Abstract
This report presents methodology and modelling results concerning a deep-rock repository for spent nuclear fuel in Forsmark. Specifically, the modelling tools MIKE SHE, MIKE 11 and MOUSE are used to quantify the groundwater inflow to the repository and associated hydrological and hydrogeological effects during the construction and operation phases. The modelling results presented in the report provide input to the Environmental Impact Assessment (EIA) that will be part of a permit application according to the Environmental Code. Based on an existing MIKE SHE model for Forsmark, the first step of the modelling process was to implement an updated hydrogeological model of the bedrock and to increase the vertical and horizontal extents of the model domain. Other model updates involve the vegetation classification, and implementation of SFR (final repository for short-lived radioactive waste) and the subsurface drainage system at the nearby nuclear power plant. The updated model was calibrated using measured data on groundwater levels in the Quaternary deposits and the bedrock, water levels in lakes, and stream discharges. The calibrated model was then used for simulation of undisturbed conditions (i.e. without the repository) as a reference for modelling results obtained for disturbed conditions (with the repository). The modelling results for
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Citation Formats
Maartensson, Erik, and Gustafsson, Lars-Goeran.
Hydrological and hydrogeological effects of an open repository in Forsmark. Final MIKE SHE flow modelling results for the Environmental Impact Assessment.
Sweden: N. p.,
2010.
Web.
Maartensson, Erik, & Gustafsson, Lars-Goeran.
Hydrological and hydrogeological effects of an open repository in Forsmark. Final MIKE SHE flow modelling results for the Environmental Impact Assessment.
Sweden.
Maartensson, Erik, and Gustafsson, Lars-Goeran.
2010.
"Hydrological and hydrogeological effects of an open repository in Forsmark. Final MIKE SHE flow modelling results for the Environmental Impact Assessment."
Sweden.
@misc{etde_1004324,
title = {Hydrological and hydrogeological effects of an open repository in Forsmark. Final MIKE SHE flow modelling results for the Environmental Impact Assessment}
author = {Maartensson, Erik, and Gustafsson, Lars-Goeran}
abstractNote = {This report presents methodology and modelling results concerning a deep-rock repository for spent nuclear fuel in Forsmark. Specifically, the modelling tools MIKE SHE, MIKE 11 and MOUSE are used to quantify the groundwater inflow to the repository and associated hydrological and hydrogeological effects during the construction and operation phases. The modelling results presented in the report provide input to the Environmental Impact Assessment (EIA) that will be part of a permit application according to the Environmental Code. Based on an existing MIKE SHE model for Forsmark, the first step of the modelling process was to implement an updated hydrogeological model of the bedrock and to increase the vertical and horizontal extents of the model domain. Other model updates involve the vegetation classification, and implementation of SFR (final repository for short-lived radioactive waste) and the subsurface drainage system at the nearby nuclear power plant. The updated model was calibrated using measured data on groundwater levels in the Quaternary deposits and the bedrock, water levels in lakes, and stream discharges. The calibrated model was then used for simulation of undisturbed conditions (i.e. without the repository) as a reference for modelling results obtained for disturbed conditions (with the repository). The modelling results for undisturbed conditions that are presented in the report closely resemble those of the final MIKE SHE site descriptive modelling (SDM-Site Forsmark). The repository layout was implemented as pipe links (segments) in the modelling tool MOUSE, and the implemented layout was used for the modelling of disturbed conditions. The study uses an updated and verified MIKE SHE-MOUSE coupling routine that is specifically adapted for calculation of groundwater inflow to grouted rock tunnels. The vertical shafts of the repository are implemented in the form of MIKE SHE grid cells with atmospheric pressure. Modelling results for disturbed conditions show that the magnitude and the geographical extent of the groundwater-table drawdown are smaller than the hydraulic-head drawdown in the bedrock. The influence area for the groundwater-table drawdown primarily coincides with locations where the Quaternary deposits are in contact with bedrock containing fracture zones with high vertical hydraulic conductivity. The groundwater inflow to the repository, the groundwater-table drawdown and the drawdown of hydraulic heads in the bedrock were analysed for different values of the hydraulic conductivity of the grouted zone (K{sub grout}) and also for layouts that aim to represent different repository-development phases. For a hypothetical case with a fully open repository, the model-calculated inflow is in the interval 15-47 L/s depending on the value of K{sub grout}. Using meteorological data and sea-level data for the year 2006, the associated influence area for the groundwater-table drawdown (annual average drawdown exceeding 0.3 m) has a size of 1.4 km2 for K{sub grout} = 10-7 m/s and less than half for K{sub grout} = 10-9 m/s. According to the modelling results, the groundwater inflow to the repository has very small effects on water levels in lakes and discharges in streams. However, for K{sub grout} = 10-7 m/s the annually accumulated discharge in the stream upstream from Lake Bolundsfjaerden is reduced by 13%, which is due to drawdown of the groundwater table within the catchment area of the stream. Sensitivity analyses show that the groundwater inflow to the repository and the size of the groundwater table influence area are not very sensitive to the tested variants concerning the hydrogeological properties of the upper 200 m of the bedrock and the boundary conditions (including the sea level). The model-calculated influence area demonstrates some sensitivity to the choice of methodology for modelling water flow in the unsaturated zone. Moreover, the influence area is larger if the hydrogeological properties in the upper 20 m of the model domain are the same as those used in a parallel DarcyTools modelling activity. According to the MIKE SHE modelling results, the inflow to a planned extension of SFR will have no or very limited impact on the inflow to the repository and also on the location of the groundwater table, compared to a situation with the repository and the present SFR layout. Moreover, results of so called particle tracking show that there is a low probability for spreading of water-soluble substances from the grouted zone to the ground surface. A simplified approach was used for modelling of the backfill saturation and the groundwater-level recovery subsequent to the operational phase of the repository. The results indicate that the location of the groundwater table will be fully recovered within a few years after termination of the groundwater diversion from the repository}
place = {Sweden}
year = {2010}
month = {Jul}
}
title = {Hydrological and hydrogeological effects of an open repository in Forsmark. Final MIKE SHE flow modelling results for the Environmental Impact Assessment}
author = {Maartensson, Erik, and Gustafsson, Lars-Goeran}
abstractNote = {This report presents methodology and modelling results concerning a deep-rock repository for spent nuclear fuel in Forsmark. Specifically, the modelling tools MIKE SHE, MIKE 11 and MOUSE are used to quantify the groundwater inflow to the repository and associated hydrological and hydrogeological effects during the construction and operation phases. The modelling results presented in the report provide input to the Environmental Impact Assessment (EIA) that will be part of a permit application according to the Environmental Code. Based on an existing MIKE SHE model for Forsmark, the first step of the modelling process was to implement an updated hydrogeological model of the bedrock and to increase the vertical and horizontal extents of the model domain. Other model updates involve the vegetation classification, and implementation of SFR (final repository for short-lived radioactive waste) and the subsurface drainage system at the nearby nuclear power plant. The updated model was calibrated using measured data on groundwater levels in the Quaternary deposits and the bedrock, water levels in lakes, and stream discharges. The calibrated model was then used for simulation of undisturbed conditions (i.e. without the repository) as a reference for modelling results obtained for disturbed conditions (with the repository). The modelling results for undisturbed conditions that are presented in the report closely resemble those of the final MIKE SHE site descriptive modelling (SDM-Site Forsmark). The repository layout was implemented as pipe links (segments) in the modelling tool MOUSE, and the implemented layout was used for the modelling of disturbed conditions. The study uses an updated and verified MIKE SHE-MOUSE coupling routine that is specifically adapted for calculation of groundwater inflow to grouted rock tunnels. The vertical shafts of the repository are implemented in the form of MIKE SHE grid cells with atmospheric pressure. Modelling results for disturbed conditions show that the magnitude and the geographical extent of the groundwater-table drawdown are smaller than the hydraulic-head drawdown in the bedrock. The influence area for the groundwater-table drawdown primarily coincides with locations where the Quaternary deposits are in contact with bedrock containing fracture zones with high vertical hydraulic conductivity. The groundwater inflow to the repository, the groundwater-table drawdown and the drawdown of hydraulic heads in the bedrock were analysed for different values of the hydraulic conductivity of the grouted zone (K{sub grout}) and also for layouts that aim to represent different repository-development phases. For a hypothetical case with a fully open repository, the model-calculated inflow is in the interval 15-47 L/s depending on the value of K{sub grout}. Using meteorological data and sea-level data for the year 2006, the associated influence area for the groundwater-table drawdown (annual average drawdown exceeding 0.3 m) has a size of 1.4 km2 for K{sub grout} = 10-7 m/s and less than half for K{sub grout} = 10-9 m/s. According to the modelling results, the groundwater inflow to the repository has very small effects on water levels in lakes and discharges in streams. However, for K{sub grout} = 10-7 m/s the annually accumulated discharge in the stream upstream from Lake Bolundsfjaerden is reduced by 13%, which is due to drawdown of the groundwater table within the catchment area of the stream. Sensitivity analyses show that the groundwater inflow to the repository and the size of the groundwater table influence area are not very sensitive to the tested variants concerning the hydrogeological properties of the upper 200 m of the bedrock and the boundary conditions (including the sea level). The model-calculated influence area demonstrates some sensitivity to the choice of methodology for modelling water flow in the unsaturated zone. Moreover, the influence area is larger if the hydrogeological properties in the upper 20 m of the model domain are the same as those used in a parallel DarcyTools modelling activity. According to the MIKE SHE modelling results, the inflow to a planned extension of SFR will have no or very limited impact on the inflow to the repository and also on the location of the groundwater table, compared to a situation with the repository and the present SFR layout. Moreover, results of so called particle tracking show that there is a low probability for spreading of water-soluble substances from the grouted zone to the ground surface. A simplified approach was used for modelling of the backfill saturation and the groundwater-level recovery subsequent to the operational phase of the repository. The results indicate that the location of the groundwater table will be fully recovered within a few years after termination of the groundwater diversion from the repository}
place = {Sweden}
year = {2010}
month = {Jul}
}