JULY 20, 2011 - Nuclear Power Plant Safety

 
 
Visitors
Doyle Purvis
Carol Jones

Program
Bruce Jorgensen -
Nuclear Safety
 
This presentation could have been filled with engineering jargon waaaay over our heads. Instead, we were treated to a very structured talk on nuclear safety in terms we could all understand.
 
Simply put, a nuclear reactor splits large atoms and in the process creates heat used to create electricity and smaller radioactive atoms.  Because the smaller radioactive atoms are potentially volatile they create a unique hazard. Bruce’s definition of nuclear safety is the task of keeping those smaller radioactive atoms away from people.
 
In a typical Nuclear Power Plant there are four barriers that keep the radioactive material away from people.  
 
  • The fissionable ceramic nuclear fuel itself can withstand very high temperatures and will not melt … as long as it is kept below 4500 degrees.  
     
  • Cladding, the sheath surrounding the fuel, is another barrier … as long as it is kept below 2500 degrees. Once above 2500 degrees the cladding will crack and even burn. It will burn so hot that it will take the oxygen right out of the water (H2O) leaving free hydrogen which is explosive.
     
  • The Steel Containment Vessel will not melt … if kept below 1500 degrees.
     
  • And finally the Containment Building. It must be kept below 300 degrees. 
Clearly, temperature is critical. To keep the radioactive atoms away from people, only one rule is necessary – stated as often as possible.
 
Keep them cool
Keep them cool
Keep them cool
 
But there have been nuclear incidents or accidents.  The causes can be grouped as follows.
 
  • Human Error - The Three Mile Island and Chernobyl accidents were the result of operators not understanding their systems. They took the wrong actions with catastrophic results. Highly disciplined trained operators are the key to preventing this kind of accident.
     
  • Equipment Failure – There have been thousands of incidents of equipment failure in the industry … and one never hears about them. Why? Because the design standard in the nuclear industry is to build equipment and systems with two or three totally independent and fully operational backups. Whenever a piece of equipment fails there is another immediately available to take its place.
     
  • Mother Nature - Numerous natural events have threatened nuclear power plants and none resulted in catastrophe … until Fukushima. Engineers have been successful at planning for the worst but the 40 foot tidal wave in Japan was beyond anyone’s imagination.  It was a tidal wave like no other.
     
  • Sabotage - There has not been a terrorist attack on a nuclear plant. It goes without saying that defensive measures are in place at all of the nuclear facilities in the United States.
Bruce commented on the safety systems in place at our own Palo Verde Power Plant just west of Phoenix. While there is no absolute guarantee, Palo Verde appears to score high marks in the area of nuclear safety.