Atomic Accidents

Reading Atomic Accidents, by Jim Mahaffey, in my home office.

The Oakland University library has online access to the book Atomic Accidents: A History of Nuclear Meltdowns and Disasters, From the Ozark Mountains to Fukushima, by Jim Mahaffey. I’m glad they do; with the library still locked up because of the coronavirus pandemic, I wouldn’t have been able to check out a paper copy. The book is more about nuclear engineering than nuclear medicine, but the two fields intersect during nuclear accidents, so it’s relevant to readers of Intermediate Physics for Medicine and Biology.

In his introduction, Mahaffey compares the 20th century invention of nuclear power to the 19th century development of steam-powered trains. Then he writes

In this book we will delve into the history of engineering failures, the problems of pushing into the unknown, and bad luck in nuclear research, weapons, and the power industry. When you see it all in one place, neatly arranged, patterns seem to appear. The hidden, underlying problems may come into focus. Have we been concentrating all effort in the wrong place? Can nuclear power be saved from itself, or will there always be another problem to be solved? Will nuclear fission and its long-term waste destroy civilization, or will it make civilization possible?

Some of these disasters you have heard about over and over. Some you have never heard of. In all of them, there are lessons to be learned, and sometimes the lessons require multiple examples before the reality sinks in. In my quest to examine these incidents, I was dismayed to find that what I thought I knew, what I had learned in the classroom, read in textbooks, and heard from survivors could be inaccurate. A certain mythology had taken over in both the public and the professional perceptions of what really happened. To set the record straight, or at least straighter than it was, I had to find and study buried and forgotten original reports and first-hand accounts. With declassification at the federal level, ever-increasing digitization of old documents, and improvements in archiving and searching, it is now easier to see what really happened.

So here, Gentle Reader, is your book of train wrecks, disguised as something in keeping with our 21st century anxieties. In this age, in which we strive for better sources of electrical and motive energy, there exists a deep fear of nuclear power, which makes accounts of its worst moments of destruction that much more important. The purpose of this book is not to convince you that nuclear power is unsafe beyond reason, or that it will lead to the destruction of civilization. On the contrary, I hope to demonstrate that nuclear power is even safer than transportation by steam and may be one of the key things that will allow life on Earth to keep progressing; but please form your own conclusions. The purpose is to make you aware of the myriad ways that mankind can screw up a fine idea while trying to implement it. Don’t be alarmed. This is the raw, sometimes disturbing side of engineering, about which much of humanity has been kept unaware. You cannot be harmed by just reading about it.

That story of the latest nuclear catastrophe, the destruction of the Fukushima Daiichi plant in Japan, will be held until near the end. We are going to start slowly, with the first known incident of radiation poisoning. It happened before the discovery of radiation, before the term was coined, back when we were blissfully ignorant of the invisible forces of the atomic nucleus.

I’ll share just one accident that highlights some of the issues with reactor safety discussed by Mahaffey. It took place at the Chalk River reactor in Ontario, Canada, about 300 miles northeast of Oakland University, as the crow flies.

I found several parallels between the Chalk River and Chernobyl accidents (readers might want to review my earlier post about Chernobyl before reading on). Both hinged on the design of the reactor, and in particular on the type of moderator used to slow neutrons. Both highlight how human error can overcome the most careful of safety designs. Their main difference is that Chalk River was a minor incident while Chernobyl was a catastrophe.

The Chalk River reactor began as a Canadian-British effort during World War II that operated in parallel to America’s Manhattan Project. It’s development has more in common with the plutonium-producing Hanford Site in Washington state than with the bomb-building laboratory in Los Alamos. After Enrico Fermi and his team built the first nuclear reactor in Chicago using graphite as the moderator, the Canadian-British team decided to explore moderation by heavy water. In 1944 they began to build a low-power experimental reactor along the Chalk River. For safety, the reactor has a scram consisting of heavy cadmium plates that would absorb neutrons and would lower into the reactor if a detector recorded too high of a neutron flux, shutting down nuclear fission. The energy production was controlled by raising and lowering the level of heavy water, which could be pumped into the reactor by pushing a switch. As a safety precaution, the pump would turn off after 10 seconds unless the switch was pushed again. To power up the reactor, the operator had to push the switch over and over.

In the summer of 1950 an accident occurred. Two physicists were going to test a new fuel rod design, so the reactor was shut down. The operator knew he would have to push the heavy water button many times to restart the reactor, so he began early, before the physicists were done installing the rod. Growing tired of repeatedly pushing the button, he shoved a wood chip into the switch so it was stuck on. Then the phone rang, and he was distracted by the call. The reactor went supercritical and the two physicists were doused with gamma radiation until the cadmium plates descended. Fortunately, the plates shut down the reactor before too much damage was done, and the physicists survived. Yet, the accident provides many lessons, including how human error can cause the best laid plans to go awry.

Later, a much larger reactor was built at Chalk River, and Mahaffey tells more horror stories about subsequent accidents, including one that required months of cleanup that was led in part by future President Jimmy Carter.

This story is a sample of what you’ll find in Atomic Accidents. Mahaffey describes all sorts of mishaps, from a sodium-cooled plutonium breeder reactor that in the 1960s that almost lost Detroit (Yikes, that’s just down the road from where I sit writing this post), to a variety of incidents in which an atomic bomb (usually not armed) was damaged or lost, to the frightening Kyshtym disaster in 1957 at the Mayak plutonium production site in Russia. He ends the book by describing the better-known accidents at Three-Mile Island, Chernobyl, and Fukushima.

I didn’t realize how all-or-nothing an atomic reactor is. The nuclear fuel is below a critical mass and inert until it reaches a threshold of criticality, at which point it promptly releases a burst of energy and neutrons. Usually it doesn’t blow up like a bomb, because it typically melts before the chain reaction can reach truly explosive proportions. Mahaffey has all sorts of terrifying tales. One begins with a fissile material such as uranium-235 or plutonium-239 dissolved in water; A technician pores the water from one container to another with a more spherical shape, resulting in a flash of neutrons and gamma rays that deliver a lethal dose of radiation.

After scaring us all to death, Mahaffey ends on an upbeat note.

The dangers of continuing to expand nuclear power will always be there, and there could be another unexpected reactor meltdown tomorrow, but the spectacular events that make a compelling narrative may be behind us now. We have learned from each incident. As long as nuclear engineering can strive for new innovations and learn from its history of accidents and mistakes, the benefits that nuclear power can yield for our economy, society, and yes, environment will come.

Atomic Accidents reminded me of Henry Petroski’s wonderful To Engineer is Human: The Role of Failure in Successful Design. The thesis of both books is that you can learn more by examining how things fail than how things succeed. If you want to understand nuclear engineering, the best way is to study atomic accidents.

Originally published at




Professor of Physics at Oakland University and coauthor of the textbook Intermediate Physics for Medicine and Biology.

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Brad Roth

Brad Roth

Professor of Physics at Oakland University and coauthor of the textbook Intermediate Physics for Medicine and Biology.

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