Abstract
The final repository for low and intermediate level radioactive operational waste, SFR, located about 150 km north of Stockholm, is to undergo a future extension. The present on-going project, scheduled from 2007 to 2011, is to define and characterise a suitable bedrock volume for the extended repository. This will include the drilling and geoscientific evaluation of seven core-drilled and four percussion boreholes as well as subsequent interpretation and modelling based on the obtained results in order to provide the necessary information for safety assessment and repository design. This report presents a preliminary hydrogeochemical site description for the SFR site and should be considered as an early progress report rather than a complete hydrochemical site descriptive model. The completed hydrogeochemical field investigations have yielded chemical data from a total of 12 borehole sections in five boreholes and additional data from the entire length of two open boreholes in connection with hydraulic tests. These data, together with data from a total of 18 early boreholes in the present SFR tunnel system, were used in the interpretation work. The main part of the data consisted of basic groundwater analyses including major ions and isotopes. Some sporadic gas, microbe and measured redox data are
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Nilsson, Ann-Chatrin;
[1]
Tullborg, Eva-Lena;
[2]
Smellie, John
[3]
- Geosigma AB, Uppaala (Sweden)
- Terralogica AB, Graabo (Sweden)
- Conterra AB, Partille (Sweden)
Citation Formats
Nilsson, Ann-Chatrin, Tullborg, Eva-Lena, and Smellie, John.
Preliminary Hydrogeochemical Site Description SFR (version 0.2).
Sweden: N. p.,
2010.
Web.
Nilsson, Ann-Chatrin, Tullborg, Eva-Lena, & Smellie, John.
Preliminary Hydrogeochemical Site Description SFR (version 0.2).
Sweden.
Nilsson, Ann-Chatrin, Tullborg, Eva-Lena, and Smellie, John.
2010.
"Preliminary Hydrogeochemical Site Description SFR (version 0.2)."
Sweden.
@misc{etde_1004323,
title = {Preliminary Hydrogeochemical Site Description SFR (version 0.2)}
author = {Nilsson, Ann-Chatrin, Tullborg, Eva-Lena, and Smellie, John}
abstractNote = {The final repository for low and intermediate level radioactive operational waste, SFR, located about 150 km north of Stockholm, is to undergo a future extension. The present on-going project, scheduled from 2007 to 2011, is to define and characterise a suitable bedrock volume for the extended repository. This will include the drilling and geoscientific evaluation of seven core-drilled and four percussion boreholes as well as subsequent interpretation and modelling based on the obtained results in order to provide the necessary information for safety assessment and repository design. This report presents a preliminary hydrogeochemical site description for the SFR site and should be considered as an early progress report rather than a complete hydrochemical site descriptive model. The completed hydrogeochemical field investigations have yielded chemical data from a total of 12 borehole sections in five boreholes and additional data from the entire length of two open boreholes in connection with hydraulic tests. These data, together with data from a total of 18 early boreholes in the present SFR tunnel system, were used in the interpretation work. The main part of the data consisted of basic groundwater analyses including major ions and isotopes. Some sporadic gas, microbe and measured redox data are available, but these are either not treated in this report, or are only briefly discussed. This was due to time constraints since special care is needed when interpreting few data of varying quality. The groundwaters in the SFR dataset cover a maximum depth down to about .400 masl and represent a relatively limited salinity range (1,500 to 5,500 mg/L chloride). However, the delta18O values show a wide variation (-1.55 to -0.75% V-SMOW) similar to that reported from the Forsmark site investigations. At the SFR, marine indicators such as Mg/Cl, K/Cl and Br/Cl also show relatively large variations considering the limited salinity range. From very few measured Eh values, and in accordance with the chemistry of Fe, Mn, S and U, it is concluded that mildly reducing conditions (.140 to .190 mV) generally prevail in the investigated groundwaters. This is in line with measured Eh values in brackish marine waters of Littorina type from the site investigations in Forsmark and Laxemar (PLU). Hydrogeochemical observations together with palaeoclimatic considerations were used to differentiate the groundwaters into four major types; 1) local Baltic Sea water type, 2) Littorina type water with a glacial component, 3) brackish glacial water type, and 4) mixed brackish water (transition type). Explorative analyses using traditional geochemical approaches have been performed to describe groundwater conditions (origin and evolution) and other properties (mixing and reactions) in more detail. The division into groundwater types has facilitated interaction and integration with the hydrogeological models making it possible to construct a hydrogeochemical site descriptive model for the SFR site. The distribution of the different groundwater types shows that the major deformation zones have served as important groundwater flow pathways over long periods of geological time while single fractures in rock volumes between zones generally contain older and more isolated groundwater. Presently, the steeply dipping structures in particular have facilitated the drawdown of modern Baltic Sea water which has been observed since excavation and construction of the SFR some twenty years ago. Understanding the evolution of the groundwater system over time, i.e. since the last glaciation and more recently since excavation and construction of the SFR repository, shows that: 1) present-day hydraulic conditions have preserved groundwater patterns which replicate to a large extent what will occur during the next deglaciation (long-term perspective), and 2) the future impact of extended excavations and underground construction on groundwater chemistry can be predicted from past to present-day observations at the SFR site (short-term perspective)}
place = {Sweden}
year = {2010}
month = {May}
}
title = {Preliminary Hydrogeochemical Site Description SFR (version 0.2)}
author = {Nilsson, Ann-Chatrin, Tullborg, Eva-Lena, and Smellie, John}
abstractNote = {The final repository for low and intermediate level radioactive operational waste, SFR, located about 150 km north of Stockholm, is to undergo a future extension. The present on-going project, scheduled from 2007 to 2011, is to define and characterise a suitable bedrock volume for the extended repository. This will include the drilling and geoscientific evaluation of seven core-drilled and four percussion boreholes as well as subsequent interpretation and modelling based on the obtained results in order to provide the necessary information for safety assessment and repository design. This report presents a preliminary hydrogeochemical site description for the SFR site and should be considered as an early progress report rather than a complete hydrochemical site descriptive model. The completed hydrogeochemical field investigations have yielded chemical data from a total of 12 borehole sections in five boreholes and additional data from the entire length of two open boreholes in connection with hydraulic tests. These data, together with data from a total of 18 early boreholes in the present SFR tunnel system, were used in the interpretation work. The main part of the data consisted of basic groundwater analyses including major ions and isotopes. Some sporadic gas, microbe and measured redox data are available, but these are either not treated in this report, or are only briefly discussed. This was due to time constraints since special care is needed when interpreting few data of varying quality. The groundwaters in the SFR dataset cover a maximum depth down to about .400 masl and represent a relatively limited salinity range (1,500 to 5,500 mg/L chloride). However, the delta18O values show a wide variation (-1.55 to -0.75% V-SMOW) similar to that reported from the Forsmark site investigations. At the SFR, marine indicators such as Mg/Cl, K/Cl and Br/Cl also show relatively large variations considering the limited salinity range. From very few measured Eh values, and in accordance with the chemistry of Fe, Mn, S and U, it is concluded that mildly reducing conditions (.140 to .190 mV) generally prevail in the investigated groundwaters. This is in line with measured Eh values in brackish marine waters of Littorina type from the site investigations in Forsmark and Laxemar (PLU). Hydrogeochemical observations together with palaeoclimatic considerations were used to differentiate the groundwaters into four major types; 1) local Baltic Sea water type, 2) Littorina type water with a glacial component, 3) brackish glacial water type, and 4) mixed brackish water (transition type). Explorative analyses using traditional geochemical approaches have been performed to describe groundwater conditions (origin and evolution) and other properties (mixing and reactions) in more detail. The division into groundwater types has facilitated interaction and integration with the hydrogeological models making it possible to construct a hydrogeochemical site descriptive model for the SFR site. The distribution of the different groundwater types shows that the major deformation zones have served as important groundwater flow pathways over long periods of geological time while single fractures in rock volumes between zones generally contain older and more isolated groundwater. Presently, the steeply dipping structures in particular have facilitated the drawdown of modern Baltic Sea water which has been observed since excavation and construction of the SFR some twenty years ago. Understanding the evolution of the groundwater system over time, i.e. since the last glaciation and more recently since excavation and construction of the SFR repository, shows that: 1) present-day hydraulic conditions have preserved groundwater patterns which replicate to a large extent what will occur during the next deglaciation (long-term perspective), and 2) the future impact of extended excavations and underground construction on groundwater chemistry can be predicted from past to present-day observations at the SFR site (short-term perspective)}
place = {Sweden}
year = {2010}
month = {May}
}