RE: How Does an RBMK Reactor Explode
09-04-2019, 04:22 PM (This post was last modified: 09-18-2019, 02:03 PM by Dartz.)
09-04-2019, 04:22 PM (This post was last modified: 09-18-2019, 02:03 PM by Dartz.)
---
The Chernobyl Nuclear Power Plant, and the city of Pripyat beside it, had been the brainchild of Viktor Bryukhanov. Bryukhanov had taken the city and its power plant form a paper concept, to a living, thriving thing. By 1986 Pripyat had become a model for the best in Soviet life. The shelves were well stocked, the apartments comfortable and the amenities accessible. There is a hotel, a swimming pool, multiple schools and a 'Palace of Culture', where residents can indulge in their hobbies.
Pripyat is what the Soviet Union wishes it was.
By 1986, four reactors had been completed at Chernobyl, with two more under construction. Pripyat and Chernobyl are planned to be the largest nuclear power complex in the entire world. Chernobyl reactor 4 was finished in 1983, a few weeks ahead of schedule, earning Bryukhanov an award from the government. On the other hand, there have been some corners cut. Fireproof materials for the roof were not available, so conventional materials were used. Some safety tests were failed when initially attempted - but the deadline was looming, so the reactor was put into service anyway.
The tests however, still had to be completed.
Over the next three years the test is attempted a further two times - failing each time. Finally, the fourth time, was April 26th, 1986. The test was succesful, and the reactor operators shut down the reactor.
Then it exploded.
The test was of a safety-critical system, but was not considered safety-crticial in and of itself. It was not really thought of as a test of the nuclear systems. The test program had been drawn up by an electrical engineer and from there it made its way to the desk of Nikolai Fomin, the station Chief Engineer. Fomin - only just back from work after a serious car accident - reviewed it, and not seeing it as potentially hazardous to the reactor, signed off on the proceedure. The proceedure was less than clear about what was required from the reactor.
The test, was an attempt to answer a question. If offsite power was lost due to accident or grid failure, and no other sources of power were available to the reactor, how would the electrically driven cooling pumps be operated? These pumps had to be kept running - they could not be permitted to stop. The reactor did have emergency diesel generators, but these took a full minute to start up. The pumps themselves each required 30MW of power. They can each move 12 Megalitres of water per hour. And there are 8 of them - of which 6 were normally in use.
If, at full power, the reactor were to loose cooling water and the control rods were to somehow fail to fully insert, it was calculated that it would take just 40 seconds for the fuel channels in the core would begin to buckle and warp. They would loose all resiliance. A breach in just three fuel channels out of the more than 1600 in the reactor could introduce enough steam pressure into the reactor chamber to lift the lid off the reactor - like the lid on a boiling pot hopping. Everything attached to the lid - the fuel channels, the control rods, would then be pulled out of position, potentially to the point where they would jam in place, leaving the reactor endlessly accelerating itself while all the remaining water boiled off.
Suffice to say, it was necessary to find another source of sufficient energy to keep the pumps running.
This was the reactors own turbine generator. At the first moment of an accident, the throttle valve to the turbine would close, but sheer force of inertia would keep the turbine and its generator spinning. Thousands of tons of steel rotating at 2500rpm may have just enough remaining energy to keep the reactor pumps circulating. Doing this, involved careful switching and regulation of the generator, both to keep the turbine from slowing too quickly, and to keep enough power flowing to run the pumps.
This test is important enough that Deputy-Chief engineer Anatoly Dyatlov chooses to supervise it personally. Dyatlov was not well liked - by all accounts he was an abrasive man, and very strict about professionalism. He was the teacher who would not let you have your pudding, without eating your meat. But at the same time, Dyatlov was fair - if you ate your meat you got your pudding. It didn't matter - the appearrance of him in the room always ratcheted the tension up. Everyone was afraid of making a mistake under his watch because he would be merciless. Nothing would be overlooked.
Also in the control room of Reactor 04 that night was the team operating the reactor. There are three main areas of responsibility. The Reactor engineer is responsible solely for maintaining the balance of reactivity in the core, keeping the core alive and operating at a stable power point. A pump engineer, is solely responsible for maintaining the flow of water through the reactor, and balancing it against the power produced to keep steam flowing to the turbine. The turbine engineer, monitors the turbine, condensers and generator, to make the best use ot steam generated.
The groundwork for the test is laid during the previous dayshift. The emergency core cooling system is disabled - a process which takes hours manually cranking valves closed - to prevent it from being triggered accidentally by the test. The dayshift operators also wind the power of the reactor down from its normal 3000 MW, down to 1500MW. The reactor operators measure core power based on the heat energy produced inside the core - the thermal power - a figure which is typically three times higher than the electrical energy output.
The test proceedure calls for the reactor to be at a self-sustaining power level. This is set around and about 700Mw thermal. Before they can do this, the day-shift are told to maintain power by the local grid controller.
It isn't until after midnight, and a shift change, that Chernobyl is given permission to reduce power. The dayshift has long gone home, and the night shift has taken over.
Aleksandr Akimov, the Shift supervisor, and Leonid Toptunov - who at age 25 was a Senior reactor engineer - will now be responsible for the reactor. Controlling the pumps, will be Boris Solyarchuk, overseen by Yuriy Tregub who stuck around from the dayshift to see what happened. The Turbine and its generator, are to be the responsibility of Igor Kirchenbaum. Observing, are two trainees - Viktor Proskuryarkov and Aleksandr Kudryavtsev. Elsewhere in the plant, a team from the turbine's manufacturer will take the opportunity to run vibration tests on the turbines. There are other hangers on in the control room, watching, curious about the test.
Just after midnight, Dyatlov orders the reactor's power be brought down to 700.
Toptunov begins to work the power down. As he winds the reactor down, Xenon is still being produced according to the high power levels from 6 hours previously. Toptunov has to precariously balance a reactor that suddenly seems to be trying harder and harder to shut itself down, as more and more negative reactivity is added to the core by the Xenon. It gets harder and hard to reduce the power safely.
Under the gaze of Dyatlov, a mistake is made. To try and stabilise Power, a setting is switched. The setting has the opposite effect of that intended.
The chain reaction collapses. The reactor stalls.
With power below 30MW, the test is fucked. There isn't even enough energy to spin up the turbine. Proceedure calls for the reactor to be shut down. This would allow any Xenon in the reactor to decay, and make restarting it easier. Dyatlov overrides proceedure, commanding Power be raised immediately. This is not necessarily unsafe, provided the reactivity margins of the reactor aren't compromosied.
According to some, Akimov objects to Dyatlov. There is a discussion between the pair. Dyatlov overrules him. What is certain, is that Akimov restarts the reactor.
But the reactor doesn't want to start.
The Xenon poisoning is so strong, the reactor is effectively completely poisoned out.
Akimov and Toptunov withdraw control rods. They withdraw almost all the control rods they can but still the reactor does not want to start. They disconnect some of the emergency rods from the computer control, and withdraw them from the core. Of the two hundred and eleve control rods, over two hundred are taken clear out of the reactor. They are all at the exact same, zero, position. The graphite displacers at the tip of the rod are now dead centre in the reactor, with a meter either side of the displacer being filled with liquid water.
The power level in the reactor grinds up to 200MW.
It's barely enough to spin up the turbine to the required speed, but the reactor is self-sufficient.
Dyatlov is satisfied. It's enough to complete the test.
On the other hand, the low power levels are creating problems for Stolyarchuk running the pumps. Water is moving too fast through the reactor to boil. Water levels in the steam seperators are getting too high - risking liquid water being ingested into the steam turbine. This would destroy the turbine. An automatic emergency shutdown is triggered, threatening to terminate the chain reaction and finish the test again.
Dyatlov orders the emergency shutdown to be overriden. This is not a violation of proceedure. It's permitted to disable the automatic emergency shutdown when the reactor is at low power levels.
The low power level still causes trouble. In order to make enough steam to keep the turbine spinning, hot water is being recirculated back to the reactor from the steam seperators, faster than it can be cooled. It is hot enough to begin to flash to steam inside the circulating pumps. Still, Stolyarchuk is able to stabilise flow and keep steam flowing to the turbine. The reactor is now stabilised - the difficult part is over.
At 1:40:03, Dyatlov orders the test be begun.
Kirchenbaum closes the throttle valve to the turbine. The turbine begins to coast. The generator is disconnected, and switched over to directly supply half of the cooling pumps. For safety reasons, half of the pumps are left running at full power using grid electricity. Normally, the reactor would have shut itself down as soon as the throttle valve closed. But the automatic shutdown has been disabled. The reactor continues to operate at 200MW of power.
As the generator slows, so do the pumps. Less and less water moves through the reactor. More and more steam is generated. The positive void coefficient begins to take effect The reactor control system automatically compensates for this. Power level remains constant throughout the test.
For forty seconds, everything proceeds as normal. Everything looks normal.
The test is succesful. The stalling generator is able to maintain the pumps for long enough for the generators to start.
There is no moment of forboding. There is no sense of impending doom.
With the test almost completed, Akimov calmly chooses to shut down the reactor - instructing Toptunov to smother it. There is a button on the reactor operator's control panel, hidden behind a wax-sealed guard labelled AZ-5. AZ-5, in this case, being translated as Emergency Protection System 5. The button immediately forces all control rods to be inserted into the reactor at once.
This should terminate the reaction.
Toptunov puts his finger on the button and holds it. It has to be held in place, or else the rods will stop moving.
The control rods begin to move into the reactor core, sliding down their channels. The graphite displacers push forward, pushing water out of the reactor ahead of them. This water, which aborbs neutrons, is replaced by graphite, which moderates neutrons. Reactivity is added to the bottom of reactor, even as it is being removed from the top.
If multiple control rods are moving together, enough reactivity could be added to momentarily cause an overall increase in power.
At this moment, a two hundred control rods are moving in unison, pushing reactivity down into the bottom of the core. More and more water is being converted to steam, creating voids which further increase reactivty.
So long as the reactor stays within the delayed-critical regime, this is not a problem. It will take seconds for the control rods to push through this regime - not long enough for the power to even start to run away with itself. This is what the designers expect will happen. This is what has always happened.
This is not what happens.
Power begins to rise - it rises far faster than it should. Steam forms. Reactivity increases. Heat increases. More steam forms. In a small section of the core - either through a unique combination of fresher fuel, or slightly less poisoning, or a large steam void - the reactivity added by the control rod tips passes that one dollar mark for one brief instant. It becomes Prompt Critical. Instead of taking seconds or minutes to increase, the reaction is now only limited by the time it takes for each neutron to find the next atom. Fuel elements shatter.
In one moment, the reactor power is in the hundreds of megawatss. The next, it exceeds 22000MW - eight times it's normal operating limit. It is drawn by the datalogger as a vertical line on the graph, running straight off the top. For one brief instant, Chernobyl Reactor 4 has become a nuclear bomb.
Water in the reactor surrounding this point is flash boiled. The steel structure of the reactor itself is melted and boiled by the intense release of energy. Above this pocket of rapidly expanding steam is a slug of liquid water. As far as the rest of the reactor is concerned, nothing unusual is happening - it is currently shutting down.
This changes in an instant. This bubble of steam rapidly expands, ramming the remaining water in the reactor out of its way. The fuel rod channelsburst open, flooding the core chamber with high pressure steam. In moments, the reactor chamber overpressurises, blasting the reactor lid clean off the top of the reactor, tearing every single control rod and fuel rod channel free of the reactor stack. The lid drops back down onto its side, a tangle of control and fuel rods trailing behind it like some hideous medusa. The bottom plate of the reactor blasts downwards to the foundations, bursting every single pipe beneath. Any remaining water in the core immediately flash-boils to steam.
The explosion rattles the men in the control room. But they have no idea what's really happened - there is no 'Core exploded' indicator light. Stolyarchuk sees this on his control panel as a water hammer. Trugub sees every single pressure relief valve at once open - something that should theoretically be impossible. The datalogger records the moment as a surge in water level in the steam drums, and as a momentary push back against the force of the main circulating pumps.
For a few seconds, these pumps continue to run normally, picking up speed. There is still water enough in the remains of the cooling circuit to keep them supplied, even if they are now pumping water into an open reactor pit.
All of this water pours across superheated steel and graphite. It doesn't even boil - the sheer heat of the graphite cracks it apart, splitting water into oxygen and hydrogen. A spark from any one of a hundred broken cables lights this off in one massive explosion - more powerful than the first
The second explosion blows the building clean open, collapsing one of the pump rooms, killing technician Valery Khodemchuk instantly. The core of the reactor is ejected to the sky, fragments of burning graphite lighting spot fires across the remaining roof of the building. Radioactive fuel rods fall onto the turbine hall below. The remnants of the graphite in the reactor ignite, burning like the devils own barbeque, spewing hot radiation high into the atmosphere.
The radiation from the reactor core is so powerful, it is ionising the air itself splitting the molecules of the atmosphere apart. A bright laser-beam of blue light reaches like a searchlight to the heavens, marking the birth of a new and terrible Godzilla.
That is how an RBMK reactor explodes.
--
The Chernobyl Nuclear Power Plant, and the city of Pripyat beside it, had been the brainchild of Viktor Bryukhanov. Bryukhanov had taken the city and its power plant form a paper concept, to a living, thriving thing. By 1986 Pripyat had become a model for the best in Soviet life. The shelves were well stocked, the apartments comfortable and the amenities accessible. There is a hotel, a swimming pool, multiple schools and a 'Palace of Culture', where residents can indulge in their hobbies.
Pripyat is what the Soviet Union wishes it was.
By 1986, four reactors had been completed at Chernobyl, with two more under construction. Pripyat and Chernobyl are planned to be the largest nuclear power complex in the entire world. Chernobyl reactor 4 was finished in 1983, a few weeks ahead of schedule, earning Bryukhanov an award from the government. On the other hand, there have been some corners cut. Fireproof materials for the roof were not available, so conventional materials were used. Some safety tests were failed when initially attempted - but the deadline was looming, so the reactor was put into service anyway.
The tests however, still had to be completed.
Over the next three years the test is attempted a further two times - failing each time. Finally, the fourth time, was April 26th, 1986. The test was succesful, and the reactor operators shut down the reactor.
Then it exploded.
The test was of a safety-critical system, but was not considered safety-crticial in and of itself. It was not really thought of as a test of the nuclear systems. The test program had been drawn up by an electrical engineer and from there it made its way to the desk of Nikolai Fomin, the station Chief Engineer. Fomin - only just back from work after a serious car accident - reviewed it, and not seeing it as potentially hazardous to the reactor, signed off on the proceedure. The proceedure was less than clear about what was required from the reactor.
The test, was an attempt to answer a question. If offsite power was lost due to accident or grid failure, and no other sources of power were available to the reactor, how would the electrically driven cooling pumps be operated? These pumps had to be kept running - they could not be permitted to stop. The reactor did have emergency diesel generators, but these took a full minute to start up. The pumps themselves each required 30MW of power. They can each move 12 Megalitres of water per hour. And there are 8 of them - of which 6 were normally in use.
If, at full power, the reactor were to loose cooling water and the control rods were to somehow fail to fully insert, it was calculated that it would take just 40 seconds for the fuel channels in the core would begin to buckle and warp. They would loose all resiliance. A breach in just three fuel channels out of the more than 1600 in the reactor could introduce enough steam pressure into the reactor chamber to lift the lid off the reactor - like the lid on a boiling pot hopping. Everything attached to the lid - the fuel channels, the control rods, would then be pulled out of position, potentially to the point where they would jam in place, leaving the reactor endlessly accelerating itself while all the remaining water boiled off.
Suffice to say, it was necessary to find another source of sufficient energy to keep the pumps running.
This was the reactors own turbine generator. At the first moment of an accident, the throttle valve to the turbine would close, but sheer force of inertia would keep the turbine and its generator spinning. Thousands of tons of steel rotating at 2500rpm may have just enough remaining energy to keep the reactor pumps circulating. Doing this, involved careful switching and regulation of the generator, both to keep the turbine from slowing too quickly, and to keep enough power flowing to run the pumps.
This test is important enough that Deputy-Chief engineer Anatoly Dyatlov chooses to supervise it personally. Dyatlov was not well liked - by all accounts he was an abrasive man, and very strict about professionalism. He was the teacher who would not let you have your pudding, without eating your meat. But at the same time, Dyatlov was fair - if you ate your meat you got your pudding. It didn't matter - the appearrance of him in the room always ratcheted the tension up. Everyone was afraid of making a mistake under his watch because he would be merciless. Nothing would be overlooked.
Also in the control room of Reactor 04 that night was the team operating the reactor. There are three main areas of responsibility. The Reactor engineer is responsible solely for maintaining the balance of reactivity in the core, keeping the core alive and operating at a stable power point. A pump engineer, is solely responsible for maintaining the flow of water through the reactor, and balancing it against the power produced to keep steam flowing to the turbine. The turbine engineer, monitors the turbine, condensers and generator, to make the best use ot steam generated.
The groundwork for the test is laid during the previous dayshift. The emergency core cooling system is disabled - a process which takes hours manually cranking valves closed - to prevent it from being triggered accidentally by the test. The dayshift operators also wind the power of the reactor down from its normal 3000 MW, down to 1500MW. The reactor operators measure core power based on the heat energy produced inside the core - the thermal power - a figure which is typically three times higher than the electrical energy output.
The test proceedure calls for the reactor to be at a self-sustaining power level. This is set around and about 700Mw thermal. Before they can do this, the day-shift are told to maintain power by the local grid controller.
It isn't until after midnight, and a shift change, that Chernobyl is given permission to reduce power. The dayshift has long gone home, and the night shift has taken over.
Aleksandr Akimov, the Shift supervisor, and Leonid Toptunov - who at age 25 was a Senior reactor engineer - will now be responsible for the reactor. Controlling the pumps, will be Boris Solyarchuk, overseen by Yuriy Tregub who stuck around from the dayshift to see what happened. The Turbine and its generator, are to be the responsibility of Igor Kirchenbaum. Observing, are two trainees - Viktor Proskuryarkov and Aleksandr Kudryavtsev. Elsewhere in the plant, a team from the turbine's manufacturer will take the opportunity to run vibration tests on the turbines. There are other hangers on in the control room, watching, curious about the test.
Just after midnight, Dyatlov orders the reactor's power be brought down to 700.
Toptunov begins to work the power down. As he winds the reactor down, Xenon is still being produced according to the high power levels from 6 hours previously. Toptunov has to precariously balance a reactor that suddenly seems to be trying harder and harder to shut itself down, as more and more negative reactivity is added to the core by the Xenon. It gets harder and hard to reduce the power safely.
Under the gaze of Dyatlov, a mistake is made. To try and stabilise Power, a setting is switched. The setting has the opposite effect of that intended.
The chain reaction collapses. The reactor stalls.
With power below 30MW, the test is fucked. There isn't even enough energy to spin up the turbine. Proceedure calls for the reactor to be shut down. This would allow any Xenon in the reactor to decay, and make restarting it easier. Dyatlov overrides proceedure, commanding Power be raised immediately. This is not necessarily unsafe, provided the reactivity margins of the reactor aren't compromosied.
According to some, Akimov objects to Dyatlov. There is a discussion between the pair. Dyatlov overrules him. What is certain, is that Akimov restarts the reactor.
But the reactor doesn't want to start.
The Xenon poisoning is so strong, the reactor is effectively completely poisoned out.
Akimov and Toptunov withdraw control rods. They withdraw almost all the control rods they can but still the reactor does not want to start. They disconnect some of the emergency rods from the computer control, and withdraw them from the core. Of the two hundred and eleve control rods, over two hundred are taken clear out of the reactor. They are all at the exact same, zero, position. The graphite displacers at the tip of the rod are now dead centre in the reactor, with a meter either side of the displacer being filled with liquid water.
The power level in the reactor grinds up to 200MW.
It's barely enough to spin up the turbine to the required speed, but the reactor is self-sufficient.
Dyatlov is satisfied. It's enough to complete the test.
On the other hand, the low power levels are creating problems for Stolyarchuk running the pumps. Water is moving too fast through the reactor to boil. Water levels in the steam seperators are getting too high - risking liquid water being ingested into the steam turbine. This would destroy the turbine. An automatic emergency shutdown is triggered, threatening to terminate the chain reaction and finish the test again.
Dyatlov orders the emergency shutdown to be overriden. This is not a violation of proceedure. It's permitted to disable the automatic emergency shutdown when the reactor is at low power levels.
The low power level still causes trouble. In order to make enough steam to keep the turbine spinning, hot water is being recirculated back to the reactor from the steam seperators, faster than it can be cooled. It is hot enough to begin to flash to steam inside the circulating pumps. Still, Stolyarchuk is able to stabilise flow and keep steam flowing to the turbine. The reactor is now stabilised - the difficult part is over.
At 1:40:03, Dyatlov orders the test be begun.
Kirchenbaum closes the throttle valve to the turbine. The turbine begins to coast. The generator is disconnected, and switched over to directly supply half of the cooling pumps. For safety reasons, half of the pumps are left running at full power using grid electricity. Normally, the reactor would have shut itself down as soon as the throttle valve closed. But the automatic shutdown has been disabled. The reactor continues to operate at 200MW of power.
As the generator slows, so do the pumps. Less and less water moves through the reactor. More and more steam is generated. The positive void coefficient begins to take effect The reactor control system automatically compensates for this. Power level remains constant throughout the test.
For forty seconds, everything proceeds as normal. Everything looks normal.
The test is succesful. The stalling generator is able to maintain the pumps for long enough for the generators to start.
There is no moment of forboding. There is no sense of impending doom.
With the test almost completed, Akimov calmly chooses to shut down the reactor - instructing Toptunov to smother it. There is a button on the reactor operator's control panel, hidden behind a wax-sealed guard labelled AZ-5. AZ-5, in this case, being translated as Emergency Protection System 5. The button immediately forces all control rods to be inserted into the reactor at once.
This should terminate the reaction.
Toptunov puts his finger on the button and holds it. It has to be held in place, or else the rods will stop moving.
The control rods begin to move into the reactor core, sliding down their channels. The graphite displacers push forward, pushing water out of the reactor ahead of them. This water, which aborbs neutrons, is replaced by graphite, which moderates neutrons. Reactivity is added to the bottom of reactor, even as it is being removed from the top.
If multiple control rods are moving together, enough reactivity could be added to momentarily cause an overall increase in power.
At this moment, a two hundred control rods are moving in unison, pushing reactivity down into the bottom of the core. More and more water is being converted to steam, creating voids which further increase reactivty.
So long as the reactor stays within the delayed-critical regime, this is not a problem. It will take seconds for the control rods to push through this regime - not long enough for the power to even start to run away with itself. This is what the designers expect will happen. This is what has always happened.
This is not what happens.
Power begins to rise - it rises far faster than it should. Steam forms. Reactivity increases. Heat increases. More steam forms. In a small section of the core - either through a unique combination of fresher fuel, or slightly less poisoning, or a large steam void - the reactivity added by the control rod tips passes that one dollar mark for one brief instant. It becomes Prompt Critical. Instead of taking seconds or minutes to increase, the reaction is now only limited by the time it takes for each neutron to find the next atom. Fuel elements shatter.
In one moment, the reactor power is in the hundreds of megawatss. The next, it exceeds 22000MW - eight times it's normal operating limit. It is drawn by the datalogger as a vertical line on the graph, running straight off the top. For one brief instant, Chernobyl Reactor 4 has become a nuclear bomb.
Water in the reactor surrounding this point is flash boiled. The steel structure of the reactor itself is melted and boiled by the intense release of energy. Above this pocket of rapidly expanding steam is a slug of liquid water. As far as the rest of the reactor is concerned, nothing unusual is happening - it is currently shutting down.
This changes in an instant. This bubble of steam rapidly expands, ramming the remaining water in the reactor out of its way. The fuel rod channelsburst open, flooding the core chamber with high pressure steam. In moments, the reactor chamber overpressurises, blasting the reactor lid clean off the top of the reactor, tearing every single control rod and fuel rod channel free of the reactor stack. The lid drops back down onto its side, a tangle of control and fuel rods trailing behind it like some hideous medusa. The bottom plate of the reactor blasts downwards to the foundations, bursting every single pipe beneath. Any remaining water in the core immediately flash-boils to steam.
The explosion rattles the men in the control room. But they have no idea what's really happened - there is no 'Core exploded' indicator light. Stolyarchuk sees this on his control panel as a water hammer. Trugub sees every single pressure relief valve at once open - something that should theoretically be impossible. The datalogger records the moment as a surge in water level in the steam drums, and as a momentary push back against the force of the main circulating pumps.
For a few seconds, these pumps continue to run normally, picking up speed. There is still water enough in the remains of the cooling circuit to keep them supplied, even if they are now pumping water into an open reactor pit.
All of this water pours across superheated steel and graphite. It doesn't even boil - the sheer heat of the graphite cracks it apart, splitting water into oxygen and hydrogen. A spark from any one of a hundred broken cables lights this off in one massive explosion - more powerful than the first
The second explosion blows the building clean open, collapsing one of the pump rooms, killing technician Valery Khodemchuk instantly. The core of the reactor is ejected to the sky, fragments of burning graphite lighting spot fires across the remaining roof of the building. Radioactive fuel rods fall onto the turbine hall below. The remnants of the graphite in the reactor ignite, burning like the devils own barbeque, spewing hot radiation high into the atmosphere.
The radiation from the reactor core is so powerful, it is ionising the air itself splitting the molecules of the atmosphere apart. A bright laser-beam of blue light reaches like a searchlight to the heavens, marking the birth of a new and terrible Godzilla.
That is how an RBMK reactor explodes.
--
Oh sweet meteor of death
Fall upon us.
Deliver us in fire
To Peace everlasting.
Fall upon us.
Deliver us in fire
To Peace everlasting.