I watched the much-hyped HBO Mini Series. No doubt, it is a very well-made series - gripping and horrifying. It succeeds in at least two areas - scaring the hell out of people about Nuclear energy and conveying a message that Soviet Era lies created monstrous things. Both of which are true but not entirely. If you didn't know anything about Chernobyl and heard about it from this series for the first time, then I can tell you to take things with a pinch of salt. Pretty much none of the horrible scenes on screen were real, and it was, at best, a simplistic Hollywood treatment of a much more complex incident.
How do I know? Let's begin with that. I am not an expert, but I did study Nuclear Power Engineering, a graduate-level course. The Prof who taught the course is one of the leading Nuclear safety experts in India. I loved open electives in my college days. Looking back, I think I made pretty good choices, sometimes unintentionally, or maybe I just got lucky. Quantum computing, Nuclear physics to Economics and Finance. In final year, like everyone else I too had a job and had secured a good grade in my thesis as well. So, I opted for a course that would have classes in the afternoon on Thursdays and would be somewhat interesting too. (the main idea behind this was to take a course that will allow me to watch as many movies as possible and read books) but surprisingly, I did really well, and I liked it enough that I still remember a few things.
The course was all about Nuclear power and reactor designs. In the nuclear safety part of the course, Chernobyl occupied a significant portion. That was only a major Nuclear accident that ever happened. We also studied a little about Three-mile Island accident (Fukushima happened much later; I am sure it is part of the course now). I did some mathematical analysis as well, which I do not remember now. All I remember is Prof. Asked me to make the presentation in powerpoint so that he can use it in his next classes. I had made it in Latex. He jokingly said - "my guru was a mathematician and a chela too is doing this math thingy, just send me a power point." Years later, I met the same Prof at the Indian consulate in New York. I was wondering if he would recognize me when he walked to me and smiled - "Abhishek Ojha 2007??". Anyways, Chernobyl is a thing that you cannot forget! If you are reading about Chernobyl on Wikipedia after watching the series and searching for more - I have been doing that since learning about it in that graduate course in 2007.
Enough of the story to make a point that I do know a thing or two about Nuclear reactors and Chernobyl.
The universe is made of atoms, and Nuclear physics (and physics in general) is a thing of beauty. Nuclear physics is relatively easy to understand as well - the complicated part is getting the physics and design right for it to work in real life. That is - in Weapons and Reactors. The theoretical concept is simple - you begin with fissile material, a nuclide that can capture a rightly speeded or relatively slow (a thermal) neutron and undergo Fission. Fire a slowed-down neutron into a U-235 nucleus that will absorb the neutron, become unstable and split immediately into two different atoms along with two or three new neutrons. These newly generated neutrons hit other atoms of fissile thing and generate more neutrons, which in turn do the same thing… and so on…this fission thing keeps going on and becomes a chain reaction. Boom! That's Nuclear energy.
So, there are at least three tricky components (actually many more) here - getting the proper enriched fissile isotopes (such as Uranium 235), properly slowed-down neutrons and then controlling the chain reaction. Each step is very complex, intricate, and of course, at an atomic level. - Chaalu Kaise hoga? Aur ek baar ho gaya to ab control kaise hoga? Sounds like a love story.
The trick is proper physics and design - things of enormous intricacy and beauty that come with a hefty risk. But believe me, the risk is worth taking! None of it is simple, otherwise... well- all countries would have nuclear bombs or at least reactors by now. Imagine computations that give precise estimates about tiny particles' behavior in the scale of micro seconds!
If you do not want to control and let it go on its own way, the chain reaction gets unstoppable with enormous energy release in a very short time, and that's what becomes a Nuclear Weapon. But If we can control it at our will, this becomes the most valuable thing for humanity. Just like fire but at a dramatically bigger scale in every way - complexity, risk, and reward. While we are at it, there is another way to produce nuclear energy called fusion. As the name suggests, instead of splitting a heavy atom... smaller atoms join in this case to make bigger atoms with a massive release of energy. This is a thing of stars… and superstars (stars such as our sun is powered by this) where Hydrogen fuses to make Helium, Helium to Carbon to Oxygen and so on. But this requires enormous energy to begin. It also releases even more energy than Fission, so there are not yet functioning fusion reactors, but there are fusion-based weapons, called thermonuclear weapons. In simple terms, because no one really cares about controlling energy in a bomb! You can trigger a fission chain reaction first that will give enough energy for fusion, and sometimes it feeds back to another fission and then back to fusion and so on to create chaos and destruction - and you probably guessed one of the names of such bombs - the Hydrogen bomb.
All nuclear reactors to date are Fission based, so were the bombs used in Hiroshima and Nagasaki. Mini-series references few Hiroshima's going off in a reactor accident - Just to emphasize the difference between a bomb and a reactor - a reactor uses the fissile material which is only around 3-5% fissile but in a bomb, it is ~95%! A reactor releases the same energy over the years which is just in fractions of a second in case of a bomb… so the first Fact - a reactor is not a bomb! A reactor has a tightly controlled nuclear reaction with many negative feedbacks to stop the reaction if anything goes wrong; whereas bombs are made intentionally uncontrolled. (the bombs used in Japan (Little boy) contained 64kg of enriched uranium, out of which only less than a kg underwent nuclear Fission, another bomb fat man was plutonium-based.)
It is just the energy generation part which is different, the remaining parts of a reactor are still the same eons-old (well as much as electricity is old), the method of heating the water from energy, turning a turbine and producing the electricity. Just the part of burning the coal or gas is replaced with atomic Fission. Simple!
Fun Fact - It is a famously quoted that cockroaches can survive a nuclear explosion, but the Fact is they can survive but only to a point so it is not entirely true.
That was about a nuclear reactor, What about Soviet Era? I have read several good books and some very good movies about horrible things during Soviet Era, and I know how much messed up it was, but in 1986, I think things were not as bad as depicted in series. The country was way beyond Stalin Era, so it wasn't as corrupt and dictatorial. Chernobyl was a massive evacuation and clean up with around 600,000 people involved and Russian scientists did everything they can. The problem was not entirely the bureaucracy, Communist party and KGB but reality was no one knew what to do for sure! They tried different things because no one had expected this, no one really understood what exactly is happening and it is not surprising for an unprecedented accident like that in the era of first generation of nuclear reactors. Three-mile was similar, but luckily it didn't end up as catastrophic. Years later Fukushima was close enough too. Yes, the US and Japan didn't try to cover up the incident, but I guess it wasn't very different in the case of the USSR as well. The points made in mini-series are way exaggerated. Russian policy of transparency glasnost was happening by this time. Soviet scientists approached this accident and aftermath with an unprecedented sense of openness.
Let me explain by a toy example - Google for accidents when automobiles were a new thing, you will find unbelievable pictures of accidents which we cannot even imagine now! And Nuclear reactors are way more complicated than operating an automobile. Perhaps all such innovations had unfortunate accidents - airlines, trains - you can design and control only the things that you can think of. The real risk is the one that you cannot see! As humans, we do not respect the power of what we do not know. So was the case with first-gen RMBK reactors. It is easy to critic the design now! Russians knew the faults of RMBK reactors, it wasn't classified, and scientists were quickly able to pinpoint the reasons for what happened. But in a war like situation they had to come up with solutions on the go (such as dumping the mixture of sand, boron, clay and lead) and that's what happened.
The mini-series dramatizes a few things, which is fine to make a point. Another fictionalized thing is radiation from a reactor does not affect people the way it is shown in series. HBO puts out some facts at the end of the series such as two of the employees who went to open the valves of radioactively active water tanks are still alive but there are many factually wrong things in series - everyone died on bridge of death, the baby absorbed the radiation (that's not possible scientifically, but it is one of the most emotionally powerful scenes in the series), radiation is also not contagious - you do not isolate people because it will spread like some disease!, then there is helicopter crash that never really happened and that light emitting from reactor penetrating in the sky – that's fictional too. A single scientist and minister working on evacuation plan? In reality, the commission was staffed by multiple scientists, military officers, government officials and on a much larger and complex scale. Many people volunteered to help including the employees of reactor who went to open the water valves. There was nothing hidden at international convention and videos of that are available, but the main point (I think) was - they didn't know and couldn't grasp that it really was that dangerous.
And the Fact is it really wasn't that dangerous as shown in mini-series!
Apart from thyroid cancer cases, which is not fatal, there is no evidence of more deaths or defects due to the Chernobyl accident than reported numbers. Studies put minuscule amounts to fatalities caused by these thyroid cancers, statistically speaking ~100 in around 80 years! The dramatic spike in cancer rates after the incident, as claimed in series too, is wrong. The numbers put by WHO is not significant at all ~.6%. Also, nearly 80% of first respondents impacted by direct radiation survived.
What is wrong with plenty of fiction and pseudoscience in the mini-series? Such misrepresentations and stigmatizations come with a cost. Studies after the Fukushima accident show that more people were impacted by fear of nuclear radiation than actual radiation! What we do not discuss is the psycho-social impacts that harm more than radiation impacts in such incidents, Fukushima accident reported higher rates of depression, trauma, and anxiety which has direct health effects. All deaths after Fukushima happened because of these, absolutely none by radiation. While some scientists see Chernobyl and Fukushima as examples that even in the worst possible cases, Nuclear accidents have proven to be safer compared to the other environmental unfriendly ways of energy. The mini-series terrified everyone about the nuclear energy, but in reality, it is the cleanest energy in human history and the safest too.
Fact: a proper nuclear power plant releases less radioactivity into the atmosphere than a coal power plant. (Actually, it is mining and enriching uranium which is not very clean environmentally, but not many people talk about it.)
Also, radiation is not like bullets, and the reactors are not bombs. Even in the worst accidents, only a relatively small amount of matter can escape and harm only a limited number of people. Some studies show because it is so environment-friendly that nuclear energy has saved millions of lives. The problem is it is difficult to imagine something that caused as horrible as Hiroshima and Nagasaki can also make the world a safer place. After Hiroshima and Nagasaki, we are wired to think that it is monstrous. Same as we are wired to think snakes are dangerous, and we should kill them immediately, even if we know for a fact that around 85% of snake species are harmless! How difficult is it to explain that to a person?
Similarly, we are bound to see nuclear accidents as nuclear bombs! Even if we know that statistically, air travel is safer than road travel, we see air travel more dangerous. Even if we know that nuclear energy has been safer than all other modes of energy production that we know so far, we still see it as an evil.
Coming back to Nuclear buzzwords, Fission happens naturally every day at a slow rate in different materials. The most famous person that comes to mind on hearing radioactivity is Marie Curie, First and only female to win Nobel twice and in both Physics and Chemistry. She spent her life in the presence of so much radiation that her belongings (such as clothes, furniture, books, notes, etc.), now French national treasures and scientific treasures, are still so radioactive that you need to put special protective clothing to see that. She died from aplastic anemia, a rare condition linked to polonium and radium, both discovered by her. Her body was also radioactive and was therefore placed in a coffin lined with lead. For a long time, people didn't know that radioactivity is harmful, and there were once radioactive health SPAs, chocolates, kinds of toothpaste, toys etc. with radioactivity! I am not making this up; you can google.
What is radiation that we talk about? Radiation is energy traveling through space such as sunshine. The splitting of an atom releases gamma radiation, which is nothing but high-energy photons. Resulting atoms later release beta radiation as well, which is fast electrons and more gamma radiation. Mostly, radiation is helpful energy but can also cause damage to matter, mainly living tissues. In a controlled way, it too is a super useful thing, and it is omnipresent, part of the environment at harmless levels. The main forms of radiation come from the atoms in forms of alpha, beta, and gamma radiations. These rays have high penetrating power and can pass through the human body. Mass in the form of concrete, lead, or water is used to shield us from them. Röntgen was the scientist who discovered X-rays, and Röntgen, which is referred in Mini-Series is a legacy unit of measurement named after him for the exposure of X-rays and gamma rays. Like many other things in nature, banana is radioactive too, and there actually is a measure called banana equivalent dose.
Reactor design - Enriched Uranium, a fissile material, is the fuel of reactors. It is made into small pellets and then arranged into rods, which are put together as a bundle and submerged into water. Once this mechanism is set up - control and cooling are two most essential functionalities of a reactor - prevent overheating and find material that can absorb neutrons. No free neutrons mean no fission. When you want to stop the reaction or slow down - control rods made of neutron thirsty material are inserted into the core. They absorb neutrons and stop the reaction or slow it down, depending on their level. But unfortunately, it is also not as simple as it sounds; basically, It is not like flipping a switch.
Then for extra safety, everything is put within concrete and radiation shield containments, just in case. These concrete structures, too, are not simple. They are designed to be strong enough to survive earthquakes or a crashing jet airliner, that's the safety benchmark these days. Of course, Chernobyl being a first-gen reactor, didn't have the same containment standards; otherwise, probably we wouldn't know Chernobyl as we know it today. Chernobyl had design flaws and needed more human intervention than modern reactors but even a well-designed reactor is still susceptible to natural disasters, Fukushima is an example of that. Fukushima had many measures of safety, but they didn't consider losing the power of cooling generators, which sounds somewhat apparent now. As I mentioned earlier, we do not respect the power of the unknown until it happens and becomes apparent.
The most common reactor design is a light water reactor. In light water reactors, water works as coolant as well as moderator, so when more heat is produced, more water evaporates, and less is available to work as a moderator for neutrons, and that automatically slows down the reaction. This is a negative feedback loop that controls the reaction from overheating and maintains equilibrium.
In RMBK design (the one in Chernobyl), water works as a coolant but graphite blocks as moderator. Why? Because it makes these reactors run even with less enriched uranium than light water reactors, and also it gives an ability to refuel it while still running. The primary design was mainly for plutonium production to be used in weapons and not for power production. But the cost is this breaks the negative feedback loop of slowing the reaction with more steam - this is what is called the positive void coefficient. In this case, the fission reaction speeds up when more steam is produced. The Fission becomes more efficient, which leads more heat in the reactor, more reaction - more efficient - more heat - and the process continues to the meltdown of the core. A nuclear Meltdown means core damage from overheating. When RMBK reactor was running at high power, things were in equilibrium and this was never a problem but the equilibrium broke and made it unstable at low power. In a nutshell, the problem was running the reactor in low power mode created a buildup of Xenon, which is a neutron observing element, so it became difficult to maintain an appropriate level of Fission. No free neutrons, no fission, no fission, no energy. So, they removed the control rods completely to increase the reaction, but this led to the positive void coefficient thing, and things went out of control.
In case of nuclear meltdown, Nuclear fuel and fission products (such as isotopes of Iodine, krypton, cesium) flows into the coolant, super-heated steam and mixing with metals etc. it can cause explosions and eventually these can flow into environment. The mini-series shows people taking Iodine, the way it works is… It doesn't avoid or kill radiation, but because if our bodies already have enough Iodine, it will not absorb the isotope of Iodine now present in environment that is a harmful version of Iodine. We heard boron too in the series - it is a neutron absorbing material and as we know, anything that absorbs neutron slows down the reaction. Actually, scientists still debate what exactly caused the explosion. It might have been a steam explosion or a hydrogen explosion or some weird reaction after things went out of control.
Can it happen again? Or can something else happen? Generally, once we know an unknown - it becomes obvious, so chances are very low that the same thing will happen again, but something else can always happen. If you have ever designed or developed anything new, you know what I mean. No matter how much you test, there is a high chance that you missed something. You can do only so much with checklists and tests. Engineers, scientists, and designers always face this challenge before finalizing each component and making sure that it will work properly, yet there are so many products recalls every year, one of the most iconic designs of our era iPhone 4, too, had a design issue famously known as antennagate. Believe me, these things undergo very rigorous testing before they go into production. But most such design flaws are not very dangerous (although some are - In March 2019, Boeing 737 MAX was grounded globally after two nearly-new aircrafts crashed within four months, killing all 346 people). Unfortunately, Nuclear reactors fall under the extreme dangerous category, but with time and every new release, products evolve into something better, so have nuclear reactors. It is worth noting that there is no universal standard for reactors, and each country has its own regulatory and safety authorities. There still are some reactors and proposed designs (some fast breeder reactors which generate more fissile material as they generate power) with small positive void coefficient - Russia, China, Japan, Canada, and India have designed such reactors. Reactor designers find a positive void coefficient too small to matter, but then so thought Chernobyl engineers about it. The one good thing is modern reactors do more things themselves in an automated way and requires lesser human intervention.
Another interesting point that makes the point that Chernobyl didn't turn out to be as horrible as portrayed in series is other 3 reactors next to reactor 4 were functioning as late as the year 2000! Real people worked in those plants… that says a lot about all the horror that we saw about radiation killing people instantly. There are still 10 RMBK reactors functioning in different parts of Russia, of course, with improvements. The changes they made are mainly adding more inhibitors to the core to prevent reactions at low power, redesign, and increase in control rods and more fuel enrichment.
My point is - Chernobyl was a messy and grim event, and no one anticipated or was prepared for it, but there's a lot of fictionalization and exaggeration for dramatic effect. The real heroes numbered in thousands, and actual deaths were much less. Various studies reflect that radiation from Chernobyl killed, at most, 200 people. They ended up evacuating ~300,000 people and a huge area, around ~600,000 people were involved in cleaning efforts. What happened in the exclusion zone since then is still not completely clear to scientific community, some claim that life was muted and impacted while some new researches show that the area has become a safe sanctuary for many animals and plants, the life in exclusion zone is more diverse and richer now, thriving without any human interference!
In 2017, the accident site was covered in a new sarcophagus, which is a modern engineering marvel, the largest moving structure in the world. It is also a beautiful symbol of the world coming together to protect the environment. An interesting observation by scientists was the survival of a fungi within walls of the Chernobyl reactor's ruins. These particular fungi do something called radio-synthesis to convert radiation into usable energy and the fun Fact is we all do also have the same-thing in our bodies, albeit in a very small amount that these fungi use to do radio-synthesis. Who knows, we will devise a simple way to not only survive radiation but also harness it in future! Who among hunter-gatherers would have imagined controlling fire the way it is now?
In short, it is complicated.