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| DC Field | Value | Language |
|---|---|---|
| dc.contributor.advisor | Hisseine, Ousmane | - |
| dc.contributor.author | Anunike, Great | - |
| dc.date.accessioned | 2025-05-06T12:54:52Z | - |
| dc.date.available | 2025-05-06T12:54:52Z | - |
| dc.date.issued | 2025 | - |
| dc.identifier.uri | http://hdl.handle.net/11375/31618 | - |
| dc.description | In the global transition toward cleaner and more sustainable energy systems, nuclear power stands out as a critical tool for decarbonizing the energy sector. Recent developments indicate a resurgence in the adoption of nuclear energy, underscoring its growing relevance in the pursuit of low-carbon solutions. As concrete and steel together constitute approximately 95% of the material input in nuclear infrastructure, the integrity and resilience of nuclear facilities are closely tied to the performance of their concrete containment structures. In alignment with the safety objectives established by the International Atomic Energy Agency (IAEA), these containment systems must fulfill three essential safety functions: (i) confinement of radioactive materials, (ii) protection of the reactor from both natural and human-induced hazards, and (iii) effective shielding against radiation. Typically, nuclear containment structures are built using pre-stressed or reinforced concrete with steel liners. However, conventional concrete systems are susceptible to long-term degradation, particularly from freeze–thaw cycles, corrosion of reinforcement, and deterioration under high temperatures and internal pressures. These vulnerabilities pose significant risks to structural integrity, especially during severe operational conditions or accidents. To address these limitations and further enhance the safety margins of nuclear facilities, there is a growing imperative for the adoption of advanced concrete technologies, among which ultra-high-performance concrete (UHPC) has emerged as a highly promising option. UHPC is distinguished by its ultra-dense microstructure, exceptional mechanical toughness, and near-impermeability to aggressive agents, making it particularly well-suited for demanding environments such as nuclear containment. Its compact matrix contributes not only to improved durability but also to enhanced radiation shielding and leak-tightness. Moreover, the superior strength characteristics of UHPC enable the construction of slimmer containment walls, offering both safety and design advantages over traditional concrete systems. | en_US |
| dc.description.abstract | Nuclear energy is a fundamental component in the global transition to cleaner energy sources. Within this context, concrete serves as the key protective barrier in nuclear facilities. To advance the safety and security of such infrastructures, this research centers on the development of radiation shielding ultra-high-performance concrete (RS-UHPC), engineered for superior mechanical and radiation shielding efficiency. Firstly, two comprehensive reviews were undertaken to critically assess the formulation and performance characteristics of RS-UHPC based on existing scattered and fragmented literature on the topic. Secondly, machine learning (ML) datadriven modeling was pursued to assess the influential parameters on RS-UHPC performance, particularly gamma linear attenuation coefficient (µ). Among all models, the Random Forest and XG Boost models demonstrated superior predictive accuracy, achieving high R² values of 81% and 77%, respectively, and low error metrics. Lastly, an experimental program was implemented to develop an advanced RS-UHPC through a two-phase optimization (mortar to composite level). This approach integrated dry-wet particle packing density optimization with optimal custom mixture design (OCMD) to investigate the combined influence of magnetite, ilmenite, and ferroboron on RS-UHPC. The resulting optimized RS-UHPC mortar, demonstrated a 49% increase in density, a 44% improvement in µ, a 37% increase in fast neutron (∑R), and a 681% increase in thermal neutron (∑abs). At the composite level, the incorporation of steel fibres (up to 3% vol.) enhanced the ∑R by over 61%, the µ by 9%, and the 7-day f’c by 26% while maintaining stable ∑abs compared to the optimized UHPC mortar. Moreover, the RS-UHPC composite enhanced the ∑R by over 120%, the µ by 57%, the 7-day f’c by 36%, and the ∑abs by nearly 700% when compared to the quartz sand-based reference mortar. | en_US |
| dc.language.iso | en | en_US |
| dc.subject | Heavyweight aggregates; Mix design; Nuclear safety; Nuclear radiation; Radiation shielding; Ultra-high-performance concrete (UHPC) | en_US |
| dc.subject | Durability, Elevated temperature; Heavyweight aggregates; Mechanical performance; Nuclear radiations; Nuclear safety; Radiation shielding; Rheology; Ultra-highperformance concrete (UHPC) | en_US |
| dc.subject | composite; ferroboron; ilmenite; magnetite; mixture design; mortar; nuclear energy; optimal custom design, particle packing optimization; radiation shielding; response surface methodology; ultra-high-performance concrete | en_US |
| dc.title | DRY-WET PACKING OPTIMIZATION OF ULTRAHIGH-PERFORMANCE CONCRETE FOR RADIATION SHIELDING: UNVEILING THE INTERACTIVE EFFECTS OF MAGNETITE, ILMENITE, AND FERROBORON | en_US |
| dc.title.alternative | OPTIMIZATION OF RADIATION SHIELDING ULTRA-HIGH-PERFORMANCE CONCRETE | en_US |
| dc.type | Thesis | en_US |
| dc.contributor.department | Civil Engineering | en_US |
| dc.description.degreetype | Thesis | en_US |
| dc.description.degree | Master of Applied Science (MASc) | en_US |
| dc.description.layabstract | Owing to its dense microstructure, exceptional mechanical properties and resistance to degradation, ultra-high-performance concrete (UHPC) has emerged as an attractive candidate for extending the service life of civil infrastructure. The current research focuses on leveraging the exceptional merits of UHPC to re-engineer a novel radiation shielding UHPC (RS-UHPC), which can eventually contribute to fostering the safety and security of nuclear containment structures. A comprehensive two-phase investigation was conducted to develop a novel RS-UHPC by leveraging the combined effect of key heavyweight aggregates, namely of magnetite, ilmenite, and ferroboron. The first phase focuses on optimizing RS-UHPC mortars through dry-wet packing approaches alongside response surface methodology to develop predictive performance models. Building upon the optimum RS-UHPC mortar, the second phase focuses on optimizing the fibre content necessary for improved mechanical and radiation shielding efficiency. As such, the current research contributes to advancing the development of innovative materials needed to foster the deployment of nuclear energy. | en_US |
| Appears in Collections: | Open Access Dissertations and Theses | |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| anunike_great_samuel_finalsubmission2025april_mastersdegreethesis.pdf | Master’s degree thesis final submission for June 17th 2025 graduation | 29.78 MB | Adobe PDF | View/Open |
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