Original subtitles

Today, on Impossible Engineering, the largest movable building in the world.

My first reaction was how huge this thing is.

Absolutely mind -blowing.

Constructed in the middle of a deserted nuclear disaster zone.

Working in this environment presented immense challenges for us because it's

world's most contaminated place.

And the pioneering historic innovations.

Oh, this is it.

It's a massive structure.

What a breathtaking view.

The most iconic building in New York City.

That made the impossible possible.

This is the Ivankiv district of Ukraine in Eastern Europe.

Once part of the mighty Soviet Union, it became a world of ghost towns and

hastily abandoned cities.

It's one of the most radioactive regions on the planet, with over 960 square

miles deemed uninhabitable.

All the result of one of the world's worst engineering failures.

In 1986, a routine safety test went devastatingly wrong at the Chernobyl

power plant, and a series of explosions spread clouds of deadly radiation across

Europe and beyond.

Safety teams rushed to cover the wrecked reactor with a rapidly constructed

concrete box.

The emergency measure was a temporary fix to contain the danger.

But now, 30 years later, the structure around the damaged reactor is at serious

risk of failure, threatening all of Europe once again.

So, some of the greatest engineering minds from around the world have come

together to design a unique solution.

A giant protective container known as the new safe confinement.

It's enormous.

It's 108 meters high. If you're British, it would cover St. Paul's Cathedral. If

you're American, it covers the Statue of Liberty.

If you're Italian, it would cover the Coliseum. And if you're French, it's

times the weight of the Eiffel Tower.

This is absolutely a one -of -a -kind structure.

It is, in fact, the largest man -made, movable land structure ever built.

It weighs 36 ,000 tons,

257 meters wide, and has a length of

160 meters. It's huge, and no one has ever built anything like this before.

But this is more than just a building.

It's a machine designed to facilitate one of the most important ongoing

engineering projects in history.

Dismantling and cleaning up the destroyed reactor.

A task which could take more than 100 years.

Designed to withstand a century of Ukraine's bitterly cold winters and

summers.

A 27 ,000 -ton steel frame supports the giant metal panels which slide over the

existing shelter, creating a barrier to stop radioactive dust from escaping.

With an uninterrupted floor area of 463 ,000 square feet, it's big enough to

house eight jumbo jets.

Simon Evans is one of the project's overseers.

The role of the new safe confinement is twofold. Firstly, to confine the old

reactor so it can ensure you minimise any future releases of radiation.

And secondly, to provide the infrastructure to start taking the old

apart and put it into a safe and secure long -term condition because 96 % of the

lethal radioactive inventory is still sitting inside that building. So it had

be secured.

Heading up the team of project managers is Mac McNeil.

The structure that was built over the reactor was constructed in six months

following the actual disaster.

Because it was such a radioactive environment, the people who worked on it

not use traditional construction methods.

So the structure itself was never a very stable structure.

To be able to dismantle it.

The old radioactive building must be entirely covered.

But this provides a seemingly impossible engineering challenge on a scale never

attempted before.

I think this is one of those projects that people thought could not be done.

So how do you build a self -supporting structure capable of enclosing a volume

of 35 million cubic feet?

The answer lies with techniques pioneered almost a century ago.

Once upon a time, airships were seen as the future of aviation.

But their sheer magnitude presented a problem.

Storage space.

That solution would come from Czech -born airship pioneer Carl Arnstein.

To build and house his mighty machines, Arnstein designed an unprecedented new

hangar and built it in Akron, Ohio.

Mechanical engineer Dan Dickrell is visiting to see how this groundbreaking

structure could provide answers to the challenge engineer space in Chernobyl.

Oh, this is it. This is the Akron Air Dock.

It was built in 1929.

At the time, it was the largest single room on Earth.

The Akron Air Dock is almost 1 ,200 feet long.

328 feet wide and 213 feet high, with a floor area of 387

,000 square feet.

We can fit the Statue of Liberty from side to side and the Empire State

from end to end with just a little bit sticking out.

The reason why that's possible is because the air docks volume is entirely

usable. There are no internal support columns.

It's this type of uninterrupted floor space that the engineers at Chernobyl

to build to contain the reactor.

So how did Arnstein achieve it?

The roof is supported by 11 parabolic steel arches.

This keeps the floor completely clear of internal columns.

But the vast size of the hangar presented a serious problem to its

stability.

Steel reacts to changes in temperature.

On a small scale, it's hardly noticeable.

But in what was then the world's biggest room, it could have catastrophic

consequences. So when the sun hates the steel structure, it causes it to expand.

So Arnstein designed the building to breathe.

This is the leg of one of the arches.

Down at the bottom, there's a foot.

Now the footer is floating. It's not originally connected to the ground. And

this is the key innovation that allows the building to expand and contract as

heats and cools.

If it was originally connected to the ground, the building would essentially

itself apart.

The techniques used in its design and construction, which seemed radical at

time, have become commonplace in constructing a building of its size.

Engineers at Chernobyl must adapt this concept to create something big enough

contain the decaying carcass around the reactor, or they risk another nuclear

disaster.

Mac McNeil, the lead project manager, has clearance to enter the restricted

near the failed reactor.

And what you're looking at here is the structure that was built over the

very hastily in 1986 after it blew up.

Over the last 30 years since the accident, the structure itself has

deteriorate. You can see a lot of corrosion on it showing the effects of

weathering. And when you think of it, how huge this structure is.

The dimensions of this new safe confinement are really spectacular.

Like Arnstein's air dock, the structure of the new safe confinement relies on

the power of the arch.

The metal framework is made up of a series of 16 arched trusset, standing at

over 328 feet high.

Steel structure is very, very large.

They are all bolted together.

There's no welding on it. And there are over 600 ,000 bolts that hold it all

together. It's a very, very complex structure, but it has to be because of

size and the overall weight of the arch.

And unlike most other construction projects, failure to complete it puts

at risk.

Because not only is the new safe confinement building a complicated,

-breaking structure, it also sits directly above one of the most

places on Earth.

Building at the location of a notorious nuclear disaster comes with a unique set

of challenges.

As one of the project leads at Chernobyl's new safe confinement, Simon

well aware of his job site's hazardous conditions.

It's an immensely time -sensitive project because the longer you delayed,

more dangerous it became.

Careful around here.

As the head of the project for its financiers.

Simon Evans had special security clearance to go even deeper into the old

reactor complex, to the heart of the disaster.

It's an enormous facility and very, very complex and very difficult to find your

way around.

Security's tight due to the unspent nuclear material still present.

The amount of time he can spend here is carefully controlled.

The judgments are that you have around 200 tonnes of material sitting inside

Unit 4, inside the sarcophagus, which is probably about 10 metres to our right,

fortunately through lots of walls of thick concrete.

This is the heartbeat of the old reactor, the control room.

The job of the controllers was to monitor constantly the power in the

make sure the levels were stabilised.

And what happened at the time of the accident was they lost control of the

reactor.

So I find this a very haunting place, to be honest, almost a monument to the

importance of doing things safely.

Designing this vital structure is one thing.

Building it in a nuclear disaster zone is another.

Working in this environment presented immense challenges for us.

The first thing we had to do was clean the site, and then we had to make sure

that we had all sorts of support facilities in place to enable many

workers to come in over many years.

The biggest challenge, of course, is radiation.

Radiation levels vary around the Chernobyl site.

Higher doses of radiation for extended periods of time can be fatal.

This means the time workers spend in the most radioactive places has to be

carefully monitored.

Something project manager Cyril Fargier has experienced firsthand.

The difference of radiation level between this place and really nearby

is huge.

To give you an idea, here a worker can work the whole year and not reach the

limit. Whereas very close to the reactor, working one hour, we would

yearly limit.

The solution the team came up with was to build the structure away from the

reactor.

They identified an area of less radioactive land and planned to carry

main construction here, then move it into position over the reactor.

But even here, the time the workers could spend on site was limited, so the

decision was taken to construct the enormous roof section at ground level.

But by solving one problem, they created another.

Once the top part was built on the ground, the problem was how to lift it.

The heaviest section was around 8 ,000 tons.

With thousands of tons to move and traditional cranes ruled out on safety

grounds, engineers must look to the innovative pioneers of the past for a

solution to this seemingly impossible engineering obstacle.

Physicist Dr.

Andrew Steele is in Munich, Germany, looking for answers that may help the

in Chernobyl.

Almost 50 years ago, The city was preparing to host the upcoming 1972

Games. Wow, check this out.

At the center of the Olympics was this almost 70 ,000 -seater Olympic stadium,

draped in this incredible cable net structure.

270 miles of steel cables were strung between 58 steel pylons.

to support a huge canopy composed of 8 ,000 plexiglass panels.

Although from down here it looks like this roof is just floating over the

making it look this effortless is actually a huge engineering challenge.

The roof was constructed in sections, and each one of those sections weighs

over 1 ,000 tonnes.

The plan was to construct those individual roof sections down on the

and then lift them up into position once they'd been completed.

And this presents quite literally an enormous challenge if you want to try

do it using a crane.

You'd have had to position that crane outside the stadium. And as you can see,

that means it would have had to have been absolutely huge.

Engineers were going to have to devise a radical solution, which had never been

tested at this scale.

Just like the engineers at Chernobyl, the German team needed to find a way to

some heavy lifting.

without using cranes.

In the 1930s, renowned French engineer Eugène Fresenet pioneered the use of

hydraulic jacks as part of his methodology to pre -stress concrete to

longer bridges.

The team in Munich had a theory that the hydraulic jacks that Fresenet used to

apply tension could also be used to lift such an enormous weight.

Engineers decided to use an adapted and relatively untested version of

Fresenet's system known as strand jacking. This was a bold move.

Strand jacking had never been used for a project of this size.

With the opening ceremony of the Games looming, in June 1971, the engineers

their breath as the new technique was tried for the first time on this grand

scale.

And the way that these jacks work is they've got a couple of different

or wedges.

One is fixed at the bottom, and that's going to be represented by my right hand

here. And the other at the top is mobile. It's attached to a hydraulic

that's going to be my left hand.

So if I want to lift that weight down there, the first thing I've got to do is

release this anchor at the bottom.

Then the hydraulic ram does its stuff.

And when that gets to the top of its stroke, the clamp at the bottom grabs

it again, which then means the hydraulic ram can move down, grab on, and then

repeat.

A great advantage of this strand jack system is that you can use them in

conjunction with one another. So if you want to lift a heavier weight, you can

use loads of them together in tandem to get them to do exactly the motion that

you need.

Once completed, the enormous stadium roof covered an area of over 796 ,000

square feet.

At the time, making it the largest cable net structure in the world.

But can the Chernobyl engineers, racing to prevent another radiation leak, use

this technique to solve their giant problem, how to raise the roof?

The Strand Jack is an engineering solution from the 1930s.

But today it's getting a 21st century upgrade.

In Chernobyl, Ukraine, the team needs to raise the enormous arched roof of the

new safe confinement structure.

So they're supersizing Eugene Fresenet's innovation to a scale he never could

have imagined.

So the optimized solution that we chose was to design and fabricate special

lifting towers.

And on top of each tower, we install a platform with jacks.

With the strand jacks positioned on top of the lifting towers, cables with a

high tensile strength are run down to the roof section.

When powered, the jacks pull these cables, lifting the 8 ,800 -ton section

roof.

Its jack had a capacity of maximum 900 tons, and we had over 40 train

jacks activated simultaneously to make this operation.

A computer -controlled system ensures this crucial maneuver is pinpoint

accurate.

All the 10 -lifting power lifts the structure in an evenly way, very

We had tolerance and accuracy every point within a few centimeters.

But to get this accuracy over 260 meters, that's a very high precision.

The next sections of the arch were attached to the roof using giant hinges,

the whole thing was jacked up even higher.

Once it had popped out at 354 feet, it was time to repeat the whole process for

the second part of the arch.

There is excitement when you start an operation like this.

You are even more excited at the end of the day when the mast reaches altitude

and they are secured.

Then everybody is safe and we have completed on time.

It's totally a unique engineering work.

With the framework taking shape, the team still has some serious challenges

ahead. It was the most complex and precise engineering ever envisaged over

a site.

And it's a battle against the clock to prevent another disaster.

Timing was critical to get the reactor covered.

The concern was that it could collapse.

In the Ukraine.

It's a race against time for the international team building the

safe confinement to contain the damaged leaking reactor at the Chernobyl nuclear

power plant.

Costing over $2 .2 billion, the giant arch is large enough to completely

Big Ben.

Mac McNeil heads up the project management team.

Timing was critical to get the arch in place, get the reactor covered.

It is not a stable structure and ultimately the concern was that it could

collapse. Of course, that could release another cloud of radiation, which no one

wanted.

However, before the colossal arch can be moved over the reactor, the structure

has to be sealed.

But finding a suitable material isn't easy.

We need a material that will last 100 years because the deconstruction of the

shelter could conceivably take a very, very long time.

They need something capable of containing some of the most lethal

Earth and that would last a century of extreme conditions in this radioactive

wasteland.

Professor Eric Lima is discovering how a case of one -upmanship led to a major

innovation that could help engineers in Chernobyl. In the 1920s and the 1930s,

the city was gripped by skyscraper fever.

Architects and engineers were outdoing themselves to try to build the highest

buildings.

At the southern end of Manhattan, 40 Wall Street was under construction and

looked set to become the world's tallest building.

But about five miles away in Midtown, automotive tycoon Walter Chrysler had

other ideas.

Okay, what you see is the really cool, iconic building is the Chrysler

It was designed by William Van Allen, right there.

At first, it wasn't on course to be crowned the world tallest.

and he had a plan.

Secretly, he obtained a license to bring a long, tall point, a needle, that he

was going to put on the top of his building.

But the problem was, it's going to be exposed to all the elements, rain, wind,

sleet. How do you make sure it doesn't rust?

It's the same problem facing the engineers in Chernobyl.

So what compound has what it takes to snag the Chrysler building the world's

tallest title?

And safeguard the structure protecting Europe from Chernobyl's nuclear fallout.

For the answer, Van Allen and the new safe confinement team turn to the

innovators of the past.

For the Chrysler Building architect William Van Allen, and for the engineers

behind Chernobyl's new safe confinement project 80 years later,

protecting metal from the elements represents a major concern.

But in 1911, metallurgists Philip Monartz and Wilhelm Borchers built on

advances in non -corrosive steel used in cutlery to create a steel almost

entirely resistant to the elements.

To do this, they added a crucial element to iron alloy,

chromium.

So this scrubby is made of steel.

The main component of steel is iron.

Now when the iron is exposed to oxygen in the air and moisture, there's a

chemical reaction.

That reaction makes iron oxide, otherwise known as rust.

Monerts and Brochere discovered that by adding other elements, most importantly

chromium, To this mixture, they were able to make an alloy that was much more

resistant to corrosion than anything that had come before.

Today, we call that mixture stainless steel.

The chromium added to the alloy reacts with the oxygen to form a film a few

atoms thick.

This protects the material from other oxygen atoms contained in rainwater,

would react with the iron, causing rust.

Days before the grand opening, William Van Allen's fire, encased in this

-edge material, was erected on top of the skyscraper in just 90 minutes,

crowning the Chrysler Building as the tallest in the world, vesting 40 Wall

Street by over 100 feet.

When the Chrysler Building was being constructed... Stainless steel is a

material that's almost completely untested architecturally.

And yet, when you look at it, over 80 years now, it's completely withstood the

trials of time.

In Chernobyl, engineers are putting stainless steel to an even greater test.

protecting the world from another nuclear disaster.

So there are a little more than 87 ,000 square meters of stainless steel

covering the exterior of the arch.

That's why you see the shiny appearance of the arch when you look at it.

The interior is also covered in stainless steel. We don't want this

material to deteriorate.

Sandwiched between two giant spans of stainless steel are multiple layers of

other materials, all carefully chosen to help contain the radiation.

But getting the equivalent of 12 football fields of gleaming stainless

onto the outside of a 354 -foot -high arch isn't easy.

The material actually was put in place using workers that we called alpinists

because they had to be in full, almost mountaineering gear, suspended from the

roof of the arch to put all these in place.

They're absolutely mind -blowing.

With the crucial protective covering in place.

It's time for the most difficult part of the operation.

So how do you move such a vast building in some of the most radioactive

conditions on Earth?

With nearly 40 ,000 tons of steel to move and no margin for error, a single

-off could have disastrous consequences.

It will take some seriously creative engineering and a lot of power to get

critical megastructure into place.

In the Ivankiv district of Ukraine, the massive new safe confinement arch is

ready to move into place over the site of the 1986 Chernobyl nuclear disaster.

If the old reactor building is disturbed, it would have catastrophic

consequences. So it's essential this process runs smoothly.

Project manager Cyril Fargier is on hand for the operation.

So you can see here the skidding beams.

On these skidding beams, we had a Teflon path.

On top of it, we had what we call the skidding shoes.

with a stainless steel interface, which allow a very small friction coefficient

when we're pushing the arch.

But even with the Teflon -coated skidding beams, it still takes a lot of

to move nearly 40 ,000 tons.

That force comes from a technology already used to lift the structure,

jacks. So we had jacks which are pushing horizontally, and also there was jacks

perpendicular to the beam in order to monitor and to compensate any slight

deflection of the beam.

In late 2016, the operation began.

Watching the process was surreal in many respects.

Because you could look at it from a very micro level and you could see the

pistons moving very slowly and the whole arch seemed to object to moving because

the noise it was making was like 10 ,000 fingernails on a blackboard.

Yet when you looked up and saw this enormous structure over it, did you

sort of start to feel the immense engineering that was in these pistons

Basically we were doing up to...

approximately 100 meters per day,

but sometimes less.

It's not a race.

The objective was to do it in safety and in quality and not to create any stress

in this huge structure.

As the structure approaches the old reactor building, it is the tensest

of the operation.

Carefully designed cutouts ensure the end wall clears all the protrusions from

the reactor roof.

So when the arch reached its final position, we were able to complete the

enclosure.

After seven days of painstaking skidding, the structure lands in its

resting place.

Sliding the arch was nerve -wracking, but when it had reached its final

position, I'll confess I did feel a little bit emotional about it because it

such an epic moment.

It's extremely exciting because I believe right now in the world there is

such project so amazing in terms of size, dimension, challenge.

But the team still faces the biggest challenge yet in their quest to put

what once went wrong.

This almost impenetrable barrier stands between the failing nuclear reactor and

the Earth's atmosphere.

But it not only encloses the reactor, it's also designed to dismantle it.

Inside the arch, there are two bridge cranes that go forward and backward

across the whole length of the arch.

The two 315 -foot -long bridge cranes move along the east -west axis.

Hanging from them are three tool platforms, which can move along the

-south axis.

This enables tools to be remotely maneuvered to anywhere in and around the

reactor.

What we have here is the robotic mobile tool platform.

And from this platform will be hung about 10 different tools that can cut,

grind. There's some vacuuming tools, cut grabbing tools.

So this is really the workhorse of the whole new safe confinement because this

is where...

All of the action occurs.

In a sense, it's taking apart a structure very carefully so that you

cause a collapse or further damage to it. You want to take it apart very

methodically, and all of that needs to be well planned. So it will take many,

many years to do that.

As the dismantling process may take over 100 years, The surrounding structure

and machinery need to be able to withstand not only the high levels of

radiation, but any corrosion caused by humidity.

The area most at risk is the giant metal framework.

Unlike the stainless steel covering that surrounds it, this is made from carbon

steel which, if left untreated, could be prone to rust.

So how do engineers protect these metal masses from over a century's worth of

destructive moisture?

For the answer to that question, they must look to a remarkable innovation of

the past.

The dismantling of the Chernobyl nuclear reactor is estimated to take over 100

years. That is, if the new safe confinement containing it lasts that

So on a typical steel building, you would probably have to do a lot of

maintenance of the steel to maintain its erosion resistance.

And here in this structure, we just don't have the opportunity to do that.

You have the radiation conditions. You have this huge volume.

So it is very important that the structure itself be able to resist

for the design life of the arch.

The engineers heading up this project must find a way to protect their massive

structure and the machinery inside.

But what can they use to combat decay?

It's an issue that's been faced in the past.

American chemistry professor Walter A. Patrick patented a method to process

silicon, a chemical element found in sand, to mass -produce silica gel, a

substance which had a quality the U .S. Navy needed after World War II to

preserve its fleet of battleships for future use.

It may also help the team in Chernobyl.

Engineer Dan Dickrell visits the USS Iowa to see how.

This is the USS Iowa, an excellent example of a battleship from the Second

War. She entered service in 1943, saw active combat duty, but was

shortly thereafter and placed into a reserve.

If you look at her, she's in amazing condition, very well preserved.

How is that possible?

For a 75 -year -old, she looks great.

Well, it's all down to this stuff right here, silica gel.

Each silica particle is covered in pores which attract water molecules.

Once all these spaces are taken, it can't hold any more water.

But there is a solution.

When silica is heated, the water is driven away, and it can start trapping

again.

Silica gel plays a huge part in everyday life, keeping food, electronics, and

clothing free from moisture.

It's also a crucial component of the system used to preserve this ship.

Desiccant dehumidifiers draw moist air over a rotating wheel of silica.

This attracts the moisture, allowing dry air to be circulated.

When the wheel turns, the waterlogged silica is exposed to a heating element.

The water detaches and is drained away, and the dry silica can start the process

again.

By installing dehumidifiers on the mothballed ships, the Navy engineers

able to lower the humidity and prevent them from rusting.

Oh, this is the old communication center.

All this stuff is very sensitive to moisture.

Still in actually really good shape.

Thanks to silica, the reserve fleet was kept in great condition and ready for

speedy reactivation.

But the engineers of the new safe confinement have a lot more surface to

dry than the USS Iowa.

The new safe confinement is the largest land -based mobile structure on Earth.

If the structure or its machinery corrode before they finish the century

process of dismantling the failed reactor underneath, the consequences

disastrous.

In Chernobyl, engineers have taken Patrick's method and implemented it on a

much, much bigger scale.

The ductwork you see brings in air that comes in from the outside and is forced

through the dehumidifiers, which then reduce the moisture content of the air.

The key component of the actual drying material is silicon.

This monumental system recirculates over 17 million cubic feet of air every hour

to maintain 40 % humidity, a condition under which carbon steel does not

corrode. If this system weren't here and operating, then the structure of the

arch could be subject to corrosion over a period of years.

The dehumidifiers are the final historic piece of the puzzle that makes this

modern engineering dream a reality.

The new safe confinement is carefully constructed on one of the most

contaminated pieces of land on the planet.

Well, I feel very inspired, slightly humble, and very proud.

You know, it takes a lot of human ingenuity, a lot of good engineering

lot of very thoughtful planning, and always, always attention to safety.

The unprecedented and ambitious project stands as testament to the Herculean

effort of a truly international team.

An immense example of what the international community can do when they

together with a shared objective.

Being a part of that legacy really gives me a feeling that I have contributed

something to the people of Ukraine, to the people of Europe, and perhaps to the

people of the world as well.

By building on the work of the inspirational pioneers of the past,

their ideas and breaking new ground themselves, the engineers have succeeded

making the impossible possible.

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