According to Wikipedia, Asse, a.k.a. “Asse 2” because of an original Asse shaft dug there in 1906, is an old salt mine in Lower Saxony that was turned into a West German research mine in 1965 and also used as a permanent storage site for nuclear waste between 1967 and 1978. Politicians assured the public the mine’s known water problem could be reliably stopped forever, and lawsuits to prevent the project failed in court.
Low-level radioactive waste with particularly long-lived isotopes and medium-level radioactive waste with short-lived isotopes was stored there, in metal drums that were supposed to be used as transport, not permanent, containers. In the first phase of the experiment, the drums were stacked on one another. In the second phase the drums were stacked horizontally, like a woodpile. In the third phase, drums were dumped off an underground cliff and then rock salt debris was dumped on them. It is now known that metal drums last only a few years to decades when exposed to salt water, and these metal drums may have been further damaged by how they were placed into storage. Hydrogen is possibly forming.
No fees were collected for nuclear waste delivered between 1967 and 1975. In 1975 the law changed—“permanent storage” was not defined in German law until 1976, for example—after which Asse collected a total of about 900,000 euros in fees until the research program on permanent nuclear waste disposal ended in 1995. Asse’s remaining open caverns were carefully filled in with trainloads of rock between 1995 and 2004.
In 2008 it became known that Asse 2 was in danger of collapse due to water seepage and cracking, not surprising due to its history and the fact that its salt ceilings have been deforming by up to 15 cm/year for many years now. A state investigation was started and found, among other things, that radioactive salt water was first detected in the mine in 1995. Two billion euros are now budgeted for the cleanup, though experts estimate the cost will be closer to six billion. The site’s recent budgets exceeded 100 million euros/year, used for maintenance and public relations, reported ZDF heute journal, which broadcast disturbing photos of the damage in this report from 05 Oct. 2012. ZDF says the plan is to drill a new tunnel and remove the nuclear waste through it, though that might not be possible. It has been estimated the ceiling rock will start to fail in early 2014, and that cleanup can’t be started before 2036.
Update on 04 Mar 2014: New environmental minister Barbara Hendricks visited Asse for the first time. About twelve thousand liters of water are seeping into the nuclear waste storage site there each day, said ARD tagesschau.de, which is why the Bundestag voted one year ago to move Asse’s nuclear waste as quickly as possible, to protect local groundwater from radioactive contamination. During her hard-hatted and overalled inspection of the underground chambers, Minister Hendricks said she didn’t think the work could be easily speeded up because more than <120 people cannot be in the old salt mine at a time for safety and technical reasons. Local people are demanding that a second shaft be built immediately, to finish the cleanup before the old tunnels collapse.