Let me tell you a joke.
Days after the Chernobyl plant melted down General Tarakanov, aware of the extreme importance of clearing the reactor roof of radioactive graphite ahead of the weather, began accepting offers of robots from other nations to do the job.
The West Germans, very confident, delivered a tele-presence robot designed for coal mining in dangerous conditions. The robot was lifted onto the roof and set to work, pushing blocks toward the crater. After only a few minutes it ceased to function, ruined by the radiation.
The Japanese, also very confident, delivered a autonomous robot to do the job. Placed on the roof it enjoyed some success, pushing over a ton of radioactive material back into the breach before succumbing to the radiation.
Seeing that the roof was beginning to be cluttered with dead, radioactive robots General Tarakanov said, "This is nonsense! Soviet Science has developed the perfect robot for situations such as this!"
Up went the Soviet's robot and, indeed, it performed beautifully. Though less strong than the Japanese robot it functioned far longer and managed to push several tons of materials back into the reactor. After several hours, seeing that the robot was beginning to be affected by the radiation, General Tarakanov retrieved his bullhorn and called up to the roof, "Private Sidorov, you may come down now!"
It's not a very funny, I'm afraid, but such were the jokes of the Liquidators, the soldiers and volunteers tasked with the cleanup of the Chernobyl Disaster. Said in another fashion, earnestly, by the chairman of the State Committee on the Use of Nuclear Energy, A. M. Peetrosyants: "Science requires victims."
"That is something one cannot forget,"[1] says Grigori Medvedev in his "The Truth About Chernobyl". The jacket blurb for my particular copy boasts that Medvedev's book is "an exciting minute-by-minute account ... of the world's largest nuclear disaster and coverup." Make no mistake, Medvedev's book is the primary source we have, especially in the English speaking world, for insight into individual reactor operator's actions on April 26, 1986. The books and is written with great skill and insight into the plant's operation but it is not exactly what I would call exciting. Rather, it is a work of creeping horror.
Why did Unit No. 4 of the Chernobyl Nuclear Power Plant melt down? With a nod to Charles Perrow's "Normal Accidents" there were several System Accidents lurking. The most apparent is the instability of the reactor design, a "high-power channel-type reactor" (RBMK). "The core of an RBMK ... is tightly packed with graphite columns, each of which contains a tubular channel. The nuclear fuel bundled are loaded into these channels ... The tubular openings ... receive control rods, which absorb neutrons. When all the rods are lowered within the core, the reactor is shut down. As the rods are withdrawn, the chain reaction of nuclear fission begins ... The higher the rods are withdrawn, the grater the power of the reactor."[2] A little later, Medvedev notes that RBMK type reactors suffer from a "series of positive reactivity coefficients..."[3] In particular, this last means that the reactor--which can only be shutdown through the intentional movement of control rods, which must be perfectly aligned--has a tendency to increase its output, to the point of "positive shutdown": the RBMK's default state is to blow up.
More concerning, those in charge of the reactor were not nuclear experts. Chief Engineer Fomin, in control of Unit 4 at the time of the accident, was an electrical engineer by training, with no advanced understanding of nuclear facilities. "I talked to Fomin and warned him that a nuclear power station was a radioactive and extremely complex facility. ... With a knowing smile he replied that a nuclear power station was a prestigious and ultramodern place to work; and that, in any case, you didn't have to be a genius to run one ..."[4] The plant's manager, Bryukhanov, was "specialized in turbines"[5]. The plant, poorly understood by those that supervised it, was not operated with due respect to its danger. Equipment vital for the diagnosis of failures and for the safety of individuals were simply unavailable. "I asked whether those were the only radiometers they had," from the testimony of a shift foreman, "and (they) told me that they had some but they were in the safe, which had been buried in the rubble after the explosion. (They) felt that the people in charge of the plant had never expected such a serious accident."[6]
Medvedev treats the proximate cause of the accident with care, going to great lengths to establish the sequence of events of that night, explaining how a relatively common test of latent inertial energy potential of the plant's steam turbines became catastrophic: over-confidence in the infallibility of the plant and incompetence in its operation. "Thus, the emergency core cooling system was disconnected deliberately ... Apparently (the operators) were confident the reactor would not fail them. ... It is clear that the operational staff did not fully understand the physics of the reactor..."[7] is a theme played in its various repetitions throughout the text: chronic failures of communication, deliberate misinformation and an unwillingness to believe what was right before one's eyes. After to the reactor's destruction the operational staff continued to insist that the reactor had not been breached, no matter that radiation readings were off the scale of the devices on-hand and graphite, which could only have come from the very center of the reactor's core, was strewn about the plant. When told that the the radiation situation was fatal after limited exposure in many places, the plant manager responded, "There's something wrong with your instrument. Fields that high are just impossible. ... Get that thing (a radiometer capable of measuring up to 250 roentgens) out of here, or toss it in the garbage!"[8] Over and over, Medvedev documents the slow movement toward understanding of those responding to the disaster, of its immense scale. Even once the breach was accepted many people were needlessly irradiated--often fatally--for want of a clear-eyed grasp of the situation, of both the immediate and lasting dangers of radiation. "People tend to see only what is convenient for them to see--even if it costs them their lives!"[9] laments Medvedev.
The Chernobyl reactor is one of the most dramatic examples of a system designed with humans as a mere service component. The reactor, requiring constant intervention to avoid going critical, was not arranged internally such that those on-duty at the time of any incident could properly diagnose what had happened, nor had the operators been sufficiently trained--or screened for training--to make a good go at keeping the reactor in a steady state. Medvedev notes, even, that the system of feedback in the event of minor accidents was entirely severed: accidents were hushed up and no one could learn from them, all the while a 'spotless' record engendered a casual over-confidence. The reactor was presumed to be so safe, effortlessly efficient, that it had never been designed with mundane human intervention in mind, requiring, instead, in the end, heroics on a massive scale. Had the plant been designed with humans in a more elevated role it would still have, eventually, suffered a catastrophic failure--system accidents, being as they are--but fewer people would have died from radiation burns, having been issued proper equipment, and fewer civilians would have been dangerously irradiated, having been informed of the radiation risks and evacuated.
Ultimately, that's the real trick to such systems. Disasters will occur; it is the nature of the response to the disaster and the effects of the disaster which change. Consider that the response to the Apollo 13 accident had many of the same features to the Chernobyl response: redundant systems that weren't and led experts off on tangents, high trust in the correct operation of the machine and a disbelief in the instrumentation of the system post-failure. Unlike the Chernobyl operators, Mission Control and the Flight Astronauts were all highly trained domain experts, equipped with an intuitive understanding of the machine they were operating and provided by said machine tools to override its behavior. With no small effort, the lunar module was re-purposed, mid-flight, into a life-boat. However, machine-oriented systems simply are how they are. When this is good, it's very good: humans can enjoy the ride, feeling positively about how technologically clever we are. When this is bad, though, it's dreadful: not truly understanding the machine, we're at it's mercy as it travels, by itself, to it's default failure state. Maybe, if we're lucky, this is a quiet failure.
When reading "The Truth About Chernobyl" think very carefully through the descriptions of nuclear tans which turn into full-body necrotizing flesh, of firemen irradiated to death in a matter of hours, of shifts clearing debris so ruinous that the soldier's entire military mobilization lasts a mere forty-five seconds because any further work would have irradiated them too much to be of any further use. Think this all through and consider how the people tied up in the systems you build end up when the systems suffer their inevitable accidents. Very few things are so deadly serious as a nuclear reactor, of course, but failures must be considered, with great care, in the pursuit of technical excellence. Failure as a first-class concern in the design of a system adapts the system to meet the challenges human operators will face, giving them tools, insight and, ultimately, a position of supreme control over the mechanism. This is a natural result of seriously considering failure and any system which subverts the human to the machine has not been designed with graceful failure in mind, necessarily. Medvedev's "The Truth About Chernobyl" charts the progress of one such machine-oriented system, through its inevitable, catastrophic failure and on through the struggle to contain the damage. Medvedev gives the reader an outsized example of a general concern for anyone knocking mechanisms together.
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1. Grigori Medvedev: The Truth About Chernobyl (BasicBooks, 1991) 5.
2. Medvedev, The Truth About Chernobyl, 34.
3. Medvedev, The Truth About Chernobyl, 35.
4. Medvedev, The Truth About Chernobyl, 43,44.
5. Medvedev, The Truth About Chernobyl, 42.
6. Medvedev, The Truth About Chernobyl, 129.
7. Medvedev, The Truth About Chernobyl, 49.
8. Medvedev, The Truth About Chernobyl, 113-114.
9. Medvedev, The Truth About Chernobyl, 131.
Let me tell you a joke. It's not a very funny, I'm afraid, but such were the jokes of the Liquidators, the soldiers and volunteers tasked with the cleanup of the Chernobyl Disaster.