Building Chernobyl's MegaTomb

Engineers race to build a massive dome to contain the crumbling remains of the reactor. Airing April 26, 2017 at 9 pm on PBS Aired April 26, 2017 on PBS

Program Description

In 1986, in the heart of Ukraine, the Chernobyl nuclear reactor exploded, releasing 400 times more radiation than the Hiroshima Bomb. It was the world’s worst nuclear disaster. Thirty workers died, 50,000 people fled the nearest city, and radioactive fallout made an area larger than Long Island a no-go zone. Hastily, a so-called “sarcophagus” was built to contain the radioactive materials that lingered at the site after the explosion. But 30 years later, the sarcophagus is crumbling, and another disaster at Chernobyl looms. Now, an international team of engineers is racing the clock to assemble one of the most ambitious superstructures ever built—an extraordinary 40,000 ton, $1.5 billion dome to encase the crumbling remains of the Chernobyl nuclear reactor. Battling arctic winter weather—and lethal radiation—this is the inside story of the epic race to build Chernobyl’s MegaTomb.


Building Chernobyl's MegaTomb

PBS Airdate: April 26, 2017

NARRATOR: Today, in the heart of Ukraine, an extraordinary race is underway, to construct a one-and-a-half-billion dollar megadome.

NICOLAS CAILLE (Novarka): It's the biggest moveable structure in the world.

NARRATOR: At 40,000 tons, it will be the largest structure ever moved on land. Its job: to entomb the crumbling remains of the Chernobyl nuclear reactor.

ROB OWEN (Crane System Manager): It is just fantastic, really, really an amazing structure.

NARRATOR: In 1986, in what was the Soviet Republic of Ukraine, the Chernobyl nuclear reactor exploded, releasing 400 times more radioactive material than the Hiroshima Bomb. Thirty workers died; 50,000 people fled the nearest city, and the radioactive fallout spread over Europe. It was the world's worst nuclear accident.

Thirty years later, its hastily built enclosure is crumbling. In a race against time, engineers are struggling to prevent another catastrophic release of deadly radioactive debris into the environment.

IAN CARLING (Cladding Site Engineer): It is extremely dangerous.

JEAN-PHILIPPE GARDEUR (Deputy Construction Manager): Everything we touch, everything we do is completely crazy.

NARRATOR: They're battling freezing weather and lethal radiation, in a desperate race to build Chernobyl's MegaTomb, right now, on NOVA.

Each day, on trains like this, over 1,000 people travel to work at one of Europe's most dangerous and high stakes construction sites. They are heading to Chernobyl, in North Central Ukraine, once part of the Soviet Union.

Here, at the Chernobyl nuclear power station, workers are racing against the clock to build a massive structure. It will enclose the highly radioactive ruins of a nuclear reactor that exploded here over 30 years ago and that remains extremely dangerous, today.

The right half of this building contains the reactor that exploded. The makeshift containment structure over it is collapsing, threatening to release radiation into the environment. To prevent another deadly catastrophe, engineers will entomb it inside a completely new shelter.

But the site is still too radioactive for builders to construct a new cover directly over the old reactor. The only solution is to build the new shelter to the side of the reactor and slide it into position. It will be the largest structure ever moved on land.

The vast scale of the project was what attracted French engineer Nicolas Caille.

NICOLAS CAILLE: It's a big project, with people from everywhere in the world, so, yeah, it is very, very challenging.

NARRATOR: Over 40 countries, including the United States, have contributed a total of $1.5-billion to build the new shelter and finally close a chapter on a disaster that occurred on April 26th, 1986.

On that day, technicians were carrying out a new test on this Soviet-built, water-cooled nuclear reactor. The reactor design was flawed, and the test caused it to run out of control, resulting in a massive steam explosion. The blast killed two workers and blew radioactive uranium fuel onto nearby buildings.

Radiation from the debris and the reactor itself soon killed another 28 people.

NEWS REPORT, VOICE MAN #1: Soviet authorities have been trying to downplay the incident, claiming that there are only two dead and only 150 sent to hospital.

NEWS REPORT, VOICE MAN #2: There are conflicting reports coming out of the Soviet Union. We do know that a zone of deadly radiation has been released.

NARRATOR: The explosion sent six tons of radioactive fuel particles high into the atmosphere above Europe. Where it settled, it contaminated both the land and livestock.

EVACUATION ANNOUNCEMENT, NEWS CLIP, VOICE WOMAN #1: (Translation) Attention! Attention!

NARRATOR: In the vicinity of the reactor, the radioactive fallout forced a third-of-a-million people to evacuate, never to return.

It remains the world's worst-ever nuclear power plant disaster. It left the Soviet authorities with a monumental problem: around 200 tons of shattered uranium fuel rods and other radioactive debris remained inside the damaged reactor building. Left uncovered, it would continually release radioactive dust into the air, a poisonous cloud to threaten the surrounding area.

Over the next six months, workers braved extreme radiation to seal the reactor inside a 300,000-ton shelter, made from steel and concrete. It came to be called the "sarcophagus."

But it was flawed from the start. The extreme radiation prevented the workers from completing the welds needed to seal the prefabricated sections of the sarcophagus together.

Nikolai Steinberg was one of the engineers who built the sarcophagus.

NIKOLAI STEINBERG (Former Chief Engineer, Chernobyl Nuclear Power Plant): They had no time. Every day, every hour, every minute, it was improvisation.

NARRATOR: Even worse, the sarcophagus had no foundations. It simply stood on the ruins of the destroyed reactor. Even as they built it, engineers knew its days were numbered.

NIKOLAI STEINBERG: So, when we completed the sarcophagus we made the decision that the real lifetime of the sarcophagus should be no more than 30 years.

NARRATOR: Now, time is up.

SIMON EVANS (Chernobyl Shelter Fund): These are the world's most uncomfortable boots. I think they preserve these just for occasional visitors.

NARRATOR: Simon Evans is in charge of financing the complex international project. With funding tight, he wants to have the shelter in place as soon as possible, so he needs to know firsthand the condition of the sarcophagus.

Inside the damaged reactor building, Simon's team wears masks to protect them from inhaling radioactive dust.

VOICE MAN #3 (Worker inside reactor building): Don't stop. Don't stop.

NARRATOR: He stops to check some critical devices.

SIMON EVANS: This equipment monitors the stability of the existing shelter, which is absolutely essential to ensure that we know exactly what is going on here.

We know that it's way beyond its design life. It's crumbling. We already had a collapse on one part of the turbine hall, about two-and-a-half years ago, with a very heavy snow load, and did some very major structural damage there.

NARRATOR: In the main reactor hall lies the most deadly debris: the remains of the reactor's uranium fuel rods, radioactive dust and molten material from the core of the reactor. These give off so much radiation, that it shows up as white flashes on video.

None of this must escape, but the sarcophagus enclosing this material, is falling apart. If its roof collapses, it will throw another lethal cloud of radioactive dust out into the atmosphere, where the wind could blow it over the surrounding area.

SIMON EVANS: The collapse of the shelter itself over the old reactor hall is the apocalyptic scenario, which we must avoid. Certainly, it would release another major release of radiation into the environment.

NARRATOR: Six years after the sarcophagus was built, the Ukrainian government held a competition for ideas for a new containment structure, to make the Chernobyl reactor safe.

NICOLAS CAILLE: They received, probably, 200 different ideas. And they selected five of them. And it took approximately 10 years to decide which idea would be the best, which idea can be constructed. And in 2007, we won the project, and we signed the contract 20 years after the accident.

NARRATOR: The winning plan, from the French construction consortium Novarka, is very ambitious.

About 300 yards away from the reactor, where radiation levels are low enough for builders to work safely, they will construct two halves of a giant steel arch, 30 stories high. They will mount them on two concrete runways that extend alongside the crumbling sarcophagus. Next, they will slide the two halves of the arch together to make one enormous structure. Inside the ceiling of the arch, they will attach two giant robotic cranes. Once complete, engineers will slide the vast arch over the reactor.

Then, in the future, the remotely-controlled robot cranes inside the arch will dismantle the old sarcophagus and remove the remains to a yet-to-be-built storage facility. This part of the plan has not been worked out.

In spring, 2012, workers start to assemble the steel tubing that will form the giant skeleton of the arch. They will use over half-a-million bolts to join it together.

NICOLAS CAILLE: It will be a complicated task. To erect 36,000 of tons, it's quite challenging.

NARRATOR: They will build the first half of the arch from the top down, using jacks mounted on towers to raise it, in a series of massive lifts.

NICOLAS CAILLE: You have a lift of 30 meters, and then you build below, and the structure is going up, up, up, up, up.

NARRATOR: It takes three lifts to raise the arch to its full height of 350 feet. Now, they must bolt on the steel tubes that will form the sides of the structure.

Once they have built the first half of the arch, they will slide it to one side of the worksite to make enough space to construct the second half.

Building it this way enables the construction crew to keep a safe distance from the destroyed reactor, where the radioactive materials left inside present the most danger to the workers.

The remains of the uranium fuel emit deadly radiation. The most dangerous are gamma rays. Gamma rays, like X-rays are made of high-energy photons and can travel long distances. Some of these, pass through the reactor walls and stream out into the surrounding space. Most will pass straight through a human body, but some will interact, damaging cells and fragmenting D.N.A., which can cause cancer.

The dangers are very real. In 1986, when the Chernobyl reactor exploded, it exposed workers and firefighters to high levels of gamma radiation. In the following weeks, 28 workers died from acute radiation sickness.

Every year, on the anniversary of the disaster, the people of Slavutych, the town where most Chernobyl workers now live, remember those who lost their lives.

Viktor Ivkin was working at the reactor that night. Like many others, he received a large dose of radiation.

VIKTOR IVKIN (Survivor, worked at the reactor, was there the night of disaster): (Translation) By this time, I had already vomited a couple of times, and if a person shows this reflex, that means they've absorbed over 100 roentgens.

NARRATOR: One hundred roentgens is over 900 times the maximum amount of radiation considered safe to receive over an entire year.

VIKTOR IVKIN: (Translation) Many of the chaps from that shift died. I wish there were more of us left. Every year, we're becoming fewer and fewer. It's very sad.

NARRATOR: Today, inside the old sarcophagus, 95 percent of the uranium that was in the reactor before the explosion lies scattered and exposed.

Here, close to the sarcophagus, the high number of gamma rays makes it too dangerous to work for the long periods of time needed to construct the arch.

But the engineers have one thing on their side. As the gamma rays leave the reactor, they get further apart from each other, and some are absorbed in the air. So, for every 1,000 gamma rays passing through a person standing 30 yards from the radioactive source only about one will pass through a worker standing 300 yards away, where they are building the arch.

Radiological engineer Nicolas Guilcher measures the radiation across the site.

NICOLAS GUILCHER (Radiation Protection Engineer at Novarka): You can see, here, the reactor Number 4, which was damaged in ‘86, and at about 200 meters from the reactor, the platform where the arch will be built. So, you can understand that if you are going further from the reactor, the dose rates are lower.

NARRATOR: A special unit of 50 people checks the daily amount of radiation every construction worker receives.

DAVID DRISCOLL (Health and Safety Manager): We provide everybody with dosimeters. I have the French national dosimeter; I have a Ukrainian national dosimeter; and then we also have an electronic dosimeter that is our operational dosimeter.

NARRATOR: The dosimeters ensure no worker receives more than their annual permitted dose of radiation, so, every aspect of the construction must be designed with this in mind, including the arches.

NICOLAS CAILLE: We have decided to build 300 meters away, because we can work as much as we want: 10 hours a day, eight hours a day, the full week, the full year.

NARRATOR: There's another challenge that makes this already complex project even tougher, the lack of time. The hastily built sarcophagus covering the reactor could collapse at any moment.

JEAN-PHILIPPE GARDEUR: Good morning, all. This is a jacking and lifting, so, I will ask you to not stand under the load, if you don't need to be under the load.

NARRATOR: The lifting team needs to work fast, to complete the arch on schedule.

Jean-Philippe Gardeur is gearing up for the final lift, to raise the second half of the arched enclosure to its full height.

JEAN-PHILIPPE GARDEUR: Everything on this field is huge, is enormous, you know? We don't have small things. Everything we touch, everything we do, is completely crazy.

Nice to hear this noise, hey?

NARRATOR: It will take 40 huge jacks to raise this metal monster.

BJORN-EVERT VAN ECK RASMUSSEN (Engineer): That's going to be very tight, that's for sure. But we will see.

NARRATOR: Each jack has enough power to lift over two loaded jumbo jets.

JEAN-PHILIPPE GARDEUR: Okay, guys, so we will start the jacking now.

We start, so we have to try to reach the target of finishing the jacking today.

SEVERAL MEN IN CONTROL ROOM: Quickly, quickly, quickly. Seven, eight, five millimeters.


NARRATOR: Success. But the team can't afford to relax.

If the sarcophagus collapses before the arch is in place, the fallout would contaminate the arch and the whole worksite. It would undo the years of work spent cleaning up the area, a process which began immediately after the accident and that came with a heavy loss.

After Chernobyl exploded, it spewed radioactive dust onto the surrounding countryside. The Soviet authorities declared a 19-mile-radius exclusion zone around the reactor. They drafted 350,000 people to clean up the radioactive fallout.

They were called "liquidators."


NARRATOR: At the center of the hot zone, they cleared the radioactive debris from the roof of the exploded reactor. Some only had 45 seconds to perform their task, before their dose of radiation became too great.

In the surrounding area, they washed down surfaces to remove the radioactive dust. They bulldozed and buried the most contaminated homes, along with over a million tons of contaminated soil.

Among the liquidators was Ivan Martynenko.

IVAN MARTYNENKO (Chernobyl Liquidator): Our first assignment was to build a special decontamination center for washing vehicles and people.

They told us that if we were exposed to the level of 10 roentgens, we would be honorably discharged. It was a lie. Even when we had that sort of exposure, they said there are no units to replace us.

NARRATOR: The World Health Organization estimates that more than 2,000 liquidators have died, or will die, as a result of the radiation they received. No one wants a repeat of this disaster. To prevent one, it's essential the arch is completed as quickly as possible.

Two and a half years after construction began, it's late fall, and engineers are anxious to entirely cover the shelter's enormous roof before the winter storms hit.

IAN CARLING: The biggest problem we have is the weather. It's the biggest, biggest problem on here. For the winter period, we can lose three months, four months of the year.

NARRATOR: British engineer, Ian Carling, is in charge of constructing the roof of the arch. In Ukraine's harsh climate, that's a daunting challenge. Winter temperatures here can plunge to minus-20 degrees Fahrenheit.

IAN CARLING: Today, we had the wind problem. Yesterday, we had ice on the roof, so we could not work. We lost a whole morning yesterday just through the ice on the roof alone.

NARRATOR: Ian's team must work 350 feet above the ground. That's more than 30 stories high.

IAN CARLING: This job, it's extremely dangerous: the winds, the rains. It makes the surfaces that we're working on very slippy.

NARRATOR: The roofers are all trained rope-access technicians, but the dangerous conditions here require both skill and absolute concentration.

IAN CARLING: Some of the materials that we're using, they can act like&hellipa kite, if you like. You can imagine a sail in the air, and the material is razor sharp. So, it's very, very dangerous. So, yes, we have to be very, very careful.

NARRATOR: Even when its roof is complete, the arch will be far from finished. Before they slide it over the reactor, engineers must transform it into a machine designed to deal with Chernobyl's radioactive debris.

The radioactive material inside the reactor will remain dangerous for at least 20,000 years. If engineers simply covered the reactor with the arch and did nothing else, they would only be adding to the problem. In time, like any building, the arch would eventually collapse, and a future generation would need to build another, even bigger structure to keep the reactor safe.

To prevent this, engineers must design a system within the arch to clean up the destroyed reactor. The process will require a series of difficult steps.

NICOLAS CAILLE: We have to provide tools to enable the deconstruction. We have to remove the sarcophagus built by the Russians. So, first of all, it is to remove the roof over the exploded reactor. And then, after, they will have to break the concrete. And at the end, remove the fuel, the heart of the reactor.

It will take a long time. Our arch is warrantied for 100 years, so at the maximum, they can take 100 years.

NARRATOR: No one has attempted to dismantle an exploded nuclear reactor before. Radiation makes the job too dangerous to do by hand, so the workers must rely on tools operated at a distance.

In Shoreview, Minnesota, Rob Owen leads the team building a special remote-control crane to dismantle the reactor.

ROB OWEN: The fuel that was there is still there, but when they start to dismantle the sarcophagus, you're going to expose that fuel. And as it gets exposed, the level of radiation will get much, much higher than it is today.

NARRATOR: Rob is testing a quarter-scale model of the remote-controlled crane that will be installed inside the new shelter. It uses an ingenious system of wires to carry a platform holding a robotic arm. The configuration of the wires is crucial. If the platform was supported by vertical wires, it would swing, but using three pairs of wires arranged in triangles and adding a heavy weight makes it rigid.

It has one drawback: a strong side force could move the platform up and slacken some of the wires. But if the weight on the platform is heavy enough, all the wires will stay tight, and the platform will remain rigid enough to hold the robot arm that will dismantle the sarcophagus.

ROB OWEN: We kind of had to really go back and study the design. Would it work here? Could we make it big enough? It had to be considerably larger than anything that has ever been built, but the idea was really intriguing, because of all the pluses.

NARRATOR: To drill into walls or pull a beam, the robotic arm must be able to push and pull horizontally.

ROB OWEN: We have the six wire ropes and a lot of weight here, as you can see, on the bottom. All the cables remain in tension. It provides that stiffness that allows you to do pushing, pulling.

NARRATOR: The model demonstrates that the concept works, but it must be tested at full scale. If successful, this special crane will be deployed alongside conventional cranes to dismantle the damaged reactor.

The job will take decades, and this creates another major design challenge for the engineers building the arch.

NICOLAS CAILLE: It must last 100 years. The metallic structure cannot last 100 years. You have to protect the structure and repaint it. I mean, as I'm French, I take the example of the Eiffel Tower, which is repainted every seven to 10 years.

NARRATOR: Painting the steel arch protects it for a time, but, eventually, the paint will degrade, exposing the metal to moisture in the air, causing it to rust.

DAVID COULET (Site Manager): This steel structure has been painted in the factory. This paint will last 15 years. Unfortunately, we will not be able to renew it once the arch will be in the final position, because the radiation conditions at that location are too severe for a painter.

NARRATOR: In its final position over the reactor, the arch will be impossible to repaint. To solve this problem, they're engineering the steel to be inside a special climate-controlled environment. The gap between the arch's exterior roof and interior ceiling will be sealed, creating a vast enclosed space around the steelwork.

Powerful fans will pull in air from outside, channel it through massive dehumidifiers to remove moisture, then blow the dried air along two miles of aluminum ducts, into every corner of the enclosed space. The ducts will constantly recirculate the dry air to make sure that the atmosphere in the enclosure remains dry, so the steelwork doesn't rust.

For the plan to work, Ian Carling must ensure the interior ceiling is completely sealed.

IAN CARLING: Horosho. Spasibo. (Translation) "Good. Thanks."

We have some junctions here, so, because of this gap, we have to do a compressed sealant, which makes the air seal tight.

NARRATOR: But the siding here, known as cladding, has another important job. When the cranes dismantle the old reactor, they will throw up clouds of radioactive dust.

IAN CARLING: This cladding, it's stainless steel, and it is designed for the purpose of containing any airborne contaminated particles from escaping into the environment, during the dismantling of the reactor Number 4.

NARRATOR: Spring 2016, the massive cranes have arrived from America. Before engineers slide the arch over the reactor, they must install them and the carriage that will carry the robotic arm.

Baptiste Briois is the engineer in charge. Today he has a 26-story climb to the control room.

BAPTISTE BRIOIS (Engineer): Three-hundred-sixty-nine. Three-hundred-sixty-nine stairs. Twice a day.

Everyone in position? Everything's ready? We can start.

NARRATOR: The team relies on 13 hydraulic jacks, fixed near the top of the arch, to lift the 900-ton crane into position. Inside the jacks, hydraulic jaws grip the wires attached to the crane and slowly hoist them up.

BAPTISTE BRIOIS: It's coming closer and closer. I like it.

NARRATOR: But just as the crane lifts off, they hit a glitch.

BAPTISTE BRIOIS: Apparently, we have a little problem with the strand carousel.

NARRATOR: As the wires leave each jack, they should coil around a carousel, but on one, the lifting wires are tangling.

Working 300 feet above the ground, it's a precarious operation to wrestle the wires back into place.

BAPTISTE BRIOIS: It was very quick. They are very efficient. So, we can still finish today.

NARRATOR: Now engineers can start tests on the full-scale crane.

TONY DELAPORTE (engineer): Now we can lift?

ELENA OBI (commissioning engineer at Novarka): Yes, we can lift. Yes.

NARRATOR: Once the shelter has been moved into position over the old reactor, this crane, yet to be fitted with its robotic arm, will start dismantling the ruins of the Chernobyl reactor. It will be the final step in the long operation to seal the reactor away and make the site safe.

But then they will face a problem that bedevils the entire nuclear industry: where to store the radioactive waste.

Today, more than 30 years after the Chernobyl disaster, the 19-mile exclusion zone around the reactor is still a restricted area. But, aside from the absence of people and a few warning signs, there is little indication that large amounts of radioactive material fell on this land.

Nature has reclaimed the empty human settlements. Two miles from the reactor lies the abandoned city of Pripyat. Fifty-thousand people once lived here, many of them workers at the nuclear plant.

VIKTOR IVKIN: There were roses everywhere. There was a lot of greenery, and many young people, and the river flowing right through the city. It was just great. We remember the place as clean, beautiful and bright.

NARRATOR: High levels of radioactive debris contaminated this city. Like other areas inside the zone, it will remain uninhabitable for hundreds of years. For decades, the authorities have used the zone as a dumping ground for contaminated machinery from the clean-up operations. Now, they are building a facility here for storing radioactive fuel and waste from the reactors at Chernobyl and from other plants in Ukraine.

Storing nuclear waste has challenges of its own, and this ambitious plan for the future has yet to be entirely mapped out. With winter approaching, the team is working to a tight deadline. The workers have just 11 days to prepare to move the arch.

DAVID DRISCOLL: We're coming to the end. We're preparing for the skidding of the arch over the reactor. At last, this huge thing is built and it's going to move to where it should be.

NARRATOR: For the engineers, this is the last chance to make sure everything works.

DAVID DRISCOLL: There's a lot more activity, because we now have many more tasks to complete, all in the same period.

NARRATOR: One remaining job is crucial before they slide the arch, opening its enormous special doors. To stop radioactive dust from escaping, the arch must form a perfect seal around the old reactor building. But parts of the old sarcophagus stick out, which would prevent the arch from sliding to its final position.

So, engineers have equipped the arch with tilting panels, like giant cat doors, that they must raise and then lower into place when the arch is in position, sealing the small remaining gap with an extra-durable plastic membrane.

Just as the team is raising the heaviest panel, a blizzard strikes. Despite the weather, the engineers must press on. They operate the panels remotely from a platform on one side of the arch.

DAVID COULET: We have six tilting panels, and the largest one is 320 tons. So, once the arch will have reached its final location, the radiation conditions do not allow a manned operation at that location. So, we have designed a system of hydraulic jacks, a system of winches, to close this panel, remotely.

NARRATOR: It takes four hours to winch the massive "cat door" open. Four-and-a-half years after work began, to build the 40,000-ton shelter, the day finally arrives when the team will attempt to slide it over the reactor.

It will be the largest structure ever moved across land.

NICOLAS CAILLE: Now, we are almost at the end. We are under pressure. It's a great challenge because of the size. I am also thinking of myself. I have already a lot of white hair, and the sooner it will be finished, the better it will be for me.

NARRATOR: Moving this massive structure will be no simple task. The obvious way to move a monster arch would be on wheels, but that won't work here.

The arch is so heavy, that it would overload the wheel bearings, which would fracture, leaving the structure stranded. So, instead of wheels, engineers will use a hundred-and-sixteen stainless steel feet, known as skid shoes. These will slide on Teflon pads, placed on top of the rails.

Geert-Jan Thijssen leads the team that will move the arch.

GEERT-JAN THIJSSEN (Mammoet): Over these nooks, we put the Teflon pad. And, basically, if you put a lot of them, you make your own sliding way for the skid shoes to slide on.

NARRATOR: The pads are made of P.T.F.E., the polymer used on non-stick cookware. This low-friction surface will help the stainless steel feet of the arch to slide.

To push the arch, engineers will fit each leg with hydraulic pistons. These move a pair of wedges that grip the steel rail. Powerful pumps will then extend the pistons, to push the arch forward. More than 200 pistons must work in perfect unison to slowly slide the arch towards the reactor.

NICOLAS CAILLE: This is a one-off skidding. I mean you can't go back. So, you should be sure that you haven't forgotten anything.

NARRATOR: This is the critical maneuver everyone has been working towards for seven years.

VOICE MAN #1 IN CONTROL ROOM: We have the confirmation that we are ready.


NICOLAS CAILLE: Allez, allez. Le top. On y va.

BAPTISTE BRIOIS: On y va. Okay. We go.

NARRATOR: The pistons fire up. Two-thousand tons of force pushes against the arch.

NICOLAS CAILLE: Okay. Rolling.

NARRATOR: And they're off. The vast structure, as heavy as three-and-a-half Eiffel Towers, slides towards the reactor at about 33-feet-an-hour. Even if all goes well, it will still take six long days.

It's crucial that the pistons move both sides of the arch at the same speed. To make sure they don't twist the arch, lasers measure the exact position of both sides and display any difference on screens in the control room.

GEERT-JAN THIJSSEN: If you move one side faster than the other, you will get bending in the arch, which can lead to damage of the arch. And if we go too far from each other, then, you see, the deviation between the two gets too high, and then we have to adjust and move forward to correct the readings we get on the system.



GEERT-JAN THIJSSEN: That's the difficult part. You get so much data you have to act correctly and quickly.

NARRATOR: The closer they get to the reactor, the more difficult the operation becomes. Sliding the arch over the reactor walls will be tight.

GUILLAUME MOREL (General Methods Coordinator): People will follow the sliding, itself, of the arch. Eighty, ninety people will be involved. We have a lot of watchmen, because our clearance is very limited. The clearance that we have is quite tight; it's 50 centimeters.

INTERVIEWER: What could go wrong during the skidding?

GUILLAUME MOREL: Nothing, everything should be fine.

NARRATOR: But just as the arch approaches the reactor, they run into trouble. It becomes snagged on a barbed wire fence.

The radiation here is high, so they must act fast.

NICOLAS CAILLE: There is two rebar that are touching the arch. So we are sending somebody with a saw to remove these rebar, to be sure we are not damaging the arch.

NARRATOR: With the wire removed, there's one last task before the final push. They must partially lower one of the tilting panels. If they wait until the arch is in position, then, as they close it, it would jam on a chimney.

NICOLAS CAILLE: It will hit the chimney. So, we have to tilt it before, and then we can restart to the end and finish it tonight.

Vitaly, yes. Go. Go.

NARRATOR: The panel clears the chimney and the final push begins. After seven days of pushing, the arch is finally in position over the reactor.

NICOLAS CAILLE: It's a feeling of pride. We have achieved something great. It's a big step for safety. And Ukraine and Europe will be much safer now.

NARRATOR: In the coming years, the cranes with the robotic arm attached will start the dismantling process.

It has taken 18 years of planning, seven years of construction, and a unique international collaboration of 10,000 men and women from 30 countries, but three decades after the world's worst nuclear accident, Chernobyl is finally sealed away, for generations to come.

Building Chernobyl's MegaTomb – Extra Scenes

1. Wildlife in the Exclusion Zone

NARRATOR: After the Chernobyl disaster, the authorities set up a 19-mile-radius exclusion zone around the destroyed reactor. Thirty years on, ecologist Mike Wood is investigating what types of animals live in the zone and if the levels of radiation affect where they live.

MIKE WOOD (Ecologist, University of Salford): At the time of the accident, depending on which direction the wind was blowing and whether or not there was rainfall, you got different amounts of radioactive fallout in different parts of the exclusion zone.

NARRATOR: Mike is setting up camera traps in three different areas, places with high, medium and low radioactive contamination. The traps will photograph any large mammal that moves in front of the lens.

MIKE WOOD: We're hoping to be able to understand more about the way in which the range of large mammal species that we see is, or is not, influenced by the radiation levels.

NARRATOR: By placing traps at 84 randomly chosen sites in each area, Mike hopes to discover how many different species of large mammals live in each place.

MIKE WOOD: When we put the cameras out, we take a G.P.S. reading of the location of the camera, and then we can use handheld G.P.S., like this, to be able to find the cameras again, and then come and see what it's recorded.

So, let's have a look at this.

NARRATOR: The cameras reveal an astonishing variety of life.

MIKE WOOD: So, we can see that we've got an elk here and wild boar, as well. We see quite a range of animals on most of the cameras that we bring back in: red deer, wolves, lynx, Eurasian lynx, and, also, European bison, as well.

In the high contamination areas and in the low contamination areas, there doesn't seem to be a difference in the range of species that we see.

NARRATOR: It appears that, thanks to the absence of humans, some animals are thriving in the exclusion zone.

2. The Telescopic Tube

NARRATOR: Engineers must equip their new shelter with the tools to dismantle the ruined reactor. The initial plan was to install two bridge cranes on the ceiling of the new arch. On one, they will attach a giant telescopic tube equipped with a robotic arm. This would allow them to pull the structure apart piece by piece, load the debris into sealed trucks and take the radioactive waste to storage.

At least, that was the theory.

In Minnesota, Rob Owen leads the team designing the dismantling system.

ROB OWEN: The first work that we did was actually doing some studies of the telescoping tube. Because of the enormous size that they had envisioned, they wanted some verification that it was possible.

NARRATOR: But when Rob and his team studied the telescopic tube, they hit a problem: its length.

ROB OWEN: This is at least twice as long, if not more, than we had ever done. And it also had to carry a tremendous payload at the end.

NARRATOR: To reach all the way from the ceiling of the arch to its working height on the sarcophagus, the telescopic tube would have to be massive, and that weight is the problem.

The danger comes from earthquakes. Although Chernobyl isn't in a seismic area, it is only 400 miles from the Vrancea zone in Romania, one of the most active seismic areas in Europe. A large earthquake here would be felt in Chernobyl. It would shake the heavy tube, generating extreme forces that could damage the arch.

ROB OWEN: The weight of the telescopic tube just kept growing and growing; it would just be outrageous.

NARRATOR: The telescopic tube was out, so the team went back to the drawing board. They knew they needed something lighter and less rigid. The solution was to replace the tube with a platform supported on wires. It was called a Tensile Truss.

Broadcast Credits

Martin Gorst
Carlo Massarella
Paul Shepard
Eric Meyers
Peter Fison
Justin Ingham
Roshan Samarasinghe
Mat Stimpson
Alex Tate
Gwyn Williams
Dmytro Kolchynsky
Anatolii Kuksa
Taras Shumeyko
Emma Houghton-Brown
Katie Reisz
Mel Moore
Vicky Newman
Sara Revell
Pete Youens
Fluid Pictures
Paul Goodman
Barrie Pease
Vicki Matich
Paul Fallon
Andy Hodges
Bob Jackson
Philip Michael
EBRD / Novarka
KBJR Metro News 6
Sergei Koshelev
Professor Stuart Burgess
Laurin Dodd
European Bank for Reconstruction & Development
Dr. Alan Flowers
Mac McNeil
Birte Pedersen
Leesa Rumley
Sue Harvard
yU + co.
Walter Werzowa
John Luker
Musikvergnuegen, Inc.
Ray Loring
Rob Morsberger
The Caption Center
Spencer Gentry
Jennifer Welsh
Eileen Campion
Eddie Ward
Ana Aceves
Caitlin Saks
Anne Barleon
Linda Callahan
Cory Allen
Sarah Erlandson
Janice Flood
Susan Rosen
Kristine Allington
Tim De Chant
Lauren Aguirre
Lauren Miller
Brittany Flynn
Kevin Young
Michael H. Amundson
Nathan Gunner
Ariam McCrary
David Condon
Pamela Rosenstein
Elizabeth Benjes
Evan Hadingham
Chris Schmidt
Melanie Wallace
Laurie Cahalane
Julia Cort
Paula S. Apsell

A NOVA production by Windfall Films Ltd. (part of the Argonon Group) for NOVA/WGBH Boston in association with the BBC, and France Television, NHK, and N24

© 2017 WGBH Educational Foundation

All rights reserved

This program was produced by WGBH, which is solely responsible for its content.

Original funding for this program was provided by Cancer Treatment Centers of America, 23andMe, The David H. Koch Fund for Science, and the Corporation for Public Broadcasting.


Image credit (construction of New Safe Confinement)
© WGBH Educational Foundation


Baptiste Briois
Nicolas Caille
Ian Carling
Cladding Site Engineer
David Coulet
Site Manager
David Driscoll
Health and Safety Manager
Simon Evans
Chernobyl Shelter Fund
Jean-Philippe Gardeur
Deputy Construction Manager
Guillaume Morel
General Methods Coordinator
Rob Owen
Crane System Manager
Nikolai Steinberg
Fmr. Chief Engineer, Chernobyl Nuclear Power Plant
Geert-Jan Thijssen

Preview | 00:30

Full Program | 52:55

Full program available for streaming through

Watch Online
Full program available