The Fukushima Daiichi nuclear disaster (福島第一原子力発電所事故,
Fukushima Dai-ichi (pronunciation) genshiryoku
hatsudensho jiko) was a nuclear accident at
the Fukushima Daiichi Nuclear Power Plant
in Ōkuma, Fukushima Prefecture.
The disaster was the most severe nuclear accident
since the 26 April 1986 Chernobyl disaster
and the only other disaster to be given the
Level 7 event classification of the International
Nuclear Event Scale.The accident was started
by the Tōhoku earthquake and tsunami on 11
March 2011.
On detecting the earthquake, the active reactors
automatically shut down their fission reactions.
Because of the reactor trips and other grid
problems, the electricity supply failed, and
the reactors' emergency diesel generators
automatically started.
Critically, they were powering the pumps that
circulated coolant through the reactors' cores
to remove decay heat, which continues after
fission has ceased.
The earthquake generated a 14-meter-high tsunami
that swept over the plant's seawall and flooded
the plant's lower grounds around the Units
1–4 reactor buildings with sea water, filling
the basements and knocking out the emergency
generators.
The resultant loss-of-coolant accidents led
to three nuclear meltdowns, three hydrogen
explosions, and the release of radioactive
contamination in Units 1, 2 and 3 between
12 and 15 March.
The spent fuel pool of previously shutdown
Reactor 4 increased in temperature on 15 March
due to decay heat from newly-added spent fuel
rods; but did not boil down sufficiently to
expose the fuel.In the days after the accident,
radiation released to the atmosphere forced
the government to declare an ever larger evacuation
zone around the plant, culminating in an evacuation
zone with a 20-kilometer radius.
All told, some 154,000 residents evacuated
from the communities surrounding the plant
due to the rising off-site levels of ambient
ionizing radiation caused by airborne radioactive
contamination from the damaged reactors.Large
amounts of water contaminated with radioactive
isotopes were released into the Pacific Ocean
during and after the disaster.
Michio Aoyama, a professor of radioisotope
geoscience at the Institute of Environmental
Radioactivity, has estimated that 18,000 terabecquerel
(TBq) of radioactive caesium 137 were released
into the Pacific during the accident, and
in 2013, 30 gigabecquerel (GBq) of caesium
137 were still flowing into the ocean every
day.
The plant's operator has since built new walls
along the coast and also created a 1.5-kilometer-long
"ice wall" of frozen earth to stop the flow
of contaminated water.While there has been
ongoing controversy over the health effects
of the disaster, a 2014 report by the United
Nations Scientific Committee on the Effects
of Atomic Radiation (UNSCEAR) and World Health
Organization projected no increase in miscarriages,
stillbirths or physical and mental disorders
in babies born after the accident.
An ongoing intensive cleanup program to both
decontaminate affected areas and decommission
the plant will take 30 to 40 years, plant
management estimate.On 5 July 2012, the National
Diet of Japan Fukushima Nuclear Accident Independent
Investigation Commission (NAIIC) found that
the causes of the accident had been foreseeable,
and that the plant operator, Tokyo Electric
Power Company (TEPCO), had failed to meet
basic safety requirements such as risk assessment,
preparing for containing collateral damage,
and developing evacuation plans.
At a meeting in Vienna three months after
the disaster, the International Atomic Energy
Agency faulted lax oversight by the Ministry
of Economy, Trade and Industry, saying the
ministry faced an inherent conflict of interest
as the government agency in charge of both
regulating and promoting the nuclear power
industry.
On 12 October 2012, TEPCO admitted for the
first time that it had failed to take necessary
measures for fear of inviting lawsuits or
protests against its nuclear plants.
== Overview ==
The Fukushima Daiichi Nuclear Power Plant
comprised six separate boiling water reactors
originally designed by General Electric (GE)
and maintained by the Tokyo Electric Power
Company (TEPCO).
At the time of the Tōhoku earthquake on 11
March 2011, Reactors 4, 5, and 6 were shut
down in preparation for re-fueling.
However, their spent fuel pools still required
cooling.Immediately after the earthquake,
the electricity-producing Reactors 1, 2, and
3 automatically shut down their sustained
fission reactions by inserting control rods
in a legally mandated safety procedure referred
to as a SCRAM, which ends the reactors' normal
running conditions.
As the reactors were unable to generate power
to run their own coolant pumps, emergency
diesel generators came online, as designed,
to power electronics and coolant systems.
These operated nominally until the tsunami
destroyed the generators for Reactors 1–5.
The two generators cooling Reactor 6 were
undamaged and were sufficient to be pressed
into service to cool the neighboring Reactor
5 along with their own reactor, averting the
overheating issues the other reactors suffered.The
largest tsunami wave was 13–14 meters (43–46
feet) high and hit approximately 50 minutes
after the initial earthquake, overwhelming
the plant's seawall, which was 10 m (33 ft)
high.
The moment of impact was recorded by a camera.
Water quickly flooded the low-lying rooms
in which the emergency generators were housed.
The flooded diesel generators failed soon
afterwards, resulting in a loss of power to
the critical coolant water pumps.
These pumps were needed to continuously circulate
coolant water through the Generation II reactors
for several days to keep the fuel rods from
melting, as the fuel rods continued to generate
decay heat after the SCRAM event.
The fuel rods would become hot enough to melt
during the fuel decay time period if an adequate
heat sink was not available.
After the secondary emergency pumps (run by
back-up electrical batteries) ran out, one
day after the tsunami on 12 March, the water
pumps stopped and the reactors began to overheat.
As workers struggled to supply power to the
reactors' coolant systems and restore power
to their control rooms, a number of hydrogen-air
chemical explosions occurred, the first in
Unit 1 on 12 March, and the last in Unit 4,
on 15 March.
It is estimated that the hot zirconium fuel
cladding-water reaction in Reactors 1–3
produced 800–1,000 kilograms (1,800–2,200
lb) of hydrogen gas each.
The pressurized gas was vented out of the
reactor pressure vessel where it mixed with
the ambient air, and eventually reached explosive
concentration limits in Units 1 and 3.
Due to piping connections between Units 3
and 4, or alternatively from the same reaction
occurring in the spent fuel pool in Unit 4
itself, Unit 4 also filled with hydrogen,
resulting in an explosion.
In each case, the hydrogen-air explosions
occurred at the top of each unit, that was
in their upper secondary containment buildings.
Drone overflights on 20 March and afterwards
captured clear images of the effects of each
explosion on the outside structures, while
the view inside was largely obscured by shadows
and debris.Coinciding with the well understood
implications of a loss of coolant accident,
the insufficient cooling eventually led to
meltdowns in Reactors 1, 2, and 3.
The full extent of the movement of the resulting
corium is unknown but it is now considered
to be at least through the bottom of each
reactor pressure vessel (RPV), residing somewhere
between there and the water-table below each
reactor, in a similar manner to what was observed
at reactor 4 in Chernobyl.
As of September 2018, one cancer fatality
was the subject of a financial settlement,
to the family of a former station workman.
while approximately 18,500 people died due
to the earthquake and tsunami.
The maximum predicted eventual cancer mortality
and morbidity estimate according to the linear
no-threshold theory is 1,500 and 1,800, respectively,
but with the strongest weight of evidence
producing an estimate much lower, in the range
of a few hundred.
In addition, the rates of psychological distress
among evacuated people rose fivefold compared
to the Japanese average due to the experience
of the disaster and evacuation.In 2013, the
World Health Organization (WHO) indicated
that the residents of the area who were evacuated
were exposed to low amounts of radiation and
that radiation-induced health impacts are
likely to be low.
In particular, the 2013 WHO report predicts
that for evacuated infant girls, their 0.75%
pre-accident lifetime risk of developing thyroid
cancer is calculated to be increased to 1.25%
by being exposed to radioiodine, with the
increase being slightly less for males.
The risks from a number of additional radiation-induced
cancers are also expected to be elevated due
to exposure caused by the other low boiling
point fission products that were released
by the safety failures.
The single greatest increase is for thyroid
cancer, but in total, an overall 1% higher
lifetime risk of developing cancers of all
types, is predicted for infant females, with
the risk slightly lower for males, making
both some of the most radiation-sensitive
groups.
The WHO predicted those within the womb, depending
on their gender, would have the same elevations
in risk as the infant groups.A screening program
a year later in 2012 found that more than
a third (36%) of children in Fukushima Prefecture
have abnormal growths in their thyroid glands.
As of August 2013, there have been more than
40 children newly diagnosed with thyroid cancer
and other cancers in Fukushima prefecture
as a whole.
In 2015, the number of thyroid cancers or
detections of developing thyroid cancers numbered
137.
However, whether these incidences of cancer
are elevated above the rate in un-contaminated
areas and therefore were due to exposure to
nuclear radiation is unknown at this stage.
Data from the Chernobyl accident showed that
an unmistakable rise in thyroid cancer rates
following the disaster in 1986 only began
after a cancer incubation period of 3–5
years; however, whether this data can be directly
compared to the Fukushima nuclear disaster
is yet to be determined.On 5 July 2012, the
Japanese National Diet-appointed Fukushima
Nuclear Accident Independent Investigation
Commission (NAIIC) submitted its inquiry report
to the Japanese Diet.
The Commission found the nuclear disaster
was "manmade", that the direct causes of the
accident were all foreseeable prior to 11
March 2011.
The report also found that the Fukushima Daiichi
Nuclear Power Plant was incapable of withstanding
the earthquake and tsunami.
TEPCO, the regulatory bodies (NISA and NSC)
and the government body promoting the nuclear
power industry (METI), all failed to correctly
develop the most basic safety requirements
– such as assessing the probability of damage,
preparing for containing collateral damage
from such a disaster, and developing evacuation
plans for the public in the case of a serious
radiation release.
Meanwhile, the government-appointed Investigation
Committee on the Accident at the Fukushima
Nuclear Power Stations of Tokyo Electric Power
Company submitted its final report to the
Japanese government on 23 July 2012.
A separate study by Stanford researchers found
that Japanese plants operated by the largest
utility companies were particularly unprotected
against potential tsunami.TEPCO admitted for
the first time on 12 October 2012 that it
had failed to take stronger measures to prevent
disasters for fear of inviting lawsuits or
protests against its nuclear plants.
There are no clear plans for decommissioning
the plant, but the plant management estimate
is thirty or forty years.A frozen soil barrier
was constructed in an attempt to prevent further
contamination of seeping groundwater by melted-down
nuclear fuel, but in July 2016 TEPCO revealed
that the ice wall had failed to stop groundwater
from flowing in and mixing with highly radioactive
water inside the wrecked reactor buildings,
adding that "its ultimate goal has been to
'curtail' groundwater inflow, not halt it".
By 2019, the ice wall had reduced the inflow
of groundwater from 440 cubic meters per day
in 2014 to 100 cubic meters per day, while
contaminated water generation decreased to
170 cubic meters per day from 540 cubic meters
per day in 2014.In 2018, tours to visit the
Fukushima disaster area began.
== Plant description ==
The Fukushima Daiichi Nuclear Power Plant
consisted of six GE light water boiling water
reactors (BWRs) with a combined power of 4.7
gigawatts, making it one of the world's 25
largest nuclear power stations.
It was the first GE-designed nuclear plant
to be constructed and run entirely by the
Tokyo Electric Power Company (TEPCO).
Reactor 1 was a 439 MWe type (BWR-3) reactor
constructed in July 1967, and commenced operation
on 26 March 1971.
It was designed to withstand an earthquake
with a peak ground acceleration of 0.18 g
(1.4 m/s2, 4.6 ft/s2) and a response spectrum
based on the 1952 Kern County earthquake.
Reactors 2 and 3 were both 784 MWe type BWR-4s.
Reactor 2 commenced operation in July 1974,
and Reactor 3 in March 1976.
The earthquake design basis for all units
ranged from 0.42 g (4.12 m/s2, 13.5 ft/s2)
to 0.46 g (4.52 m/s2, 14.8 ft/s2).
After the 1978 Miyagi earthquake, when the
ground acceleration reached 0.125 g (1.22
m/s2, 4.0 ft/s2) for 30 seconds, no damage
to the critical parts of the reactor was found.
Units 1–5 have a Mark-1 type (light bulb
torus) containment structure; unit 6 has Mark
2-type (over/under) containment structure.
In September 2010, Reactor 3 was partially
fueled by mixed-oxides (MOX).At the time of
the accident, the units and central storage
facility contained the following numbers of
fuel assemblies:
There was no MOX fuel in any of the cooling
ponds at the time of the incident.
The only MOX fuel was currently loaded in
the Unit 3 reactor.
=== Cooling ===
Nuclear reactors generate electricity by using
the heat of the fission reaction to produce
steam, which drives turbines that generate
electricity.
When the reactor stops operating, the radioactive
decay of unstable isotopes in the fuel continues
to generate heat (decay heat) for a time,
and so requires continued cooling.
This decay heat amounts to approximately 6.5%
of the amount produced by fission at first,
then decreases over several days before reaching
shutdown levels.
Afterwards, spent fuel rods typically require
several years in a spent fuel pool before
they can be safely transferred to dry cask
storage vessels.
The decay heat in the Unit 4 spent fuel pool
had the capacity to boil about 70 metric tons
(69 long tons; 77 short tons) of water per
day.In the reactor core, high-pressure systems
cycle water between the reactor pressure vessel
and heat exchangers.
These systems transfer heat to a secondary
heat exchanger via the essential service water
system, using water pumped out to sea or an
onsite cooling tower.
Units 2 and 3 had steam turbine-driven emergency
core cooling systems that could be directly
operated by steam produced by decay heat and
that could inject water directly into the
reactor.
Some electrical power was needed to operate
valves and monitoring systems.
Unit 1 had a different, entirely passive cooling
system, the Isolation Condenser (IC).
It consisted of a series of pipes run from
the reactor core to the inside of a large
tank of water.
When the valves were opened, steam flowed
upward to the IC, where the cool water in
the tank condenses the steam back to water
that runs under gravity back to the reactor
core.
For unknown reasons, Unit 1's IC was operated
only intermittently during the emergency.
However, during a 25 March 2014 presentation
to the TVA, Dr Takeyuki Inagaki explained
that the IC was being operated intermittently
to maintain reactor vessel level and to prevent
the core from cooling too quickly, which can
increase reactor power.
As the tsunami engulfed the station, the IC
valves were closed and could not be reopened
automatically due to the loss of electrical
power, but could have been opened manually.
On 16 April 2011, TEPCO declared that cooling
systems for Units 1–4 were beyond repair.
=== Backup generators ===
When a reactor is not producing electricity,
its cooling pumps can be powered by other
reactor units, the grid, diesel generators,
or batteries.Two emergency diesel generators
were available for each of Units 1–5 and
three for Unit 6.In the late 1990s, three
additional backup generators for Units 2 and
4 were placed in new buildings located higher
on the hillside, to comply with new regulatory
requirements.
All six units were given access to these generators,
but the switching stations that sent power
from these backup generators to the reactors'
cooling systems for Units 1 through 5 were
still in the poorly protected turbine buildings.
The switching station for Unit 6 was protected
inside the only GE Mark II reactor building
and continued to function.
All three of the generators added in the late
1990s were operational after the tsunami.
If the switching stations had been moved to
inside the reactor buildings or to other flood-proof
locations, power would have been provided
by these generators to the reactors' cooling
systems.The reactor's emergency diesel generators
and DC batteries, crucial components in powering
cooling systems after a power loss, were located
in the basements of the reactor turbine buildings,
in accordance with GE's specifications.
Mid-level GE engineers expressed concerns,
relayed to Tepco, that this left them vulnerable
to flooding.The Fukushima reactors were not
designed for such a large tsunami, nor had
the reactors been modified when concerns were
raised in Japan and by the IAEA.Fukushima
II was also struck by the tsunami.
However, it had incorporated design changes
that improved its resistance to flooding,
reducing flood damage.
Generators and related electrical distribution
equipment were located in the watertight reactor
building, so that power from the electricity
grid was being used by midnight.
Seawater pumps for cooling were protected
from flooding, and although 3 of 4 initially
failed, they were restored to operation.
=== Central fuel storage areas ===
Used fuel assemblies taken from reactors are
initially stored for at least 18 months in
the pools adjacent to their reactors.
They can then be transferred to the central
fuel storage pond.
Fukushima I's storage area contains 6375 fuel
assemblies.
After further cooling, fuel can be transferred
to dry cask storage, which has shown no signs
of abnormalities.
=== Zircaloy ===
Many of the internal components and fuel assembly
cladding are made from zircaloy because it
does not absorb neutrons.
At normal operating temperatures of approximately
300 °C (572 °F), zircaloy is inert.
However, above 1,200 degrees Celsius (2,190
°F), zirconium metal can react exothermically
with water to form free hydrogen gas.
The reaction between zirconium and the coolant
produces more heat, accelerating the reaction.
In addition, zircaloy can react with uranium
dioxide to form zirconium dioxide and uranium
metal.
This exothermic reaction together with the
reaction of boron carbide with stainless steel
can release additional heat energy, thus contributing
to the overheating of a reactor.
== Prior safety concerns ==
=== 1967: Layout of the emergency-cooling
system ===
In 1967 when the plant was built TEPCO levelled
the sea coast to make it easier to bring in
equipment.
This put the new plant at 10 meters (33 ft)
above sea level, rather than the original
30 meters (98 ft).On 27 February 2012, the
Nuclear and Industrial Safety Agency ordered
TEPCO to report its reasoning for changing
the piping layout for the emergency cooling
system.
The original plans separated the piping systems
for two reactors in the isolation condenser
from each other.
However, the application for approval of the
construction plan showed the two piping systems
connected outside the reactor.
The changes were not noted, in violation of
regulations.After the tsunami, the isolation
condenser should have taken over the function
of the cooling pumps, by condensing the steam
from the pressure vessel into water to be
used for cooling the reactor.
However, the condenser did not function properly
and TEPCO could not confirm whether a valve
was opened.
=== 1991: Backup generator of Reactor 1 flooded
===
On 30 October 1991, one of two backup generators
of Reactor 1 failed, after flooding in the
reactor's basement.
Seawater used for cooling leaked into the
turbine building from a corroded pipe at 20
cubic meters per hour, as reported by former
employees in December 2011.
An engineer was quoted as saying that he informed
his superiors of the possibility that a tsunami
could damage the generators.
TEPCO installed doors to prevent water from
leaking into the generator rooms.
The Japanese Nuclear Safety Commission stated
that it would revise its safety guidelines
and would require the installation of additional
power sources.
On 29 December 2011, TEPCO admitted all these
facts: its report mentioned that the room
was flooded through a door and some holes
for cables, but the power supply was not cut
off by the flooding, and the reactor was stopped
for one day.
One of the two power sources was completely
submerged, but its drive mechanism had remained
unaffected.
=== 2000: Tsunami study ignored ===
An in-house TEPCO report in 2000 recommended
safety measures against seawater flooding,
based on the potential of a 50-foot tsunami.
TEPCO leadership said the study's technological
validity "could not be verified."
After the tsunami a TEPCO report said that
the risks discussed in the 2000 report had
not been announced because "announcing information
about uncertain risks would create anxiety."
=== 2008: Tsunami study ignored ===
In 2007, TEPCO set up a department to supervise
its nuclear facilities.
Until June 2011, its chairman was Masao Yoshida,
the Fukushima Daiichi chief.
A 2008 in-house study identified an immediate
need to better protect the facility from flooding
by seawater.
This study mentioned the possibility of tsunami-waves
up to 10.2 meters (33 ft).
Headquarters officials insisted that such
a risk was unrealistic and did not take the
prediction seriously.Dr Yukinobu Okamura of
the Active Fault and Earthquake Research Center
(replaced in 2014 by Research Institute of
Earthquake and Volcano Geology (IEVG), Geological
Survey of Japan (GSJ), AIST) urged TEPCO and
NISA to revise their assumptions for possible
tsunami heights upwards, based on his team's
findings about the 869 Sanriku earthquake,
but this was not seriously considered at the
time.The U.S. Nuclear Regulatory Commission
warned of a risk of losing emergency power
in 1991 (NUREG-1150) and NISA referred to
that report in 2004, but took no action to
mitigate the risk.Warnings by government committees,
such as one in the Cabinet Office in 2004,
that tsunamis taller than the maximum of 5.6
meters (18 ft) forecast by TEPCO and government
officials were possible, were also ignored.
=== Vulnerability to earthquakes ===
Japan, like the rest of the Pacific Rim, is
in an active seismic zone, prone to earthquakes.
A seismologist named Katsuhiko Ishibashi wrote
a 1994 book titled A Seismologist Warns criticizing
lax building codes, which became a best seller
when an earthquake in Kobe killed thousands
shortly after its publication.
In 1997 he coined the term "nuclear earthquake
disaster", and in 1995 wrote an article for
the International Herald Tribune warning of
a cascade of events much like the Fukushima
disaster.The International Atomic Energy Agency
(IAEA) had expressed concern about the ability
of Japan's nuclear plants to withstand earthquakes.
At a 2008 meeting of the G8's Nuclear Safety
and Security Group in Tokyo, an IAEA expert
warned that a strong earthquake with a magnitude
above 7.0 could pose a "serious problem" for
Japan's nuclear power stations.
The region had experienced three earthquakes
of magnitude greater than 8, including the
869 Sanriku earthquake, the 1896 Sanriku earthquake,
and the 1933 Sanriku earthquake.
== Events ==
=== Tōhoku earthquake ===
The 9.0 MW Tōhoku earthquake occurred at
14:46 on Friday, 11 March 2011, with the epicenter
near Honshu, the largest island of Japan.
It produced maximum ground g-forces of 0.56,
0.52, 0.56 (5.50, 5.07 and 5.48 m/s2, 18.0,
16.6 and 18.0 ft/s2) at units 2, 3, and 5
respectively.
This exceeded the earthquake reactor design
tolerances of 0.45, 0.45, and 0.46 g (4.38,
4.41 and 4.52 m/s2, 14.4, 14.5 and 14.8 ft/s2).
The shock values were within the design tolerances
at units 1, 4, and 6.When the earthquake struck,
units 1, 2, and 3 were operating, but units
4, 5, and 6 had been shut down for a scheduled
inspection.
Reactors 1, 2, and 3 immediately shut down
automatically; this meant the plant stopped
generating electricity and could no longer
use its own power.
One of the two connections to off-site power
for units 1–3 also failed, so 13 on-site
emergency diesel generators began providing
power.
=== Tsunami and flooding ===
The earthquake triggered a 13-to-15-meter
(43 to 49 ft)-high tsunami that arrived approximately
50 minutes later.
The waves overtopped the plant's 5.7-meter
(19 ft) seawall, flooding the basements of
the power plant's turbine buildings and disabling
the emergency diesel generators at approximately
15:41.
TEPCO then notified authorities of a "first-level
emergency".
The switching stations that provided power
from the three backup generators located higher
on the hillside failed when the building that
housed them flooded.
Power for the plant's control systems switched
to batteries designed to provide power for
about eight hours.
Further batteries and mobile generators were
dispatched to the site, but were delayed by
poor road conditions; the first arrived at
21:00 11 March, almost six hours after the
tsunami struck.
Unsuccessful attempts were made to connect
portable generating equipment to power water
pumps.
The failure was attributed to flooding at
the connection point in the Turbine Hall basement
and the absence of suitable cables.
TEPCO switched its efforts to installing new
lines from the grid.
One generator at unit 6 resumed operation
on 17 March, while external power returned
to units 5 and 6 only on March 20.
=== Evacuation ===
The government initially set in place a four-stage
evacuation process: a prohibited access area
out to 3 km (1.9 mi), an on-alert area 3–20
km (1.9–12.4 mi) and an evacuation prepared
area 20–30 km (12–19 mi).
On day one, an estimated 170,000 people were
evacuated from the prohibited access and on-alert
areas.
Prime Minister Kan instructed people within
the on-alert area to leave and urged those
in the prepared area to stay indoors.
The latter groups were urged to evacuate on
25 March.
The 20 km (12 mi) exclusion zone was guarded
by roadblocks to ensure that fewer people
would be affected by the radiation.
During the evacuation of hospitals and nursing
homes, 51 patients and elderly people died.The
earthquake and tsunami damaged or destroyed
more than one million buildings leading to
a total of 470,000 people needing evacuation.
Of the 470,000, the nuclear accident was responsible
for 154,000 being evacuated.
=== Hydrogen explosions ===
In Reactors 1, 2, and 3, overheating caused
a reaction between the water and the zircaloy,
creating hydrogen gas.
On 12 March, leaking hydrogen mixed with oxygen
exploded in Unit 1, destroying the upper part
of the building and injuring five people.
On 14 March, a similar explosion occurred
in the Reactor 3 building, blowing off the
roof and injuring eleven people.
On the 15th, there was an explosion in the
Reactor 4 building due to a shared vent pipe
with Reactor 3.
=== Core meltdowns in units 1, 2, and 3 ===
The amount of damage sustained by the reactor
cores during the accident, and the location
of molten nuclear fuel ("corium") within the
containment buildings, is unknown; TEPCO has
revised its estimates several times.
On 16 March 2011, TEPCO estimated that 70%
of the fuel in Unit 1 had melted and 33% in
Unit 2, and that Unit 3's core might also
be damaged.
As of 2015 it can be assumed that most fuel
melted through the reactor pressure vessel
(RPV), commonly known as the "reactor core",
and is resting on the bottom of the primary
containment vessel (PCV), having been stopped
by the PCV concrete.
In July 2017 a remotely controlled robot filmed
for the first time apparently melted fuel,
just below the reactor pressure vessel of
Unit 3.TEPCO released further estimates of
the state and location of the fuel in a November
2011 report.
The report concluded that the Unit 1 RPV was
damaged during the disaster and that "significant
amounts" of molten fuel had fallen into the
bottom of the PCV.
The erosion of the concrete of the PCV by
the molten fuel after the core meltdown was
estimated to stop at approx.
0.7 meters (2 ft 4 in) in depth, while the
thickness of the containment is 7.6 meters
(25 ft) thick.
Gas sampling carried out before the report
detected no signs of an ongoing reaction of
the fuel with the concrete of the PCV and
all the fuel in Unit 1 was estimated to be
"well cooled down, including the fuel dropped
on the bottom of the reactor".
Fuel in Units 2 and 3 had melted, however
less than in Unit 1, and fuel was presumed
to be still in the RPV, with no significant
amounts of fuel fallen to the bottom of the
PCV.
The report further suggested that "there is
a range in the evaluation results" from "all
fuel in the RPV (none fuel fallen to the PCV)"
in Unit 2 and Unit 3, to "most fuel in the
RPV (some fuel in PCV)".
For Unit 2 and Unit 3 it was estimated that
the "fuel is cooled sufficiently".
According to the report, the greater damage
in Unit 1 (when compared to the other two
units) was due to the longer time that no
cooling water was injected in Unit 1.
This resulted in much more decay heat accumulating,
as for about 1 day there was no water injection
for Unit 1, while Unit 2 and Unit 3 had only
a quarter of a day without water injection.In
November 2013, Mari Yamaguchi reported for
Associated Press that there are computer simulations
which suggest that "the melted fuel in Unit
1, whose core damage was the most extensive,
has breached the bottom of the primary containment
vessel and even partially eaten into its concrete
foundation, coming within about 30 centimeters
(1 ft) of leaking into the ground" – a Kyoto
University nuclear engineer said with regards
to these estimates: "We just can't be sure
until we actually see the inside of the reactors."According
to a December 2013 report, TEPCO estimated
for Unit 1 that "the decay heat must have
decreased enough, the molten fuel can be assumed
to remain in PCV (primary containment vessel)".In
August 2014, TEPCO released a new revised
estimate that Reactor 3 had a complete melt
through in the initial phase of the accident.
According to this new estimate within the
first three days of the accident the entire
core content of Reactor 3 had melted through
the RPV and fallen to the bottom of the PCV.
These estimates were based on a simulation,
which indicated that Reactor 3's melted core
penetrated through 1.2 meters (3 ft 11 in)
of the PCV's concrete base, and came close
to 26–68 centimeters (10–27 in) of the
PCV's steel wall.In February 2015, TEPCO started
the muon scanning process for Units 1, 2,
and 3.
With this scanning setup it will be possible
to determine the approximate amount and location
of the remaining nuclear fuel within the RPV,
but not the amount and resting place of the
corium in the PCV.
In March 2015 TEPCO released the result of
the muon scan for Unit 1 which showed that
no fuel was visible in the RPV, which would
suggest that most if not all of the molten
fuel had dropped onto the bottom of the PCV
– this will change the plan for the removal
of the fuel from Unit 1.In February 2017,
six years after the disaster, radiation levels
inside the Unit 2 containment building were
crudely estimated to be about 650 Sv/h.
The estimation was revised later to 80 Sv/h.
These readings were the highest recorded since
the disaster occurred in 2011 and the first
recorded in that area of the reactor since
the meltdowns.
Images showed a hole in metal grating beneath
the reactor pressure vessel, suggesting that
melted nuclear fuel had escaped the vessel
in that area.In February 2017, TEPCO released
images taken inside Reactor 2 by a remote-controlled
camera that show a 2-meter (6.5 ft) wide hole
in the metal grating under the pressure vessel
in the reactor's primary containment vessel,
which could have been caused by fuel escaping
the pressure vessel, indicating a meltdown/melt-through
had occurred, through this layer of containment.
Ionizing radiation levels of about 210 sieverts
(Sv) per hour were subsequently detected inside
the Unit 2 containment vessel.
Undamaged spent fuel typically has values
of 270 Sv/h, after ten years of cold shutdown
with no shielding.In January 2018, a remote-controlled
camera confirmed that nuclear fuel debris
was at the bottom of the Unit 2 PCV, showing
fuel had escaped the RPV.
The handle from the top of a nuclear fuel
assembly was also observed, confirming that
a considerable amount of the nuclear fuel
had melted.
=== Damage to unit 4 ===
Reactor 4 was not operating when the earthquake
struck.
All fuel rods from Unit 4 had been transferred
to the spent fuel pool on an upper floor of
the reactor building prior to the tsunami.
On 15 March, an explosion damaged the fourth
floor rooftop area of Unit 4, creating two
large holes in a wall of the outer building.
It was reported that water in the spent fuel
pool might be boiling.
Radiation inside the Unit 4 control room prevented
workers from staying there for long periods.
Visual inspection of the spent fuel pool on
30 April revealed no significant damage to
the rods.
A radiochemical examination of the pond water
confirmed that little of the fuel had been
damaged.In October 2012, the former Japanese
Ambassador to Switzerland and Senegal, Mitsuhei
Murata, said that the ground under Fukushima
Unit 4 was sinking, and the structure may
collapse.In November 2013, TEPCO began moving
the 1533 fuel rods in the Unit 4 cooling pool
to the central pool.
This process was completed on 22 December
2014.
=== Units 5 and 6 ===
Reactors 5 and 6 were also not operating when
the earthquake struck.
Unlike Reactor 4, their fuel rods remained
in the reactor.
The reactors had been closely monitored, as
cooling processes were not functioning well.
Both Unit 5 and Unit 6 shared a working generator
and switchgear during the emergency and achieved
a successful cold shutdown nine days later
on 20 March.
=== Central fuel storage areas ===
On 21 March, temperatures in the fuel pond
had risen slightly, to 61 °C (142 °F) and
water was sprayed over the pool.
Power was restored to cooling systems on 24
March and by 28 March, temperatures were reported
down to 35 °C (95 °F).
=== Radioactive contamination ===
Sub article: Comparison of Fukushima and Chernobyl
nuclear accidents with detailed tables inside
Radioactive material was released from the
containment vessels for several reasons: deliberate
venting to reduce gas pressure, deliberate
discharge of coolant water into the sea, and
uncontrolled events.
Concerns about the possibility of a large
scale release led to a 20-kilometer (12 mi)
exclusion zone around the power plant and
recommendations that people within the surrounding
20–30 km (12–19 mi) zone stay indoors.
Later, the UK, France, and some other countries
told their nationals to consider leaving Tokyo,
in response to fears of spreading contamination.
In 2015, the tap water contamination was still
higher in Tokyo compared to other cities in
Japan.
Trace amounts of radioactivity, including
iodine-131, caesium-134, and caesium-137,
were widely observed.Between 21 March and
mid-July, around 27 PBq of caesium-137 (about
8.4 kg or 19 lb) entered the ocean, with about
82 percent having flowed into the sea before
8 April.
However, the Fukushima coast has some of the
world's strongest currents and these transported
the contaminated waters far into the Pacific
Ocean, thus causing great dispersion of the
radioactive elements.
The results of measurements of both the seawater
and the coastal sediments led to the supposition
that the consequences of the accident, in
terms of radioactivity, would be minor for
marine life as of autumn 2011 (weak concentration
of radioactivity in the water and limited
accumulation in sediments).
On the other hand, significant pollution of
sea water along the coast near the nuclear
plant might persist, due to the continuing
arrival of radioactive material transported
towards the sea by surface water running over
contaminated soil.
Organisms that filter water and fish at the
top of the food chain are, over time, the
most sensitive to caesium pollution.
It is thus justified to maintain surveillance
of marine life that is fished in the coastal
waters off Fukushima.
Despite caesium isotopic concentrations in
the waters off of Japan being 10 to 1000 times
above the normal concentrations prior to the
accident, radiation risks are below what is
generally considered harmful to marine animals
and human consumers.Researchers at the University
of Tokyo's Underwater Technology Research
Center towed detectors behind boats to map
hot spots on the ocean floor off Fukushima.
Blair Thornton, an associate professor the
university, said in 2013 that radiation levels
remained hundreds of times as high as in other
areas of the sea floor, suggesting ongoing
contamination (at the time) from the plant.A
monitoring system operated by the Preparatory
Commission for the Comprehensive Nuclear-Test-Ban
Treaty Organization (CTBTO) tracked the spread
of radioactivity on a global scale.
Radioactive isotopes were picked up by over
40 monitoring stations.On 12 March, radioactive
releases first reached a CTBTO monitoring
station in Takasaki, Japan, around 200 km
(120 mi) away.
The radioactive isotopes appeared in eastern
Russia on 14 March and the west coast of the
United States two days later.
By day 15, traces of radioactivity were detectable
all across the northern hemisphere.
Within one month, radioactive particles were
noted by CTBTO stations in the southern hemisphere.Estimates
of radioactivity released ranged from 10–40%
of that of Chernobyl.
The significantly contaminated area was 10-12%
of that of Chernobyl.In March 2011, Japanese
officials announced that "radioactive iodine-131
exceeding safety limits for infants had been
detected at 18 water-purification plants in
Tokyo and five other prefectures".
On 21 March, the first restrictions were placed
on the distribution and consumption of contaminated
items.
As of July 2011, the Japanese government was
unable to control the spread of radioactive
material into the nation's food supply.
Radioactive material was detected in food
produced in 2011, including spinach, tea leaves,
milk, fish, and beef, up to 320 kilometres
from the plant.
2012 crops did not show signs of radioactivity
contamination.
Cabbage, rice and beef showed insignificant
levels of radioactivity.
A Fukushima-produced rice market in Tokyo
was accepted by consumers as safe.On 24 August
2011, the Nuclear Safety Commission (NSC)
of Japan published the results of its recalculation
of the total amount of radioactive materials
released into the air during the accident
at the Fukushima Daiichi Nuclear Power Station.
The total amounts released between 11 March
and 5 April were revised downwards to 130
PBq (petabecquerels, 3.5 megacuries) for iodine-131
and 11 PBq for caesium-137, which is about
11% of Chernobyl emissions.
Earlier estimations were 150 PBq and 12 PBq.In
2011, scientists working for the Japan Atomic
Energy Agency, Kyoto University and other
institutes, recalculated the amount of radioactive
material released into the ocean: between
late March through April they found a total
of 15 PBq for the combined amount of iodine-131
and caesium-137, more than triple the 4.72
PBq estimated by TEPCO.
The company had calculated only the direct
releases into the sea.
The new calculations incorporated the portion
of airborne radioactive substances that entered
the ocean as rain.In the first half of September
2011, TEPCO estimated the radioactivity release
at some 200 MBq (megabecquerels, 5.4 millicuries)
per hour.
This was approximately one four-millionth
that of March.
Traces of iodine-131 were detected in several
Japanese prefectures in November and December
2011.According to the French Institute for
Radiological Protection and Nuclear Safety,
between 21 March and mid-July around 27 PBq
of caesium-137 entered the ocean, about 82
percent before 8 April.
This emission represents the most important
individual oceanic emissions of artificial
radioactivity ever observed.
The Fukushima coast has one of the world's
strongest currents (Kuroshio Current).
It transported the contaminated waters far
into the Pacific Ocean, dispersing the radioactivity.
As of late 2011 measurements of both the seawater
and the coastal sediments suggested that the
consequences for marine life would be minor.
Significant pollution along the coast near
the plant might persist, because of the continuing
arrival of radioactive material transported
to the sea by surface water crossing contaminated
soil.
The possible presence of other radioactive
substances, such as strontium-90 or plutonium,
has not been sufficiently studied.
Recent measurements show persistent contamination
of some marine species (mostly fish) caught
along the Fukushima coast.Migratory pelagic
species are highly effective and rapid transporters
of radioactivity throughout the ocean.
Elevated levels of caesium-134 appeared in
migratory species off the coast of California
that were not seen pre-Fukushima.
Scientists have also discovered increased
traces of radioactive isotope Caesium-137
in wine grown in a vineyard in Napa Valley,
California.
The trace-level radioactivity was in dust
blown across the Pacific Ocean.As of March
2012, no cases of radiation-related ailments
had been reported.
Experts cautioned that data was insufficient
to allow conclusions on health impacts.
Michiaki Kai, professor of radiation protection
at Oita University of Nursing and Health Sciences,
stated, "If the current radiation dose estimates
are correct, (cancer-related deaths) likely
won't increase."In May 2012, TEPCO released
their estimate of cumulative radioactivity
releases.
An estimated 538.1 PBq of iodine-131, caesium-134
and caesium-137 was released.
520 PBq was released into the atmosphere between
12–31 March 2011 and 18.1 PBq into the ocean
from 26 March – 30 September 2011.
A total of 511 PBq of iodine-131 was released
into both the atmosphere and the ocean, 13.5
PBq of caesium-134 and 13.6 PBq of caesium-137.
TEPCO reported that at least 900 PBq had been
released "into the atmosphere in March last
year [2011] alone".In 2012 researchers from
the Institute of Problems in the Safe Development
of Nuclear Energy, Russian Academy of Sciences,
and the Hydrometeorological Center of Russia
concluded that "on March 15, 2011, ~400 PBq
iodine, ~100 PBq caesium, and ~400 PBq inert
gases entered the atmosphere" on that day
alone.In August 2012, researchers found that
10,000 nearby residents had been exposed to
less than 1 millisievert of radiation, significantly
less than Chernobyl residents.As of October
2012, radioactivity was still leaking into
the ocean.
Fishing in the waters around the site was
still prohibited, and the levels of radioactive
134Cs and 137Cs in the fish caught were not
lower than immediately after the disaster.On
26 October 2012, TEPCO admitted that it could
not stop radioactive material entering the
ocean, although emission rates had stabilized.
Undetected leaks could not be ruled out, because
the reactor basements remained flooded.
The company was building a 2,400-foot-long
steel and concrete wall between the site and
the ocean, reaching 30 meters (98 ft) below
ground, but it would not be finished before
mid-2014.
Around August 2012 two greenling were caught
close to shore.
They contained more than 25,000 becquerels
(0.67 millicuries) of caesium-137 per kilogram
(11,000 Bq/lb; 0.31 μCi/lb), the highest
measured since the disaster and 250 times
the government's safety limit.On 22 July 2013,
it was revealed by TEPCO that the plant continued
to leak radioactive water into the Pacific
Ocean, something long suspected by local fishermen
and independent investigators.
TEPCO had previously denied that this was
happening.
Japanese Prime Minister Shinzō Abe ordered
the government to step in.On 20 August, in
a further incident, it was announced that
300 metric tons (300 long tons; 330 short
tons) of heavily contaminated water had leaked
from a storage tank, approximately the same
amount of water as one eighth (1/8) of that
found in an Olympic-size swimming pool.
The 300 metric tons (300 long tons; 330 short
tons) of water was radioactive enough to be
hazardous to nearby staff, and the leak was
assessed as Level 3 on the International Nuclear
Event Scale.On 26 August, the government took
charge of emergency measures to prevent further
radioactive water leaks, reflecting their
lack of confidence in TEPCO.As of 2013, about
400 metric tons (390 long tons; 440 short
tons) of water per day of cooling water was
being pumped into the reactors.
Another 400 metric tons (390 long tons; 440
short tons) of groundwater was seeping into
the structure.
Some 800 metric tons (790 long tons; 880 short
tons) of water per day was removed for treatment,
half of which was reused for cooling and half
diverted to storage tanks.
Ultimately the contaminated water, after treatment
to remove radionuclides other than tritium,
may have to be dumped into the Pacific.
TEPCO decided to create an underground ice
wall to block the flow of groundwater into
the reactor buildings.
A $300 million 7.8 MW cooling facility freezes
the ground to a depth of 30 meter.
As of 2019, the contaminated water generation
had been reduced to 170 metric tons (170 long
tons; 190 short tons) per day.In February
2014, NHK reported that TEPCO was reviewing
its radioactivity data, after finding much
higher levels of radioactivity than was reported
earlier.
TEPCO now says that levels of 5 MBq (0.12
millicuries) of strontium per liter (23 MBq/imp
gal; 19 MBq/U.S. gal; 610 μCi/imp gal; 510
μCi/U.S. gal) were detected in groundwater
collected in July 2013 and not the 900 kBq
(0.02 millicuries) (4.1 MBq/imp gal; 3.4 MBq/U.S.
gal; 110 μCi/imp gal; 92 μCi/U.S. gal) that
were initially reported.On 10 September 2015,
floodwaters driven by Typhoon Etau prompted
mass evacuations in Japan and overwhelmed
the drainage pumps at the stricken Fukushima
nuclear plant.
A TEPCO spokesperson said that hundreds of
metric tons of radioactive water entered the
ocean as a result.
Plastic bags filled with contaminated soil
and grass were also swept away by the flood
waters.
==== Contamination in the eastern Pacific
====
In March 2014, numerous news sources, including
NBC, began predicting that the radioactive
underwater plume traveling through the Pacific
Ocean would reach the western seaboard of
the continental United States.
The common story was that the amount of radioactivity
would be harmless and temporary once it arrived.
The National Oceanic and Atmospheric Administration
measured caesium-134 at points in the Pacific
Ocean and models were cited in predictions
by several government agencies to announce
that the radiation would not be a health hazard
for North American residents.
Groups, including Beyond Nuclear and the Tillamook
Estuaries Partnership, challenged these predictions
on the basis of continued isotope releases
after 2011, leading to a demand for more recent
and comprehensive measurements as the radioactivity
made its way east.
These measurements were taken by a cooperative
group of organizations under the guidance
of a marine chemist with the Woods Hole Oceanographic
Institution, and revealed that total radiation
levels, of which only a fraction bore the
fingerprint of Fukushima, were not high enough
to pose any direct risk to human life and
in fact were far less than Environmental Protection
Agency guidelines or several other sources
of radiation exposure deemed safe.
Integrated Fukushima Ocean Radionuclide Monitoring
project (InFORM) also failed to show any significant
amount of radiation and as a result its authors
received death threats from supporters of
a Fukushima-induced "wave of cancer deaths
across North America" theory.
== Response ==
Government agencies and TEPCO were unprepared
for the "cascading nuclear disaster".
The tsunami that "began the nuclear disaster
could and should have been anticipated and
that ambiguity about the roles of public and
private institutions in such a crisis was
a factor in the poor response at Fukushima".
In March 2012, Prime Minister Yoshihiko Noda
said that the government shared the blame
for the Fukushima disaster, saying that officials
had been blinded by a false belief in the
country's "technological infallibility", and
were taken in by a "safety myth".
Noda said "Everybody must share the pain of
responsibility."According to Naoto Kan, Japan's
prime minister during the tsunami, the country
was unprepared for the disaster, and nuclear
power plants should not have been built so
close to the ocean.
Kan acknowledged flaws in authorities' handling
of the crisis, including poor communication
and coordination between nuclear regulators,
utility officials, and the government.
He said the disaster "laid bare a host of
an even bigger man-made vulnerabilities in
Japan's nuclear industry and regulation, from
inadequate safety guidelines to crisis management,
all of which he said need to be overhauled."Physicist
and environmentalist Amory Lovins said that
Japan's "rigid bureaucratic structures, reluctance
to send bad news upwards, need to save face,
weak development of policy alternatives, eagerness
to preserve nuclear power's public acceptance,
and politically fragile government, along
with TEPCO's very hierarchical management
culture, also contributed to the way the accident
unfolded.
Moreover, the information Japanese people
receive about nuclear energy and its alternatives
has long been tightly controlled by both TEPCO
and the government."
=== Poor communication and delays ===
The Japanese government did not keep records
of key meetings during the crisis.
Data from the SPEEDI network were emailed
to the prefectural government, but not shared
with others.
Emails from NISA to Fukushima, covering 12
March 11:54 PM to 16 March 9 AM and holding
vital information for evacuation and health
advisories, went unread and were deleted.
The data was not used because the disaster
countermeasure office regarded the data as
"useless because the predicted amount of released
radiation is unrealistic."
On 14 March 2011 TEPCO officials were instructed
not to use the phrase "core meltdown" at press
conferences.On the evening of 15 March, Prime
Minister Kan called Seiki Soramoto, who used
to design nuclear plants for Toshiba, to ask
for his help in managing the escalating crisis.
Soramoto formed an impromptu advisory group,
which included his former professor at the
University of Tokyo, Toshiso Kosako, a top
Japanese expert on radiation measurement.
Mr. Kosako, who studied the Soviet response
to the Chernobyl crisis, said he was stunned
at how little the leaders in the prime minister's
office knew about the resources available
to them.
He quickly advised the chief cabinet secretary,
Yukio Edano, to use SPEEDI, which used measurements
of radioactive releases, as well as weather
and topographical data, to predict where radioactive
materials could travel after being released
into the atmosphere.The Investigation Committee
on the Accident at the Fukushima Nuclear Power
Stations of Tokyo Electric Power Company's
interim report stated that Japan's response
was flawed by "poor communication and delays
in releasing data on dangerous radiation leaks
at the facility".
The report blamed Japan's central government
as well as TEPCO, "depicting a scene of harried
officials incapable of making decisions to
stem radiation leaks as the situation at the
coastal plant worsened in the days and weeks
following the disaster".
The report said poor planning worsened the
disaster response, noting that authorities
had "grossly underestimated tsunami risks"
that followed the magnitude 9.0 earthquake.
The 12.1-meter (40 ft) high tsunami that struck
the plant was double the height of the highest
wave predicted by officials.
The erroneous assumption that the plant's
cooling system would function after the tsunami
worsened the disaster.
"Plant workers had no clear instructions on
how to respond to such a disaster, causing
miscommunication, especially when the disaster
destroyed backup generators."In February 2012,
the Rebuild Japan Initiative Foundation described
how Japan's response was hindered by a loss
of trust between the major actors: Prime Minister
Kan, TEPCO's Tokyo headquarters and the plant
manager.
The report said that these conflicts "produced
confused flows of sometimes contradictory
information".
According to the report, Kan delayed the cooling
of the reactors by questioning the choice
of seawater instead of fresh water, accusing
him of micromanaging response efforts and
appointing a small, closed, decision-making
staff.
The report stated that the Japanese government
was slow to accept assistance from U.S. nuclear
experts.A 2012 report in The Economist said:
"The operating company was poorly regulated
and did not know what was going on.
The operators made mistakes.
The representatives of the safety inspectorate
fled.
Some of the equipment failed.
The establishment repeatedly played down the
risks and suppressed information about the
movement of the radioactive plume, so some
people were evacuated from more lightly to
more heavily contaminated places."From 17
to 19 March 2011, US military aircraft measured
radiation within a 45 km (28 mi) radius of
the site.
The data recorded 125 microsieverts per hour
of radiation as far as 25 km (15.5 mi) northwest
of the plant.
The US provided detailed maps to the Japanese
Ministry of Economy, Trade and Industry (METI)
on 18 March and to the Ministry of Education,
Culture, Sports, Science and Technology (MEXT)
two days later, but officials did not act
on the information.The data were not forwarded
to the prime minister's office or the Nuclear
Safety Commission (NSC), nor were they used
to direct the evacuation.
Because a substantial portion of radioactive
materials reached ground to the northwest,
residents evacuated in this direction were
unnecessarily exposed to radiation.
According to NSC chief Tetsuya Yamamoto, "It
was very regrettable that we didn't share
and utilize the information."
Itaru Watanabe, from the Science and Technology
Policy Bureau, blamed the US for not releasing
the data.Data on the dispersal of radioactive
materials were provided to the U.S. forces
by the Japanese Ministry for Science a few
days after 11 March; however, the data was
not shared publicly until the Americans published
their map on 23 March, at which point Japan
published fallout maps compiled from ground
measurements and SPEEDI the same day.
According to Watanabe's testimony before the
Diet, the US military was given access to
the data "to seek support from them" on how
to deal with the nuclear disaster.
Although SPEEDI's effectiveness was limited
by not knowing the amounts released in the
disaster, and thus was considered "unreliable",
it was still able to forecast dispersal routes
and could have been used to help local governments
designate more appropriate evacuation routes.On
19 June 2012, science minister Hirofumi Hirano
stated that his "job was only to measure radiation
levels on land" and that the government would
study whether disclosure could have helped
in the evacuation efforts.On 28 June 2012,
Nuclear and Industrial Safety Agency officials
apologized to mayor Yuko Endo of Kawauchi
Village for NISA having failed to release
the American-produced radiation maps in the
first days after the meltdowns.
All residents of this village were evacuated
after the government designated it a no-entry
zone.
According to a Japanese government panel,
authorities had shown no respect for the lives
and dignity of village people.
One NISA official apologized for the failure
and added that the panel had stressed the
importance of disclosure; however, the mayor
said that the information would have prevented
the evacuation into highly polluted areas,
and that apologies a year too late had no
meaning.In June 2016, it was revealed that
TEPCO officials had been instructed on 14
March 2011 not to describe the reactor damage
using the word "meltdown".
Officials at that time were aware that 25–55%
of the fuel had been damaged, and the threshold
for which the term "meltdown" became appropriate
(5%) had been greatly exceeded.
TEPCO President Naomi Hirose told the media:
"I would say it was a cover-up...
It’s extremely regrettable.”
== 
Event rating ==
The incident was rated 7 on the International
Nuclear Event Scale (INES).
This scale runs from 0, indicating an abnormal
situation with no safety consequences, to
7, indicating an accident causing widespread
contamination with serious health and environmental
effects.
Prior to Fukushima, the Chernobyl disaster
was the only level 7 event on record, while
the Three Mile Island accident was rated as
level 5.
A 2012 analysis of the intermediate and long-lived
radioactivity released found about 10–20%
of that released from the Chernobyl disaster.
Approximately 15 PBq of caesium-137 was released,
compared with approximately 85 PBq of caesium-137
at Chernobyl, indicating the release of 26.5
kilograms (58 lb) of caesium-137.
Unlike Chernobyl, all Japanese reactors were
in concrete containment vessels, which limited
the release of strontium-90, americium-241,
and plutonium, which were among the radioisotopes
released by the earlier incident.Some 500
PBq of iodine-131 were released, compared
to approximately 1,760 PBq at Chernobyl.
Iodine-131 has a half-life of 8.02 days, decaying
into a stable nuclide.
After ten half lives (80.2 days), 99.9% has
decayed to xenon-131, a stable isotope.
== Aftermath ==
Although there were no deaths from radiation
exposure in the immediate aftermath of the
incident, there were a number of (non-radiation
related) deaths during the evacuation of the
nearby population.
=== Risks from ionizing radiation ===
Although people in the incident's worst affected
areas have a slightly higher risk of developing
certain cancers such as leukemia, solid cancers,
thyroid cancer, and breast cancer, very few
cancers would be expected as a result of accumulated
radiation exposures.
Estimated effective doses outside Japan are
considered to be below (or far below) the
levels regarded as very small by the international
radiological protection community.In 2013,
the World Health Organization reported that
area residents who were evacuated were exposed
to so little radiation that radiation-induced
health effects were likely to be below detectable
levels.
The health risks were calculated by applying
conservative assumptions, including the conservative
linear no-threshold model of radiation exposure,
a model that assumes even the smallest amount
of radiation exposure will cause a negative
health effect.
The report indicated that for those infants
in the most affected areas, lifetime cancer
risk would increase by about 1%.
It predicted that populations in the most
contaminated areas faced a 70% higher relative
risk of developing thyroid cancer for females
exposed as infants, and a 7% higher relative
risk of leukemia in males exposed as infants
and a 6% higher relative risk of breast cancer
in females exposed as infants.
One-third of involved emergency workers would
have increased cancer risks.
Cancer risks for fetuses were similar to those
in 1 year old infants.
The estimated cancer risk to children and
adults was lower than it was to infants.
These percentages represent estimated relative
increases over the baseline rates and are
not absolute risks for developing such cancers.
Due to the low baseline rates of thyroid cancer,
even a large relative increase represents
a small absolute increase in risks.
For example, the baseline lifetime risk of
thyroid cancer for females is just three-quarters
of one percent and the additional lifetime
risk estimated in this assessment for a female
infant exposed in the most affected location
is one-half of one percent.
The World Nuclear Association reports that
the radiation exposure to those living in
proximity to Fukushima is expected to be below
10 mSv, over the course of a lifetime.
In comparison, the dosage of background radiation
received over a lifetime is 170 mSv.According
to a linear no-threshold model (LNT model),
the accident would most likely cause 130 cancer
deaths.
However, radiation epidemiologist Roy Shore
countered that estimating health effects from
the LNT model "is not wise because of the
uncertainties."
Darshak Sanghavi noted that to obtain reliable
evidence of the effect of low-level radiation
would require an impractically large number
of patients, Luckey reported that the body's
own repair mechanisms can cope with small
doses of radiation and Aurengo stated that
“The LNT model cannot be used to estimate
the effect of very low doses…”In April
2014, studies confirmed the presence of radioactive
tuna off the coasts of the Pacific U.S. Researchers
carried out tests on 26 albacore tuna caught
prior to the 2011 power plant disaster and
those caught after.
However, the amount of radioactivity is less
than that found naturally in a single banana.
Caesium-137 and caesium-134 have been noted
in Japanese whiting in Tokyo Bay as of 2016.
"Concentration of radiocesium in the Japanese
whiting was one or two orders of magnitude
higher than that in the sea water, and an
order of magnitude lower than that in the
sediment."
They were still within food safety limits.In
June 2016 Tilman Ruff, co-president of the
political advocacy group, the "International
Physicians for the Prevention of Nuclear War"
argues that 174,000 people have been unable
to return to their homes and ecological diversity
has decreased and malformations have been
found in trees, birds, and mammals.
Although physiological abnormalities have
been reported within the vicinity of the accident
zone, the scientific community has largely
rejected any such findings of genetic or mutagenic
damage caused by radiation, instead showing
it can be attributed either to experimental
error or other toxic effects.Five years after
the event, the Department of Agriculture from
the University of Tokyo (which holds many
experimental agricultural research fields
around the affected area) has noted that "the
fallout was found at the surface of anything
exposed to air at the time of the accident.
The main radioactive nuclides are now caesium-137
and caesium-134", but these radioactive compounds
have not dispersed much from the point where
they landed at the time of the explosion,
"which was very difficult to estimate from
our understanding of the chemical behavior
of cesium".In February 2018, Japan renewed
the export of fish caught off Fukushima's
nearshore zone.
According to prefecture officials, no seafood
had been found with radiation levels exceeding
Japan safety standards since April 2015.
In 2018, Thailand was the first country to
receive a shipment of fresh fish from Japan's
Fukushima prefecture.
A group campaigning to help prevent global
warming has demanded the Food and Drug Administration
disclose the name of the importer of fish
from Fukushima and of the Japanese restaurants
in Bangkok serving it.
Srisuwan Janya, chairman of the Stop Global
Warming Association, said the FDA must protect
the rights of consumers by ordering restaurants
serving Fukushima fish to make that information
available to their customers, so they could
decide whether to eat it or not.In July 2018,
a robotic probe has found that radiation levels
remain too high for humans to work inside
one of the reactor buildings.
=== Thyroid screening program ===
The World Health Organization stated that
a 2013 thyroid ultrasound screening program
was, due to the screening effect, likely to
lead to an increase in recorded thyroid cases
due to early detection of non-symptomatic
disease cases.
The overwhelming majority of thyroid growths
are benign growths that will never cause symptoms,
illness, or death, even if nothing is ever
done about the growth.
Autopsy studies on people who died from other
causes show that more than one third of adults
technically have a thyroid growth/cancer.
As a precedent, in 1999 in South Korea, the
introduction of advanced ultrasound thyroid
examinations resulted in an explosion in the
rate of benign thyroid cancers being detected
and needless surgeries occurring.
Despite this, the death rate from thyroid
cancer has remained the same.According to
the Tenth Report of the Fukushima Prefecture
Health Management Survey released in February
2013, more than 40% of children screened around
Fukushima prefecture were diagnosed with thyroid
nodules or cysts.
Ultrasonographic detectable thyroid nodules
and cysts are extremely common and can be
found at a frequency of up to 67% in various
studies.
186 (0.5%) of these had nodules larger than
5.1 mm (0.20 in) and/or cysts larger than
20.1 mm (0.79 in) and underwent further investigation,
while none had thyroid cancer.
A Russia Today report into the matter was
highly misleading.
Fukushima Medical University give the number
of children diagnosed with thyroid cancer,
as of December 2013, as 33 and concluded "it
is unlikely that these cancers were caused
by the exposure from I-131 from the nuclear
power plant accident in March 2011".In October
2015, 137 children from the Fukushima Prefecture
were described as either being diagnosed with
or showing signs of developing thyroid cancer.
The study's lead author Toshihide Tsuda from
Okayama University stated that the increased
detection could not be accounted for by attributing
it to the screening effect.
He described the screening results to be "20
times to 50 times what would be normally expected."
By the end of 2015, the number had increased
to 166 children.However, despite his paper
being widely reported by the media, an undermining
error, according to teams of other epidemiologists
who point out Tsuda's remarks are fatally
wrong, is that Tsuda did an apples and oranges
comparison by comparing the Fukushima surveys,
which uses advanced ultrasound devices that
detect otherwise unnoticeable thyroid growths,
with data from traditional non-advanced clinical
examinations, to arrive at his "20 to 50 times
what would be expected" conclusion.
In the critical words of epidemiologist Richard
Wakeford, “It is inappropriate to compare
the data from the Fukushima screening program
with cancer registry data from the rest of
Japan where there is, in general, no such
large-scale screening,”.
Wakeford's criticism was one of seven other
author's letters that were published criticizing
Tsuda's paper.
According to Takamura, another epidemiologist,
who examined the results of small scale advanced
ultrasound tests on Japanese children not
near Fukushima, "The prevalence of thyroid
cancer [using the same detection technology]
does not differ meaningfully from that in
Fukushima Prefecture,”.In 2016 Ohira et
al. conducted a study cross-comparing thyroid
cancer patients from Fukushima prefecture
evacuees with rates of Thyroid cancer in from
those outside of the evacuation zone.
Ohira et al. found that "The duration between
accident and thyroid examination was not associated
with thyroid cancer prevalence.
There were no significant associations between
individual external doses and prevalence of
thyroid cancer.
External radiation dose was not associated
with thyroid cancer prevalence among Fukushima
children within the first 4 years after the
nuclear accident.."A 2018 publication by Yamashita
et al. also concluded that Thyroid cancer
rate differences can be attributed to the
screening effect.
They noted that the mean age of the patients
at the time of the accident was 10–15 years,
while no cases were found in children from
the ages of 0-5 who would have been most susceptible.
Yamashita et al. thus conclude that "In any
case, the individual prognosis cannot be accurately
determined at the time of FNAC at present.
It is therefore urgent to search not only
for intraoperative and postoperative prognostic
factors but also for predictive prognostic
factors at the FNAC/preoperative stage."A
2019 investigation by Yamamoto et al. evaluated
the first and the second screening rounds
separately as well as combined covering 184
confirmed cancer cases in 1.080 million observed
person years subject to additional radiation
exposure due to the nuclear accidents.
The authors concluded "A significant association
between the external effective dose-rate and
the thyroid cancer detection rate exists:
detection rate ratio (DRR) per μSv/h 1.065
(1.013, 1.119).
Restricting the analysis to the 53 municipalities
that received less than 2 μSv/h, and which
represent 176 of the total 184 cancer cases,
the association appears to be considerably
stronger: DRR per μSv/h 1.555 (1.096, 2.206).
The average radiation dose-rates in the 59
municipalities of the Fukushima prefecture
in June 2011 and the corresponding thyroid
cancer detection rates in the period October
2011 to March 2016 show statistically significant
relationships.
This corroborates previous studies providing
evidence for a causal relation between nuclear
accidents and the subsequent occurrence of
thyroid cancer."Thyroid cancer is one of the
most survivable cancers, with an approximate
94% survival rate after first diagnosis.
That rate increases to a nearly 100% survival
rate if caught early.
==== Chernobyl comparison ====
Radiation deaths at Chernobyl were also statistically
undetectable.
Only 0.1% of the 110,645 Ukrainian cleanup
workers, included in a 20-year study out of
over 500,000 former Soviet clean up workers,
had as of 2012 developed leukemia, although
not all cases resulted from the accident.Data
from Chernobyl showed that there was a steady
but sharp increase in thyroid cancer rates
following the disaster in 1986, but whether
this data can be directly compared to Fukushima
is yet to be determined.Chernobyl thyroid
cancer incidence rates did not begin to increase
above the prior baseline value of about 0.7
cases per 100,000 people per year until 1989
to 1991, 3–5 years after the incident in
both adolescent and child age groups.
The rate reached its highest point so far,
of about 11 cases per 100,000 in the decade
of the 2000s, approximately 14 years after
the accident.
From 1989 to 2005, an excess of 4,000 children
and adolescent cases of thyroid cancer were
observed.
Nine of these had died as of 2005, a 99% survival
rate.
=== Effects on evacuees ===
In the former Soviet Union, many patients
with negligible radioactive exposure after
the Chernobyl disaster displayed extreme anxiety
about radiation exposure.
They developed many psychosomatic problems,
including radiophobia along with an increase
in fatalistic alcoholism.
As Japanese health and radiation specialist
Shunichi Yamashita noted:
We know from Chernobyl that the psychological
consequences are enormous.
Life expectancy of the evacuees dropped from
65 to 58 years – not because of cancer,
but because of depression, alcoholism, and
suicide.
Relocation is not easy, the stress is very
big.
We must not only track those problems, but
also treat them.
Otherwise people will feel they are just guinea
pigs in our research.
A survey by the Iitate local government obtained
responses from approximately 1,743 evacuees
within the evacuation zone.
The survey showed that many residents are
experiencing growing frustration, instability,
and an inability to return to their earlier
lives.
Sixty percent of respondents stated that their
health and the health of their families had
deteriorated after evacuating, while 39.9%
reported feeling more irritated compared to
before the disaster.
Summarizing all responses to questions related
to evacuees' current family status, one-third
of all surveyed families live apart from their
children, while 50.1% live away from other
family members (including elderly parents)
with whom they lived before the disaster.
The survey also showed that 34.7% of the evacuees
have suffered salary cuts of 50% or more since
the outbreak of the nuclear disaster.
A total of 36.8% reported a lack of sleep,
while 17.9% reported smoking or drinking more
than before they evacuated.
Stress often manifests in physical ailments,
including behavioral changes such as poor
dietary choices, lack of exercise, and sleep
deprivation.
Survivors, including some who lost homes,
villages, and family members, were found likely
to face mental health and physical challenges.
Much of the stress came from lack of information
and from relocation.In a 2017 risk analysis,
relying on the metric of potential months
of life lost, it determined that unlike Chernobyl,
"relocation was unjustified for the 160,000
people relocated after Fukushima", when the
potential future deaths from exposure to radiation
around Fukushima, would have been much less,
if the alternative of the shelter in place
protocol had instead been deployed.
=== Radioactivity releases ===
In June 2011, TEPCO stated the amount of contaminated
water in the complex had increased due to
substantial rainfall.
On 13 February 2014, TEPCO reported 37 kBq
(1.0 microcurie) of caesium-134 and 93 kBq
(2.5 microcuries) of caesium-137 were detected
per liter of groundwater sampled from a monitoring
well.
Dust particles gathered 4 km from the reactors
in 2017 included microscopic nodules of melted
core samples encased in cesium.
After decades of exponential decline in ocean
cesium from weapons testing fallout, radioactive
isotopes of cesium in the Sea of Japan increased
after the accident from 1.5 mBq/L to about
2.5 mBq/L and are still rising as of 2018,
while those just off the eastern coast of
Japan are declining.
=== Insurance ===
According to reinsurer Munich Re, the private
insurance industry will not be significantly
affected by the disaster.
Swiss Re similarly stated, "Coverage for nuclear
facilities in Japan excludes earthquake shock,
fire following earthquake and tsunami, for
both physical damage and liability.
Swiss Re believes that the incident at the
Fukushima nuclear power plant is unlikely
to result in a significant direct loss for
the property & casualty insurance industry."
=== Compensation ===
The amount of compensation to be paid by TEPCO
is expected to reach 7 trillion yen.Costs
to Japanese taxpayers are likely to exceed
12 trillion yen ($100 billion).
In December 2016 the government estimated
decontamination, compensation, decommissioning,
and radioactive waste storage costs at 21.5
trillion yen ($187 billion), nearly double
the 2013 estimate.In March 2017, a Japanese
court ruled that negligence by the Japanese
government had led to the Fukushima disaster
by failing to use its regulatory powers to
force TEPCO to take preventive measures.
The Maebashi district court near Tokyo awarded
¥39 million (US$345,000) to 137 people who
were forced to flee their homes following
the accident.
=== Energy policy implications ===
By March 2012, one year after the disaster,
all but two of Japan's nuclear reactors had
been shut down; some had been damaged by the
quake and tsunami.
Authority to restart the others after scheduled
maintenance throughout the year was given
to local governments, which all decided against
reopening them.
According to The Japan Times, the disaster
changed the national debate over energy policy
almost overnight.
"By shattering the government's long-pitched
safety myth about nuclear power, the crisis
dramatically raised public awareness about
energy use and sparked strong anti-nuclear
sentiment".
An energy white paper, approved by the Japanese
Cabinet in October 2011, says "public confidence
in safety of nuclear power was greatly damaged"
by the disaster and called for a reduction
in the nation's reliance on nuclear power.
It also omitted a section on nuclear power
expansion that was in the previous year's
policy review.Michael Banach, the current
Vatican representative to the IAEA, told a
conference in Vienna in September 2011 that
the disaster created new concerns about the
safety of nuclear plants globally.
Auxiliary Bishop of Osaka Michael Goro Matsuura
said this incident should cause Japan and
other countries to abandon nuclear projects.
He called on the worldwide Christian community
to support this anti-nuclear campaign.
Statements from Bishops' conferences in Korea
and the Philippines called on their governments
to abandon atomic power.
Author Kenzaburō Ōe, who received a Nobel
prize in literature, urged Japan to abandon
its reactors.The nuclear plant closest to
the epicenter of the earthquake, the Onagawa
Nuclear Power Plant, successfully withstood
the cataclysm.
Reuters said it may serve as a "trump card"
for the nuclear lobby, providing evidence
that it is possible for a correctly designed
and operated nuclear facility to withstand
such a cataclysm.The loss of 30% of the country's
generating capacity led to much greater reliance
on liquified natural gas and coal.
Unusual conservation measures were undertaken.
In the immediate aftermath, nine prefectures
served by TEPCO experienced power rationing.
The government asked major companies to reduce
power consumption by 15%, and some shifted
their weekends to weekdays to smooth power
demand.
Converting to a nuclear-free gas and oil energy
economy would cost tens of billions of dollars
in annual fees.
One estimate is that even including the disaster,
more years of life would have been lost in
2011 if Japan had used coal or gas plants
instead of nuclear.Many political activists
have called for a phase-out of nuclear power
in Japan, including Amory Lovins, who claimed,
"Japan is poor in fuels, but is the richest
of all major industrial countries in renewable
energy that can meet the entire long-term
energy needs of an energy-efficient Japan,
at lower cost and risk than current plans.
Japanese industry can do it faster than anyone
– if Japanese policymakers acknowledge and
allow it".
Benjamin K. Sovacool asserted that Japan could
have exploited instead its renewable energy
base.
Japan has a total of "324 GW of achievable
potential in the form of onshore and offshore
wind turbines (222 GW), geothermal power plants
(70 GW), additional hydroelectric capacity
(26.5 GW), solar energy (4.8 GW) and agricultural
residue (1.1 GW)."In contrast, others have
said that the zero mortality rate from the
Fukushima incident confirms their opinion
that nuclear fission is the only viable option
available to replace fossil fuels.
Journalist George Monbiot wrote "Why Fukushima
made me stop worrying and love nuclear power."
In it he said, "As a result of the disaster
at Fukushima, I am no longer nuclear-neutral.
I now support the technology."
He continued, "A crappy old plant with inadequate
safety features was hit by a monster earthquake
and a vast tsunami.
The electricity supply failed, knocking out
the cooling system.
The reactors began to explode and melt down.
The disaster exposed a familiar legacy of
poor design and corner-cutting.
Yet, as far as we know, no one has yet received
a lethal dose of radiation."
Responses to Monbiot noted his "false calculation
that [nuclear powered electricity] is needed,
that it can work economically, and that it
can solve its horrific waste, decommissioning
and proliferation-security pitfalls ... [along
with human] safety, health and indeed human
psychology issues."In September 2011, Mycle
Schneider said that the disaster can be understood
as a unique chance "to get it right" on energy
policy.
"Germany – with its nuclear phase-out decision
based on a renewable energy program – and
Japan – having suffered a painful shock
but possessing unique technical capacities
and societal discipline – can be at the
forefront of an authentic paradigm shift toward
a truly sustainable, low-carbon and nuclear-free
energy policy."On the other hand, climate
and energy scientists James Hansen, Ken Caldeira,
Kerry Emanuel, and Tom Wigley released an
open letter calling on world leaders to support
development of safer nuclear power systems,
stating "There is no credible path to climate
stabilization that does not include a substantial
role for nuclear power."
In December 2014, an open letter from 75 climate
and energy scientists on the website of pro-nuclear
advocate Barry Brook asserted "nuclear power
has lowest impact on wildlife and ecosystems
– which is what we need given the dire state
of the world’s biodiversity."
Brook's advocacy for nuclear power has been
challenged by opponents of nuclear industries,
including environmentalist Jim Green of Friends
of the Earth.
Brook has described the Australian Greens
political party (SA Branch) and Australian
Youth Climate Coalition as "sad" and "increasingly
irrelevant" after they expressed their opposition
to nuclear industrial development.As of September
2011, Japan planned to build a pilot offshore
floating wind farm, with six 2 MW turbines,
off the Fukushima coast.
The first became operational in November 2013.
After the evaluation phase is complete in
2016, "Japan plans to build as many as 80
floating wind turbines off Fukushima by 2020."
In 2012, Prime Minister Kan said the disaster
made it clear to him that "Japan needs to
dramatically reduce its dependence on nuclear
power, which supplied 30% of its electricity
before the crisis, and has turned him into
a believer of renewable energy".
Sales of solar panels in Japan rose 30.7%
to 1,296 MW in 2011, helped by a government
scheme to promote renewable energy.
Canadian Solar received financing for its
plans to build a factory in Japan with capacity
of 150 MW, scheduled to begin production in
2014.As of September 2012, the Los Angeles
Times reported that "Prime Minister Yoshihiko
Noda acknowledged that the vast majority of
Japanese support the zero option on nuclear
power", and Prime Minister Noda and the Japanese
government announced plans to make the country
nuclear-free by the 2030s.
They announced the end to construction of
nuclear power plants and a 40-year limit on
existing nuclear plants.
Nuclear plant restarts must meet safety standards
of the new independent regulatory authority.
On 16 December 2012, Japan held its general
election.
The Liberal Democratic Party (LDP) had a clear
victory, with Shinzō Abe as the new Prime
Minister.
Abe supported nuclear power, saying that leaving
the plants closed was costing the country
4 trillion yen per year in higher costs.
The comment came after Junichiro Koizumi,
who chose Abe to succeed him as premier, made
a recent statement to urge the government
to take a stance against using nuclear power.
A survey on local mayors by the Yomiuri Shimbun
newspaper in January 2013 found that most
of them from cities hosting nuclear plants
would agree to restarting the reactors, provided
the government could guarantee their safety.
More than 30,000 people marched on 2 June
2013, in Tokyo against restarting nuclear
power plants.
Marchers had gathered more than 8 million
petition signatures opposing nuclear power.In
October 2013, it was reported that TEPCO and
eight other Japanese power companies were
paying approximately 3.6 trillion yen (37
billion dollars) more in combined imported
fossil fuel costs compared to 2010, before
the accident, to make up for the missing power.From
2016 to 2018 the nation fired up at least
eight new coal power plants.
Plans for an additional 36 coal stations over
the next decade are the biggest planned coal
power expansion in any developed nation.
The new national energy plan that would have
coal provide 26% of Japan's electricity in
2030, presents the abandoning of a previous
goal of reducing coal's share to 10%.
The coal revival is seen as having alarming
implications for air pollution and Japan's
ability to meet its pledges to cut greenhouse
gases by 80% by 2050.
=== Equipment, facility, and operational changes
===
A number of nuclear reactor safety system
lessons emerged from the incident.
The most obvious was that in tsunami-prone
areas, a power station's sea wall must be
adequately tall and robust.
At the Onagawa Nuclear Power Plant, closer
to the epicenter of 11 March earthquake and
tsunami, the sea wall was 14 meters (46 ft)
tall and successfully withstood the tsunami,
preventing serious damage and radioactivity
releases.Nuclear power station operators around
the world began to install Passive Autocatalytic
hydrogen Recombiners ("PARs"), which do not
require electricity to operate.
PARs work much like the catalytic converter
on the exhaust of a car to turn potentially
explosive gases such as hydrogen into water.
Had such devices been positioned at the top
of Fukushima I's reactor buildings, where
hydrogen gas collected, the explosions would
not have occurred and the releases of radioactive
isotopes would arguably have been much less.Unpowered
filtering systems on containment building
vent lines, known as Filtered Containment
Venting Systems (FCVS), can safely catch radioactive
materials and thereby allow reactor core depressurization,
with steam and hydrogen venting with minimal
radioactivity emissions.
Filtration using an external water tank system
is the most common established system in European
countries, with the water tank positioned
outside the containment building.
In October 2013, the owners of Kashiwazaki-Kariwa
nuclear power station began installing wet
filters and other safety systems, with completion
anticipated in 2014.For generation II reactors
located in flood or tsunami prone areas, a
3+ day supply of back-up batteries has become
an informal industry standard.
Another change is to harden the location of
back-up diesel generator rooms with water-tight,
blast-resistant doors and heat sinks, similar
to those used by nuclear submarines.
The oldest operating nuclear power station
in the world, Beznau, which has been operating
since 1969, has a 'Notstand' hardened building
designed to support all of its systems independently
for 72 hours in the event of an earthquake
or severe flooding.
This system was built prior to Fukushima Daiichi.Upon
a station blackout, similar to the one that
occurred after Fukushima's back-up battery
supply was exhausted, many constructed Generation
III reactors adopt the principle of passive
nuclear safety.
They take advantage of convection (hot water
tends to rise) and gravity (water tends to
fall) to ensure an adequate supply of cooling
water to handle the decay heat, without the
use of pumps.As the crisis unfolded, the Japanese
government sent a request for robots developed
by the U.S. military.
The robots went into the plants and took pictures
to help assess the situation, but they couldn't
perform the full range of tasks usually carried
out by human workers.
The Fukushima disaster illustrated that robots
lacked sufficient dexterity and robustness
to perform critical tasks.
In response to this shortcoming, a series
of competitions were hosted by DARPA to accelerate
the development of humanoid robots that could
supplement relief efforts.
Eventually a wide variety of specially designed
robots were employed (leading to a robotics
boom in the region), but as of early 2016
three of them had promptly become non-functional
due to the intensity of the radioactivity;
one was destroyed within a day.
== Reactions ==
=== Japan ===
Japanese authorities later admitted to lax
standards and poor oversight.
They took fire for their handling of the emergency
and engaged in a pattern of withholding and
denying damaging information.
Authorities allegedly wanted to "limit the
size of costly and disruptive evacuations
in land-scarce Japan and to avoid public questioning
of the politically powerful nuclear industry".
Public anger emerged over an "official campaign
to play down the scope of the accident and
the potential health risks".In many cases,
the Japanese government's reaction was judged
to be less than adequate by many in Japan,
especially those who were living in the region.
Decontamination equipment was slow to be made
available and then slow to be utilized.
As late as June 2011, even rainfall continued
to cause fear and uncertainty in eastern Japan
because of its possibility of washing radioactivity
from the sky back to earth.To assuage fears,
the government enacted an order to decontaminate
over a hundred areas with a level contamination
greater than or equivalent to one millisievert
of radiation.
This is a much lower threshold than is necessary
for protecting health.
The government also sought to address the
lack of education on the effects of radiation
and the extent to which the average person
was exposed.Previously a proponent of building
more reactors, Kan took an increasingly anti-nuclear
stance following the disaster.
In May 2011, he ordered the aging Hamaoka
Nuclear Power Plant closed over earthquake
and tsunami concerns, and said he would freeze
building plans.
In July 2011, Kan said, "Japan should reduce
and eventually eliminate its dependence on
nuclear energy".
In October 2013, he said that if the worst-case
scenario had been realized, 50 million people
within a 250-kilometer (160 mi) radius would
have had to evacuate.On 22 August 2011, a
government spokesman mentioned the possibility
that some areas around the plant "could stay
for some decades a forbidden zone".
According to Yomiuri Shimbun the Japanese
government was planning to buy some properties
from civilians to store waste and materials
that had become radioactive after the accidents.
Chiaki Takahashi, Japan's foreign minister,
criticized foreign media reports as excessive.
He added that he could "understand the concerns
of foreign countries over recent developments
at the nuclear plant, including the radioactive
contamination of seawater".Due to frustration
with TEPCO and the Japanese government "providing
differing, confusing, and at times contradictory,
information on critical health issues" a citizen's
group called "Safecast" recorded detailed
radiation level data in Japan.
The Japanese government "does not consider
nongovernment readings to be authentic".
The group uses off-the-shelf Geiger counter
equipment.
A simple Geiger counter is a contamination
meter and not a dose rate meter.
The response differs too much between different
radioisotopes to permit a simple GM tube for
dose rate measurements when more than one
radioisotope is present.
A thin metal shield is needed around a GM
tube to provide energy compensation to enable
it to be used for dose rate measurements.
For gamma emitters either an ionization chamber,
a gamma spectrometer or an energy compensated
GM tube are required.
Members of the Air Monitoring station facility
at the Department of Nuclear Engineering at
the University of Berkeley, California have
tested many environmental samples in Northern
California.
=== International ===
The international reaction to the disaster
was diverse and widespread.
Many inter-governmental agencies immediately
offered help, often on an ad hoc basis.
Responders included IAEA, World Meteorological
Organization and the Preparatory Commission
for the Comprehensive Nuclear Test Ban Treaty
Organization.In May 2011, UK chief inspector
of nuclear installations Mike Weightman traveled
to Japan as the lead of an International Atomic
Energy Agency (IAEA) expert mission.
The main finding of this mission, as reported
to the IAEA ministerial conference that month,
was that risks associated with tsunamis in
several sites in Japan had been underestimated.In
September 2011, IAEA Director General Yukiya
Amano said the Japanese nuclear disaster "caused
deep public anxiety throughout the world and
damaged confidence in nuclear power".
Following the disaster, it was reported in
The Economist that the IAEA halved its estimate
of additional nuclear generating capacity
to be built by 2035.In the aftermath, Germany
accelerated plans to close its nuclear power
reactors and decided to phase the rest out
by 2022.
Italy held a national referendum, in which
94 percent voted against the government's
plan to build new nuclear power plants.
In France, President Hollande announced the
intention of the government to reduce nuclear
usage by one third.
So far, however, the government has only earmarked
one power station for closure – the aging
plant at Fessenheim on the German border – which
prompted some to question the government's
commitment to Hollande's promise.
Industry Minister Arnaud Montebourg is on
record as saying that Fessenheim will be the
only nuclear power station to close.
On a visit to China in December 2014 he reassured
his audience that nuclear energy was a "sector
of the future" and would continue to contribute
"at least 50%" of France's electricity output.
Another member of Hollande's Socialist Party,
the MP Christian Bataille, said that Hollande
announced the nuclear curb to secure the backing
of his Green coalition partners in parliament.Nuclear
power plans were not abandoned in Malaysia,
the Philippines, Kuwait, and Bahrain, or radically
changed, as in Taiwan.
China suspended its nuclear development program
briefly, but restarted it shortly afterwards.
The initial plan had been to increase the
nuclear contribution from 2 to 4 percent of
electricity by 2020, with an escalating program
after that.
Renewable energy supplies 17 percent of China's
electricity, 16% of which is hydroelectricity.
China plans to triple its nuclear energy output
to 2020, and triple it again between 2020
and 2030.New nuclear projects were proceeding
in some countries.
KPMG reports 653 new nuclear facilities planned
or proposed for completion by 2030.
By 2050, China hopes to have 400–500 gigawatts
of nuclear capacity – 100 times more than
it has now.
The Conservative Government of the United
Kingdom is planning a major nuclear expansion
despite some public objection.
So is Russia.
India is also pressing ahead with a large
nuclear program, as is South Korea.
Indian Vice President M Hamid Ansari said
in 2012 that "nuclear energy is the only option"
for expanding India's energy supplies, and
Prime Minister Modi announced in 2014 that
India intended to build 10 more nuclear reactors
in a collaboration with Russia.
=== Investigations ===
Three investigations into the Fukushima disaster
showed the man-made nature of the catastrophe
and its roots in regulatory capture associated
with a "network of corruption, collusion,
and nepotism."
Regulatory capture refers to the "situation
where regulators charged with promoting the
public interest defer to the wishes and advance
the agenda of the industry or sector they
ostensibly regulate."
Those with a vested interest in specific policy
or regulatory outcomes lobby regulators and
influence their choices and actions.
Regulatory capture explains why some of the
risks of operating nuclear power reactors
in Japan were systematically downplayed and
mismanaged so as to compromise operational
safety.Many reports say that the government
shares blame with the regulatory agency for
not heeding warnings and for not ensuring
the independence of the oversight function.
The New York Times said that the Japanese
nuclear regulatory system sided with and promoted
the nuclear industry because of amakudari
('descent from heaven') in which senior regulators
accepted high paying jobs at companies they
once oversaw.
To protect their potential future position
in the industry, regulators sought to avoid
taking positions that upset or embarrass the
companies.
TEPCO's position as the largest electrical
utility in Japan made it the most desirable
position for retiring regulators.
Typically the "most senior officials went
to work at TEPCO, while those of lower ranks
ended up at smaller utilities."In August 2011,
several top energy officials were fired by
the Japanese government; affected positions
included the Vice-minister for Economy, Trade
and Industry; the head of the Nuclear and
Industrial Safety Agency, and the head of
the Agency for Natural Resources and Energy.In
2016 three former TEPCO executives, chairman
Tsunehisa Katsumata and two vice presidents,
were indicted for negligence resulting in
death and injury.
In June 2017 the first hearing took place,
in which the three pleaded not guilty to professional
negligence resulting in death and injury.
In September 2019 the court found all three
men not guilty.
The judge decided that "it was not clear if
preventative measures could have been put
in place in time to prevent" the accident.
==== NAIIC ====
The Fukushima Nuclear Accident Independent
Investigation Commission (NAIIC) was the first
independent investigation commission by the
National Diet in the 66-year history of Japan's
constitutional government.
Fukushima "cannot be regarded as a natural
disaster," the NAIIC panel's chairman, Tokyo
University professor emeritus Kiyoshi Kurokawa,
wrote in the inquiry report.
"It was a profoundly man-made disaster – that
could and should have been foreseen and prevented.
And its effects could have been mitigated
by a more effective human response."
"Governments, regulatory authorities and Tokyo
Electric Power [TEPCO] lacked a sense of responsibility
to protect people's lives and society," the
Commission said.
"They effectively betrayed the nation's right
to be safe from nuclear accidents.The Commission
recognized that the affected residents were
still struggling and facing grave concerns,
including the "health effects of radiation
exposure, displacement, the dissolution of
families, disruption of their lives and lifestyles
and the contamination of vast areas of the
environment".
==== Investigation Committee ====
The purpose of the Investigation Committee
on the Accident at the Fukushima Nuclear Power
Stations (ICANPS) was to identify the disaster's
causes and propose policies designed to minimize
the damage and prevent the recurrence of similar
incidents.
The 10 member, government-appointed panel
included scholars, journalists, lawyers, and
engineers.
It was supported by public prosecutors and
government experts.
and released its final, 448-page investigation
report on 23 July 2012.The panel's report
faulted an inadequate legal system for nuclear
crisis management, a crisis-command disarray
caused by the government and TEPCO, and possible
excess meddling on the part of the Prime Minister's
office in the crisis' early stage.
The panel concluded that a culture of complacency
about nuclear safety and poor crisis management
led to the nuclear disaster.
== See also
