The Migration of Radionuclides with Ground Water. A Discussion of the Relevance of the Input Parameters used in Model Calculations

1981 ◽  
Vol 11 ◽  
Author(s):  
Bror Skytte Jensen
Keyword(s):  
Radioactive Waste ◽  
Ground Water ◽  
Chemical Processes ◽  
Model Calculations ◽  
Input Parameters ◽  
Long Term Performance ◽  
Term Performance ◽  
Physical And Chemical ◽  
Take All

The plans for the disposal of radioactive waste leave very little time for testing long term performance of a repository so the evaluation of the hazards involved in the operation relies heavily on model calculations. It is therefore of utmost importance that these model calculations take all important parameters into account and are based on a thorough understanding of the possible physical and chemical processes in which the migrating species take part.

The Theoretical Evaluation of Localised Corrosion in Radioactive Waste Canisters.

1986 ◽  
Vol 84 ◽  
Author(s):  
S.M. Sharland
Keyword(s):  
Experimental Data ◽  
Radioactive Waste ◽  
Growth Rates ◽  
Crevice Corrosion ◽  
Chemical Processes ◽  
Uniform Corrosion ◽  
Theoretical Evaluation ◽  
Input Parameters ◽  
Physical And Chemical

AbstractUnder repository conditions, it is likely that radioactive waste canisters will be subjected to both uniform and localised corrosion. Localised corrosion can take many forms depending on the precise physical and chemical environment of the metal at the time of attack, but generally the rates of penetration are much greater than those associated with uniform corrosion. The most likely forms under aerated repository conditions are pitting and crevice corrosion. To ensure adequate radionuclide containment an allowance for these rates must be included in the final canister dimensions. It is considered the best way to predict long term penetration rates is to develop mathematical models, which include all the physical and chemical processes necessary to describe the system and use experimentally determined input parameters relating to these processes. These models must then draw on further experimental data for validation over short timescales. In this paper, we discuss several techniques of modelling long term pit propagation in waste canisters. The complexity of the problem has lead to a number of physical and chemical approximations in the modelling. We investigate the applicability and ranges of validity of several of the more common approximations, both in our own models and in the literature, and compare the predictions with experimental pit growth rates. An investigatation of the sensitivity of the models to the various empirical input parameters indicates which need to be determined most accurately.

Acoustic Emission Monitoring of Cement-Based Structures Immobilising Radioactive Waste

2007 ◽  
Author(s):  
L. M. Spasova ◽  
M. I. Ojovan ◽  
M. Hayes ◽  
H. Godfrey
Keyword(s):  
Acoustic Emission ◽  
Radioactive Waste ◽  
Mechanical Performance ◽  
Cement Matrix ◽  
Properties Of Materials ◽  
Long Term Performance ◽  
Term Performance ◽  
Physical And Chemical ◽  
Non Destructive

The long term performance of cementitious structures immobilising radioactive waste can be affected by physical and chemical processes within the encapsulating materials such as formation of new phases (e.g., vaterite, brucite), degradation of cement phases (e.g., CSH gel, portlandite), degradation of some waste components (e.g., organics), corrosion of metallic constituents (aluminium, magnesium), gas emission, further hydration etc. The corrosion of metals in the high pH cementitious environment is of especial concern as it can potentially cause wasteform cracking. One of the perspective non-destructive methods used to monitor and assess the mechanical properties of materials and structures is based on an acoustic emission (AE) technique. In this study an AE non-destructive technique was used to evaluate the mechanical performance of cementitious structures with encapsulated metallic waste such as aluminium. AE signals generated as a result of aluminium corrosion in a small-size blast furnace slag (BFS)/ordinary Portland cement (OPC) sample were detected, recorded and analysed. A procedure for AE data analysis including conventional parameter-based AE approach and signal-based analysis was applied and demonstrated to provide information on the aluminium corrosion process and its impact on the mechanical performance of the encapsulating cement matrix.

scholarly journals Evolution of the Reaction and Alteration of Mudstone with Ordinary Portland Cement Leachates: Sequential Flow Experiments and Reactive-Transport Modelling

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1026
Author(s):  
Keith Bateman ◽  
Shota Murayama ◽  
Yuji Hanamachi ◽  
James Wilson ◽  
Takamasa Seta ◽  
...  
Keyword(s):  
Reactive Transport ◽  
Chemical Properties ◽  
Reactive Transport Modelling ◽  
Transport Modelling ◽  
General Sequence ◽  
Long Term Performance ◽  
Term Performance ◽  
Physical And Chemical ◽  
Flow Experiments

The construction of a repository for geological disposal of radioactive waste will include the use of cement-based materials. Following closure, groundwater will saturate the repository and the extensive use of cement will result in the development of a highly alkaline porewater, pH > 12.5; this fluid will migrate into and react with the host rock. The chemistry of the fluid will evolve over time, initially high [Na] and [K], evolving to a Ca-rich fluid, and finally returning to the groundwater composition. This evolving chemistry will affect the long-term performance of the repository, altering the physical and chemical properties, including radionuclide behaviour. Understanding these changes forms the basis for predicting the long-term evolution of the repository. This study focused on the determination of the nature and extent of the chemical reaction, as well as the formation and persistence of secondary mineral phases within a mudstone, comparing data from sequential flow experiments with the results of reactive transport modelling. The reaction of the mudstone with the cement leachates resulted in small changes in pH with the precipitation of calcium aluminium silicate hydrate (C-(A-)S-H) phases of varying compositions. As the system evolves, secondary C-(A-)S-H phases re-dissolve and are replaced by secondary carbonates. This general sequence was successfully simulated using reactive transport modelling.

The Long-Term Safety and Performance Analyses of the Surface Disposal Facility for the Belgian Category A Waste at Dessel

2013 ◽  
Author(s):  
Wim Cool ◽  
Elise Vermariën ◽  
William Wacquier ◽  
Janez Perko
Keyword(s):  
Radioactive Waste ◽  
Radiological Criteria ◽  
Disposal Facility ◽  
Safety Function ◽  
License Application ◽  
Performance Analyses ◽  
And Performance ◽  
Long Term Performance ◽  
Term Performance

ONDRAF/NIRAS, the Belgian Agency for Radioactive Waste and Enriched Fissile Materials, and its partners have developed long-term safety and performance analyses in the framework of the license application for a surface disposal facility for low level radioactive waste (category A waste) at Dessel, Belgium. This paper focusses on the methodology of the safety assessments and on key results from the application of this methodology. An overview is given (1) of the performance analyses for the containment safety function of the disposal system and (2) of the radiological impact analyses confirming that radiological impacts are below applicable reference values and constraints and leading to radiological criteria for the waste and the facility. In this discussion, multiple indicators for performance and safety are used to illustrate the multi-faceted nature of long-term performance and safety of the surface disposal. This contributes to the multiple lines of reasoning for confidence building that a positive decision to proceed to the next stage of construction is justified.

Web-Based Data Management System for Long-Term Performance Monitoring and Stewardship of a Low-Level Radioactive Waste Disposal Facility

2003 ◽  
Author(s):  
Craig H. Benson ◽  
Robert J. Tipton ◽  
Uday Kumthekar ◽  
J. D. Chiou
Keyword(s):  
Radioactive Waste ◽  
Performance Monitoring ◽  
Radioactive Waste Disposal ◽  
Data Management System ◽  
Web Based ◽  
Disposal Facility ◽  
Long Term Performance ◽  
Term Performance ◽  
Low Level Radioactive Waste

A web-based data management system is described that is being used for long-term performance monitoring and stewardship of a low-level radioactive waste disposal facility (LLRWDF) at the Fernald Closure Project (FCP) in Fernald, Ohio, USA. The system provides integrated data collection and management for monitoring performance of the liner and cover systems in the LLRWDF. Integrated performance monitoring data (meteorological, hydrological, geophysical, ecological, leachate flow, and leachate quality data) are presented and compared with performance criteria and action levels in near real-time. A status summary is also included for the site manager, regulators, and other stakeholders to provide an early warning regarding the need for corrective action.

Thermodynamic Modeling of Cement/Groundwater Interaction as a Tool For Long-Tern Performance Assessment

1989 ◽  
Vol 176 ◽  
Author(s):  
Louise J. Criscenti ◽  
R. Jeff Serne
Keyword(s):  
Radioactive Waste ◽  
Performance Assessment ◽  
Natural Environment ◽  
Chemical Behavior ◽  
Geochemical Model ◽  
The Past ◽  
Long Term Performance ◽  
Term Performance ◽  
Low Level Radioactive Waste

ABSTRACTThe chemical behavior of cement in the natural environment is of interest because cement has been suggested as a means of containing low-level radioactive waste and as a barrier between radioactive-waste containers and the surrounding soil or rock. In the past, either experiments or computer modeling have been used independently to predict how cement will leach in the natural environment. In this study, a geochemical model for cement leaching was developed, and predictions by the model were compared to results from a static leach test. Calcium concentrations and pH were adequately predicted by the model; however, other major leachate constituents, such as Al, Si, and S04, were poorly predicted. Additional experimental data and refinement of the model are both required to better predict the observed leachate concentrations. Accurate prediction of experimental results by a geochemical model would increase confidence in the model for use in long-term performance assessment.

Input Parameters for the Mechanistic-Empirical Design of Full-Depth Reclamation Projects

2021 ◽  
pp. 036119812110179
Author(s):  
Vishwa V. Beesam ◽  
Cristina Torres-Machi
Keyword(s):  
Pavement Design ◽  
Design Parameters ◽  
Future Research ◽  
Limited Information ◽  
Full Depth Reclamation ◽  
Input Parameters ◽  
Current Design ◽  
Long Term Performance ◽  
Term Performance

Cold recycling technologies such as full-depth reclamation (FDR) are sustainable and cost-effective techniques for pavement rehabilitation that reduce environmental impacts and construction costs and time. The limited information available on the material properties of FDR mixtures and their characterization in mechanistic-empirical (M-E) pavement design hinders the full deployment of FDR. Previous research has found current M-E default values to be non-representative and overly conservative, leading to an underestimation of the true performance capabilities of FDR materials. To address this gap, this paper analyzes the performance of 11 FDR sites constructed throughout Colorado, U.S., and compares their long-term performance with M-E predictions. The objective of this paper is to recommend input values for the M-E design of FDR base materials that result in reliable predictions of FDR long-term performance. The analysis includes both non-stabilized and emulsion-stabilized FDR projects. Both initial International Roughness Index (IRI) and resilient modulus were found to have a significant impact on M-E predictions and were calibrated in a two-step process. The proposed input parameters lead to a conservative design of FDR projects and result in improved IRI predictions compared with the ones derived from current design criteria. With the current design parameters, IRI predictions were, on average, overestimated by 51 in./mi, whereas the proposed input parameters make it possible to reduce this difference to 17 in./mi. Future research is needed to improve current models in M-E pavement design software to adequately model cold in-place recycled layers such as FDR.

scholarly journals Preliminary Performance Assessment for Deep Borehole Disposal of High-Level Radioactive Waste

2012 ◽  
Vol 1475 ◽  
Author(s):  
Peter N. Swift ◽  
Bill W. Arnold ◽  
Patrick V. Brady ◽  
Geoff Freeze ◽  
Teklu Hadgu ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Performance Assessment ◽  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
High Level Radioactive Waste ◽  
Deep Boreholes ◽  
High Level ◽  
Long Term Performance ◽  
Term Performance

ABSTRACTDeep boreholes have been proposed for many decades as an option for permanent disposal of high-level radioactive waste and spent nuclear fuel. Disposal concepts are straightforward, and generally call for drilling boreholes to a depth of four to five kilometers (or more) into crystalline basement rocks. Waste is placed in the lower portion of the hole, and the upper several kilometers of the hole are sealed to provide effective isolation from the biosphere. The potential for excellent long-term performance has been recognized in many previous studies. This paper reports updated results of what is believed to be the first quantitative analysis of releases from a hypothetical disposal borehole repository using the same performance assessment methodology applied to mined geologic repositories for high-level radioactive waste. Analyses begin with a preliminary consideration of a comprehensive list of potentially relevant features, events, and processes (FEPs) and the identification of those FEPs that appear to be most likely to affect long-term performance in deep boreholes. The release pathway selected for preliminary performance assessment modeling is thermally-driven flow and radionuclide transport upwards from the emplacement zone through the borehole seals or the surrounding annulus of disturbed rock. Estimated radionuclide releases from deep borehole disposal of spent nuclear fuel, and the annual radiation doses to hypothetical future humans associated with those releases, are extremely small, indicating that deep boreholes may be a viable alternative to mined repositories for disposal of both high-level radioactive waste and spent nuclear fuel.

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