Have you ever heard of the bat and ball puzzle? It's a maths puzzle. Cedric buys a cricket ball for ten pence. Let's imagine that it's the 1950s. You can't buy a cricket ball for ten pence nowadays, but let's imagine it's the 1950s.
He buys a cricket call for ten pence. He buys a bat as well. The bat is one pound more expensive than the ball. How much does he pay in total for the bat and ball?
Instinctively most people would say one pound and ten pence. The ball is ten pence. The bat is a pound more expensive equals a pound. One pound ten pence.
But that's wrong. The bat isn't a pound. It's a pound more than 10p, which is £1.10, and then you add on 10p for the ball equals £1.20. I remember the first time I worked this out in my head. It felt incredible, as if a huge rush of refreshing air had blown into my mind. I felt as if I understood the universe. I was intelligent!
Pripyat's main square
But that's wrong. The bat isn't a pound. It's a pound more than 10p, which is £1.10, and then you add on 10p for the ball equals £1.20. I remember the first time I worked this out in my head. It felt incredible, as if a huge rush of refreshing air had blown into my mind. I felt as if I understood the universe. I was intelligent!
I remember thinking of all the things I could do with my intelligence. The limitless horizons of the universe were within my grasp. The feeling faded, but for a while it was magical. Numbers.
Intelligence is not enough. The ability to solve maths problems is not enough. Neither is writing, or the ability to play guitar. Mastery of tools is just the first step. You still have to beat the metal; write the symphony; use your knowledge of maths to prove once and for all that the gravitational constant is indeed constant. That is where I failed.
But, oh, that magic feeling. It took me an age to understand what went on inside Chernobyl's number four reactor in the early hours of 26 April 1986, and even though I think I understand the technical aspects there are so many things I'll never understand, at least not fully. The culture for example.
Technically you're not supposed to go into or climb on the buildings - it's unsafe - but the tour operators aren't dummies. This is why I'm not naming the company I picked, because I don't want them to get in trouble. It would take just one dead American tourist to put a bunch of Ukranian tour guides out of work and perhaps even behind bars.
Intelligence is not enough. The ability to solve maths problems is not enough. Neither is writing, or the ability to play guitar. Mastery of tools is just the first step. You still have to beat the metal; write the symphony; use your knowledge of maths to prove once and for all that the gravitational constant is indeed constant. That is where I failed.
But, oh, that magic feeling. It took me an age to understand what went on inside Chernobyl's number four reactor in the early hours of 26 April 1986, and even though I think I understand the technical aspects there are so many things I'll never understand, at least not fully. The culture for example.
As mentioned in the previous post I'm not like most other people on the internet. I'm British, not American, so modern Ukraine isn't as jarring as it might be if I was an upper-middle class Californian. When I think of the Soviet Union I think of Britain in the 1970s, but with secret policemen on every street corner and no David Bowie.
A year after Chernobyl there was another atomic accident, this time in Goiania, Brazil. Some scavengers broke into an abandoned cancer treatment centre and stole part of an abandoned radiotherapy machine. It was a powerful gamma radiation source used to deliver targeted radiotherapy, but they didn't know that. From their point of view it was a piece of scrap with glowing blue pellets inside it. They passed it on to a local scrap metal dealer, who took it home to show his family.
They were fascinated by the supernatural blue glow that came from inside the device. They broke it open and passed the radioactive pellets to their friends, who fell ill. Eventually the authorities realised what was going on and intervened, but four people were given lethal doses of radiation, including the scrapyard owner's six-year-old daughter-in-law. Dozens more were contaminated by radioactive debris that had leaked from the container.
It's easy to mock those people. How could they have been so stupid? But perhaps they didn't think a lethal radiation source would be left behind in a derelict hospital. There was just one guard, who took that night off to visit the cinema. Perhaps they simply didn't know about radiation. I didn't grasp the fact that radiotherapy involves radiation until I was a grown-up. Until then assumed it was something to do with radios, or something.
Every generation has a different past and a different future. We are driven by ghosts on a radar screen, shadows cast by bonfires, unknowable illusions conjured by the inner light of faith. The staff on duty at Chernobyl that night were the product of a system and a culture of which I know nothing. They had different dreams and different fears, they lived in a different world.
They had been asked to run a test. Nuclear reactors need a lot of electricity to keep going. Ordinarily this comes from the reactor itself, but in the event of a malfunction there is a backup generator. The problem was that Chernobyl's backup generator took several minutes to bring online, so the authorities decided to find out if the inertia of the freewheeling reactor turbine could generate power even after the nuclear reaction had been quenched.
The test was scheduled for the daytime, but there was an emergency so it was put off until late at night. I have no idea if the night shift was less well-briefed than the day shift. The issue of individual responsibility for the disaster is still a thorny subject. Twenty-six years earlier, in 1960, there was a huge explosion at the Soviet rocket base in Baikonur. An ICBM fired its upper stage while the rocket was still being fuelled. Almost a hundred people were killed in the fireball.
Among the dead was Marshal Mitrofan Nedelin, their leader. The investigative commission decided to punish no-one because, in the words of General Secretary Leonid Brezhnev, "the guilty have already been punished". Whatever firing squad the authorities had ready for Nedelin was redundant because he was already dead.
If the Chernobyl accident was the result of human error the people responsible for pushing the buttons paid for it with their lives. They died slowly, their insides burned by radiation. Their bodies were buried in metal coffins in order not to contaminate the soil. A handful of Chernobyl's senior staff were sentenced to hard labour, and by the time their sentences were over the Soviet Union no longer existed and they were effectively unemployable. The men who made the system found themselves unemployed and irrelevant a few years later. The guilty were punished.
The disaster had two immediate technical causes. The first was Xenon poisoning. When Uranium-235 decays it spits out neutrons. Most of the neutrons fly off into the air, but some of them crash into other atoms of Uranium-235, causing them to spit out neutrons too. The end result is a nuclear chain reaction of neutrons smashing into U-235 atoms, which decay and fire out neutrons that smash into U-235 atoms etc. If you compress all this into a tiny ball the result is a nuclear explosion.
The smashed U-235 atoms leave behind little chunks of atomic debris called fission products. One such product is Xenon-135. Most of the fission products have no effect on the nuclear reaction, but Xenon-135 absorbs neutrons and slows the reaction down. Ordinarily the flow of neutrons quickly burns away the Xenon, but if too much builds up inside the reactor rods the neutrons grind to a halt and the power drops. This is Xenon poisoning. Xenon-135 evaporates in a little over nine hours, but the team working on the reactor that night couldn't wait nine hours, they had a deadline.
There's an experiment you can do. Heat a pan of water until it boils, then drop in a piece of ice. In a few seconds the whole pan stops boiling. The cold ice is just enough to push the water below the boiling point, but when the ice melts the pan starts boiling again. Imagine you want to boil away the ice really quickly, so you turn the gas all the way up. That's more or less what happened at Chernobyl.
During the test the technicians at Chernobyl slowly deactivated the reactor, but Xenon-135 started to build up within the fuel rods, which caused the reactor power to decrease much faster than the staff expected. They didn't want to wait for the Xenon to decay naturally, so they withdrew most of the control rods in order to boost the reactor's power and burn off the Xenon. For a while this worked.
Apparently the staff managed to run the test, although history doesn't record if it was successful or not. By the time they finished most of the Xenon had burned away. The control rods were still disengaged, and when the Xenon evaporated the reaction started to go into overdrive because there was nothing left to block the neutrons. One of the technicians hit the emergency scram button, which sent the control rods back down into the reactor, but the results were unexpectedly catastrophic.
The second technical cause of the disaster was the design of the reactor itself. Let's talk about water. Water has several functions in a nuclear reactor. It generates steam that powers the reactor's turbine. It draws heat away from the fuel rods and stops them from melting. It can also be used to raise or lower the power of the reaction by moderating the flow of neutrons.
The moderating effect of water is slightly counter-intuitive. Water slows down neutrons, and a lot of water will block the neutrons entirely and stop the reaction. Paradoxically a little bit of water actually makes the reaction more powerful, because slow neutrons sustain a reaction better than fast neutrons. Imagine that slow neutrons are big fat blundering chunks of energy smashing their way through the fuel rods whereas fast neutrons are tiny little high-speed bullets that immediately shoot off into the ether.
Nuclear reactors are designed so that the individual fuel rods are subcritical. By themselves they can't sustain a nuclear chain reaction. They don't produce enough neutrons. In order to start a nuclear reaction the rods have to be placed next to each other, at which point the flow of neutrons between the rods is in theory high enough to make the reaction start.
But even then modern reactors are designed so that their array of fuel rods is also slightly subcritical. The nuclear reaction doesn't start until water is added to the reactor. If the water leaks or boils away the nuclear reaction stops because the neutrons are going too fast to sustain a chain reaction.
Modern reactors are not immune to failure. If a water-moderated reactor loses its water the nuclear reaction stops, but there's nothing to stop the fuel rods from overheating and melting. This is what happened at Fukushima. The plant operators at Fukushima shut down the reactor properly, but the loss of cooling water meant that some of the fuel rods melted down, wrecking the interior of the plant and releasing nuclear contamination into the environment. A meltdown is a catastrophe, but it's a slower and more manageable catastrophe than a massive steam explosion.
At Chernobyl the water wasn't supposed to be part of the nuclear reaction. It was used purely for heat transfer, but the designers still had to compensate for its presence. When the control rods were pulled out of the reactor cooling water rushed into the channels, which reduced the reactor power slightly, so the rods were designed with graphite tips. Graphite slows down neutrons and boosts the nuclear reaction, the idea being that as the water rushed into the control rod channels the graphite tips would boost the reaction just enough to stop the power suddenly dropping.
The problem is that during the final stages of the disaster most of the cooling water had boiled into steam, which doesn't absorb neutrons at all. As the control rods pushed down into the reactor their graphite tips boosted the power, counteracting water that was no longer there, and in a split-second there was a massive positive feedback loop. The heat shot up and deformed the rods, jamming them in place, and then the runaway reaction caused the remaining water - thirty thousand gallons of it - to erupt into a violent steam explosion.
The resulting blast threw the concrete lid of the containment vessel to one side, opening the reactor core to the turbine hall. A few seconds later an even more violent explosion blew open the roof of the building and threw chunks of burning graphite and nuclear fuel into the surrounding environment. A raging fire began to send a cloud of radioactive smoke into the environment.
A year after Chernobyl there was another atomic accident, this time in Goiania, Brazil. Some scavengers broke into an abandoned cancer treatment centre and stole part of an abandoned radiotherapy machine. It was a powerful gamma radiation source used to deliver targeted radiotherapy, but they didn't know that. From their point of view it was a piece of scrap with glowing blue pellets inside it. They passed it on to a local scrap metal dealer, who took it home to show his family.
They were fascinated by the supernatural blue glow that came from inside the device. They broke it open and passed the radioactive pellets to their friends, who fell ill. Eventually the authorities realised what was going on and intervened, but four people were given lethal doses of radiation, including the scrapyard owner's six-year-old daughter-in-law. Dozens more were contaminated by radioactive debris that had leaked from the container.
It's easy to mock those people. How could they have been so stupid? But perhaps they didn't think a lethal radiation source would be left behind in a derelict hospital. There was just one guard, who took that night off to visit the cinema. Perhaps they simply didn't know about radiation. I didn't grasp the fact that radiotherapy involves radiation until I was a grown-up. Until then assumed it was something to do with radios, or something.
Every generation has a different past and a different future. We are driven by ghosts on a radar screen, shadows cast by bonfires, unknowable illusions conjured by the inner light of faith. The staff on duty at Chernobyl that night were the product of a system and a culture of which I know nothing. They had different dreams and different fears, they lived in a different world.
They had been asked to run a test. Nuclear reactors need a lot of electricity to keep going. Ordinarily this comes from the reactor itself, but in the event of a malfunction there is a backup generator. The problem was that Chernobyl's backup generator took several minutes to bring online, so the authorities decided to find out if the inertia of the freewheeling reactor turbine could generate power even after the nuclear reaction had been quenched.
The test was scheduled for the daytime, but there was an emergency so it was put off until late at night. I have no idea if the night shift was less well-briefed than the day shift. The issue of individual responsibility for the disaster is still a thorny subject. Twenty-six years earlier, in 1960, there was a huge explosion at the Soviet rocket base in Baikonur. An ICBM fired its upper stage while the rocket was still being fuelled. Almost a hundred people were killed in the fireball.
Among the dead was Marshal Mitrofan Nedelin, their leader. The investigative commission decided to punish no-one because, in the words of General Secretary Leonid Brezhnev, "the guilty have already been punished". Whatever firing squad the authorities had ready for Nedelin was redundant because he was already dead.
If the Chernobyl accident was the result of human error the people responsible for pushing the buttons paid for it with their lives. They died slowly, their insides burned by radiation. Their bodies were buried in metal coffins in order not to contaminate the soil. A handful of Chernobyl's senior staff were sentenced to hard labour, and by the time their sentences were over the Soviet Union no longer existed and they were effectively unemployable. The men who made the system found themselves unemployed and irrelevant a few years later. The guilty were punished.
The disaster had two immediate technical causes. The first was Xenon poisoning. When Uranium-235 decays it spits out neutrons. Most of the neutrons fly off into the air, but some of them crash into other atoms of Uranium-235, causing them to spit out neutrons too. The end result is a nuclear chain reaction of neutrons smashing into U-235 atoms, which decay and fire out neutrons that smash into U-235 atoms etc. If you compress all this into a tiny ball the result is a nuclear explosion.
The smashed U-235 atoms leave behind little chunks of atomic debris called fission products. One such product is Xenon-135. Most of the fission products have no effect on the nuclear reaction, but Xenon-135 absorbs neutrons and slows the reaction down. Ordinarily the flow of neutrons quickly burns away the Xenon, but if too much builds up inside the reactor rods the neutrons grind to a halt and the power drops. This is Xenon poisoning. Xenon-135 evaporates in a little over nine hours, but the team working on the reactor that night couldn't wait nine hours, they had a deadline.
There's an experiment you can do. Heat a pan of water until it boils, then drop in a piece of ice. In a few seconds the whole pan stops boiling. The cold ice is just enough to push the water below the boiling point, but when the ice melts the pan starts boiling again. Imagine you want to boil away the ice really quickly, so you turn the gas all the way up. That's more or less what happened at Chernobyl.
During the test the technicians at Chernobyl slowly deactivated the reactor, but Xenon-135 started to build up within the fuel rods, which caused the reactor power to decrease much faster than the staff expected. They didn't want to wait for the Xenon to decay naturally, so they withdrew most of the control rods in order to boost the reactor's power and burn off the Xenon. For a while this worked.
Apparently the staff managed to run the test, although history doesn't record if it was successful or not. By the time they finished most of the Xenon had burned away. The control rods were still disengaged, and when the Xenon evaporated the reaction started to go into overdrive because there was nothing left to block the neutrons. One of the technicians hit the emergency scram button, which sent the control rods back down into the reactor, but the results were unexpectedly catastrophic.
The second technical cause of the disaster was the design of the reactor itself. Let's talk about water. Water has several functions in a nuclear reactor. It generates steam that powers the reactor's turbine. It draws heat away from the fuel rods and stops them from melting. It can also be used to raise or lower the power of the reaction by moderating the flow of neutrons.
The Chernobyl reactor is built on the river Pripyat. The reactor is behind me; you're not allowed to take pictures this close from this angle.
The moderating effect of water is slightly counter-intuitive. Water slows down neutrons, and a lot of water will block the neutrons entirely and stop the reaction. Paradoxically a little bit of water actually makes the reaction more powerful, because slow neutrons sustain a reaction better than fast neutrons. Imagine that slow neutrons are big fat blundering chunks of energy smashing their way through the fuel rods whereas fast neutrons are tiny little high-speed bullets that immediately shoot off into the ether.
Nuclear reactors are designed so that the individual fuel rods are subcritical. By themselves they can't sustain a nuclear chain reaction. They don't produce enough neutrons. In order to start a nuclear reaction the rods have to be placed next to each other, at which point the flow of neutrons between the rods is in theory high enough to make the reaction start.
But even then modern reactors are designed so that their array of fuel rods is also slightly subcritical. The nuclear reaction doesn't start until water is added to the reactor. If the water leaks or boils away the nuclear reaction stops because the neutrons are going too fast to sustain a chain reaction.
Modern reactors are not immune to failure. If a water-moderated reactor loses its water the nuclear reaction stops, but there's nothing to stop the fuel rods from overheating and melting. This is what happened at Fukushima. The plant operators at Fukushima shut down the reactor properly, but the loss of cooling water meant that some of the fuel rods melted down, wrecking the interior of the plant and releasing nuclear contamination into the environment. A meltdown is a catastrophe, but it's a slower and more manageable catastrophe than a massive steam explosion.
At Chernobyl the water wasn't supposed to be part of the nuclear reaction. It was used purely for heat transfer, but the designers still had to compensate for its presence. When the control rods were pulled out of the reactor cooling water rushed into the channels, which reduced the reactor power slightly, so the rods were designed with graphite tips. Graphite slows down neutrons and boosts the nuclear reaction, the idea being that as the water rushed into the control rod channels the graphite tips would boost the reaction just enough to stop the power suddenly dropping.
The problem is that during the final stages of the disaster most of the cooling water had boiled into steam, which doesn't absorb neutrons at all. As the control rods pushed down into the reactor their graphite tips boosted the power, counteracting water that was no longer there, and in a split-second there was a massive positive feedback loop. The heat shot up and deformed the rods, jamming them in place, and then the runaway reaction caused the remaining water - thirty thousand gallons of it - to erupt into a violent steam explosion.
The resulting blast threw the concrete lid of the containment vessel to one side, opening the reactor core to the turbine hall. A few seconds later an even more violent explosion blew open the roof of the building and threw chunks of burning graphite and nuclear fuel into the surrounding environment. A raging fire began to send a cloud of radioactive smoke into the environment.
There's some debate about the nature of the second explosion. The prevailing theory is that the intense heat caused the remaining steam to split into oxygen and hydrogen, which exploded because hydrogen is very reactive. It's generally accepted that it couldn't have been a nuclear explosion, because that only happens if the atomic material is compressed at the moment of detonation. No-one was there to witness it, and the plant's instruments were destroyed.
Two of the reactor's staff were killed immediately, buried by debris. For a few weeks the official death toll only included those two people, which was accurate but misleading, because most of the staff on duty that night were given lethal doses of radiation. The dosage was too high for their equipment to measure but they could taste it. For the most part they survived for a few weeks, a few hung on for a couple of months.
As of 2018 the official death toll is 37, including four helicopter crewmembers killed in a crash during the clean-up operation. There are rumours that many of the "liquidators" were worked until near-death, at which point they were shipped off to other parts of the Soviet Union to die out of sight. Furthermore the uncertain effects of chronic radiation sickness has frustrated attempts to come up with a definitive death toll. The World Health Organisation estimates 4,000 excess deaths as a result of the disaster. A study by a member of the International Agency for Research on Cancer estimates 9,000 excess deaths plus over twenty thousand extra cancer cases, not necessarily fatal.
On an economic level I very much doubt that the extra money from disaster tourism will ever compensate for the loss of several towns plus an expensive radar array and a nuclear power complex plus the cost of cleaning up the disaster area. Belarus, just over the border, doesn't even get money from tourists. The Soviet Union initially tried to clean up the area by itself, but after the collapse Chernobyl fell down the list of Russia's economic priorities, and now the zone is managed by international agencies.
On a political level the disaster appalled General Secretary Mikhail Gorbachev, who took a dim view of the old guard's attempt to brush it under the carpet. A few weeks later he gave a televised speech that poured scorn on international alarm at the accident, but his words have none of the reality-distorting chutzpah of vintage Soviet propaganda. If nothing else the lack of transparency made his novel new policy of glasnost look like a hollow sham, which angered him because he really did believe that greater transparency was a good thing.
Two of the reactor's staff were killed immediately, buried by debris. For a few weeks the official death toll only included those two people, which was accurate but misleading, because most of the staff on duty that night were given lethal doses of radiation. The dosage was too high for their equipment to measure but they could taste it. For the most part they survived for a few weeks, a few hung on for a couple of months.
As of 2018 the official death toll is 37, including four helicopter crewmembers killed in a crash during the clean-up operation. There are rumours that many of the "liquidators" were worked until near-death, at which point they were shipped off to other parts of the Soviet Union to die out of sight. Furthermore the uncertain effects of chronic radiation sickness has frustrated attempts to come up with a definitive death toll. The World Health Organisation estimates 4,000 excess deaths as a result of the disaster. A study by a member of the International Agency for Research on Cancer estimates 9,000 excess deaths plus over twenty thousand extra cancer cases, not necessarily fatal.
On an economic level I very much doubt that the extra money from disaster tourism will ever compensate for the loss of several towns plus an expensive radar array and a nuclear power complex plus the cost of cleaning up the disaster area. Belarus, just over the border, doesn't even get money from tourists. The Soviet Union initially tried to clean up the area by itself, but after the collapse Chernobyl fell down the list of Russia's economic priorities, and now the zone is managed by international agencies.
On a political level the disaster appalled General Secretary Mikhail Gorbachev, who took a dim view of the old guard's attempt to brush it under the carpet. A few weeks later he gave a televised speech that poured scorn on international alarm at the accident, but his words have none of the reality-distorting chutzpah of vintage Soviet propaganda. If nothing else the lack of transparency made his novel new policy of glasnost look like a hollow sham, which angered him because he really did believe that greater transparency was a good thing.
I can't help but draw parallels with the Challenger disaster of 1986. In both cases the potential safety risks were deliberately overlooked by an organisation keen to maintain a schedule, but in the words of Richard Feynman, Nobel Prize-winning physicist and member of the commission selected to investigate the disaster, "reality must take precedence over public relations, for nature cannot be fooled."
It would be nice to think that Feynman's contributions to the Challenger investigation were lauded and acted upon, but seventeen years later exactly the same culture he damned lost Columbia and its seven crewmembers; in contrast the Russian nuclear industry has not had a major nuclear accident since Chernobyl, so perhaps people can change. If there's one thing I've learned from Rocky IV, it's that people can change.
It would be nice to think that Feynman's contributions to the Challenger investigation were lauded and acted upon, but seventeen years later exactly the same culture he damned lost Columbia and its seven crewmembers; in contrast the Russian nuclear industry has not had a major nuclear accident since Chernobyl, so perhaps people can change. If there's one thing I've learned from Rocky IV, it's that people can change.
