-ii*. f I SSI-rapport 93-06 !".••••' •'• Shit t 'us Box 6020- OS -~'.'*9 ssi 10-; 01 STOCKHOLM Soha Hans Ehdwall et al Studies on the Waste Depository of the Sillamäe Plant -Sur.. fctftBStatens strålskyddsinstitut Nummer / Number: 1993-06 Swedish Radiation Protection Institute ISSN: 0282-4434 Titelblad / Title page Datum / Date of issue: 1993-03-15 Författare / Author: Hans Ehdwall, Björn Sundblad, Vladimir Nosov, Henno Putnik, Raimo Mustonen, Laina Salonen, Erkki Illus, Henning Qvale Avdelning / Division: Dokumentets titel / Title of the document: Studies on the Waste Depository of the Sillamäe Plant State of the art report from the project group Sammanfattning / Abstract: The studies on the waste material in the Sillamäe depository indicate that the wall material of the depository is typical mill tailing from chemical enrichment of uranium ore. The results from the sea sampling show that the impact from the depository on the marine environment is obvious close to the shore-line. However, the concentrations of radioactive elements decrease very rapidly as the distance from the shore increases. Nyckelord (valda av författaren) / Key words (chosen by the author): Sillamäe, uranium waste, waste deposit, thorium, loparite, environmental radiation Antal sidor / Number of pages: 10 THE SILLAMÄE PROJECT 93-03-15 STUDIES ON THE WASTE DEPOSITORY OF THE SILLAMÄE PLANT State of the art report from the project group SUMMARY The studies on the waste material in the Sillamäe depository indicate that the wall material of the depository is typical mill tailing from chemical enrichment of uranium ore. The results from the sea sampling show that the impact from the depository on the marine environment is obvious close to the shore-line. However, the concentrations of radioactive elements decrease very rapidly as the distance from the shore increases. The farthest distance where elevated radionuclide concentrations were observed was 300 meters from the shore-line. The results on the ground water used as a tap water in Sillamäe indicate that the waste depository ooes not contaminate the local ground waters. BACKGROUN', Until 1970, only uranium ore and alum- shale were processed at the plant. Sillamäe is a .'I town, some 185 km Elemental uranium was enriched with east of Tallin . ,:i onia. It has about 20 a chemical treatment of the crushed COO inhabita rt. ; nd has been develo- ore by: ped around £ Sillamäe Metallurgy -leaching Uranium from groun- Plant, today 1 State join-stock com- ded ore using sulphuric acid pany callec rS Silmet. Unti! recently, -solid liquid separation and the plant t: nged to and was mana- washing ged by the 3SR Ministry of Medium- -solvent extraction of Uranium Scale Engei -;ering and it's production was uraniun, ,or military and civil use. After the recovering of Uranium the leached liquid was neutriized by the The Sillamst Plant was built in 1948 addition of ammonia and oil-shale ash as a top se ;'et facility, originally for from a local thermal power plant and processing aljm-shale (about 300 ppm discharged together with the the solid of U) from Estonia. Later uranium ore residues of the Uranium ore into tai- from eastern Europe (up to 10 000 lings. Between 1948 and 1959, waste ppm) was processed. As a total, 4 013 from the Uranium processing was 000 tons of uranium ore were pro- transported to the first marine terrace cessed at the plant. Most of the ore of Päite cape and stored at the sur- was brought from Czechoslovakia (2.2 face. In 1959 , a waste depository was million tons) and from Hungarv (1.2 established. The site was surrounded million tons). Minor amounts of ura- by a dike made from local ground and nium ore were brought from Poland, production residues whir i permit drai- Romania, Bulgaria and DDR. nage. The depot has been reconstructed a couple of times in the last decades and in 1969-70 it was ex- ' f panded to it's present size. Waste 'K- material from whithin the depot was 4 million tons of uranium mining resi- then used for the construction 01 the duals, walls of the impoundment. 1.5 million tons of oil-shale ash, and 0.2 million tons of calcium fluoride Today, the depot is an oval retention (CaF2), including impoundment with an overall area of about 330 000 m2, the top of the dam 1.2 thousand tons of uranium, being about 25 meters above sea le- 0.8 thousand tons of thorium, and vel. About 50% of it's area is covered 4.4 x 1015 Bq (1.2 x 105Ci) of radioac- by a sedimentary pond containing tive elements (decay products of ura- about 150-200 000 m3 of waste water nium and thorium) of which about 3 x with a depth of 0-3 meters. The bottom 104 Bq (7000 Ci) is radium. of the depository concists of a perme- able sandy-gravel-shingle ground THE PROJECT (thickness varying from 1 to 8 meters) lying on a 2 -10 meter thick layer of in June 1992, an international project watertight Cambrium clay. was established. The tasks of the group were defined as: In the beginning of the 1970s the plant switched to processing of loparite - a 1. to estimate the amounts of ra- mineral from the Kola Peninsula rich of dioactive and chemical pollutants in Niobium, Tantalium and other rare the depository, earth metals. In addition loparite also 2. to estimate the amounts of ra- contains Uranium (about 0.03%) and dioactive and chemical pollutants lea- in paticular Thorium (0.6%). Since king from the depository to the Gulf of 1977, no Uranium ore has been pro- Finland, cessed, the depot has been used for 3. to estimate the environmental the disposal of oil-shale ash and was- impact of the Sillamäe waste pond to tes from loparite processing (1977-89). the Gulf of Finland, to the Sillamäe The annual volume of disposal of lo- town, and to the ground water in parite waste has been about 20 000 Sillamäe area, and tons per year, and oil-shale ash has 4. to make proposals for getting been disposed over different areas the waste depository to an acceptable during the last years. Today the plant condition. is operating only about 15-20% of it's production capacity due to shortage of Two alternatives for environmental im- raw material and chemicals for the pact to the Gulf of Finland and the Bal- process. tic Sea are to be studied. The first is if the depository remains as it is and the It can be concluded that the Sillamäe second if, of some reason, ali the waste depot has been formed of waste contents in the depository, in short ti- with various chemical and physical me period, will enter the Gulf of Fin- properties accumulated over the years land. due to various technological processes used for production. The first meeting of the group was held in Sillamäe in June 15-17. The mee- An estimation of the substances dis- ting resulted in a plan for sampling that posed in the aam, given by the plant, should be performed during autum indicates the following: 1992. The second meeting was held in ' f Helsinki in November 23-25, after most In order to estimate the impact of air- of the collected samples were ana- borne radon originating from the pond, lyzed. The members of the project passive radon monitors were set out at group and other participants in the 10 different locations. The exposure project are listed in the appendix. time is expected to be around 5-7 months. SAMPLING RESULTS OF THE MEASUREMENTS In September 14-17, sampling was done at Sillamäe. Soil samples from Solid samples from the depository the pond wall were taken at 25 diffe- rent places. Preparation for the sam- Twentyfive samples of the solid waste pling was done by the Silmet Plant in were collected from small pits dug in advance so that the pits were dug to a the wall of the depository. During depth of about half a meter into the sampling, dose rates were measured wall. At each place soil samples were inside the pits. Two samples were taken for measurement of radioactive collected outside the wall of the de- and chemical substances. The exter- pository and these samples represent nal gamma radiation was also measu- the older waste deposited in the be- red at each pit. ginning of the industrial operation at Sillamäe. Two samples were taken Water samples were taken from nine from the top of the depository to repre- different drilled well holes around the sent the waste of the present produc- depository. The samples are ground tion of the plant. Places for different water samples and they are assumed samples are shown in Figure 1. to be representative for liquid effluents leaving the disposal area to the Gulf of Concentrations of 238U and 226Ra in the Finland. Water samples from a little wall samples showed that the wall pool between the depository and the material of the depository is typical Gulf of Finland, from the top of the waste of chemical enrichment of ura- pond and from a spring outside the nium ore. The uranium concentrations disposal site were also taken as well varied between 2000 and 9000 Bq/kg as samples of domestic tap water. The dry weight, and radium concentrations K K spring was choosen after considering between 1000 and 73 000 Bq/kg. the direction of ground water flow and These uranium and radium concentra- is used as a reference. Tap water used tions are roughly 100 to 1000 times in Sillamäe originates from deep drilled higher than typical concentrations in wells (depths varying between 125 and soil.