Plant Meltdowns

Three Mile Island, Chernobyl, and Fukushima
Three Mile Island

All three of these disasters were due to human error. For Three Mile Island (TMI) it started with the reactor automatically shutting down because controls to the feed water pumps were accidentally damaged during a polisher cleaning 11 hours earlier. If the reactor controls detect a malfunction like this, the reactor control systems can safely shut down a reactor without human help. However, maintenance personnel had shut all the valves to the shutdown cooling pumps. Something that was never to be done with the reactor powered up. This caused an immediate over heating of the reactor triggering an emergency pressure valve to open to let steam out. The operators manually started pumping cooling water into the reactor. A control panel indicator showed that the valve had closed and the operators assumed the reactor was now safely cooling. However, the valve was stuck open, which let the cooling water drain out as fast as it was pumped in. The valve had failed previously during testing, but was never fixed. The less experienced night operators thought they were keeping to reactor’s core cool, but they were wrong. It was not until the day shift arrived, that the senior operators noticed the elevated temperature of the emergency valve outlet pipe which indicated that the valve was still open. By then the reactor’s core had melted. This series of three human mistakes cost the plant’s owner hundreds of millions and brought America’s nuclear industry to a halt. The damage to the public was a tiny exposure to radiation. An amount less than one would get living downwind from a coal-powered plant.

Here are six links to diverse sources for additional information on the Three Mile Island Meltdown. The first is a 1999 special report in the Washington Post, Crisis at Three Mile Island and Wikipedia’s entry, Three Mile Island Accident. Both of these pieces include details of the human failures noted above. In contrast, the sources listed below gloss over the details of the initial missteps that started the reactor meltdown.

From the United States Nuclear Regulatory Commission (U.S.NRC), A Backgrounder on Three Mile Island, from the World Nuclear Association, Three Mile Island Accident, from the Smithsonian, Three Mile Island: The Inside Story, and from Dickinson College, a nationally recognized and highly selective liberal arts college located in Carlisle, Pennsylvania who built a website dedicated to the Three Mile Island Accident.

 
Chernobyl

Chernobyl was a completely different situation although its cause was also rooted in human failure. Management wanted to test a new emergency shutdown procedure but they were behind schedule and the test ended up being performed by less experienced night operators (they get blamed for everything). Something went wrong causing the reactor to grossly overheat and catch fire. Unlike Three Mile Island, Chernobyl’s reactor was moderated with combustible graphite instead of water and there was no containment building. In a few seconds, the reactor heated to the point that the graphite started to burn. The reactor building soon collapsed and highly radioactive ash from the burning graphite and highly radioactive fuel was free to engulf the region.

If there was anything to be learned from Chernobyl, it was that America should have maintained a vibrant nuclear power industry which could have helped other countries replace their old and dangerous reactors with new safer designs.

For a more detailed analysis read Backgrounder on Chernobyl Nuclear Power Plant Accident from the United States Nuclear Regulatory Commission (U.S.NRC), and the World Nuclear Association’s report, Chernobyl Accident, which includes after effect information updated to December 2012.

There is a newly released pro nuclear move, Pandora’s Promise. It documents the recent conversion of several anti-nuclear environmentalists into believers that nuclear power is safe and clean. It documents France’s popular nuclear program and even travels into the Chernobyl Exclusion Zone and talks to the people resettling there. Click the link above for more information and to view the movie’s trailer.

Lastly, we need to resist the inflammatory rhetoric that compares Chernobyl with Hiroshima and Nagasaki. Only 49 workers died because of Chernobyl. Most were brave first responders who gave their lives to put out the burning reactor and cover its remains. Yes, large areas were contaminated but people are returning as radiation levels fall. Yes, many people received excessive doses of radiation. These people are being monitored. Some effects linger, but deaths attributable to the exposure seem few if any. The World Nuclear Association’s, Chernobyl Accident  report details these facts.

Burke has never figured out why so many people have such a strong fear of Nuclear Power, which has only killed 49 people in over 55 years. while the fossil fuel industry kills hundreds each year. For example, this July 19, 2013, 47 innocent people were incinerated in the tanker train accident in Lac-Méganatic, Quebec. This is only two less that the world wide total of 49 deaths from Chernobyl. Wikipedia on the Lac-Méganatic derailment.

 
Fukushima Dai-ichi

Since Chernobyl, nuclear proponent touted the fact that a Chernobyl like incident could not happen with a modern reactor since they were water moderated and enclosed in a strong containment structure. They forgot Murphy’s Law, “Anything that can go wrong, will!”

Failure analysis is based on assumptions. Fukushima was designed to survive a once in a hundred-year tsunami not a once in a thousand-year one. Translated into probability, the chance of the hundred-year tsunami happening sometime next year is one in a hundred. For the thousand-year tsunami, it is one in a thousand. However, in the real world either could happen tomorrow. The only difference is that the larger tsunami is 10 times less likely to happen tomorrow. You must design for the worst case like the million-year tsunami and add an additional safety factor on top of that.

Nuclear power plants are often located near a large body of water to condense the spent steam back into water. Using an ocean or a river is cheaper than building large cooling towers. Since they were in a known Tsunami Zone these reactors should have been designed to operate under water (think Nuclear Submarine) or located way up a hill, or even underground. Reactors 5 and 6 at Fukushima were offline but still in need of cooling when the tsunami hit. Luckily, a government mandated third backup generator had to be located up a nearby hill as its air-cooling fins made it too large to fit inside with the other backup generators. Water from the Tsunami splashed up against its sides but it was able to start and power plants 5 and 6 to a safe cold shutdown.

Our first link is to Kenichi Ohmae’s April 2012 Special Report to the Japan Times.  It is the best independent analysis of the Fukushima meltdowns we have read. Ohmae, a nuclear core designer who earned his Ph.D. in nuclear engineering from the Massachusetts Institute of Technology, spent three months investigating the disaster. His full report includes four hours of YouTube videos (with english subtitles), and an untallied number of pages.

Another excellent analyses of the Fukushima reactor meltdowns is an official report prepared for the Japanese This 291 page has been translated into English. Beware, this 291 page pdf file seems slow to download. What should we learn from Fukushima Daiichi accident – Team H2O 21.12.2011.

In July, 2012, the Sandia National Laboratories published the Fukushima Daiichi Accident Study report for U.S. Nuclear Regulatory Commission (NRC) and Department of Energy. It is a 298 page pdf but it loads quickly,
We have included these extensive documents not so much for your reading (you are welcome to) but to imprint you with the concept that nuclear power is just not a simple issue of good versus evil but a serious and complex issue that power professionals take very seriously. If something does go wrong, they perform a very detailed analysis of what went wrong so changes can be made to prevent a reoccurrence.