Spain's oldest nuclear plant, known as the 'sister' to Japan's disaster-struck Fukushima plant, is to be closed in July 2013 after 42 years in service, the operator said Thursday.

Ecological groups were delighted by the impending demise of the Santa Maria de Garona plant, which has a uranium-fission powered reactor that heats water to drive a steam turbine.

The Garona plant's operator, Nuclenor, said "regulatory uncertainty" made it impossible to seek an extension to the plant's licence, which runs out in July after already being extended by four years in 2009.

The deadline for lodging the request was Wednesday.

Nuclenor, equally owned by Spanish energy groups Iberdrola and Endesa, had asked for more time to make the request because it was waiting for details of the government's energy market reforms.

The reforms, including possible tax and tariff increases for some energy sectors including the nuclear industry, have yet to be agreed, reportedly because of a dispute among key ministers.

Greenpeace welcomed the news of the expected closure of the plant, which environmentalists say is of the same design as the doomed Fukushima installation.

"The decision of the electrical power groups to not seek an extension shows the economic failure of nuclear energy, despite government support," Greenpeace said in a statement.

The licence would expire on July 6, it said, calling for a new protest at the plant, near the northern city of Burgos, on Sunday to call for its immediate, permanent closure.

A massive earthquake off Japan in March 2011 created a tsunami that swamped the Fukushima Daiichi plant, sending three reactors into meltdown, spewing radiation over a large area and forcing the evacuation of thousands of people.

Spain has six nuclear plants with a total of eight reactors.