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A system safety assurance case aims to demonstrate that a system is reasonably safe within the parameters defined according to its intended use. A system safety assurance case involves the definition of a Safety Engineering Process and its execution for the particular system. An essential element in the Safety Engineering Process is hazard analysis. An often used version of hazard analysis is HAZOP. HAZOP identifies hazards and hazardous events in the system's design. Traditionally, HAZOP is performed based on the expertise of a multi-disciplinary team. This team uses a heuristic based approach that results in documented output that often does not include adequate traceability as to how the output results were obtained. This thesis proposes a systematic approach to HAZOP that was developed after performing detailed analysis on how traditional HAZOP is performed in industry. It aims to produce documented output in which the output results are traceable to interim steps in the process. We call this systematic approach HAZOP+, because it was designed to provide sufficient detail so that it can form the basis of a HAZOP metamodel created in Workflow+ - a relatively new model driven methodology for developing assurance cases. Workflow+ has well-defined semantics, and so we refer to HAZOP+ as formalizable. HAZOP+ has a number of benefits over traditional HAZOP, and these benefits are demonstrated by comparing a traditional application of HAZOP with the application of HAZOP+, both applied to a typical Lane Keeping Assist feature. A long term objective of system safety assurance is to be able to perform incremental safety assurance, for example, by updating the system safety assurance case after a modification to the system or its environment. Since the safety assurance case for a system depends on elements of the Safety Engineering Process, as well as the outputs of that process, the ability to perform an incremental hazard analysis after a modification to the system or environment can be a real benefit. This thesis further describes how HAZOP+ can be enhanced/extended to HAZOPdelta - an incremental version of HAZOP+. / Thesis / Master of Applied Science (MASc)

Spatial disorientation is the singular most common factor in human-error aviation accidents, and over ninety percent of those accidents are fatal. Despite advances in aviation over the past one hundred years in both technology and training, spatial disorientation mishaps continue at a steady pace, even though other incidents declining in frequency. Because spatial disorientation is a highly complex phenomena that involves the vestibular system, the visual system, and cognitive factors such as workload and attention, predicting spatial disorientation is extremely difficult. Likewise, exactly replicating spatial disorientation for training purposes is challenging as well as extremely dangerous and costly. The goal of this study was twofold: to understand if innate abilities can predict propensity for spatial disorientation, and to investigate the efficacy of using story-based vignettes – narratives – to train spatial disorientation to increase schematic learning in pilots. Results demonstrated that performance on a spatial orientation task such as the Direction Orientation Task (DOT) is not a reliable predictor for spatial disorientation recognition based on self-report spatial disorientation frequency. In addition, though story-based vignettes demonstrated potential for increased cue recognition over a control training event, significant differences were not found in novel spatial disorientation recognition, critical cue identification, or confidence. These findings indicate that spatial disorientation could be a completely perceptual (bottom-up) task rather than one that is both top-down and bottom-up and implies future research into the ways we describe and measure spatial disorientation in order to understand it as well as train for it.

This study analyzed the relationship between stressful work environments, physical fitness, and employee well-being, and proposed the “survival of the fittest” model. The “survival of the fittest” model was tested to determine whether physical fitness reduced the negative health outcomes of stressful work environments. Stressful work environments were framed through the job demands-control model (Karasek, 1979), and employee well-being was assessed through cardiovascular health and psychological well-being. Physical fitness was measured as cardiorespiratory endurance. Main effect and interaction effect models were tested using hierarchical regression and nonlinear structural equation modeling (SEM) analyses techniques. This study showed that employee well-being is negatively affected by current work trends. The results indicated that the interaction effect of high strain jobs (high job demands and low job control) negatively affected cardiovascular health, but not psychological well-being. Psychological well-being was negatively affected by high job demands, and low job control independently (main effects), whereas cardiovascular health was not negatively affected by these main effects. The results also indicated that fitness, when measured as a state, did not produce the hypothesized stress reducing effects, nor the expected improvements in cardiovascular health and psychological well-being. A discussion of these results includes an analysis of group differences, an evaluation of the fitness measure, and an examination of the sample population. This dissertation contributed to the occupational health and stress literature by offering conceptual and methodological improvements over past research. Specifically, I analyzed the job demands-control model through a focused measure of job control and a descriptive measure of job demands. Psychological well-being included the emotional exhaustion measure of burnout, and a measure of anxiety and depression not previously tested in this literature stream. Objective measures of cardiovascular health (blood pressure) and physical fitness (step test) were obtained, and data were gathered from a cross-sectional sample of 100 working adults. Furthermore, the application of nonlinear SEM techniques allowed for the simultaneous examination of physiological and psychological health outcomes, which provided a holistic view of the work stress and employee well-being relationship not previously found in this literature.

The job-related fatality rate in the construction industry is high as a result of multiple factors associated with the safety of workers. However, mental fatigue, a prominent factor affecting one’s hazard perception, from engagement in construction tasks and its effects on fall hazard has not been adequately studied. This thesis proposes a two-trajectory framework to assess mental fatigue using Electroencephalography (EEG). Primarily, Wavelet Packet Decomposition (WPD) was used to obtain energy in each brain wave, and seven mental fatigue indices including θ, α, β, α/β, θ/α, θ/β, and (θ + α)/β were calculated. Secondarily, sample entropy (SampleEn) values were calculated for groups under comparison to examine the results from the WPD. Results from the adopted method suggest that typical construction activities and height exposure can cause mental fatigue and reduce vigilance level in workers. It is essential to have a quantitative approach for continuous cognitive monitoring to enhance construction safety.

Canada has participated in the Generation IV International Forum (GIF) collaboration in the area of Super Critical Water-cooled Reactors (SCWR). Similar to the current CANDU technologies, in the Canadian SCWR design the low pressure heavy water moderator system is separated from the supercritical coolant system (25MPa). The High Efficiency Re-entrant Channel (HERC) design in the Canadian SCWR has multiple coolant regions (i.e. coolant in the downward center flow tube and coolant in the upward outer fuel region) and provides thermal isolation between the moderator and heat transport system fluid. Although the overall reactivity feedback in the channel is negative for equilibrium density decrease transients, a temporary positive reactivity may be induced during non-equilibrium conditions such as cold-leg Loss of Coolant Accidents (LOCA). The primary objective of this study is to investigate the fuel and coolant behaviors under postulated LOCA transients, in particular those caused by cold-leg breaks, and to demonstrate the effectiveness of several proposed safety systems in the Canadian SCWR. The one-dimensional thermalhydraulic system code RELAP5 has been used for the safety analysis in many LWRs. The latest version RELAP5/MOD4 has been improved to accommodate supercritical water and is used in this study. A RELAP5 model is constructed based on the most recent Canadian SCWR design. The 336 fuel channels are split into two representative groups each with a series of hydraulic and heat structure models. A benchmark study is conducted by comparing RELAP5 to CATHENA simulations and shows good agreement for both steady-state and transient predictions. The RELAP5 model is then used to predict the system response to several postulated LOCA transients. For a 100% (single-ended) cold-leg break located in between the feedwater pump and the inlet plenum, the system pressure immediately drops followed closely by a flow reversal with rapid discharge from the break. A brief power pulse (178%FP) is observed under this non-equilibrium depressurization scenario. The transient simulations show the potential for two sheath temperature maxima, one early in the transient as a result of the power pulse and the subsequent flow-power mismatch, and another later peak resulting from the fuel heat-up under near stagnant channel flow conditions (such as in the failure of the Emergency Core Cooling Systems) as the heat transfer regime changes to radiation dominated. The Automatic Depressurization System (ADS) located on the hot-leg side mitigates the later fuel heat-up by introducing forward channel flows. This effect is enhanced by additional coolant supplied from Low Pressure Coolant Injection (LPCI) which is part of the Emergency Core Cooling System (ECCS). Under the 100% break LOCA/LOECC transient, the core inventory is depleted rapidly after the break and thermal radiation becomes the dominant heat removal mechanism. The highest MCST, 1331 K, is achieved approximately 136s after the break and meets the safety criterion (1533 K). Beyond this time the sheath temperatures gradually decrease either by the continuous LPCI from the reactor sumps, gravity driven core cooling, or in the event of a failure of those systems by the Passive Moderator Cooling System (PMCS). LOCAs initiated by break sizes varying from 5% to 100% of the cold-leg cross-section area are simulated under loss of ECCS. In this specific design, break sizes less than 15% are defined as SBLOCAs and show an early pressure increase up to the Safety Relief Valve (SRV) setpoint. During SBLOCAs, the first MCST peak is more limiting than the large LOCA case because of insufficient fuel cooling caused by relatively low reverse flow. However, these lower reverse flows prolong the period of blowdown cooling and hence help to mitigate the secondary MCST peak. The worst LOCA case occurs in the 15% break case with a maximum cladding temperature of 1450 K. The results showed the most sensitive parameters are delays associated with SDS action, emissivity and ADS actuation parameters. / Thesis / Master of Applied Science (MASc)

Florida is one of two states that do not allow ARNPs to prescribe controlled substances. The Florida Legislature has expressed concern regarding the safety of ARNPs prescribing controlled substances. The purpose of this study was to compare malpractice rates of ARNPs and physicians in states with and without controlled substance prescribing. The design was a direct comparison of malpractice rates in states with and without ARNP controlled substance prescriptive authority. Comparison of malpractice claims was made between physicians (MDs and DOs collectively) and ARNPs in the United States and by state ARNP prescribing authority. Comparison of malpractice claims was also made between Florida and states that were demographically similar. The results showed that ARNPs have significantly less malpractice than physicians in the United States. In addition, there were no significant differences in malpractice, whether or not the ARNP was allowed to prescribe controlled substances. Finally, ARNPs working in states that are demographically similar to Florida, but allowed to prescribe controlled substances had no significant increase in malpractice. This study showed that there is no increase in malpractice rates in states where ARNPs prescribe controlled substances, either fully or partially, supporting the hypothesis.

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