<p>In the next few decades, the nuclear industry worldwide is expected to launch a set of reactors with advanced reactor designs. Generation-IV (GEN-IV) reactors are to display superior safety by incorporating additional passive safety concepts as well as improving accident management and minimization of consequences. Canada is in the early stages of conceiving its GEN-IV reactor design – the Supercritical Water Reactor (SCWR). The proposed design is based on the existing CANDU configurations and is expected to offer significant advances in thermal efficiency, fuel cycle sustainability, and relative cost of energy. Of particular interest is the reactor's ability to use inherent or passive safety concepts which will translate to the reactor being walk-away safe in an accident.</p> <p>Steam generators in CANDU remove decay heat by thermosyphoning in a loss of Class-IV power accident. This natural circulation process was a passive feature in GEN-II and GEN-III CANDUs. The SCWR's direct thermodynamic cycle implies steam generators are no longer incorporated into the design. This thesis examines how the SCWR compensates for the removal of a passive safety system element and the difference to the overall safety of the reactor following accidents. These results will be compared to the traditional CANDU's response in accidents to demonstrate the added value of this new reactor in maintaining the goal of no widespread core damage. Comparisons were also made between the SCWR and similar GEN-IV reactors in terms of design and response to various initiating events.</p> <p>Probabilistic Risk Analysis is used in this thesis to assess the SCWR design options. Although the SCWR is in the pre-conceptual design phase, the results of such risk assessment studies could affect the design, operation, and licensing of this new reactor. Future studies can build on this work to conduct more detailed analyses to characterise the SCWR's safety and reliability.</p> / Master of Applied Science (MASc)

Tunnelling in urban areas is one of the most challenging engineering activities, as it has relatively high “risk” due to various uncertainties and the intensity of the possible consequences. Numerous studies have been conducted to address the tunnelling risk, by mainly focusing on the “identification” of the causes and how to control or mitigate the risks. However, limited work has been done on how to quantify the risk by considering the multi-level uncertainties encountered in different phases of the project. The primary objective of this work is to develop a multi-scale risk management (RM) framework to address and quantify the risk of ground surface settlement, induced by tunnelling, in soft clay in urbanized areas. The specific focus is placed on quantifying the risk of tunnel-induced settlement for existing buildings, by taking into account multiple uncertainty levels (e.g. uncertainties of parameters, uncertainties of models, etc.). The framework addresses the tunnel-induced settlement risk, both during the construction of the tunnel as well as after its completion, for buildings with shallow and deep foundations. It offers different classes of assessment to quantify the risk, according to the structure’s current condition and the corresponding limit-state function, that is designated to each class. The RM framework is aligned with ISO 31000 risk management act, consisting of “risk identification”, “risk analysis” and “risk evaluation”. Risk identification includes studies on tunnelling technical reports, field observations, etc., in order to identify the causes of short-term and long-term tunnelling-induced settlement. The risk analysis involves a series of fault tree, event tree and consequence tree analyses to estimate the likelihood of the ground subsidence and subsequent events. For risk evaluation, different probabilistic methods (e.g. first-order reliability method, second-order reliability method and Monte Carlo sampling) are utilized to estimate the risk of surface buildings with shallow and deep foundations. The framework has been implemented in an example problem, to demonstrate the procedure and to address the main influential parameters in each class of assessment using the alpha importance measure. Rt risk tool has been utilized to perform reliability calculations and FORM has been used as the primary method due to its valuable balance between computational cost and accuracy. The outcomes of this RM framework are risk registers and colour-coded risk maps including the exceedance probability of a predefined settlement threshold for each building in the affected area. This framework receives technical data and provides risk-based information for higher-level managers and decision-makers to prioritize their actions and allocate their resources in the most effective way. / Thesis / Master of Applied Science (MASc) / The aim of this study is to provide a multi-level risk management (RM) framework to address and quantify the risk of surface building settlement induced by tunnelling in soft clay in urbanized areas. The focused is placed on quantifying the risk of tunnel-induced settlement of existing buildings, by taking into account multiple uncertainty levels. The framework addresses the tunnel-induced settlement risk, both during the construction of the tunnel as well as after its completion, for buildings with shallow and deep foundations. It offers different classes of assessment to quantify the risk, according to the structure’s current condition and with respect to specific limit-state functions designated for each class. The proposed framework was implemented in an example to demonstrate the procedure and outcomes.