On April 26, 1986 Reactor 4 in the Ukrainian atomic energy plant Chernobyl exploded, destroying its concrete roof, polluting the surrounding territory and ultimately all of Europe with radioactive particles, and intensifying the debate about the pros and cons of atomic power and whether this kind of disaster would occur again. Yet for all of the rants and ravings of anti-nuclear proponents, it was not the technology of the Chernobyl power plant – whether it was more or less sophisticated than necessary – that caused this accident. It was human failure.
What happened at Chernobyl? Without going into a technical description of a nuclear power generator, suffice it to say that reactivity is controlled by core rods that are inserted into or backed out of the reactor core. The core produces tremendous heat, which is cooled by water that absorbs the heat to produce the steam that drives the turbines which generate electric power. In order to prevent radiation contamination from escaping, a reactor is a closed system. So after steam leaves the turbines, it cools, returning it to water, and the process starts all over again. If the heat isn’t managed correctly, the core overheats and explodes or produces a runaway meltdown.
Just prior to the accident the Chernobyl reactor was scheduled to undergo annual maintenance, which required taking it off of the power grid for a few hours. But before its operators were able to start the maintenance procedures, engineers from Moscow phoned to say they wanted the operators to conduct an experiment that required the reactor to be cut back to 25% of capacity. As the reactor wound down, the operators “disconnected” the emergency cooling system to prevent it from kicking in during the experiment. Then they got another unexpected call from Kiev requesting that the reactor remain on the grid due to an unexpected surge in electricity demand. Seven hours passed before the reactor was off the grid, putting the experiment behind schedule.
For whatever reason, in the wind-down the operators had shut off the automatic capacity control system and tried to hit the 25% capacity level using manual controls. They missed. A reactor acts like an over-damped system. This means it doesn’t respond immediately to intervention; it’s like the thermostats on the walls of our homes when the temperature is reset. Multiple inputs and over-damping cause us to think a current temperature is the result of an input we just punched in, when in fact it is the result of an input punched in sometime in the past. This likely explains why manual control caused the reactor to fall to 1% of capacity – a very dangerous unstable situation. The operators were able to coax the reactor back to 7% – still in the zone of instability – and then decided to continue the experiment. This was probably their gravest error.
The experiment required the operators to turn on all water pumps. What Moscow and the Ukrainian operators failed to anticipate (or notice) was that at reduced capacity there is less heat. More water therefore caused more cooling. This caused the reactor to automatically take off its own “brakes” – something the operators apparently didn’t notice either or, under pressure to complete the experiment in the remaining time, paid no heed to. Steam levels therefore dropped, to which the operators responded by pumping more water to make steam. This cooling dropped steam levels even more. So the operators tried to increase heat by removing more rods from the core. This appeared to do the trick in steam production but it reduced the number of core rods below the safety standard. Nevertheless, the operators decided to continue the experiment, now operating a reactor without brakes. Unknown to the operators, they were now in a “graveyard” spiral from which there could be no recovery.
Minutes later, the steam line to one of the turbines was closed, as the experiment required, which caused the steam pressure in the system to increase – an unanticipated event that hadn’t happened in previous capacity reductions. Absent the automatic steam brakes, the operators attempted a kind of emergency braking – they seemed finally to have noticed things were going wrong. In an effort to reduce heat, they tried to shove the control rods back into the reactor but that was no longer possible, because the heat that had developed in the reactor core had bent the tubes into which the rods slid. At that point there were two explosions. The rest is common knowledge.
Why did the operators violate the safety rules? They had violated them before and gotten away with it. They were an experienced team who had just won an award for keeping their reactor on the grid for long periods of uninterrupted service. The considerable self-confidence of this team was doubtless a contributing factor in the accident. Most of the time they operated the reactors intuitively not analytically, which experts tend to do. They thought they knew what they were dealing with, and they probably also thought themselves beyond the “ridiculous” safety rules devised for operators, but not for a team of experienced professionals like themselves.
Let’s contrast this with what happened at the Fukushima Daiichi power plant in northern Japan last weekend.
Shortly after Japan was hit with a magnitude 8.9 earthquake, it was slammed by the follow up tsunami in a classic one-two punch. The quake caused 11 of Japan's nuclear reactors to shut down – automatically, I might add – including three at the Fukushima power plant. Now, not only was the Japanese government dealing with the twin catastrophes of a quake and tsunami, it had to further deal with what could (not necessarily would) become a catastrophe if the nuclear reactors were damaged and their failover systems didn’t perform.
When the quake shut down Fukushima, it also kicked it off of the power grid. This deprived the plant operators of electricity, requiring them to switch on emergency diesel generators in order to maintain core cooling. Then the tsunami hit and wiped out the generators. Now the operators were forced to switch over to battery power to operate critical instrumentation and equipment. The batteries were designed as one of the backups to the backups, to provide power for cooling the core for 8 hours. And they did. Eight hours was enough time to truck in mobile generators to replace those destroyed by the tsunami.
Were they making this stuff up as they went along? No. However unlikely, multiple failures had been anticipated in designing the emergency procedures and they had been practiced repeatedly. Nevertheless, at the end of the day on Friday, Prime Minister Naoto Kan wisely decided to protect the public and declare a “nuclear emergency” which called for evacuating 200,000 people in the area encompassed by a 20 kilometer radius of the plant.
However, the mobile generators couldn’t be connected to the plant due to interface problems. So after the battery power was exhausted, and the residual heat could not be carried away, the plant operators had to begin thinking of the possibility of a core meltdown, which meant executing “loss of cooling event” procedures.
I was once a partner/investor in a software business that produced simulated nuclear power plant failure scenarios and calculated the radiation contamination levels that would exist at specified locations depending upon the type of failure. These were used to train the plant operators in every combination of malfunctions, including the destruction of the containment dome over the plant. Part of the simulated drill was the release of a contamination plume to the external environment so that a “dose assessment” of the surrounding landscape would be required in the training. For the record, a Boeing 727 at full throttle could fly into the external containment dome without damaging it enough to permit an external release, and there are three concentric containment domes over nuclear reactors – except some in Russia, which might as well have been covered with a tent.
Following procedures and their training, the Fukushima operators prepared for core meltdown. Steam builds up inside of an interior containment dome as it does in a pressure cooker. A household pressure cooker has a vent to release steam when it reaches a certain pressure to keep it from exploding. Likewise, the plant operators released steam Saturday, which was so hot that it caused an explosion. At that point sea water mixed with boric acid was pumped into the reactor, destroying the cores at a cost of billions of dollars. The only person known to have been killed in connection with the Fukushima power plant failure was hit by a crane. No one has died from radiation exposure.
Tens of thousands of Japanese have been killed by the earthquake, a subsequent tsunami, and the potential outbreak of disease. But what do the American anti-nuclear media focus on? The damage to a nuclear power plant whose operators, despite a succession of improbable events, responded in the disciplined professional manner consistent with their training.
Almost from the moment it was known that the Fukushima station was damaged, however, the hyper-hysterical press began painting an apocalypse in the making. CNN reporting headlined its news as “countdown to meltdown.” Has a nice ring, don’t you think?
The always biased, loose with the facts New York Times reported “Operators fear that if they cannot establish control, despite increasingly desperate measures to do so, the reactors could experience full meltdowns, which would release catastrophic amounts of radiation.” False. Assuming the interior containment dome was somehow destroyed, the middle containment dome is four-inch thick steel and the external containment dome is a steel-reinforced concrete and graphite envelope. In the unlikely event that the middle dome is breached, the molten reactor core would drop to the floor of the third dome, spread, and terminate reaction. Then it would cool down.
In at least one article about the reactor crisis, the accompanying photos were of burning refinery and natural gas storage tanks. The implication apparently intended was that these were reactors blazing away. This is either journalistic stupidity – not knowing the difference in the appearance of a tank farm and a nuclear reactor station – or it is journalistic dishonesty.
The anti-nuke mainstream media has devoted more column inches to speculative “what might happen” scenarios than reporting accurate up-to-the-minute status. Sure, containment domes could collapse, radiation plumes could drift on the jet stream, millions could die, and mutant babies could be born resembling American Idol’s Steven Tyler and rocker Mick Jagger. So far, none of that has happened.
Then we have the politicians sounding off as if they had a clue what they were talking about. Representative Ed Markey, a renowned opponent of nuclear power, exploited the Fukushima crisis as “another Chernobyl” and predicted “the same thing could happen here.” He called for suspension of licensing for third generation reactors that don’t use pumps to circulate cooling water but rather use convection to circulate it. The Fukushima reactors were 40 years old – and ironically two weeks away from being decommissioned when the quake and tsunami hit – but if they had the technology Markey wants to halt, we wouldn’t be reading about them.
Senator Joe Lieberman, who periodically has an affliction in which thoughts drop directly out of his brain and on his tongue, told Face the Nation last Sunday that this country should put the brakes on developing nuclear power plants. "I think we've got to kind of quietly and quickly put the brakes on until we can absorb what has happened in Japan as a result of the earthquake and the tsunami and then see what more, if anything, we can demand of the new power plants that are coming online," said Lieberman. What’s to absorb? Fukushima got hit with back to back disasters that exceeded the design specs ten-fold and still held together. The Nuclear Energy Agency of the Organization for Economic Cooperation and Development says plants constructed by today's standards are 1,600 times safer than the Fukushima plant.
Is Lieberman unaware that the U.S. Navy has had nuclear-powered ships since 1953? In those 5,800 reactor years, during which the ships steamed over 136 million miles, there have been no accidents, man-made or otherwise, and no radioactive releases.
The production of energy in large quantities will always pose risks. Refineries catch fire, coal mines collapse, sea drill rigs explode, and dams break. We learn from these failures and avoid repeating them. If environmentalists and politicians around the world use the Fukushima incident as an excuse to back away from developing nuclear energy, they will make the world even more dependent on fossil fuels, which is more dangerous than nuclear energy. Chernobyl killed 31 people. By comparison, the Paul Scherrer Institute in Switzerland calculated that in the 30 year period prior to 2000, more than 20,000 people died in severe accidents in the oil supply chain. More than 15,000 people died in severe accidents in the coal supply chain – 11,000 in China alone. The rate of direct fatalities per unit of energy production is 18 times worse for oil than it is for nuclear power.
The only nuclear power incident to occur in this country happened in 1979 at the Three Mile Island Nuclear Station. Not one person was killed. But the nuclear power industry was killed. Of the 129 stations planned when that non-event occurred, only 53 were completed because of over-regulation, anti-nuclear activists, and compliance costs. Nuclear power now supplies only 20% of the growing US energy demand. If we had built all the nuclear power plants planned in 1979, today we would be very nearly energy independent and Kyoto-compliant.
Absorb that.
What happened at Chernobyl? Without going into a technical description of a nuclear power generator, suffice it to say that reactivity is controlled by core rods that are inserted into or backed out of the reactor core. The core produces tremendous heat, which is cooled by water that absorbs the heat to produce the steam that drives the turbines which generate electric power. In order to prevent radiation contamination from escaping, a reactor is a closed system. So after steam leaves the turbines, it cools, returning it to water, and the process starts all over again. If the heat isn’t managed correctly, the core overheats and explodes or produces a runaway meltdown.
Just prior to the accident the Chernobyl reactor was scheduled to undergo annual maintenance, which required taking it off of the power grid for a few hours. But before its operators were able to start the maintenance procedures, engineers from Moscow phoned to say they wanted the operators to conduct an experiment that required the reactor to be cut back to 25% of capacity. As the reactor wound down, the operators “disconnected” the emergency cooling system to prevent it from kicking in during the experiment. Then they got another unexpected call from Kiev requesting that the reactor remain on the grid due to an unexpected surge in electricity demand. Seven hours passed before the reactor was off the grid, putting the experiment behind schedule.
For whatever reason, in the wind-down the operators had shut off the automatic capacity control system and tried to hit the 25% capacity level using manual controls. They missed. A reactor acts like an over-damped system. This means it doesn’t respond immediately to intervention; it’s like the thermostats on the walls of our homes when the temperature is reset. Multiple inputs and over-damping cause us to think a current temperature is the result of an input we just punched in, when in fact it is the result of an input punched in sometime in the past. This likely explains why manual control caused the reactor to fall to 1% of capacity – a very dangerous unstable situation. The operators were able to coax the reactor back to 7% – still in the zone of instability – and then decided to continue the experiment. This was probably their gravest error.
The experiment required the operators to turn on all water pumps. What Moscow and the Ukrainian operators failed to anticipate (or notice) was that at reduced capacity there is less heat. More water therefore caused more cooling. This caused the reactor to automatically take off its own “brakes” – something the operators apparently didn’t notice either or, under pressure to complete the experiment in the remaining time, paid no heed to. Steam levels therefore dropped, to which the operators responded by pumping more water to make steam. This cooling dropped steam levels even more. So the operators tried to increase heat by removing more rods from the core. This appeared to do the trick in steam production but it reduced the number of core rods below the safety standard. Nevertheless, the operators decided to continue the experiment, now operating a reactor without brakes. Unknown to the operators, they were now in a “graveyard” spiral from which there could be no recovery.
Minutes later, the steam line to one of the turbines was closed, as the experiment required, which caused the steam pressure in the system to increase – an unanticipated event that hadn’t happened in previous capacity reductions. Absent the automatic steam brakes, the operators attempted a kind of emergency braking – they seemed finally to have noticed things were going wrong. In an effort to reduce heat, they tried to shove the control rods back into the reactor but that was no longer possible, because the heat that had developed in the reactor core had bent the tubes into which the rods slid. At that point there were two explosions. The rest is common knowledge.
Why did the operators violate the safety rules? They had violated them before and gotten away with it. They were an experienced team who had just won an award for keeping their reactor on the grid for long periods of uninterrupted service. The considerable self-confidence of this team was doubtless a contributing factor in the accident. Most of the time they operated the reactors intuitively not analytically, which experts tend to do. They thought they knew what they were dealing with, and they probably also thought themselves beyond the “ridiculous” safety rules devised for operators, but not for a team of experienced professionals like themselves.
Let’s contrast this with what happened at the Fukushima Daiichi power plant in northern Japan last weekend.
Shortly after Japan was hit with a magnitude 8.9 earthquake, it was slammed by the follow up tsunami in a classic one-two punch. The quake caused 11 of Japan's nuclear reactors to shut down – automatically, I might add – including three at the Fukushima power plant. Now, not only was the Japanese government dealing with the twin catastrophes of a quake and tsunami, it had to further deal with what could (not necessarily would) become a catastrophe if the nuclear reactors were damaged and their failover systems didn’t perform.
When the quake shut down Fukushima, it also kicked it off of the power grid. This deprived the plant operators of electricity, requiring them to switch on emergency diesel generators in order to maintain core cooling. Then the tsunami hit and wiped out the generators. Now the operators were forced to switch over to battery power to operate critical instrumentation and equipment. The batteries were designed as one of the backups to the backups, to provide power for cooling the core for 8 hours. And they did. Eight hours was enough time to truck in mobile generators to replace those destroyed by the tsunami.
Were they making this stuff up as they went along? No. However unlikely, multiple failures had been anticipated in designing the emergency procedures and they had been practiced repeatedly. Nevertheless, at the end of the day on Friday, Prime Minister Naoto Kan wisely decided to protect the public and declare a “nuclear emergency” which called for evacuating 200,000 people in the area encompassed by a 20 kilometer radius of the plant.
However, the mobile generators couldn’t be connected to the plant due to interface problems. So after the battery power was exhausted, and the residual heat could not be carried away, the plant operators had to begin thinking of the possibility of a core meltdown, which meant executing “loss of cooling event” procedures.
I was once a partner/investor in a software business that produced simulated nuclear power plant failure scenarios and calculated the radiation contamination levels that would exist at specified locations depending upon the type of failure. These were used to train the plant operators in every combination of malfunctions, including the destruction of the containment dome over the plant. Part of the simulated drill was the release of a contamination plume to the external environment so that a “dose assessment” of the surrounding landscape would be required in the training. For the record, a Boeing 727 at full throttle could fly into the external containment dome without damaging it enough to permit an external release, and there are three concentric containment domes over nuclear reactors – except some in Russia, which might as well have been covered with a tent.
Following procedures and their training, the Fukushima operators prepared for core meltdown. Steam builds up inside of an interior containment dome as it does in a pressure cooker. A household pressure cooker has a vent to release steam when it reaches a certain pressure to keep it from exploding. Likewise, the plant operators released steam Saturday, which was so hot that it caused an explosion. At that point sea water mixed with boric acid was pumped into the reactor, destroying the cores at a cost of billions of dollars. The only person known to have been killed in connection with the Fukushima power plant failure was hit by a crane. No one has died from radiation exposure.
Tens of thousands of Japanese have been killed by the earthquake, a subsequent tsunami, and the potential outbreak of disease. But what do the American anti-nuclear media focus on? The damage to a nuclear power plant whose operators, despite a succession of improbable events, responded in the disciplined professional manner consistent with their training.
Almost from the moment it was known that the Fukushima station was damaged, however, the hyper-hysterical press began painting an apocalypse in the making. CNN reporting headlined its news as “countdown to meltdown.” Has a nice ring, don’t you think?
The always biased, loose with the facts New York Times reported “Operators fear that if they cannot establish control, despite increasingly desperate measures to do so, the reactors could experience full meltdowns, which would release catastrophic amounts of radiation.” False. Assuming the interior containment dome was somehow destroyed, the middle containment dome is four-inch thick steel and the external containment dome is a steel-reinforced concrete and graphite envelope. In the unlikely event that the middle dome is breached, the molten reactor core would drop to the floor of the third dome, spread, and terminate reaction. Then it would cool down.
In at least one article about the reactor crisis, the accompanying photos were of burning refinery and natural gas storage tanks. The implication apparently intended was that these were reactors blazing away. This is either journalistic stupidity – not knowing the difference in the appearance of a tank farm and a nuclear reactor station – or it is journalistic dishonesty.
The anti-nuke mainstream media has devoted more column inches to speculative “what might happen” scenarios than reporting accurate up-to-the-minute status. Sure, containment domes could collapse, radiation plumes could drift on the jet stream, millions could die, and mutant babies could be born resembling American Idol’s Steven Tyler and rocker Mick Jagger. So far, none of that has happened.
Then we have the politicians sounding off as if they had a clue what they were talking about. Representative Ed Markey, a renowned opponent of nuclear power, exploited the Fukushima crisis as “another Chernobyl” and predicted “the same thing could happen here.” He called for suspension of licensing for third generation reactors that don’t use pumps to circulate cooling water but rather use convection to circulate it. The Fukushima reactors were 40 years old – and ironically two weeks away from being decommissioned when the quake and tsunami hit – but if they had the technology Markey wants to halt, we wouldn’t be reading about them.
Senator Joe Lieberman, who periodically has an affliction in which thoughts drop directly out of his brain and on his tongue, told Face the Nation last Sunday that this country should put the brakes on developing nuclear power plants. "I think we've got to kind of quietly and quickly put the brakes on until we can absorb what has happened in Japan as a result of the earthquake and the tsunami and then see what more, if anything, we can demand of the new power plants that are coming online," said Lieberman. What’s to absorb? Fukushima got hit with back to back disasters that exceeded the design specs ten-fold and still held together. The Nuclear Energy Agency of the Organization for Economic Cooperation and Development says plants constructed by today's standards are 1,600 times safer than the Fukushima plant.
Is Lieberman unaware that the U.S. Navy has had nuclear-powered ships since 1953? In those 5,800 reactor years, during which the ships steamed over 136 million miles, there have been no accidents, man-made or otherwise, and no radioactive releases.
The production of energy in large quantities will always pose risks. Refineries catch fire, coal mines collapse, sea drill rigs explode, and dams break. We learn from these failures and avoid repeating them. If environmentalists and politicians around the world use the Fukushima incident as an excuse to back away from developing nuclear energy, they will make the world even more dependent on fossil fuels, which is more dangerous than nuclear energy. Chernobyl killed 31 people. By comparison, the Paul Scherrer Institute in Switzerland calculated that in the 30 year period prior to 2000, more than 20,000 people died in severe accidents in the oil supply chain. More than 15,000 people died in severe accidents in the coal supply chain – 11,000 in China alone. The rate of direct fatalities per unit of energy production is 18 times worse for oil than it is for nuclear power.
The only nuclear power incident to occur in this country happened in 1979 at the Three Mile Island Nuclear Station. Not one person was killed. But the nuclear power industry was killed. Of the 129 stations planned when that non-event occurred, only 53 were completed because of over-regulation, anti-nuclear activists, and compliance costs. Nuclear power now supplies only 20% of the growing US energy demand. If we had built all the nuclear power plants planned in 1979, today we would be very nearly energy independent and Kyoto-compliant.
Absorb that.
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