Nuclear accidents

diagrams: Chernobyl reactor before and after

Nuclear fission is one of the world-changing discoveries of the mid-twentieth century. The atomic bomb projects of the United States led to the atomic bombing of Japan in August 1945, and the hope for limitless electricity brought about the proliferation of a variety of nuclear reactors around the world in the decades following World War II. And, of course, nuclear weapons proliferated to other countries beyond the original circle of atomic powers.

Given the enormous energies associated with fission and the dangerous and toxic properties of radioactive components of fission processes, the possibility of a nuclear accident is a particularly frightening one for the modern public. The world has seen the results of several massive nuclear accidents — Chernobyl and Fukushima in particular — and the devastating results they have had on human populations and the social and economic wellbeing of the regions in which they occurred.

Safety is therefore a paramount priority in the nuclear industry, both in research labs and military and civilian applications. So what is the situation of safety in the nuclear sector? Jim Mahaffey’s Atomic Accidents: A History of Nuclear Meltdowns and Disasters: From the Ozark Mountains to Fukushima is a detailed and carefully researched attempt to answer this question. And the information he provides is not reassuring. Beyond the celebrated and well-known disasters at nuclear power plants (Three Mile Island, Chernobyl, Fukushima), Mahaffey refers to hundreds of accidents involving reactors, research laboratories, weapons plants, and deployed nuclear weapons that have had less public awareness. These accidents resulted in a very low number of lives lost, but their frequency is alarming. They are indeed “normal accidents” (Perrow, Normal Accidents: Living with High-Risk Technologies. For example:

  • a Japanese fishing boat is contaminated by fallout from Castle Bravo test of hydrogen bomb; lots of radioactive fish at the markets in Japan (March 1, 1954) (kl 1706)
  • one MK-6 atomic bomb is dropped on Mars Bluff, South Carolina, after a crew member accidentally pulled the emergency bomb release handle (February 5, 1958) (kl 5774)
  • Fermi 1 liquid sodium plutonium breeder reactor experiences fuel meltdown during startup trials near Detroit (October 4, 1966) (kl 4127)

Mahaffey also provides detailed accounts of the most serious nuclear accidents and meltdowns during the past forty years, Three Mile Island, Chernobyl, and Fukushima.

The safety and control of nuclear weapons is of particular interest. Here is Mahaffey’s summary of “Broken Arrow” events — the loss of atomic and fusion weapons:

Did the Air Force ever lose an A-bomb, or did they just misplace a few of them for a short time? Did they ever drop anything that could be picked up by someone else and used against us? Is humanity going to perish because of poisonous plutonium spread that was snapped up by the wrong people after being somehow misplaced? Several examples will follow. You be the judge. 

Chuck Hansen [

U.S. Nuclear Weapons – The Secret History

] was wrong about one thing. He counted thirty-two “Broken Arrow” accidents. There are now sixty-five documented incidents in which nuclear weapons owned by the United States were lost, destroyed, or damaged between 1945 and 1989. These bombs and warheads, which contain hundreds of pounds of high explosive, have been abused in a wide range of unfortunate events. They have been accidentally dropped from high altitude, dropped from low altitude, crashed through the bomb bay doors while standing on the runway, tumbled off a fork lift, escaped from a chain hoist, and rolled off an aircraft carrier into the ocean. Bombs have been abandoned at the bottom of a test shaft, left buried in a crater, and lost in the mud off the coast of Georgia. Nuclear devices have been pounded with artillery of a foreign nature, struck by lightning, smashed to pieces, scorched, toasted, and burned beyond recognition. Incredibly, in all this mayhem, not a single nuclear weapon has gone off accidentally, anywhere in the world. If it had, the public would know about it. That type of accident would be almost impossible to conceal. (kl 5527)

There are a few common threads in the stories of accident and malfunction that Mahaffey provides. First, there are failures of training and knowledge on the part of front-line workers. The physics of nuclear fission are often counter-intuitive, and the idea of critical mass does not fully capture the danger of a quantity of fissionable material. The geometry of the storage of the material makes a critical difference in going critical. Fissionable material is often transported and manipulated in liquid solution; and the shape and configuration of the vessel in which the solution is held makes a difference to the probability of exponential growth of neutron emission — leading to runaway fission of the material. Mahaffey documents accidents that occurred in nuclear materials processing plants that resulted from plant workers applying what they knew from industrial plumbing to their efforts to solve basic shop-floor problems. All too often the result was a flash of blue light and the release of a great deal of heat and radioactive material.

Second, there is a fault at the opposite end of the knowledge spectrum — the tendency of expert engineers and scientists to believe that they can solve complicated reactor problems on the fly. This turned out to be a critical problem at Chernobyl (kl 6859).

The most difficult problem to handle is that the reactor operator, highly trained and educated with an active and disciplined mind, is liable to think beyond the rote procedures and carefully scheduled tasks. The operator is not a computer, and he or she cannot think like a machine. When the operator at NRX saw some untidy valve handles in the basement, he stepped outside the procedures and straightened them out, so that they were all facing the same way. (kl 2057)

There are also clear examples of inappropriate supervision in the accounts shared by Mahaffey. Here is an example from Chernobyl.

[Deputy chief engineer] Dyatlov was enraged. He paced up and down the control panel, berating the operators, cursing, spitting, threatening, and waving his arms. He demanded that the power be brought back up to 1,500 megawatts, where it was supposed to be for the test. The operators, Toptunov and Akimov, refused on grounds that it was against the rules to do so, even if they were not sure why. 

Dyatlov turned on Toptunov. “You lying idiot! If you don’t increase power, Tregub will!”  

Tregub, the Shift Foreman from the previous shift, was officially off the clock, but he had stayed around just to see the test. He tried to stay out of it. 

Toptunov, in fear of losing his job, started pulling rods. By the time he had wrestled it back to 200 megawatts, 205 of the 211 control rods were all the way out. In this unusual condition, there was danger of an emergency shutdown causing prompt supercriticality and a resulting steam explosion. At 1: 22: 30 a.m., a read-out from the operations computer advised that the reserve reactivity was too low for controlling the reactor, and it should be shut down immediately. Dyatlov was not worried. “Another two or three minutes, and it will be all over. Get moving, boys! (kl 6887)

This was the turning point in the disaster.

A related fault is the intrusion of political and business interests into the design and conduct of high-risk nuclear actions. Leaders want a given outcome without understanding the technical details of the processes they are demanding; subordinates like Toptunov are eventually cajoled or coerced into taking the problematic actions. The persistence of advocates for liquid sodium breeder reactors represents a higher-level example of the same fault. Associated with this role of political and business interests is an impulse towards secrecy and concealment when accidents occur and deliberate understatement of the public dangers created by an accident — a fault amply demonstrated in the Fukushima disaster.

Atomic Accidents provides a fascinating history of events of which most of us are unaware. The book is not primarily intended to offer an account of the causes of these accidents, but rather the ways in which they unfolded and the consequences they had for human welfare. (Generally speaking his view is that nuclear accidents in North America and Western Europe have had remarkably few human casualties.) And many of the accidents he describes are exactly the sorts of failures that are common in all largescale industrial and military processes.

(Largescale technology failure has come up frequently here. See these posts for analysis of some of the organizational causes of technology failure (link, link, link).)

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