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The radiological hazards from tritium are usually associated with exposure to tritium oxide either by inhalation, ingestion or permeation through skin. However, exposure from skin-contact with tritium gas contaminated surfaces represents a different radiological hazard in tritium removal facilities and future fusion power plants. Previous experiments on humans by Eakins et al. (8), and more recent experiments on hairless rats at Chalk River Laboratories have shown that when a tritium gas-contaminated surface is brought into contact with intact skin, high concentrations of organically-bound tritium in urine and skin are observed which were not seen from single tritiated water (liquid or vapour form) contamination. The results of the rat experiments, which involved measurements of tritium activity in urine and skin, after contact with contaminated stainless steel, are described. These results are also compared to previous data from human experiments. The effect of various exposure conditions and different contaminated surfaces such as brass, aluminum and glass are analysed and related to the results from contaminated stainless steel exposure. Dosimetric models are being developed in order to improve the basis for dose assessment for this mode of tritium uptake. The presently studied model is explained along with the assumptions and methods involved in its derivation. The features of 'STELLA', the software program used to implement the model, are discussed. The methods used to estimate skin and whole body dose from a model are demonstrated. Finally, some experiments for improving the accuracy of the model are proposed. Briefly, this study compares the results from animal and human experiments as well as different exposure conditions, and determine the range of whole body and skin dose that may be involved from skin-contact intake. This information is essential for regulatory purposes particularly in the derivation of doses for skin-contact contamination. / Thesis / Master of Science (MS)

Structural applications, including aircraft, ships, and offshore oil drilling platforms, have witnessed a surge in composite material usage. However, exposure to elevated temperatures poses a significant risk to these materials, especially in scenarios such as fires and high-temperature exhaust gas impingement. Despite limited or no visible damage, composite properties can undergo significant degradation, leading to potential in-service failures and jeopardizing operational safety and integrity. It was previously determined that the accuracy of the equipment and methodology used for measuring elevated temperature thermal properties, particularly in predicting composite material thermal properties could not meet the necessary precision. Using an inverse analysis technique to solve for the thermal conductivity and specific heat capacity, the thermal properties of composite materials can be determined. These thermal properties can then be used in a rapid heat damage assessment and failure prediction tool that can be updated based on additional data provided during inspection which takes into account material state changes and damage development due to the elevated temperature exposure and provides a way to incorporate those changes into subsequent structural analyses. / Master of Science / Composite materials are great for structural usage in a wide variety of endeavors. The problem with them is that when exposed to high temperatures, the composite materials properties can change. This can cause failures from seemingly good material which can cause serious bodily harm or even death. My research aims to help bolster the safety and integrity of composite material structures by providing a reliable way to determine their thermal properties. With the thermal properties known, development of a tool that can predict composite material failures which can take into account changes in the material due to thermal damage.

As the existing steel infrastructure inevitably continues to age and deteriorate, engineers are increasingly looking for innovative and effective methods for repairing and maintaining existing structures. Structural steel components can degrade due to the surrounding environmental conditions, and are susceptible to corrosion damage when exposed to aggressive environments and deicing salts. The conventional methods for repairing steel structures can be labor-intensive and time-consuming, and add considerable weight to the existing structure. One alternative is utilizing carbon fiber reinforced polymers (CFRP). Many studies have documented the ability of CFRPs to enhance the strength of existing structures. Furthermore, CFRP offers the benefits of being non-corrosive and having a high strength-to-weight ratio. Most studies on steel strengthening have focused on the bond behavior of CFRP to steels having a smooth surface condition, which are not representative of deteriorated structures in greater need of retrofitting. Further research has examined the durability of CFRP-steel bonds relative to environmental conditions that do not reflect the service life conditions for typical applications. In this work, a comprehensive study is conducted on the effects of the surface condition and environmental exposure on the bond between CFRP and steel. The influence of corrosion and simulated corrosion pitting is evaluated to determine whether structures with non-uniform surfaces are adequate for CFRP retrofits. In addition, the durability of CFRP-steel bonded systems is investigated through laboratory hygrothermal aging and in-situ environmental conditioning to multiple environments in Virginia. The research can be useful in the development of guidelines that will assist engineers determine if a CFRP retrofit solution is applicable in a given environmental setting and appropriate for the level of deterioration of the structure. / Doctor of Philosophy / As steel structures continue to age, engineers are looking for innovative and effective methods for repairing and maintaining the existing steel infrastructure. Steel components in structures can degrade due to the surrounding environmental conditions. The conventional methods for repairing steel structures can be labor-intensive and time-consuming, and add considerable weight to the existing structure. One alternative is utilizing carbon fiber reinforced polymers (CFRP). The ability of CFRPs to enhance the strength of existing structures has been widely documented. Furthermore, CFRP offers the benefits of being non-corrosive and avoids adding considerable weight to the structure. Most studies on steel strengthening have focused on the bond behavior of CFRP to steels having a smooth surface condition, which are not representative of deteriorated structures in greater need of retrofitting. Further research has examined the durability of CFRP-steel bonds relative to environmental conditions that do not reflect the service life conditions for typical applications. In this work, a comprehensive study is conducted on the effects of the surface condition and environmental exposure on the bond between CFRP and steel. The influence of corrosion and simulated corrosion pitting is evaluated to determine whether structures with non-uniform surfaces are adequate for CFRP retrofits. In addition, the durability of CFRP-steel bonds exposed to laboratory and field conditions is investigated. The research can be useful in the development of guidelines that will assist engineers determine if the application of CFRPs retrofit solution is suitable in a given environment and appropriate for the level of deterioration of the structure.