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
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/38039 |
| Date | 01 May 1991 |
| Creators | King, John Barry |
| Contributors | Davis, Lorin R., Reyes, Jose N. Jr |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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