Introduction
This paper provides the guidelines on how to develop a model that suits different geological formations for disposing of nuclear waste products. It includes an analysis of different situations that provides the geological understanding of the potential sites using different software tools to conduct the study. In addition, the paper uses overall work packages for automated analysis of the tools and processes used for the development of the model. In addition, the paper is divided into six sections and each section makes significant contributions to the modeling process by providing a detailed description of the model and the underpinning procedures for creating radioactive waste disposal zones. The introduction section is characterized by a systematic and logical sequence of procedures necessary for data collection, processing, interpretation, and integration into the model. On the other hand, the module provides a communication framework and identifiable best practices for sharing data with the stakeholders responsible for taking the necessary actions including the government to protect the environment from the effects of radioactive wastes by formulating policies for the disposal of waste products. In addition, the government formulates the necessary legal framework that is used to identify, model, and prepare the potential sites based on knowledge and data on the geological formation of the site.
Objectives
Miller, Chapman, McKinley, Alexander, and Smellie (2011) reviewed the research objectives that were used as the framework to write the report by comparing the report with recent findings in the area of study. The results of the review showed that the report is up-to-date and the objectives were well articulated. However, et al. (2011) observed that the research paper should have been logically organized to avoid making a repetition of the objectives. Miller et al. (2011) affirmed that the paper meets the minimum standard requirements for developing the model by categorizing the modeling into the three key components, which include geology, hydrogeology, and hydrochemistry to define the characteristics of the rocks that were used to generate the modeling data.
Approach
A critical review of the paper leads to the conclusion that studies by different researchers on modeling geological sites for the disposal of radioactive wastes agree with the methodology used in this paper. Most of the methodologies used to model the repository of rocks use different categories of rocks that are evaluated before the disposal site is prepared especially those that are in the RWMD in the UK. Here, the three core potential characteristics of the rocks that have been identified as potential candidates for the waste preparation sites include the higher strength rocks from the geological geometry of rocks found in the UK, the behavior of the rocks because of the movement of fluids and other liquid wastes stored in the rocks, and the safe storage and disposal of waste materials. The study shows that the article investigated the potentiality of lower strength sedimentary rocks on the appropriateness to store radioactive wastes and for their consistency with the geological formation of rocks in the UK.
Some of the elements that were used in the model, known as evaporates were established to originate from salts and other hydrates, which contaminate stationary or flowing underground water, increasing the vulnerability of those who use water to the harmful effects on the health and the environment. Overall rating of the paper based on previous research in the same area leads to the conclusion that the paper meets the necessary threshold required for a sufficiently researched paper on the most appropriate tools and procedures for the UK to apply when modeling waste disposal sites. The key areas of investigation, based on the research by different authors have been exhaustively discussed in the paper.
Originality
The author tried to make the paper to be original. However, there is evidence of heavy borrowing from different authors and institutions and other sources in writing the paper (Chapman & Mc Kinley, 1987). It is clear that Chapman and Mc Kinley (1987) considered different types of geological structures as the storage areas for different waste products from different countries. However, such information was obtained as the best practice for the application, interpretation and modeling of geological information using data generated from studies conducted on topographical, geomorphological and geological characteristics of the areas of study.
Article Review
Analytical summary
Analytically, the investigation was based on the UK’s geological background and policies and laws that govern the identification of areas for the disposal of nuclear wastes to ensure that they are consistent with the best practices for storing nuclear wastes. The study is in agreement with most of the low-level radioactive waste (LLW) methods and packages that were part of the waste disposal program. Previous research factored in the use of the deep geological disposal methods and the other study considered the use of land-based disposal methods. However, it is fair to note that the present modeling makes both HLW and the LLW to be inclusive in the process because they have widely been recommended as the right waste disposal methods in many countries. It is clear that the location of geological faults and repositories that were modeled into the construction of deep and shallow waste disposal sites should be investigated to understand the geological characteristics of disposal sites that could be developed in such geological areas. By conducting a feasibility study to develop the waste disposal sites, the methodology is in agreement with the approaches that have been investigated and practiced in many countries including the USA.
The geological survey of the countries provides sufficient data about the caverns and the chemical composition of the soils and rocks to map and model the shallow and deep waste disposal sites. For instance, France provides a model for waste disposal under clay soils. On the other hand, Sweden’s model is based on diameter vertical or horizontal boreholes that are drilled underground to create galleries that are 450 meters deep. The model used in Sweden is based on a detailed descriptive model based on an environmental impact assessment that provides a detailed analytical report of the thermal properties, rock mechanics, and the “hydrogeology, hydro-geochemistry, bedrock transport properties and a description of the surface system”. On the other hand, Finland uses vertical disposal boreholes at a depth of 600 meters, but other models use are deeper underground tubes or channels drilled several meters below the ground. Here, the general concept is to use a deep storage site the underground that provides safer storage of the waste materials.
Appropriateness of the article
The article provides a synthesis of different models with empirical evidence of the tools that have been used in different situations such as the geological nature of the tools to determine the rock formations that have been worked on. The criticism of the methods is that most of the tools and assessment methods were done using tools that were available in 1981 and 1997. However, the long term use of the methods and evidence of suitability makes the approach proposed by Chapman and Mc Kinley (1987) suitable for modeling the different components used to investigate the hydrogeology, hydrochemistry and engineering of suitable methods that could be used to model the disposal of the waste materials in the UK.
The general mapping of the region that was followed by the district, site, and the Potential Repository Zone (PRZ) facilitates the process of creating a logical model for mapping details of the limited surface exposure of the land using the visible surface. It is evident in the model that the boreholes and mine plans have been investigated using limited geological data based on an interpretation of the geophysical data. The main problem here was that the results were represented in a 2D model that fails to meet the criteria for combining different data sets to create a complete model. However, further investigations show that the model was later revised to create a more robust model that defines every aspect of the mapping and data integration process by making the interpretation of the data sets used to make the conclusion on the study. An investigation by Hadermann and Heer (1996) shows that the topographical investigation was based on the OS 1:50,000 topographic data, which is sufficient to explain the standard application of the measures necessary to ensure correct data was used. In addition, the model provides the true vertical depths that need to be factored into the entire modeling process because different elements represent different attributes and one of the most critical attributes is the vertical depth from the surface to ensure safe storage of nuclear waste materials.
However, it is worth noting that the mapping was done using traditional methods and such an approach lacked the use of modern advanced and sensitive tools and equipment and information that was generated using the tools was deemed not to be up-to-date. However, the mapping was made accurate by the use of BGS procedures that rely on the quality of the Intergraph software, which uses digital map drafting. It is also evident that some work was done by the use of the Quaternary fieldwork program (Ojovan & Lee, 2013). The overall, it is worth suggesting that mapping needs to be done dynamically to evaluate and update the modeling process using up-to-date software versions and modern mapping technologies.
Basement rocks
The exploration of the basement rocks is another area that was adequately covered because the structure and nature of the rocks were critical when evaluating the suitability of the area for disposing of the nuclear wastes. The rock formation can either be strong or weak tectonic forces and the potential to damage the storage facilities depends on the strength of the rocks to resist the action of the forces. It is evident that the model shows that the Borrowdale Volcanic Group – BVG can be exposed to the sea and that makes it the perfect place for the disposal of the nuclear wastes because the tectonic forces act towards the sea at the point where pressure and energy are released, leaving little or no damage to the storage facilities. The article claims that the “Geological mapping of the western part of the Lake District” was in agreement with the argument by Saltelli and Tarantola (2002), which provides rich information about the entire volcanic faults of the target region and information of the geological survey to determine the vulnerability of the area to natural forces such as earthquakes.
Here, the key data sets that were used to determine the suitability of the site include the Gibb Deep Geology Group on-site, BGS off-site that defined the Core logs, the Borehole Televiewer (BHTV), and the Core photographs. It is evident that the model factored the deep survey of the rocks and soils to determine the most suitable depths to store the waste materials. However, it is evident that no samples of the rocks or the soils were collected for laboratory analysis at this point. In addition, the data affects the confidence that could be derived from the use of the data for geological mapping and drilling of storage boreholes.
On the other hand, the article provides a detailed discussion of the integration of boreholes using the data from the GeoQuest workstation. The critical elements considered in this case were the datasets, the lithological logs of seismic velocities, and the fault position of the rocks. The adequacy of the interpretation and use of the data was evident at the point where the results showed that the fault patterns can be caused by seismic activities from different directions. In addition, offshore and onshore data integration using data generated from the contour map of average velocity, different velocity maps, and the seismic maps does not provide sufficient data to allow for adequate confidence in the use of the results to create the boreholes or to be adequately sure that the mapping is effective for use. The findings are in agreement with the study conducted by Valsala, Roy, Shah, Gabriel, Raj and Venugopal (2009) that the data gaps that appear in the case of seismic activities need to be addressed effectively.
The methodology used to evaluate the sedimentary rocks and other rock formations made adequate representation of facts because the process relied on information gathered from research that had been conducted in the same area covering the three main objectives stated in the study. However, a weakness arises because the software used could not allow for 3D modeling, which is an important component of the study. The strategy for using domain maps provides sufficient data to model the process, but it is recommended that future studies integrate the software with the 3D capabilities to ensure adequate modeling of the rocks for safe disposal of nuclear wastes.
Geological structure of the Sellafield was modeled using several software packages that do not provide evidence of the suitability of the packages in modeling the geology of different areas. However, evidence of new data based on the modeling software shows the reliability of the tools and the confidence in the results. In addition, the sources of data are adequate for the model. However, there is no description of the data was obtained for use and the degree of confidence and reliability in the modeling process (List, Mirchandani, Turnquist & Zografos, 1991). Despite the weakness, it is evident that the data from different sources were combined to create a 3D model using the VULCAN and earthVision software because the software uses the triangulated mesh system to address the gap in data using stratigraphic surfaces. By combing both the earthVision and VULCAN capabilities, it was possible to obtain the right 3D model for the Potential Repository Zone (Rutqvist, Wu, Tsang, & Bodvarsson, 2002). However, the modeling solutions do not provide any detailed study of alternative solutions that include the use of other software products and no comparison of data sets that are done on different software products to model the potential repository zone.
The modeling is rich in content on the mineral deposits that are within the Potential Repository Zone. The study provides the fracture orientation of the mining sites, the spatial heterogeneity, spatial variability, and the rock mass properties have been discussed in detail to ensure a comprehensive summary of information about the appropriateness of the area of study for waste disposal. However, the study falls short of proving the chemical composition of the substances the reactive nature when exposed to the storage material used to make the storage tanks and how that could affect the safety of the waste materials. However, the mention of the use of the core samples to conduct in situ tests confirms the dependability of the results that were used to do the modeling.
Other areas of study that provided sufficient data for the modeling include an investigation into the tectonic effects using expertise such as the Seismic Hazard Working Party (SHWP) to conduct hazard management issues because of the expertise on the various effects that earthquakes have had on the rocks. The in-situ stress has comprehensively been covered and the geotechnical modeling was done using expertise knowledge domains (Rutqvist, Wu, Tsang & Bodvarsson, 2002). Other issues covered include the safety of groundwater, the effects of natural and induced changes to the quality of water, and the techniques that are safe for designing and developing the repository.
Various examples shave been used to verify the model by comparing practical findings with empirical data based on practical evidence. The site descriptive models include attributes such as the underground layout, site-specific inputs, the thermal, geological and environmental impact assessment reports. The integrated geological model that has been applied when creating the site has been factored into the study. In comparison, the site descriptive model (SDM) used to create the model in use for the various sites that were investigated shows that results were comprehensive and appropriate for use in modeling a new site.
Additional models such as the local model area (and corresponding volume) provide a clear approach to use in modeling a specified local area that has been specified for creating the repository.
Conclusion
In conclusion, the investigation shows that geological modeling to determine the potential characteristics of a nuclear waste disposal zone was conducted in a comprehensive manner that was deemed satisfactory. Several issues such as the geomorphology of the site identified for the disposal of the wastes, the characteristics of the soils and rocks in which the material could be disposed of, the distribution and nature of the characteristic of the soil and sedimentary rocks, the software tools to use to map the target sites were done comprehensively. However, it is evident that some approaches such as the use of software to examine the topographical, geomorphological and geology of the target sites sometimes when doe using a 2D model and data that was not updated failed to update the model effectively. The modeling strategies were consistent with the modeling techniques and the sources of data were of good quality. On the other hand, the study used several case studies to demonstrate the characteristics and nature of the soils and sedimentary rock and the nature and scope of the disposal strategies that have been used everywhere to create the model. The number and depth of the boreholes used to create the storage sites could be very deep. For instance, the 29 deep boreholes in the Sellafield area demonstrate the reliability of the disposal modeling strategies. France provides another excellent model for the deep storage of nuclear wastes in a thick clay (mudstone) bed in the Paris basin that is 500 meters deep. The rock structure is defined by the thick succession of Jurassic strata that is sufficient to ensure compliance with the French policy on nuclear waste disposal. In Sweden, a site descriptive model (SDM) was developed after a large volume of data was collected and analyzed for the purpose of modeling the disposal site after a vigorous analysis of the data. However, the main weakness identified here is that the article fails to present empirical evidence on how accurate some software tools are in analyzing the data collected from different sites and how applicable the findings are in real-life situations. Some of the sources of data need to be updated to make the study current.
References
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Valsala, T. P., Roy, S. C., Shah, J. G., Gabriel, J., Raj, K., & Venugopal, V. (2009). Removal of radioactive caesium from low level radioactive waste (LLW) streams using cobalt ferrocyanide impregnated organic anion exchanger. Journal of hazardous materials, 166(2), 1148-1153.