On March 20, 1978, a power supply failure for the plant's non-nuclear instrumentation system led to steam generator dryout (ref NRC LER 312/78-001). This triggered an automatic reactor shutdown. In a 2005 document, the United States Nuclear Regulatory Commission indicated that it was the third most serious safety-related occurrence in the United States to date (behind the Three Mile Island accident and the Browns Ferry cable tray fire). The U.S. Nuclear Regulatory Commission (NRC) staff concluded that fundamental design flaws which were known by plant operators and the NRC itself were at the heart of the problem and should have been fixed years before. “In summary, the information was available and known which could have prevented this overcooling transient; but in the absence of adequate plant modifications, the incident should have been expected,” the staff wrote.