|Fig. 1: Warning sign at the entrance to the Chernobyl zone. (Source: Wikimedia Commons)|
Chernobyl (Fig. 1) and Three Mile Island are two notorious nuclear incidents connected to human error. Environmentalist groups like Greenpeace, who lobby aggressively against nuclear power of any kind, use these accidents and others as ammunition against scientists and policy makers attempting to expand nuclear capacity. Public opinion also shifts dramatically against nuclear energy in the wake of any large-scale and well-publicized accident. Chernobyl continues to dominate any policy debate on nuclear energy. But what if these nuclear accidents can be prevented with simple and easily implemented policies which would improve the performance of employees and substantially decrease the probability of error?
Sleep deprivation has been shown to adversely impact a wide range of physiological and cognitive functions. A sleep-restricted state can lead to fatigue, clumsiness, weight fluctuations, diabetes, increased risk of heart disease, and slower reaction times. Most germane to this report, sleep deprivation substantially impacts capacity to deal with complex and stressful tasks. A study used fMRI technology to monitor brain activity of sleep- deprived subjects performing verbal learning tasks; the study showed that regions of the brain's prefrontal cortex, an area that supports mental faculties such a s working memory and logical reasoning, had to work harder in sleep- deprived subjects than that of a non-sleep-deprived individual.  A wide range of studies, as well as anecdotal evidence, support the view that sleep deprivation substantially impairs normal functions; in a high-stress and high-risk workplace environment, these effects can be dangerous, deadly, and in the case of nuclear accidents, catastrophic. 
Unfortunately, it is very difficult to obtain reliable data on the exact causes of major industrial and engineering accidents, so this report by no means suggests a definite cause-and-effect relationship between sleep deprivation and major nuclear accidents. However, authors considering this subject have used information available on the timing and nature of nuclear accidents as an alternative approach. 
Three Mile Island remains the most serious United States incident in a commercial nuclear power plant. Between the hours of 4 and 6 a.m. on March 28, 1979, shift workers at the Three Mile Island plant unit 2 reactor in Pennsylvania failed to recognize the loss of core coolant water resulting from a stuck valve. Although the problem was precipitated by a mechanical problem, human error was chiefly to blame for the flawed corrective action that caused the near meltdown of the reactor later that morning. In 1985, after the Davis-Besse reactor in Ohio went into automatic shutdown at 1:35 a.m, an operator pushed the two wrong buttons in the control room, which defeated the function of the auxiliary feed-water system. Although corrective action eventually stabilized the reactor, the subsequent combination of equipment malfunctions and human errors made the situation dangerous. In the same year, operators lost control of a reactor in California at 4:14 a.m. due to human error. The nuclear plant catastrophe at Chernobyl is officially acknowledged to have begun at 1:23 a.m. as a result of human error. 
Although it cannot be proved that the human responses and errors occurring in these accidents resulted from sleep deprivation, we have a basic set of facts which point to common-sense preventative measures to improve reduce the probability of human error at nuclear plants. The effects of sleep deprivation are well understood, and we know that many nuclear accidents occur early in the morning as a result of human error. Further, reports on well-understood engineering accidents such as the Challenger disaster have explicitly pointed towards sleep deprivation as playing a major role.  These phenomena seem more than coincidental. In public and government debates following serious nuclear incidents, the emphasis is consistently placed on the extent to which technological failures and policy decisions contributed to the catastrophes. While important, they do not abrogate the responsibility to attend to factors such as sleep deprivation which have played a role in increasing the incidence of human error.
© Charlie Walker. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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