The weiben sumpfe of wittmar
On this map, the radioactive sumps from the 750-meter bottom of the nuclear waste repository have been projected onto the earth’s surface.
A brief history of the Asse II nuclear waste repository
The underground salt mine
There is a skyscraper in Germany that you can walk on but never see in full size. It is camouflaged by a wooded hill that rises about seventy meters from the Lower Saxony farmland: The Asse. A few kilometers to the northwest lies Wolfenbuttel, the city center of Braunschweig can be reached by car in just under half an hour, and to the south the pale blue silhouette of the Harz mountains with the Brocken can be seen. A walker on the eastern section of the Asse Ridgeway has the houses of the community of Remlingen in his sights, but is probably not aware that he is walking in the immediate vicinity of the invisible building. If he wanted to visit it, he would have to take an elevator 750 meters underground. There is the first floor with 12 spacious rooms, each 60 meters long, 40 meters wide and 15 meters high.
Similar to a parking garage, a five-meter-wide "spiral staircase" leads up through all thirteen floors to the roof chambers of the 650-meter-long and 260-meter-high underground structure. An extensive network of paths branches off from the spiral staircase and connects the floors that have been carved out of a massive salt dome. It is the mine building of the former Asse II salt mine. Hardly any visitor is really prepared for the heat down here. In this dry and harsh salt desert climate, one would like to rub off the visitor’s clothes after the first tentative steps, although a huge fan provides a constant flow of fresh air from the Remlingen Biosphere. The finest salt dust swirls in the circulating mine air. It settles on skin and lips and burns in the corners of the eyes. You can taste it on your tongue.
The huge cavities in the vertically piled up salt massif were created between 1909 and 1964, when rock and potash salt was mined here. Potash mining was already no longer profitable in the 1920s. Inflation and the loss of the German potash monopoly have left their mark on the southern slope of the Asse mine. But even the table salt brand "Asse-Sonnensalz" did not establish itself permanently on the market. And this is how the Wintershall Group – pronounced Winters-Hall – as owner sold its Asse II mine to the Federal Republic of Germany in 1964. This marked the end of "positive mining" in the shaft. This is what miners call the extraction of ores and minerals from the mountain to the earth’s surface. During the full employment and economic growth of the 1960s, the first German nuclear reactors produced supposedly cheap electricity.
The numbers were impressive. Economists and politicians went into raptures because, compared with the same amount of coal, one kilogram of uranium dioxide could generate 140,000 times more energy. The only small flaw was that the production of electricity from uranium produced non-recyclable radioactive residues that had to be stored safely for some time. Apparently it was a matter of a few hundred years. Some busybodies talked about ten thousand years, but such exaggerations did not have to be taken seriously.
The optimism about scientific and technological progress of his time had also rubbed off on the nuclear physicist and philosopher Carl Friedrich von Weizsacker. At the end of the 1960s, he calculated on the basis of expert forecasts that all the nuclear waste present in Germany in the year 2000 could be packed into a cube 20 meters on a side and disposed of in a dry mine without any problem. And were there not cavities with a volume of more than three million cubic meters gaping in the desert climate deep below the Asse, which now belonged to the federal government?
The nuclear waste high-rise leans against the porous Carnallit saddle. The storage chambers are marked in red.
A single salt mining chamber already offered a holding capacity of 36.000 cubic meters. There the paltry 8.000 cubic meters arrive quietly in Weizsacker’s box. And this is how "negative mining" began in the Asse in 1967: Hazardous foreign substances were brought underground from the technosphere of man and stowed in empty mining chambers. For research purposes, as it hieb.
All options were kept open with the official phrase "experimental disposal". This verbal salto mortale might be interpreted by optimists and the gullible as meaning that the radioactive waste would be taken away again as soon as sufficient knowledge had been gathered against final disposal in salt. In the meantime, skeptics wondered how it would be possible to successfully "attempt" final disposal without actually carrying it out to the end, i.e., forever. From their point of view, an experimental final disposal was de facto a final disposal. Otherwise, those responsible would have had to speak of interim storage.
Here, in the cavities of Asse II, negative mining has meanwhile taken on a dimension that is unprecedented worldwide and will continue to occupy many future generations of people. About 125.000 barrels of low-level radioactive waste and 1300 barrels of medium-level radioactive waste were driven into the salt between 1967 and 1978. Here we are talking about substances that still pose a danger to living beings after several hundred thousand years. So let’s talk about plutonium. Officially, there are about 12 kilograms of this highly toxic substance distributed over several thousand barrels in the Ace salt. This element is present in the earth’s crust in barely measurable quantities. And in view of the small amount of uranium decay that occurs during the operation of a nuclear power plant, an officially admitted 12 kilograms as nuclear waste components is an astonishingly coarse quantum. This figure also sparked fears, which have never been silenced, that highly radioactive waste might have been stored in secret and falsely declared.
If a person inhales dust containing only a few millionths of a gram of plutonium, the radiation is trapped in his body and can unfold without constraint, inevitably leading to lung cancer. So the human body reacts with gross misunderstanding to radioactive decay. The radiation released in the process does not actually have any malicious intentions. It only wants to spread as unhindered as possible and enforces its unrestrained expansion policy quite impressively. If matter stands in its way, by which it is easily slowed down, it makes its rude comments. It prefers to communicate with living beings on the molecular level and leaves behind in tie, organs and genetic material ingeniously coded information with which the value-conservative DNA knows nothing. And so the body counters with helpless maneuvers and suicide missions like bone atrophy and blood cancer.
There are at least four different plutonium otopes in the ace. Isotopes are atomic nuclei of the same element, but with different numbers of nuclear building blocks.So we have here a plutonium assortment with 238, 239, 240 and 241 nuclear building blocks. The respective share of these plutonium isotopes in the total amount of almost 12 kilograms is unknown. Plutonium-239 has the highest half-life. Ideally, if the twelve kilograms were divided "fraternally" by all four isotopes, there would be three kilograms of plutonium-239 with a half-life of 24,000 years. For comparison: The Nagasaki atomic bomb "Fat Man" contained 6 kilograms of plutonium-239. Now it takes 24.000 years, so many atomic nuclei of this isotope will have transformed into nuclei of other elements that half of the original mass, one and a half kilograms, will still be present.
After 48.000 years, according to statistical decay probability, there will still be 750 grams of plutonium in the Asse, and after 100.000 years, there will still be about 180 grams. A half-life of 24.000 years does not mean – as is often wrongly concluded – that after 48.000 years, there is no longer any need to fear dangerous plutonium radiation. It depends on the quantity concentrated in one place. If one calculates here with the half-life of 24.000 years, there are still about 180 grams of mass left in 202.008, about 10 grams of the amed three kilograms of plutonium-239 will still be left. With a threshold of about 25 millionths of a gram for triggering lung cancer, even another 100,000 years later, it is far from being possible to speak of the one harmless Amount of this material speak. And that is why plutonium dust in the Asse represents a realistic risk potential for several hundred thousand years.
Such periods of time are a huge, hardly imaginable order of magnitude for human culture. It becomes even more absurd when politicians and scientists want to take responsibility for this period in advance and claim that they can safely store nuclear waste for such a long time that no one will be harmed. Forty years ago, at the beginning of the "experiments" with nuclear waste in the Asse, people relied on the plasticity of salt, on its tendency to crawl into cavities and to remain in them.
The salt, so the brash thesis goes, will float around the nuclear waste drums and keep them firmly in the mountain and permanently away from the biosphere. Experts and representatives of the people unanimously guaranteed, against their better judgment, that the old salt mine was sufficiently stable. However, the geodynamic forces are disturbed exactly where intensive mining was carried out. Here there are artificially created, complicated interactions between rock layers and groundwater flows due to human intervention. Whoever therefore gives guarantees for the stability of old mine buildings is entering – literally – fragile terrain. Because nothing is really rigid. Everything gets into motion at some point.
Even if it is impossible to imagine a few hundred thousand years of future human history, from a geological perspective, the same period is in fact not yet a significant period in which significant changes in the earth’s crust would occur. They only emerge when we look further back into the past. About 250 million years ago, northern Germany was not flooded for the first time by a shallow sea. Back then the continents did not look like we know them today. There was a time when the territory we now call Germany was located near the equator. Under subtropical heat and extreme drought, the seas evaporated more rapidly. They came and went in constant succession and left behind mighty salt deposits north of the Harz Mountains in the course of many millions of years.
Then came the stones. Shell limestone and red sandstone slid over each other. Compliant was pulverized. Rigid overburden gave way and collapsed. Rock weathered by water, ice and wind has been pushed underground by lagging boulders, followed by layers of gypsum, flame marl and foliated clay. And underneath, the glittering female crystal desert sank into the depths with it.
Under the prere of the overburden, the salt of the many seas, long since evaporated, reacted plastically and crept, slowly but inexorably, with its lower specific gravity upward, toward the younger rock layers, which readily crumbled and collapsed on top of each other. Thus, the salt was able to rise along a fracture zone to near the surface of the future Braunschweig land. Above this, a gypsum cap formed, covered by discarded red sandstone clods: the Assehugel (Asse Hill). This happened about 100 million years ago. At that time, our ancestors were audacious small rodents that had to seek cover in the hunting grounds of the predatory dinosaurs of Lower Saxony and hunt for their daily survival rations of flies and worms.
Shortly before, they had courageously turned off a broad evolutionary path that was to lead their less risky cousins, after curious failures, to the extremely successful genus of mice. Our ancestors scurried at best as hamster-like quadrupeds through the feathery undergrowth of the Cretaceous.
Since then, the asse mound has been resting, seemingly immobile, in the landscape between the Harz Mountains and the heath. But appearances are deceptive. It rumbles underground, albeit with a monstrous inertia for which the nervous human senses, accustomed to constant stimuli, are unprepared. From the perspective of geological history, however, the rocks are constantly in motion. Surface rocks sink into the earth’s interior in an incredibly leisurely cycle. Here it is transformed under heat and prere. Granite becomes gneiss, limestone advances to marble, while layers of clay undergo tough metamorphosis to form slate. Then the stones come back to the earth’s surface, weather and turn to dust. It is carried away by the wind and enriches itself in another place, possibly to topsoil, an integrated development environment for the first, let’s say: Forest strawberry of history.
Even salt is still rising today. Although even the most attentive human observer would not perceive any dramatic unrest at the Asse site over a long period of time, the salt massif stands in a field of tension between different geodynamic forces. Gravity, friction and water prere take their toll. From above, heavy overburden weighs on the lighter salt. When it rains, the water seeps into the ground. In the gravel, sand and limestone near the surface, as well as in the porous gypsum cap that sits on top of the salt, the groundwater ripples through fires and cracks in the rock at a flow rate of a leisurely 5 to 100 meters a day and seeks new paths for itself. The mechanical forces and stresses in the rock take on an additional dimension when people drill elaborate holes in the earth with remarkable zeal in order to access the mineral resources.
Potash salt mining in the Asse began in 1883 with test drilling in Wittmar, a small community on the southern slope of the mountain range. This is also where construction work on the Asse I shaft began in 1899. Two years later, a factory was already standing on the site of the mine, where the crude salt was processed into ready-to-use potash fertilizer. It was the high time of the German potash salt industry. For almost a thousand years, miners in the rock salt mines had regarded the orange-red, brownish and amber veins of this bitter mineral as troublesome impurities and thrown it into the dumps as waste. But then the German chemist Justus von Liebig discovered that potassium salt, together with phosphoric acid and nitrogen, was one of the three most important nutrients for plants.
In 1977, the chlorinated potassium factory on the Asse I mine site was demolished
With the dawn of the artificial fertilizer era, Germany, chronically poor in raw materials, suddenly found itself in possession of the most important potash salt deposits, supplying 99 percent of the world’s potash fertilizer needs. In addition, potash served the emerging chemical industry as an important raw material for the production of paper, paints, soaps, bleaching agents and later also plastics. And now the Asse union as operator of the plants in Wittmar also wanted to profit from this national boom.
The name Wittmar means female swamp. The Settlers in 13. The nineteenth-century people who gave the place this name will not have known that they were squatting here over the soft legacy of evaporated seas. In the world view of the High Middle Ages, continents and oceans had only recently been created by God exactly as they were found. Developments and changes in the earth’s crust were not foreseen in the history of creation. But the fossilized fragments of crinoids, shells, snails and ammonites could hardly have been overlooked by the newcomers plowing their fields at the edge of the village. Even today, fossils can be found in the fields near Wittmar, testifying to the marine past of this stretch of land. In the short years of the potash boom, the small farming village grew rapidly into a mining settlement.
But after only four years of potash mining, water began to seep from the overburden into the chambers of the 300-meter level, presumably due to improper salt mining. A year later, in July 1906, the Asse I mine was filled with water and had to be abandoned. The repository engineers should therefore have this mighty, five-million-cubic-meter water reservoir in the immediate vicinity of the radiation dump as an instability factor in the Asse subsurface on the calculation.