Characterization and Remediation Planning for Two Uranium Tailings Facilities at a Uranium Production Legacy Site in Ukraine (PChP)
Korychenskyi K. O., Voitsekhovych O. V., Lavrova T. V. Ukrainian Hydrometeorological Institute
IAEA Technical Meeting of the Uranium Mining and Remediation Exchange Group 7–9 October 2019 Chemnitz, Germany
1 Overview of the problem
2 Overview of the problem
1 km
µSv/h
Soils within Zone of contamination Zone of concentrate refining Background with ore material and temporary ore shops (purification uranium concentrates storage 230 226 soil from Th and Ra
3 Overview of the problem
Surface water contamination
The maximum allowable content of uranium isotopes in drinking water (NRSU-97)
Control level of total alpha-activity (State sanitary regulations and standards 2.2.4-171-10) 4 SW-2 SW-3 SW-4 Dnieper river
Site characterisation
Konoplyanka model river Trytuznyi Open pit
Zapad PChP noe Centralny territory Tailing Yar s Tailings Kamianske city (Inhabited area)
5 Uranium-rich iron ore from Polymetallic ores of Schneierberg ore field Uranium-phosphoric ores Pervomaiske (1949-1968y) and (Germany 1951-1953), ore concentrates from Melovoe deposit Zhovtorichenske (1949 – 1990y) from Jáchymov deposit (CZ 1951-1964) and (Kazakhstan 1960-1987) deposits (Dnipropetrovsk district) Bihor, Banat (HU 1951-1963)
Blast furnace slag Ore
Ore storage (Base C)
Shop #1 Slag storage, milling, and pulp preparation Shop #4 Ore storage, milling, and pulp preparation (Building 1, 2 (Building 1A and 1B) and 3)
Until 1953 – slag Until from 1960 From 1953 – ore 1960 to 1987
Shop #2 Hydrometallurgical Shop #22 Hydrometallurgical Shop #5 Hydrometallurgical processing processing (1949-1960) (bld. 102) processing (1952-1987) (bld. 2) (1951-1990) (building 6)
Precipitation-filtration Purification from radium, scheme: digestion, Sorption scheme: extraction, thorium and REE, uranium precipitation, filtering, sorption: from 1960 – cationite SG-1, sorption (building 102, 103, washing, drying from 1976 – “solid extractant”, 104) (1949-1960) desorption, uranium concentrate production
40% concentrate of 95% concentrate of
uranyl-carbonate UO2CO3 uranium oxide U3O8 (yellow cake)
“Central Yar” “Zapadnoe” “Yugo-vostochnoe” “Dniprovske” “Sukhachivske” tailings tailings tailings tailings tailings (1st section:1968 -1983, (1949 -1954) (1951 -1954) (1956 -1980) (1954 -1968) 2nd section; form 1983) 6 Observation wells for groundwater quality
7 Materials for analysis
Tailings material Drilling campaigns in 2009 and 2012 Available data for: •Dose rate with depth of borehole •Moisture content, density, porosity and particle size of material •Pore water (only 2012) •Physical-chemical parameters profiles, measured in field (Eh, pH)
Groundwater Groundwater monitoring data since 2005 Available data for: •Radionuclide composition •Chemical composition •Physical-chemical parameters (Eh, pH, TDS, EC) •Water level and hydrological parameters
8 Analytical work
Analytical work was carried out in UHMI and JSI radiochemical laboratories. Following methods were used: •X-ray diffraction analysis of the mineral matter of tailings dumps for the determination of mineralogical composition. •Methods of sequential extraction for determination of mobile forms of radionuclides (BCR) •Batch-type measurement for contaminant desorption •Radiochemical methods for the isolation of uranium, radium and thorium for water and mineral matter (TEVA+UTEVA, microprecipitation). •Methods of low-background semiconductor γ- and α-spectrometry. •Field and laboratory methods for determining the basic physicochemical parameters (pH, Eh, EC, TDS)
9 Central Yar Tailings Facility
• Operated from 1949 to 1954 • Placed in natural ravine • low pH (up to 2.5-4) within the tailings material • No special engineering protective cover • Contaminated topsoil • Area is planted with foliar trees. Specific activities of selected radionuclides in different compartments of CY tailings (in [Bq/g])
Mass - 0.22 million t of radioactive tailings; Volume – 0.13bln. m3 Total activity - 104 TBq (1.04*14E14 Bq);
10 Central Yar Tailings Facility
12-2c
12-1c
11 Zapadnoe Tailings Facility
• In operation 1950 to 1954 • Mass - 0.77 million t of radioactive tailings 3 • Volume – 0.23 bln. m • pH 8 – 9 (in tailings material) • Special engineering protective cover but not sufficient and ruined • Topsoil is contaminated in significant levels
Specific activities of selected radionuclides in different compartments of CY tailings (in [Bq/g])
12 Zapadnoe Tailings Facility pH
12-ZP
13 Mineralogical composition
Central
Yar
Tailings
Zapadnoe
Tailings
14 Central Yar
The spatial distribution of pH in the tailings body Uranium in exchangeable water soluble form
12-1CY - 12m
15 Characteristics of pore solutions Zapadnoe Tailings
The spatial distribution of pH in the tailings body Uranium in exchangeable water soluble form
12-1ZP - 4.5m
16 Characteristics of pore solutions Distribution coefficient (Kd) of U, Th and Ra in tailings
Depth, m Kd, L/kg Tailings dump from to U-238 Th-230 Ra-226
0 5 157 3716 18484 Zapadnoe 5 10 141 8562 27278 10 15 38 295 3317 0 5 427 238 43798 Central Yar 5 10 2387 5660 53117 10 15 886 14867 45806 Eh–pH diagrams for the U–/ Th–/ Ra–,
SO4-HCO3-H2O systems at 25 °C Central Yar and Zapadnoe
tailings
18 Speciation of uranium and radium in underground waters within the Central Yar tailings
19 Speciation of uranium and radium in underground waters within the Zapadnoe tailings • Alkaline conditions promote the migration of uranium in the composition of carbonate complex compounds. • The higher the content of hydrocarbonate ion in the composition of groundwater, the more stable the complex compounds are. • The conditions created in the Zapadnoe tailings pond do not prevent the migration of uranium and radium from the material of the tailing dump.
20 MDL Chemical Potential of reuse Concentration+/-unc (mg/kg) element (mg/k of residual g) CY12-2 CY12-1 ZP12-1 ZP12-1 material (14-15m) (14-15m) (6.5-7m) (10-10.5m) Pb 0,03 3,59 ± 0,32 4,19 ± 0,38 21,59 ± 1,94 949,0 ± 85,4 Be 0,05 2,06 ± 0,18 2,05 ± 0,18 6,73 ± 0,61 11,63 ± 1,05 V 0,12 186,8 ± 16,8 209,4 ± 18,8 514,3 ± 46,3 178,9 ± 16,1 Cr 0,05 23,74 ± 2,14 23,39 ± 2,10 79,87 ± 7,19 84,62 ± 7,62 0,015 ± Tl 0,005 0,012 ± 0,001 0,12 ± 0,01 2,03 ± 0,18 0,001 0,021 ± Bi 0,003 0,016 ± 0,001 0,35 ± 0,03 11,69 ± 1,05 0,002 U 0,19 460,8 ± 41,5 726,3 ± 65,4 88,14 ± 7,93 209,6 ± 18,9 As 0,17 CY12-2 CY12-1 ZP12-1 ZP12-1 Concentration of REE (14-15m) (14-15m) (6.5-7m) (10-10.5m) (mg/kg) 21 7 14 21 26 Processing data for risk assessment modelling Groundwater transport and aquifer mixing calculations in NORMALYSA 22 Conclusions • This study aimed to understand the geochemical situation within the tailings, to evaluate the impact of these tailings on the quality of ground water in surrounding area and assess impact on the environment. • The tailings, as objects of uranium production legacy, defined as the main source of ground and surface water contamination on the territory of Prydniprovskyi Chemical Plant. • The geochemical conditions that formed in the tailings "Zapadnoe" and "Central Yar" contribute to the leaching of uranium into the environment. Such favorable conditions for migration are facilitated by: • Infiltration of atmospheric precipitation through the surface covering over the body of the tailings and the absence of an engineering barrier in its bottom part. • The presence of gypsum in the mineralogical composition of the tail material and the free access of infiltration waters contribute to an increase in the sulfate ion content in the pore and groundwater. • Low levels of pH of the environment in the Central Yar tailings. • The access of oxygen, which enters the tailing dump body with atmospheric infiltration waters, leads to an increase of the oxidation potential (Eh). 23