Just as global warming and rising oil prices were making nuclear energy seem more acceptable, the radioactive leak at the plant near the coastal city of Tarragona sparked new safety concerns.
Socialist Prime Minister Jose Luis Rodriguez Zapatero's anti-nuclear government had appeared to be swimming against the tide in the West, where countries such as Britain, Finland and the United States are increasingly relying on nuclear power.
But the Spanish government seemed to be growing less critical of nuclear energy, when it came out that Asco I had downplayed the importance of a leak that occurred during refuelling in November.
Not only was the leak over 100 times more serious than the 1,000 megawatt plant had reported, but radioactive particles have now been found as far as 60 kilometres outside the plant.
Ultimately the leak was not deemed dangerous in itself. Rated a level 2 on a risk scale of zero to 7, the leak is not believed to have had adverse health effects on any of the 1,600 people being tested. And there has never been a safety problem ranked above level 3 in a Spanish nuclear plant.
But the fact that Asco I appeared to misinform the public about the incident led to the director and the protection chief of the plant being sacked and the plant facing a fine of up to 30 million euros (46 million dollars).
The Asco I incident in addition did arouse safety concerns, with Carlos Bravo from the environmental group Greenpeace describing Spanish nuclear plants as 'obsolete.'
According to trade union sources quoted by the daily El Pais, companies running nuclear plants have in general been cutting personnel and investment costs, thus increasing safety risks.
Zapatero has pledged to close nuclear plants that have been operating for more than 40 years.
In theory, the government wants to close all of Spain's eight active nuclear plants by 2028, while continuing to turn the country into one of the world leaders in the use of renewable energies.
Spain currently gets about a fifth of its energy from nuclear power, as opposed to 10 per cent from wind energy.