A report published in Germany's Focus magazine alleges that authorities in the state of Lower Saxony were aware of safety issues at the Asse II atomic storage facility 15 years ago.
Asse has become the latest focus of the nuclear debate
The Focus report says the state government, led by the Social Democratic Party (SPD) at the time, commissioned a technical report on potential hazards at the converted salt mine in 1991.
After two years of evaluation, experts warned that areas near the south-western edge of Asse were unsafe. Their 1993 report found that up to 4,000 litres of water were flooding into the mine's shafts each day. It recommended that all shafts and caverns less than 750 metres below the earth’s surface should be stabilised to prevent possible collapse.
Focus reports that although SPD leaders in Lower Saxony received an updated report highlighting safety concerns in 1998, they chose to keep the warnings under wraps.
The extent of the safety problems at Asse were made public last week, prompting Environment Minister Sigmar Gabriel to transfer responsibility of the facility from the Munich-based Helmholtz Institute for Scientific Research to the Federal Office for Radiation Protection.
In the 1960s researchers thought salt mines were ideal for storing nuclear waste
Nuclear power is often touted as being clean and carbon-friendly, but opponents point out that no one has yet found a durable solution for storing nuclear waste, which remains highly radioactive for centuries.
Asse was converted into an atomic waste storage facility in the 1960s as a pilot project linked to plans for a permanent facility at another former salt mine at Gorleben, Lower Saxony.
But problems at Asse raise questions about the feasibility of the Gorleben site at a time when Germany’s grand coalition government is split on whether or not to reverse plans to abandon all nuclear power by 2021.
Chancellor Angela Merkel's conservative Christian Democratic Union (CDU), which supports continued use of nuclear power, is worried that Asse will undermine its calls for a rethink of the planned phase-out.
In a radio interview on Sunday, Merkel said there needed to be decisions about what to do with highly radioactive material.
"We do also need to make progress in the storage of highly radioactive material. It's about atomic plants. A moratorium has been agreed for Gorleben and of course decisions must be made on how things go from here," Merkel told Deutschlandfunk radio.
Environment Minister Gabriel has assumed control of Asse
In its latest issue, Der Spiegel magazine quoted a strategy paper in which conservative lawmaker Katherine Reiche demanded that Environment Minister Gabriel immediately lift the moratorium on exploring options for storing atomic waste at Gorleben.
The moratorium is the result of battles between supporters of nuclear power, who unsuccessfully tried to rush through Gorleben's commissioning in the 1970s, and a powerful lobby of opponents for whom the unresolved storage question buys time to discredit nuclear energy.
Der Spiegel reports that a search for alternatives elsewhere, which Gabriel and the Social Democrats prefer, would cost at least one billion euros. If plans for the waste storage facility at Gorleben are given up completely, energy companies could make compensation demands worth billions of euros.