I vividly remember hearing the news of a nuclear reactor explosion in Russia twenty years ago and watching with horror those desperate scenes on television of emergency workers flying over the burning reactor to drop sand and concrete in an attempt to put out the fire.

But nothing brings it home like my experience of visiting Chernobyl last weekend and seeing at first hand the ongoing damage caused to people and the environment.

On the 20th anniversary of the world's worst civil nuclear disaster there are still over 350 farms in Wales under restrictions because of radioactive contamination carried on the wind from Chernobyl. There are much higher rates of cancers in the worse affected areas of northern Ukraine and southern Belarus. And for many years to come there will be a 35 mile diameter highly contaminated "exclusion zone" around Chernobyl.

With prior permission and after going through two checkpoints we were allowed to enter this "zone".

I was amazed at the size of this area where it won't be safe for anyone to live for hundreds of years. This 962 square mile area includes forests, villages and large towns as well as the site of the reactor itself. Driving around the zone we hardly saw another person or vehicle. In the forest I saw the remains of houses with trees growing through the roof and pieces of garden furniture still out after being hurriedly abandoned twenty years ago.

It is an eerie experience to walk around a ghost town with no traffic or people. Pripyat is one such place. It was a modern town built to house the Chernobyl plant workers and their families and was one of the first places to be evacuated after the extent of the accident became public knowledge. The only people there now are the scientists and government officials who monitor the contamination and travel there from outside the zone.

Although it is illegal to live within this area some people have returned, preferring to gamble with their health rather than live away from their homes indefinitely. I met one of these people, a farmer in his seventies. His village had been evacuated several days after the disaster and taken to the capital city, Kiev. He had been given a house in another area but the land was so poor he returned to his original home with his family. Around five hundred people have returned of the 130,000 people evacuated to the Ukraine.

Standing in front of Unit 4 of the power station I was lost for words. The geiger counter carried at all times by our Ukranian government guide beeped quickly and showed a radiation reading several hundred times above normal. The remains of the reactor had been hastily covered in a concrete shell, which is by now leaking. We were only allowed to stay there for a maximum of twenty minutes. The radioactivity released in the blast was equivalent to two hundred Hiroshima and Nagasaki bombs.

And dumped in a field near the plant itself are the rusting remains of the helicopters, fire engines and other machinery used in the days following the disaster. We only stayed a few minutes and were warned not to get too close because of the radioactivity. Two hundred and thirty seven emergency workers developed acute radiation sickness and 47 died. It is a chilling reminder of the human sacrifice of the emergency services and the human cost of this disaster.

There are still a lot of unanswered questions about the Chernobyl disaster and it's consequences but there is one lesson we can learn from it. Nuclear power is not safe and the nuclear experiment has failed. After my visit I'm more determined than ever to keep campaigning for a nuclear free Wales.

Jill Evans ASE/MEP