Thesis (MScIng)--University of Stellenbosch, 2004. / Please refer to full text for abstract.

published_or_final_version / Radioisotope / Doctoral / Doctor of Philosophy

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / abstract / Transport Policy and Planning / Master / Master of Arts in Transport Policy and Planning

published_or_final_version / abstract / Geography / Master / Master of Philosophy

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Politics and Public Administration / Doctoral / Doctor of Philosophy

The Hazard Analysis and Critical Control Point (HACCP) system for studying the food preparation process was conducted in four households in an environmentally poor urban neighborhood of Guayaquil, Ecuador. The analysis consisted of observing all of the steps in the food preparation process, measuring food temperatures at each step, and collecting food and water samples. Food and water samples were tested for total aerobic microorganisms, molds and yeast, total coliforms, and fecal coliforms. Temperatures reached during the cooking process were high enough to kill vegetative forms of foodborne pathogens; however, heat-resistant spores could have survived. Leftover food was held at room temperature for long periods of time which allowed multiplication of vegetative forms from spores or from contaminated food utensils. Leftover food was eaten either cold or reheated to warm temperatures. Water samples were taken from water delivery trucks and from each family. Water was identified as one of the main hazards in food preparation. None of the water samples met the criteria of the Ecuadorean National Institute of Standards for human consumption. Fecal samples were taken from children in the families, and were analyzed for parasites. Parasites were found in all of the samples. After critical control points were identified, appropriate interventions were taken to improve safety at each step. Based on these HACCP observations, a food and water safety program was designed and taught to five mothers attending a Guayaquil Child Care Center. The program included a lesson on each of four topics: food and water safety, parasites, care during diarrhea with emphasis on oral rehydration therapy and the introduction of solid food, and nutrition. A control mother was identified for each group. Diarrhea occurred in children of both groups but none of the children was hospitalized. With the exception of nutrition concepts, the knowledge about food and water safety concepts, parasites and care during diarrhea were well understood by both groups. This was reflected in positive changes in families' behavior toward using improved food and water sanitation practices as observed during a visit to each family which followed the HACCP study and the educational program. / Graduation date: 1994

Pressurizer modeling for predicting the dynamic pressure of the PIUS system is presented. The transient behavior of this model for the PIUS system was investigated. The validity of this model for the PIUS system is limited to transients that are neither too large nor too long in duration. For example, the model is not capable of describing events following a complete loss of liquid for the pressurizer. However, the model can be used for qualitative prediction of the PIUS system behavior for a wide variety of severe transients. A review of pressurizer modeling indicates that the neglecting of the change in the internal energy of the subcooled water during transients is an acceptable assumption. The inherently safe feature of the PIUS system was confirmed through the self-shutdown of the reactor or, in some cases, through reactor power reduction as a result of the ingress of the pool boric acid solution into the primary system. This dynamic model was constructed of three major components: (1) The primary loop, (2) The secondary loop, and (3) The natural convection loop through the pool. A lumped parameter model, uniform heat transfer, and point kinetics have been the main approximations in this model. Other approximations are mentioned during the modeling of each component of the model. The dynamic model was simulated using the DARE-P continuous system simulation language which was developed in the Electrical Engineering Department at the University of Arizona.

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