In the depths of Peter Uerpmann's collection we came across a block of massive crystalline halite - rock salt.
The locality is given as Asse II, probably picked up during his time as a worker in the German Nuclear industry.
Asse (Shaft) II is situated in the Asse Mountains of Wolfenbüttel, Lower Saxony, Germany. It was opened and operated as a potash mine from 1906 to 1908, before being developed into a salt mine operational between 1916 and 1964.
After salt production ceased the mine was acquired and was re-used as a repository for low to medium level nuclear waste. At the time the deep and large cavities beneath the salt dome geological feature were thought an ideal place for this type of use.
Time Line for Nuclear Waste Storage at Asse II (courtesy of Bellona.org)
Waste was generally stored in sealed drums within levels in the mine deeper than 500m. This continued between 1965 and 1995, after which time the cavities have been back filled with salt as a dry operation.
Storage of Nuclear Waste at Asse II (courtesy of Bellona.org)
Salt mining is traditionally structurally unsupported and the resulting stresses created in the remaining salt structure during mining mine cavities are carried by overhead rock. Natural features of the salt dome geology are also factored into the mine engineering, however reports on mechanical stress and movement suggest the overlying rock is moving at 15cm per annum, weakening the whole mine.
Due to this deformation water is now flooding into the mine and of course risks contributing further to the loss of stability – to the point where it is in danger of falling in.
Historically, between 1906 to 1988 there have been 29 water breaches. Sometimes sealed off, partly dry or with negligible inflows.
Since 1988 (to 2008) this has increased to 32 new breaches. As a counteraction the brine is collected and pumped before it reaches the deeper storage areas.
The pumped brine is tested for radiation, and thankfully to date all values have been below the detection limit.
The brine is pumped into tankers and moved to the abandoned K+S AG mines (Bad Salzdetfurth, Adolfsglück and Mariaglück). The brine in Mariaglück is also tested for radiation.
In 1979 a report on the stability of the mine was released by a working group, this describes an imminent scenario of uncontrolled plastic flow from the surrounding rock on the southern flank resulting in the subsequent possible collapse.
The management of Asse II categorised this report as "unscientific" and declared that there were no stability problems.
In 2007 the Institut für Gebirgsmechanik (IfG) in Leipzig, which had been monitoring Asse II since 1996, predicted that an increase in the rate of loss of load carrying capacity would result in an increased displacement of the surrounding rock. The shifts would lead to an uncontrollable increase in water inflow and make continued dry operation impossible.
On 8 September 2008, the responsible ministers of Lower Saxony and the German government replaced the operator with the Federal Office for Radiation Protection (Bundesamt für Strahlenschutz (BfS)).
In 2009, Greenpeace published a letter written in 1996 from this authority to the German Bundesumweltministerium in which it warned there is the risk of severe radioactive contamination if the mine floods and that further investigation is urgently needed.