"Remember the calamity of the great tsunamis. Do not build any homes below this point." , but no one listened.
Hey! Lets talk about the Fukushima nuclear disaster
This is the kind of reactor used in Unit 1
This is a General electric boiling water reactor or BWR-3 the 3 means it is the 3rd design but it considered to be a 1st generation reactor. The containment around the reactor is of the mark-1 design and has a distinctive light bulb shape with a torus around the bottom that serves as the wet well for holding extra cooling water and for condensing steam released by the reactor pressure vessel. Unit-1 at Fukushima was a BWR-3 reactor in a Mk-1 containment started construction in 1969 Unit 2,3, 4 and 5 were a newer BWR-4 in a MK-1 containment and were built between 1969 and 1972 Unit 6 was a BWR-5 in a MK-2 containment that started construction in 1979.
This is a picture of the brown's ferry reactor in the USA, it is the same kind of reactor containment used in Units 1-5 of the Fukushima plant. the Lid for the reactor can be seen on the bottom of the picture, in later pictures you will see the lid for the Fukushima plant. The little people working on the thing are highlighted in red.
In the beginning there was the Tōhoku earthquake of 2011
The 2011 Tōhoku earthquake was the most powerful earthquake to hit Japan in recorded history surpassing the 869 Jogan Sanriku earthquake that happened in the year 869....1142 years ago (the magnitude of this is only an estimate since seismographs did not exist back then)
Fukushima Daiichi Administraive building
the Fukushima plant had survived major earthquakes before in the past and despite being a more powerful earthquake than the plant was designed to withstand things were stable.
All reactors shutdown when the earthquake occurred
In a nuclear power plant the reactors will shutdown if even the slightest thing happens, even jarring hydraulic lines near the reactor will cause a shutdown. A nuclear operator once said "the reactor always wants to shutdown, it is our job to keep it running". When the reactors shutdown the amount of heat they produce falls off exponentaly, most of this heat is due to radioactive decay of short lived fission products. About an hour after shutdown the typical nuclear reactor will be producing only 1% of it's original thermal output but normal output is huge (a 1000mw reactor produces enough heat to melt a bus in 10 seconds!) so it's important to keep the reactor cooled even after shutdown and failing to cool the reactor after shutdown will eventually lead to meltdown (where the fuel inside of the reactor gets hot enough to melt.)
Outside electrical power to the plant was lost after the earthquake
This is a picture of the Ultra High voltage switchgear building that was damaged by the earthquake.
Backup diesel generators supplied power for reactor cooling
In Fukushima outside power was lost when the earthquake damaged the ultra high voltage switchgear equipment sending power into the plant so backup diesel generators supplied power to coolant pumps to cool the reactor. Each reactor had it's own set of backup generators.
Then a big tsunami wave showed up
The Tōhoku earthquake occurred out in the ocean and resulted in a huge tsunami wave that was up to 20 meters (65ft) tall and 15 meters (49ft) in the Fukushima prefecture. The waves that would hit the Fukushima Daiichi nuclear plant were 14 meters tall.
It's ok because there is a big-ass seawall.
In the late 1960's the plant's designers anticipated a big huge tsunami wave hitting the plant and built a seawall around the plant to protect it. Using past events as a guide designers figured a 5.7 meter (18ft )high wall would be sufficient to protect against the largest wave that the plant would have seen....Unfortunately in 2011 the tsunami wave was 14 meters tall, over twice the height of the seawall and completely flooded the plant.
The resulting tsunami caused major problems at Fukushima
There is a truck in the room...How?!?
Emergency diesel generators were knocked out by the tsunami
This is a picture of the doorway leading into an electrical control room, electricity does not work well when submerged in water.
Tsunami damage caused a station blackout
A black out meaning the operators lost all the monitors of what the reactor was doing and they lost the ability to control the reactor remotely. This is a picture of one of the controls rooms at Fukushima, nothing was working for a while after the tsunami and despite being completely flooded some of the instruments did come back to life after a few hours. Luckily for the operators there are ways of cooling the reactors that do not require electricity or human intervention such as the isolation condensers on Unit 1 and the emergency core cooling systems for the remaining 5 reactors that are powered by steam from boiling coolant.
It's Ok because nuclear reactors have lots of things to keep them from melting down
This looks like a Mark-3 BWR containment but it's close enough, anyway just Look at all that shit! Core spray! Reactor core isolation whatevers! You'd think that all of that stuff would be enough but unfortunately most of them require power and that is an issue because after the tsunami there was no power. Luckily there is the Reactor core isolation condensers and in the older Unit-1 there are the regular Isolation condensers which can run without power.
Unit-1 Isolation condesners failed
This is a picture of an Isolation condenser like the kind used in reactor 1. the Isolation condenser condenses the cooling water that boils in the reactor that formed from residual decay heat after shutdown. It requires no electricity, has no moving parts aside from valves and can cool the reactor as long as the condenser is filled with water. Unfortunately after the earthquake shutdown the reactors the operators were cycling the Isolation condensers on and off to limit pressure losses in the reactor and the tsunami wave knocked out all electrical power including the power to open the valves controlling the Isolation condensers while the isolation condensers were turned off. Due a complete station blackout operators could not tell what state the ICs were at and due lack of understanding of their operation staff did not recognize that the ICs were not functioning as intended, there was no way to tell that the reactor was running out of water and eventually a meltdown in unit 1 would occur within a few hours.
Unit-1 Isolation condensers not working? Fuck it! Lets flood the reactor using fire engines
Due to problems with the isolation condensers in unit 1 The next line of defense was to depressurize the reactors and inject water from fire engines to flood the reactor.
What would MacGyver do?
In order to open the motor valves to vent pressure in the reactor containment and allow low pressure water to be injected workers ran out to their cars that had not been washed away, removed the batteries and hooked them up in series to power the DC motor operated valves.
Unfortunately at least half of the water pumped in from the fire engines was diverted to the steam condenser via small bypass that was unknown to operators. Water being injected from the fire engines was not sufficient to keep the core from overheating.
Three hours after the Tsunami struck, After all normal cooling systems failed, backup cooling and water injection failed to replenish water the fuel became exposed, got really hot and started melting. Another issue with meltdowns is the production of Hydrogen gas that forms from molten fuel cladding. Hydrogen gas poses a major explosion hazard.
The hydrogen gas produced by the melting zirconium fuel cladding in reactor one was supposed to be venting out though dedicated pipes and up a big tall stack, unfortunately hydrogen escaped though various leaks in the piping caused by the earthquake damage and accumulated in the upper half of the reactor buildings where it exploded. There were supposed to be vents that would open up preventing a buildup of hydrogen in the buildings but without electricity could not be opened.
Extent of explosion damage
The large explosion would suggest major damage however no one was killed by the explosions and only the flimsy metal roofs of the reinforced concrete reactor buildings were destroyed along with equipment used in refueling but no major damage occurred to the actual reactor vessel or secondary containment.
Unit 2 and 3 Reactor Core Isolation cooling begin to crap out
For units 2 and 3 the reactors had a more advanced method of backup cooling using a steam powered turbine that would circulate cooling water though the reactor. Known as the Reactor core Isolation cooling (RCIC) it was steam powered turbines drew water from the suppression to cool the reactor. The RCIC was designed to operate for up to 8 hours which was assumed to be long enough for normal reactor cooling to be restored....The RCIC would operate for 70 hours until finally pressure in the reactor became too low for the RCIC keep operating, the system was shut off, valves were actuated manually to reduce pressure and flood the reactor with water injected via fire engines.
Hydrogen explosion in units 3 and 4
After Unit 3 began to meltdown there was another hydrogen explosion in the top of the reactor building. Later Unit-4 which was in cold shutdown before the tsunami and did not meltdown would suffer a hydrogen explosion. Unit-2 which melted down last never exploded because operators were able to open vents to let hydrogen gas escape.
Water injection into Units 2 and 3
Once the reactor core isolation cooling crapped out on units 2 and 3 water injection started using fire engines, unfortunately this was delayed by problems in depressurizing the reactors enough to allow low pressure water to be injected, then by operators who were not experienced in the procedure and also by the reactor buildings exploding around them.
Unit-2 and Unit-3 meltdown
Because of the long delay in water injection by fire engines after shutting down the RCIC units-2 and 3 melted down. The core damage from the meltdown was not as bad as in unit-1 because nearly 3 days had passed since the reactor shutdown and decay heat was much lower. The reactor pressure vessel in unit-2 was likely breached by molten fuel (although to a much less extent than in unit-1).
Spent fuel pools
This is a picture of a big concrete pumping truck pouring water into the spent fuel pools of reactor 4. In the reactor buildings right next to the lid for the reactor pressure vessel is a big swimming pool where the spent fuel from the reactor chills out for a few years before they stick in dry storage casks and park it outside the building. About a week after the accident water levels started getting low and water was pumped in to keep the pools filled up. News stations had made a big deal about the possibility of the fuel pools getting empty however unlike the fuel in the reactor decay heat is low enough that the fuel will not melt or catch on fire, there is no moderator and the geometry of the fuel will not allow criticality, also it was found later by the US nuclear regulatory commission using computer simulations that without water the fuel would have gotten no hotter than 600 degrees Celsius which is not hot enough to damage the fuel or the cladding. Spent fuel being exposed to air would not have been a major disaster.
What about Unit-5 and Unit-6!?!?!?!
When the disaster struck units 5 and 6 were shutdown for refueling and there was no chance of a meltdown. The two units were of a newer design than the rest having been built in 1979 and built on slightly higher ground. Had they been fueled up during the disaster a meltdown would more than likely not have occurred since the backup diesel generators survived the tsunami and all of the core cooling systems were still functional. The two units were able to be restarted and resume generating power but 6 months after the meltdowns the Fukushima prefecture parliament voted to shut down all reactors in the prefecture indefinitely. The two units will be used for full scale training and simulation.
What about other nuclear plants?
This is the Onagawa Nuclear power plant. Onagawa Nuclear power plant was the closest to the epicenter of the earthquake and was hit by a more severe tsunami wave than Fukushima Daiichi, however the 14m high seawall surrounding the plant was able to protect it from the tsunami wave, all backup cooling systems kept functioning and it never came close to a meltdown. Several residents sought shelter in the plant's gymnasium after their homes were destroyed by the tsunami.
Fukushima Daini (Fukushima 2)
There was another Fukushima nuclear power plant a few kilometers away called Fukushima Daini ( Daiichi and Daiini mean one and two respectively). The plant was much newer and higher seawall was high enough to deflect the tsunami wave. Seawater pumps were knocked out but backup cooling continued for all units there was no disaster
Filtering contaminated water
In the haste to cool the reactors large parts of the reactor buildings, containment vessels and turbine buildings were flooded with water that has become contaminated with radioactive material by contact with melted fuel from the reactor. Soon after the workers got a handle on cooling the reactors efforts began to contain contaminated water from leaking into the environment and then to filter out the nasty radioactive bits in the water. A huge tank farm has been setup on the site of the plant and a sizable water treatment plant has been built to filter out radioactive crap using zeolite which is a rock used for making cat litter and is also good at trapping cesium molecules. The Filter media and radioactive sludge from water treatment will be stuck in cans and put somewhere where it won't bother anyone until a few 30 year half-lives pass and it stops being dangerous.
Temporary cover for Unit-1
In order to keep out the weather and to limit radioactive gasses from escaping a temporary metal cover was built over unit-1. It was been found that the amount of radioactivity being released though the reactor building is not as high as expected and since the cover will get in the way of de-fueling the reactor TEPCO plans on disassembling the cover in a year or two.
Unit 4 reactor lid visible
Unit-4 is in the best shape of all of the damaged reactors, it never melted down and while the roof blew up the building is in relatively decent shape. In this picture the busted up metal roof has been removed and the lid for the reactor containment is visible (the big yellow thing).
Inside of Unit 4
This is the new refueling platform and overhead crane for unit 4, I needed to double check that this was actually unit 4 that blew up because the new area looks really good.
Google Street view of Exclusion zone.
The whole area looks pretty depressing, there are a few cars driving around, damaged buildings, washed up cars laying around. Without people around many areas are starting to become overgrown and revert to nature.
This was a legitimate map made by NOAA to show wave heights from the earthquake.
Incorrectly atributing tsunami damage to nuclear meltdown
A few miles away from Fukushima I nuclear power plant there was an oil refinery that caught fire from the earthquake and tsunami.
Bullshit scare mongering.
750 Rads is a fatal dose of radiation. This is another misleading bullshit map put out by some anonymous person in the name of a legitimate organization.
What about all the sailers on the USS Carrier that got cancer?
The USS Ronald Reagan was sailing a few miles off the coast of japan after the tsunami and during the meltdowns at Fukushima now there is something like 70 sailors who are suing TEPCO because they got cancer. The people suing probably do have cancer and that is terrible however it is very unlikely to be due to radiation from Fukushima. Being a Nuclear powered aircraft carrier there are several Radiation monitors aboard that keep tabs on radiation levels and according to the Navy radiation levels were within safe levels. Also According to Cancer.gov 460.4 of 100,000 (0.46%) people in the United States develop cancer in a year so for a pool of 5500 people aboard a ship you would be looking at about 25 cancer cases that are going to happen anyway regardless of what anyone is exposed to.
What about radioactive fish
A handful of fish caught right outside of the plant made headlines because they had X times the legal limit of radiation which is understandable given that contaminated water is still leaking into the ocean. A study by Standford University a few months after the meltdown Found large long lived migratory fish caught near the United states did contain measurable levels of cesium-137 isotope which is not naturally occurring and is the single largest contributor to radiation from the Fukushima meltdowns. The levels of Cs-137 in the tuna were on average about 4Bq/kg wish is very low, well within legal limits and about 1/80th the levels radioactivity produced from the natural potasium-40 normally found in tuna. Here is a link to the study http://micheli.stanford.edu/pdf/Madiganetal_PNAS_2012.pdf
What about the Exclusion zones?!?!?
After the releases of radiation from the meltdowns everyone within a 12km radius of the plant was evacuated which turned out to be about of 100,000 people.
Radation levles in exclusion zones
This is a map is from safecast.org that is some sort of crowd sourced radiation detecting website. The green areas are places where people are being allowed back to live, the yellow are places that people can visit temporary and the red are placed that people cannon yet return to. Last time I checked the Japanese government made 20mSv per year the threshold value for the exclusion zone. For perspective the average background radiation is 1mSv per year in Japan and 2.3 mSv in the united states (the US has higher background radiation levels because of natural radon in the ground). - A person absorb about 6mSv of radiation from all sources natural and artificial, -50mSv is the annual dose limit for radiation workers in power plants -100mSv is the lowest proven dose that will increase a persons risk of cancer. -1000mSv will give you radiation sickness -8000mSv will kill you
Evacuations around the nuclear plant
About 100,000 people were evacuated from a 20km area around the plant. Since then it has been estimated that over 1,600 people have died as a result "stress-related illnesses and other maladies after the disaster than from injuries directly linked to the disaster." 1600 people have died trying to fleeing radiation that has killed no one.
Long term cancer risks
The 2013 world health organization published a study on lifetime cancer risks from radiation in the area outside of the exclusion zone and the workers at the plant. "The predicted magnitude of cancer risks was assessed for leukaemia, thyroid cancer, female breast cancer and all solid cancers combined. The risks were calculated over a lifetime and over the 15 years following the accident. The lifetime attributable risks (LAR) were quantitatively estimated only in the most affected parts of Fukushima prefecture. For all other locations in Japan and around the world, the radiation-related cancer risks were estimated to be much lower than the usual fluctuation in the baseline cancer risks. " http://apps.who.int/iris/bitstream/10665/78218/1/9789241505130_eng.pdf
What is next?
The disaster is over for the most part, criticality ended immediately after the earthquake, the reactors are finished melting down, cooling functions have been restored and the spent fuel pools are topped off. In the last three years work has been preformed to stabilize the reactor buildings and prevent any future earthquake or tsunami from damaging them again. Next step will be to plug leaks in the reactor buildings, wipe up any radioactive stuff, defuel the melted reactors and maybe demolish the buildings. Elsewhere around Fukushima the highly radioactive fission products like Iodine-131 have long decayed into nothing and longer lived isotopes like Cesium-137 sprinkled over the land are being carried away by wind, rain and erosion that chews away all man made structures. As the radioactive stuff decays or is removed the radioactivity in the area will keep falling, many evacuated areas are safe to move back to and hopefully more places will cool off enough to move back to.