While the current political tensions in Ukraine continue to threaten stability in the region, an even larger spectre looms in Chernobyl, the site of the world’s worst nuclear accident. 

Nearly three decades later, recovery from the disaster continues, with construction currently under way on an immense shield designed to entomb the radioactive remains of the reactor that exploded all those years ago.

At nearly 110 metres high and 275 metres wide, and weighing around 32,000 tonnes, the arch-like New Safe Confinement is one of the most complicated feats of modern engineering that, once complete, will be the largest movable structure ever built. It’s designed to last 100 years - the estimated time to finish clean-up at the site. 

But the project is already years behind schedule. Though plans have been in the works to contain the leaky, crumbling reactor since 1992, construction on the New Safe Confinement only began in 2010. Originally slated to be finished 2015, developers have now pushed the date back to 2017. 

Half of the arch has been assembled so far, but the future of the $2.2 billion project, funded by the European Bank for Reconstruction and Development, now hangs in the balance. With Ukraine thrown into an economic crisis and Russia at its borders, there are concerns the shelter may not be completed in time - if at all. 

"It is unfortunately a situation which can further deteriorate and it’s very difficult, then, to predict what the impacts on our project will be," said Vince Novak, director of nuclear safety at the EBRD. 

"You must not forget that this is a project about nuclear safety," Novak said in an interview with The Verge. "And its importance transcends borders and transcends political divisions and differences." 

Adi Roche, head of the NGO Chernobyl Children International, recently returned from a trip to study the progress of the shelter’s construction and describes the situation as a “ticking time bomb”. 

“Chernobyl is the old Soviet Union’s deadly legacy to Ukraine and the world has very real reason to be extremely concerned about the ongoing threat it poses, especially at a time of great instability and growing hostility between Ukraine and Russia," she said. 

For many Ukrainians, Chernobyl remains a deep wound, a stark reminder of an era during which government policies of secrecy and corruption bred deep mistrust among the public. 

A botched system test in reactor four at the Chernobyl Nuclear Power Plant resulted in a catastrophic explosion on April 26, 1986, shooting a plume of nuclear fallout into the sky. Much of Europe was shrouded in radioactive contamination. Inside the reactor, a fire burned for 10 days as firefighters fought to contain the blaze. Many of them would die as a result of radioactive exposure only weeks later. 

Helicopters dumped sand, concrete and boric acid in a desperate attempt to bury the reactor before it was hastily sealed in a concrete and steel shelter known as the sarcophagus. There, a 200-tonne mass of nuclear fuel and other highly unstable radioactive materials remain to this day. But the structure was never meant to be permanent, and after decades, cracks have begun to show. 

Former Soviet leader Mikhail Gorbachev admitted in a 2006 opinion piece that the disaster was a catalyst for the dismantling of the USSR. 

“The nuclear meltdown at Chernobyl . . . was perhaps the real cause of the collapse of the Soviet Union five years later. Indeed, the Chernobyl catastrophe was an historic turning point: there was an era before the disaster, and there is the very different era that followed,” he wrote. 

The crisis was an embarrassing failure for the Soviets, who withheld information about the explosion for nearly three days. It was only after a Swedish power plant raised an alarm over the unusual radiation levels that officials admitted an accident had taken place.

With no warnings of the true dangers of radiation, and no basic safety guidelines in place, firefighters had rushed to the scene at Chernobyl completely unaware they were being exposed to lethal doses of radioactive waste. Many of the first responders, as well as workers sent in to help contain the disaster, suffered severe symptoms of acute radiation poisoning within days. 

When calculating the human cost of the Chernobyl disaster, figures vary widely. Two workers were killed in the initial explosion, with a further few dozen more deaths linked to the incident. Many claim thousands more died as a result of the aftermath and clean-up operations. 

The wider impact of radiation exposure is difficult to measure, however. Over the years, various reports have pointed to rises in fatal cancers among the population as well as the number of children born with genetic defects linked to radiation. Some estimates put the number of people affected as high as a million across Europe, while more conservative figures hover in the tens of thousands. 

The accident at Chernobyl also devastated the natural environment, with the surrounding forest still bearing the effects of the nuclear fallout. Local pine trees absorbed such high levels of radiation in the blast that they turned a reddish shade of brown.

A recent study in the Red Forest, as it’s now known, found the trees had not been decomposing properly. Without natural decomposers like bacteria and fungi to help put nutrients back into the soil, scientists fear a bushfire, fuelled by 28 years’ worth of dead, dry leaves, could redistribute toxic contaminants via smoke over a vast area. 

Meanwhile, what remains of reactor four is still at risk. Encased in its shoddy, rusting sarcophagus, Chernobyl’s time bomb is just one spontaneous chain reaction away from another disaster.