Known Problems
Duane Arnold's primary containment shell was undersized in the original design.. The "torus direct vent bypass system" retrofit was installed in all 18 Mark I reactors in the late 1980s and is operated by a butterfly valve at the operators' control, after a zero leakage rupture diaphragm breaks prior to reaching the primary containment max design pressure. Operators now have the controls necessary to protect against a rupture of primary containment, however remote..
The reactor has been shut down in unplanned scrams eleven times since the year 2000, as indicated in NRC performance indicator reports.
Read more about this topic: Duane Arnold Energy Center
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