The 20th anniversary of the Three Mile Island accident, the worst commercial nuclear mishap in us history, was marked by a candle protest and anti-nuclear speeches.

More than 100 protesters spoke out against atomic power and recalled the horror, that had gripped the nation for days and led to the evacuation of about 140,000 people from the Harrisburg area in Middletown, usa .

On March 28, 1979, a relief valve at Three Mile Island's Unit 2 reactor released radioactive water as steam. Plant operators then mistakenly shut off the flow of the cooling water to the 150-tonne radioactive core, prompting a partial meltdown and a large-scale evacuation.

The accident saw a us $1 billion clean-up and a tremendous tightening in safety procedures and regulatory scrutiny. Despite anecdotal reports of cancer and other health problems, official studies have shown no evidence of accident-related health effects, apart from mental stress. "We did not become a ghost town, as some said we would,' said Barbara Layne, mayor of Middletown Borough.

After the Three Mile Island accident, not a single new nuclear plant has been ordered in the nation. The cost of strict and rigourous safety procedures that have been put in place after the accident have made nuclear energy prohibitive.