7. PLUTONIUM PRODUCTION AND RADIOCHEMICAL REPROCESSING OF SPENT NUCLEAR FUEL

7.1. General information

In the former USSR the production of weapon grade plutonium was concentrated at the three great enterprises:

• the Industrial Association (IA) "Mayak" in Ozersk, Chelyabinsk Region;
• the Siberian Chemical Combine (SCC) in Seversk, Tomsk Region;
• the Mining and Chemical Combine (MCC) in Zheleznogorsk, Krasnoyarsk Region

All the enterprises are located at the territory of Russian Federation.

The process of plutonium extraction from irradiated uranium includes, firstly, separation of the two metals and, secondly, their purification from fission products. Metallic plutonium articles are the final product of the plutonium line of the process.

The nuclear materials production is accompanied by generation of radioactive wastes, which undergo suitable processing and then are sent for storage.

7.2. Characterization of accumulated radioactive wastes

Irradiated materials reprocessing, like any chemical production works, is connected with generation and disposal of waste. Radioactive wastes (RW) are differentiated over their aggregate state, specific (volume) activity level and origin.

By their aggregate state the RW are divided into liquid, solid and gaseous wastes. To the category of liquid wastes, besides waste process solutions, various suspensions and sludges are attributed. The solid RW include: metals, concrete, wood, organic films, working clothes, etc. The gaseous wastes may be provisionally subdivided into two groups: gases, containing induced (in nuclear reactors) activity, and gases, evolving as a result of irradiated uranium reprocessing and of further chemical and metallurgical treatment of radioactive materials.

At present at the enterprises on reprocessing of irradiated uranium high, medium and low level radioactive wastes (RW) are kept.

By their origin the RW may be subdivided into process wastes (the reactor wastes and the wastes of radiochemical, chemical & metallurgical, UF₆ production, uranium isotopic enrichment and other production works) and non-process ones (the wastes of sanitary treatment points, special laundries, research laboratories and other auxiliary works).

By their total activity the process wastes are significantly predominating. The most part (practically more, than 99 % ) of fission products is concentrated in liquid RW, as far as aqueous processes were and are now used for the industrial reprocessing of irradiated uranium.

7.2.1. The IA "Mayak"

The Industrial Association is situated on the area of 160 sq.km. Dwelling blocks are arranged in the North-Western and South-Western parts of the territory. The main production site is located in the Central and Eastern parts of the territory. The area between the production and living zones is occupied by auxiliary production works. The nearest settlements to the industrial zone are at the distances of:

12 km to the West - the town of Kyshtym;

16 km to the North - the town of Kasli;

5 km to the South - the Novogorny settlement.

Besides those, there are also some little villages in the area around the "Mayak" territory by the radius of 10 km [7.1].

The extent of the sanitary and protective zone to the North-Eastern and Western directions is about 10 km. And it is widened to 18 km to the leeward Eastern direction. Its border passes along the border of dwelling area. The total area of the sanitary and protective zone is 250 sq.km, including 60 sq. km of aquatories and 150 sq.km of forests. At the territory of the sanitary and protective zone it is allowed to conduct restricted agricultural and forestry works.

Around the industrial zone of the enterprise to a radius of 40 km and within the 1957 radioactive trace area to the border of Sverdlovsk region a sanitary observation zone is established. Its total area is 1800 sq.km, including 216 sq.km of aquatories and 900 sq.km of forests. At the observation zone territory 38 settlements are situated. They are inhabited by 150 thousand people.

Two natural water reservoirs on the "Mayak"’s territory are used for industrial circulating water supply, and two man-made water basins which were origininally swamped are used for storage of medium level liquid radioactive wastes.

The production complex of "Mayak" includes:

• production reactors;
• radiochemical plant;
• radioisotopes production;
• chemical and metallurgical production works;
• chemical production works.

Besides that, a number of auxiliary works are operated at the enterprise:

• water treatment plant;
• repair and mechanical plant;
• storehouses of combustible and lubricating materials;
• motor car transportation and railway facilities;
• construction divisions.

The first production uranium-graphite reactor "A" with 100 MW power was started-up on June 19, 1948 [7.2], and it was decommissioned on June 16, 1987. Later on at the Combine a number of uranium-graphite reactors were put into operation: AV-1 (15.06.50), AV-2 (06.04.51), AI (22.12.51), AV-3 (15.09.52).

The first heavy-water reactor OK-180 with 100 MW power was put into operation on October 17, 1951 [7.3]. The OK-180 reactor was decommissioned in 1965 and then disassembled.

The next heavy-water reactor OK-190 was put into operation on December 27, 1955. The reactor worked for 10 years, and it was shut down on November 8, 1965. Later on the reactor was disassembled, and on its place in April 1966 another reactor, OK-190m, was started-up. The OK-190m reactor worked for 20 years, and it was shut down in 1986 [7.6]. Afterwards reactors of a different type, ensuring more reliable operation, were built: the "Ruslan" reactor was started-up on June 16, 1979, then "Ludmila’ reactor was put into operation [7.6].

To separate plutonium, generated in nuclear reactors, from uranium and fission products, a radiochemical plant was built at the Combine and put into operation at the end of 1948. Irradiated uranium slugs covered with aluminium claddings entered the plant and, after removing the cladding, dissolved in nitric acid. The solution, containing uranium, plutonium and fission products, was processed by using the well-known acetate-fluoride technology [7.4]. The gained experience allowed to commence in 1952 designing of three new radiochemical plants, where irradiated uranium slugs were processed after the improved acetate scheme. Later on at the plants sorption decontamination of plutonium concentrates was implemented using home-made ion-exchange resins.

In spite of improvement of the technological process, the acetate technology had a very serious disadvantage: large volumes of liquid radioactive wastes generated. As a result of many years’ investigations, conducted at research institutes and at the Combine’s Central Laboratory, a compact extraction-sorption technological process was elaborated and suggested for use [7.5]. Radiochemical production went to new technology, based on the process.

Since 1971 at the RT-1 radiochemical plant reprocessing of spent nuclear fuel of NPPs with VVER-440 and BN-600 reactors, of naval power reactors, research reactors is carried out. The plant’s production capacity is 400 ton/year [7.7, 7.11]. Twenty years’ experience of the RT-1 plant operation has shown high reliability of the technological process and of equipment. The closed nuclear fuel cycle concept was realized in the uranium line: after purification, of uranium in the form of fused uranyl-nitrate is supplied to plants for RBMK reactors’ fuel manufacturing. Plutonium separated as a result of the regeneration process in the form of dioxide is sent for storage. It is completely suitable to be used for making of mixed uranium-plutonium fuel for fast reactors [7.7].

The construction of new shops of the chemical and metallurgical plant was started in 1948. It was conducted in two stages. The first stage was designated for processing of the radiochemical plant product solutions to metallic plutonium and making articles of the metal. The second stage was put into operation after producing first lots of highly enriched uranium.

Radioactive wastes management at the IA "Mayak"

The first production reactor, radiochemical plant and other production works of "Mayak" were situated in the Techa-Mishelyak interriver area. Slightly active reactor waters were discharged into the Kyzyl-Tash Lake (water reservoir No.2). Till 1953 the Lake was flowing. From 1953 till 1956 flood waters of the Irtyash-Kasli system were passed periodically through the Lake. Since 1957 the water reservoir No.2 has been closed, and it is used as a heat sink in the system of circulating water supply of nuclear reactors. In summer to keep the necessary water level in the water reservoir No.2 it is replenished from the Irtyash Lake.

At the early period of the Combine operation radionuclides from both radiochemical plant and flowing production uranium-graphite reactors ("A", "AI", "AV-1, 2, 3") were released into the Techa River, running out of the Kyzyl-Tash Lake. However the discharge of about 1.11x10¹⁷ Bq (3 millions Ci) in the time period from March 1950 till the end of 1951 was completely considered as a contribution of the radiochemical plant. The plant’s radioactive discharges were partly stipulated by the project, but mainly they resulted from unforeseen emergency situations.

In 1949 the high level waste storage facilities at the radiochemical plant were filled up, and the problem of further operation arose. At that time it was decided to discharge the wastes into the Techa River. Since October 28, 1951 the main part of the discharges was directed to the Karachay lake, and only (3.7-7.4)x10¹² Bq/day (100-200 Ci/day) were still disposed into the Techa River [7.10]. The discharge of medium level liquid wastes of the radiochemical plant in 1949-1951 has led to radioactive contamination of bottom sediments and the River’s upper reaches’ flood-plain. To prevent the radionuclides spreading down stream, a cascade of water reservoirs No. 3, 4, 10, 11 was created [7..9, 7.10].

The dam No. 3, making water reservoir No. 3, was built in 1951 at a distance of 2,5 km from the water reservoir No. 2. Regeneration solutions from clean-up facilities, where waste waters of reactors’ and the radiochemical plant’s special canalization were reprocessed, were disposed into the water reservoir. Operating spillway to the water reservoir No. 4 is carried out over the dam No. 3.

The dam No. 4, making water reservoir No. 4, is situated in 3 km from the dam No. 3 down stream. The dam had existed earlier, and in 1956 it was built up and reinforced. Regeneration solutions of the water treatment plant are disposed to the water reservoir No. 4. Operating spillway to the water reservoir No. 10 is carried out over the dam No. 4.

The dam No. 10, making water reservoir No. 10, was built in 1956 5 km from the dam No. 4 down stream on the Techa River. It has operating spillway to the water reservoir No. 11.

The dam No. 11 was built in 1964 17 km from the dam No. 10 down stream on the Techa River. Filling of the water reservoir No. 11 was started in 1966. The water body locks up the cascade of water reservoirs, it has no spillway. Below dam No. 11, a drainage system was made to collect waters filtered through the dam’s body.

The seepage waters can be returned to the water reservoir No. 11, if the permissible levels of radionuclides concentration are exceeded.

All the cascade of water reservoirs is designated for low level liquid wastes storage. The waters are discharged directly into the water reservoirs No. 3 and No. 4, from which, due to natural water overflow, the radionuclides and salts get into the water reservoir No. 10 and then into the water reservoir No. 11. To collect on-surface run-off from the water catchement area interceptor canals were built along the water reservoirs of the cascade: the left bank canal and the right bank canal, which discharge into the Techa River below dam No. 11. Filling of the water reservoirs of the cascade occurs due to the "Mayak" discharges, atmospheric precipitations, on-surface run-off from the limited water catchment area and influx of the ground waters.

The water reservoir No. 6 is the natural Tatysh Lake, having no run-off. At present it is used for circulating water supply. Besides the cooling waters, non-process and household waters from the industrial area come into the water body after cleaning.

The water reservoir No. 17 is an engineered structure, made in a natural cavity as a result of erecting an earthen dam No. 17 in 1949. The water body is used for storage of medium level liquid wastes. At present a project of its complete elimination is being worked out.

The water reservoir No. 9 is the natural Karachay Lake. Since 1951 it is used as a medium level liquid wastes storage. Since 1988 works aimed at the water reservoir elimination are being conducted.

The characterization of accumulated radioactive materials and radioactive wastes

In the initial period of the radiochemical plant operation, while reprocessing of 1 ton of irradiated uranium slugs about 25 tons of acidic and alkaline solutions, more than 2000 tons of cooling and process water were spent, and the amount of salts generated in the process was up to 15 tons [7.1].

In the RT-1 plant as a result of reprocessing of 1 ton of spent nuclear fuel of the VVER-440 reactors 45 m³ of high level, 150 m³ of medium level and 2000 m³of low level liquid wastes are generated [7.11].

Till 1996 all the plant’s high level wastes after evaporation were solidified by vitrification. The medium level wastes will be processed by bitumization, and the low level wastes after ion exchange cleaning to the maximum permissible concentrations will be discharged into the open water reservoirs [7.8]. The data on amounts of accumulated liquid and solid radioactive wastes, as well as characterization of their storage sites are presented in Table 7.1 [7.14].

The consequences of IA "Mayak" activities

The IA "Mayak" activities led to intensive radiation contamination of the Urals area - with the highest levels in the Northern part of Chelyabinsk region. It was caused by imperfection of nuclear technologies at the initial stages of the enterprise’s operation, and lack of knowledge concerning radioactive substances behaviour in the environment. The most significant radioactive contamination of the environment and the population exposure due to the contamination took place during the first half of the time period of the "Mayak"’s operation [7.1, 7.12].

Due to lack of proper technological systems for the radiochemical production works’ liquid wastes management and an easy-going approach to the problem of disposal of such wastes into the natural aquatic systems, through the 1949-1956 time period the radiochemical plant’s wastes with total activity of 10¹⁷ Bq (2.7 millions Ci) were discharged into the small Techa River which flowed into the Iset’ River. As a result of that 124 thousand people, who had lived in the riverside area at Chelyabinsk and Kurgan Regions, underwent radiation exposure.

Design defects of the first high level liquid waste storage reservoirs led in the autumn of 1957 to radiation overheating of a tank followed by explosion of nitrate-acetate salts, contained in it. As a result of the explosion about 7.4x10¹⁷ Bq (20 millions Ci) of radioactive products were scattered by wind to significant distance, and led to radioactive contamination of the Northern part of Chelyabinsk Region and of Sourthern part of Sverdlovsk Region. The contaminated zone, called afterwards East-Urals radioactive trace (EURT), had an area about 20 thousand sq.km in the limits of minimum detectable radioactive contamination level 3.7x10⁹ Bq/km² (0,1 Ci/km²)of Sr-90. and 1 thousand km² in the limits of contamination density of 7.4x10¹⁰ Bq/km² (2 Ci/km²)of Sr-90. (Fig.7.1) [7.28-7.29]. That was adopted as the permissible level of safe living. At that time 272 thousand people lived in the whole contaminated territory. Maps of radioactive contamination of the territories with Sr-90 (Fig.7.2) and Cs-137 (Fig.7.3) were drawn up in accordance with data of investigations conducted in 1993 by the Chelyabinsk regional Center on Hydrometeorology and Environmental Monitoring [7.29].

After cessation of discharges into the Techa River the medium level liquid wastes since 1953 were disposed into the small (0,45 km²) shallow and swampy Karachay Lake. In spring 1967 the water body’s banks uncovered because of extreme drought conditions. During two weeks about 2.22x10¹³ Bq (600 Ci) of radioactive products were scattered by gusty winds over the adjacent territory. The contaminated area was 1800 km² in the limits of contamination density of 0,1 Ci/km² of Sr-90. The contamination with essentially lower level, as compared to 1957 explosion, was laid mainly on the EURT territory in the limits of Chelyabinsk Region. 40 thousand people underwent additional radiation exposure.

The fourth factor of the environment contamination and the population exposure connected with IA "Mayak" activities were the regular releases of process radioactive products into the atmosphere from the plants’ stacks. The greatest releases, caused by the growth of the production capacities and imperfection of the gas clean-up systems, took place during the first ten years of the "Mayak"’s operation.

As of January 1, 1996, the contaminated lands’ area was 2736 km² (see Table 7.2). The soils are contaminated with Cs-137 and Sr-90.

7.2.2. The Siberian Chemical Combine (SCC)

The construction of the SCC was started in March 1949 [7.15].

The production site of the SCC is situated on the second super-flood-plain terrace of the Tom’ River right bank at a distance of 12-15 km to the North of Tomsk city. The locality relief is obviously sloped to the West side towards the river. There are many small rivers and streams, flowing to the West, on the terrain. The riverside part of the area is swampy and falls to the main river behind the embankment. The left bank of river is low.

The Combine includes the following production works:

• reactors - plutonium production, electric and heat power generation;
• radiochemical plant - reprocessing of irradiated materials aimed at separation and purification of uranium and plutonium salts;
• chemical and metallurgical plant - production of metallic uranium and plutonium;
• sublimate plant - U₃O₈ production, UF₆ production;
• isotope enrichment plant - enriched uranium production;
• nuclear fissile materials storehouses and facilities for storage of uranium oxides, uranium hexafluoride, articles of metallic uranium having different enrichment, irradiated in production reactors standard uranium slugs, plutonium oxides, articles of metallic plutonium;
• objects for radioactive wastes processing, storage and disposal;
• thermal electric plant - electric and heat power generation.

The construction of the uranium enrichment plant was started in 1951. The first stage of the plant was put into operation on July 26, 1953. Till 1973 the gas diffusion technology was used for uranium isotopes separation, later on the plant went to highly efficient centrifuge technology. At present, because of reduction of the State order for enriched uranium, separation capacities are not fully utilized at the plant. This allowed to render commercial services to foreign firms interested in uranium enrichment.

The construction of the first production uranium-graphite reactor was started in 1952. It was put into operation on November 20, 1955. The I-1 reactor went through several stages of modernization, it was operated for 35 years and was shut down on August 21, 1990 in connection with the reduction of weapon grade plutonium production.

In 1954 a sketch design of a new type power and production complex known as the Siberian Nuclear Plant was carried out. In September 1958 the first stage of the NPP-1 based on the 100 MW EI-2 uranium-graphite reactor was put into operation. The third reactor AD-3 was started-up on July 14, 1961. The 2-nd and the 3-d reactors were stopped, respectively, on 31.12.90 and on 14.08.92. In 1959 the construction of the two-purpose uranium-graphite reactors ADE-4 and ADE-5 was started. The reactors became operating in 1965 and 1967, respectively, and they are still working. The I-1 reactor had a single pass system of its core cooling, so the cooling water after dilution was discharged into the Tom’ River. The other four reactors had closed cooling systems.

The uranium hexafluoride production (sublimate) plant was constructed in 1951. In April 1954 the anhydrous hydrogen fluoride production department was put into operation, and in a year the uranium tetrafluoride production department was started-up. The plant has been modernized, that allowed to rise its production capacity by several times and to decrease releases and disposal of radionuclides and toxic chemical substances by tens and hundreds times.

The radiochemical plant design was carried out in 1953-1961. In August 1961 the first stage of the plant and in October 1962 its second stage were put into operation. The reprocessing of irradiated uranium slugs was conducted using the acetate precipitation scheme [7.4].

In 1983 the plant went to high-capacity extraction technology, that allowed to stop the analogous production works at the IA "Mayak" and besides, to decrease significantly the volumes of radioactive wastes [7.5].

In 1958 the decision was taken to build a chemical and metallurgical plant at the Siberian Chemical Combine, and in August 1961 the plant produced its first products.

Radioactive waste management at the SCC

As a result of reprocessing of irradiated uranium at the Combine great amounts of high, medium and low level radioactive wastes have been accumulated.

Solutions and sludges are attributed to liquid radioactive wastes. All the wastes are divided into process and non-process ones. The main amount of liquid process wastes (more than 95 %) are generated at the radiochemical plant. The wastes disposal into deep underground strata has been adopted at the SCC as a main method of liquid radioactive wastes management. The high level wastes undergo intermediate storage in stainless steel reservoirs, and then, after corresponding treatment, they are sent to underground disposal. The medium level wastes after corresponding treatment are also sent to underground disposal. For intermediate storage of liquid radioactive wastes both open on-surface storage facilities and special closed type storage facilities are used. Medium level process wastes of the chemical and metallurgical production works are sent for storage into an open pool. Process wastes of the enrichment plant are added to the wastes sent for underground disposal. Liquid radioactive wastes of the sublimate plant are sent to two sludge-storage facilities.

Non-process liquid radioactive wastes and sludges are divided by the method of their further processing into liquid wastes, sent for underground disposal, and those, which are not subjected to processing. Low level non-process wastes of all plants are sent to two water reservoirs, from which they go to clean-up facilities for processing up to 50% of the cleaned-up waste-waters undergo underground disposal. Another part after cleaning to standard levels (coagulation, mechanical cleaning, ion exchange) is sent for disposal into the river through an intermediate water reservoir-settler.

The liquid radioactive wastes, which are not subjected to processing, are sent to open sludge-storage facilities. Sludges, filtering materials and regenerates, coming from clean-up facilities, are mainly in that category.

The methods of solid wastes management depend on the waste type. Depending on the specific activity level, they are either disposed into earthen or concrete burials, or piled-up in special compartment at sites of regular storage. Solid wastes of production reactors, enrichment and uranium production plants are stored and disposed at the plants’ production sites. Since 1961 a specially equipped facility is used for burial of solid radioactive wastes of the radiochemical and chemical & metallurgical plants. Low level solid wastes are disposed in trench type burials, and medium and high level wastes - in concrete structures.

Liquid radioactive wastes (LRW) storage facilities

Open storage facilities and underground disposal sites are used in the LRW management scheme. To process the LRW at the SCC there is a system of open storage facilities, two underground disposal sites, a low level waste processing ground and a station for medium and high level waste treatment.

Basins B-1, B-2, B-25

At the first stage of the radiochemical plant operation medium level LRW were discharged into the B-1 basin, and then - into the B-2 basin. Afterwards, as the underground LRW disposal site was put into operation, the basins were used as intermediate reservoirs for intermediate storage of solutions before pumping them into the underground strata. Now they are removed from service. The total activity collected there of long-lived nuclides is estimated to be 4.66x10¹⁸ Bq (126 MCi). The reservoirs are not large in volume, and in drought summer drying up of a part of the water is possible.

The B-1 basin is an on-surface storage facility, having a 1 m thick loamy wall at the bottom and slopes. The wall is covered with a 1 m thick soil layer. Its area is 60,3 thousand m², its capacity is 150 thousand m³, actually filled volume is 110 thousand m³. The total activity of radionuclides, collected in the basin, is estimated at 2.7x10¹⁸ Bq (73 MCi). At present works on decommissioning the basin are being conducted.

The B-2 basin is an on-surface storage facility, having a loamy wall 1 m thick at the bottom and slopes. The wall is covered with a soil layer I m thick. Its area is 51,4 thousand m², its capacity is 135 thousand m³, actually filled volume is 63.7 thousand m³, the collected radionuclides total activity is 1.87x10¹⁸ Bq (50,5 MCi). At present works on decommissioning the basin are being conducted. Since 1991 works have been started on filling the B-2 basin with soil.

The B-25 basin is an on-surface storage facility with a loamy wall I m thick at the bottom and slopes. The wall is covered with a soil layer I m thick. Its area is 10 thousand m², its capacity is 20 thousand m³, actually filled volume is 13 thousand m³. Radionuclides with total activity of 5.2x10¹³ Bq (1400 Ci) are collected in the basin. Annually 1300 m³ of LRW come into the basin from the chemical & metallurgical plant, and the same volume of LRW are sent to the RKh-1 sludge-storage facility after some retention.

Sludge-storage facilities

The RKh-1 is an on-surface LRW storage facility, having a loamy wall 0,45 m thick at the bottom and slopes. The wall is covered with a soil layer 0,5 m thick. Its area is 20 thousand m³, its capacity is 100 thousand m³, actually filled volume is 70 thousand m³, the total radionuclides activity is 6.66x10¹³ Bq (1800 Ci). Annually up to 100 thousand m³ of LRW come to the sludge-storage facility, used as an intermediate settler, from the enrichment and UF₆ production plants, as well as from clean-up facilities, and the same volume of solution is sent to the RKh-2 sludge-storage facility.

The RKh-2 is an on-surface storage facility, having a loamy wall 0,45 thick at its bottom and slopes. The wall is covered with a soil layer 0,5 m thick. The sludge-storage area is 46 thousand m², its design capacity is 210 thousand m³, actually filled volume is 84,5 thousand m³. Annual receipt to the sludge-storage facility from the RKh-1 is 100 thousand m³, and after settling the same volume is sent to underground disposal. The radionuclides activity in the sludge-storage facility is estimated at 3.33x10¹³ Bq (900 Ci).

Water storage reservoirs

VKh-1 is an engineered flowing water storage reservoir, used for settling and intermediate holding of waste waters. Its bottom has no water proofing. Its area is 300 thousand m², its volume is 500 thousand m³, actually filled volume is 375 thousand m³, the collected radionuclides activity is 2.96x10¹² Bq (80 Ci).

VKh-3 is an engineered flowing water storage reservoir. It is a part of the Combine’s complex of clean-up facilities and is used for balancing, settling and intermediate holding of special canalization waters before cleaning. The reservoir’s bottom is a natural soil, its area is 1362 thousand m², its volume is 2470 thousand m³, actually filled volume is 2336 thousand m³, the total radionuclides activity is 2.22x10¹⁴ Bq (6000 Ci). Annually about 1800 thousand m³ of LRW enter the water reservoir from production works, and the same volume of waste waters is sent to VKh-4.

VKh-4 is a water storage reservoir placed at the cascade after the VKh-3, before clean-up facilities. Its bottom has no damp proofing. Its area is 1350 thousand m², its volume is 4350 thousand m³, actually filled volume is 2880 thousand m³. The total radionuclides activity is 4.44x10¹² Bq (120 Ci). Annually 1800 thousand m³ of waste waters enter the water reservoir, and the same volume is sent to the Combine’s clean-up facilities.

Underground disposal of liquid radioactive wastes [7.16-7.17]

The "site 18" is used for low level wastes disposal (up to 6300 m³/day), the "site 18a" is used for medium level wastes disposal (up to 550 m³/day). The latter site was also used for experimental disposal of limited portions of wastes, which were conditionally considered as high level ones. Now the high level wastes are not disposed. The underground storage sites are situated close to the main production complexes of the Combine in the limits of its sanitary & protective zone. The waste contain uranium fission products, including isotopes of strontium, zirconium, niobium, ruthenium, cesium, cerium, etc. as well as non-recoverable microconcentrations of uranium and transuranium elements, salts, detergents, acids, alkalines, finely dispersed solid materials.

Before disposal treatment of the wastes treatment is carried out at the Combine’s clean-up facilities and at the radiochemical plant in order to provide consistency of the wastes with the geological medium as well as additional extraction of long-lived transuranium elements before disposal.

The wastes are transferred to disposal by pipelines, pumping is carried out through a system of injection wells (there are 37 wells in total). The injection pressure is up to 2 MPa at the "site 18’ and up to 1,2 MPa at the "site 18a". Within and outside the limits of the disposal sites there are 244 observation wells used for the geological medium state and waste migration control.

The medium level wastes disposal at the "site 18a" is carried out into the 2-nd sandy stratum, lying in the depth interval of 315-340 meters. The strata used for LRW disposal are separated, underspread and covered by weakly permeable loamy floors, isolating the strata, containing the LRW, from the surface of not deeply occurring underground waters. The natural speed of water movement in the strata is 3-5 meters a year. Radionuclides are intensively retained by the rocks.

Special geological prospecting works and investigations preceded creation of the underground disposal sites. They allowed to substantiate, in principle, the disposal feasibility and safety. The license, giving the right to use underground disposal, has been received.

Solid radioactive wastes (SRW) storage facilities [7.14]

In the more than 40 year period of the Siberian Chemical Combine’s operation more than 130 thousand tons of solid radioactive wastes have been generated.

Data on accumulated solid and liquid radioactive wastes and characterization of the wastes’ storage and disposal facilities are presented in Table 7.3.

Radiation situation in the SCC area

The adequncy of the radiation situation in the SCC area is estimated on the basis of comparison of the data of radiation monitoring in the environment around the Combine with the sanitary standards and, if necessary, - with background levels [7.20].

The radiation monitoring is carried out on the territory of the observation zone (its area is 1560 sq.km, its radius is 15-20 km). The main objects of the control are as follows:

• Releases into the atmosphere (19 radionuclides).
• Waste-waters (17 radionuclides).
• Near-ground layer of the atmospheric air at nine stationary points, located in the town and around the Combine at the radius of 15-50 km (10 radionuclides and gamma-background).
• Soil, grass and snow in the town and in 20 settlements, situated around the Combine at the radius of 15-20 km (Sr-90 and Cs-137).
• Underground waters in 77 wells at the underground disposal site territory and in 48 wells outside the site.
• Open water reservoirs (Tom’ and Ob’ Rivers) twice a year at a distance of 150-200 km downstream of the Combine’s waste waters’ outlet and once a year - 700-800 km downstream of the outlet. Periodically, in summer, lakes are examined in the Combine’s area.

According to results of 1993 and 1994 monitoring , the radiation situation in the areas, surrounding the SCC, may be specified by the following data.

Radioactive products released into the atmosphere were in the range of 0,1-0,6 % of the maximum permissible levels (including: sum of alpha-emitting nuclides - 0,3 %, sum of beta-emitting nuclides and noble radioactive gases - from 0,1 to 0,3 %, I-131 - from 0,2 to 0,4 %, Sr-90 - 0,6 %). Absolute values of radionuclides content in the near-surface layer of the atmosphere in the area, surrounding the SCC, in 1994 were ( Bq/l):

The content of Ru-103, 106, Ce-144, Zr-95, Nb-95 was in the range of (0.022-0.074)x10^-7 Bq/l in all the marked points. The I-131 content was 1.11x10^-5Bq/l in all the marked points.

Radionuclides released with the Combine’s waste-waters at the point of their discharge into the Tom’ River were in the range of 0,6 to 76,5 % of the specified maximum permissible levels.

At settlements Chernil’shchikovo and Samus’ situated along the Tom’ River downstream of the discharge point, the Mn-54, Mn-56, Co-58, Fe-59, Zn-65, Sr-89,90, Ru-106, Cs-137, Ce-144 radionuclides were not detected with lower sensitivity limits of measurement by 2-5 orders of magnitude lesser than the corresponding DC_B values.

With lower sensitivity limits of measurement 0.67 Bq/l for Cs-137, 0.19 Bq/l for Sr-90, 0.52 Bq/l for Ru-106, 4,1x10² Bq/l for tritium (by 100-1000 times lesser, than the corresponding DC_B values) the radionuclides were not detected in underground waters in observation wells of the local monitoring system (by the radius of 12-15 km). The above mentioned nuclides were not detected in samples of artesian drinking water as well.

According to the environmental monitoring data for 1995, the radiation situation in the area, surrounding the SCC, can be specified as follows [7.21]. Radioactive products releases into the atmosphere did not exceed 0,2-0,3 % of the maximum permissible values. Radionuclides releases in the point of LRW outlet into the Tom’ River were in the range of 0,7-33 % of the maximum permissible level.

Radionuclides content in the near-ground layer of the atmosphere was at the level, close to the background values, that is by 1-8 orders of magnitude lower than the corresponding permissible concentration values, specified by the NRB-76/87 Rules for the atmospheric air.

Cs-137 and Sr-90 content in the soil on the observation zone territory is within the limits of values, corresponding to the global level of (1.11-3.7)x10⁹ Bq/km². The only exception is the territory situated at the leeward side (to the North-East) at a distance of 8-13 km from the Combine’s industrial area where the Cs-137 content is 2-3 times higher compared to the global level that is a result of many years operation of the SCC production works.

Cs-137, Ru-106, Sr-90 and tritium radionuclides were not detected in underground water samples of the local observation wells system with the lower sensitivity limits of measurement 100-1000 times lower than the permissible concentration levels set by the NRB-76/87 Rules for drinking water.

The release of radioactive products that occurred in the accident on April 6, 1993, had no significant effect on the radiation situation. The contamination was local and was mainly Ru-103, Ru-106, Zr-95, Nb-95 radionuclides. At present the gamma-exposure rate on the trace of the release does not exceed 20 mR/h. In Georgievka village the exposure rate has decreased to the natural background level (6-8 mR/h).

In 1996 there were no accidents at the Combine. The radionuclides releases and discharges were at the 1995 level. In that period at the SCC irradiated uranium slugs of operating production uranium-graphite reactors were reprocessed, that is just the same amount as in 1995.

Emergency releases of radioactive products [7.18-7.19]

For the time period of SCC operation 36 radiation accidents of different scale have occurred. The most serious accident (3 class event, according to the international INES scale) took place on April 6, 1993.

Among the rest 35 emergency situations two radiation accidents should be marked. In June 1977, while reprocessing irradiated uranium slugs at the radiochemical plant, some insufficiently cooled slugs got into the processed lot. That led to elevated release of I-131 (8.4x10¹¹ Bq for two weeks) into the atmosphere. The monthly maximum permissible level was exceeded by 2,4 times. On May 11, 1977, at the radiochemical plant, as a result of a blowhole in a pressure pipeline at an injection well, while pumping LRW, spread of 8-14 m³ of the solution occurred. That led to contamination of a plot 200-220 m long and 10-40 m wide. Gamma-exposure rate reached 140 R/h. Later on all the contaminated zone was eliminated.

Accident of April 6, 1993 [7.19-7.22]

On April 6, 1993 at 12.58 (local time) at the radiochemical plant of the SCC, while conducting regular operations of preparing uranium solution for an extraction purification, destruction of a process apparatus AD-6102/2, in which the operations were carried out, occurred as a result of fast growth of pressure.

The explosion and release of gas and aerosol mixture led to break-down of the upper ceilings of the chamber, where the apparatus was installed, as well as of a part of the shop’s building structures, caused ignition of a section of the roofing (the fire was eliminated in 10 minutes) and partial release of radioactive products, contained in the gas and aerosol mixture, into the atmosphere.

The apparatus was a stainless steel vessel, its volume was 34,15 m³. At the moment of destruction the vessel contained 25 m³ of uranium nitric acid solution, which at the preceding stage was in contact with organic solution (30 % of tributhyl-phosphate in kerosene). The solution contained 8773 kg of uranium and 320 g of plutonium, its total activity was 2.07x10¹³ Bq, including 7.4x10¹¹ Bq of alpha-emitting nuclides.

The following settlements are located at the contamination zone: Georgievka (16 km from the radiochemical plant, 30 inhabitants, gamma-exposure rate was from 18 to 45 mR/h) and Chernaya Rechka (34 km from the radiochemical plant, gamma-exposure rate was from 12 to 50 mR/h).

As to the rest of recorded accidents at the SCC, they have not led to radioactive products’ releases into the environment exceeding the specified maximum permissible levels.

The total area of contaminated lands was 10.392 km² on 01.01.96 [7.13]. The data on the contaminated lands are presented in Table 7.4. The soils are contaminated with Cs-137 and Sr-90 radionuclides. There are no published data on Sr-90 and Cs-137 distribution on the contaminated lands.

More than 9.0 km² of the total contaminated lands area at the SCC are in the underground LRW disposal site territories, as well as to the B-1, B-2, B-25 basins, RKh-1, RKh-2 sludge storage facilities, VKh-1, VKh-2 water storage reservoirs.

The main effort of the SCC operation from the moment of starting-up production works is the minimization of radionuclides’ effects on the population and the environmental objects. At the initial stage of the radiochemical plant (the main source of LRW) operation the minimization was achieved due to presence of basins for storage of medium level process wastes. Putting into operation of the underground LRW disposal sites allowed to localize hundreds of millions of Ci of long-lived radionuclides in geological medium within the limits of the sanitary & protective zone and mining allocation of the disposal. The solid RW are isolated in reliable reinforced concrete facilities or in suitable burials.

On the whole it can be concluded, that the stable operation of the enterprise allowed to ensure quite satisfactory radiation situation both at the production site and in the dwelling areas in the Combine’s impact zone.

7.2.3. The Mining & Chemical Combine (MCC)

The decision, concerning the MCC construction, was taken in 1950. It was decided to place the main objects of the MCC in a rock mass on the right bank of the Yenisei River 60 km down stream of Krasnoyarsk city. The Combine’s underground site was chosen at the place where the Atamanov chain of hills came right up to the Yenisei River. The territory for the town’s construction was chosen ten kilometers to the South upstream of the main production site on the former flood land of the Yenisei River [7.24].

The area of the Mining & Chemical Combine’s territory is about 360 sq.km along the right bank of the Yenisei River. The South-Western bearing of the wind is dominating. The observation zone dimensions are: 15 km towards the predominating winds bearing (to the North-East), 9 km of the windward side (from the South-West), from 2 to 8 kilometers towards other directions. The population in settlements on the area controlled by the Combine is:

• the town of Zheleznogorsk - more than 80 thousand;
• the Dodonovo village - about 600;
• the Bol’shoi Balchug village - about 400;
• the Atamanovo settlement - about 5000.

The river, flowing close to the Combine’s territory, is a controlled non-freezing all the year round water stream of the hydroelectric power plant.

The Combine was designated for weapon grade plutonium (WGP) production. The WGP is generated in production uranium-graphite reactors. The irradiated uranium is processed at the radiochemical plant to separate uranium and plutonium and decontaminate them from fission products. Plutonium dioxide and fused uranyl-nitrate are the Combine’s end products, which are sent to other enterprises of the Minatom of Russia. Liquid releases after the reprocessing as well as gaseous effluents undergo decontamination at the clean-up facilities of the Combine. Solid radioactive wastes are sent to special storage facilities of the enterprise.

In 1977 the construction of the RT-2 plant was started [7.23]. The plant is designated for interim storage and further reprocessing of spent nuclear fuel (SNF) of the former USSR nuclear power plants with VVER-1000 nuclear reactors in order to return unburnt uranium and generated plutonium into the nuclear fuel cycle for repeated use.

According to the plant’s project, it was foreseen to have in its structure reactor and radiochemical production works, nuclear power-and-heating facility, objects for water supply and ventilation, placed in rock workings in the depth of the mountain range. Besides that, the project foresaw construction of objects for liquid and solid radioactive wastes storage and processing, for heat supply and of other auxiliary service necessary for providing normal work of the industrial enterprise and living of the population.

In December 1985 the first stage of the RT-2 plant - the complex of the storehouse for transportation, reception and interim storage of spent nuclear fuel - was put into operation [7.23].

There were three production reactors at the MCC. The first of them, AD, was started up on August 26, 1958, the second one, ADE-1, - on July 20, 1961. Both reactors are thermal, uranium-graphite, water-cooled ones of channel type. Natural uranium slugs were loaded into the core. The reactors’ safe operation at a set power level and reliable plugging of the chain nuclear reaction in the core in case of emergency were ensured by the control, monitoring and protection systems. The reactors worked in single-pass mode, disposing cooling water into the Yenisei River. The AD and ADE-1 reactors were stopped on June 30, 1992 and on September 29, 1992, respectively.

The third, two purpose ADE-2 reactor was put into operation in 1964. It is used for both plutonium and electric power production, as well as for water heating (since 1966) to supply the town of Zheleznogorsk with heat and hot water. The power-and-heating complex includes six turbo-generators, thirty steam generators, the first circuit pumping plant, an electric substation and other facilities.

The radiochemical plant was put into operation in 1964. It is designated for extracting of plutonium from irradiated uranium. The plant’s basic process flow chart includes operations of metallic uranium dissolving in nitric acid, multistage extraction reprocessing of the solution to separate uranium and plutonium and to decontaminate them from radioactive fission products and deep purification of the plutonium concentrate by using sorption method. Uranyl-nitrate and plutonium dioxide are the end products of the reprocessing of the irradiated uranium slugs. Because of sharp reduction of weapon grade plutonium production the reprocessing of irradiated uranium slugs has been ceased at the plant. High level liquid RW are sent to special storage facilities, medium and low level RW after holding and corresponding treatment are sent to the "Severnyi" site for underground disposal into deep geological strata-collectors. Gaseous and aerosol effluents undergo multistage cleaning and then are discharged into the atmosphere.

The RT-2 is designated for reception, interim storage and further reprocessing of nuclear power plants’ spent fuel. Its design capacity is 1500 tons of irradiated uranium a year. Fuel assemblies on the basis of mixed uranium-plutonium oxide (MOX-fuel) and regenerated uranium are to be the plant’s end products. The RT-2 plant process flow chart is based on extraction technology of uranium and plutonium separation and purification. Liquid radioactive wastes, emerging as a result of SNF reprocessing, have to undergo fractionation followed by solidification into glass-like or mineral-like compositions. The RW management processes, adopted in the plant’s design, comply with the present-day concepts, allow to decrease maximally their volumes and to provide safe storage conditions.

The first stage of the plant - the complex of SNF storehouse - was put into operation in 1985. The storehouse design capacity is 6000 tons. At present it is filled to 16 % [7.23].

The characterization of accumulated radioactive wastes at the enterprise on the whole

The whole nuclear production complex, including three reactors and a radiochemical plant is situated under the ground, at the depth of 250-300 m and, unlike the IA "Mayak" and the SCC, has safe biological shielding. The complex is equipped with a ventilation system with filters, that allows to ensure protection against activity from outside.

As a result of the MCC operation, large amounts of liquid and solid high, medium and low level radioactive wastes have been collected.

The solid and liquid RW are kept in storage facilities on the Combine’s territory.

Liquid radioactive wastes [7.14]

Liquid RW, emerging as a result of the production works operation, depending on the activity level, are sent to cleaning facilities, collected in special tanks or in open storage reservoirs. After corresponding treatment and cleaning they are sent to underground disposal (the "Severnyi" site). Decontaminated waters are discharged into the Yenisei River.

The basin 365 is an open type water storage reservoir, made on the first super-flood-plain terrace of the Yenisei River. It is designated for reception and interim storage of the reactors’ emergency waters and off-grade non-process waste-waters of the radiochemical plant before sending them to cleaning facilities. The liquid RW isolation from ground waters is provided due to anti-filtering shield of clay, two asphalt layers on the bottom and slopes, as well as due to presence of a bottom and bank draining system for interception and collecting of probable leakages in case of a damage of the water proofing.

The basin 366 is an open type water storage reservoir, made on the first super-flood-plain terrace of the Yenisei River. It has been built by hydraulic deposition of soil and is designated for reception of decontaminated (in accordance with the set standards) waters from the Combine’s cleaning facilities in order to provide their holding, settling and filtration before their discharge into a stream, and then into the Yenisei River. With maximum filled basin the water filtrates through the bottom and the dam body and in case of excessive filling it discharges over the berm.

The basin 354a is an open pit type water storage reservoir, built in practically water-proof rocks and designated for reception, composition balancing and interim storage of regeneration solutions and sludges from cleaning facilities, as well as of low level wastes and condensate after evaporation of the radiochemical plant process wastes before sending them to underground disposal. The wastes are isolated from contact with ground waters due to two-layer anti-filtering shield on the bottom and slopes and presence of a draining system between the shield’s layers, as well as due to engineered geological and hydrogeological structure of the area - presence of a thick covering of uniform and practically water-proof clays.

The basin 354 is situated 100 m from the basin 354a, on a site with identical engineered geological and hydrogeological conditions. Its destination and design are analogous to those of the basin 354a. At present the basin is completely emptied, and works on its elimination are being conducted.

The underground liquid radioactive wastes disposal site

The "Severnyi" site is used for disposal of low level radioactive wastes (up to 800 m³ a day) into the second sandy stratum and of medium level radioactive wastes (up to 500 m³ a day) into the first sandy stratum. Earlier experimental disposal of some portions of wastes, conditionally attributed to high level ones, was carried out into the first sandy stratum.

The site is situated in 12 km from the Combine’s main production works within the limits of the sanitary & protection zone of the enterprise. The disposed wastes contain radonuclides of uranium fission products, including strontium, cesium, zirconium, niobium, ruthenium, cerium, as well as trace amounts of uranium and transuranium elements, unrecoverable in the solutions’ processing. Before the underground disposal the RW treatment is carried out at the Combine’s cleaning facilities and at the radiochemical plant in order to provide consistency of the wastes with the geological medium, as well as additional recovery of long-lived transuranium elements.

The wastes are transferred to disposal by pipelines. The pumping is carried out through a system of injection wells (there are 16 such wells in total). The injection pressure is about 2 MPa. Within and outside the disposal site there are 70 observation wells used for control of the state of geological medium and the wastes’ migration.

The first and second sandy strata used for the disposal occur in the depth intervals of 300-500 m and 180-280 m, respectively. The strata are underspread, separated and covered by loamy floors, isolating the strata, containing radioactive wastes, from the surface and from non-deeply occurring underground waters. The natural speed of water movement is 5-6 m a year in the first stratum, and 10-15 m a year in the second stratum. Radionuclides are intensively retained by the rocks.

Special geological prospecting works and explorations preceded creation of the "Severnyi" underground disposal site. They allowed to substantiate the feasibility of RW injection and the disposal safety. At present the license, allowing disposal use has been received.

The underground disposal of liquid RW allowed to eliminate the impact of huge amounts of radionuclides on the population and on the environment. The state of the wastes and the containing geological formations is controlled by conducting complex observations and measurements. Their results allow to confirm the disposal sites safety and to take measures for additional isolation of RW, if necessary. Probable complications and emergency situations while carrying out the disposal will not lead to disastrous consequences, connected with large scale effect on the environmental systems.

Radioactive wastes storage facilities [7.14]

For the years of operations at the Mining & Chemical Combine great amounts of solid and liquid RW have been generated. Data on the accumulated wastes are presented in Table 7.5.

Radiation situation in the MCC area

Radionuclides’ releases into the atmosphere in 1993 did not exceed the standard levels by any components [7.25]. The releases of radioactive noble gases were at the level of 0,6 % of the maximum permissible value, and the sum of released beta-emitting nuclides was at the level of 0,9 % of the standard value. The mean annual volume activity of radionuclides in the near-surface layer of the atmosphere in the sanitary & protective zone of the MCC was lower than DC_B: for Co-60 - by 4,3x10⁶ times, for Ru-106 - by 3,8x10⁵ times, for Ce-144 - by 2,8x10⁵ times, for Cs-137 - by 3,0x10⁶ times.

Since decommissioning of the AD and ADE-1 single-pass reactors the volume activity level in the near-surface layer of the atmosphere has fallen by 8 times. In the nearest to the MCC settlements (the Bol’shoi Balchug village and the town of Zheleznogorsk) in the near-surface layer of the atmosphere, mainly, only Cs-137 is detected. Its volume activity is by 7,6 times lower, as compared to DC_B. On the whole the effect of gaseous and aerosol effluents of the active production works of the MCC on the contamination of the sanitary & protective zone and of the observation zone is practically not detectable against the global background level.

After the AD and ADE-1 single pass reactors’ shutdown the release of radionuclides into the Yenisei River is mainly determined by short-lived isotopes (Na-24, P-32), coming with cooling water of the control & protection system of the two-purpose ADE-2 reactor. The volume activity of the water discharged into the Yenisei River is in the range of 1,2-7,0 DC_B for Na-24 and 0,05-1,5 DC_B - for P-32. On the whole the summed release of all radionuclides did not exceed the standards and was in the limits of 0,3-6,0 % of calculated values of the maximum permissible release. The volume activity of radionuclides in the river’s water does not exceed 0,3 DC_B at the discharge location, 0,08 DC_B - 500 m from the discharge location down stream and 0,015 DC_B - at 15 km from the discharge location down stream (1 km up-stream of the first settlement on the right bank of the Yenisei River - the Bol’shoi Balchug village). The values of Pu-239 and Pu-240 volume activity (summed) are lower than the sensitivity limit of the measurement method, and they do not exceed 8,0x10^-5 DC_B. The maximum values of Sr-90 and Cs-137 volume activity are 1,2x10^-3 and 6,0x10^-3 of DC_B, respectively. In case of arranging centralized water supply from the Yenisei River, at the first settltment on the right bank (the Bol’shoi Balchug village) the effective dose limit due to the river water consumption would be 5 m Sv/year.

On the whole, after decommissioning of the single-pass reactors the water surface exposure rate and volume activity of all radionuclides (summed) in the water do not exceed standard values set by the NRB-76/87 at the discharge location. The radioecological situation in the flood-plain of the Yenisei River is mainly determined by the formerly conducted discharge of the single-pass AD and ADE-1 reactors’ cooling waters. The values of exposure rate in the river side at the area of living and economical activity of the population in 15-500 km downstream the MCC discharge location do not exceed 10-15 mR/h. On particular islands and in some local sections of the flood-plain 15-250 km downstream of the MCC discharge location there are "spots" with exposure rate level, reaching 200 mR/h.

In 300 km-zone the radioactive contamination of the flood-plain of the Yenisei River is mainly determined by two intense floodings (1966 and 1988) with the river water discharge up to 21 000 m³/s, that have led to carry-over of a part of bottom sediments, containing radionuclides, to islands and flood-plain’s plots. At present in that zone there are some plots with gamma-exposure rates in the range from 30 to 200 mR/h.

As on the 01.01.96 the area of contaminated lands was 7.79 km² [7.13]. The lands are contaminated with Cs-137 and Sr-90 radionuclides. The data on the contaminated lands are presented in table 7.6.

More than 5.7 km²of the total contaminated lands area at the MCC fall to the underground LRW disposal site territory, as well as to the basins 354, 354a, 365, 366.

Reliable information about the existing situation on radioactively contaminated territories is needed to take decisions, concerning necessity of carrying out remediation measures. That is why permanent observation and monitoring ought to be conducted, i.e. a system of radioecological control of the areas, of radioactive contamination should be created.

7.3. Characterization of the available data

The data on the three industrial enterprises presented in this Chapter give rather complete representation of quantitative characteristics concerning accumulated radioactive wastes and their activity.

Some years ago (as on January 1, 1990 and on January 1, 1993) inventories of sites and objects for treatment, utilization, collecting, storage and disposal of radioactive materials and ionized radiation sources were conducted.

Annually the enterprises present to the Ministry data on radioactive products’ discharges into water reservoirs and effluents into the atmosphere, and on radioactively contaminated and remediated territories. Databases on radionuclides’ discharges into water reservoirs and effluents into the atmosphere, as well as on radioactively contaminated lands are available since January 1, 1993.

Table 7.1

The amount of accumulated solid and liquid radioactive wastes and characterization on their storage sites at the IA "Mayak"

Table 7.2

Contaminated lands at the IA "Mayak"

Table 7.3.

The amount of accumulated solid and liquid radioactive wastes and the characterization of their storage sites at the SCC

Table 7.4

Contaminated lands at the Siberian Chemical Combine

Table 7.5.

The amount of accumulated solid and liquid radioactive wastes and characterization of their storage sites at the MCC

Table 7.6

References

7.1. A.K.Kruglov, How the nuclear industry was created in the USSR, Moscow. TsNIIAtominform, 1994, 380 pp. (In Russian).

7.2. V.I.Merkin, "The first production nuclear reactor of the Soviet Union. Its erection and starting-up". - In the Collection of reports delivered at the Jubilee Scientific & Practical Conference of the Minatom of RF "50 Years of the Nuclear Science and Engineering of Russia", Moscow, 1996.

7.3. A.K.Kruglov, "On the first heavy-water nuclear reactors in the country", Information Bulletin of the Public Information Centre on Nuclear Energy, No. 7-8, Moscow, TsNIIAtominfirm, 1994.

7.4. V.I.Zemlyanukhin, "The creation of radiochemical technology of plutonium production", Science and Society: History of the Soviet Nuclear Project (40-s - 50-s). The International Symposium, held in Dubna, May 14-18, 1996. - Abstracts.

7.5. B.S.Zakharkin, "The elaboration of technology of spent nuclear fuel reprocessing", Pages of the History of VNIINM. The Recollections of Workers, v.2, Moscow, TsNIIAtominform, 1993.

7.6. V.I.Fetisov, "The IA "Mayak" in front of a new challenge - the conversion", Atom-pressa, No. 31, 1993.

7.7 Yu.V.Glagolenko, E.G.Dzekun, S.I.Rovnyi, V.P.Ufimtsev, "The reprocessing of spent nuclear fuel at the IA "Mayak", Abstracts of reports at the 3-d International Radioecological Conference "The Destiny of Spent Nuclear Fuel: Problems and Reality" held in Krasnoyarsk, June 22-27, 1996".

7.8. A.S.Polyakov, "Irradiated nuclear materials and radioactive wastes management". - In the Collection of reports delivered at the Jubilee Scientific & Practical Conference of the Minatom of RF "50Years of the Nuclear Science and Engineering of Russia", Moscow, 1996.

7.9. A.V.Akleev, et.al. Radioactive contamination of the environment in the South Urals region and its effect on the health of the population. Ed by Academician L.A. Buldakov. - Moscow, TsNIIAtominform, 1991.

7.10. A.K.Kruglov, Yu.V.Reshet’ko, Yu.V.Smirnov, "On the restoration of radioactively contaminated territories", Information Bulletin of the Public Information Centre on Nuclear Energy, No.10, 1992.

7.11. V.F.Men’shchikov, V.N.Yakimets, "Criteria of considering projects for spent nuclear fuel reprocessing are necessary".- In the Collection of reports of the Second International Radioecological Conference "After the Cold War: Disarmament, Conversion and Security", held in Krasnoyarsk, September 12-16, 1994.

7.12. The environmental consequences of the IA "Mayak" activities, The Information Sheet of the Environmental Centre of the IA "Mayak’, 1992.

7.13. The Federal Programme "Restoration of territories contaminated as a result of activities of enterprises, producing nuclear weapon materials, Draft. - Moscow, VNIIKhT, 1994.

7.14. The Cadastre of sites for storage and disposal of radioactive wastes, The Minatom of Russia. Moscow, VNIIKhT, 1994.

7.15. Advertisement prospect for the SCC 40-th anniversary (after the materials of the "Novoye Vremya" weekly), the "Expres SV" firm, 1993.

7.16. O.L.Kedrovskii, A.I.Rybal’chenko, M.K.Pimenov et.al. "The deep burial of liquid radioactive wastes into porous geological formations", Atom. Ener., 1991, v. 70, No. 5, p. 298-303.

7.17. A.I.Rybal’chenko, M.K.Pimenov, P.P.Kostin et.al, The deep burial of liquid radioactive wastes, Moscow: IzdAT, 1994, 256 pp.

7.18. K.P.Makhon’ko, L.N.Pavlova, V.P.Martynenko et.al, "The estimation of the Siberian Chemical Combine effect on radioactive contamination of the environment in 1989-1994", Atom. Energ., 1996, v. 80, No. 3.

7.19. V.F.Men’shchikov, Information of the RF Security Council Working Group on the results of examination of ensuring radiation and environmental safety of the SCC and adjacent territories, 1994.

7.20. A.I.Malyshkin, G.P.Belousov, S.I.Bushuev, "The radiation situation in the SCC area". - Paper, presented at the Second International Radioecological Conference After the Cold War: Disarmament, Conversion and Security, Krasnoyarsk, 12-16 September, 1994.

7.21. A.I.Malyshkin, G.P.Belousov, S.I.Bushuev, "The radiation situation in the SCC area". - Paper, presented at the 3-d International Radioecological Conference The Destiny of Spent Nuclear Fuel: Problems and Reality, Krasnoyarsk, June 22-27, 1996.

7.22. G.V.Vorob’yov, A.M.Dmitriev, A.S.D’yakov, Yu.I.Yershov, D.P.Osanov, L.V.Popova, Collection Plutonium in Russia. Environmental, economical, political aspects of the problem,. Published by the Centre of the Environmental Policy of Russia and the Centre of Nuclear Ecology and Energy Policy of the Social & Environmental Union, Moscow, 1994.

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7.29. Information of the Chelyabinsk Region Administration on radioactive contamination of soils of the Northern part of the Chelyabinsk Region, as of 1993.