Repository-Scale Modeling of the Long-Term Hydraulic Perturbation Induced by Gas and Heat Generation in a Geological Repository for High-and Intermediate-Level Radioactive Waste: Methodology and Example of Application

2011 ◽  
Vol 90 (1) ◽  
pp. 77-94 ◽  
Author(s):  
Andreas Poller ◽  
Carl Philipp Enssle ◽  
Gerhard Mayer ◽  
Jean Croisé ◽  
Jacques Wendling
Keyword(s):  
Radioactive Waste ◽  
Heat Generation ◽  
Intermediate Level ◽  
Scale Modeling ◽  
Geological Repository ◽  
Intermediate Level Radioactive Waste

The Management of Historic Intermediate Level Radioactive Waste in the United Kingdom

2003 ◽  
Author(s):  
David Horsley ◽  
Bruce McKirdy
Keyword(s):  
United Kingdom ◽  
Radioactive Waste ◽  
Waste Management ◽  
Storage Conditions ◽  
Intermediate Level ◽  
The United Kingdom ◽  
Environmentally Sound ◽  
Intermediate Level Radioactive Waste ◽  
The Uk

Nirex is the organisation responsible for long-term radioactive waste management in the UK. Our Mission is to provide the UK with safe, environmentally sound and publicly acceptable options for the long-term management of radioactive materials. The United Kingdom has a significant legacy of long-lived intermediate level radioactive waste. This has arisen from 50 years of investigation and exploitation of nuclear technology. Some of the waste is stored in old facilities that do not provide the standards of containment that would be incorporated in modern facilities. Also the risk to people and to the environment from the inventory in these facilities will increase with time as the structures age and degrade, increasing the chance of containment failure. There is, therefore, a need to retrieve this raw waste and process and package it to make it demonstrably safe for continued storage, pending a decision on disposal of radioactive waste. This packaging should, as far as is practicable, be compatible with the UK long-term waste management strategy. Nirex has developed its Phased Disposal Concept for intermediate and low-level radioactive waste. Based on that concept, Nirex has developed waste package specifications and carries out assessments of waste packaging proposals. For legacy wastes it may not always practicable to demonstrate full compliance with all Nirex disposal criteria. This paper describes an approach, agreed between Nirex and BNFL, for managing these wastes. The proposed approach takes account of long-term waste management issues whilst recognising the need for timely improvement of storage conditions.

Numerical Assessment of the Long-Term Safety of the Morsleben Repository for Low- and Intermediate-Level Radioactive Waste

2009 ◽  
Author(s):  
Ju¨rgen Wollrath ◽  
Ju¨rgen Preuss ◽  
Dirk-A. Becker ◽  
Jo¨rg Mo¨nig
Keyword(s):  
Radioactive Waste ◽  
Radiation Protection ◽  
Total Activity ◽  
Intermediate Level ◽  
Probabilistic Uncertainty ◽  
Numerical Assessment ◽  
Safety Case ◽  
Calculation Results ◽  
Intermediate Level Radioactive Waste

The Morsleben repository has been in operation since 1971 as a repository for low- and intermediate-level radioactive waste. Until the end of the disposal phase in 1998 a waste volume of about 37,000 m3 with a total activity of 4.5·1014 Bq was disposed of. Currently, the German Federal Office for Radiation Protection (BfS) is applying for the licence to finally close the repository. Concerning the possible release of radionuclides to the biosphere, the repository is subject to German radiation protection regulations. Their fulfilment has to be proven by means of numerical calculations as a part of the safety case. A simplified repository model has been developed by GRS and used for calculating the consequences of different scenarios and variants, as well as for a probabilistic uncertainty and sensitivity analysis. The application for licensing is, among others, based on these results. In this paper the main features of the model and the underlying assumptions, as well as the most important calculation results are presented and explained.

The Hydrogeologic Environment for a Proposed Deep Geologic Repository in Canada for Low and Intermediate Level Radioactive Waste

2011 ◽  
Author(s):  
Jonathan F. Sykes ◽  
Stefano D. Normani ◽  
Yong Yin ◽  
Mark R. Jensen
Keyword(s):  
Radioactive Waste ◽  
Solute Transport ◽  
Regional Scale ◽  
Intermediate Level ◽  
Geologic Repository ◽  
Site Specific ◽  
Ordovician Limestone ◽  
Intermediate Level Radioactive Waste ◽  
The Impact

A Deep Geologic Repository (DGR) for low and intermediate level radioactive waste has been proposed by Ontario Power Generation for the Bruce nuclear site in Ontario, Canada. As proposed the DGR would be constructed at a depth of about 680 m below ground surface within the argillaceous Ordovician limestone of the Cobourg Formation. This paper describes the hydrogeology of the DGR site developed through both site characterization studies and regional-scale numerical modelling analysis. The analysis provides a framework for the assembly and integration of the site-specific geoscientific data and examines the factors that influence the predicted long-term performance of the geosphere barrier. Flow system evolution was accomplished using both the density-dependent FRAC3DVS-OPG flow and transport model and the two-phase gas and water flow computational model TOUGH2-MP. In the geologic framework of the Province of Ontario, the DGR is located on the eastern flank of the Michigan Basin. Borehole logs covering Southern Ontario combined with site-specific data from 6 deep boreholes have been used to define the structural contours and hydrogeologic properties at the regional-scale of the modelled 31 sedimentary strata that may be partially present above the Precambrian crystalline basement rock. The regional-scale domain encompasses an approximately 18500km2 region extending from Lake Huron to Georgian Bay. The groundwater zone below the Devonian includes units containing stagnant water having high concentrations of total dissolved solids that can exceed 300g/L. The Ordovician sediments are significantly under-pressured. The horizontal hydraulic conductivity for the Cobourg limestone is estimated to be 2 × 10−14 m/s based on straddle-packer hydraulic tests. The low advective velocities in the Cobourg and other Ordovician units result in solute transport that is diffusion dominant with Peclet numbers less than 0.003 for a characteristic length of unity. Long-term simulations that consider future glaciation scenarios include the impact of ice thickness and permafrost. Solute transport in the Ordovician limestone and shale was diffusion dominant in all simulations. The Salina formations of the Upper Silurian prevented the deeper penetration of basal meltwater.

Development of Low-pH Cements for Immobilisation of Intermediate Level Radioactive Waste: Achievements and Challenges

2013 ◽  
Author(s):  
Regeane Martins de Freitas ◽  
Abir Al-Tabbaa
Keyword(s):  
Radioactive Waste ◽  
Low Ph ◽  
Intermediate Level ◽  
Pore Waters ◽  
New Materials ◽  
Waste Forms ◽  
Potential Alternative ◽  
Intermediate Level Radioactive Waste ◽  
Modelling Approach

Although cementation is a widely recognized solidification/stabilization process for immobilisation of Intermediate Level Radioactive Waste (ILRW), the low resistance to hyperalkaline pore waters compromises the effectiveness of the process when Portland Cement (PC) is employed. Moreover the manufacture of PC is responsible for significant CO2 emissions. In this context, low pH cements are environmentally more suitable and have emerged as a potential alternative for obtaining secure waste forms. This paper summarises the achievements on development of low-pH cements and the challenges of using these new materials for the ILRW immobilisation. The performance of waste forms is also discussed in terms of radionuclides release. Reactive magnesium oxide and magnesium phosphate cements are emphasised as they feature important advantages such as consumption of available constituents for controlling acid-base reactions, reduced permeability and higher density. Additionally, in order to identify new opportunities for study, the long-term modelling approach is also briefly discussed.

Hydrogeologic Modelling in Support of a Proposed Deep Geologic Repository in Canada for Low and Intermediate Level Radioactive Waste

2009 ◽  
Author(s):  
Jonathan F. Sykes ◽  
Stefano D. Normani ◽  
Yong Yin ◽  
Eric A. Sykes ◽  
Mark R. Jensen
Keyword(s):  
Life Expectancy ◽  
Radioactive Waste ◽  
Flow System ◽  
Regional Scale ◽  
Performance Measure ◽  
Intermediate Level ◽  
Geologic Repository ◽  
Site Specific ◽  
Intermediate Level Radioactive Waste

A Deep Geologic Repository (DGR) for Low and Intermediate Level radioactive waste has been proposed by Ontario Power Generation for the Bruce Nuclear Power Development site in Ontario, Canada. The DGR is to be constructed at a depth of about 680 m below ground surface within the argillaceous Ordovician limestone of the Cobourg Formation. This paper describes a regional-scale geologic conceptual model for the DGR site and analyzes flow system evolution using the FRAC3DVS-OPG flow and transport model. This provides a framework for the assembly and integration of site-specific geoscientific data that explains and illustrates the factors that influence the predicted long-term performance of the geosphere barrier. In the geologic framework of the Province of Ontario, the Bruce DGR is located at the eastern edge of the Michigan Basin. Borehole logs covering Southern Ontario combined with site specific data have been used to define the structural contours at the regional and site scale of the 31 sedimentary strata that may be present above the Precambrian crystalline basement rock. The regional-scale domain encompasses an 18.500km2 region extending from Lake Huron to Georgian Bay. The groundwater zone below the Devonian is characterized by units containing stagnant water having high concentrations of total dissolved solids that can exceed 300g/l. The computational sequence involves the calculation of steady-state density independent flow that is used as the initial condition for the determination of pseudo-equilibrium for a density dependent flow system that has an initial TDS distribution developed from observed data. Long-term simulations that consider future glaciation scenarios include the impact of ice thickness and permafrost. The selection of the performance measure used to evaluate a groundwater system is important. The traditional metric of average water particle travel time is inappropriate for geologic units such as the Ordovician where solute transport is diffusion dominant. The use of life expectancy and groundwater age is a more appropriate metric for such a system. The mean life expectancy for the DGR and base case parameters has been estimated to be in excess of 8 million years.

scholarly journals Assessment of the climate changes evolution for the long-term safety of the radioactive waste repository in the Czech Republic

2019 ◽  
Vol 133 ◽  
pp. 02005
Author(s):  
Markéta Camfrlová
Keyword(s):  
Czech Republic ◽  
Radioactive Waste ◽  
Spent Nuclear Fuel ◽  
Global Climate ◽  
Deep Geological Repository ◽  
Climatic Effects ◽  
The Czech Republic ◽  
Area Of Interest ◽  
Geological Repository

Nuclear energy accounts for a significant part of the total energy production in the Czech Republic, which is currently facing a problem dealing with the high-level radioactive waste (HLW) and the spent nuclear fuel (SNF). Deep repository is the safest option for storage of HLW. Rock environment of the area must guarantee the stability of the deep geological repository for at least 100,000 years. The aim of the research is a long-term evaluation of the climatic changes of the hypothetical area of interest, which corresponds to the candidate sites for deep geological repository in the Czech Republic. The occurrences of endogenous and exogenous phenomena, which could affect site stability, were evaluated. Concerning exogenous processes, research focuses mainly on the assessment of climatic effects. The climate scenarios for the Central Europe were examined – global climate change, glaciation, and the depth of permafrost as well as CO2 increase.

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