative preference criteria were then formulated and applied to potential areas in order to identify and select potential sites. The same criteria, but with more detailed data and investigations, were also applied for ranking potential sites in order to select several preferred candidate sites. This task is divided into three subphases as follows:
( A ) Selection of parameters and criteria In this subphase the proposed parameters and criteria used in the identification, selection and comparison of potential sites were formulated by a team of experts composed of specialists from various relevant fields described below.
( B) Assessment of potential areas and identification of potential sites During this subphase, the potential areas from Phase 1 were divided into smaller, relatively homogeneous areas. The identification and assessment of such homogeneous smaller potential areas was performed by applying:
(a) Exclusionary criteria. Supplemented and revised exclusionary criteria from Phase I, completed by a map survey in scale 1 : 100,000, (b) Comparative criteria. As a basis for the identification of potential sites. The comparison of a great number of those areas and the selection of more suitable ones was performed by computer program--using the multicriteria analysis approach PROMETHEE (Brans et al., 1986; Mladineo, 1990). In the selected smaller areas the potential sites were identified by using topographic maps in the scale 1:25,000 and data on certain comparative criteria. ( C ) Comparison of potential sites and selection of preferred candidate sites In this subphase, the assessment and comparison of potential sites was performed by using the selected PROMETHEE program for multicriteria analysis. The result of the analysis in this subphase is in fact the final result of the whole study and its primary objective, i.e. the selection of several referred candidate sites, will be presented for the initiation of procedures for the amendment and supplement of the ULUP.
PRINCIPLES OF FORMULATING EXCLUSIONARY CRITERIA Exclusionary criteria were formulated by a team of experts. This team was formed after the consideration of all relevant regulations to LILRW repository siting. The members of the team were scientists and experts in the field of different technical, natural, and social disciplines. In the procedure of formulating exclusionary criteria, different viewpoints and principles for formulating these criteria were analyzed first. The principles were adopted as follows:
(a ) Viewpoint of economics of engineering solutions for a LILR W repository The areas in which it is not possible to meet the necessary technical/technological requirements or where the engineering solution of repository construction and operation would be highly uneconomical (e.g. seismo-tectonics area) need to be rejected.
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(b) Viewpoint of safety requirements The areas where it is not possible to meet safety requirements defined by law, as well as the areas where those requirements would be met mainly by applying engineering solutions, have to be rejected (e.g. hydrological characteristics).
(c) Viewpoint of land use in closer and wider site area of repository The areas where the present and planned land use in the closer or wider site area would be in significant conflict with LILRW repository operation need to be rejected (e.g. high population density, natural amenities, etc.).
REVIEW OF EXCLUSIONARY CRITERIA On the basis of the quoted principles and significant factors of repository site in Table 1 the review of the exclusionary criteria is presented (Study, 1991). In formulating these criteria, the following aspects were taken into consideration: I. transportation, 2. hydrologic aspects, 3. geology and seismology, 4. demography, 5. present and planned land use, 6. environmental protection. Taking these aspects into consideration the following exclusionary criteria were formulated: E.2.1. Flooding: All natural floodplain areas (return period of 1000 years) are rejected, regardless of whether they are protected or not. E.3.1.1. Seismotectonics: The areas with maximal potential earthquake intensity of the IX or over IX degree on the commonly used MCS scale are rejected. E.3.1.2. Neotectonics: The areas in zones having identified faults are rejected. E.3.2. Lithological and geomorphological characteristics: The areas having increased erosion rate caused by iithology or relief dynamics as well as the areas composed of rocks unstable under natural conditions (weathering, etc.) and by construction activities are rejected for shallow ground type of repository. - - F o r tunnel-type of repository the areas exhibiting land-sliding and rock-falling are rejected, if that poses hazard to repository structures. [The tunnel-type of LILR W repository means the digging of disposal tunnels in hard rocks (mainly in granites) as stable, shallow geological structures. In such tunnels immobilized radwaste is being disposed in metal drums that are placed in concrete boxes which are finally filled up with fresh concrete mass.] E.3.3. H ydrogeology--protection of water-bearing layer (aquifer): --The areas containing protected sources of potable water accordng to "The Regulations on Protective Measures and Conditions for Determining Zones of Sanitary Protection for Sources of
Table 1. List of exclusionary criteria Environmental acceptability Aspects of the site selection procedure I. Transportation 2. Hydrologic aspects 2.1. Flooding 3. Geology and seismology 3.1. Seismotectonics Neotectonics 3.2. Lithology and geomorphology 3.3. Hydrogeology 4. Demography 5. Present and planned land use 5.1. Special purposes 5.2. Mining and mineral exploitation 6. Environmental protection 6.1. Natural heritage protection 6.2. Cultural heritage protection
Economics engineering
Safety
Vicinity area
Wider area
E.2.1. E.3,1.1. E3.1.2. E.3.2. E.3.3. E.4.0.
E.5.I. E.5.2. E.6.1. E.6.2.
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Potable Water" are rejected. - - F o r the purpose of protecting water, a disposal facility site cannot be located in an area having significant water-bearing layer (aquifers) of any type. E.4.0. Population density: The areas having a cumulative population density of more than 80 inhabitants per sq. km within a 20 km radius from repository site are rejected. E.5.1. Special purposes: The areas designated for special purposes, including protected zones, are rejected. (Some areas have special land use and protection status regarding national defense.) E.5.2. Mining and minerals exploitation: The areas in zones of present or future mining and exploitation of minerals, gas, oil, coal, etc. are rejected. E.6.1. Natural heritage protection: National parks, natural parks and other significant natural amenities are rejected. E.6.2. Cultural heritage protection: The areas having cultural amenities registered in the List of World Cultural and Natural Heritage as well as those having other cultural amenities of great importance for the entire community are rejected. According to each group of thexe exclusionary criteria, the screening analysis of the whole territory of Croatia was made, and the results were given on maps in the scale 1 : 300,000. Based on all collected results, 12 potential areas, situated in the central and east part of Croatia were selected. In these areas there are many possibilities for LILRW repository siting. These possibilities were analysed in Phase II of the site selection process.
PRINCIPLES OF FORMULATING COMPARATIVE CRITERIA Comparative criteria were formulated by the same team of experts which formulated the exclusionary criteria. Comparative criteria are usually presented in the form of requirements for achieving a certain goal or a desired state. These goals can be defined as ideal (desirable) conditions, and if an ideal condition cannot be achieved, the criteria have also to describe the degree of acceptability. The comparative criteria were formulated from the same points of view like the exclusionary criteria, i.e. engineering aspects, safety-related aspects, environmental impact and acceptability in the closer site area and in the wider site area.
(a) Engineering aspects Preference has to be given to the sites which enable simpler and thus more economical engineering solutions. The analysis of site characteristics has to be made, and the sites which enable less expensive engineering solutions are to be preferred.
(b ) Safety-related aspects Sites are more suitable where safety is based upon better natural characteristics, requiring the minimum of engineering interventions. The analysis has to be made of whether the safety requirements for the construction and/or operation of the waste disposal facility are met. The preference is to be given to the sites having better natural safety.
(c ) Environmental impact and acceptability in closer site area The public acceptance of potential sites depends heavily on the environmental impact of the repository. It is therefore very important for the phase of preferred sites identification and selection to consider and analyse all the aspects of possible environmental aspects, and to formulate on the basis of such comprehensive considerations the comparative criteria which refer to environmental protection. Following the domestic legal provisions and international recommendations which refer
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to the management of radioactive waste (contained primarily in I AEA--International Atomic Energy Aoency--documents), the expert team in Croatia has considered the following aspects: natural
heritage protection, cultural heritage protection, soil properties, biological and ecological values, and radiologieal aspects. In connection with these aspects, the following principles for the comparative criteria formulation referring to the acceptability in closer site area were defined: --Preference has to be given to the natural site characteristics which provide a lesser environmental impact, as well as to the present and planned land use that ensures better safety and acceptability of the site. The analysis has to be made on whether the safety requirements are met concerning the impact of the facility on the immediate environment. Emphasis is placed upon impact during regular disposal operations as well as in the cases of possible accidents. The characteristics of the site can also affect the degree of social acceptance. Therefore, --the sites having better natural characteristics and with minimum requirements on engineering interventions are more suitable and have to be preferred. Also, --the sites where it is possible to anticipate less conflict with other users of the area are more suitable. (For this group of criteria in Croatia the analysis and comparison of characteristics of the area surrounding a potential site within a radius of approx. 5 km were performed).
(d) Acceptability o['the site (]acility ) in wider .site area Related to the previously mentioned aspects of LILRW repository impact on the environment, the following principles for the comparative criteria formulation referring to the acceptability in wider site area were defined: --Preference has to be given to natural site characteristics which provide fewer conflicts in wider site area, concerning the impact of regular disposal operations on present and planned land use. The analysis has to be made on the possible impact of the waste disposal facility on the wider site area. Emphasis is placed upon the analysis of the present and planned land use as well as the degree of social acceptance regarding possible changes in the value of the area. Due to that, --the sites where it is possible to anticipate fewer conflicts with the present users of the area are more suitable and have to be preferred. (For this group of criteria in Croatia the analysis and comparison of characteristics of the area surrounding a potential site within a radius of approx. 20 km were performed.)
REVIEW OF COMPARATIVE CRITERIA On the basis of the quoted principles and significant factors of repository site in Table 2 the review of ratings/scores of comparative criteria is presented (Study, 1991). In the formulating of these criteria the following aspects were taken into considerations:
A.3.1. Seismotectonics and seismic--seismic activity More suitable sites are those where the earthquake activity is expected to be of smaller intensity. Scaling method: maximum horizontal acceleration of ground oscillations for earthquake has been calculated on the basis of earthquake intensity. According to this acceleration potential sites are ranked by scoring in the range 0-100%.
A.3.2. Soil mechanics Less suitable sites are those where less favorable natural conditions (unsuitable slope inclination, surface soil layer having unsuitable geomechanical characteristics with lower permitted load properties) are present at the site. Scaling method: potential site has been evaluated on the basis of expert opinion respecting
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morphologic characteristics (slope inclination), lithological properties, permitted basement load and seismic characteristics. Potential sites are ranked in 1-10 range categories. B.2.1. Hydrologic aspects--flooding More suitable sites are those which are located outside the flooding areas of mountain streams and outside the areas which are affected by erosion processes. According to exclusionary criteria E.2.1. all flooding areas referring to mountain streams have to be rejected, and the drainage basin above this area needs to be analyzed on erosion risk. Scaling method: potential sites are ranked using five-point scale 1-5, according to the value of "coefficient of erosion" which was estimated on the basis of annual average precipitation, coefficient of ground-resistance, coefficient of biological cover and regulation of drainage basin and coefficient of morphological characteristics of drainage basin. B.2.2. Meteorological aspects--extreme phenomena More suitable sites are those having less intensive (frequency and amounts) precipitation. Scaling method: potential sites are ranked according to the value of extreme precipitation for return period of 100 years.
B.3.1. Seismotectonics and seismic--neotectonic activity More suitable sites are those located in neotectonically less active zones. Scaling method: potential sites are ranked using three-point scale I-3, according to scoring on Table 2. List of comparative criteria and values of weighting factors A
C
B
Engineering aspects
Safetyrelated aspects
D W.F. weighting Environmental aspects factors Vicinity area
Wider area Total
Aspects of the site selection procedure
Index
I. Transportation 1.1. Transportation of radioactive waste 2. Meteorological and hydrological aspects 2.1. Hydrological aspects 2.2. Meteorological aspects 3. Geology and seismology 3.1. Seismotectonics and seismics A.3.1. A.3.2. 3.2. Soil engineering 3.3. Hydrogeology 4. Demography 5. Present and planned land use 5,1. Settlements 5.2. Tourism 5.3. Agriculture 5.4. Forestry 5.5. Industry and mining 5.6. Infrastructure 5.7. Special purposes 6. Environmental protection 6.1. Natural heritage protection 6.2. Cultural heritage protection 6.3. Soil properties 6.4. Biological/ecological values 6.5. Radiological aspects Total
W.F. %
4,0 4,0
Index
B.2.1. B.2.2.
7,5 2,8
B.3.1. B.3.2.
5,9 9,8
8.6.3.
8,0
W.F. %
4,0
30,0
Index
W.F, %
C.I.I.
3,7
3,7
C.2.1. C.2.2.
3,2 0,8
14,3
C.3.3. C.4.0.
12,1 5,4
35,8 5,4
C.5.1. C.5.2. C.5.3. C.5.4. C.5.5. C.5.6. C.5.7.
4,4 3,3 2,6 2,2 1,1 1,5 1,1
D.5.1. D.5.2.
C.6.1. C.6.2. C.6.3. C.6.4. C.6.5.
3,0 1,6 2,4 2,5 1,6
D.6.1. D.6.2.
52,5
Index
W.F. %
3,5 2,5
22,2 2,5 1,0
18,6 9,5
I00,0
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geological structure, amplitudes and nature of neotectonic movements, distance from a fault and fault activity. This scoring is made by geology experts.
B.3.2. Lithology and 9eomorphology More suitable sites are those made by unweathered clays, clayey marls or sediments consisting of mixed clay and silt, as well as the areas composed of shales or unfractured metamorphic and igneous rocks. Scaling method: potential sites are ranked using six-point scales 1-6, according to scoring on prevailing rock type, engineering-geological rock classification, erodibility and land-sliding risk.
B.6.3. Soil properties--chemical aggressiveness More suitable sites are those where the soil are predominantly characterized by low chemical aggressiveness. Scaling method: potential sites are ranked using four-point scale 1-4, according to scoring on active soil acidity (pH values in H20 in surface soil horizon), humus composition and erodibility.
C.I.I. Transportation of radioactive waste More suitable sites are those which offer the greatest possible safety regarding transportation of radioactive waste. It was difficult to use this criterion straightforwardly because the beginning and the end points of the transportation route are not known yet. Scaling method: potential sites are ranked using five-point scale 1-5, according to scoring on potential site altitude, distance from regional transportation routes and intensity of precipitation.
C.2.1. Hydrologic aspects--distance J'rom surface water More suitable sites are those situated at a greater distance to permanent and intermittent surface streams, lakes, fish ponds and reservoirs. Scaling method: potential sites are ranked according to a value which was estimated on the basis of distance of surface waster from potential sites.
C.2.2. Meteorological aspects--dispersion in atmosphere More suitable sites are those where expected dispersion in the ground atmospheric layer is greater. Scaling method: potential sites are ranked using four-point scale 1-4, according to scoring on the dispersion characteristics of the ground atmospheric layer. This scoring was made by meteorological expert.
C.3.3. H ydrogeology More suitable sites are those where there is no groundwater or where the reserves of groundwater are insignificant, and where infiltration capability and flow-rate of ground-water eliminate the possibilities for radio-nuclide migration. Scaling method: potential sites are ranked using six-point scale 1-6, according to scoring on prevailing rock type, crack porosity, expected coefficient of primary filtration rate and number of water springs within a 10km radius from the potential site. This scoring was made by a hydrogeological expert.
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C.4.0. Demographic aspects More suitable sites are those having a lower population density and depopulation trends in settlements situated within 5 km from the site. Scaling method: potential sites are ranked according to score values which are estimated on the basis of population density at potential sites within 5 km radius, and according to seven categories of the demographic status of settlements.
C.5.1. Settlements More suitable sites are those where within a 5 km radius there is a smaller number of settlements. Scaling method: potential sites are ranked according to score values which are estimated on the basis of the number of settlements (classified in five categories according to the number of inhabitants), and on the basis of degree of centralization, which is defined according to urban and land use plans.
C.5.2. Tourism More suitable sites are those having a smaller number of tourist centres and a smaller number of existing and planned facilities for tourist lodgings within a 5 km radius. Scdaling method: potential sites are ranked according to score values which are estimated on the basis of the number of tourist centers (classified in three categories according to type of tourism), and the number of beds (lodging capacity).
C.5.3. Agriculture More suitable sites are those located in the areas with a low potential of agricultural yield within a 5 km radius, relatively unsuitable for cattle raising and for crops production, which are also at a greater distance from highly productive agricultural areas. Scaling method: potential sites are ranked according to score values which are estimated on the basis of soil quality, suitability for domestic animals raising and according to the distance from the areas having intensive agricultural production.
C.5.4. Forestry More suitable sites are those where within a 5 km radius there are fewer secondary forest products: edible mushrooms and medical herbs. Scaling method: evaluation is done by experts on the basis of potential quantity of forest (plant) "products" per square unit area. Score value for each potential site has been calculated and classified in to three categories.
C.5.5. Industry and mining More suitable sites are those where within a 5 km radius there is a smaller number of industrial centres of any kind and special industry with "sensitive" products (food, pharmaceuticals). Scaling method: potential sites are ranked using three-point scale 0-2. Point value is estimated on the basis of number of industrial centers, numbers of employees and type (kind) of industrial activities.
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C.5.6. Infrastructure More suitable sites are those where the connections to infrastructure installations (water and electricity supply) are better. Scaling method: potential sites are ranked using three-point scale 1-3. The distance to connections to electricity network as well as the distance to technological water supply is evaluated on the basis of expert assessment.
C.5.7. Special purposes More suitable sites are those having no limitations or special requirements from the aspect of national defense.
Ministry of National Defense of Croatia reviewed the results of Phase I of the site selection process (i.e. potential areas). The remaining areasfor further investigations have no special requirements from the aspect of national defense. C.6.1. Natural heritage protection More suitable sites are those having fewer protected localities within a 5 km radius of the site. Scaling method: potential sites are ranked according to score values which are estimated on the basis of categories of protection according to the Nature Protection Act. Score values are estimated on the base of expert opinion on a 1-10 scale.
C.6.2. Cultural heritage protection More suitable sites are those having fewer protected localities and objects within a 5 km radius of the site. Scaling method: potential sites are ranked in five categories, 1-5 according to the score values which are estimated by experts on the basis of numbers of localities, "density" of localities, specific regional characteristics and estimated value of localities.
C.6.3. Soil properties--plant production More suitable sites are those with less area of high-quality soils for plant production within a 5 km radius of the site. Scaling method: potential sites are ranked using four-point scales 1-4. Scoring is determined on the basis of soil types, soil thickness and structures, granulometric properties, draining properties and nutritive characteristics.
C.6.4. Biological/ecological values Disposal sites surrounded by biologically less valuable or less sensitive areas within a 5 km radius, are preferable. Scaling method: potential sites are ranked using ten-point scale 1-10. Scoring is estimated by experts on the basis of the evaluation of ecosystem diversity, ecosystem specificity, irretrievability, endemic features, biomass, stability or age of ecosystem and species diversity.
C.6.5. Radiological aspects of existing conditions More suitable sites are those where there is a smaller groundwater migration rate, and less potential for bioaccumulation of radio-nuclides in organisms within a 5 km radius of the site.
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Scaling method: potential sites are ranked using four-point scale 1-4. Scoring is estimated by experts on the basis of the evaluation of characteristics influencing migration and bio-accumulation of radio-nuclides in the vicinity of potential site.
D.5.1. Settlements More suitable sites are those where there are fewer settlements within a 5-20 km radius area. Scaling method: the same as in C.5.1.
D.5.2. Tourism More suitable sites are those having fewer high quality tourist centers, fewer existing and planned facilities for tourist lodgings and shorter tourist season, in a radius of up to 20 km of the site. Scaling method: the same as in C.5.2.
D.6.1. Natural heritage protection More suitable sites are those having fewer protected localities within a 20 km radius. Scaling method: the same as in C..6.1.
D.6.2. Cultural heritage protection More suitable sites are those with less and more distant protected amenities of cultural heritage in the wider site area. Scaling method: the same as in C.6.1.
IMPLEMENTATION OF COMPARATIVE CRITERIA--METHOD OF RANKING There are many ranking techniques and methods in practice. On the basis of the experience acquired in Croatia, it was decided that in the ranking of potential sites for the LILRW repository a multicritereia analysis had to be used. The PROMETHEE method ("Preference Ranking Organization for Enrichment Evaluations"), developed by Brand and Vincke, was chosen (Brans et al., 1986). The method is computerized using principles of multicriteria techniques and decision-making methods. The main characteristic of this multicriteria decision aid is pairwise comparison of alternatives, using preference functions, defined for each criteria, in order to obtain a partial or complete Pre-order? of efficient solutions. The relative significance of particular criterion is expressed by assigning to it a corresponding weighting factor. In our case, the values of weighting factors were estimated by the heuristic rating method, based on the decisions of the expert team. After analyzing and discussing the criteria, the members of the expert team proposed the weighting factors and made the ranking list of all criteria as a result. A special expert coordination-group adopted the final list of weighting factors, presented in Table 2. The scaling method of criteria evaluation was done by scoring, but so that the final weighting factors were expressed in percentages. It is obvious that the expert team placed emphasis on the criteria related to the safety of the LILRW repository (30%) and its closer area (52.5%). The wider area acceptability was assessed by the weighting factor of 9.5% since it was assumed that the LILRW repository had almost no impact on the wider site area. In the same way the importance of engineering aspects was estimated to only 8%, because it was assumed that the repository would not require complex civil-engineering interventions. In the course of the criteria evaluation, the author of this paper proposed that the defining of weighting factors and the ranking of criteria should be made by the mathematical algorithm using AHP (Analytic Hierarchy Process) of Saaty (Golden et al., 1989). However, the expert team did not
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accept that proposal, forming the opinion that in the considered case a heuristic evaluation of the criteria by the expert team would be more appropriate. PRELIMINARY RESULTS OF SITE SELECTION Following the adopted procedure (Fig. 1), at the end of Phase I 12 potential areas for siting the LILRW repository were selected. The first task in Phase II was to check all selected areas using the exclusionary criteria again, but this time based on more detailed maps (in the scale 1 : 100,000) in order to get more accurate data (geologic, lithologic, hydrogeologic, morphologic, hydrographic, etc.). After performed checking, the 12 potential areas were reduced to eight. Each of these areas was divided into several smaller areas relatively homogeneous regarding some of the more important comparative criteria. That resulted in 97 smaller areas, which represented the starting point for the preliminary evaluation. The preliminary evaluation and comparison were performed in order to reject all those smaller areas that were evidently worse than the others. The proposed comparative criteria and weighting factors were used for comparison by computer program PROMCALC (Mladineo, 1990; Brown and Marechel, 1994; Brans and Marescuai, 1994 applying the PROMETHEE methodology). For some of the criteria the assessment was based on the data collected exclusively for the purpose of that work, or on the data existing in the institutions participating in that work. Some assessments were based on the expert opinions. The analyses of the obtained results included the following: (a) analysis of ranking; (b) comparative analysis of results (c) determination of relations regarding groups of criteria (A, B, C, D). As the result of this evaluation, among 97 smaller potential areas only 47 were selected in order to be considered in the next phase of the site selection. Within those selected areas, potential sites were identified by determining "reference points". The determination of reference points was based on some favourable topographic, geomorphic, hydrologic, demographic and traffic-related characteristics of the concerned potential site. Topographic maps in the scale 1:25,000, as well as the data obtained from hydrogeologic and seismic-tectonic maps, were also considered. In the next phase, more detailed data were collected for the remaining 47 potential sites. The sites were prospected in the field and reference exclusionary criteria were checked once more. During the field-prospect of potential sites, previously determined reference points were re-evaluated. With respect to basic safety site characteristics (lithology, hydrogeology, risk of flooding), several potential sites were excluded since they were assessed to be significantly less suitable than the others. Thus, the number was reduced to 34 potential sites. All relevant characteristics of these remaining sites were assessed, and a preliminary comparison was performed on the basis of all comparative criteria and by means of the multicriteria P R O M E T H E E approach. The results of the preliminary comparison of potential sites served to the expert coordination group as the decisional background for the preliminary selection and a short list of preferred sites. Several most favorable potential sites were selected and grouped in four smaller areas (7.5-23.5 km z) designated as preliminary preferred sites. PROVISIONAL CONCLUSION The presented procedure of the site selection for the LILRW repository in Croatia was developed on the principles of "Problem Solving Technology". This procedure, the definition of the criteria and weighting factors, as well as the choice of preferred sites have to be verified by a competent public body. This verification has not been done yet because of the war in Croatia, and consequently everything presented in this paper needs to be considered as provisional. The remarks that can possibly result from public and/or expert debate on the procedure and criteria, need to be thoroughly discussed among the members of the study expert team. If any of the remarks are justified, they need to be accepted and the relevant part(s) of the procedure has to be modified.
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REFERENCES Bana e Costa, C. (1990) Readings in Multiple Criteria Decision Aid. Springer-Verlag, Berlin. Berakovib,, B., Fijan, Z. and Lauc, A. (1986) Status causes and possibilities of development of operational research. X Conference IFORS, Washington, July 1986. Brans, J.P. and Mareschal, B. (1992) PROMETHEE V: MCDM problems with segmentation constraints. Infor 30(2), 35-96. Brans, J.P. Maresachal, B. and Vincke, Ph. (1986) How to select and how to rank projects: the PROMETHEE method for MCEDM. European Journal of Operational Research 24, 228-238. lnstitut for Urban Planning of Croatia (1991) Site Survey-stage of the siting process for Low-and Intermediate-Level Radioactive Waste disposal facilities, Zagreb, Croatia. Mareschal, B. and Brans, J.P. (1988) Geometrical representations for MCDA: the GAlA procedure. European Journal of Operational Research 34, 69-77. Mladineo, N. (1990) Multi-criteria analysis method. (Elaboration prepared for the Study: "Site survey stage of the siting process for Low- and Intermediate- Level Radioactive Waste disposal facilities" in Croatia.) Gradevinski fakultet, Split, Croatia.
ITOR 4:4-8
Pergamon
so969--6ol~97)oooo3-s
1997 IFORS. Published by EIsevi©rScience Ltd All rights reserved. Printed in Great Britain 0969-6016/97 $17.00 + 0.00
Ranking the Sites for Low- and Intermediate-Level Radioactive Waste Disposal Facilities in Croatia JOSIP C.E. PETRA~ University of Zagreb, Croatia This paper describes the procedure of identification and ranking of the potential sites for LILRW disposal facilities in Croatia. It presents preliminary results of the final phase of the site survey stage, i.e. preliminary comparison and ranking of potential sites. The potential sites were chosen on the basis of exclusionary (rejection) criteria, and the preliminary ranking of the sites was performed on the basis of comparative preference criteria by the multicriteria analysis approach PROMETHEE. The list of exclusionary and comparative criteria is given, and the weighting factors of comparative criteria are presented. © 1997 IFORS. Published by Elsevier Science Ltd.
Key words: Siting, radioactive waste disposal, procedure, exclusionary criteria, comparative criteria, weighting factors, preferences.
INTRODUCTION In the process of preparing the Urban and Land Use Plan (ULUP) of Croatia in the year 1990, among other study documentation, the study: "Site Survey Stage of the Siting Process for Low- and Intermediate- Level Radioactive Waste disposal facilities" (LILRW) was made. This study was a part of the bigger study: "Site Screening Investigation and Assessment of Site Suitability for Fossil Fuel Power Plants and Nuclear Facilities on the Territory of the Republic of Croatia" The author of this paper was a member of the team which made the LILRW study. The objective of the study was to identify suitable sites for the LILRW repository and make a preliminary ranking list of these sites. It was planned that the study would be discussed in the State Parliament twice: --for the approval of criteria and methodology, and --for the approval of its results, i.e. the proposed preferred sites to be included in the ULUP. The first discussion was held at the end of 1990, and in January 1991 the Government of Croatia published the booklet with the result of the work done by that time. The purpose of the publication was to inform the public on the proposed methodology and siting criteria. The proposed methodology and criteria for the LILRW repository were reviewed and positively assessed by the International Atomic Energy Agency (IAEA) Radioactive Waste Management Advisory Programme (RWAMAP) mission in Croatia and Slovenia, in April 1991. Further work on the study was interrupted because of the beginning of the war in Croatia. Now the war has ended, the activities are continuing.
THE PROCEDURE OF SITE SELECTION FOR LILRW REPOSITORY IN CROATIA The site selection for the LILRW repository in Croatia, a complex task, has to be in compliance with national and IAEA regulations. The basic law that regulates this subject as well as the conditions for using other legislation and standards is the"Act on Radiation Protection and the Safe Use of Nuclear Energy". According to this Act, all regulations relevant to LILRW repository siting were considered in the first phase of the selection process in Croatia. The process involves three basic steps: 1. Site survey stage, i.e. regional and site(s) screening studies, having as primary objective the inclusion of preferred sites in the "ULUP of Croatia"; 2. Modifications and supplements to the ULUP defined on the basis of the Parliament decisions on the inclusion of preferred sites in the ULUP;
Correspondence: Josip C.E. Petrag, Faculty of Civil Engineering, University of Zaffreb, Croatia
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~,.
THE WHOLE TERRITORY 3 OF CROATIA J
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Fig. 1. Procedureappliedin the LILRW repositorysite selectionCroatia.
3. Licensing procedures for site permits (including site evaluation and site confirmation stages of the siting process) on the basis of necessary investigations and studies. The first of these three steps is the subject of this paper. The procedure applied m this step is shown in Fig. 1. It is developed on the principles of"Problem solving technology" (Berakovi~ et al., 1986). In methodological sense, the procedure consists of two basic phases: Phase I: Regional Analysis of the Territory of the Republic of Croatia and Selection of Potential Regions (Areas) Phase II: Identification of Potential Sites and Selection of Preferred Sites. In Phase I, the whole territory of Croatia was analysed. This was performed by using the exclusionary (rejection) criteria method (exclusionary screening). The areas that were unacceptable on the basis of at least one characteristic were rejected. The remaining areas were designated as potential areas or further analysis. The bases for applying exclusionary criteria in this phase were appropriate topographic and other
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specialized maps of Croatia, mostly in the scale 1: 300,000, as well as the existing data corresponding to the selected scale. In Phase II, all the potential areas remaining after Phase I were checked on the compliance with the exclusionary criteria applied on the basis of more detailed data and maps (in the scale 1: 100,000). Comparative preference criteria were then formulated and applied to potential areas in order to identify and select potential sites. The same criteria, but with more detailed data and investigations, were also applied for ranking potential sites in order to select several preferred candidate sites. This task is divided into three subphases as follows:
( A ) Selection of parameters and criteria In this subphase the proposed parameters and criteria used in the identification, selection and comparison of potential sites were formulated by a team of experts composed of specialists from various relevant fields described below.
( B) Assessment of potential areas and identification of potential sites During this subphase, the potential areas from Phase 1 were divided into smaller, relatively homogeneous areas. The identification and assessment of such homogeneous smaller potential areas was performed by applying:
(a) Exclusionary criteria. Supplemented and revised exclusionary criteria from Phase I, completed by a map survey in scale 1 : 100,000, (b) Comparative criteria. As a basis for the identification of potential sites. The comparison of a great number of those areas and the selection of more suitable ones was performed by computer program--using the multicriteria analysis approach PROMETHEE (Brans et al., 1986; Mladineo, 1990). In the selected smaller areas the potential sites were identified by using topographic maps in the scale 1:25,000 and data on certain comparative criteria. ( C ) Comparison of potential sites and selection of preferred candidate sites In this subphase, the assessment and comparison of potential sites was performed by using the selected PROMETHEE program for multicriteria analysis. The result of the analysis in this subphase is in fact the final result of the whole study and its primary objective, i.e. the selection of several referred candidate sites, will be presented for the initiation of procedures for the amendment and supplement of the ULUP.
PRINCIPLES OF FORMULATING EXCLUSIONARY CRITERIA Exclusionary criteria were formulated by a team of experts. This team was formed after the consideration of all relevant regulations to LILRW repository siting. The members of the team were scientists and experts in the field of different technical, natural, and social disciplines. In the procedure of formulating exclusionary criteria, different viewpoints and principles for formulating these criteria were analyzed first. The principles were adopted as follows:
(a ) Viewpoint of economics of engineering solutions for a LILR W repository The areas in which it is not possible to meet the necessary technical/technological requirements or where the engineering solution of repository construction and operation would be highly uneconomical (e.g. seismo-tectonics area) need to be rejected.
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(b) Viewpoint of safety requirements The areas where it is not possible to meet safety requirements defined by law, as well as the areas where those requirements would be met mainly by applying engineering solutions, have to be rejected (e.g. hydrological characteristics).
(c) Viewpoint of land use in closer and wider site area of repository The areas where the present and planned land use in the closer or wider site area would be in significant conflict with LILRW repository operation need to be rejected (e.g. high population density, natural amenities, etc.).
REVIEW OF EXCLUSIONARY CRITERIA On the basis of the quoted principles and significant factors of repository site in Table 1 the review of the exclusionary criteria is presented (Study, 1991). In formulating these criteria, the following aspects were taken into consideration: I. transportation, 2. hydrologic aspects, 3. geology and seismology, 4. demography, 5. present and planned land use, 6. environmental protection. Taking these aspects into consideration the following exclusionary criteria were formulated: E.2.1. Flooding: All natural floodplain areas (return period of 1000 years) are rejected, regardless of whether they are protected or not. E.3.1.1. Seismotectonics: The areas with maximal potential earthquake intensity of the IX or over IX degree on the commonly used MCS scale are rejected. E.3.1.2. Neotectonics: The areas in zones having identified faults are rejected. E.3.2. Lithological and geomorphological characteristics: The areas having increased erosion rate caused by iithology or relief dynamics as well as the areas composed of rocks unstable under natural conditions (weathering, etc.) and by construction activities are rejected for shallow ground type of repository. - - F o r tunnel-type of repository the areas exhibiting land-sliding and rock-falling are rejected, if that poses hazard to repository structures. [The tunnel-type of LILR W repository means the digging of disposal tunnels in hard rocks (mainly in granites) as stable, shallow geological structures. In such tunnels immobilized radwaste is being disposed in metal drums that are placed in concrete boxes which are finally filled up with fresh concrete mass.] E.3.3. H ydrogeology--protection of water-bearing layer (aquifer): --The areas containing protected sources of potable water accordng to "The Regulations on Protective Measures and Conditions for Determining Zones of Sanitary Protection for Sources of
Table 1. List of exclusionary criteria Environmental acceptability Aspects of the site selection procedure I. Transportation 2. Hydrologic aspects 2.1. Flooding 3. Geology and seismology 3.1. Seismotectonics Neotectonics 3.2. Lithology and geomorphology 3.3. Hydrogeology 4. Demography 5. Present and planned land use 5.1. Special purposes 5.2. Mining and mineral exploitation 6. Environmental protection 6.1. Natural heritage protection 6.2. Cultural heritage protection
Economics engineering
Safety
Vicinity area
Wider area
E.2.1. E.3,1.1. E3.1.2. E.3.2. E.3.3. E.4.0.
E.5.I. E.5.2. E.6.1. E.6.2.
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Potable Water" are rejected. - - F o r the purpose of protecting water, a disposal facility site cannot be located in an area having significant water-bearing layer (aquifers) of any type. E.4.0. Population density: The areas having a cumulative population density of more than 80 inhabitants per sq. km within a 20 km radius from repository site are rejected. E.5.1. Special purposes: The areas designated for special purposes, including protected zones, are rejected. (Some areas have special land use and protection status regarding national defense.) E.5.2. Mining and minerals exploitation: The areas in zones of present or future mining and exploitation of minerals, gas, oil, coal, etc. are rejected. E.6.1. Natural heritage protection: National parks, natural parks and other significant natural amenities are rejected. E.6.2. Cultural heritage protection: The areas having cultural amenities registered in the List of World Cultural and Natural Heritage as well as those having other cultural amenities of great importance for the entire community are rejected. According to each group of thexe exclusionary criteria, the screening analysis of the whole territory of Croatia was made, and the results were given on maps in the scale 1 : 300,000. Based on all collected results, 12 potential areas, situated in the central and east part of Croatia were selected. In these areas there are many possibilities for LILRW repository siting. These possibilities were analysed in Phase II of the site selection process.
PRINCIPLES OF FORMULATING COMPARATIVE CRITERIA Comparative criteria were formulated by the same team of experts which formulated the exclusionary criteria. Comparative criteria are usually presented in the form of requirements for achieving a certain goal or a desired state. These goals can be defined as ideal (desirable) conditions, and if an ideal condition cannot be achieved, the criteria have also to describe the degree of acceptability. The comparative criteria were formulated from the same points of view like the exclusionary criteria, i.e. engineering aspects, safety-related aspects, environmental impact and acceptability in the closer site area and in the wider site area.
(a) Engineering aspects Preference has to be given to the sites which enable simpler and thus more economical engineering solutions. The analysis of site characteristics has to be made, and the sites which enable less expensive engineering solutions are to be preferred.
(b ) Safety-related aspects Sites are more suitable where safety is based upon better natural characteristics, requiring the minimum of engineering interventions. The analysis has to be made of whether the safety requirements for the construction and/or operation of the waste disposal facility are met. The preference is to be given to the sites having better natural safety.
(c ) Environmental impact and acceptability in closer site area The public acceptance of potential sites depends heavily on the environmental impact of the repository. It is therefore very important for the phase of preferred sites identification and selection to consider and analyse all the aspects of possible environmental aspects, and to formulate on the basis of such comprehensive considerations the comparative criteria which refer to environmental protection. Following the domestic legal provisions and international recommendations which refer
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to the management of radioactive waste (contained primarily in I AEA--International Atomic Energy Aoency--documents), the expert team in Croatia has considered the following aspects: natural
heritage protection, cultural heritage protection, soil properties, biological and ecological values, and radiologieal aspects. In connection with these aspects, the following principles for the comparative criteria formulation referring to the acceptability in closer site area were defined: --Preference has to be given to the natural site characteristics which provide a lesser environmental impact, as well as to the present and planned land use that ensures better safety and acceptability of the site. The analysis has to be made on whether the safety requirements are met concerning the impact of the facility on the immediate environment. Emphasis is placed upon impact during regular disposal operations as well as in the cases of possible accidents. The characteristics of the site can also affect the degree of social acceptance. Therefore, --the sites having better natural characteristics and with minimum requirements on engineering interventions are more suitable and have to be preferred. Also, --the sites where it is possible to anticipate less conflict with other users of the area are more suitable. (For this group of criteria in Croatia the analysis and comparison of characteristics of the area surrounding a potential site within a radius of approx. 5 km were performed).
(d) Acceptability o['the site (]acility ) in wider .site area Related to the previously mentioned aspects of LILRW repository impact on the environment, the following principles for the comparative criteria formulation referring to the acceptability in wider site area were defined: --Preference has to be given to natural site characteristics which provide fewer conflicts in wider site area, concerning the impact of regular disposal operations on present and planned land use. The analysis has to be made on the possible impact of the waste disposal facility on the wider site area. Emphasis is placed upon the analysis of the present and planned land use as well as the degree of social acceptance regarding possible changes in the value of the area. Due to that, --the sites where it is possible to anticipate fewer conflicts with the present users of the area are more suitable and have to be preferred. (For this group of criteria in Croatia the analysis and comparison of characteristics of the area surrounding a potential site within a radius of approx. 20 km were performed.)
REVIEW OF COMPARATIVE CRITERIA On the basis of the quoted principles and significant factors of repository site in Table 2 the review of ratings/scores of comparative criteria is presented (Study, 1991). In the formulating of these criteria the following aspects were taken into considerations:
A.3.1. Seismotectonics and seismic--seismic activity More suitable sites are those where the earthquake activity is expected to be of smaller intensity. Scaling method: maximum horizontal acceleration of ground oscillations for earthquake has been calculated on the basis of earthquake intensity. According to this acceleration potential sites are ranked by scoring in the range 0-100%.
A.3.2. Soil mechanics Less suitable sites are those where less favorable natural conditions (unsuitable slope inclination, surface soil layer having unsuitable geomechanical characteristics with lower permitted load properties) are present at the site. Scaling method: potential site has been evaluated on the basis of expert opinion respecting
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morphologic characteristics (slope inclination), lithological properties, permitted basement load and seismic characteristics. Potential sites are ranked in 1-10 range categories. B.2.1. Hydrologic aspects--flooding More suitable sites are those which are located outside the flooding areas of mountain streams and outside the areas which are affected by erosion processes. According to exclusionary criteria E.2.1. all flooding areas referring to mountain streams have to be rejected, and the drainage basin above this area needs to be analyzed on erosion risk. Scaling method: potential sites are ranked using five-point scale 1-5, according to the value of "coefficient of erosion" which was estimated on the basis of annual average precipitation, coefficient of ground-resistance, coefficient of biological cover and regulation of drainage basin and coefficient of morphological characteristics of drainage basin. B.2.2. Meteorological aspects--extreme phenomena More suitable sites are those having less intensive (frequency and amounts) precipitation. Scaling method: potential sites are ranked according to the value of extreme precipitation for return period of 100 years.
B.3.1. Seismotectonics and seismic--neotectonic activity More suitable sites are those located in neotectonically less active zones. Scaling method: potential sites are ranked using three-point scale I-3, according to scoring on Table 2. List of comparative criteria and values of weighting factors A
C
B
Engineering aspects
Safetyrelated aspects
D W.F. weighting Environmental aspects factors Vicinity area
Wider area Total
Aspects of the site selection procedure
Index
I. Transportation 1.1. Transportation of radioactive waste 2. Meteorological and hydrological aspects 2.1. Hydrological aspects 2.2. Meteorological aspects 3. Geology and seismology 3.1. Seismotectonics and seismics A.3.1. A.3.2. 3.2. Soil engineering 3.3. Hydrogeology 4. Demography 5. Present and planned land use 5,1. Settlements 5.2. Tourism 5.3. Agriculture 5.4. Forestry 5.5. Industry and mining 5.6. Infrastructure 5.7. Special purposes 6. Environmental protection 6.1. Natural heritage protection 6.2. Cultural heritage protection 6.3. Soil properties 6.4. Biological/ecological values 6.5. Radiological aspects Total
W.F. %
4,0 4,0
Index
B.2.1. B.2.2.
7,5 2,8
B.3.1. B.3.2.
5,9 9,8
8.6.3.
8,0
W.F. %
4,0
30,0
Index
W.F, %
C.I.I.
3,7
3,7
C.2.1. C.2.2.
3,2 0,8
14,3
C.3.3. C.4.0.
12,1 5,4
35,8 5,4
C.5.1. C.5.2. C.5.3. C.5.4. C.5.5. C.5.6. C.5.7.
4,4 3,3 2,6 2,2 1,1 1,5 1,1
D.5.1. D.5.2.
C.6.1. C.6.2. C.6.3. C.6.4. C.6.5.
3,0 1,6 2,4 2,5 1,6
D.6.1. D.6.2.
52,5
Index
W.F. %
3,5 2,5
22,2 2,5 1,0
18,6 9,5
I00,0
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geological structure, amplitudes and nature of neotectonic movements, distance from a fault and fault activity. This scoring is made by geology experts.
B.3.2. Lithology and 9eomorphology More suitable sites are those made by unweathered clays, clayey marls or sediments consisting of mixed clay and silt, as well as the areas composed of shales or unfractured metamorphic and igneous rocks. Scaling method: potential sites are ranked using six-point scales 1-6, according to scoring on prevailing rock type, engineering-geological rock classification, erodibility and land-sliding risk.
B.6.3. Soil properties--chemical aggressiveness More suitable sites are those where the soil are predominantly characterized by low chemical aggressiveness. Scaling method: potential sites are ranked using four-point scale 1-4, according to scoring on active soil acidity (pH values in H20 in surface soil horizon), humus composition and erodibility.
C.I.I. Transportation of radioactive waste More suitable sites are those which offer the greatest possible safety regarding transportation of radioactive waste. It was difficult to use this criterion straightforwardly because the beginning and the end points of the transportation route are not known yet. Scaling method: potential sites are ranked using five-point scale 1-5, according to scoring on potential site altitude, distance from regional transportation routes and intensity of precipitation.
C.2.1. Hydrologic aspects--distance J'rom surface water More suitable sites are those situated at a greater distance to permanent and intermittent surface streams, lakes, fish ponds and reservoirs. Scaling method: potential sites are ranked according to a value which was estimated on the basis of distance of surface waster from potential sites.
C.2.2. Meteorological aspects--dispersion in atmosphere More suitable sites are those where expected dispersion in the ground atmospheric layer is greater. Scaling method: potential sites are ranked using four-point scale 1-4, according to scoring on the dispersion characteristics of the ground atmospheric layer. This scoring was made by meteorological expert.
C.3.3. H ydrogeology More suitable sites are those where there is no groundwater or where the reserves of groundwater are insignificant, and where infiltration capability and flow-rate of ground-water eliminate the possibilities for radio-nuclide migration. Scaling method: potential sites are ranked using six-point scale 1-6, according to scoring on prevailing rock type, crack porosity, expected coefficient of primary filtration rate and number of water springs within a 10km radius from the potential site. This scoring was made by a hydrogeological expert.
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C.4.0. Demographic aspects More suitable sites are those having a lower population density and depopulation trends in settlements situated within 5 km from the site. Scaling method: potential sites are ranked according to score values which are estimated on the basis of population density at potential sites within 5 km radius, and according to seven categories of the demographic status of settlements.
C.5.1. Settlements More suitable sites are those where within a 5 km radius there is a smaller number of settlements. Scaling method: potential sites are ranked according to score values which are estimated on the basis of the number of settlements (classified in five categories according to the number of inhabitants), and on the basis of degree of centralization, which is defined according to urban and land use plans.
C.5.2. Tourism More suitable sites are those having a smaller number of tourist centres and a smaller number of existing and planned facilities for tourist lodgings within a 5 km radius. Scdaling method: potential sites are ranked according to score values which are estimated on the basis of the number of tourist centers (classified in three categories according to type of tourism), and the number of beds (lodging capacity).
C.5.3. Agriculture More suitable sites are those located in the areas with a low potential of agricultural yield within a 5 km radius, relatively unsuitable for cattle raising and for crops production, which are also at a greater distance from highly productive agricultural areas. Scaling method: potential sites are ranked according to score values which are estimated on the basis of soil quality, suitability for domestic animals raising and according to the distance from the areas having intensive agricultural production.
C.5.4. Forestry More suitable sites are those where within a 5 km radius there are fewer secondary forest products: edible mushrooms and medical herbs. Scaling method: evaluation is done by experts on the basis of potential quantity of forest (plant) "products" per square unit area. Score value for each potential site has been calculated and classified in to three categories.
C.5.5. Industry and mining More suitable sites are those where within a 5 km radius there is a smaller number of industrial centres of any kind and special industry with "sensitive" products (food, pharmaceuticals). Scaling method: potential sites are ranked using three-point scale 0-2. Point value is estimated on the basis of number of industrial centers, numbers of employees and type (kind) of industrial activities.
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C.5.6. Infrastructure More suitable sites are those where the connections to infrastructure installations (water and electricity supply) are better. Scaling method: potential sites are ranked using three-point scale 1-3. The distance to connections to electricity network as well as the distance to technological water supply is evaluated on the basis of expert assessment.
C.5.7. Special purposes More suitable sites are those having no limitations or special requirements from the aspect of national defense.
Ministry of National Defense of Croatia reviewed the results of Phase I of the site selection process (i.e. potential areas). The remaining areasfor further investigations have no special requirements from the aspect of national defense. C.6.1. Natural heritage protection More suitable sites are those having fewer protected localities within a 5 km radius of the site. Scaling method: potential sites are ranked according to score values which are estimated on the basis of categories of protection according to the Nature Protection Act. Score values are estimated on the base of expert opinion on a 1-10 scale.
C.6.2. Cultural heritage protection More suitable sites are those having fewer protected localities and objects within a 5 km radius of the site. Scaling method: potential sites are ranked in five categories, 1-5 according to the score values which are estimated by experts on the basis of numbers of localities, "density" of localities, specific regional characteristics and estimated value of localities.
C.6.3. Soil properties--plant production More suitable sites are those with less area of high-quality soils for plant production within a 5 km radius of the site. Scaling method: potential sites are ranked using four-point scales 1-4. Scoring is determined on the basis of soil types, soil thickness and structures, granulometric properties, draining properties and nutritive characteristics.
C.6.4. Biological/ecological values Disposal sites surrounded by biologically less valuable or less sensitive areas within a 5 km radius, are preferable. Scaling method: potential sites are ranked using ten-point scale 1-10. Scoring is estimated by experts on the basis of the evaluation of ecosystem diversity, ecosystem specificity, irretrievability, endemic features, biomass, stability or age of ecosystem and species diversity.
C.6.5. Radiological aspects of existing conditions More suitable sites are those where there is a smaller groundwater migration rate, and less potential for bioaccumulation of radio-nuclides in organisms within a 5 km radius of the site.
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Scaling method: potential sites are ranked using four-point scale 1-4. Scoring is estimated by experts on the basis of the evaluation of characteristics influencing migration and bio-accumulation of radio-nuclides in the vicinity of potential site.
D.5.1. Settlements More suitable sites are those where there are fewer settlements within a 5-20 km radius area. Scaling method: the same as in C.5.1.
D.5.2. Tourism More suitable sites are those having fewer high quality tourist centers, fewer existing and planned facilities for tourist lodgings and shorter tourist season, in a radius of up to 20 km of the site. Scaling method: the same as in C.5.2.
D.6.1. Natural heritage protection More suitable sites are those having fewer protected localities within a 20 km radius. Scaling method: the same as in C..6.1.
D.6.2. Cultural heritage protection More suitable sites are those with less and more distant protected amenities of cultural heritage in the wider site area. Scaling method: the same as in C.6.1.
IMPLEMENTATION OF COMPARATIVE CRITERIA--METHOD OF RANKING There are many ranking techniques and methods in practice. On the basis of the experience acquired in Croatia, it was decided that in the ranking of potential sites for the LILRW repository a multicritereia analysis had to be used. The PROMETHEE method ("Preference Ranking Organization for Enrichment Evaluations"), developed by Brand and Vincke, was chosen (Brans et al., 1986). The method is computerized using principles of multicriteria techniques and decision-making methods. The main characteristic of this multicriteria decision aid is pairwise comparison of alternatives, using preference functions, defined for each criteria, in order to obtain a partial or complete Pre-order? of efficient solutions. The relative significance of particular criterion is expressed by assigning to it a corresponding weighting factor. In our case, the values of weighting factors were estimated by the heuristic rating method, based on the decisions of the expert team. After analyzing and discussing the criteria, the members of the expert team proposed the weighting factors and made the ranking list of all criteria as a result. A special expert coordination-group adopted the final list of weighting factors, presented in Table 2. The scaling method of criteria evaluation was done by scoring, but so that the final weighting factors were expressed in percentages. It is obvious that the expert team placed emphasis on the criteria related to the safety of the LILRW repository (30%) and its closer area (52.5%). The wider area acceptability was assessed by the weighting factor of 9.5% since it was assumed that the LILRW repository had almost no impact on the wider site area. In the same way the importance of engineering aspects was estimated to only 8%, because it was assumed that the repository would not require complex civil-engineering interventions. In the course of the criteria evaluation, the author of this paper proposed that the defining of weighting factors and the ranking of criteria should be made by the mathematical algorithm using AHP (Analytic Hierarchy Process) of Saaty (Golden et al., 1989). However, the expert team did not
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accept that proposal, forming the opinion that in the considered case a heuristic evaluation of the criteria by the expert team would be more appropriate. PRELIMINARY RESULTS OF SITE SELECTION Following the adopted procedure (Fig. 1), at the end of Phase I 12 potential areas for siting the LILRW repository were selected. The first task in Phase II was to check all selected areas using the exclusionary criteria again, but this time based on more detailed maps (in the scale 1 : 100,000) in order to get more accurate data (geologic, lithologic, hydrogeologic, morphologic, hydrographic, etc.). After performed checking, the 12 potential areas were reduced to eight. Each of these areas was divided into several smaller areas relatively homogeneous regarding some of the more important comparative criteria. That resulted in 97 smaller areas, which represented the starting point for the preliminary evaluation. The preliminary evaluation and comparison were performed in order to reject all those smaller areas that were evidently worse than the others. The proposed comparative criteria and weighting factors were used for comparison by computer program PROMCALC (Mladineo, 1990; Brown and Marechel, 1994; Brans and Marescuai, 1994 applying the PROMETHEE methodology). For some of the criteria the assessment was based on the data collected exclusively for the purpose of that work, or on the data existing in the institutions participating in that work. Some assessments were based on the expert opinions. The analyses of the obtained results included the following: (a) analysis of ranking; (b) comparative analysis of results (c) determination of relations regarding groups of criteria (A, B, C, D). As the result of this evaluation, among 97 smaller potential areas only 47 were selected in order to be considered in the next phase of the site selection. Within those selected areas, potential sites were identified by determining "reference points". The determination of reference points was based on some favourable topographic, geomorphic, hydrologic, demographic and traffic-related characteristics of the concerned potential site. Topographic maps in the scale 1:25,000, as well as the data obtained from hydrogeologic and seismic-tectonic maps, were also considered. In the next phase, more detailed data were collected for the remaining 47 potential sites. The sites were prospected in the field and reference exclusionary criteria were checked once more. During the field-prospect of potential sites, previously determined reference points were re-evaluated. With respect to basic safety site characteristics (lithology, hydrogeology, risk of flooding), several potential sites were excluded since they were assessed to be significantly less suitable than the others. Thus, the number was reduced to 34 potential sites. All relevant characteristics of these remaining sites were assessed, and a preliminary comparison was performed on the basis of all comparative criteria and by means of the multicriteria P R O M E T H E E approach. The results of the preliminary comparison of potential sites served to the expert coordination group as the decisional background for the preliminary selection and a short list of preferred sites. Several most favorable potential sites were selected and grouped in four smaller areas (7.5-23.5 km z) designated as preliminary preferred sites. PROVISIONAL CONCLUSION The presented procedure of the site selection for the LILRW repository in Croatia was developed on the principles of "Problem Solving Technology". This procedure, the definition of the criteria and weighting factors, as well as the choice of preferred sites have to be verified by a competent public body. This verification has not been done yet because of the war in Croatia, and consequently everything presented in this paper needs to be considered as provisional. The remarks that can possibly result from public and/or expert debate on the procedure and criteria, need to be thoroughly discussed among the members of the study expert team. If any of the remarks are justified, they need to be accepted and the relevant part(s) of the procedure has to be modified.
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REFERENCES Bana e Costa, C. (1990) Readings in Multiple Criteria Decision Aid. Springer-Verlag, Berlin. Berakovib,, B., Fijan, Z. and Lauc, A. (1986) Status causes and possibilities of development of operational research. X Conference IFORS, Washington, July 1986. Brans, J.P. and Mareschal, B. (1992) PROMETHEE V: MCDM problems with segmentation constraints. Infor 30(2), 35-96. Brans, J.P. Maresachal, B. and Vincke, Ph. (1986) How to select and how to rank projects: the PROMETHEE method for MCEDM. European Journal of Operational Research 24, 228-238. lnstitut for Urban Planning of Croatia (1991) Site Survey-stage of the siting process for Low-and Intermediate-Level Radioactive Waste disposal facilities, Zagreb, Croatia. Mareschal, B. and Brans, J.P. (1988) Geometrical representations for MCDA: the GAlA procedure. European Journal of Operational Research 34, 69-77. Mladineo, N. (1990) Multi-criteria analysis method. (Elaboration prepared for the Study: "Site survey stage of the siting process for Low- and Intermediate- Level Radioactive Waste disposal facilities" in Croatia.) Gradevinski fakultet, Split, Croatia.
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