Methodological Proposal for the Site Selection of a borehole Repository in Brazil
Pereira1, P. Rodrigues1, S. Cota1
1 Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Belo Horizonte, Brazil
Abstract According to the Brazilian regulation for site selection for low level waste repositories, areas of interest and preliminary areas steps must encompass a bibliographic review, followed by a systematic study of natural characteristics and infrastructure. Using a GIS platform, a methodology based on spatial and
geochemical/hydrochemical databases for porous and fissural domains, along with selection/exclusion criteria, were proposed to select possible sites of a borehole repository for sealed sources. After this
selection, technical, logistical and juridical features were also considered. Applying this methodology for Brazil, 209 counties were selected as preliminary areas. The lack of necessary databases can be a difficult
for applying this approach.
• Developed to meet the requeriments of the Brazilian Standards [1] and the ISAM methodology [2,
3]. • The site selection is a key component for assuring the safety of the repository design. • Main goal is to select Areas of Interest and Preliminary Areas. • The methodology uses a systematic process proposed by [4], including the Conceptual and
Planning Stage and the Area Survey Stage.
• Site selection process: indentification of the desirable features and data evaluation (FIG 1) [4,5,6]
• Databases were divided in Spatial data (Terrain and Technical, Logistical and Juridical Features) (TABLE 1 and 2) and Geochemical/Hydrochemical Data (Water analysis).
• Spatial data evaluation divided in each round, • Desirable features for each group ( TABLE 1 e 2)
TABLE 1: Desirable Terrain Features
Terrain Features Desirable
Characteristics Terrain Features
Desirable
Characteristics
Geology
(Geodiversidade and
Levantamento
Geológico/Litológico
database)
(1:2.500.000 scale)
Uniform stratigraphy,
lithology and
mineralogy, both in
thickness and mineral
composition
Meteorology (Atlas
Pluviométrico do
Brasil) (1:5.000.000
scale)
Low rainfall index
(<1400 mm/year)
Simple structural
characteristics High temperatures
Argillaceous and
massive crystalline
geologic terrains.
Arenaceus in
conjunction with
favorable climatic
conditions.
Geochemistry/hydro
chemistry (Rede
Integrada de
Monitoramento das
Águas Subterrâneas
database)
Low
sulphide/sulphates
and chloride content
Older rocks, with
seismological stability
and not disturbed by
fractures
pH is a dynamic
propriety, having
different impacts on
the engineered
barriers depending
of the geochemical
characteristics.
Higher pH solutions
(pH>8.5) are
desirable
Hydrogeology (Mapa
Hidrogeológico do
Brasil ao Milionésimo
database)
(1:1.000.000 scale)
Low hydraulic
conductivity and low
porosity values
Eh redox >200 mV
(NECSA.2004)
Regions with deep
seated groundwater
table or deep
geological confining
units (aquicludes) -
below of drinking
water zones
Tectonic and
seismicity: (Sismos
database)
Low tectonic and
seismic activity
Apart from recharge
zones or poor
recharge
No foresee uses
Surface processes
(Mapa Hidrogeológico
do Brasil ao
Milionésimo database)
(1:1.100.000 scale)
Stable and not
steeply relief, easy
access by road
Underdeveloped,
young soil
No presence of water
bodies
Far from coastal and
marine features
No. Criterion Cutt -off
values
Numerical parameters
(in km) Method
Scale Level
(*) 1 Source Cities none 720 Inclusion 1:100.000 1
2 Indigenous Criterion none 10 and 20¹ Exclusion
~1:5.500.000 1
3 Demographic density
(municipal) <57,39
inhab/km² 0 Inclusion
~1:500.000 2
4 Main Drainage none 1 Exclusion
1:1.000.000 2
5 Environmental
Conservation Units none 10 Exclusion
~1:500.000 2 6 Mining Areas none 0 Exclusion 1:100.000 3
7 Altitude aspect (over
1.800 m) none 1 Exclusion
1,000,000 3
8 Highways + main roads none 15 Inclusion 1:50.000 3
(*)Selection Levels defined on CNEN 6.06: Region of Interest 2: Preliminary Areas 3: Potential Areas 1: Aprox. mean area of all indian reservations in Brazil. Adopted for areas in study
TABLE 2: Desirable TLJ Features
FIGURE 2: Workflow of the methodology
3. Fissural Aproach
• The evaluation lead to 209 counties containing areas that met the
requirements proposed on the methodology • Possibility of correlating different variables and parameters • Tendency of rejecting sites based on false premises due the lack of
appropriated databases, heterogeneous scales, data inconsistencies and subjectivity of some criteria.
• As well established in the literature [3], only few requirements of the site must be satisfied, mainly related to hydrological and geochemical conditions
Results of fissural and
porous approach
Bibliography: [1] COMISSÃO NACIONAL DE ENERGIA NUCLEAR, Seleção e escolha de locais para depósitos de rejeitos radioativos, CNEN-NE-6.06, Brazil (1989). [2] INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Assessment Methodologies for Near Surface Disposal Facilities, Vol1 , Austria (2004). [3] INTERNATIONAL ATOMIC ENERGY AGENCY, BOSS: Borehole Disposal of Disused Sealed Sources, IAEA-TECDOC-1644, Vienna (2011). [4] SOUTH AFRICAN NUCLEAR ENERGY CORPORATION, Borehole Disposal Concept: Generic Site Selection and Characterisation, GEA-1622, Pretoria (2004). [5] INTERNATIONAL ATOMIC ENERGY AGENCY, Siting of Near-Surface Disposal Facilities, IAEA Safety Guide, Vienna (1990). [6] INTERNATIONAL ATOMIC ENERGY AGENCY, Borehole Disposal Facilities for Radioactive Waste, SSG-1, Vienna (2009).
1.Introduction
2.Methodology
3.Fissural approach
4. Porous approach
5. TLJ Features and potential hydrogeoeochemicical associated sites
6.Conclusions