Thesis Format
Integrated Article
Degree
Master of Science
Program
Civil and Environmental Engineering
Supervisor
El Naggar, M. Hesham
Abstract
Canada is one of the leading countries in nuclear energy usage for the past 60 years. Intermediate and high levels nuclear waste need to be contained and isolated in a deep geological repository, DGR, (i.e., 500 to 800 m below the ground level), using a multiple-barrier isolation system. Gap Fill Material (GFM) is a Bentonite based material that will be used to backfill the remaining spaces between the central bentonite blocks containing fuel waste containers and surrounding excavation walls. The Nuclear Waste Management Organization (NWMO) requires a simple and easy method to remotely determine the density of the GFM inside the DGR to ensure that it satisfies the density requirements, and consequently, limits the radiation of buried nuclear fuel into the surrounding environment. Several direct and indirect density measurement techniques were investigated, and a comprehensive laboratory testing program was performed. The program includes 277 Shear wave velocity and 59 Cone Penetration Tests on GFM samples with densities between 1.45 and 1.8 g/cm3. The results indicate strong relationships and provide some correlations between the GFM density, shear wave velocity, and cone penetration resistance. The laboratory results were then used to develop 5 artificial neural networks employing regression tool in MATLAB software with a high correlation coefficient (R-value) between the measured and predicted output variables.
Summary for Lay Audience
Canada is one of the leading countries using nuclear energy for powering residential and business buildings. In addition to electricity generation, nuclear technology is also used for medical purposes (e.g., cancer treatment), in food and agriculture (e.g., food irradiation) and in many industrial processes. The resulting nuclear waste can be classified into three radioactive categories (i.e., low, intermediate, and high-level waste). Both intermediate and high-level waste needs to be contained and isolated in very deep geological repositories, DGR, (i.e., 500 to 800 m below the ground level), using a multiple-barrier isolation system. A Bentonite based Gap Fill Material (MX-80 bentonite) will be used to fill the gaps between central bentonite blocks containing the Used Fuel Containers (UFCs) and the excavation walls. The main objective of this study is to identify and develop a suitable, reliable, and easy to use method to measure the density of the GFM inside the DGR. Providing a suitable method to measure the as-placed density of the GFM will allow the Nuclear Waste Management Organization (NWMO) to ensure that the used GFM satisfies the density requirements, and consequently, limit the radiation of the buried nuclear fuel into the surrounding environment. It is understood that the method used in a production setting will need to be carried out remotely since there will be no access for personal during placement of Buffer Boxes and GFM in the placement room (500 to 800 m below the ground surface) and these methods of testing must be straightforward, since complexity of testing will slow the overall placement process. Several direct and indirect density measurements techniques were investigated, and the regression method is recommended to estimate the GFM density inside the DGR. In the regression, the GFM density is correlated with other soil parameters that are readily available or can be easily estimated using simple testing techniques, such as shear wave velocity and CPT results Strong correlations were developed between the GFM density, shear wave velocity, and cone penetration resistance under similar testing conditions as those available inside the DGR.
Recommended Citation
Elzamel, Mai, "Determining the Variability of the As-Placed Dry Density of Gap Fill Material" (2023). Electronic Thesis and Dissertation Repository. 9676.
https://ir.lib.uwo.ca/etd/9676