Chernobyl's last wedding: The couple who married as a nuclear disaster unfolded

It was just after midnight. Iryna Stetsenko had finished doing her nails for her wedding, opened the balcony door and was battling her nerves to get to sleep.

In a nearby apartment packed with guests, her fiancé Serhiy Lobanov was asleep on a mattress in the kitchen.

Then a "rumble" disturbed the quiet, says Iryna. "It was as if a lot of planes were flying overhead, everything was humming and the glass in the windows shook."

Serhiy says he "felt a shake, as if some kind of wave passed", wondered if it was a mild earthquake, and fell back to sleep.

The 19-year-old trainee teacher and power plant engineer, who was 25, were looking forward to married life in the newly built Soviet city of Pripyat. They had no idea that the world's worst ever nuclear accident was unfolding less than 2.5 miles (4km) away.

Reactor number four at the Chernobyl power plant – in what is now northern Ukraine - had exploded, spewing out radioactive material that would spread across swathes of Europe.

Forty years later, the highly radioactive remains of the plant are in a warzone. The couple now live in Berlin, having uprooted their lives a second time - this time to escape conflict, not a nuclear disaster.

But on the morning of 26 April 1986, Serhiy remembers waking around 6am, full of excitement, to find his wedding day had dawned gloriously sunny.

He had errands to do - bed linen to take to a friend's apartment where he and Iryna planned to sleep that night, and flowers to buy.

He says he saw soldiers in gas masks outside, and men washing the street with a foamy solution. Some men he knew from his work at the nuclear plant told him they had been called in urgently because "something happened", but they did not know what.

As he looked out from the friend's high-rise apartment, he spotted smoke rising from reactor four.

It would later become clear that firefighters and power plant workers had spent the night risking lethal doses of radiation to tackle a huge toxic blaze.

"I felt a bit anxious," he says. Drawing on his training, he took some fabric, wet it and put it across the apartment entrance as a precaution to catch radioactive dust, he adds.

He then rushed to the market. Unusually for a Saturday morning, it was deserted, so he picked five tulips for the bouquet.

Iryna, who was staying with her mother in the family's apartment, says the phone kept ringing overnight. Her mother sounded "alarmed", she says, by neighbours calling to say "something terrible" had happened. But there was little detail.

Information was strictly controlled in the Soviet Union. They turned on the radio, but there was no mention of any incident.

In the morning, her mother rang the authorities: "They told her not to panic, all planned events in the city should go ahead."

Officially, everything carried on as usual. Children were sent to school.

Later in the day, the bride, groom and guests drove in a line of cars to the Palace of Culture, known for hosting both ceremonial events and popular discos.

They made their vows standing on a cloth embroidered with their names, then moved with their guests to a nearby café.

But the wedding banquet felt "sad", not celebratory, says Serhiy. "Everyone understood that something had happened, but no one knew the details".

For their first dance, they had practised a traditional waltz. But with the growing realisation that a tragedy was unfolding, "from the first steps we went out of rhythm", recalls Iryna. "We just hugged each other and moved in the hug."

Then - exhausted but finally man and wife - they returned to the friend's apartment.

But, Serhiy says, in the early hours of Sunday morning, another friend knocked on the door, telling them to rush to an evacuation train, due to leave at 5am.

The only extra clothing Iryna had with her was a flimsy dress for the second day of the celebrations, so she put her wedding dress back on to hurry back to her mother's apartment to change. Also, her shoes had given her blisters. "I was in a wedding dress and I was running barefoot through the puddles," says Iryna.

It was still dark as they saw the glow of the collapsed reactor from the train. It was "as if you were looking into the eye of a volcano," says Serhiy.

The official announcement, when it came, described the evacuation as "temporary".

"We left for three days, but ended up going for our entire lives," he adds.

The Soviet Union was heavily criticised for its slowness in revealing the scale of the disaster. It was only two days after the explosion – after radiation was detected in Sweden – that it acknowledged an accident had happened. It was more than two weeks before Soviet leader Mikhail Gorbachev spoke about it publicly.

A safety test had gone badly wrong. An estimate cited by the International Atomic Energy Agency (IAEA) and World Health Organization suggests the explosions released 400 times more radioactive material than the bomb at Hiroshima.

Nikolai Solovyov was working as a lead engineer in the turbine hall at the time.

"It was like an earthquake beneath us," he recalls. "We saw the roof collapsing… A blast of air came towards us and brought all this black dust… And the siren started."

He says he and colleagues raced towards the site thinking a generator had exploded – unable to imagine it could be the reactor itself.

One checked their monitors and said radiation levels were "off the charts", Nikolai remembers.

He says they found another colleague standing on one of the turbines, apparently unhurt but vomiting - a sign of radiation sickness. "He was one of the first to die," he says.

The official death toll from the incident is 31 people - two were killed by the explosion itself, while 28 died from Acute Radiation Sickness, and one from cardiac arrest, in the weeks afterwards.

The wider impact of the disaster is contested and difficult to determine. No comprehensive long-term medical study was set up at the time.

In 2005, a study by several UN agencies concluded 4,000 people could die as a result of the accident. Other estimates suggest the number could be tens of thousands.

An operation was launched to stop the exposed reactor pouring out radiation.

Helicopter flights dropped sand and other materials on it. The authorities brought in hundreds of thousands of people from all over the Soviet Union to contain the disaster.

Extreme radiation levels caused machines to break down, so some work had to be done by hand.

Jaan Krinal and Rein Klaar were deployed from Estonia, then part of the Soviet Union, and were part of a group sent to clear debris from the roof of reactor three.

"You wore lead plates - one in front, one on your back, and one between your legs. It was heavy, 20kg or more," says Jaan.

"On your head: a standard Soviet construction helmet - goggles, gloves and a dosimeter [to measure radiation] in your pocket," he says.