All language subtitles for Nova S42E12 Nuclear Meltdown Disaster.DVDRip.en.PBS

Japan's most powerful
earthquake ever...

triggers a monster tsunami.

Fear washes over the nation.

But that's just the beginning.

Ten nuclear reactors

at two power plants
are crippled,

threatening the unimaginable.

If Tokyo needed to be evacuated,

I feared the entire nation
of Japan

would be paralyzed by chaos.

It became darker and darker.

A terrifying situation.

We were fighting
an invisible enemy,

out-of-control reactors.

What will it take to save
the country from radiation?

Mankind has never faced

the forces of physics
and the forces of nature

that those people faced.

"Nuclear Meltdown Disaster,"
right now on NOVA.

This is the road to nowhere,

a once-thriving place

in one of the most prosperous
countries on earth...

Japan.

Radioactive Japan.

Time stood still here
on March 11, 2011.

Houses that aren't homes.

Schools that are silent.

Stores shuttered.

Towns without people.

Past the checkpoints,

the scans,

and the meticulous suit-up,

layer upon layer upon layer
of protection

is the place we simply know
as Fukushima...

site of three
nuclear reactor meltdowns.

This is called the Central
Control Room.

All of the equipment
at the power plant

is operated from here.

He is a nuclear plant operator.

This is where
he has always worked.

He used to live nearby,
but now he too cannot go home.

He and his co-workers
are ashamed,

scorned by the neighbors
they once had.

We've been through so much

in this control room.

It's hard to put into words.

He was here when it happened.

Now he is hoping to make amends

by helping clean up
the toxic mess.

Four years ago,
this room was completely dark.

We had only small fluorescent
lights and flashlights.

We had given up
on our own survival.

Now, talking to you
with the lights on,

it seems like a lifetime ago.

This is the story
of the Fukushima meltdowns.

The infamous events at Fukushima
Daiichi, or number one...

told by those who were there
and risked everything.

And the lesser-known story
of its sister plant

seven miles away:
Fukushima Daini, or number two.

It faced the same onslaught
and challenges,

but thanks to a little luck
and a herculean effort,

it was saved
from ending up like this.

March 11, a bad day for Japan
and the world,

could have been so much worse.

The inevitable came
without warning at 2:46 p.m.

Two giant pieces
of the earth's crust,

tectonic plates,
move suddenly and violently.

One pushes down,
causing the plate above it

to spring upward like a catapult
along a 300-mile fault line.

In a nation all too familiar
with earthquakes,

it is the largest ever recorded:
magnitude nine.

Propagating outward
at 9,000 miles an hour,

record-breaking seismic waves
careen toward land

and the ten nuclear reactors
at the two Fukushima plants,

all of them designed
by General Electric,

owned and operated by
the largest utility in Japan...

The Tokyo Electric
Power Company...

TEPCO.

They are there to feed

the insatiable energy needs
of Tokyo.

Suddenly, I heard
the earth rumble,

like a fierce growl.

It was an extremely
intense earthquake.

But it wasn't only strong,
it was also terribly long.

An American nuclear reactor
service technician,

Carl Pillitteri, is there
doing some upgrades.

It was just one big hammer.

The entire building was moving.

Everything was coming down.

The lights were crashing
everywhere.

And it just got worse
from there, actually.

In one nanosecond, just
the entire floor went black.

The shaking was like nothing
I had experienced.

The operators either held
onto that bar or crouched down.

That's how we endured
the earthquake.

I just wondered,

"How long is this going
to continue?"

It lasts six minutes.

Takeyuki Inagaki

is general manager
of the maintenance department

for Units 1 through 4
at Daiichi.

He reports directly to the
superintendent, Masao Yoshida.

Both men have spent
their entire careers at TEPCO.

Inagaki worries about his wife
and two sons.

When the earthquake hit,

I think I sent one email
to my wife explaining that

I didn't think I'd be able
to come home for a while.

After I sent it, we lost contact
with the outside.

We couldn't even make calls.

Seismometers at nuclear plants
are designed to trigger

an automatic emergency response
after an earthquake.

Power plant operators
routinely drill for this,

but it is still a risky,
tense event.

Called a SCRAM, it is designed
to put the brakes

on the nuclear chain reaction
of sustained fission.

A nuclear reactor
is fueled by uranium,

an element that naturally
splits apart,

releasing neutrons.

But uranium fission
can induce more fission.

When a loose neutron fires
into a nearby uranium nucleus,

it becomes unstable
and quickly splits.

Each time an atom splits,
it generates heat.

To make fission robust enough
to generate power,

uranium is enriched,
shaped into pellets,

and then stacked in long tubes
called fuel rods.

This ensures
lots of uranium atoms

are close enough to each other

to allow
a healthy chain reaction.

To manage the rate
of the reaction,

control rods
that absorb neutrons

are moved in and out of spaces
among the fuel.

During a SCRAM, the control rods
are pushed all the way in,

terminating the chain reaction.

By 3:02, operators at Daiichi
confirm the three reactors

that were online
have successfully SCRAM-ed.

And at Fukushima Daini,

all four reactors
running full throttle

also automatically shut down
safely.

Even though
the nuclear chain reaction

has now abruptly stopped,

the uranium fuel rods
remain very hot.

It's called decay heat.

The nuclear chain reaction
was stopped within seconds,

but the decay heat
continued to be a problem.

It takes approximately
20 to 24 hours

for the systems
to cool the reactor down

to less than 212 degrees

and achieve what's called
"cold shutdown."

At its core,
a nuclear power plant

is not unlike a pressure cooker
on a stove.

Water is heated
to the boiling point,

creating steam.

And steam under pressure
turns turbines,

generating electricity.

The complexity and cost
of nuclear energy

is about keeping the radioactive
genie in the bottle.

So the uranium fuel
sits inside rods underwater

in a steel pressure vessel

surrounded by a concrete
and steel containment structure

inside a reactor building.

All those layers of protection
are there

in case the water stops flowing.

If that happens,

it quickly boils away,
exposing the fuel,

and it melts,
turning into radioactive magma.

Unchecked, it will melt right
through the steel reactor vessel

and on to the concrete
and steel containment structure

that surrounds it.

So at the Fukushima plants now,
it is critical

that the electric water pumps
and valves keep running

for the reactor core
to safely cool down.

Power normally comes
from the electric grid,

and the earthquake
has caused a blackout.

But there is a plan B.

The plant is equipped
with diesel electric generators

to provide power
in an emergency.

They start automatically,
as they're designed to do.

If it had only been
the earthquake,

we wouldn't be here today.

The safety systems
were doing their thing,

the reactor cores
were being cooled,

and things were going
pretty well.

When the sea floor
suddenly moves upward

during the earthquake,

it causes the water near
the epicenter to rise with it.

The giant swell is the start
of a tsunami.

Forecasters issue
a tsunami warning.

They predict ten-foot-high waves
in Fukushima Prefecture.

The main buildings
at Daiichi and Daini

are about 30 feet
above sea level,

so no one worries much
about a tsunami.

And then, at 3:27 p.m...

the first of seven giant waves

crashes over the seawall.

Then I saw the tsunami coming.

I was on top of that hill,

and I wondered
if I was high enough.

This thing was, you know...

It was huge.

The tallest surge of water
is nearly 50 feet high,

more than twice the height
of the seawall.

I assumed there would be
a tsunami,

but not one 50 or 55 feet high.

I couldn't even imagine
a tsunami like that.

Fukushima Daiichi is inundated.

Two workers drown,
trapped in the basement

of the number four
turbine building.

Six generators,
along with the wiring,

switches, and breakers
connecting them to the plant

are located in the basements

of the turbine buildings
for Units 1 through 4.

The flood waters
destroy them all.

Two additional generators
behind Unit 4 are high and dry,

but their switching gear
is in the basement,

ruined by the seawater.

The generators would be useless.

Meanwhile, seven miles
to the south

at the other Fukushima plant...
Daini, or number two...

The crisis is equally dire.

The big waves roll in,

swamping key motors, wiring,
pumps, and generators.

Immediately after
the tsunami hit,

this room lost power.

That's when I realized something
very serious had happened.

Naohiro Masuda
is the plant superintendent

on that fateful day.

He began his career here
at Daini,

reporting for duty in 1982
while it was still being built.

He knows it as well as anyone.

This building is 40 feet
above sea level,

and since there was
a power outage here,

I imagined most of the buildings
near the sea

were damaged by the tsunami.

From that point on,
we knew we were in trouble.

Operators in the control rooms
give Masuda very bad news:

Units 1, 2, and 4

no longer have any operative
cooling systems.

In nuclear power, we say,
"Stop, cool, and contain."

These are the three
most important functions.

When I realized that
we had lost cooling,

I knew the situation
was extremely serious.

But what needs to be fixed?

And how?

He orders a team
of about 40 workers

to go out
and inspect the damage.

There were several hundred
aftershocks that day.

I really hesitated
to give the order

to send people out on-site.

They arrive in the rooms

housing electric motors
that run the pumps

that draw seawater
to cool the reactors.

Cars had been washed
right up to the door,

and there were huge piles
of debris.

They said, "How could you have
sent us to such a place?"

Today, they have preserved some
of the evidence of the flood

that wiped out the motors
and their wiring.

Electrical supply systems
are located in this room.

The tsunami came up to here.

Back at Daiichi,

Reactors 1 through 4
are now in total darkness,

and things are quickly spiraling
out of control.

We were in the middle
of dealing with the accident.

Then, all at once,
the lamps went out.

All sorts of alarms
were going off.

All of those went out.

Basically, a station blackout.

"Station blackout"...
the two most dreaded words

in the world
of nuclear power generation.

At Fukushima Daiichi,

Reactors 1 and 2 not only lose
the alternating current

that powers the pumps
and valves,

but also the direct current,

there to keep the instruments
working.

It became darker and darker,

a terrifying situation.

And the operators weren't sure
what was happening.

We couldn't even tell
if there was water

in the nuclear reactors.

We were at the starting line
of a race,

but we didn't know
if we'd need to run 100 yards

or if we'd need to run
a marathon.

The oldest reactor at the site
is Unit 1.

It began operation in 1971

and is equipped with outmoded
last-resort cooling systems

called isolation condensers.

The steam being produced
by the hot reactor core

was routed
into this large tank of water.

The water would cool the steam,
convert it back into water,

and it would drain back
into the reactor core

to be recycled
over and over again.

It is a passive system designed
to work on natural circulation

without any electrical power
at all.

So, is it working?

In the darkened control room,
they don't have a clue.

What they did not know
at the time

is when the power fails,
the isolation condenser valves

are almost completely closed,

curtailing the flow
of steam and water.

When the isolation condensers
failed on Unit 1,

the reactor water level
just started boiling away

because it was no longer
being cooled and maintained

by the isolation condensers.

If the isolation condensers
are working properly,

vents on the side
of the reactor building

would be releasing
huge amounts of steam.

There was steam coming out
of the discharge of it,

but they didn't realize
it wasn't sufficient.

So they thought they had
more time than they did.

Now, there is nothing
to stop the meltdown.

At 3:42 p.m., 15 minutes after
the tsunami waves rolled in,

TEPCO notifies the national
and local governments

that there is a "special event"
at the plant.

Actually, it is an emergency
that has never been envisioned.

It was a situation

that hadn't been anticipated.

We couldn't use
the procedure manuals.

What was happening was
beyond what we trained for

on a daily basis.

Using what little information
we had,

we had to decide immediately,
"What can we do?

What should we do?"

It was a race against time.

They desperately need power,
but from where?

TEPCO dispatches
generator trucks,

but they are slowed by
earthquake and tsunami wreckage.

When they finally arrive
late on the 11th,

damage to the plant's
electrical system

makes it all but impossible
to connect them.

So they must improvise,

hoping to jury rig their
dead instruments back to life

by raiding the parking lots,

grabbing as many batteries
as they can from buses and cars.

It took several hours

to figure out
how to connect the batteries.

They had the schematic
wiring diagram,

and they were furiously
examining it for several hours.

We ended up wasting
a lot of time.

Meanwhile, the water is
boiling away fast in Unit 1.

But how fast?

Six hours after the tsunami,
at 9:19 p.m.,

they finally get the batteries

and some portable
generators rigged

so the instruments
can flicker on.

The gauges show the water level
in Reactor 1,

normally 20 feet above the top
of the uranium fuel,

is now only eight inches
above it.

They pencil in a running record
of the water levels

right beside the gauge.

But the pressure in the vessel
is so high

it causes inaccurate
instrument readings.

They learn later
the uranium fuel

had actually been exposed
for three hours.

It's becoming more like

a lava flow from a volcano.

So it overheated, melted,
released radioactive contents,

and started falling into the
bottom of the reactor vessel.

In Tokyo, Japan's
prime minister, Naoto Kan,

worries that he might have
to order a mass evacuation

from Fukushima
all the way to Tokyo:

50 million people.

If Tokyo needed to be evacuated,

I feared
the entire nation of Japan

would be paralyzed by chaos
for quite a long time.

At 9:23 p.m., he orders everyone

living within two miles of
Daiichi to evacuate immediately

so TEPCO can prepare
to vent some steam...

Radioactive steam.

At this stage,
radioactive iodine-131

is the isotope
of greatest concern.

It is linked to thyroid cancer.

Children are most vulnerable.

We knew we had to vent,

but the question was, "How?"

There was no electricity,
and the valve was pneumatic.

We needed an air compressor
to open it,

but we didn't even have that.

Kan becomes increasingly
frustrated and impatient.

Even though we approved it,

many hours went by
and they still had not vented.

We asked them why.

A specialist from TEPCO told me,
"I don't know the reason."

Much of the information
he was getting

from his government
and the utility

turned out not to be true,

and he had no source
of independent knowledge

of what was going on
in those reactors.

Kan decides the only way
to know for sure is to go there,

and so early on the morning
of March 12,

he flies to Fukushima Daiichi.

He passes over mile upon mile
of utter devastation

from the earthquake and tsunami.

Nearly 16,000 are dead.

He lands at Daiichi
just after 7:00,

about 15 hours
after the tsunami.

I met with Superintendent
Yoshida for 45 minutes.

While he explained
the situation on-site,

I could see that he was a person
who could be trusted.

The prime minister endorses
the superintendent and his plan.

Yoshida vows to begin venting
at 9:00 a.m.

But there is much to do
and much to consider.

To go into a pitch-black
reactor building

with the containment vessel
pressure so high,

I don't know if I should say it,

but it felt like we were putting
together a suicide squad.

To open the vent, they need
to manually turn two valves:

one in the basement
and another on the second floor.

At 9:04 a.m., a pair of workers
makes their way

through a dark labyrinth

to the second floor
of the Reactor 1 building.

It takes them 11 minutes
to open the valve.

Nine minutes later

a second team heads
for the valve in the basement.

They get to a point about midway

and the radiation is higher
than they thought they'd get.

They basically had drawn up,

"If radiation gets to this
point, we'll go back."

Well, they got to that point
before they got to the valves.

They abort their mission.

In the Emergency Response
Center, they realize

they must find a way to open
the vent remotely.

They scramble to find an air
compressor that can be attached

to the pipe that blasts
the valve open.

Finally, at 2:50 p.m.,

steam starts rising
from the exhaust tower

and the pressure starts
dropping.

Could the worst be over?

Actually, it is just
about to begin.

At Daini, where the power
is still out

and the reactors
are getting hotter,

there is a stroke of luck.

There is power inside the
radiation waste building

behind Reactor 1.

But they need it down
by the water.

Naohiro Masuda decides
to lay cables,

hoping to restore cooling
to the reactors.

Each of the four reactors needs
three operative pump motors.

They need to lay five-and-a-half
miles of cable

to connect them all.

He needs supplies urgently...

At least 50 big spools
of heavy-duty cable.

Masuda orders the cable,
but the shipment is delayed.

The police were
busy redirecting traffic

for evacuations

and when the truck hit those
detours it wound up going

in the completely wrong
direction.

While they wait at Daini,

the crisis is getting
much worse at Daiichi.

Uranium fuel rods are encased
in zirconium.

If it gets too warm,

there's a chemical reaction
between the zirconium

and the water or steam

to produce large amounts
of hydrogen.

The containment structure
on a boiling water reactor

is sealed with a dome-shaped top
that is removed for refueling.

The pressure in Reactor 1
is now so high

that it slightly lifts the top.

The hydrogen escapes
through the gap

and into the reactor building,
where it mixes with air.

It would be just a matter
of time

before the highly flammable gas
would explode.

It is 3:36 p.m.

Suddenly there was an upward
thrust, an impact that seemed

to push the whole building
upward

and it became completely dark.

I thought it was
just another aftershock,

but we all sensed something
was very wrong.

Then headquarters told me

that the top of the reactor
building

was completely destroyed.

When I heard that,
I was shocked.

It is a devastating setback.

I think that most of us
who were working at the time

didn't feel like we were going
to make it out alive.

At Daini, workers are preparing
to lay the heavy cables

when they get word
of the explosion at Daiichi.

After the explosion, I had
everyone outside come back

into the Emergency
Response Room.

There were 500 to 600 people
in the room.

I said, "Please trust me.

"I definitely won't do anything
to harm you,

"but Fukushima Daini is still
in trouble

and I need you to do your best."

The cables arrive
on the morning of the 13th.

Finally, the heavy lifting
to save Fukushima Daini begins.

These were
large-capacity motors,

several hundred amperes,
so the cables were fairly thick.

Each person had to walk

while carrying around
35 pounds of cable.

It is a race against time
and physics.

Normally, If you
wanted to lay that much cable,

it would take you about a month.

I didn't actually think
it was possible

in the amount of time
that we had.

A total of around 200 workers
were involved.

We swapped people out
when they got exhausted.

In the midst of this, Masuda is
running out of fresh water

to cool his crippled reactors.

He asks TEPCO headquarters
for a shipment.

I asked Tokyo for 4,000
tons of water,

but instead they delivered

4,000 liters
of bottled drinking water.

That made me realize that we
were on our own.

We couldn't count on Tokyo.

So we started looking for water.

He remembers a creek
used as a water supply

during construction
of the plant.

Workers repair
the leaky old pipe

with a scavenged bicycle tube.

At Daiichi, events are still
overtaking them.

As the dust settles at Unit 1,

they learn five workers
are injured.

With freshwater reservoirs
exhausted,

they scramble to inject seawater
into the reactors.

By 7:04 p.m., success.

But using corrosive seawater

means the reactors will surely
be destroyed.

TEPCO headquarters tells
Superintendent Yoshida to stop

while they seek
government approval.

Yoshida does
this very dramatic thing

where on the video conference,
he orders the people

to stop the seawater injection.

Before that, he'd called them
over and said,

"I'm going to order you to stop
the seawater injection.

"Ignore that.

"That's just for Tokyo.

You continue
the seawater injections."

Personally, I think the decision

that Superintendent Yoshida made
was the right one.

If we had stopped
the seawater injection

at that point, I think things
would have been much worse.

In the meantime,
Unit 3 was becoming unstable.

Now our mission was "Don't let
Unit 3 turn into Unit 1."

With no battery power,

they are unable to open the
valves to begin venting Unit 3.

And there are no handles
on these valves.

So they grab car batteries,

hoping to open them
from the control room.

By 9:00 a.m. Sunday, March 13,

the Unit 3 reactor core
is exposed and melting.

The pressure keeps rising.

Fearing another hydrogen
explosion,

Yoshida orders workers
to retreat

to the Emergency Response Center

early on the morning
of March 14.

But the pressure plateaus and he
lifts the order an hour later.

We alternated between deploying
and pulling back workers

because we were afraid of
another hydrogen explosion.

Unfortunately, we had close
to 50 people positioned

around Unit 3
when the explosion happened.

It is 11:01, March 14.

Since there were so many people
out there,

I was really afraid
for their safety.

I thought to myself, "It's very
possible someone was killed."

Then, one by one,
people started to trickle back.

They were all very pale in the
face and some were bleeding.

When Unit 3 explodes,
11 workers are injured.

Amazingly, no one is killed.

And when we finally accounted
for everyone,

that's when we noticed the water
level in Unit 2 was dropping.

It seems inevitable that Unit 2
will be the next to blow.

At noon on March 14, an hour
after the explosion at Unit 3,

the water covering
the hot radioactive fuel

begins to drop precipitously.

An hour and a half later,

the emergency backup
cooling system fails.

Superintendent Yoshida quietly
tells a few trusted workers

to prepare buses
for an evacuation.

For now he has no choice

but to order his men
back into harm's way.

After the explosion of Unit 3,

he begged us to again go
to the field to save Unit 2.

It was very impressive.

But by 6:22 p.m.,
the water is gone.

The uranium fuel is completely
uncovered and melting.

Again they try to use car
batteries to open the vents

and relieve some pressure.

No luck.

From the 14th

until early in the morning
on the 15th,

it was really...
how can I describe it?

It was like being in hell.

As day breaks on the morning
of March 15,

they hear a loud explosion.

But it is not what they dread.

It is a complete surprise.

There has been
an explosion in Unit 4.

But this reactor was shut down
for maintenance

when the tsunami hit.

What could have happened there?

And what saved Unit 2
from blowing up?

The investigation
will have to wait.

Superintendent Yoshida orders
an immediate evacuation

of 650 workers.

He and nearly 70 supervisors
would stay.

In the confusion, they become
known as the "Fukushima 50."

We were fighting an invisible
enemy, out-of-control reactors.

It was like fighting a war.

It is midnight on the 13th.

In the Daini control room,
operators are girding

for what seems inevitable:

venting radioactive steam
into the environment.

Then the cables and the motors
finally start falling

into place, and the mood shifts
dramatically.

When we got word

that they were finished running
the cable, there was applause.

Then they tested the motors

and reported,
"The motors are working!"

And there was more applause.

When the pumps were
finally working

for units one, two, and four,

there were three bursts
of applause, one for each.

It was such a rush!

I can't believe they did it.

What a team they are.

They pulled off
something incredible.

I thought, "They did it!"

The pressure in Unit 1 had risen

to just under the containment
vessel's pressure limit.

We had about two hours to spare.

I'd say we made it
by the skin of our teeth.

At Daiichi, Superintendent
Yoshida has now lifted

the evacuation order,

and workers that had fled
start to return.

Things had bottomed out

and for the first time we were
able to catch our breath.

Then we started to worry
about cooling the fuel pools.

The pools are high up
in the reactor buildings,

there to store both
spent and new uranium fuel.

There are more than 3,100
fuel bundles,

millions of uranium pellets,

in the pools
for units one through four.

They are not inside
the containment vessels,

and there are no emergency pumps
to keep them full.

Should the pools go dry,

the rods could overheat
and catch fire in the open air,

releasing
a huge amount of radiation.

This is the worst-case scenario

that has haunted
Prime Minister Kan.

It could force him to order
a mandatory evacuation

of everyone for 150 miles
or more.

Tokyo uninhabitable...

maybe for decades.

It is hard to fathom.

Nuclear plant operator Chuck
Casto, then an NRC executive,

arrives at Fukushima Daiichi

in the midst of this turmoil
and uncertainty.

The biggest challenge
right away,

as soon as I stepped foot
on the ground, was,

"Should people take lethal doses
to stop this accident?"

The situation was desperate...

Concerns we had never faced
before...

And we were trying to work
our way through them

the best we could.

It is time for
desperate measures.

On the morning of March 17,

Self Defense Forces helicopters
fly four daring missions,

hoping to dump seawater
onto the Unit 3 spent fuel pool,

which appears
to be boiling away.

Radiation forces them to fly
high above the plant... too high.

In reality, barely any of
the water got into the pool.

And tensions were
still running high.

So they turn
to an elite rescue squad

from the Tokyo fire department.

They plan to use equipment

designed to fight
high-rise fires.

They arrive at the plant
late the next night.

They are led by Deputy Chief
Yukio Takayama,

a 35-year veteran.

The plan was to get water into
Unit 3 by any means necessary.

It needed to be dead on,
not like when you put out a fire

and spray the water
anywhere you want.

Two thoughts kept running
through my mind:

"Please be over soon"

and "What will I do
if this place explodes?"

I had never felt

that kind of fear before.

I thought, "This is
what it feels like

to really be in trouble."

They get the job done
in 20 minutes.

Day breaks.

The water is now flowing.

The fuel in storage is never
exposed to the air

and the feared radiation is
not released.

Tokyo is saved.

Little by little,

in a small way, we started
to have some hope.

Up until then,
we were spiraling further down

and now we were dangling there.

We weren't falling anymore.

For the first time in days,
Takeyuki Inagaki finds the time,

and a working phone,
to call home.

My wife asked me, are you okay?

I could tell she was very
emotional from her voice.

I said, "I'm alive for now
and I have all my limbs.

Please take care."

In the days and weeks ahead,

the nightmare does not end,
but at least it gets no worse.

Concrete pump trucks unleash
steady torrents of seawater

onto the fuel pools.

Power is fully restored to the
plant, finally, on March 21.

By June, they install a complex
filtration system

to remove cesium

from the water washing
through the radioactive debris

and flowing into the Pacific.

And slowly the answers start
trickling in.

Why did Unit 4 explode?

It used the same vent stack
as Unit 3.

When hydrogen built up there,

it seeped into Unit 4
via a shared duct.

Why didn't Unit 2 blow up
as they feared?

They realize the explosion
at Unit 1 knocked out a door

near the top of the Unit 2
reactor building.

It allowed hydrogen
and radiation to escape Unit 2.

While it was venting, the wind
shifted toward land,

sending the highest
concentrations of cesium

to the northwest.

The fallout will linger
for decades.

Eight months after
the earthquake and tsunami,

reporters tour
Fukushima Daiichi.

Superintendent Masao Yoshida
tries to downplay the worry.

The plant is stable enough

for local residents to have
peace of mind.

However, it's still very
difficult to work

under the current conditions.

Yoshida had been reprimanded
by his TEPCO superiors

for disobeying orders
and injecting seawater

during the worst of the crisis.

What about his workers?

Six that ventured
into the reactor buildings

trying to open the vent valves
got the worst doses...

As much as 678 millisieverts
of radiation.

5,000 millisieverts is
considered lethal,

and 250 is the maximum
normally allowed

for nuclear plant workers
in an emergency.

The cancer risk
for those six Daiichi workers

is undoubtedly greater
in the long run.

But during that fateful week,

they all believed there was
no long run for them.

To be blunt, there were
a number of times

that I thought I would
probably die.

We couldn't predict anything.

The worst-case scenario
for the meltdown

was that it would get
out of control.

I felt that this was possible.

And so I thought,
"Maybe this is the end."

One month later,

the hot melted cores
finally drop

below the boiling point
of water.

Cold shutdown.

By then, Yoshida is gone.

He has cancer,
unrelated to his job.

He dies in July of 2013.

Yeah, he was always
keeping his head.

Always encouraging people.

He was a good leader.

You might even say
he was superhuman.

Not just because of the quality
of his decisions,

but how quickly he made them.

Without him,

I could not have...

Yeah, I could not be here.

Fukushima, four years later.

What was once one of the largest
nuclear power plants

in the world

is now the center of the most
complex, expensive,

expansive cleanup
ever attempted.

It could take
as long as 40 years.

It will rely on technology
not yet invented

and the determination
of people not yet born.

The man in charge of it all is
the hero of Fukushima Daini.

Naohiro Masuda is now TEPCO's
chief decommissioning officer.

It is a very different challenge

than what he faced
in March 2011.

This is the first time

anyone has attempted this kind
of decommissioning.

No one in the world
has this experience.

So when we try to set a goal
to work towards,

I can't even give
clear instructions

because we're still figuring out
what it is we're trying to do.

This is not Chernobyl,

hastily abandoned,

encased in a tomb
and encircled by a fence.

This is Japan,
where land is precious

and they have a history
of rising from ruin.

Here, they hope to erase
the painful past

and maybe one day
return to their homes.

I was born and raised
in this area,

the same area where we are
decommissioning.

It's not possible
to live here now,

but we all have a strong desire
to make it habitable again.

I think that's
what keeps us working.

It is a disaster with deep roots
at high levels,

bad design decisions,

technological hubris,
a broken safety culture.

But in Japan,
the sins of the company

are the sins of its workers,

so they are considered culprits
as well as victims.

We did what we had to do.

I strongly regret

the inexcusable situation
that unfolded.

Mankind has never faced
the forces of physics

and the forces of nature
that those people faced.

The system may have failed,

but those operators did the best
they could with what they had.

In my mind,
they were absolute heroes.

There's nothing to be proud of.

Most of the plant workers were
born and raised here.

They wanted to protect
their hometown,

protect their families.

The reality is,

tens of thousands of people are
still under evacuation...

and we're the ones
that caused that.

By no means are we heroes.