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Call number: LD2668 .T4 1964 N74 / Master of Science

Call number: LD2668 .T4 1964 P83 / Master of Science

LD2668 .T4 1966 B415 / Master of Science

In the event of a small break loss of coolant accident (SBLOCA) in a nuclear reactor, cold fluid is injected through the reactor system high pressure injector to compensate for the coolant loss. When this flow rate is less than a critical value, however, the hot fluid in the cold leg penetrates into the vertical injection line in a process called buoyant backflow. Because the resulting penetrations induce thermal stresses in the pipe, the presence of backflow in the injection lines is potentially significant. Since these penetrations could potentially damage the pipe, it was the purpose of this study to evaluate the backflow behavior. To this end, both the critical injection conditions and the subcritical penetration depth were experimentally determined through flow simulation in a 1/5 scale model. In addition, the experimental trends wi-re modeled theoretically. By matching the theoretical results to the experimental data, it was determined that backflow began below a critical Froude number of .65 and increased in depth with the negative logarithm of the injection velocity. The agreement between theory and experiment was excellent. For a certain class of reactor systems, the full scale Froude numbers were then compared to the critical value obtained in the analysis. For the systems involved in this comparison, the full scale Froude numbers were shown to be less than .65 for all practical flow rates. As a consequence, buoyant backflow is expected within the injection lines of these reactors, under safety injection conditions. / Graduation date: 1991

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