In Chernobyl the engineers now have plans to build a gigantic hangar to prevent a second disaster. The Ark…an arch-shaped tubular structure…is 360 feet high and 900 feet across. An estimated 200 tons of radioactive matter lies within the temporary structure and everything inside is contaminated. The European Union has spent tens of millions of pounds trying to stabilise the structure but many still fear a collapse and another catastrophe.

The £600 million Ark Project will contain the radioactive remains for the next 100 years while remote-controlled devices or specially trained teams try to dismantle the reactors and store the lethal material. David Sycamore, a Brit working for the EU in Kiev commented: ‘The new shelter is going to be the eighth wonder of the world – it’s an amazing piece of engineering which is on the scale of the Egyptians building the pyramids.’

The engineers may be coming to grips with the scale of the catastrophe but they represent a world of sanity in the smoke and mirrors world of Chernobyl as officials seek to play down the casualty figures. Here is Nikolai Omelyanets, deputy head of the National Commission for Radiation Protection in Ukraine.

‘At least 500 000 people have already died out of the two million people officially classed as victims of Chernobyl. 34 499 people who took part in the clean up of Chernobyl have died in the years since the catastrophe. The death of these people from cancers was nearly three times as high as in the rest of the population. We have found that infant mortality increased 20% to 30% because of chronic exposure to radiation after the accident.’

The UN’s International Atomic Energy Agency and the World Health Organisation are ignoring this information according to Omelyanets. Yesterday The Independent quoted figures from The Chernobyl Forum…a group of a hundred scientists drawn together by the UN. They estimate the final death toll at four thousand from the fall-out with an additional five thousand radiation-related deaths in the heavily contaminated regions. The response of the Nuclear Industry is to insist that Chernobyl couldn’t happen in Western Europe because the Chernobyl Reactors had no strengthened containment shell, which are standard in the design of our nuclear reactors. So how safe are our sites?

Sellafield is one of the biggest nuclear sites in Europe, employing more than 10 000 people and is far more complex than sites like Chernobyl that tend to house only power plants. The Sellafield site is home to Calder Hall, the first British civil nuclear station and an array of other operations including Thorp, the spent nuclear fuel reprocessing plant, and SMP, which was built to produce Mixed Oxide Fuel for overseas customers using plutonium and uranium.

Formerly known as Windscale, it is the site where plutonium was produced for nuclear weapons. The Nuclear Decommissioning Authority believes that the Sellafield clean up will take at least 75 years. Legacy issues there include the continuing clean-up resulting from the 1957 shutdown as a result of a fire, and dealing with a number of ‘ponds’ where waste was dumped fairly indiscriminately.

The scale of the problems at the 770-acre site near Whitehaven is spelled out in the decommissioning authority’s draft strategy. ‘At Sellafield it has been estimated that there may be as much as 20 million cubic metres of contaminated land, some of which is deep underground, resulting largely from leakages from legacy sites,’ it says. At the B30 storage pond the European Commission has complained that it has not been possible to carry out checks to ensure that fissile materials intended for the civil nuclear programme have not been diverted to the military.

The Blair government denies this but the decommissioning authority admits: 'Delays in spent fuel retrieval have resulted in serious degradation of the fuel.’ Dave Skilbeck who is in charge of the B41 solid waste storage ‘silo’ at Sellafield, admits that there is only a partial inventory of what was thrown into the facility he is decommissioning. According to managers at the site, some of the problems stem from when the plant was asked to work flat out during the Miners’ Strike of 1984 - 5 to keep the lights on. Waste problems were rather pushed to one side with no thought of how you dealt with this later.

Meanwhile across the frozen North Slopes of Alaska the region’s largest oil accident on record has been sending hundreds of thousands of gallons of crude oil pouring into the Arctic Ocean after a badly corroded BP Pipeline ruptured. As oil is increasingly transported through environmentally sensitive areas by pipeline the dangers posed by poorly maintained rotting pipes has become increasingly clear. To quote a BP oilman: ‘Something happened to the corrosion rates in that line between September 2005 and the time of the spill that we don’t yet fully understand.’ At the last count clean-up crews had removed 40 000 gallons of crude oil and melted snow off the frozen tundra but indications are that this is the second largest crude oil spill in Alaska…second only to the 1989 Exxon Valdez disaster.

The publicity caused by the leak in the 30-year-old pipeline is set to seriously damage BP’s image, which has been carefully crafted to show it as a company concerned about the environment. BP boasts that it is fully signed up to the dangers of Global Warming and makes a conspicuous effort to flaunt its green credentials. BP has even been erecting wind turbines above its petrol stations. Now they are all doing it…with Tescos the latest to announce Rooftop Turbines.

It was twenty years ago today that the worst nuclear accident in history took place when one of the four reactors at the Chernobyl complex 80 miles north of Kiev in Ukraine exploded. Here is the official version of events. Prior to a routine shutdown, the reactor crew prepared for a test to determine how long turbines would supply power following a loss of power, by deliberately disabling a safety mechanism that shut down the reactor automatically.

When the crew tried to shut down the reactor manually there was a dramatic power surge which caused the fuel elements to rupture. A steam explosion lifted off the cover plate of the reactor releasing radioactive material into the atmosphere. A second explosion blew out fragments of burning fuel and graphite from the reactor’s core, air rushed in and the reactor’s hot graphite core burst into flames. Fire fighters took nine days to put it out. Huge amounts of radioactive material were released…hundreds of times the fallout from the Hiroshima nuclear bomb.

Belarus took the brunt of the uranium dioxide in the plant that escaped. Ukraine was also contaminated. In total five million people were exposed to radiation including the 600 000 workers who volunteered for the clean-up operations.

The disaster occurred in the early hours of 26th April 1986. My two children were living with their mother in Uppsala 800 miles north of Chernobyl and first heard of the disaster a couple of days later when a nuclear power station in Sweden raised the alarm as a radioactive plume passed overhead and drifted north putting Sweden at the mercy of the weather. Had it rained at the wrong time my children would have been covered with radioactive fall-out.

After the disaster the city of Pripyat was emptied of inhabitants. Today it has a chilling, post-apocalyptic look to it. Ragged curtains blow through the broken windows of apartments in deserted and crumbling high-rise blocks. The streets with their Lenin statues and fading posters exhorting a march towards a communist paradise are being reclaimed by vegetation. The four dozen villages in the exclusion zone around Chernobyl were also evacuated but scores of mainly elderly people who could not adapt to the cramped city apartments they were offered have returned surreptitiously. Eventually the authorities were forced tacitly to accept their presence.

The zone’s inhabitants can collect their pensions and once every two weeks a policeman calls by to check that everyone is still alive. Adam Lahovsky, an 82-year old war veteran who lives in a small single-storey timber cottage said: ‘I was not going to allow the Chernobyl disaster to drive me out.’ His wife Nina said that a van selling bread and other staples visited once a week and they spend their pension on food and medicine.

They keep chickens and supplement their diet with berries and wild mushrooms…which have five times the permitted limit for caesium-137. Their son visits regularly to help out. Herds of boars are among the wildlife now thriving in the exclusion zone despite the radiation. Free of human predators the area provides sanctuary for moose, rare Przewalski horses and even wolves.

Evgenia Stepanova of the Ukrainian Scientific Centre for Radiation Medicine said ‘We’re overwhelmed by thyroid cancers, leukaemias and genetic mutations that are not recorded in the World Health Organisation data and which were practically unknown 20 years ago.’

In the Rivne region of Ukraine, 300 miles west of Chernobyl doctors say they are coming across an unusual rate of cancers and mutations. ‘In the 30 hospitals of our region we find that up to 30% of people who were in highly radiated areas have physical disorders including heart and blood diseases, cancers and respiratory diseases. Nearly one in three of all newborn babies have deformities, mostly internal,’ said Alexander Vewremchuk of the Special Hospital for the Radiological Protection of the Population in Vilne.

Twenty years on restrictions are still in place on reindeer in Lapland and on 274 farms in Wales and Cumbria while caesium-137 levels are ten times above permitted levels in Germany, Austria, Italy, Poland and Lithuania.