At the bottom of this post is a picture of THE conference room at the IAEA where Valery Legasov presented to the world his (then) version of the events of the Chernobyl disaster. A lot of people have asked me what I thought of the “Chernobyl” mini-series on HBO; this (longer) post is my response. Links to sources are at the bottom for any super-nerds who want to do more reading.
First of all, the series did a good job at portraying the fear, the uncertainty, and the confusion that surrounded the first few hours of the response. Most of the operators (except possibly Dyatlov, more on him later) were trained to believe the RBMK reactor was indestructible (“appeared to have succumbed to the hypnosis of excessive self-confidence, as they acted contrary to the laws of nuclear physics”, Ref [1]). When the reactor exploded, the notion that their RBMK reactor had actually exploded was so far outside anyone’s belief system that it took them hours to accept the reality at the site, and for those who could not see firsthand – it took days. This significantly stunted the response.
As bad as it seemed in the series, in my opinion the Soviet attempt to cover up or hide the accident was even worse in reality. There was a clear directive from the top (“Soviet reactor technology is the best in the world; we don’t have accidents”) and those caught in the middle were unwilling or unable to present information that countered that view. Those on the ground were unwilling to act without explicit direction from above; there was absolutely no sense of “Let’s get it done” or “Give those on the ground a modicum of autonomy to do what’s best.” The Politburo, based in Moscow, always knew best. This opinion of mine is based on countless interviews in Adam Higganbotham’s great book, “Midnight in Chernobyl” [Ref 2].
The series did an incredible job getting some of parlance of nuclear engineering into the mainstream: RBMK reactor, positive void coefficient, reactivity margin, xenon poisoning, and the concept of scram and the AZ-5 button. I mean, who could imagine that a concept as obscure as “positive void coefficient” would become commonplace? Unfortunately for me, I don’t think the series is going to inspire anyone to become a nuclear engineer, or to support nuclear power as a tool against climate change. The series did not do enough to distinguish between how bad the RBMK reactor design was and how robust modern designs are today; but then again, that wasn’t the purpose of the series.
Fun fact #1: There are 44 CANDU reactors operating today (a Canadian design, with variants operating in Romania, India, South Korea, and Argentina). All of them have positive void coefficients under certain circumstances, but the positive void coefficient doesn’t lead to runaway conditions like in the RBMK reactor.
Fun fact #2: According to INSAG-7 [Ref 3], the RBMK reactor design had as much as 5 dollars worth of positive reactivity for accident scenario of a total loss of coolant. In other words, it was 5 times as much reactivity as that needed to go prompt supercritical. That is an astonishingly bad condition; the reactor goes supercritical many times over in the case of a loss of coolant? Unbelievable.
Personally, I place the blame for the accident squarely at the feet of Anatoly Dyatlov. He was a bombastic, driven, recalcitrant physicist (not uncommon with brilliant physicists) with a damn-the-rules-they-don’t-apply-to-me attitude. He should have known better; he had already received a dose of 200 REM (2 Sieverts) during an accident at the Komsomolsk shipyard installing reactors into submarines [Ref 2]. What should have spooked him into being cautious only emboldened him. He wrote the procedure for the test they were performing on Reactor 4, and therefore he felt authorized to violate its procedures with autonomy. He published two articles in 2006 (“How It Was” [Ref 4] and “Why INSAG Has Still Got It Wrong” [Ref 5]) to defend himself, but to me, they ring hollow: he kept trying to place the blame on poor reactor design elements like reactivity margin and the degree of subcooling, but they overlook one thing. Things brings me to my next observation of the series:
The series didn’t accurately portray Just. How. Far. Outside. Normal. Operations. They. Were. Under normal conditions, arguably, the RBMK reactor worked acceptably. But there were far too many cases (Ignalina, even Reactor #1 at Chernobyl had a small core meltdown accident in 1982 due to a faulty coolant valve and operators not following procedures properly) before which showed just how razor-thin the margin was between “operating normally” and “fuel damage.” Table 4.1 (page 136) of the NRC Report [Ref 6] has the best, moment-by-moment breakdown I’ve seen. At Dyatlov’s insistence, they repeatedly turned off safety system after safety system, warning after warning. The RBMK design had 219 control rods; at the time of the accident, only 6 were in the core when there were supposed to be at least 15, and more like at least 32. “Midnight in Chernobyl” [Ref 2] does a good job at describing how harried the operators were and the crazy length they were going to just to keep the reactor from shutting itself down. It was even worse than what was shown in the series.
And lastly, Episode 5. Wow; what an awesome conclusion. The depiction of Legasov with the red and blue tiles was a great way to explain the technical aspects of what was going on. (Just like the character of Ulana Khomyuk was an amalgam of many other characters, Legasov had a bunch of other helpers.) The scene of the control room before and during the accident gives a visceral response to the viewer that’s impossible to elicit in boring technical documents and even in books. Episode 1 was tough for me to watch: like watching the movie Titanic, you know this isn’t going to end well. But Episode 5 was a great conclusion to a well-done series.
Here’s hoping we can all learn lessons beyond just, “Chernobyl was bad,” but other important lessons like, “Appropriate safety margins” and “The importance of proper management, especially during times of crisis.”
Richard Feynman famously said, “For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled.” It was true when he said it in 1986, and it’s just as true today.
References:
[1] Firsthand accounts of Chornobyl. Published 1989. https://apps.dtic.mil/dtic/tr/fulltext/u2/a335076.pdf
[2] Adam Higganbotham, “Midnight in Chernobyl.” https://www.amazon.com/Midnight-Chernobyl…/dp/B07GNV7PNH
[3] INSAG-7, the IAEA’s final report on the Chernobyl accident. https://www-pub.iaea.org/…/publicat…/PDF/Pub913e_web.pdf
[4] Dyatlov, “How it Was” https://www.neimagazine.com/…/featurehow-it-was-an…/
[5] Dyatlov, “Why INSAG Has Still Got It Wrong” https://www.neimagazine.com/…/featurewhy-insag-has…
[6] NRC report on Chernobyl. https://www.nrc.gov/docs/ML0716/ML071690245.pdf
