Olga Betko recalls the Chernobyl explosion and its aftermath...

It would not be an exaggeration to say that everybody in Ukraine, except those born after the event, remembers exactly where they were on 26 April 1986 when Chernobyl's reactor No. 4 exploded.

Luckily for me, a freelance youth magazine reporter living in Kiev, some 60 miles from the plant, I stayed indoors for a few days, working on an important article.

Otherwise, like many others, I might have gone out to enjoy the warm spring days, oblivious to the clouds of radioactive gas and dust spreading in the air around us.

The wind dispersed the invisible poison not only throughout Ukraine, Belarus and Russia, but also across the whole of Europe and the eastern shores of the USA.

After checking the soaring radiation levels, Swedish nuclear engineer Cliff Robinson thought that a nuclear bomb had gone off. It was he who alerted the world. The Kremlin did not acknowledge that anything had happened for several days.

In Ukraine and elsewhere in the Soviet Union, listeners to the so-called "hostile voices" of the BBC and Radio Liberty were alerted to the news.

Rumours reached our family, but we refused to believe them. My father was particularly dismissive: he was not used to the kind of danger that one could not see, smell or touch.

The day after the explosion, in Pripyat, a dormitory town for the power plant's workers, toddlers were still playing out in the playgrounds; their mothers had no idea that a radioactive cloud was engulfing them.

The firemen treated the situation as a routine fire... grabbing chunks of radioactive graphite with their bare hands

The "temporary" evacuation of the town of Pripyat was announced the next day. It is strange, now, to listen to that 26-year-old recording, with the newsreader explaining that "the Communist Party officials and the authorities" were in full control of the situation.

The 50,000 citizens of Pripyat believed that they were leaving their homes for about three days. They would never return.

No one knew what lay ahead and no one had been prepared for what had already happened.

Sergij Akulinin, a turbine operator who was on shift in a neighbouring block at the time of the explosion, and who took part in rescue operations, recalls that there were no instructions on what to do in case of an accident. Emergency workers had no protective gear, and were supplied with dodgy dosimeters.

The firemen treated the situation as a routine fire; Akulinin remembers them grabbing chunks of radioactive graphite with their bare hands. Those men are not around to share their memories; Akulinin thanks his lucky stars that he is still alive.

There were still no official radio or television announcements by May Day, when crowds of people took part in festive demonstrations in Kiev, still unaware of what had happened.

But the rumours persisted, and panic started to spread. Anatoly Romanenko, then the Ukrainian Minister of Health, returned from a trip abroad on 2 May. He recalled in an interview how he was greeted at Boryspil airport, Kiev, by crowds of people desperate to get away. It was not easy for him to persuade Communist Party officials to inform the population about how to protect themselves. When he appeared on television on 5 May, he was allowed to recommend that parents take their children away for "recreational rest", but was banned from using the word "evacuation".

By that point it was probably not possible to contain the truth anyway. Perhaps for the first time in its history, the Soviet propaganda machine faced an event that could not be hidden.

Twenty years after the accident, which, according to the International Atomic Energy Agency, released as much as 400 times the radioactive contamination of the Hiroshima bomb, many questions remain. The jury is still out as to the causes of the accident. The long-term effects on people's health and the environment are also controversial. Even the number of deaths caused by the accident is not known with any degree of accuracy. The economic cost of the Chernobyl disaster is also difficult to estimate, but it runs into tens of billions of dollars.

Perhaps the heaviest price was social and psychological. Akulinin's wife left her home in Pripyat in 1986. "She does not have a single childhood photograph or a toy," he said. "Can you imagine how that feels? Can anyone imagine, what it was like for people suddenly to start their lives from scratch?"

Today, Pripyat is a "ghost town", with an empty ferris wheel in the centre, which was never used - the launch was planned for May Day 1986. Some return each April to lay flowers next to their former homes.

A new town - Slavutich - has been built for the emergency workers. Some older people live inside the 30 km exclusion zone - they just could not bear to leave all they possessed and their whole life behind. One couple, "Father Savva" and his wife Olena, live inside the 10 km zone, the "zone of absolute exclusion". They grow vegetables, and go fishing and mushroom-picking, foraging for whatever they can find.

Recently the Chernobyl area has received more and more visitors - journalists, scientists and tourists. Those who expect to find a dead zone are amazed by the wildlife. When people fled, animals, including some endangered species, turned it into a unique refuge. The Red Forest, one of the most polluted areas in the world, is an astonishingly fertile wildlife habitat. There have been reports of birds flying in and out of holes in the sarcophagus.

Will the contamination have any long-term adverse effect on the flora and fauna of the region? This remains to be seen. Twenty years after the disaster, Chernobyl still holds many secrets.