Here is an interesting discussion of where we stand in the United States regarding severe incidents at nuclear plants.
Note, in the image the vent piping, #2, which allows depressurization of the primary containment. This post Three Mile Island, lessons learned modification was apparently not incorporated at these Japanese plants.
Note also, in the upper right hand corner of the image, a pictorial of a ventilation system in the secondary containment which exhausts through charcoal and other filters to the atmosphere. Unfortunately, this equipment is usually not hardened for severe events, nor supplied with emergency electric power.
If either of these two systems had been operable at Fukashima, destruction of the secondary buildings by hydrogen explosions, may have been averted.
U.S. Nuclear Power Plants Reconfirming Safety, Response Programs in Light of Japan Situation
U.S. Nuclear Plants Withstand Severe Events
Recent experience with earthquakes in California, Hurricane Andrew in Florida and Katrina in New Orleans repeatedly demonstrate that U.S. nuclear plants can withstand severe natural events. In each case, safety systems functioned as designed, operators responded effectively and emergency training proved successful.
When Hurricane Katrina struck New Orleans and the Gulf Coast, the devastation overwhelmed the resources of local, state and federal authorities. Katrina resulted in 1,800 deaths, damage exceeding $100 billion and millions without electric power. Entergy’s Waterford 3 nuclear energy station was in the path of the hurricane and lost offsite power, but the plant’s backup diesel generators started immediately and powered vital reactor systems for nearly five days until offsite power was restored.
The plant lost offsite communications except for satellite phones, the company’s corporate headquarters in New Orleans was evacuated and employee homes were destroyed. Yet Waterford 3 was restarted after a detailed check of plant systems, and the electricity produced there was vital to the area’s restoration. The company said information shared by the nuclear industry helped Waterford 3 prepare for the storm.
