0:00:04 > 0:00:07Today, in Ukraine, an international team of engineers
0:00:07 > 0:00:09is racing to assemble
0:00:09 > 0:00:13one of the most complex superstructures ever built.
0:00:13 > 0:00:17It's the largest structure that will have moved on land.
0:00:17 > 0:00:24An extraordinary 36,000-tonne, £1.2 billion mega dome.
0:00:24 > 0:00:27Its job, to entomb the crumbling remains
0:00:27 > 0:00:30of the Chernobyl nuclear reactor.
0:00:30 > 0:00:35It's just fantastic. Really, really an amazing structure.
0:00:36 > 0:00:41In 1986, the Chernobyl nuclear reactor exploded,
0:00:41 > 0:00:46releasing 400 times more radiation than the Hiroshima bomb.
0:00:47 > 0:00:50It was the world's worst nuclear disaster.
0:00:51 > 0:00:5630 workers died. 50,000 people fled the nearest city.
0:00:57 > 0:01:01And radioactive fallout turned an area larger than Lancashire
0:01:01 > 0:01:02into a no-go zone.
0:01:04 > 0:01:0730 years on, as scientists investigate
0:01:07 > 0:01:09the true impact of the disaster...
0:01:09 > 0:01:12It's given wildlife an opportunity to move back in,
0:01:12 > 0:01:14for their numbers to increase.
0:01:14 > 0:01:18..the shell of the nuclear reactor is collapsing.
0:01:19 > 0:01:20Engineers must battle
0:01:20 > 0:01:24to stop another escape of deadly radiation...
0:01:24 > 0:01:26It is extremely dangerous.
0:01:27 > 0:01:30Everything we touch, everything we do, it is completely crazy.
0:01:32 > 0:01:36..fighting freezing weather and lethal radiation.
0:01:37 > 0:01:44This is the inside story of the race to build Chernobyl's mega tomb.
0:02:10 > 0:02:12These are the world's most uncomfortable boots.
0:02:12 > 0:02:15But I think they preserve these just for occasional visitors.
0:02:17 > 0:02:21Simon Evans is one of the world's most unusual bankers.
0:02:22 > 0:02:26He is overseeing the funds for a project that will clean up
0:02:26 > 0:02:30and make safe one of the most deadly places on earth.
0:02:31 > 0:02:35The Chernobyl nuclear power plant in Ukraine.
0:02:41 > 0:02:44BEEPING
0:02:44 > 0:02:48If you spend too long in some parts of this building,
0:02:48 > 0:02:50the radiation will kill you.
0:02:51 > 0:02:53Don't stop, don't stop.
0:03:12 > 0:03:14We are in the control room of Reactor 4,
0:03:14 > 0:03:16where just over 30 years ago,
0:03:16 > 0:03:18they conducted a safety test
0:03:18 > 0:03:20on April 26, 1986,
0:03:20 > 0:03:22and it went catastrophically wrong,
0:03:22 > 0:03:24and there's the consequences we're all too familiar with.
0:03:28 > 0:03:32At 1.23 in the morning inside this Soviet-built reactor,
0:03:32 > 0:03:37a runaway nuclear reaction created a massive steam explosion.
0:03:40 > 0:03:42The blast killed two workers,
0:03:42 > 0:03:46and blew radioactive uranium fuel onto nearby buildings.
0:03:50 > 0:03:53Radiation coming from this and the destroyed reactor
0:03:53 > 0:03:55killed a further 28 people.
0:03:57 > 0:03:59- NEWSREEL:- 'Soviet authorities have been trying
0:03:59 > 0:04:01'to downplay the incident, claiming that there are
0:04:01 > 0:04:03'only two dead and only 100...'
0:04:03 > 0:04:05- NEWSREEL:- '..reports coming out of the Soviet Union.
0:04:05 > 0:04:09'We do know that a zone of deadly radiation has been released...'
0:04:09 > 0:04:12The explosion sent 50 tonnes of nuclear fuel
0:04:12 > 0:04:14high into the atmosphere.
0:04:15 > 0:04:18The wind blew it across Europe.
0:04:18 > 0:04:24Where it settled, it contaminated both the land and animals.
0:04:26 > 0:04:30In the UK, sheep reared in parts of Wales and Cumbria
0:04:30 > 0:04:34were declared unfit for human consumption.
0:04:39 > 0:04:43Close to the reactor, the radioactive fallout
0:04:43 > 0:04:47forced a third of a million people to evacuate their homes,
0:04:47 > 0:04:49never to return.
0:04:51 > 0:04:53It was and remains
0:04:53 > 0:04:56the world's worst ever nuclear disaster.
0:04:56 > 0:04:59HE SPEAKS RUSSIAN
0:05:01 > 0:05:02After the dust settled,
0:05:02 > 0:05:05the Soviet authorities faced a monumental problem.
0:05:09 > 0:05:12Over 200 tonnes of radioactive material
0:05:12 > 0:05:15remained inside the damaged reactor building.
0:05:17 > 0:05:22Left unchecked, wind would blow the radioactive dust into the air.
0:05:30 > 0:05:32Over the next six months,
0:05:32 > 0:05:35workers battled extreme radiation
0:05:35 > 0:05:38to seal the reactor inside a 300,000-tonne shelter
0:05:38 > 0:05:40made from steel and concrete.
0:05:43 > 0:05:45It was called the sarcophagus.
0:05:50 > 0:05:54Once it was complete, the world breathed a sigh of relief.
0:05:55 > 0:05:56Everything seemed safe.
0:06:02 > 0:06:05But the engineers who built the sarcophagus
0:06:05 > 0:06:07knew it was a temporary fix.
0:06:09 > 0:06:15Today, 30 years after it was built, the shelter is falling apart.
0:06:28 > 0:06:30This equipment monitors the stability
0:06:30 > 0:06:33of the existing shelter, which is absolutely essential
0:06:33 > 0:06:35to ensure that we know precisely what's going on here.
0:06:35 > 0:06:39We know that it's way beyond its design life. It's crumbling.
0:06:39 > 0:06:42We've already had a collapse in one part of the turbine hall
0:06:42 > 0:06:45about two and a half years ago, with a very heavy snow load,
0:06:45 > 0:06:47and you see some very major destruction and damage there.
0:06:52 > 0:06:55This is the most radioactive area.
0:06:55 > 0:06:58The hall that once contained the reactor.
0:07:11 > 0:07:16The remains of nuclear fuel rods and the molten core of the reactor
0:07:16 > 0:07:20give off so much radiation that visits here are limited to seconds.
0:07:23 > 0:07:25Holes in the roof are clearly visible.
0:07:27 > 0:07:31The collapse of the shelter itself over the old reactor hall
0:07:31 > 0:07:34is the apocalyptic scenario which we must avoid.
0:07:34 > 0:07:35Certainly, it would release
0:07:35 > 0:07:38another major release of radiation into the environment.
0:07:38 > 0:07:40BEEPING
0:07:40 > 0:07:43The sarcophagus is a toxic time bomb.
0:07:43 > 0:07:45Don't stop, Dermot.
0:07:48 > 0:07:50To make the site safe,
0:07:50 > 0:07:54today engineers need to entomb the crumbling sarcophagus
0:07:54 > 0:07:56inside a completely new shelter.
0:08:00 > 0:08:02There's just one problem with this idea.
0:08:04 > 0:08:09The site is still too radioactive for builders to construct
0:08:09 > 0:08:12a new cover directly over the old reactor.
0:08:15 > 0:08:18So they have devised an ambitious scheme
0:08:18 > 0:08:22to build a new shelter to one side of the reactor,
0:08:22 > 0:08:24then move it into position.
0:08:26 > 0:08:28This is their grand plan.
0:08:32 > 0:08:34300 metres away from the reactor,
0:08:34 > 0:08:36where radiation levels are low enough
0:08:36 > 0:08:38for builders to work normally,
0:08:38 > 0:08:42they will construct two halves of a giant steel arch
0:08:42 > 0:08:44taller than Big Ben.
0:08:45 > 0:08:48They will mount them on two concrete runways,
0:08:48 > 0:08:51running either side of the crumbling sarcophagus.
0:08:55 > 0:08:58Then, they will slide the two halves of the arch together
0:08:58 > 0:09:01to make one enormous structure.
0:09:04 > 0:09:06Inside the ceiling of the arch,
0:09:06 > 0:09:09they will attach two giant robotic cranes.
0:09:12 > 0:09:16Next to the reactor, they will construct a nerve centre
0:09:16 > 0:09:20to provide the power, ventilation and control systems for the arch.
0:09:23 > 0:09:28Once complete, engineers will slide the vast arch over the reactor.
0:09:32 > 0:09:36It will be the biggest structure ever moved across land.
0:09:38 > 0:09:43Over time, the remotely controlled robot cranes inside the arch
0:09:43 > 0:09:47will dismantle the old sarcophagus
0:09:47 > 0:09:49and remove the remains of the exploded reactor...
0:09:51 > 0:09:53..making the site safe.
0:09:57 > 0:10:02It's a trailblazing scheme that will cost more than £1.2 billion.
0:10:03 > 0:10:07It will be funded with grants from countries all over the world.
0:10:09 > 0:10:11We're not really a normal bank.
0:10:11 > 0:10:15We have over 40 international donors supporting our work,
0:10:15 > 0:10:18representing the fact that it was an international accident
0:10:18 > 0:10:21and it's an international solution to that problem.
0:10:27 > 0:10:30THEY LAUGH AND CHAT INDISTINCTLY
0:10:34 > 0:10:39Since 2010, up to 1,200 people have travelled in
0:10:39 > 0:10:42to work at the Chernobyl site each day.
0:10:50 > 0:10:54The ambitious project has attracted an international team of engineers.
0:10:57 > 0:11:00When you have the choice between building a tunnel in Miami
0:11:00 > 0:11:03or an arch in Chernobyl,
0:11:03 > 0:11:08it seems strange to go, to choose to go to Chernobyl.
0:11:08 > 0:11:10It's a complicated project,
0:11:10 > 0:11:13because it's difficult to understand each other.
0:11:13 > 0:11:18MAN GIVES INSTRUCTIONS IN OWN LANGUAGE
0:11:18 > 0:11:22It's hard to find somebody who hasn't heard of Chernobyl.
0:11:22 > 0:11:27You know, my kids, when they talk about what their dad does, you know,
0:11:27 > 0:11:30they're like, "Oh, yeah, that's a pretty special project."
0:11:30 > 0:11:33I had a very nice agency call me and they asked
0:11:33 > 0:11:35if I was interested in Chernobyl.
0:11:35 > 0:11:37And I laughed and I said,
0:11:37 > 0:11:38"You're having a joke with me."
0:11:38 > 0:11:41But after a few conversations,
0:11:41 > 0:11:43I realised they were being serious,
0:11:43 > 0:11:45and I thought, "This is a challenge."
0:11:45 > 0:11:50The first stage of the operation is to construct the arch,
0:11:50 > 0:11:52in two halves.
0:11:53 > 0:11:57The frame will be made from 25,000 tonnes of steel tubes,
0:11:57 > 0:12:00whilst the vast roof will be clad with stainless steel.
0:12:05 > 0:12:09Ukraine's harsh climate will make building the arch
0:12:09 > 0:12:12a formidable challenge.
0:12:12 > 0:12:15The biggest problem we have is the weather.
0:12:15 > 0:12:18It's the biggest, biggest problem on here.
0:12:18 > 0:12:20For the winter period, we can lose three months,
0:12:20 > 0:12:22four months of the year.
0:12:36 > 0:12:40Winter temperatures here can plunge to -29 Celsius.
0:12:44 > 0:12:46Today, we have the wind problem,
0:12:46 > 0:12:51yesterday we had ice on the roof, so we could not work.
0:12:51 > 0:12:55We lost a whole morning yesterday just through ice on the roof alone.
0:12:56 > 0:12:59Ian's team must work 109 metres above the ground.
0:13:01 > 0:13:04That's twice the height of Nelson's Column.
0:13:05 > 0:13:06MAN SHOUTS
0:13:06 > 0:13:08For this job, it's extremely dangerous.
0:13:08 > 0:13:10The winds, the rains,
0:13:10 > 0:13:13makes the surfaces that we're working on very slippy.
0:13:14 > 0:13:17The roofers are all trained rope access technicians.
0:13:18 > 0:13:20But in these conditions,
0:13:20 > 0:13:24a momentary lapse of concentration could be fatal.
0:13:28 > 0:13:30Some of the materials that we are using,
0:13:30 > 0:13:33they can act like a kite, if you like.
0:13:33 > 0:13:35You can imagine a sail in the air,
0:13:35 > 0:13:39and the material is razor sharp, so it's very, very dangerous.
0:13:41 > 0:13:43So, yes, we have to be very, very careful.
0:13:49 > 0:13:53The extreme weather and heights aren't the only risks that
0:13:53 > 0:13:54the team must battle.
0:13:59 > 0:14:03Radiation is still streaming from the melted uranium fuel
0:14:03 > 0:14:05in the destroyed reactor.
0:14:07 > 0:14:12The uranium fuel gives off radiation in the form of gamma rays,
0:14:12 > 0:14:13high energy photons.
0:14:16 > 0:14:20Some of these pass through the walls and stream out
0:14:20 > 0:14:21into the surrounding space.
0:14:22 > 0:14:26Most pass straight through a human body.
0:14:26 > 0:14:28But some interact, damaging cells...
0:14:30 > 0:14:34..and fragmenting DNA. Which can cause cancer.
0:14:39 > 0:14:41The dangers are very real.
0:14:43 > 0:14:46Back in 1986, when the Chernobyl reactor exploded,
0:14:46 > 0:14:50the blast blew open the pressure vessel holding the uranium fuel.
0:14:54 > 0:14:56This exposed workers and firefighters to
0:14:56 > 0:14:58high levels of radiation.
0:15:03 > 0:15:06Engineer Nikolai Pazhentsov
0:15:06 > 0:15:09was on duty in the reactor as the disaster unfolded.
0:15:31 > 0:15:34Radiation burns skin,
0:15:34 > 0:15:37and can prevent cells in the body dividing normally.
0:15:51 > 0:15:53In the weeks following the disaster,
0:15:53 > 0:15:5728 workers died from their exposure to radiation.
0:16:07 > 0:16:09Every year, on the anniversary of the disaster,
0:16:09 > 0:16:11the people of Slavutych,
0:16:11 > 0:16:15the town where most Chernobyl workers now live,
0:16:15 > 0:16:17remember those who lost their lives.
0:16:21 > 0:16:25Viktor Ivkin was also working at the reactor that night.
0:16:26 > 0:16:30Like many others, he received a large dose of radiation.
0:16:48 > 0:16:53100 Roentgens is over 900 times the annual dose of radiation
0:16:53 > 0:16:56a member of the public is allowed today.
0:17:22 > 0:17:27Today, at the Chernobyl plant, the danger of radiation still exists.
0:17:32 > 0:17:3795% of the uranium that was in the reactor before the explosion
0:17:37 > 0:17:38is still there.
0:17:44 > 0:17:46Close to the reactor,
0:17:46 > 0:17:49the high number of gamma rays makes it too dangerous to work for
0:17:49 > 0:17:52the long periods of time needed to construct the arch.
0:17:55 > 0:17:58But the engineers have one thing on their side.
0:18:01 > 0:18:05As the gamma rays leave the reactor,
0:18:05 > 0:18:07they get further apart from each other.
0:18:09 > 0:18:11And some are absorbed in the air.
0:18:13 > 0:18:16So for every 1,000 gamma rays passing through
0:18:16 > 0:18:20a person standing 30 metres from the radioactive source...
0:18:23 > 0:18:28..only about one will pass through a worker standing 300 metres away,
0:18:28 > 0:18:31where they're building the arch.
0:18:42 > 0:18:44Radiological engineer Nicolas Guilcher
0:18:44 > 0:18:48measures the radiation across the site.
0:18:48 > 0:18:49You can see...
0:19:07 > 0:19:10A special unit checks the daily amount of radiation every
0:19:10 > 0:19:12worker receives.
0:19:13 > 0:19:16We provide everybody with dosimeters.
0:19:16 > 0:19:18I have a French national dosimeters,
0:19:18 > 0:19:21I have the Ukrainian national dosimeters, and then we
0:19:21 > 0:19:26so have an electronic dosimeter that is our operational dosimeter.
0:19:28 > 0:19:32The dosimeters ensure no worker receives too much radiation.
0:19:36 > 0:19:39There is one further challenge that makes this already complex
0:19:39 > 0:19:40project even tougher.
0:19:42 > 0:19:44Time.
0:19:47 > 0:19:52The crumbling reactor to their side could collapse at any moment.
0:19:55 > 0:20:01In June 1986, two months after the disaster, Soviet engineers
0:20:01 > 0:20:05began building the sarcophagus to enclose the ruined reactor.
0:20:07 > 0:20:12The plan required 300,000 cubic metres of concrete
0:20:12 > 0:20:15to buttress the damaged walls.
0:20:15 > 0:20:18And giant steel beams to support the roof.
0:20:20 > 0:20:23But the extreme radiation made it impossible to build
0:20:23 > 0:20:25the sarcophagus to normal engineering standards.
0:20:38 > 0:20:42Because all sarcophagus had no...building.
0:20:47 > 0:20:50The sarcophagus had no proper foundations.
0:20:50 > 0:20:53It simply rested on the ruins of the destroyed reactor.
0:20:56 > 0:21:00Even as they built it, engineers knew its days were numbered.
0:21:28 > 0:21:30Now, the 30 years are up.
0:21:35 > 0:21:38If the roof of the sarcophagus collapses,
0:21:38 > 0:21:41it will throw radioactive dust out into the atmosphere...
0:21:42 > 0:21:46..where the wind could blow it towards the construction site.
0:21:48 > 0:21:51If a worker inhales a radioactive fragment,
0:21:51 > 0:21:56it could stay in the body, releasing radiation that could cause cancer.
0:22:02 > 0:22:04Good morning, all.
0:22:04 > 0:22:07So, this is jacking and lifting, so I will ask you all to not
0:22:07 > 0:22:10stand under the load if you don't need to be under the load.
0:22:10 > 0:22:12HE SPEAKS RUSSIAN
0:22:15 > 0:22:18The team building the arch is in a race against time to complete
0:22:18 > 0:22:22the job before the sarcophagus collapses.
0:22:22 > 0:22:24As soon as you are ready...
0:22:25 > 0:22:29Deputy construction manager Jean-Philippe Gardeur and the team
0:22:29 > 0:22:33are gearing up to lift the second half of the arch to its full height.
0:22:33 > 0:22:36Everything on this field is huge, it's enormous, you know?
0:22:36 > 0:22:38We don't have small things.
0:22:38 > 0:22:42Everything we touch, everything we do, is completely crazy.
0:22:44 > 0:22:46Nice to hear this noise, eh?
0:22:46 > 0:22:51It will take 40 huge jacks to raise this metal monster.
0:22:51 > 0:22:55That's going to be very tight, that's for sure. But we'll see.
0:22:55 > 0:22:57HE SPEAKS OWN LANGUAGE
0:22:57 > 0:23:00Each jack has enough power to lift five jumbo jets.
0:23:02 > 0:23:05- OK, guys. So, we start the jacking now.- OK.
0:23:17 > 0:23:20- Quickly.- Quickly, quickly.
0:23:20 > 0:23:22Seven...
0:23:27 > 0:23:29OK. Let's continue.
0:23:29 > 0:23:31HE SPEAKS OWN LANGUAGE
0:23:39 > 0:23:42OK, perfect. OK.
0:23:42 > 0:23:44CHEERING
0:23:44 > 0:23:49Success. But the team can't afford to kick back and relax.
0:23:53 > 0:23:57If the sarcophagus collapses before the arch is in place,
0:23:57 > 0:24:01the fallout would contaminate both the arch and work site.
0:24:02 > 0:24:05It would undo the years of work it took to clear up the
0:24:05 > 0:24:08radioactive debris from the original disaster.
0:24:13 > 0:24:15It's a nightmare scenario,
0:24:15 > 0:24:19and the people here know better than anyone what the effects would be.
0:24:30 > 0:24:35Two miles from the reactor lies the abandoned city of Pripyat.
0:24:37 > 0:24:4050,000 people once lived here.
0:24:40 > 0:24:42Many of them workers at the nuclear plant.
0:25:13 > 0:25:16High levels of radioactive debris fell on this city.
0:25:19 > 0:25:22It will be uninhabitable for hundreds of years.
0:25:32 > 0:25:33Autumn 2014.
0:25:40 > 0:25:43Jean-Philippe must now join the two halves of the arch together
0:25:43 > 0:25:45before winter sets in.
0:25:48 > 0:25:49OK.
0:25:52 > 0:25:57It will take 56 pairs of hydraulic pistons and over
0:25:57 > 0:25:59a megawatt of power to pull the arch together.
0:26:29 > 0:26:34The two parts of the arch are finally one. It's a major moment.
0:26:36 > 0:26:37For the first time,
0:26:37 > 0:26:40it's possible to see the vast scale of the new shelter.
0:26:45 > 0:26:48Right now, it may look like nothing more than an empty hanger.
0:26:51 > 0:26:54But before they slide the shelter over the reactor,
0:26:54 > 0:26:59engineers will transform it into a living, breathing machine,
0:26:59 > 0:27:02designed to tackle Chernobyl's long-term problems.
0:27:08 > 0:27:13The radioactive debris inside the reactor will remain dangerous
0:27:13 > 0:27:15for at least 20,000 years.
0:27:18 > 0:27:21If engineers simply covered the reactor with the arch and did
0:27:21 > 0:27:24nothing else, they would only be adding to the problem.
0:27:27 > 0:27:31In time, many years from now, the arch would collapse,
0:27:31 > 0:27:35and a future generation would need to build another, even bigger
0:27:35 > 0:27:37one, to keep the reactor safe.
0:27:42 > 0:27:46To stop this happening, engineers must fit out the arch with
0:27:46 > 0:27:50trailblazing equipment designed to clear up the destroyed reactor.
0:27:52 > 0:27:56Nicolas Caille is in charge of constructing the new shelter.
0:27:56 > 0:28:00We have to provide tools to enable the construction.
0:28:00 > 0:28:03We have to remove the sarcophagus built by the Russians,
0:28:03 > 0:28:04so first of all,
0:28:04 > 0:28:08we need to remove the roof over all the exploded reactor,
0:28:08 > 0:28:13and then, after, they will have two break the concrete and at the
0:28:13 > 0:28:17end, remove the fuel in the heart of the reactor.
0:28:17 > 0:28:19It will take a long time.
0:28:23 > 0:28:29Our arch is guaranteed for 100 years, so at the maximum,
0:28:29 > 0:28:32they can take 100 years.
0:28:34 > 0:28:39No-one has attempted to dismantle an exploded nuclear reactor before.
0:28:41 > 0:28:44Radiation makes the job too dangerous for people.
0:28:47 > 0:28:51The fuel that was there is still there, but when they start to
0:28:51 > 0:28:56dismantle it, you're going to expose that fuel, and as it gets exposed,
0:28:56 > 0:29:00the level of radiation will get much, much higher than it is today.
0:29:04 > 0:29:07Rob Owen leads the team building a special robotic crane
0:29:07 > 0:29:12that will dismantle the reactor... from inside the shelter.
0:29:15 > 0:29:18It uses an ingenious system of wires to carry a platform
0:29:18 > 0:29:20holding a robotic arm.
0:29:24 > 0:29:27The arrangement of the wires is crucial.
0:29:30 > 0:29:34If the platform was supported by vertical wires, it would swing.
0:29:36 > 0:29:41But using three pairs of wires arranged in triangles,
0:29:41 > 0:29:45and adding a heavy weight, makes it rigid.
0:29:47 > 0:29:51It's not perfect, a strong side force could move the platform
0:29:51 > 0:29:52and slacken in some of the wires.
0:29:54 > 0:29:57But if the weight on the platform is heavy enough,
0:29:57 > 0:29:59all the wires will stay tight.
0:29:59 > 0:30:03And the platform will remain rigid enough to hold the robot arm
0:30:03 > 0:30:07that will dismantle the sarcophagus.
0:30:07 > 0:30:10We kind of had to really go back and study the design.
0:30:10 > 0:30:12Would it work here? Could we make it big enough?
0:30:12 > 0:30:14It had to be considerably larger
0:30:14 > 0:30:16than anything that had ever been built.
0:30:18 > 0:30:22But the idea was really intriguing, because of all the pluses.
0:30:25 > 0:30:28To drill into walls or pull a beam,
0:30:28 > 0:30:32the robotic arm needs to be able to push and pull horizontally.
0:30:33 > 0:30:36We have the six wire ropes, and a lot of weight here,
0:30:36 > 0:30:39as you can see on the bottom.
0:30:39 > 0:30:42All the cables remain in tension.
0:30:42 > 0:30:47It provides that stiffness that allows you to do pushing, pulling...
0:30:53 > 0:30:57This quarter scale model demonstrates that the concept works.
0:30:59 > 0:31:02But the only place large enough to test the full-size crane will
0:31:02 > 0:31:04be in the arch itself.
0:31:11 > 0:31:14Summer 2015.
0:31:14 > 0:31:16In less than 16 months,
0:31:16 > 0:31:20the team must slide the arch over the reactor.
0:31:20 > 0:31:23But there's yet another major job they must complete before
0:31:23 > 0:31:24that deadline.
0:31:27 > 0:31:31Right next to the reactor, they must build the nerve centre that
0:31:31 > 0:31:35will house the control systems for the arch.
0:31:35 > 0:31:36And where trucks will collect
0:31:36 > 0:31:39the broken down pieces of the old reactor.
0:31:42 > 0:31:45It will be the entrance into the arch,
0:31:45 > 0:31:50so the truck will enter below the arch and all the waste,
0:31:50 > 0:31:54the deconstructed material, will go through that building,
0:31:54 > 0:31:57out of that building, to be stored somewhere else.
0:32:00 > 0:32:02The real challenges the location.
0:32:02 > 0:32:05It's just ten, 20 metres from the exploded reactors.
0:32:08 > 0:32:13This area is so close to the reactor that builders must wear extra
0:32:13 > 0:32:16protection and working hours are limited.
0:32:21 > 0:32:24It's too dangerous for people to work inside the crane cabs above
0:32:24 > 0:32:25the reactor.
0:32:28 > 0:32:31So operators drive them by remote control
0:32:31 > 0:32:34from the safety of concrete sentry boxes.
0:32:36 > 0:32:42I don't think 30 years ago there was a word in construction for safety.
0:32:42 > 0:32:46It's increased... by tenfold, 100 fold.
0:32:48 > 0:32:51Safety is much more important than it was before.
0:32:52 > 0:32:57Back in 1986, the priority was to clean up the disaster...
0:32:58 > 0:33:00..and people paid a heavy price.
0:33:04 > 0:33:08After Chernobyl exploded, it burned for nine days,
0:33:08 > 0:33:12spewing radioactive dust onto the surrounding countryside.
0:33:14 > 0:33:19The Soviet authorities declared a 30km radius exclusion zone
0:33:19 > 0:33:20around the reactor.
0:33:23 > 0:33:27They drafted in 350,000 people to clean up the radiation.
0:33:30 > 0:33:33They were called liquidators.
0:33:36 > 0:33:40At the centre of the zone, they cleared the radioactive
0:33:40 > 0:33:42debris from the roof of the exploded reactor.
0:33:44 > 0:33:48Here, some only had 45 seconds to perform their task before
0:33:48 > 0:33:51their dose of radiation became too great.
0:33:56 > 0:33:58In the surrounding area,
0:33:58 > 0:34:01they washed down surfaces to remove the radioactive dust.
0:34:06 > 0:34:09They bulldozed and buried the most contaminated homes.
0:34:13 > 0:34:17Along with over one million tonnes of contaminated soil and machinery.
0:34:23 > 0:34:26Among liquidators was Ivan Martynenko.
0:34:37 > 0:34:39GEIGER COUNTER RAPIDLY CLICKS
0:34:58 > 0:35:01OFFICER GIVES COMMANDS IN RUSSIAN
0:35:07 > 0:35:10The World Health Organization estimates that
0:35:10 > 0:35:14around 2,200 liquidators have died or will die
0:35:14 > 0:35:17as a result of the radiation they received.
0:35:25 > 0:35:27Those guys are heroes.
0:35:28 > 0:35:30They did tremendous work.
0:35:30 > 0:35:32It could have spread and been much, much worse.
0:35:36 > 0:35:38Today, the clean-up isn't finished.
0:35:51 > 0:35:55It will take decades for the remote-controlled cranes
0:35:55 > 0:36:00to dismantle the damaged reactor and dispose of its radioactive waste.
0:36:04 > 0:36:08This creates another major design challenge for the engineers
0:36:08 > 0:36:09building the arch.
0:36:11 > 0:36:17It must last 100 years. The metallic structure cannot last 100 years.
0:36:17 > 0:36:21You have to protect the structure and repaint it.
0:36:21 > 0:36:24I mean, as a French, I take the example of the Eiffel Tower,
0:36:24 > 0:36:27which is repainted every 7-10 years.
0:36:29 > 0:36:32Moisture in the air will cause the steel to rust over time.
0:36:34 > 0:36:37Painting the steel protects it.
0:36:37 > 0:36:41But it will be impossible to repaint the steelwork once the arch
0:36:41 > 0:36:43sits over the reactor.
0:36:43 > 0:36:47As you can see, the steel structure has been painted in the factory.
0:36:47 > 0:36:51This paint will last 15 years.
0:36:51 > 0:36:55Unfortunately, we will not be able to renew it once the arch
0:36:55 > 0:36:59will be in the final position, because the radiation
0:36:59 > 0:37:04condition at that location are too severe for a painter.
0:37:11 > 0:37:15But left unpainted, the arch will corrode.
0:37:17 > 0:37:18To solve this problem,
0:37:18 > 0:37:23they're engineering the arch to be an ingenious breathing structure.
0:37:32 > 0:37:37The gap between the arch's exterior roof and interior ceiling
0:37:37 > 0:37:38will be airtight.
0:37:39 > 0:37:45This creates a vast enclosed space around the steelwork.
0:37:45 > 0:37:48Powerful fans will suck in air from outside...
0:37:50 > 0:37:53..channel it through massive dehumidifiers to remove moisture...
0:37:55 > 0:38:00..then blow the dried air along 3.5km of aluminium ducts...
0:38:02 > 0:38:05..into every corner of the enclosed space.
0:38:07 > 0:38:10The ducts will constantly recirculate the dry air...
0:38:12 > 0:38:16..to make sure that the atmosphere in the enclosure remains dry
0:38:16 > 0:38:18so the steelwork doesn't rust.
0:38:21 > 0:38:26For the ventilation to work, the interior ceiling must be airtight.
0:38:32 > 0:38:36We have some junctions here, so because of this gap,
0:38:36 > 0:38:40we have to do a compressed sealant, which makes the air seal tight.
0:38:43 > 0:38:45This cladding is stainless steel,
0:38:45 > 0:38:49and it's designed for the purpose of containing any airborne
0:38:49 > 0:38:55contaminated particles from escaping into the environment during
0:38:55 > 0:38:57the dismantling of the reactor number four.
0:39:01 > 0:39:02Spring 2016.
0:39:05 > 0:39:08Before engineers slide the arch over the reactor...
0:39:10 > 0:39:14..they must install the massive cranes 80 metres above the ground.
0:39:19 > 0:39:26- Baptiste Briois is the engineer in charge.- Up, up, up. High up. Steps.
0:39:26 > 0:39:30Today, he has a 26-storey climb to the control room.
0:39:39 > 0:39:43369. 369 steps.
0:39:43 > 0:39:45Twice a day!
0:39:47 > 0:39:51Everyone in position, everything is ready. We can start.
0:39:51 > 0:39:53We can go. We can start.
0:39:58 > 0:40:01The team is relying on 12 hydraulic jacks fixed near the top of
0:40:01 > 0:40:06the arch to lift the 800-tonne crane into position.
0:40:10 > 0:40:11Inside the jacks,
0:40:11 > 0:40:14hydraulic jaws grip the wires attached to the crane
0:40:14 > 0:40:17and slowly hoist them up.
0:40:25 > 0:40:28It's coming closer and closer. I like it.
0:40:28 > 0:40:31But just of the crane lifts off, they hit a glitch.
0:40:37 > 0:40:38Is there...? Sorry, sorry.
0:40:43 > 0:40:44Is it OK?
0:40:44 > 0:40:48No, apparently have a little problem with the strain carousel.
0:40:48 > 0:40:51The lifting wires are tangling.
0:40:53 > 0:40:55I'll be back in a minute.
0:40:59 > 0:41:02Working 90 metres above the ground,
0:41:02 > 0:41:05it's a precarious operation wrestling the wires back into place.
0:41:17 > 0:41:18It was very quick,
0:41:18 > 0:41:22they are very efficient, so we can still finish today.
0:41:22 > 0:41:23HE SPEAKS OWN LANGUAGE
0:41:52 > 0:41:57Now, engineers can start tests on the full-scale crane.
0:41:57 > 0:42:01- Now, we can lift.- Yes. Yes, we can lift, yes.
0:42:02 > 0:42:04Within the next few years,
0:42:04 > 0:42:08these cranes will start dismantling the ruins of the Chernobyl reactor.
0:42:13 > 0:42:14It will be the final step
0:42:14 > 0:42:17in the long operation to make the site safe.
0:42:19 > 0:42:22But the reactor is only one part of a wider problem.
0:42:26 > 0:42:30During the disaster, large quantities of radioactive
0:42:30 > 0:42:34material fell in the area around Chernobyl.
0:42:34 > 0:42:38A 30km exclusion zone was set up around the reactor.
0:42:41 > 0:42:4430 years on, it's still a restricted area.
0:42:49 > 0:42:53But what does the future hold for this contaminated land?
0:42:57 > 0:43:01Scientists make regular visits into the exclusion zone to study
0:43:01 > 0:43:03the effects of the radioactive contamination.
0:43:07 > 0:43:11Ecologist Mike Wood is investigating what types of animals live in
0:43:11 > 0:43:15the zone, and if the levels of radiation effect where they live.
0:43:20 > 0:43:23At the time of the accident,
0:43:23 > 0:43:26depending on which direction the wind was blowing and whether
0:43:26 > 0:43:29or not there was rainfall, you got different amounts of
0:43:29 > 0:43:33radioactive fallout in different parts of the exclusion zone.
0:43:35 > 0:43:39Mike is setting up camera traps in three different areas,
0:43:39 > 0:43:43places with high, medium and low radioactive contamination.
0:43:50 > 0:43:52The traps will photograph any large mammal
0:43:52 > 0:43:54that moves in front of the lens.
0:43:57 > 0:44:00We're hoping to be able to understand more about the way
0:44:00 > 0:44:04in which the range of large mammal species that we see
0:44:04 > 0:44:08is or is not influenced by the radiation levels.
0:44:11 > 0:44:15By placing traps at 84 randomly chosen sites in each area,
0:44:15 > 0:44:19Mike hopes to discover how many different species of large
0:44:19 > 0:44:20mammals live in each place.
0:44:23 > 0:44:24So when we put the cameras out,
0:44:24 > 0:44:29we take a GPS reading of the location of the camera, and then we
0:44:29 > 0:44:33can use hand-held GPS like this to be able to find the cameras again.
0:44:33 > 0:44:36And then come and see what it's recorded.
0:44:39 > 0:44:41So... Let's have a look at this.
0:44:51 > 0:44:56The cameras reveal an astonishing variety of life.
0:44:56 > 0:44:58So we can see that we've got an elk here.
0:44:59 > 0:45:01And wild boar, as well.
0:45:01 > 0:45:04We see quite a range of animals on most of the cameras
0:45:04 > 0:45:05that we bring back in.
0:45:05 > 0:45:10Red deer, wolves, lynx, Eurasian lynx,
0:45:10 > 0:45:12and also European bison, as well.
0:45:25 > 0:45:27In the high contamination areas,
0:45:27 > 0:45:30and in the low contamination areas, there doesn't seem to be
0:45:30 > 0:45:35a difference in the range of species that we see.
0:45:35 > 0:45:39It appears that some animals are thriving in the exclusion zone.
0:45:41 > 0:45:45But the animals might not have it all to themselves for long.
0:45:54 > 0:45:58In the once abandoned town of Chernobyl, nine miles from the
0:45:58 > 0:46:02reactor, radiation levels are low enough that some workers
0:46:02 > 0:46:07constructing the shelter stay here for up to two weeks at a time.
0:46:08 > 0:46:12And a Chinese company plans to take advantage of the cheap land
0:46:12 > 0:46:17to install 25 square kilometres of solar panels
0:46:17 > 0:46:21to once again generate electricity in the zone.
0:46:35 > 0:46:37November 2016.
0:46:39 > 0:46:43There are only 11 days to go before the team moves the arch.
0:46:44 > 0:46:46We are coming to the end.
0:46:46 > 0:46:50We're preparing for the skidding of the arch over the reactor.
0:46:50 > 0:46:54At last, this huge thing is built
0:46:54 > 0:46:57and it's going to move to where it should be.
0:46:59 > 0:47:01For the engineers,
0:47:01 > 0:47:04this is the last chance to make sure everything works.
0:47:05 > 0:47:08There's a lot more activity,
0:47:08 > 0:47:12because we now have many more tasks to complete.
0:47:12 > 0:47:13All in the same period.
0:47:16 > 0:47:18One job is crucial before they slide the arch.
0:47:20 > 0:47:24They must open its enormous special doors.
0:47:30 > 0:47:34To stop radioactive dust escaping from inside the arch...
0:47:36 > 0:47:39..its end wall must form a perfect seal around the
0:47:39 > 0:47:41old reactor building.
0:47:44 > 0:47:47But parts of the sarcophagus stick out,
0:47:47 > 0:47:50preventing the arch from sliding to its final position.
0:47:53 > 0:47:55So engineers have equipped the arch with
0:47:55 > 0:47:59tilting panels, like giant cat flaps
0:47:59 > 0:48:01that they must raise.
0:48:03 > 0:48:06And then lower into place when the arch is in position.
0:48:09 > 0:48:13Sealing the small remaining gap with a flexible plastic membrane.
0:48:20 > 0:48:25Just as the team gets set to raise the heaviest panel, a winter
0:48:25 > 0:48:29blizzard strikes, threatening to shut down the operation.
0:48:46 > 0:48:49The icy temperatures could freeze the machinery.
0:48:53 > 0:48:59We have six tilting panels and the largest one is 320 tonnes.
0:49:00 > 0:49:04At the location where they will be located, it is not possible
0:49:04 > 0:49:10to send a person to close these tilting panels, to operate them.
0:49:10 > 0:49:13So we have designed a system of hydraulic jacks,
0:49:13 > 0:49:17a system of winches to close these panels remotely.
0:49:25 > 0:49:29It takes four hours to winch the massive cat flap open.
0:49:48 > 0:49:53Seven years after work began to build the 36,000-tonne shelter,
0:49:53 > 0:49:57the day finally arrives when the team will attempt to slide it
0:49:57 > 0:49:59over the reactor.
0:50:02 > 0:50:06It will be the largest structure ever moved across land.
0:50:06 > 0:50:10We are almost at the end, and, yes, we are under pressure.
0:50:10 > 0:50:12It's a great challenge, because of the size.
0:50:15 > 0:50:17I'm also thinking about myself.
0:50:17 > 0:50:19I have already a lot of white hair,
0:50:19 > 0:50:21and the sooner it will be finished, the better it will be for me.
0:50:24 > 0:50:27When you come here, you look at the distance between the reactor and the
0:50:27 > 0:50:31arch, you're thinking, wow, this is going to be a couple of days' work.
0:50:31 > 0:50:35Moving this massive structure will be no simple task.
0:50:38 > 0:50:41The obvious way to move a monster arch would be on wheels.
0:50:44 > 0:50:45But that won't work here.
0:50:47 > 0:50:51The arch is so heavy that it would overload the wheel bearings...
0:50:54 > 0:50:58..which would fracture, leaving the structure stranded.
0:51:04 > 0:51:05So instead of wheels...
0:51:08 > 0:51:14..engineers will use 116 steel feet known as skid shoes.
0:51:16 > 0:51:21These will slide on Teflon pads placed on top of the rails.
0:51:30 > 0:51:34It's a typical example of a Teflon pad with the two holes in it.
0:51:34 > 0:51:39Over these, we put the Teflon pad, right solid.
0:51:39 > 0:51:41And basically, if you put a lot of them,
0:51:41 > 0:51:45you make your own sliding way for the skid shoes to slide on.
0:51:53 > 0:51:58This nonstick surface, also used on frying pans, will help the
0:51:58 > 0:52:03stainless steel feet of the arch to slide with very little friction.
0:52:05 > 0:52:10To push the arch, engineers will fit each leg with hydraulic pistons.
0:52:12 > 0:52:15These move a pair of wedges that grip the steel rail.
0:52:18 > 0:52:23Powerful pumps will then extend the pistons to push the arch forward.
0:52:26 > 0:52:30More than 200 pistons must work in perfect unison
0:52:30 > 0:52:34to slowly slide the arch towards the reactor.
0:52:43 > 0:52:45This is a one-off skidding.
0:52:45 > 0:52:46I mean, you can't go back,
0:52:46 > 0:52:50so you should be sure that you have not forgotten anything.
0:52:50 > 0:52:53HE GIVES INSTRUCTIONS
0:53:01 > 0:53:04This is the critical manoeuvre everyone
0:53:04 > 0:53:07has been working towards for seven years.
0:53:08 > 0:53:11There's the confirmation that we are ready. OK.
0:53:11 > 0:53:14HE GIVES INSTRUCTIONS
0:53:15 > 0:53:17We can go.
0:53:17 > 0:53:19Yeah?
0:53:19 > 0:53:20OK. Allez.
0:53:20 > 0:53:22- On y va. - On y va. OK.
0:53:24 > 0:53:25We go.
0:53:25 > 0:53:31The pistons fire up. 2,000 tonnes of force pushes against the arch.
0:53:33 > 0:53:35OK. Going.
0:53:37 > 0:53:39And they're off.
0:53:39 > 0:53:44The vast structure, as heavy as 3.5 Eiffel Towers,
0:53:44 > 0:53:48slides towards the reactor at around ten metres an hour.
0:53:55 > 0:53:59It's crucial that both sides of the arch move at the same speed.
0:54:01 > 0:54:04If you move one side faster than the other, you will get bending
0:54:04 > 0:54:08in the arch, which can lead to damage of the arch.
0:54:08 > 0:54:10And if we go too far from each other, then you see the
0:54:10 > 0:54:14deviation between the two gets too high, and then we have to adjust.
0:54:14 > 0:54:18In the screen, all the upper skid shoes are the North.
0:54:19 > 0:54:23These are the South, so we can select the upper skid shoes
0:54:23 > 0:54:27and move forward to correct the readings we get on the system.
0:54:27 > 0:54:29For the South, 383.
0:54:31 > 0:54:33- OK. OK, thank you.- What is that?
0:54:34 > 0:54:36Ten? Is the difficult part of it.
0:54:36 > 0:54:41You've got so much data, you have to act correctly and quickly.
0:54:41 > 0:54:42OK, go.
0:55:01 > 0:55:03The closer they get to the reactor,
0:55:03 > 0:55:06the more difficult the operation becomes.
0:55:11 > 0:55:15Sliding the arch over its walls will be tight.
0:55:19 > 0:55:24People will follow the sliding itself of the arch.
0:55:24 > 0:55:2780, 90 people will be involved.
0:55:28 > 0:55:32We have a lot of watchmen, because our clearance is very limited.
0:55:33 > 0:55:38The clearance that we have is quite tight. It's 50 centimetres.
0:55:38 > 0:55:42- What could go wrong during the skidding?- Nothing.
0:55:42 > 0:55:43HE LAUGHS
0:55:43 > 0:55:45Everything should be fine.
0:55:48 > 0:55:53But just as the arch approaches the reactor, they run into trouble.
0:55:58 > 0:56:02It gets caught on a barbed wire fence.
0:56:02 > 0:56:04THEY SHOUT
0:56:10 > 0:56:13THEY SPEAK IN OWN LANGUAGE
0:56:13 > 0:56:17The radiation here is high. So they must act fast.
0:56:19 > 0:56:23There is two rebar we are attaching to the arch.
0:56:23 > 0:56:27So we're sending somebody with a saw to remove these rebar.
0:56:27 > 0:56:28To be sure that we are not damaging the arch.
0:56:34 > 0:56:35With the wire removed...
0:56:37 > 0:56:40..there's one last task before the final push.
0:56:40 > 0:56:41Yes!
0:56:43 > 0:56:48They must lower one of the panels or it could jam on an old chimney.
0:56:50 > 0:56:53If the arch is too close to the end, it will hit the chimney,
0:56:53 > 0:56:56so we have to tilt it before,
0:56:56 > 0:57:00and then we can restart it again and finish it tonight.
0:57:01 > 0:57:04Oh, Vitaly! Yes!
0:57:04 > 0:57:05Go, go.
0:57:13 > 0:57:15The panel clears the chimney...
0:57:20 > 0:57:22..and the final push begins.
0:57:40 > 0:57:42THEY CHEER
0:57:46 > 0:57:49After 33 hours of pushing,
0:57:49 > 0:57:53the arch is finally in position over the reactor.
0:57:53 > 0:57:58It's a feeling of pride. We've achieved something great. It's a big
0:57:58 > 0:58:03step for safety. And Ukraine and Europe will be much safer now.
0:58:03 > 0:58:06CHEERING
0:58:07 > 0:58:12It has taken 18 years of planning, seven years of construction,
0:58:12 > 0:58:16and a unique international collaboration.
0:58:16 > 0:58:20But 30 years after the world's worst nuclear accident,
0:58:20 > 0:58:26Chernobyl is finally a much safer place for generations to come.