A Brief History of: The Fukushima Daiichi Disaster (Documentary)

[Music] natural disasters have been a fear of mankind throughout history from a volcano near pompeii to an earthquake in the pacific ocean a natural disaster can devastate a whole region causing mayhem and destruction in its wake a deadly earthquake and resulting tsunami off the coast of japan would result in nearly 20 000 missing and dead a country economically wounded and a chain of events that would cause a nuclear disaster on a scale which the world had not seen since chernobyl if you like what we do here at plainly difficult consider helping the channel grow by liking commenting and subscribing let's get started [Music] we have covered many reactor incidents on this channel however something that makes today's subject unique is that the damage to equipment and the environment is worse than anything else i've covered on this channel needless to say today we are going to dive into the fukushima disaster i'm going to rate this event here on the plane of difficult disaster scale which is higher than the ines which rated it at a seven the same level as chernobyl so obviously means that my rating scale is better the fukushina daya itchy npp site lies approximately 220 kilometers north of tokyo at almost the midpoint of the pacific coast it straddles okuma and futaba townships in fukushima prefecture which is around here on a map the site is approximately 3.5 kilometers large it is operated and managed by tokyo electric power company or tepco the site houses six boiling water reactors three built by general electric two by toshiba and one by hitachi although all were designed by ge construction on the site began in 1967 on unit 1 with its commercial operation beginning in 1972 for the next seven years the remaining five units came online with unit six commissioned in october 1979. during the 12 years between 1967 and 1979 bwr design improvements led to variations between the six units on the site after unit 1 which was an earlier bwr-3 design units 2-5 were bwr-4 designs and unit 6 was a bwr-5 design because of this the power outputs of the three designs were different with unit 1 having 460 megawatts of electricity units 2-5 having 784 megawatts of electricity and unit 6 having 100 megawatts of electricity fukushima daiya ichi plant is connected to the power grid by four lines the 500 kilovolt futaba line the two 275 kilovolt okuma lines and the 66 kilovolt yono mori line to the shin fukushima substation the site was built on a bluff 25 meters above sea level originally it was intended to be at 35 meters however the designers lowered the height to reduce the strain on sea water pumps as well as making the foundations closer to stable bedrock which helps keep the plant more earthquake resistant this lowered height was thought to be tsunami safe in conjunction with an adequate seawall the reactors on site were in two groups the first one looking at the station from the sea contains units four three two and one going from left to right the rightmost group contains units five and six like all commercial nuclear reactors the end goal is the generation of heat for the purpose of making steam this is used to drive a turbine which then generates electricity right before we dive into the disaster let's have a look at how a boiling water reactor works as this type of reactor is not often covered on this channel for the purpose of simplicity this is a general overview of how the ge bwrs work however there were many variations between the three types used at the site a bwr design uses demineralized light water for both cooling and moderation much like a pressure water reactor this type of reactor is the second most common type after the pwr however unlike a pwr which uses the heat of the coolant to create steam in a secondary coolant loop in a bwr the boiling of the primary coolant is used for the steam the steam is collected in the top of the reactor before passing towards the turbines a steam generated from fission passes through the turbine after which it goes to a condenser to be returned back to water inside the condenser a secondary loop of water is used and is kept separate from the primary to stop cross contamination at fukushima seawater was used for condenser cooling water and auxiliary equipment cooling water a seawall 10 meters high from the seabed was built in front of the power station with open channels behind it that led from the power plant to the ocean water was drawn in through sluice gates and pump rims installed for each unit from there it is transferred to the condenser by pumps installed in the pump rooms the fuel used at fukushima consisted of fuel pins bundled in square arrays the fuel pins consist of low enrichment uranium oxide or mixed uranium and plutonium oxide fuel pellets enclosed and sealed in zirconium alloy cladding tubes each of the reactors had control rods for regulating the power and had 97 137 185 across the three different bwr types the rods were inserted into the reactor from underneath the control rods had the ability to scram the reactors shutting down fission in an event of an emergency in the event of a power cut backup power is generated from diesel power generators this backup system was important for powering the coolant pumps in the event of an emergency directors have two types of containment the first being the reactor primary containment vessel the second being the building in which it is housed the core is kept within a containment vessel around the vessel there is an outer containment which is enclosed by a concrete plug the plug can be moved by a crane over the spent fuel pull the spent fuel pulls is where used fuel rods can be stored the pcv has two major compartments the reactor vessel is located in the drywell the dw is connected to a second compartment the suppression chamber which holds a large amount of water and enough space to suppress pressure increases the water within the suppression chamber can be used to scrub radioisotopes from any gases released within the containment vessel the primary containment vessels were filled with nitrogen to provide prompt control of any hydrogen generated during an incident the secondary confinement is provided by the reactor building itself and is designed to try and hold any contaminants in a last line of defense of environmental protection the site had three control rooms as each was used to control two reactors although each reactor had its own panel this setup allowed close working between reactor teams each reactor's emergency diesel generators and associated equipment were stored underneath the turbine buildings between seven to eight meters below grade the backup power systems also used dc batteries these were located in the basements of the control buildings for units one two and four and in the mezzanine levels of the turbine buildings for units three five and six units one to five had two diesel generators each and unit six had free the batteries gave the power plant up to 8 hours of emergency power in the case of electrical isolation from the grid issues were raised by some engineers during construction as placement of safety critical equipment below grade had a higher risk of flooding especially when combined with the lower bluff of the site however these issues were swept away by tepco's decision to follow ge's design plans to the letter and oh boy that would come back to bite them this leads us to march 2011. three of the six units were shut down for refueling leaving one two and three in operation there were some six thousand four hundred workers on site approximately two thousand 2400 consisting of 750 tepco personnel and around 1650 contractors were working in the controlled area with approximately 2 000 carrying out work in the support of the planned refuelling unit 4 had its fuel rods removed and units 5 and 6 still had the fuel elements inside the reactors however the control rods were inserted into the core to stop fission on the 11th of march at 14 46 local time an earthquake of a magnitude of 9 lasted for 2 minutes it was caused by a sudden release of energy at the interface where the pacific tectonic plate forces its way under the north american plate the earthquake was the largest ever recorded in japan and the world's fourth largest since records began in 1900. at the time of the earthquake sensors at the plant detected ground movement and initiated a scram in the free operating reactors this was built into the design of the plant and the action controlled the reactor's reactivity the off-site power grid connections were lost during the earthquake because of this the emergency systems needed power to be supplied by the 13 on-site generators even after shut down the reactors needed power to monitor and pump coolant through the cores as after fishing the fuel elements still provide decay heat strong enough to cause fuel element melting to help with the cooling in normal shutdown the turbines are bypassed and the coolant in steam form goes straight to condensers after which it is pumped back to the core completing the cycle however during this event the reactor was completely isolated from the turbine building due to the loss of power caused by the earthquake with the usual way of cooling now isolated a backup system using the suppression pool was used unit 1 used a different system to the remaining reactors it used two closed cooling loops by sending the primary coolant through a heat exchanger using a secondary tank of cooling water once the heat was exchanged from the reactor coolant to the secondary water the primary coolant then returned to the reactor via gravity however this system was cooling down the reactor too efficiently fearing damage to the reactor vessel from extreme heat changes one of the systems was turned off this was set out in the operational procedures for units two and three an open system was used which necessitated additional water this was powered by steam from the primary coolant turning a small turbine which in turn injected water back into the reactor the steam that ran the turbine went to and accumulated in a suppression pool inside the primary containment vessel which served as a heat sink for absorbing the waste heat the water needed to continue cooling the reactor was supplied from a condensate tank once the tank was empty all the suppression pool was full water was then supplied from the pool for cooling however not only the operating reactors on the 11th of march had decay heat during refuelling the spent fuel rods are placed in pools near each reactor these are also still hot so effective cooling is normally provided by electrical power if it was just an earthquake the event would have been effectively managed using the on-site generators and batteries however 40 minutes post-seismic activity the first tidal wave just under five meters tall crashed up against the seawall which effectively protected the plant however just 10 minutes later a second 14 meter high tsunami wave was heading for the power station the wave effortlessly crashed over the seawall which only provided protection of around five meters above the normal sea level the water flooded the turbine rooms shorting out their electrical systems the wave damaged the unhoused sea water pumps this meant that essential plant systems that use seawater including the liquid called emergency diesel generators could not be called to ensure their effective operation the flooding water made its way into all buildings including the vital basements that housed the generators and their associated electrical equipment this resulted in loss of emergency ac power one air cooled generator survived and continued to supply emergency power to unit six this meant however that units one to five had total power failure the power station was designed to be able to work off dc batteries for up to eight hours in the event of a loss of ac power generation however some of these systems were also affected by the flooding inundating the functional dc systems power started to dwindle in units 1 2 and 4 15 minutes post flood due to loss of all ac and dc power the operators of units 1 and 2 could no longer monitor the reactor pressure and the reactive water levels or key systems and components used for core calling this situation had no procedure set out for the operators because of this the emergency control room supervisors were flying blind and had to find some way of resetting power to the stricken plant units 3 5 and 6 maintain power allowing the operators to observe the power status as the main control indications and controls were still functioning units 3 and 5 still had dc battery power and 6 still had full ac power to extend the time between full plant blackout on units 3 and 5 all non-essential systems were shut down in unit 3 the operators manually restarted the reactor core cooling system controlling and monitoring the reactor water injection with the available dc power unit 1's attempt to restart the shutdown cooling system failed due to loss of power and the reactor vessel created more pressure as the core began to increase in heat the high pressure disallowed the use of an external cooling source for example from an external pump after the approval of the prime minister a nuclear emergency was declared at three minutes past 7 local time with no indications due to power loss the operators at unit 1 and 2 assumed a worst case scenario of no way of calling the reactor cause which would mean potential core uncovering of unit 1 and unit 2 in other words no coolant in the core which could lead to a meltdown this information was passed on to the government bodies at around 1 minute past 9 pm an order at 2123 was given by the government to evacuate an area of around three kilometers near the plant high levels of radiation were detected in the unit one reactor building indicating core damage at 21.51 at 10 to 12 at night the reactor vessel at unit 1 showed signs of being overpressured beyond design spec the site superintendent ordered preparations for venting of the unit 1 containment vessel at 2 10 am on the 12th of march a team was able to enter the room where unit 2's reactor core isolation cooling system equipment was located and read the parameters to determine the system's status the system was confirmed working in unit 2's core as the steam being created inside the core was successfully powering the small turbine in the backup cooling system upon hearing that unit 2's cooling was still functional operators focused on dealing with the unfolding drama at unit 1. at 4 am an alternate cooling system was put into operation using fire trucks pumping seawater into unit 1 as the vessel pressure had reduced unit 1's containment measurement at 4 19 am on the 12th of march showed that pressure had decreased since the last measurement without any operator action and without an official venting route indicating that some unintentional containment pressure relief had occurred through an unknown path this coupled with an increase in radiation levels hinted at reactive vessel damage because of this the government extended the evacuation zone to 10 kilometers plans for venting of unit 1's containment was set to start at 9am on the 12th of march as soon as the fukushima prefecture authorities confirmed at 902 am after completion of the evacuation of akuma town the team started the manipulation of valves in order to arrange the path for the venting of unit 1's containment to atmosphere at 2pm the final valve was manipulated the success of the venting operation was confirmed by decrease in containment pressure at 2 30 pm initially no increase in radioactivity was seen however this would change one hour post venting and was measured at 1 millisieverts an hour near unit 1. at unit 3 after 20 and a half hours of operation the reactor core isolation cooling system ceased to operate at 11 36 am the system was unsuccessfully restarted resulting in the heat within the reactor core creating steam lowering the coolant level an automatic high pressure coolant jet system started after the level dropped past the set level a half past three pm worked to connect the mobile voltage power supplies to units 1 and 2 using an undamaged transformer in unit 2 was completed and a low voltage grid for supply of ac power to unit 1 was re-energized however before the benefits of the return of power could be reaped unit 1 exploded the upper part of the reactor building of unit 1 was severely damaged in the explosion although no damage was caused to the primary containment the secondary in the form of building was now compromised three hours later the evacuation zone was extended to 20 kilometers the cause the explosion was thought to be from hydrogen that had escaped from the reactor via an unknown path teams returned to the site to repair the damaged electrical and water feed lines after these were repaired the reactor had been without calling for around 4 hours although things were kind of back under control for unit 1 unit 3 started to become the next drama during the disaster fearing that the turbine driven high pressure cooling system would fail with the lowering steam within the reactor unit 3 was planned to be hooked up to an external water pumping source to facilitate this the high pressure system needed to be switched off for valves to be opened to be hooked up to the new cooling system the valves could not be opened whilst the operators struggled for 45 minutes the pressure within the reactor rose disallowing the external water pumping option painting themselves into a corner the operators attempted and failed to restart the high pressure system essentially leaving unit 3 with no cooling system at all an emergency at unit 3 was declared at 5 10 am on the 13th of march at 5 15 am fire engines were called up to pump water into the reactor core like had been done for unit 1. again like with unit 1 a venting path was needed to lower pressure to reduce the reactor pressure below the fire engine pump pressure required deactivation of pressure relief valve this was achieved by the use of 12-volt batteries taken from cars at the site which were collected in the common main control room of units 3 and 4. the reactor pressure vessel fell below what was needed to use the fire engine pumps an injection of boreated fresh water into the unit 3 reactor started at 9 25 am unit 3 had also gone for more than four hours without cooling at 2 15 pm high radiation dose rate of around 1 millisieverts an hour was measured near the side boundary 15 minutes later the radiation dose rate exceeded 100 to 300 millisieverts an hour at the entry doors of the unit-free reactor building at 6 30 am on the 14th the water level in unit 3 dropped as cooling water supplies that were being pumped began to dwindle at 1101 am an explosion occurred in the upper part of the unit free reactor building similar to what happened at unit 1 destroying the structure above the service floor in addition to the destruction of the alternate water injection arrangement the capability to vent the containment in unit 2 was lost at around 1 pm on the 14th unit 2 began to experience cooling issues as well in what seems to be a repeating theme reactor pressure increased as the cooling water level decreased to enable low pressure fire truck water pumping safety valves were operated to help drop the reactor pressure the fire trucks began to pump water at 8 pm at around 9 55 pm confinement radiation levels had increased substantially to 5 360 millisieverts an hour in the dry well and 383 millisieverts an hour in the suppression chamber at 10 30 pm the unit operators tasked with establishing the venting line to relieve the containment pressure when able to open the vent valves venting from the containment was unsuccessful meaning that there was little that the operators could do to stop pressure build up within the reactor containment and in the early hours of the 15th the inevitable happened in the early hours of the 15th of march explosions were heard at units 2 and 4 with the top half of unit 4's building being damaged a drop in pressure readings on the suppression chamber of unit 2 was seen this hinted in the containment of the reactor had been compromised meaning an uncontrolled release of radioactive isotopes following the events in unit 2 all personnel except essential workers required for monitoring and emergency response were instructed by the site superintendent to go to a radiologically safe location 650 people evacuated to fukushima dayani nuclear power plant site approximately 12 kilometers away white smoke or steam was seen to be coming from the top of unit 2's reactor building a radiation measurement was taken of 11.93 millisieverts an hour at the main gate at 9am an order was issued by the government authorities at 11 am requiring all residents within a 30 kilometer radius of the power plant to take shelter indoors a team needed to enter the reactor building of unit 4 to investigate the status of the spent fuel pool however upon entry they recorded radiation levels of a thousand millisieverts an hour after an aerial survey on the 16th water levels were confirmed in unit 4's pool however it was unknown about the condition of unit 3 making its pool a priority to ensure enough water was in place to stop the spent fuel from becoming uncovered spraying started on the 17th with helicopters dropping around 30 tons of sea water later fire hoses and water cannons were used to fill the pool additionally on the 20th unit 4 received water spray as well later on into march power was gradually restored to units 1 to 4 with units 5 and 6 receiving power from the only working air cooled generator units 3 and 4 were the last to receive power after being completely cut off for more than two weeks at this time seawater was swapped for boreated fresh water in the cooling efforts of the reactors meaning the situation was gradually coming back under control unit 5 was the first to be put into cold shutdown mode at 14 30 on the 20th of march 2011. this was followed by unit 6 at 1927 on the same day however the remaining units had a long journey ahead as a more stable situation was achieved in april 2012. tepco published in may 2012 an estimate of the amount of radioactivity released at fukushima which was about one thousand and twenty petibecules over the 12th to the 31st of march 500 petabecquils of iodine 131 10 petabecquiles of cesium-137 and 10 petabecquils of cesium-134 the remaining was noble gases mainly made up of xenon-133 releases to the ocean over the 26th of march to the 30th of september were thought to be about 11 petabqls of iodine 131 3.5 petrobecquerials of cesium-134 3.6 petabecquiles of cesium-137 a total of 18.1 petabecquils the release into the ocean came from the water pumped into reactors during the false cooling which had subsequently been contaminated by the damage reactor cause however the publications were only estimates and there is much uncertainty as to how much was released into the sea this is mainly due to the area being flooded at the time of the contamination of the water it was estimated that fukushima released around 1 10th of the contamination of chernobyl tests on caught fish around the area were shown to have the same levels of contamination in 2012 as they had post-accident in 2011. hinting at a more prolonged release of contaminants into the ocean post accident and exclusion zone of 20 kilometers was set up around the plant meaning residents within the zone had to leave however other towns and villages outside the 20 kilometer zone were also evacuated for decontamination in march 2012 three area definitions were set up to describe each evacuation status of the towns and villages around a stricken power plant area one is known as the evacuation cancellation prepared zone these are areas where it's confirmed but the annual dose of radiation will definitely be 20 millisieverts a year or less and the evacuation order will soon be lifted residents are allowed to visit their property but not stay the night and people in the area are not required to take protection from radiation area 2 is where residents are not permitted to live known as the restrictive residence zone areas where the annual integral dose of radiation is expected to be 20 millisieverts a year or more and where residents are ordered to remain evacuated in order to reduce the risk of radiation exposure residents can also return to this area but not stay the night as well area 3 the difficult to return zone is where it is expected that residents will not be returning home for a long time these are the most restrictive areas and entry is prohibited unless specifically allowed to and whilst in protective clothing the annual dose of radiation in these areas is expected to be 20 millisieverts a year or more within five years and the current integral dose of radiation per year is 50 millisieverts a year or more gradually as decontamination efforts were undertaken many places affected in 2011 became habitable however such areas as futiba and parts of nami and okuma are still inaccessible to residents the roughly 195 000 residents who lived in the vicinity of the plant were screened by the end of may 2011. no elevated health risks were predicted all of the 1080 children tested for thyroid gland exposure show results within safe limits according to the june iea report in december around 1700 residents were checked with the majority showing exposure levels below 1 millisieverts a year with the remaining all but 10 receiving below 5 millisieverts a year with the final 10 in excess of 10 millisieverts a year a 2012 hirosaki university study reported 46 out of 62 people tested had activated thyroids from iodine 131 the average dose was 4.2 millisieverts and 3.5 millisieverts in adults and children respectively this was much lower compared to the tests on chernobyl evacuees who received an average of around 490 millisieverts it was estimated that there were around 700 deaths from disaster related incidents for example people uprooted from homes and hospitals because of the evacuation another big contributor to health risks from such an incident is the psychological trauma linked to being near a nuclear disaster some of the worst affected people were the key workers at the plant who were faced with the fast-moving ever-increasing disaster many who worked on the recovery efforts had to complete tasks in less than favorable conditions or whilst not knowing the safety of their friends and family due to the tsunami in the region as of 2018 the japanese government has acknowledged four workers had radiation caused illnesses with one dying of lung cancer at the age of 50. a frozen wall was installed around the site to try and limit the seepage into groundwater since the meltdowns tepco was fighting a losing battle with water that flowed downhill towards the sea which made its way via fukushima's fractured reactor buildings however the frozen soil barrier had failed to completely stop water seepage for the best part of the next decade works at the site have been painfully slow with not one but three melted down reactors to deal with in april 2011 two robots sent into reactor building one recorded radiation levels as high as eleven hundred and twenty millisieverts an hour in may another robot was sent into unit 1 and discovered levels in excess of 2 000 millisieverts an hour in 2012 radiation levels were found between 31.1 and 72.9 sieverts an hour inside the containment of unit 2. the status of the fuel in units 1 to 3 was unknown as it had melted out of the reactor's cores for several years post event in 2015 another robot was sent inside the reactor confinement for unit 1. however the intense radioactivity immobilized it finally in 2017 a remote controlled robot took the first pictures of the melted core of reactor 3. in 2019 a robot with two fingers made first contact with the fuel debris in the primary containment vessel of reactor 2. a roadmap to start removing fuel from the free units was set out with unit 3's storage pool beginning in 2018. plans to begin to remove fuel from the reactors is set to begin in 2021 the japanese government so far has put 27 billion dollars into cleaning up the mess with around 75 000 workers scrubbing the roads walls roofs gutters and drains around 600 million cubic feet of grass trees and topsoil have been removed and stuffed into millions of black bags but the road to completion of decommissioning and decontamination left by the 2011 disaster will take many more decades until it's finished now the iaea report as always is well worth a read for a full dive into the disaster if you'd like me to cover the aftermath in better detail let me know in the comments and i may make it into a future video i hope you enjoyed the video if you'd like to support the channel financially you can on patreon from one dollar per creation that gets you access to votes and early access to future videos i have youtube membership as well from 99 pence per month and that gets you early access to videos too and all i have to say is thank you for watching

Channel: Plainly Difficult

Views: 418,987

Rating: 4.9172506 out of 5

Keywords: Atomic, Nuclear History, Education, Plainly Difficult, fukushima, nuclear disaster, Radiation, Japan, Worst in history, Chernobyl, Fukushima Daiichi Nuclear reactor, smarter every day, japan history, worst nuclear accident, tepco, iaea

Id: mx5aJGUXCCk

Length: 30min 31sec (1831 seconds)

Published: Sat Aug 15 2020