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3. Environmental impacts

Nuclear Monitor Issue: 
Special: Uranium Mining in Europe - The Impacts on Man and Environment


Uranium Mines

(September 1995) Uranium ore is produced in open pit or underground mines. The ore grades often are only 0.1 %; large amounts of ore have to be mined to obtain the amounts of uranium required. In the early years after World War II, uranium was mostly mined from deposits located close to the surface, while mining later continued into the deeper underground. With the decline of uranium prices on the world market, underground mining became too expensive for most deposits, and many mines have been shut down since then.

During the active mining period, large amounts of air contaminated with radon and dust are blown into the open air, for example 7426 million m3 (i.e. 235 m3/s) of contaminated air alone at Schlema-Alberoda (Saxony, Germany) in 1993, with average radon concentrations of 96,000 Bq/m3. While lowering the doses for the miners, these ventilation efforts increase the levels for residents living near the ventilation shafts. These high levels continue after the shutdown of the mines, as long as they are still ventilated during decommissioning works and not yet flooded. In April 1992, the radon levels for residential areas of the town of Schlema in Saxony were significantly lowered by a change of the ventilation shaft: the contaminated air is now blown into open air at a remote place.

In Bulgaria, a shut-down uranium mine is located immediately neighbouring the village of Eleshnitza. It causes high radon concentrations in free air. It is anticipated that 0.3 to 1 lung cancer incidences annually are caused by the mine in the 2600 residents of the village. [Vapirev1994]

From the shutdown uranium mine of Zirovski Vrh in Slovenia, air containing radon concentrations of 5000 Bq/m3 flows into the surrounding valleys and causes high doses for residents, when air exchange is low due to climatic conditions [Peter1994].

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 are pumped out of the mines, to keep them dry during mining operations. The water is released into rivers, creeks and lakes. 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 Czech Republic, a continued contamination of the sediments of the Ploucnice river was caused from the insufficient water treatment of the Hamr I uranium mine water releases before 1989. The river sediments and flooding areas are contaminated over a length of approximately 30 km [Andel1993]. The doses received from gamma radiation, reach peak levels of 3.1 Gy/h; that is 30 times background levels.

In the Lergue river in France, the waste waters of the Le Bosc uranium mining complex (Hérault) have caused concentrations of radium-226 in sediments of 13,000 Bq/kg; that corresponds to the concentrations found in uranium ores [Descamps1988]. From the reference it cannot be concluded whether these levels are caused by the mines themselves, by the uranium mill, or by the uranium mill tailings deposits.

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]. Therefore, a detailed investigation is now being undertaken on the lung cancer risk in homes in Thuringia and Saxony [Heinrich1992].

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.


Waste Rock

Waste rock is produced in open pit mines when removing the overburden, and in underground mines when driving galleries through non-ore zones. Piles of so-called waste rock often contain elevated concentrations of radionuclides compared to normal rock. Other piles contain low grade ores, with grades too low for processing in a mill. The transition between waste rock, low grade ore, and ore is fluent and depends on the technological and economic constraints.

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 immmediate 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.

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]

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 [BT1992a]. The radioactivity thereby was dispersed over large areas. For some part of the material, a follow-up of the use is not possible.

In Czechoslovakia, material at uranium concentrations up to 200 g per tonne, and radium concentrations of up to 2.22 Bq/g, was approved for road construction until 1991 [Andel1994].


Heap Leaching Piles

In some instances, low grade ores are processed in the heap leaching technology; it is used if the grade is too low for a cost-effective treatment in an uranium mill. The leaching liquid (often sulfuric acid) is pumped to the top of the piles, from where it percolates through the ore and reaches a liner installed under the pile. From there, the uranium bearing liquid is captured and conducted to a processing plant. At the site of Le Cellier (Lozère, France), the leaching process was accelerated, and the uranium recovery was enhanced, by injection of the leaching liquid directly into the piles.

Heap leaching of low grade ores was performed on a large scale at Wismut's Gessental-pile at Ronneburg (7 million tonnes) and in Königstein (2 million tonnes); and at the Hungarian site of Pécs (2-3 million tonnes); and also on a small scale also in Mähring in Bavaria (15,000 tonnes), among others.

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 (FeS2): 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-Situ Leaching

In the case of in-situ leaching, the uranium-bearing ore is not removed from its geological deposit, but a leaching liquid is injected through wells into the ore deposit, and the uranium bearing liquid is pumped from other wells. The leaching liquid contains the leaching agent ammonium carbonate for example or - particularly in Europe - sulfuric acid. This method can only be applied if the uranium deposit is located in porous rock, confined in impermeable rock layers.

In-situ leaching gains importance with decreasing uranium prices. For economic reasons, it is the only technology used in the United States today (for example), the country with the highest cumulative uranium production so far. 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 Czech Republic, in-situ leaching was used on a large scale at Stráz pod Ralskem in North Bohemia. In Bulgaria, in-situ leaching was in use at 8 locations.

The advantages of this technology are:

  • the reduced hazards for the employees from accidents and radiation,
  • the low cost;
  • no need for large uranium mill tailings deposits.

The disadvantages of the in-situ leaching technology are:

  • the risk of spreading of leaching liquid outside of the uranium deposit, involving subsequent groundwater contamination,
  • the unpredictable impact of the leaching liquid on the rock of the deposit,
  • the production of certain amounts of waste slurries and waste water during recovery of the uranium from the liquid,
  • the impossibility of restoring natural groundwater conditions after completion of the leaching operations.

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 hazard to an aquifer that is of importance for the drinking water supply of the region.

Groundwater impact is much larger at the North Bohemian in-situ leaching site of Stráz pod Ralskem: 28.7 million m3 of contaminated liquid is contained in the leaching zone, covering an area of 5.74 km2. This zone contains a total of 1.5 million tonnes of sulphate, 37,500 tonnes of ammonium, and others. In addition to the chemicals needed for the leaching operation (including 3.7 million tonnes of sulfuric acid, among others), 100,000 tonnes of ammonium were injected; they were a waste product resulting from the recovery of uranium from the leaching liquid. Moreover, the contaminated liquid has spread out beyond the leaching zone horizontally and vertically, thus contaminating another area of 28 km2 and a further 235 million m3 of groundwater. To the southwest, the groundwater contamination has already reached the second zone of groundwater protection of the potable water supply of the town of Mimon. In southeastern direction, the contaminated groundwater is still at a distance of 1.2 - 1.5 km from the second zone of groundwater protection of the Dolánky potable water wells, which supply 200 l/s for the city of Liberec [Andel1993]. The migration of the contaminated liquids in a easterly direction towards the Hamr I underground mine is at present intercepted by a hydraulic barrier: decontaminated water is injected into a chain of wells to prevent further migration of the contaminated groundwater.

In Bulgaria, a total of 2.5 million tonnes of sulfuric acid was injected into the ore deposits treated by in-situ leaching [Vapirev1994]. Some in-situ leaching facilities (for example Okop-Tenebo) are located close to drinking water wells. It seems that the environmental impacts of in-situ leaching of uranium have not drawn much attention so far in Bulgaria.


Uranium Milling

The uranium ore produced in open pit and underground mines is processed in uranium mills to recover the uranium. These mills are, in most cases, built near the mines and comprise a mechanical and a chemical treatment. In the first step, the ore is crushed and ground, then it is leached in a hydrometallurgical process. In most cases, sulfuric acid is used as a leaching agent, but carbonate (alkaline) leaching is also used. Since the leaching agent leaches not only uranium from the ore, but also other constituents such as molybdenum, vanadium, selenium, iron, lead, and arsenic, the uranium has to be recovered from the liquid by ion exchange. The final product of the milling process is Yellow Cake, a compound containing uranium in the form of U3O8 and impurities. This final product is packed in casks and shipped to the customers for further processing.

During operation, uranium mills present a hazard, in particular due to the release of radioactive dusts.

During the decommissioning of uranium mills, large amounts of radioactively contaminated metal scrap have to be dealt with and must be disposed of safely. In the case of the decommissioning of the Crossen uranium mill, Wismut plans to dump large amounts of metal scrap in the Helmsdorf uranium mill tailings deposit, to save cost. But, due to chemical reactions taking place between tailings and scrap, gases develop and may deteriorate the safe long-term disposal of the tailings. A further 20,000 tonnes of metal scrap, at a surface contamination of less than 0.5 Bq/cm2, are to be smelted like normal scrap and are to be recycled.


Uranium Mill Tailings

The residues of the milling process, the uranium mill tailings, have the form of a slurry. They are usually pumped to settling ponds for final disposal.

An exception is the Bukhovo mill in Bulgaria, where the slurries were simply dumped in a glen between 1947 and 1958; the finer particles flew into a nearby river. During heavy precipitation, the dumped material was spread over a wider area, contaminating an agricultural area of 120 hectares. Gamma dose rates of up to 1000 µR/h were monitored; this is about hundredfold times the background value. After 1958, the most severely contaminated areas were fenced. But the fences deteriorated later, and the areas were in part reused for agriculture. Radium concentrations of up to 1077 Bq/kg were found in cereals grown on these areas. [Vapirev1994], [Dimtchev1991]

According to the calculating rules prescribed by the radiation protection regulations effective in the Western part of Germany, consumption of these cereals would result in an annual dose of 74 mSv (7400 mrem), while the admissible dose in the German uranium mining area is 1 mSv (100 mrem).

Settling ponds for uranium mill tailings are either installed in existing depressions, or, dams are built for that particular purpose. In France, the tailings are often dumped in former open pit uranium mines.

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. In the Western part of Germany, there exists only one small tailings dam with a content of 170,000 tonnes, at the Ellweiler uranium mill.


Uranium Mill Tailings in Europe
  Solids contents surface
  106 t 106 m3 ha
Germany 170 ?   650 ?
Culmitzsch 90   250
Helmsdorf 50.3   192
Trünzig 19   116
Dänkritz I 5.6   19.5
Dänkritz II 0.8   7
Oberschlema 0.4    
Schlema-Borbachtal 0.3    
Dresden-Gittersee   3 29
Freital   ? ?
Ellweiler 0.17   2.5
Czech Republic   45 ? 607 ?
Mydlovary   18.8 264
Stráz pod Ralskem   14.2 187
Dolní Rozínka   8 110
Príbram   ? 46
Hungary 20   200
Rumania 3.4 1.7 35
Bulgaria 16    
Ukraine ?    
Slovenia ?    
Estonia 4   33
Sweden 1.5 1 25
France 45    
Le Brugeaud 14.2    
Lavaugrasse 5.7    
Le Cellier 5.6    
l'Ecarpière 11.5    
Le Bosc 2.97    
St.Priest-la-Prugne 1.3    
Spain ?    
Portugal ?    
Compiled from a multitude of sources (reference years 1989-1994)
The data from different sources vary considerably in some instances

The amount of tailings produced is virtually equal to the amount of ore processed: at uranium grades of 0.1 % for example, 99.9 % of the input is left over as a waste.

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.

It therefore takes about a million years, for the radioactivity contained in the tailings, and thus the radon releases, to decrease to the level determined by the residual concentration of uranium-238. If, for example, 90 % of the uranium was recovered from ore with a uranium grade of 0.1 %, the radioactivity of the tailings stabilizes at 33 times natural background radiation levels after 1 million years. Due to the 4.5 billion year half-life of uranium-238, practically no further decrease of the radioactivity can be expected.

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. Furthermore, the tailings contain chemicals that were added during the milling process.

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 contaminants are left in a geochemical disequilibrium inside the tailings deposit, causing various processes to take place that present further hazards for the environment, for example:

  • The salts present in the deposit impede the dehydration of the slurries, which would be highly desirable to improve the stability of the deposit, and to lower seepage. On the other hand, these salts cause desiccation of adjacent areas of lower salt concentrations, resulting (for example) in the cracking of cover layers. In dry areas, contaminated salts can migrate to the surface of the deposit, where they are exposed to erosion and spread into the environment.
  • If the ore contains the mineral pyrite (FeS2), then sulfuric acid forms inside the deposit when accessed by precipitation and oxygen. This acid causes a continuous automatic leaching of contaminants.
  • Chemical interactions between the slurries and the liner under the deposit might deteriorate the performance of the liner and thus increase release of contaminants into groundwater.

Due to their properties, the tailings slurries present a very problematic potential of hazards:

The radionuclides contained in the tailings emit gamma radiation. It reaches 20 - 100 times background levels at the surface of the deposit. Gamma radiation decreases rapidly with distance from the deposit. It therefore presents a hazard only for residents living in the immediate neighbourhood of the deposit.

The gas radon-222 escaping from the tailings deposit presents one of the most severe hazards, persisting even after decommissioning of uranium mines, as it causes lung cancer and is continuously produced over longer periods of time. The U.S. Environmental Protection Agency (EPA) estimates the lifetime excess lung cancer risk of residents living nearby a bare tailings pile of 80 hectares at 2 cases per hundred [EPA1983b].

Since radon spreads quickly with the wind, many people receive small additional radiation doses. Although the excess risk for the individual is small, it cannot be neglected due to the large number of people concerned. EPA estimates that the uranium tailings deposits existing in the United States in 1983 would cause 500 lung cancer deaths per century, if no countermeasures were taken [EPA1983].

Tailings deposits are exposed to various kinds of erosion. The longterm safety of the deposit must nevertheless be assured, due to the longevity of the hazards. Precipitation can form erosion gullies; floods can destroy the whole deposit; roots and burrowing animals can intrude into the deposit and spread the material, increase radon exhalation, and make the deposit more susceptible for weathering and erosion. If the surface of the deposit desiccates, the fine sands are blown by the wind over adjacent areas.

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 Estonian uranium mill tailings deposit at Sillamäe is at risk due to its location immediately on the coast of the Baltic Sea. Erosion of the coast line proceeds in several places towards the deposit. In a worst-case scenario, it is anticipated that the whole contents of the deposit might spill into the Baltic Sea.

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. 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 1800 m length and 59 m height, does not even meet 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.

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.

The tailings dam of Zirovski Vrh in Slovenia was severely damaged during a landslide in 1990.

Failures with uranium tailings dams, have occured worldwide, again and again, for example:

  • 1977, Grants, New Mexico, USA: a spill of 50,000 tonnes of slurry and several million liters of contaminated water,
  • 1979, Church Rock, New Mexico, USA: a spill of more than 1000 tonnes of slurry and around 400 million liters of contaminated water,
  • 1984, Key Lake, Saskatchewan, Canada: a spill of more than 100 million liters of contaminated liquid.

U.S. experience shows that dry tailings, with their fine sandy consistency, were often misused for construction of homes or for landfills. In homes built on or from such material, high radiation levels were found from gamma radiation and radon. The U.S. Environmental Protection Agency (EPA) estimates the lifetime excess lung cancer risk of residents of such homes at 4 cases per 100 [EPA1983b]. There is no evidence of comparable efforts for a systematic survey of such misuse of contaminated material in any of the European uranium provinces.

Random samples taken by the independent radiation monitoring organization CRII-RAD in France showed, as an example, radon concentrations up to 1200 Bq/m3 in the kindergarden of Bessines (Haute Vienne) [CRII-RAD1994]. They were caused from use of contaminated fill in the floor of the building. This level corresponds approximately to that allowed for uranium miners for occupational exposure. The standards for radon in homes are, in many countries, around 200 Bq/m3.

Seepage from the tailings deposit contaminates surface and ground waters. Residents are endangered from radium-226 and other hazardous substances such as arsenic in their drinking water and in fish caught in the area. The seepage problem gains importance with acid tailings, since most of the radionuclides involved are more mobile under acidic conditions. In pyritic tailings, acidic conditions establish automatically by sulfuric acid production from oxidation of pyrite, enhancing the spreading of contaminants with seepage. Under favourable geochemical conditions, the contaminants are trapped in the soil beneath the deposit, or their migration is at least slowed down. But often, this retention effect decreases with time. If the bed rock consists of fractured rock, the spread of the contaminants is not retarded at all.

The behaviour of seepage in natural soils depends on complicated hydrogeological conditions; its behaviour can only be predicted on the basis of detailed monitoring data and computer modelling. The seepage release presents one of the two major hazards resulting from uranium mill tailings (the other being radon exhalation).

Total seepage from the Helmsdorf tailings deposit is estimated at 600,000 m3 per year; only about the half of this amount is detained and temporarily pumped back to the deposit, until a water treatment plant is operational. This seepage has a high contaminant load, expressed as multiples of drinking water standards, for example: sulphate 24x, arsenic 253x, uranium 46x. On the one hand, the contamination invades the creeks around the deposit, where concentrations decrease rapidly with distance. On the other hand, seepage causes contamination of groundwater. The values found here are lower, but they hardly decrease with distance. [Wismut1992c]

The total seepage releases from the uranium mill deposit at the Stráz pod Ralskem mill in North Bohemia have amounted up to 4 million m3 of contaminated liquids since 1979. Sooner or later, they could reach the river Ploucnice at a distance of only 750 m, or the deeper groundwater that represents the largest drinking water reserve in North Bohemia. At the second pond of the deposit, which became operational in 1992, a groundwater contamination front was observed, proceeding at a speed of 0.4 m per day away from the deposit. [Hudecek1993]

Groundwater also is contaminated from seepage around the uranium mill tailings deposits of the Pécs uranium mill in Hungary. About 1 - 2 km westward from the deposit, a number of wells are operated, producing about half of the potable water demand of the city of Pécs. The contaminated groundwater migrates at a speed of 30 - 50 m per year towards the drinking water wells. Due to lack of funds, further seepage cannot be intercepted, not to mention restoration of the already contaminated groundwater.

In France, radium concentrations of more than 25 Bq/g were found in the sediments of creeks around the Bellezane (Haute Vienne) uranium mill tailings deposit; this corresponds to the radium concentrations found in the tailings themselves [CRII-RAD1994].

The tailings deposit of the Estonian uranium mill at Sillamäe is located immediately on the coast of the Baltic Sea. Uranium concentrations of up to 230 times background levels were found in the sea water (190 g/l). The contamination could be monitored up to a distance of 300 m from the coast. [Ehdwall1993], [Putnik1994]

The contaminants released from uranium mill tailings can contribute through various pathways to the doses received by humans. Some of these pathways have a direct impact, while others are effective through the food chain. Two direct pathways have been identified as the major contributors to the doses received: the inhalation of released radon and dust, and the consumption of water, contaminated by seepage.

Dumping of Extraneous Wastes

The lack of disposal sites for toxic and nuclear waste lead to proposals to dump these hazardous wastes in uranium waste rock piles, in uranium mill tailings deposits, or in former uranium mines:

  • 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 m3 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.
  • Low level radioactive waste from Rhône-Poulenc's La Rochelle facility is to be dumped on the tailings of the shut down l'Ecarpière (Loire Atlantique) uranium mill in France. The La Rochelle facility produces rare earth elements from ores imported from Australia.

If the mixing of uranium mill tailings with other wastes is approved, the reclamation of these deposits becomes even more difficult, if not completely impossible, since the most suitable method available is always for a single contaminant only.

  • 176,150 radioactively contaminated casks, alleged empty, were dumped in the pit of the former open-pit uranium mine at Margnac near Limoges in France.
  • Investigations are underway in Hungary to find out, whether a deposit for high-level nuclear waste can be installed 1000 m below ground beneath the Pécs uranium mine, which is scheduled for shut down [NF 2 January 1995].

But, in most cases, decommissioned uranium mines have very poor properties of contaminant retention; detailed investigations must be performed at the site by independent experts, before such disposal can be considered.

  • 265,000 tonnes of depleted uranium is to be stored at the site of the shut down uranium mill at Bessines near Limoges in France. The depleted uranium is a waste produced by the EURODIF uranium enrichment plant located at Tricastin in the Rhône valley.

During the active life of uranium mines, the major hazards result from release of radon and dust by mine ventilation, and from mine water releases.

After shut down of the mines, the major hazards are posed by radon releases and seepage from waste rock piles and tailings deposits.

In-situ leaching presents a severe hazard to groundwater reserves.

The contamination was spread widely by use of contaminated material for construction purposes.

Heap leaching piles, uranium mill tailings deposits, and in-situ leaching facilities are the most problematic legacy of uranium mining.

All problems resulting from uranium mining are of a real long-term nature.

Mixing of different kinds of waste often makes problems even worse.

Related images:
Uranium Production
Uranium Concentrations in Rock
Elevated Radon Levels
Heap leaching of uranium ore
In Situ Leaching of Uranium
The uranium-238 decay chain
Radioactivity in tailings
Uranium Mill Tailings Hazards
Typical construction of a tailings dam
Major environmental transport pathways from uranium mill tailings to man
Related Photo's
Open pit mine Le Bosc near Lodè (Hérault, France)
Landscape of piles at Paitzdorf, Ronneburg (Thuringia), May 1990
Waste rock piles at Schlema (Saxony)
Uranium mill tailings deposit in the former bellezane open pit mine near Bessines-sur-Gartempe, January 1992
The two partial ponds of the Culmitzsch uranium mill tailings deposit
Main dam of the Helmsdorf uranium mill tailings deposit