Uranium Mining in Eastern Germany:

The WISMUT Legacy

by Peter Diehl

(last updated 17 Apr 2011)

Contents

Immediately after the end of World War II, the Soviets started exploration and mining of uranium in the historic mining provinces in the Ore Mountains. Subsequently, the Wismut company developed the third-largest uranium mining province of the world (after the US and Canada) in the Southern part of the German Democratic Republic. Information on this huge operation was not publicly accessible until the young peace and environmental activist Michael Beleites published his famous underground report "Pechblende - Der Uranbergbau in der DDR und seine Folgen" (Pitchblend - Uranium Mining in the GDR and its Impacts) in 1988 [Beleites1988]. With the political changes in 1989, it came to light to the larger public that in Eastern Germany large areas had been devastated for the production of the source material for the nuclear bomb. With the unification of Germany in 1990, uranium production was terminated. What is left over, are the huge shut-down uranium mines, hundreds of millions of tonnes of radiating waste rock and uranium mill tailings, presenting health risks through release of radon gas and contaminated seepage. This legacy does not only present an immediate hazard, but also endangers future generations for tens of thousands of years. Reclamation is underway to contain the hazards, but questions remain concerning the long-term effectiveness of the measures being taken.

Between 1946 and 1990, Wismut produced a total of around 220,000 tonnes of uranium. During peak times, production exceeded 7000 tonnes per year. For subsequent processing, all uranium produced was delivered to the Soviet Union. Initially, the uranium produced was exclusively used for nuclear weapons; later it was also used for nuclear power plants.

"Wismut" is the short name of the company.

From 1946 to 1953, it was a Soviet stock corporation; so the complete name was "SAG Wismut", where SAG stands for Sowjetische Aktiengesellschaft, and Wismut is the German name for bismuth - it was used to conceal the true purpose of the enterprise.

From 1954 to 1991, it was a joint Soviet-German stock corporation (50% / 50%); so the complete name was "SDAG Wismut", where SDAG stands for Sowjetisch-Deutsche Aktiengesellschaft.

In December 1991, the company was completely taken over by the government of then united Germany and was converted to a limited company; the name thus is now "Wismut GmbH ", where GmbH stands for Ltd. But during all these years, the company was usually referred to as simply "Wismut".

Wismut's staff in the early years is estimated to have been up to 130,000, among them many in forced labour. In the mid-eighties, the staff figures were around 27,000. More than 400,000 people have been working with Wismut at one time or another.

At the end of 1990, uranium mining was discontinued as a consequence of the German unification. Since 1991, Wismut carries out the work necessary for shut down and reclamation with drastically reduced numbers of employees (mid-1998: 3500). The government estimates the clean-up period at 10 - 15 years, at costs of DM 13 billion (US$ 9.3 billion). Since no reserves were saved by the former operators, the clean-up has to be funded from the Federal budget. Until end-1998, DM 5.7 billion (44%) have been spent already.

In the beginning, Wismut's uranium mining focused on the locations Johanngeorgenstadt / Aue / Schlema in the Saxonian part of the Ore Mountains, later also on Ronneburg in Eastern Thuringia, and Freital / Dresden-Gittersee and Königstein near Dresden. In addition to these major sites, there exist many other places where uranium was explored or temporarily mined.

Map of locations

The contents of uranium of the ore extracted by Wismut was 251,000 tonnes; the amount of uranium produced in concentrate form from the ore was lower, due to production losses. The production figures of the various regions are shown in the following table [Hähne1993]:

Uranium Production of Wismut (1946-1990) Location Ore deposit type Uranium produced (in ore) Ore Mountains / Vogtland Hydrothermal 103,000 t 41.0% Ronneburg Sedimentary metamorphose Paleozoic 113,000 t 45.0% Culmitzsch Carbonate Zechstein 12,000 t 4.8% Dresden / Freital Lower Permian coal 4,000 t 1.6% Königstein Cretaceous sedimentary 19,000 t 7.6% TOTAL 251,000 t 100%

The uranium was mined in open pits and in underground mines. The largest open pit called "Lichtenberg" is located near Ronneburg. Its initial depth was 240 meters; after being partly refilled, the depth was still 160 meters at an open volume of 80 million m3 in 1990. After depletion of the ore deposits located near the surface, mining continued at this place to depths of 500 meters. In the Ore Mountains, depths of 2000 meters were even reached; due to the high temperatures at these depths, the mines had to be air conditioned at high cost.

During the early years, the ore extracted was processed in small mechanical processing plants located near the mines. From the 1950's, processing was concentrated in two large uranium mills including chemical treatment in Crossen near Zwickau and Seelingstädt near Gera/Ronneburg. In addition, two smaller mills were in operation in Freital and Dresden-Gittersee until 1962.

A special case is the Königstein mine. This underground mine was switched to in-situ leaching in the early eighties: the ore was no longer removed from the deposit, but sulfuric acid was injected into the ore deposit to leach the uranium on site.

The grade of the ores produced by Wismut in the last years was only around 0.07% uranium, a comparatively low value. Correspondingly, mining cost and amounts of waste and tailings produced were rather high. In 1990, Wismut's production cost of DM 380.50 per kg of uranium was nearly ten times the world market price of then 10 $/lb U3O8.

During the early "wild" years of uranium mining, protective measures for the miners were very poor. Miners in these early years thus took the highest risk of contracting lung cancer. In the year 1955, radon concentrations in Wismut's mines typically were approximately 100,000 Bq/m3, with peaks of 1.5 million Bq/m3 [Jacobi1992]. Detailed information about the early years of Wismut mining can be found in [Beleites1992], [Paul1991], or [Karlsch1993], for example.

From the end of the fifties, the ore was kept wet during drilling to avoid generation of dust, and the mines were intensively ventilated to lower the radon concentrations. The doses received from radon decay products thus decreased from 150 WLM to 4 WLM per year (WLM = Working Level Month is a unit for the dose from radon decay products, which are causative for cancer development).

According to [Jacobi1992], the doses received in Wismut's mines in the early years should not be estimated at 150 WLM, but at 200 WLM per year. The true value can hardly be determined, since Wismut never performed direct individual monitoring of the doses received by the miners. Before 1955, no monitoring was performed at all - only estimates can be made for this early period. Later, radon decay product concentrations were sampled at representative locations within the mines for short periods of time. The doses received by the miners were calculated from these sampling results. While this method allows a certain overview on the doses received, its results cannot be compared with those of continuous individual monitoring.

Between 1946 and 1990, 7163 uranium miners who had been employed with Wismut died from lung cancer. For 5237 of them, the occupational exposure was recognized as the cause of the disease. At present, still approx. 200 lung cancers of former Wismut miners per year are recognized as occupationally caused [AKURA2000]. Until mid-1990, the limit for recognition was 450 WLM; then it was lowered to 200 WLM. One year of work in the uranium mines during the early years is therefore already sufficient to attribute an observed lung cancer to the occupational exposure.

An assessment of international studies on lung cancer incidences with uranium miners showed that with reference to age at exposure and age at cancer incidence, even a total exposure of only 40 WLM can be sufficient to be regarded causative. Such a dose could also be obtained by work exclusively during the mine's later years, while the recognition was so far granted only for work during the mine's early years. At exposures of 150 WLM and higher, an observed lung cancer can be attributed to the work in the uranium mines, practically independent of the exposure history. [Jacobi1992] (view details)

Further studies showed that also the risk of contracting cancers other than lung cancer is elevated for uranium miners, in particular for cancer of the mouth region, pharynx, and larynx, bone cancer, leukemia, and liver cancer [Jacobi1995] [Jacobi1997] (view details, see also Uranium Miner Health Risk Calculator). The employers' liability insurance association (Berufsgenossenschaft), however, does not recognize these studies as sufficient to prove that exposure in the mines may have been causative for any such non-lung cancer contracted [AKURA2000] [Eigenwillig2011].

Radon and dust, blown out by the mine's ventilation, do not only cause direct dose loads for the residents by inhalation: an investigation of various food samples grown in the Ronneburg (Thuringia) uranium mining district showed that by the consumption of local food the highest dose by far of 0.33 mSv (33 mrem) per year is caused from wheat grown near a ventilation shaft [Schmidt1994].

Large amounts of groundwater were pumped out of the mines, to keep them dry during mining operations. The water was released into rivers and creeks. In the sediments of rivers in the Ronneburg area, concentrations of radium and uranium around 3000 Bq/kg were found, indicating up to 100-fold increases over natural background [Hanisch1994].

In the old mining areas in the Ore Mountains, the problems resulting from uranium mining are commingled with those resulting from historic mining - mining haven taken place in the medieval age. In Schneeberg for example, extremely high concentrations of radon are found in homes: in living rooms, 20,000 Bq/m3 are not uncommon, while up to 100,000 Bq/m3 are found in basements [Keller1991]. These levels are, in part, caused by the direct access to former underground mine workings existing in the basements of many houses, or by other radon pathways from the mines to the basements. Since there is no scientific consensus on the lung cancer risk from such elevated radon levels in homes, a number of epidemiologic studies are being performed worldwide on this subject at present. First preliminary investigations in the East German uranium mining province show elevated lung cancer incidences with men in several towns; they are attributed to occupational exposure in the uranium industry. But, in Schlema and Schneeberg, elevated incidence rates of lung cancer were also found with women [Heinemann1992].

In the Dresden-Freital area, hard coal containing uranium was mined for fuel use from 1542. From 1952-1955 and 1967-1989, the same coal was mined by Wismut for uranium. Consequently, there is also a problem of both wastes from uranium mining, and from historic mining in this area, especially from the coal ashes.

All these piles present hazards to residents and the environment, even after the shutdown of the mines, due to their release of radon gas into the air, and to their release of toxic and radioactive contaminants by seepage into groundwater.

The waste rock piles of the uranium mines in the Schlema/Aue area contain a volume of 47 million m3 and cover an area of 343 hectares. The waste rock often was dumped on the valley's slopes. In many instances, they are located in the immediate neighbourhood of residential areas. Consequently, high radon concentrations in free air around 100 Bq/m3 are found in large areas of Schlema, in some quarters even above 300 Bq/m3. The independent Ecology Institute has calculated a lifetime excess lung cancer risk of 20 cases (and 60 cases respectively) per 1000 inhabitants from these concentrations [Küppers1994]. This is the extra risk caused from radiation, in addition to the risk caused from natural background or other sources. Moreover, much higher peak concentrations of radon may result from climatic inversion conditions in the narrow valleys.

View Waste rock piles at the valley slopes of Schlema (before application of cover - May 1991) (19k)

For the southern parts of the town of Ronneburg, the Ecology Institute calculated a lifetime excess lung cancer risk of 15 cases per 1000 inhabitants. Since radon spreads rapidly with the wind, the risk must also be considered for the residents in the wider surroundings: the Ecology Institute calculated an excess lung cancer incidence of 6 cases per year within a radius of 400 km. [Küppers1994]

View Waste rock pyramids of Ronneburg (36k)

Seepage is another problem presented by the waste rock piles; in some cases, even creeks were simply buried under the piles. The seepage releases of the waste rock piles in the Schlema/Aue area are estimated at 2 million m3 per year, half of which flows into groundwater. Only a small fraction of the other half is captured at the foot of the piles.

So-called waste rock was often processed into gravel or cement for use in road and railroad construction. The Saxonian Hartsteinwerke Oelsnitz alone, for example, have processed 7.58 million tonnes at uranium concentrations of up to 100 g per tonne. Baukombinat Zwickau used 14.4 million tonnes of material from the waste rock pile of the Crossen uranium mill for road construction, at uranium concentrations of up to 150 g per tonne and radium concentrations of up to 1.3 Bq/g. The radioactivity thereby was dispersed over large areas. For some part of the material, a follow-up of the use is not possible.

Heap leaching of low grade ores with sulfuric acid was performed on a large scale at Wismut's Gessental-pile at Ronneburg (7 million tonnes) and in Königstein (2 million tonnes).

During operation, these heap-leaching piles present hazards due to the release of dust, radon gas and, possibly, leaching liquid seepage. After termination of the operation, a permanent hazard may persist due to natural leaching processes taking place, if the material piled up contains the mineral of pyrite (FeS 2 ) - as is the case for the Thuringian ores: Then, precipitation together with inflow of air can cause the continuous formation of sulfuric acid within the pile, leading to a permanent leaching of uranium and other contaminants, presenting a groundwater hazard for centuries.

In Saxony, an underground mine converted to an in-situ leaching facility was in operation at Königstein near Dresden until end 1990. On a small scale, in-situ leaching was also used in the Ronneburg (Thuringia) uranium province.

In the case of Königstein, a total of 100,000 tonnes of sulfuric acid was injected with the leaching liquid into the ore deposit. At present, 1.9 million m3 of leaching liquid are still locked in the pores of the rock leached so far; a further 0.85 million m3 are circulating between the leaching zone and the recovery plant. The liquid contains high contaminant concentrations, for example, expressed as multiples of the drinking water standards: cadmium 400x, arsenic 280x, nickel 130x, uranium 83x, etc. This liquid presents a potential hazard to an aquifer that is of importance for the drinking water supply of the region.

The largest such settling ponds in Europe are the Culmitzsch tailings dam near Seelingstädt (Thuringia), containing 90 million tonnes of solids, and the Helmsdorf tailings dam in Oberrothenbach near Zwickau (Saxony), containing 50 million tonnes of solids. The Culmitzsch dam was erected on the site of a mined-out open pit uranium mine, the capacity of which was enlarged by additional dams. The Helmsdorf dam was erected as a barrier on the place of the village by the same name, which was completely destroyed for the dam.

View Culmitzsch tailings dam (partial view of the two impoundments with separating dam, before covering of dry beach, September 1990) (13k)

Uranium Mill Tailings in Eastern Germany Location Solids contents

[million tonnes] Surface

[ha] Culmitzsch 90 250 Helmsdorf 50.3 192 Trünzig 19 116 Dänkritz I 5.6 19.5 Dresden-Gittersee 3.4 29 Lengenfeld 2.4 14 Schneckenstein 1.2 6 Dänkritz II 0.8 7 Oberschlema 0.4 Schlema-Borbachtal 0.3 Johanngeorgenstadt 0.3 Freital 0.3 Total 174 approx. 650

Apart from the uranium, the tailings contain all constituents of the uranium ore. This also implies that the tailings still contain 85% of the radioactivity contained in the ore, as the long-lived decay products of uranium, thorium-230 and radium-226 are not removed. Since the uranium cannot be recovered completely from the ore during the milling process due to technological constraints, the tailings, moreover, contain 5 - 10% of the uranium initially present in the ore.

The radium-226 contained in the ore decays to the radioactive gas radon-222. A part of this radon escapes from the tailings deposit into the atmosphere. Although radon-222 has a comparatively short half-life of 3.8 days, it presents a long-term hazard, since the decay of radium-226 - with its half-life of 1600 years - constantly produces new radon-222. In addition, the tailings also contain the predecessor of radium-226 in the decay chain, thorium-230. It decays at a half-life of 80,000 years, constantly producing new radium-226.

Apart from the radioactive constituents, the tailings also contain other contaminants that were present in the ore, for example, arsenic, or various other heavy metals. The Helmsdorf tailings dam alone, for example, contains 7590 tonnes (!) of arsenic.

All these hazardous substances have been removed from their safe underground disposal and have been brought to the form of a fine sand or slurry. The contaminants thus are now much more mobile and susceptible to release into the environment. In addition, the mineral pyrite (FeS 2 ) - as contained in Thuringian ores - forms sulfuric acid inside the deposit when accessed by precipitation and oxygen. This acid causes a continuous automatic leaching and subsequent release of contaminants.

The sky darkened over the villages in the neighbourhood of Wismut's uranium mill tailings dams, when storms blew the sands from the dry tailings beach. Consequently, elevated concentrations of radium-226 and arsenic were found in dust samples from these villages. Meanwhile, the dry tailings beaches have been covered with neutral material to prevent further wind erosion.

The dams of uranium mill tailings deposits are often not of a stable construction: in most cases, they are not built as engineered structures, but by piling up of the coarse fraction of the tailings slurries themselves. An assessment of dam stability thus is subject to great uncertainties. Moreover, the dams are raised sequentially, following the rising elevation of the impounded tailings during the filling process. (view details on tailings dam safety)

Some dams (among them those of Culmitzsch and Trünzig in Thuringia) are built on geological faults and are located close to the center of seismic activity in the Eastern part of Germany. They are therefore at a specific risk during earthquakes. The main dam of the Helmsdorf tailings deposit, with its height of 59 m, does not even meet the safety margins of the German dam safety standards. In the case of a dam failure, large parts of the village of Oberrothenbach would be flooded by the slurries. 1000 people are living in the immediately threatened area, 6500 more are living in the potential flooding area.

View Dam of Helmsdorf uranium mill tailings deposit (24k)

Dam failures can also be caused by heavy precipitation events with excessive rises in the level of the water ponding above the slurries in the impoundment. In May 1994, the water level in the Helmsdorf dam approached the limit with 6 cm to spare. For this reason, an additional protection dam was built on the deposit in Spring 1995, to prevent water from reaching the main dam. Moreover, a water treatment plant was taken into operation in 1995, allowing for the lowering of the water level and thus for a decrease of the risk of dam failure.

Toxic waste was dumped on the surface of the Trünzig A uranium mill tailings pile in Thuringia before the political changes. It was intended to cover this toxic waste by another 5 m layer of domestic waste; but this was prevented by residents' protests.

1 million m 3 of domestic waste and ash was dumped on the top of the tailings deposit of the Dresden-Gittersee uranium mill, which was shut down in 1962.

of domestic waste and ash was dumped on the top of the tailings deposit of the Dresden-Gittersee uranium mill, which was shut down in 1962. Liquids presenting a hazard to water were dumped on the top of a waste rock pile at Ronneburg (Thuringia) after the political changes. These liquids must now be removed and disposed of at high cost to allow for reclamation of the pile.

Radioactively contaminated metal scrap from the decommissioning of the Crossen (Saxony) uranium mill is to be dumped in the Helmsdorf tailings dam.

Correspondingly, a standardized concept for the reclamation tasks to be done in Eastern Germany is lacking. Reclamation action was started without sufficient analysis and consideration of management alternatives. There didn't even exist a standardized procedure for hazard assessment at the various sites; only gamma radiation was monitored systematically.

According to the German Unification Treaty, the West German radiation protection regulations are not adopted for the East German uranium province, but the German Democratic Republic (GDR) regulations remain in force. Thus, an annual dose of 1 mSv (100 mrem) instead of 0.6 mSv (0.3 for the aquatic and 0.3 for the atmospheric pathway) is admissible. The calculation rules of the GDR regulations, moreover, result in much lower radiation doses for a certain amount of activity ingested, and therefore allow for much higher radiation uptake to obtain the same doses [Küppers1991]. The annual dose limit of 1 mSv means that one lifetime incidence of cancer is regarded acceptable per 286 persons concerned.

Several communities and individuals have filed a suit at the Federal Constitutional Court against this provision of the Unification Treaty. The suit has been accepted for decision, but judgement is still pending.

For the reuse of contaminated material and areas, various recommendations have been elaborated by the German Radiation Protection Commission (SSK ) [BMU1993]. They are based in principle on an excess annual dose of 1 mSv for the public. But, this limit does not include the dose from drinking water contamination (another 0.5 mSv) [SSK1993t], and from radon in homes. SSK's recommendations are, moreover, based on different calculation rules for the doses resulting from ingestion with food and water, than used in the West German radiation regulations; thus, higher radionuclide uptakes are admissible, until the limit is exceeded [Küppers1994]. For the most problematic issues - the management of the uranium mill tailings and in-situ leaching facilities - there are no recommendations at all.

Wismut is only responsible for the reclamation of those sites that were not returned to the local authorities before 1962. The communities are responsible for the other sites, but they are not nearly able to pay for their reclamation. They don't receive compensation for their former Wismut sites from the Federal Budget. (See also: Altstandorte des Uranbergbaus in Sachsen (30k PDF, in German))

Another problem is the access to environmental data gathered about the aftermath of uranium mining. For those sites that are still owned by Wismut, the data is gathered by Wismut itself; for those sites that were returned to the local authorities before 1962, the Federal Radiation Protection Agency (BfS ) performs the monitoring. For its sites, Wismut only publishes rather general annual reports , while BfS has published summary information only.

View Lichtenberg open pit (with acces ramp under construction - June 1992; the pit has been partially refilled meanwhile) (12k)

The liquid hazardous wastes that were dumped after the political changes on the Absetzerhalde pile in Ronneburg, need to be removed and disposed of separately, before this pile can be reclaimed. Wismut has built a special toxic waste deposit for this material on its Ronneburg premises. The deposit went partially into operation in October 1999.

The waste rock piles in the Saxonian mining district at Schlema are being covered with neutral material. The slopes of many of these piles are so steep though, that the covers slide in some cases. The long-term performance of these covers is questionable.