Something is Happening at Chernobyl…

35 years ago, the world experienced what was, and still is, the worst nuclear disaster in history. Reactor number four at the Chernobyl nuclear power plant had melted down, spewing radiation across Europe and creating hundreds of tons of radioactive lava, 95% of which remains semi-crystallized in dark basements to this day. And that's where most people's knowledge of the Well, almost four decades after most of the world has forgotten it, something is happening a few meters below Pripyat once again. What is it, and just how concerned should we be that Chernobyl's irradiated heart is still beating? The scope and scale of the disaster that was Chernobyl was something the world had never seen, as was the cleanup. Over 206 days, 90,000 people flooded the dangerous site to clean, catalog, and construct. The first responders were the first victims of fatal radiation doses. After those first bodies failed and robots malfunctioned, Soviet soldiers known as liquidators were brought in. These young men actually considered braving the invisible dangers because the Soviet Union had told them they could either serve two years in the concurrent Afghan war or two minutes shoveling debris off of the reactor roof. Most of these liquidators are now either sick or dead. The initial cleanup at Chernobyl was a monumental and costly effort that ended with the sarcophagus, a hastily made coffin of concrete and steel meant to keep radiation in and everything else out. It wasn't perfect, but it was never meant to be a lasting solution. Because just being in the vicinity of the failed reactor was dangerous in and of itself, nothing was constructed optimally. There were more than 1,000 square meters of cracks in the shelter and no engineer would ever consider it stable. This was when something much more impressive was designed and eventually implemented, the New Safe Confinement. Started in October 2007, the New Safe Confinement, or NSC, would be a modern tomb to rival the ancient pyramids. It was to be built taller than the Statue of Liberty and wider than the Roman Colosseum. This would require more bolts than most U.S. cities had people, and about half the Titanic's weight in steel. It was slid over the sarcophagus in late November 2017, with the promise of The NSC would allow scientists inside to study the failure, keep radiation and radioactive dust from escaping into the environment any further, and jumpstart the cleanup process with cranes installed on the interior. The space between the ruined reactor and the outside world was even pressurized. In the event of an excursion from the sarcophagus below, a pressure gradient would keep the nuclear material inside, at least for a little while. Of course, there were 30 years between when the sarcophagus was constructed and when the NSC entombed it. During that time, nature wasn't following the suggestions of scientists. No, every time it rained, water would enter the leaky coffin and soak literally hundreds of thousands of kilograms of nuclear fuel and fuel-containing materials. This was a problem because water interacts with nuclear material in a very specific way. In pretty much every nuclear reactor you've ever heard of, water is critical. Inside of a nuclear reactor, it serves three functions. The first is to cool down fuel. The second is to get turned into steam by that fuel to turn turbines and generate electricity. And the third, germane to this analysis, is to act as a moderator of nuclear reactions. This last function is at the heart of what's happening at Chernobyl right now. Neutrons flying out from radioactive materials don't just smack into other atoms and instantly cause a chain reaction. It turns out that only certain kinds of neutrons do that, the slow kind. Neutrons come screaming out of unstable nuclei at 45 million miles per hour, way too fast for other atoms to grab onto them and continue on the chain reaction. Neutrons at 1 ten-thousandth of that velocity are much better at that, and you can slow neutrons down this much by making them bump into a bunch of stuff. If you've ever played billiards, you've seen something pretty close to what's called an elastic collision, a perfect transfer of momentum. You may have even seen one ball slow down almost completely after a good smack. Looking at the math makes this easy to understand. If momentum is always conserved, then if both balls are the same mass, as you see here, then the only physical option is for one ball to slow down considerably or even completely. An effective way to slow down neutrons inside of a nuclear reactor, therefore, would be for those neutrons to hit as many similar mass particles in elastic collisions as possible and slow way down. This is exactly why you see water in a hydrogen in water has mass just like a neutron. And being a similar mass, hydrogen slows neutrons way down after colliding to the point of much more likely chain reactions and the successful operation of a nuclear reactor. This is the reason why water is a great moderator of nuclear reactions. And all of this brings us back to an inaccessible basement below Chernobyl reactor number four. Along with the cranes, sprinklers and entry points, the new safe confinement was outfitted with radiation detectors and they've been blinking above the ruins of reactor number four for 35 years. Some spots are more hot than others, but scientists expected this to be the case. The rapidly constructed sarcophagus was leaky and most of the uranium fuel at Chernobyl was still slumbering. This meant that any seasonal or heavy rain let water in submerging the fuel in pitch black basements and moderating neutron emission. This had the effect of reigniting smoldering embers of the worst nuclear disaster in history. Like lightning, neutron spikes in the radiation detectors would come and go with the rain. But this never seemed to worry the scientists of the Institute for Safety Problems of Nuclear Power Plants, the only scientific institution that has been studying the state of the sarcophagus since the accident. And to quote the scientists there, fuel containing materials were fully wet and dynamics of the neutron flux density was within seasonal trends due to the regular precipitation and condensate input, i.e. there were no potentially hazardous changes of the subcriticality of these nuclear hazardous fissile materials. End quote. And it was this institution, the ISPNPP, that has now pushed back against the flurry of breathless headlines implying some kind of imminent disaster at Chernobyl. Yes, something is indeed happening. This year, neutrons have been spiking detectors in an inaccessible basement room named 305-2. Yes, there are nuclear reactions pinging beneath Pripyat again. However, these stories are exactly why understanding the nuclear physics first is important. The nuclear scientists watching these spikes in the sarcophagus expected this to happen too. Like the expected spikes as seasonal rains dripped onto slowly deteriorating uranium fuel. You see, the new safe confinement was watertight, which meant that eventually all that water that had gotten into that cursed place would evaporate. The best hypothesis scientists currently have is that as evaporation in Chernobyl occurs without water to get in the way, neutrons are now moving through the nuclear material differently. The lava-like fuel has cracked and cooled over time and has become porous, full of holes. This change in structure, combined with the receding water and the reflectivity of the surrounding crumbling concrete, is hypothesized to account for the 40 percent increase in neutron spikes. Those 45 million mile-per-hour neutrons are shooting out once again. Quoting the representatives of the nuclear power plant in Chernobyl itself, this situation had been predicted by the ISPNPP before the NSC arch was slid over and was taking place due to the drying of over-moistened environment of black lava-like FCM. Currently, the sensors tracking the neutron flux density show constant values in all premises, with no trends to rise, and the current levels do not pose threat of self-sustained chain reaction of fission." Of course, this will only put your mind at ease if you believe the predictions of nuclear scientists working at and for the Chernobyl Power Plant. Despite the headlines, what is happening at Chernobyl is currently cause for cautious study, not panic. These are embers of a 35-year-old catastrophe, not a looming second disaster. In fact, according to the physics, nothing like what happened in 1986 is ever likely to happen there again, as remaining water to moderate a meltdown would quickly boil away, and safety protocols like sprinkler systems that spray neutron-absorbing liquids are already in place. But make no mistake here, from monitors sealed underneath an artificial shield taller than the Statue of Liberty, we know that what melted into the Earth below the Chernobyl Nuclear Power Plant in 1986, what is beneath a sarcophagus 90 kilometers north of Kiev, is not dead and buried. Until next time. Thank you so much to the very nerdy staff here at the facility for their direct and substantial support in the creation of this here video. Today especially, I'd like to recognize research assistant Applejuice, and visiting scholar Seraph the Angel. If you'd like to join the facility, no, I don't look like a cult leader, and you want to drape on a silky white lab coat, get behind-the-scenes photos every week, get members-only live streams with me, not like that, see videos early, you can go to patreon.com slash kylehill and join the facility today. And hey, if you support us just enough, you get your name on ARIA here each and every week. And as you can see, there's literally hundreds and hundreds of you, so I have no idea how I'm going to pass the time. Interesting update. You may know that my history as a science communicator and someone who likes to talk about nuclear disasters intertwines with what's called the elephant's foot. Tons of radioactive lava that melted through the basement of Chernobyl and accumulated in a elephant's foot-looking thing, wrinkled and gray. Well, when I did research on that initial video and article I wrote many years ago, it was hard enough that they had to fire an AK-47 at it to get a chunk off for study. But today, apparently, in 2021, it has more in the composition of sand. So this uranium fuel and these fuel-containing materials in Chernobyl are ever-changing and ever-deteriorating as these fuels go through their half-life. Something's always going to be happening at Chernobyl. Thanks for watching.