Master of Science

Two groups of parents from different socio-economic levels were questioned about the behavioral characteristics of their children before 18 months and subsequent incidences of accidental poisoning. The data collected showed proportional numbers of accidental poisonings regardless of parent education, race or income. Unusual activity in the child before 18 months was the best predictor of accidental poisoning during childhood.

Bridges are critical pieces of infrastructure important to public safety and welfare. Fires have the potential to damage bridges and have been responsible for taking many bridges out of service. The hazard fire poses to bridges is a little studied risk unlike more common threats such as impact, scour and earthquake. Information on the rate of occurrence of bridge fires and the mechanisms of structural response of bridges subjected to fire are both vital to policy makers seeking to address the hazard rationally. The investigation presented developed frequency statistics of bridge fire incidents from several sources of vehicle accident and fire statistics. To further investigate the fire hazard a computational model integrating the simulation of large fires and the simulation of bridge superstructure mechanical response was created. The simulation was used to perform a parametric study of fire size and location to investigate the relationship between these parameters and damage tot bridge super-""structure. The statistics investigation resulted in an observed rate of fires due to vehicle accidents of approximately 175 per year. Approximately one of these per year was the result of a tanker truck carrying a flammable liquid leading to extensive superstructure damage. The simulation showed that a tanker fire resulted in permanent damage to the bridge by several measures where as the affects of a bus fire were minimal. The simulations also demonstrated the mechanisms of bridge response; the importance of girder temperature in that response; and the differences in the response to a tanker fire that can lead to collapse. / Ph. D.

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Thesis (Ph.D.)--Boston University / This dissertation probes critical questions about the relationship between the production of cultural meanings, social power, and material objects. By using the public discourse on traffic accidents in the United States as a historical case study, this study investigates in particular the various ways by which social groups respond to unintended technological consequences and dangers within definitional processes of collectively constructing a social problem. The textual-thematic analysis draws largely upon theories from social problems literature and science & technology studies, as it looks at a number of salient historical claimsmakers, sites of discourse production, and cultural vehicles of meaning making. Specifically, the contributions of the private insurance industry, safety establishment, consumer market, automobile clubs, and printed media are closely dissected to flesh out the contours and content of the accident problem's construction and development through time. In line with a contextual constructivist approach to social problems analysis, the research has observed the emergence, evolution, and eventual waning of the accident issue along several structural anchors that provide possible explanations for some of these dynamics. To a great extent, the traffic accident problem has gradually 'disappeared' in America throughout the twentieth century - a disappearance that is not physical but conceptual. Specifically, it means that the troubling social condition is defined as something to live with, a necessary evil of which there seems to be limited ability or desire to substantially affect or eradicate. The sociological concept I employ to name this particular trajectory towards problem attenuation is normalization. Applied to the case analyzed here, the findings offer a way to understand the processes by which traffic accidents become nom1alized in America as an acquiescent price to pay for the benefits of the automobile. Theoretically, these conclusions have laid the groundwork for producing a hypothetical model of social problems normalization. The model highlights the role played by several cultural devices of claimsmaking in affecting issue attenuation or 'disappearance.' When the problem is constructed through highly technicizing, commensurating, commodifying, and socially controlling modalities of sense making, the likelihood of its normalization and eventual floundering increases.

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Since the Fukushima Daiichi nuclear accident, there have been ongoing efforts to enhance the modelling capabilities for severe accidents in nuclear power plants. The primary severe accident analysis code used in Canada for its CANDU reactors is MAAP-CANDU (adapted from MAAP-LWR). In order to meet the new requirements that have evolved since Fukushima, upgrades to MAAP-CANDU have been made most recently by the Canadian nuclear industry. While the newest version (i.e. MAAP5-CANDU) offers several important improvements primarily in core nodalization and core collapse modelling, it still lacks mechanistic models for many key thermo-mechanical deformation phenomena that may significantly impact accident progression and event timings. It is also a general consensus that having alternative analysis tools is beneficial in improving our confidence in the simulation results, especially given the complex nature of severe accident phenomena in CANDU and the limited experimental support. This thesis seeks a novel approach to CANDU severe accident modelling by combining the best-estimate thermal-hydraulic code RELAP5, the severe accident models in SCDAP, and several CANDU-specific mechanistic deformation models developed by the author. This work mainly consists of two parts. The first part is focused on the assessment of natural circulation heat sinks following crash-cooldown in the early-phase of a Station Blackout (SBO) accident where fuel channel deformation can be precluded. The effectiveness of steam generator heat removal after crash-cooldown and that of the several water make-up options were demonstrated through the simulation of several SBO scenarios with/without crash-cooldown, sensitivity studies, as well as benchmarking against station and experimental measurements. In the second part, several mechanistic severe accident models were developed to enhance the simulation fidelity beyond the initial steam generator heat sink phase to the moderator boil-off and core disassembly phases. This includes models for predicting the pressure tube ballooning and sagging phenomena during the fuel channel heat-up phase and models for the sagging and disassembly of fuel channel assemblies during the core disassembly phase. After benchmarking against relevant channel deformation experiments, the models were successfully integrated into the RELAP/SCDAPSIM/MOD3.6 code as part of the SCDAP subroutines. The advantage of utilizing a code such as SCDAP is that generic models for fission product release and hydrogen generations, which are well benchmarked, can be directly applied to CANDU simulations. With the modified MOD3.6 code the early-phase SBO simulations were extended to include the later stages of SBO until the calandria vessel dryout. The current modelling approach replaced the simple threshold-type models commonly seen in the integrated severe accident codes such as MAAP-CANDU with more mechanistic models thereby providing a more robust treatment of the core degradation process during severe accident in CANDU. / Thesis / Doctor of Philosophy (PhD)