The ultimate security blanket

“YOU can take photos. But stay on the road. Don’t step onto the grass.” It is 28 years since the world’s worst nuclear accident, at the Chernobyl nuclear power plant in northern Ukraine, but visitors are still told to be careful. Though much of the plant (at which, even now, 3,000 people work) has been decontaminated, and the roads cleaned up, the surrounding forest has hotspots where fragments of debris and nuclear fuel, ejected by the explosion that destroyed reactor number four on April 26th 1986, emit dangerous radiation.

At the moment, the reactor’s remains are sealed in by a concrete and steel structure known officially as the Shelter Object and colloquially as the sarcophagus. This has done its job for nearly three decades, but there are doubts it can manage a fourth. Wind, rain, rust and time have taken their toll, and the radiation level within it makes maintenance near-impossible. Many fear it may collapse.

That is why visitors to Chernobyl these days will see a huge and growing building looming in front of reactor four’s remains. This is the New Safe Confinement (NSC; it has yet to attract a nickname). It is in essence, as the picture shows, a giant double-skinned stainless-steel Nissen hut, which will have flat walls at each end. It weighs 30,000 tonnes; is taller, at 110 metres, than the Statue of Liberty; and is 165 metres long and 260 metres broad. It is being built by Novarka, a French consortium, and its cost, €1.5 billion, is met by donations from dozens of countries, administered by the European Bank for Reconstruction and Development. It was scheduled for completion in 2005, but political foot-dragging and wrangling over who would pay have delayed its construction by more than a decade. When it is finished, though—probably in 2017—it will protect the sarcophagus from the ravages of the weather and ensure that, even if that older container does fall down, no radiation will escape. With luck, it will be able to do this for a century.

Baba Yaga’s hut

Even now, so long after the explosion, too much radioactivity streams through the sarcophagus from the reactor’s ruined core to allow the NSC to be built in situ. Instead, it is being constructed a few hundred metres away and will be slid into place on rails—making it, Novarka reckons, the biggest movable structure ever built.

That distance, however, is still not enough for complete safety. The construction site is a compromise, for it is on a slope. The railway must be flat, so every metre it is extended means removing and disposing of more tonnes of radioactive soil. Rather than do that, Novarka has built a special concrete radiation shield in front of the sarcophagus, to provide additional protection for its workers. This, though, is a compromise too, for the shield is necessarily far shorter than the NSC’s arch will be at full height. To overcome that, the NSC is composed of two sections—each, in turn, made of linked panels, so that they can remain flat, under the shield’s protection, until raised by special jacks.

To complicate matter further, reactor four shares a building with reactor three, which did not blow up and is not covered by the sarcophagus. The NSC will cover only the reactor-four part of this building. The wall at that end of it thus has a hole through which the building fits, and which will have to be sealed to the building by a membrane when everything is in place.

Even when that has happened, however, only half of the contract will have been fulfilled. The other half—keeping the thing standing for the century specified in its blueprints—will be a challenge. Many large steel structures, such as the Forth Bridge, in Britain, have survived for more than a century. But, as Nicolas Caille, the project’s director at Novarka, points out, these rely on regular repainting to protect them from the elements.

The ruined reactor’s radioactivity means it will be impossible to do that for the NSC. Instead, the plan (besides using stainless rather than normal steel for part of its construction) is to pump warm, dry air between its inner and outer skins. As long as this ventilation system can keep the air’s relative humidity below 40%, the non-stainless bolts and beams that hold the structure together should not rust. For the plan to work, though, the dehumidifiers will have to be kept supplied with power for the whole period.

Then there is the question of what to do with the radioactive junk inside. The ultimate goal is to disassemble the sarcophagus and then cut up and dispose of the remains of the reactor. The NSC is therefore being built with several internal, remotely operable cranes, and the plan is, one day, to use these and robots to do the job.

But that will not be easy. The inside of reactor four is a mess of twisted metal, naked nuclear fuel and lumps of “corium”, a lava-like substance formed when reactor fuel melted and mixed with the concrete floor of the reactor building. This building is so radioactive that anyone walking around in it would accumulate a lethal dose in minutes. Even robots working there will need to be hardened against the radiation, and also dexterous enough to navigate through what is, essentially, a bomb site. Those involved concede that the technology needed to do this does not yet exist. But once the NSC is in place, there will be plenty of time to invent it.

There may, though, be little incentive to do so. Once the NSC is finished, and there is no longer a risk of radiation escaping, the problem of deconstructing the sagging sarcophagus and clearing out the reactor building will become less urgent. There are many other calls on the Ukrainian government’s money, and foreign donors may decide they have higher priorities. Doing nothing might even be sensible—the 100 years the NSC is designed to last will give time for radiation levels inside the reactor building to fall, making any eventual clean-up simpler. When asked about this, Igor Gromotkin, the director of the Chernobyl nuclear power plant, simply smiled and replied: “It’s a good point.”