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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings
Case Studies
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings
10
Lands Damaged as a Result of Uranium Ore Mining Operations in the Russian Federation
V. P. Karamushka and V. V. Ostroborodov, All-Russian Research, Design, and Surveying Institute of Industrial Technology (VNIPIPT)
The operations of uranium ore mining and processing enterprises inevitably contaminate the environment with solid, liquid, and gaseous wastes, which are the most voluminous within the nuclear fuel cycle industries and, despite their relatively low activity level, significantly contribute to the radiation hazard facing the population.
Table 10-1 provides data on radioactive contamination of the main sectors of the environment at uranium ore mining enterprises.
Beginning from the time large-scale uranium ore geological prospecting and mining began in the USSR in 1945, nine industrial complexes were built on the territories of six Soviet republics. The complexes now operate as production facilities in the Newly Independent States. The total land area damaged by their production activities is 80,500 ha, and about 220,000 ha may be affected eventually by radioactive products transferred by air streams, surface water flows, and so forth.
At this time in the Russian Federation, both currently operating facilities and worked-out deposits need to be put in safe condition from the standpoint of radiation risk to the population.
Following is a list of decommissioned mining enterprises of the former Russian Ministry of Atomic Energy (Minatom), as well as geological prospecting and experimental production facilities where operations have been discontinued:
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TABLE 10-1 Characterization of Radioactive Contamination of the Main Sectors of the Environment
Sector
Radiation Hazard Factors
Unit of Measurement
Background Values
Maximum Permissible Concentrations Above Natural Background
Actual Recorded Value Range
Notes
Average
Range
Air
Equivalent equilibrium concentration of radon daughter products
Bq/m3
1.8
0.1-10.0
37a
185-260
At distance of 100-150 m from source
Total ά-activity of long-lived radionuclides of the uranium natural radioactive decay family
mBq/m3
0.01
0.001-10
12.0
4-40
At distance of 100-150 m from source
Water
Ra-226 and daughter products
Bq/m3
37
1.11-111
111b
300-500
During geological prospecting and preparatory mining operations
3,700-5,500
During cleanup operations
10,000-50,000
In crude mine waters
10,000-80,000
In liquid phase of hydrometallurgical plant (HMP) tailings
Soils
Total ά-activity of long-lived radionuclides of the uranium natural radioactive decay family
Bq/kg
370
90-700
600-1,200
1,000-7,400
In sanitary protective zone of operating enterprises
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Solid Waste
Refuse heaps
ά-activity
Bq/kg
240
150-10,000
600-1,200
1,000-12,900
Refuse heaps, waste piles, radiometric enrichment and heap-leaching tails
γ-activity
µR/hr
12
10-60
20
20-200
HMP tailings
Radon exhalation from surface
Bq/m2/s
0.016
0.004-0.053
1.0c
1.7-30.0
On dry beaches of tailing dumps
Solid phase ά-activity
Bq/kg
210
370-700
600-1,200
1,100-27,300
Solid phase γ-activity
µR/hr
12
10-60
20
100-1,400
a = outdoors, for dwellings: 200 Bq/m3
b = water reservoirs, for waste waters assuming their dilution: 185 Bq/m3
c = USSR standard, by ICRP data: 0.74 Bq/m2/s
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Lermontov Industrial Association Almaz
Novotroitsk Thorium Ore Mining Administration in the city of Balei, Chita Oblast, and an open-cast mine near Ozernoye settlement
Stepnoye Ore Mining Administration in the Republic of Kalmykia
Numerous experimental production sites where geological prospecting parties operated, the biggest among them being the Aldan deposit in the Republic of Sakha (Yakutia)
The Lermontov Industrial Association Almaz is most significant from the standpoint of mine reclamation activities. We shall now consider it in more detail, as the situation there demands immediate action. The enterprise is located in the Mineralnye Vody spa area in the Caucasus, close to the city of Lermontov, Stavropol Krai (130 km southeast of the city of Stavropol).
The Almaz site effort is a model pilot project for the development and implementation of a comprehensive program for remediation of land and facilities left behind after uranium ore mining and processing operations were discontinued at similar enterprises in the Russian Federation. The Almaz uranium ore mining and processing enterprise was established in 1950 on the basis of a local mining and chemical ore mining administration. Its underground mines Beshtau, Byk, Shargadin, and Stepnoye were the first to be set in operation. In Lermontov in 1954, a hydrometallurgical plant (HMP) began processing uranium ore with triuranium octaoxide as its final product. The plant also produced fertilizers, scandium oxide, and some other by-products. To remove radioactive waste from the plant, tailings dumps were created a few kilometers away.
Mine No. 1 ceased operation in 1975, and decommissioning work continued to be performed there until 1994. An electromechanical plant was built on the former mine site. In 1989, Mine No. 2 was also put out of operation. Its mining equipment was dismantled in 1991 and reclamation of the mine’s galleries was subsequently carried out. In 1991 the HMP was shut down, its production equipment was dismantled, and the main building of its uranium processing plant was decontaminated. The radioactive waste, including contaminated equipment, was removed to the tailings dump.
After all uranium ore mining work ceased and the equipment was dismantled, the natural groundwater level began to be gradually restored. Filtration of significant volumes of groundwater through highly mineralized rocks, which had dried as a result of the ore mining operations, now creates a real hazard as it contaminates the water with radionuclides and other chemical components. There is a rather high probability that surface water (the Kuma River system) and sources of fresh and mineralized groundwater in the Mineralnye Vody spa area in the Caucasus will be contaminated.
The sites of mines No. 1 and 2 and the HMP tailings dump pose direct hazards to the local population and environmental safety. Contamination is caused by uranium, its daughter products, and other nonradioactive substances pen-
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etrating into the system of surface water and groundwater, as well as by radon emanation.
At present, the upper sections of the HMP tailings dump are covered with a layer of apatite-processing waste (neutralized phosphogypsum), which reduces the passage of radon. The dump’s lower section is almost completely covered with surface water. The results of a preliminary assessment indicate that radon emanation from the HMP tailings dump is rated first on the list of radiation impact factors, with the tailings pile from Mine No. 2 taking second place. The high level of radiation impact is caused by the contamination of the hydrogeologic system as a result of radionuclides and other chemical substances leaching from the uranium ore.
The underground mines are accessible. The total amount of radioactive waste there is about 22 million metric tons with about 49,000 Ci of total activity. Mine conservation and reclamation works have been performed occasionally.
According to radiation-monitoring data, the gamma-radiation background level in the tailings dump area is within the range of 200-2,000 µR per hour (in some places up to 4,000 µR per hour). The average soil alpha-activity level does not exceed 2,400 Bq/kg in the tailings dump area and 800 Bq/kg at the HMP site.
Taking into account the particular importance of the Mineralnye Vody spa area of the Caucasus (in accordance with the Russian president’s Decree No. 309 of March 27, 1992, entitled “On a specially secured ecological and resort region of the Russian Federation”) and with the goal of effectively applying European experience in uranium waste management in the European Union (EU) and East European states, the Russian government decided to ask the EU to provide technical assistance in developing an adequate program for the former uranium ore mining facilities in the Lermontov area for management and reclamation.
A concept has now been developed for uranium ore mine reclamation at the former state-owned enterprise Almaz in Lermontov. This plan was prepared within the framework of an EU program by a consortium including Wismut GmbH (Chemnitz), Wisutek GmbH (Chemnitz), C&E GmbH (Chemnitz), G.E.O.S. GmbH (Freiburg), Atomredmetzoloto Open Joint-Stock Company (Moscow), VNIPIPT (Moscow), and the Hydrometallurgical Plant (Lermontov). The concept (EUROPAID/116483/C/SV/RU) is the last step preceding creation of an ecologically safe zone on the territory of the former uranium ore mining enterprise Almaz in the Mineralnye Vody region.
The main results attained under this program are as follows:
A database has been created using up-to-date computer technology.
The need for carrying out reclamation works has been established and the necessary protection limits have been assigned.
Remediation options have been determined with raw economic surveys for the following complex objects:
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Beshtau mine
Byk mine
Hydrometallurgical plant
HMP tailings dump
Social aspects of the resort region’s development, as well as concerns of the Lermontov city residents and the local administration, were also taken into consideration.
In accordance with the plan, a guaranteed supply of radon water to the resorts of Pyatigorsk is foreseen, and radiation and environmental safety is to be ensured for both the local population and the recreational areas near Lermontov. The next step is practical implementation of the plan, including elaboration of working projects and their realization in concrete form. A project implementation schedule is currently being developed. To create plans for a working project for reclamation of the HMP tailings dump, a significant amount of additional data on the physical and mechanical characteristics of the deposits will be needed.
In all enterprises of the former USSR Ministry of Medium Machine-Building (Minatom was its successor), there were special service units engaged in environmental (radiation inclusive) and geochemical monitoring of water conditions. There was a special research laboratory at VNIPIPT engaged in developing technologies for tailings dumps and monitoring their conditions. As a result of the activities at VNIPIPT, which had planned all of the uranium mining enterprises both in the USSR and in Eastern Europe, the institute created an unprecedented database on such capital-intensive (as far as restoration efforts are concerned) objects as tailings dumps, the world’s largest database of its kind.
The research carried out made it possible to develop methods for underground water contamination forecasting. The methods were used in practice and showed a good convergence of the forecasts produced with actual operational monitoring data.
In the period after a facility ceases operation, the main factor determining the reliability of technical solutions for tailings dump reclamation (conservation) is the knowledge of physical and mechanical characteristics of tailings sediments both to date and for a long time to come. Such data are partly available at VNIPIPT, as a result of studies that have been carried out.
Systematic analysis of data from operational observations indicates the need for diversity in dealing with sites located in the arid zone and areas where the climate is continental or extremely continental.
The available database on sites in the Commonwealth of Independent States (CIS) makes it possible to create an atlas of physical and mechanical characteristics of tailing sediment materials and to use simplified testing procedures for the materials before performing reclamation works. Such work is already being carried out for the Central Asian region. The suggested approach makes it possible to avoid rather expensive and dangerous operations at the tailings dumps and to save on expenses for studies by several thousands of dollars.
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The next step is the development of procedures for evaluating the status of worked-out tailings dumps for various climate zones and highlands. For that purpose, we have proposed some procedures for evaluating the radioecological safety of tailings dumps as well as a procedure for assessing the environmental efficiency of reclamation works. The development of a package of standard technologies for the CIS countries with necessary amendments to the regulatory documents should be the final stage of the efforts.
As the data from observations made at both operating and worked-out tailings dumps since 1969 show, the particle size distribution of the tailings, ore processing technology, and climate conditions are the determining factors in the process of forming strength properties.
At the sites under consideration, the following uranium extraction processes were used:
Acidic
Sodium carbonate treatment
Acidic leaching from burnable coal zone
As to the effect of climate conditions, it was established that each of the climate zones requires an individual approach, and in each of them, specific reclamation technologies should be used. This can be shown by the example of sites located in arid zones. According to the 1997 United Nations Educational, Scientific, and Cultural Organization classification, arid territories on the earth are subdivided into four bioclimate zones, each characterized by its aridity index value:
Extra-arid zone: annual rainfall less than 100 mm
Arid zone: annual rainfall within the range of 100-200 mm, aridity index <0.03
Semiarid zone: annual rainfall within the range of 200-400 mm, aridity index 0.2-0.5
Zone of insufficient moistening: annual rainfall within the range of 400-800 mm, aridity index 0.5-0.75
By that classification, most of the uranium ore mining enterprises of the former USSR are situated in the arid and semiarid zones and in the zone of insufficient moistening. Thus, all such facilities located in Kyrgyzstan, Uzbekistan, Tajikistan, and, partly, Kazakhstan fall into these categories. There are such enterprises in Russia as well: the Stepnoye Ore Mining Administration in the Republic of Kalmykia and the Lermontov Industrial Association Almaz.
For the tailings dumps, the main distinction between the arid zone and the areas with continental and extremely continental climate is linked with humidity conditions in the mass of tailing sediments.
If the climate factor is not taken into account, a water lens can form within
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the body of the tailings dump. According to studies that have been carried out, the lens formation mechanism to a certain degree depends on desert groundwater recharge conditions through the suspended water zone. As our studies show, a water-saturated zone can form over a very long period in the tailings mass. The zone is isolated from the surface by a mulch layer, preventing evaporative processes.
Available factual data on the dependence of tailing sediment humidity on particle size, density, and stabilization time make it possible to develop a method for predicting humidity conditions over the long term. We are currently engaged in such work. On the basis of results of the forecasting efforts, technical solutions should be taken to ensure that saturated surface egress to the downstream side of the filled-up tailings dam is impossible.
In our practice, one solution to this problem is to make an absorbing well by means of horizontal drilling. The water-saturated zone is discharged through the well. The place for drilling is determined on the basis of forecasting calculations, and the well is monitored by penetration studies.
Results of the planned efforts to create an atlas of tailing sediment charts and geochemical landscapes for the CIS countries may also be used for East European sites as well as for other industries where environmental contamination with natural radionuclides occurs.
Taking into account the large scale of the efforts and their significance, we believe that the work can be an object of international cooperation within the framework of European Commission and International Science and Technology Center programs.
