Mayak Chemical Combine is located near Ozersk, a closed city in the Southern Urals. Until 1992 the city was known only by its post office box number Chelyabinsk-65, and prior to 1990, as Chelyabinsk 40. The city is situated approximately 15 km east of the city of Kyshtym and about 70 km north of Chelyabinsk, a city with a population of about one million people in the Asian part of Russia. The reactor area is located about 10 km from Ozersk, a city with a population of 85 600.  Construction of the Mayak Chemical Combine (MCC) began in November 1945, and the first reactor became operational in June 1948. Seventy thousand inmates from 12 different work camps laboured in the construction of Mayak's different facilities. The complex itself covers an area of approximately 90 km2.  and employs 17 100 people.
Chelyabinsk county covers an area of 88 500 km2 and has a population of 3 636 800. Of those residents, 82% live in towns. There are over 3 000 inland lakes within the county and the water flow of the largest rivers is controlled by dams. The county is rich in natural resources and there is mining for iron, magnetite and gold. Chelyabinsk County ranks sixth in Russian industrial production. In 1990 Chelyabinsk consumed 6 720 MW of electricity, and according to Russian prognoses, this figure is expected to increase to 7 500 MW by the year 2005.
Map 2: The area surrounding Mayak Chemical Combine
There used to be six operational reactors at Mayak Chemical Combine (MCC) for the production of weapons plutonium. Of these, five were graphite-moderated  while the sixth was originally a heavy water reactor. These reactors have now been shut down. The heavy water reactor was later modified to a light water reactor which remains in operation today. An additional light water reactor produces isotopes for civilian use. There is a reprocessing facility (RT-1) in use at Mayak, a vitrification facility for liquid waste and about 100 storage tanks containing high level radioactive waste.
The five water-cooled, graphite-moderated reactors at the Mayak Chemical Combine are located at two separate areas along the south-eastern bank of Lake Kyzyltash. All of the production reactors utilise an open cooling cycle whereby water from the lake is pumped directly through the reactor core and out again into the lakes. The temperature of the discharge water was about 70ºC. The A, IR and AV-1 reactors are located at Plant 156, whereas the AV-2 and AV-3 reactors are located in a different area within the complex.
The first reactor, the A reactor, was a graphite-moderated production reactor. It had 1 168 channels with natural uranium enclosed within vertical aluminium tubes, and these were designed to operate at 100 MWt, but this thermal effect was later upgraded to 500 MWt. The core was 9.2 m high and 9.4 m in diameter. The top of the reactor was 9.3 m beneath the ground. Cement walls 3 m thick were built around the reactor, and these in turn were surrounded by large water tanks. The reactor was completed in 1948, only 18 months after the initial start of construction.
The reactor was loaded with all the available uranium in the Soviet Union and began operation on June 19, 1948. The plutonium produced here was used in the first Soviet atom bomb which was tested at Semipalatinsk on August 29, 1949. The reactor was operational for 39 years, and was finally shut down in 1987. It is housed in Building 1 at Plant 156.
The dismantling of the reactor is being carried out in three stages. During the first stage, the reactor was shut down and its fuel unloaded. The second stage, which is now in progress, entails the removal of the control and operating systems and filling the remaining empty spaces with cement. This procedure is expected to take about five years. The final stage, which is expected to take 20 to 25 years, will be a 'waiting period' until a decision is made to either bury the reactor on site or remove it altogether.
The IR reactor was used for the production of plutonium and to test the fuel of both the A-reactor and the RBMK reactors. Housed inside Building 701 near the A-reactor, the IR-reactor is a small graphite-moderated 65 MWt reactor with 248 channels. Construction of the reactor began on August 15, 1950, and it became operational December 22, 1951. The reactor was shut down after 36 years of operation on May 24, 1987.
The three large graphite-moderated production reactors AV-1, AV-2, and AV-3 probably all share the same design. Each has 2 001 channels. Of the three reactors, only the AV-2 reactor has been described in openly available literature. The core of the AV-2 reactor consists of a vertical cylinder 7.6 m high and 11.8 m in diameter. Radiological shielding is provided in that the active zone is protected by three layers. The first layer consists of sand and water 1.5 m thick and a 2 m thick concrete wall. On top of this is a 1.5 m thick layer consisting of a mixture of sand and bathite ore covered by a further layer of concrete 3 m thick. Finally there is a pool of water 1.5 m deep.
AV-1 went into operation in 1955  and was shut down on August 12, 1989; AV-2 came on line in April 1951 and shut down in July 1990. AV-3 started up on September 15, 1952, and ceased operations on November 1, 1990. The AV-3 reactor is housed in Building 501 at Plant 156, and was the last of the five graphite reactors to be shut down.
The second reactor to be started at Mayak Chemical Combine was a heavy water moderated reactor known as "Ruslan".  This reactor went into operation some time between the end of 1948 and 1951, and was active until about 1980. Towards the end of the 1980s, it was rebuilt to a light water reactor with a capacity of 1 000 MW. "Ruslan" is used to produce tritium for the Soviet hydrogen bombs and specific isotopes such as 238Pu.
Another type of reactor which is still in use at Mayak is a light water reactor called "Lyudmila".  Its power is 1 000 MW and this reactor is also used for the production of tritium and various other isotopes, including 238Pu.
Between the five graphite-moderated reactors at Mayak, a total of 58.3 tonnes of plutonium has been produced. Up until the end of 1992, the two remaining reactors are believed to have produced 14.7 tonnes, for a total plutonium production at Mayak Chemical Combine of 73 tonnes.
Six months after the start-up of the A-reactor in December 1948, the first of at least three reprocessing facilities to be built at Mayak Chemical Combine began operation. The facility was in use until 1961 when it was decommissioned.
A second plant, the radiochemical facility RT-1, became operational in 1956 and is still in use. It was originally intended to reprocess weapons grade plutonium generated by the spent nuclear fuel from the five production reactors. In 1976 the facility was modified to reprocess civilian plutonium based on spent nuclear fuel from reactors on board submarines and icebreakers, research reactors, liquid metal-cooled fast breeder reactors (BN-30 and BN-600) and from the first and second generation Soviet pressurised water reactors (VVER-440).  Furthermore, countries in Eastern Europe and Finland also send spent nuclear fuel from their own Soviet/Russian-built pressurised water reactors to this facility.
The principal purpose of the modifications to the RT-1 plant was to permit the reprocessing of stainless steel or zirconium-clad nuclear fuel, as is typical of such reactors. Since the plant's modification in 1976, spent nuclear fuel from military production reactors has been transported by train to the reprocessing facility in Seversk (See Chapter 2.2.2).
The RT-1 facility has an annual capacity of 400 tonnes, or 300-900 fuel assemblies. The technology used here is a continual process whereby 99% the uranium and plutonium contents are extracted using tributyl phosphate. As of 1992, there were 2 500 employees at the plant. The reprocessing of one tonne of fuel results in 45 m3 of high level waste, 150 m3 of medium level waste and 2000 m3 of low level liquid waste. The process also leads to a further 7 500 kg of solid radioactive waste.[ 12]
In the period between 1976 and 1991 an average of about 200 tonnes of spent fuel were reprocessed per year. Since 1991 the amount of reprocessed spent fuel has decreased, in part due to the difficulties in importing spent fuel from the CIS countries Azerbaijan and Ukraine, and from the East European countries Bulgaria, Hungary and the Czech Republic. In 1995 Finland decided that from 1966 and onward, it would cease forwarding its spent fuel from the Lovisa power plant for reprocessing. In 1992, Finland was reported to have had 120 tonnes of fuel reprocessed. This corresponds to an annual production of one tonne of reactor grade plutonium.
The composition of reactor grade plutonium from light water reactor fuel is presented in Table 2. It has a burn-out rate of 33 000 MWd/tonne. At this rate of burn-out, the contents of 235U are decreased from 3.6% to 1.2%
-------------------- Isotope Contents(%) -------------------- 238Pu 1,4 239Pu 56,5 240Pu 11,28 241Pu 2,95 242Pu 1,42 --------------------Table 2. Composition of plutonium in spent fuel from a VVER reactor.[ 13]
At first it was thought that the recovered low-enriched uranium (LEU) could be used immediately as fuel in the RBMK reactors without further enrichment. However, due to the higher burn-out of VVER fuel and the fact that the RBMK reactors require a higher enrichment than was originally thought, the recovered fuel must be enriched in 235U from 0.8-1.25% and up to 2.4%.
The civilian plutonium that was processed after 1976 was originally intended to be used as fuel in the breeder reactors. However, due to serious delays in MinAtom's breeder reactor programme, the plutonium-dioxide (PuO2) is currently being placed in temporary storage. As of 1992, 25 tonnes of reactor grade plutonium had been stored.  Assuming a production rate of one tonne per year, one may infer that by 1995, there were about 27 tonnes of reactor grade plutonium in storage.
A vitrification facility for liquid radioactive waste has been in operation since 1987. This facility has a capacity of 500 l/h and transforms the radioactive waste into phosphate glass. The first ceramic smelter ran for only 13 months before the electrodes were destroyed by their very high electrical current (2 000 A). Vitrification of liquid radioactive waste was resumed on June 25, 1991, after a new smelter had been built.
The processed glass is placed into stainless steel containers (0.6 m in diameter and 3.4 m in height) which are stored in groups of three in surface storage facilities containing air cooling systems. At the present time, there are just under 4 000 such containers stored at Mayak Chemical Combine.  The containers will be stored for 20 to 30 years until a permanent underground site has been built for them.
By the beginning of 1995, 8 100 PBq (218 MCi) had been vitrified, taken out of liquid waste measuring 8 500m3 in volume. The vitrified waste weighed approximately 1 600 tonnes..  The facility has vitrified on average approximately 1 850 PBq/y (50 MCi/y) in the five years that it has been in operation. Nowadays, all high level liquid waste is vitrified.  The liquid waste that undergoes vitrification has a concentration of 10 TBq/l (400 Ci/l).
There used to be a number of production facilities at Mayak for the fabrication of MOX fuel (a mix of uranium and plutonium). Of the five MOX fabrication facilities, two have been shut down, two continue to operate and construction on the fifth has been halted for the present.
The first pilot facility operated during the 1960s and 1970s, and used approximately one tonne of weapons grade plutonium to produce test fuel assemblies for the fast research reactors. Between 1986 and 1987, there was a small facility in operation to produce MOX fuel for fast reactors of the BN type. It had a capacity of 35 kg of weapons grade plutonium a year (5 assemblies per year).
Since 1988, another facility has been producing MOX fuel for trial in the fast reactors. Its capacity is 70-80 kg of weapons grade plutonium a year, or 10 fuel assemblies per year. In 1993, the Obinsk Atomic Research Institute just outside Moscow carried out a trial using 150 kg of MOX fuel in a fast reactor.
Construction had also begun on a MOX fuel fabrication facility, but work was suspended when the plant was 50 to 70% complete. The plant was intended to produce fuel for three planned breeder reactors in the South Urals Project at a capacity of 5 to 6 tonnes of plutonium a year. Plans for this facility also included the production of MOX fuel assemblies for VVER reactors.
Construction of the Ushno-Uralskaya Power Station began in 1984. Located one kilometre from the water reservoirs in Mayak, it was known as the South Urals Project. Originally it was supposed to consist of three BN-800 type liquid metal fast breeder reactors (800 MWe). Water to cool the reactors was to be drawn from the reservoirs containing radioactive waste (see section 1.4.1). Not only would the reactors supply the Chelyabinsk region with electricity, but they would also evaporate some of the water in the reservoirs and thereby avert flooding. When the project was halted in 1987, concrete footings had been laid for only two of the reactors. The project suffered both from economic difficulties and strong opposition at the local political level, and these obstacles, when coupled with resistance from the authorities of Chelyabinsk County, were enough to block further construction.  Nevertheless, in 1992 MinAtom disregarded the local resolution against the project and appropriated funds to resume construction.  However, the funds earmarked for the project were consumed by inflation and were never actually transferred. The project has not been further resumed.
In the period 1949 to 1956, controlled amounts of liquid radioactive waste from Mayak Chemical Combine (MCC) were discharged into the river Techa. The continued operation of the reprocessing facility leads to further routine discharges to the environment. In two major accidents at the facility, large amounts of radioactivity were released. There have also been a number of other accidents of varying severity at the facilities. An area totalling 26 700 km2 has been contaminated with a total activity of 185 PBq (5 MCi). An estimated radioactivity of 5 500 PBq (150 MCi) has been released to the environment, of which 4 400 PBq (120 MCi) went to Lake Karachay.
Following the development of more simplified techniques for the handling of liquid radioactive waste from reprocessing plants, and the concept of dilution as a principal method of disposing of such waste, large amounts of medium and high level liquid radioactive waste were discharged into the Techa River approximately 6 km from its source. [ 23] Over 95% of the waste was released into the river in the period between March 1950 and November 1951 as a consequence of insufficient purification techniques.  After November 1951, high level waste was dumped into Lake Karachay instead, and this practice was continued until 1953 when a temporary storage facility was constructed. However, low and medium level waste continues to be dumped into the lake.
Approximately 76 million m3 of liquid radioactive waste with a total beta activity of 100 PBq (2.75 MCi) has been discharged into the Techa River.  The waste is mainly a mixture of strontium, caesium, niobium, and ruthenium. About 25% of the activity consists of 90Sr and 137Cs.
About 124 000 people were exposed to higher levels of radiation as a result of these discharges.  The population living along the river banks of the Techa felt the greatest impact. Here the levels of radiation were so high that 28 000 residents received medically significant doses. From 1953 onwards, the river could no longer be used as a source of drinking water, and in the years up to 1960, 7500 residents were evacuated from their villages along the riverside.  Barbed-wire fences were erected on both sides of the Techa River and it was prohibited to fetch water or to fish. Yet the area residents were never apprised of the fact that the river had been contaminated by radiation: subsequently they tended to disregard the bans.[ 30]
Certain villages alongside the river were evacuated while the inhabitants of certain others remained. Those residents who were evacuated had received effective radiation doses in the range of 0.35 Sv to 17 Sv, with the largest doses having been received by the 1 200 inhabitants of the village Metlino. The bulk of the dose was received during the first few years.
Of the remaining groups in the area who had not been evacuated, it was the residents of Muslyomovo who were the most exposed. Muslyomovo is situated 30 km downstream of Mayak Chemical Combine, and in 1949 it had a population of 4 000 inhabitants. By 1990, the number had fallen to 2 500 residents.  The effective dose received by Muslyomovo's villagers is approximately 2.8 Sv, and the effective dose received by children is 0.05 to 0.1 Sv/y.  The residents of Muslyomovo are mainly Tartars, and in the years since 1950, they have been subject to compulsory blood and bone marrow testing. The results and findings from these tests however, were kept secret until 1992.  In 1993, the administration of Chelyabinsk County passed a resolution to evacuate Muslyomovo and to build a new village for the residents further away from the Techa River; however, as a result of economic problems, the resolution never materialised. 
In an attempt to limit the transport of radioactive materials further north in the river system, a number of dams were built along the Techa River. These dams formed a cascade of reservoirs whose objective was to reduce the speed of the water to a slow, quiet flow such that radioactive particles would be deposited to the sediments rather than being transported downstream further into the river system. One of the dams was built in the middle of Muslyomovo which straddles both sides of the river. The dam opened in 1968, and areas on both sides of the river that had previously been below water level were taken into agricultural use. There are considerably higher levels of contamination above the former dam than in areas that lie below it.  Sediment samples taken from the river banks above the dam indicate activities of 400 000 Bq of 137Cs per kilogram of soil, and 120 000 Bq of 90Sr per kilogram of grass.  Nevertheless, farm animals continue to graze in this area.
The contamination measurements for the upper part of the river are now 740 GBq/km2 (20 Ci/km2) of 90Sr and 5920 GBq/km2 (160 Ci/km2) of 137Cs.
In the early 1950s, the dumping of high level waste into the Techa River ceased. By this time, a number of underground steel storage tanks equipped with cooling systems had been built to store this waste. In 1953, the facility was taken into use. Each tank has a volume of 300 m3 and is placed into an underground bunker with concrete walls 1.5 m thick. Each bunker can store up to 20 storage tanks, and these are installed into the bunker at a depth of 8.2 m below the ground surface. Much of the liquid waste stored in these tanks contain nitric acid from reprocessing procedures.
Due to the failure of a cooling pipe in one of the tanks, the cooling fluids began to evaporate. This led to the overheating of the tank (350 ºC) and the resulting explosion on September 29, 1957, at 16:20 local time. The force of the explosion corresponded to 75 tonnes of TNT such that the 2.5 m thick concrete lid was hurled 25 to 30 m away.  The total release of radioactivity was 740 PBq (20 MCi), and of this, 90% of the radionuclides (666 PBq) were spread over a small area near the tank. About 74 PBq (2 MCi) of the total activity was swept up to a height of one kilometre, leading to the radioactive contamination of certain parts of Chelyabinsk, Sverdlovsk and Tyumen counties.[ 39]
The most important of the long-lived isotopes present in the ensuing fallout from the Kyshtym accident was 90Sr. This radionuclide accounted for approximately 5.4% of the fallout, or 4 PBq (108 000 Ci). (As a point of comparison, the discharge of 90Sr after the Chernobyl accident was 8 PBq (216 000 Ci.)). There was very little 137Cs in the tank - only about 0.036%. This may have been due to the fact that much of the waste had been pumped out into Lake Karachay in order to make room for more liquid waste in the storage tanks. Most of the remaining radionuclides released in the accident were readily adsorbed to the sediments and lay at the bottom of the tank. However, this tendency towards adsorption was not true of 137Cs which remained in liquid form.  An overview of the composition of the different isotopes that were present in the ejected waste from the tank is given in Table 3.
------------------------------------------------------------- Isotope Contribution to Total Half-life Activity of Solution(%) ------------------------------------------------------------- 89Sr traces 51 d. 90Sr + 90Y 5,4 28,6 y. 95Zr + 95Nb 24,9 65 d. 106Ru + 106Rh 3,7 1 y. 137Cs 0,036 30 y. 144Ce + 144Pr 66 284 d. 147Pm traces 2.6 y. 155Eu traces 5 y. 239,240Pu traces -------------------------------------------------------------Table 3. Composition of radioactive isotopes in ejected waste from the Kyshtym accident.
One area north of Mayak with a population of 270 000 and an area of 23 000 km2 measuring 300 km long and 3 to 50 km wide was contaminated by a 90Sr concentration of more than 3.7 GBq/km2 (0.1 Ci/km2).  One district with a population of 10 000 and an area of 1 000 km2 was contaminated by a 90Sr activity of more than 74 GBq/km2 (2 Ci/km2). This concentration level was also selected as the criterion for the safety of the inhabitants.  The contaminated region is 105 km in length and 8-9 km in breadth, and is also known as the East Urals Radioactive Trace.  (See map 3 below).
Following the Kyshtym accident, the hospitals and clinics of Chelyabinsk county were filled to capacity with thousands of people whose condition was being monitored for the first 1-2 years after the explosion.  At least 200 people died as a result of radiation sickness in the years following the accident.  Agricultural production in the area was also affected. In 1958, 106 000 ha (100 hectares = 1 square kilometre) of agricultural land were laid fallow in Chelyabinsk and Sverdlovsk counties.  By 1961, all agricultural areas in Sverdlovsk had been returned to cultivation, whereas in Chelyabinsk county, an area of 40 000 ha could not be farmed again until 1978. However, there are some remaining areas totalling 180 km2 in which the farm land still cannot be used because of this accident.
Map 3: The East Urals Radioactive Trace. The 90Sr contamination are shown in Ci/km2
In the fall and winter of 1957-1958, food supplies in the Mayak region became contaminated. Varying levels of radioactivity from 6.3 GBq/kg to 2 600 GBq/kg (0.17-70 Ci/kg) were detected in agricultural products up to 20 km from the site of the accident.
In areas where the activity of 90Sr was more than 74 GBq/km2 (2 Ci/km2), the largest source of radiation intake for the inhabitants was in the form of contaminated dairy products. This was especially true in the more agricultural areas, and children in particular were at the greatest risk. In 1966-1967, the average radiation doses sustained by the critical groups as a result of 90Sr intake was measured at 16.3 mSv/year for children (ages 7 to 9). The village Sherbakovo was the village most seriously affected by the accident, with an annual dose of 26.3 mSv/year. The average dose was approximately 3 mSv/year for adults and 10 mSv/year for children.
A total of 10 200 people were evacuated from their homes following the Kyshtym accident. Those living in the most exposed areas were evacuated 7-10 days after the explosion, while the last group of residents was not moved until two years later. Some of the most contaminated areas were not evacuated until 10 days had elapsed, and this resulted in the inhabitants receiving doses of approximately 0.52 Sv over that time period.
In general, people were evacuated from those areas where the concentration of 90Sr was from 18 000 GBq/km2 (500 Ci/km2) to 122 GBq/km2 (3.3 Ci/km2). Evacuated villages were then burned to the ground and the top layer of soil scraped away. The residents of these areas sustained a collective effective dose of 1 300 manSv. In some of the more populated districts (10 700 inhabitants), the concentration of 90Sr was between 37-148 GBq/km2 (1- 4 Ci/km2). These residents were exposed to a collective dose of 4 500 manSv. By 1990, 90Sr accounted for 99.3% of the remaining contamination from the 1957 accident.  The Kyshtym accident is rated 6 out of a maximum 7 in degree of severity on the INES scale  (International Nuclear Event Scale).
When it became clear that discharging liquid radioactive waste into the river led to increased contamination of the entire river system, MCC then began to dump its liquid waste into the closed water system of Lake Karachay instead. However, the years 1962-1966 were years of relatively low precipitation and the corresponding run-off into the lake was very low. In the spring of 1967, part of Lake Karachay evaporated and 5 ha of land that had formerly lain underwater, became exposed.  Unusually strong winds swept up radioactive particles from the lake sediments and spread them over an area of 1 800 km2. The transported radionuclides were mainly 137Cs and 90Sr, with an estimated total activity of 22 TBq (600 Ci). In one particular area where the activity of 90Sr and 137Cs was3,7 GBq/km2 (0.1 Ci/km2) and (0.3 Ci/km2), respectively, there was a population of 40 000 inhabitants.  Many of the same areas that had been affected in the 1957 Kyshtym accident were impacted again ten years later.
The inhabitants of the areas most contaminated by the radioactivity spread from Lake Karachay received an effective dose of 130 mSv, while the residents of lesser impacted areas received doses of 70 mSv each.
All in all, the three accidents described above, along with discharges from routine operations, contaminated a total area of approximately 26 000 km2 with a total radioactivity of 185 PBq (5 MCi).  Approximately 500 000 people have been subjected to increased levels of radiation, and of these, 180 000 were evacuated.  The total radiation exposure from the three accidents is estimated to be 12 000 manSv.
Construction of an enrichment facility for natural thorium (Plant 5) began in 1949 near the town of Ozernyy. The town has a population of 1 370, including 500 children. Thorium enrichment was halted in 1964.
In 1968, it came out that the enrichment facility had dumped radioactive sand and clay waste directly out into the environs surrounding Ozernyy without any kind of protective shielding or covering. Furthermore, some contaminated equipment had been buried near the plant. At the present time, there are 70 spots in and around Ozernyy that have been contaminated by radiation. Furthermore, due to the use of thorium-contaminated sand for building material, there are also 36 houses in which the levels of radiation are between 50-500 *R/hour. High levels of radon and thoron have also been detected in the air.
While the most serious accident involving the reprocessing of plutonium was the 1957 Kyshtym accident, there have also been other problems in connection with the Mayak reprocessing plants. On April 21, 1957, approximately six months prior to the Kyshtym accident, a self-sustaining chain reaction took place in a highly enriched uranium-nitrate solution. Six people were injured, but no areas outside the immediate compound were contaminated. The incident was rated 4 on the INES scale.
On October 2, 1958, another self-sustaining chain reaction occurred at the reprocessing facility, this time during experimental work to determine the critical parameters of the dissolution of highly concentrated uranium nitrates. The accident was attributed to staff incompetence, and resulted in exposure of the team to radiation. The accident rated 4 on the INES scale.
Ten years later, a self-sustaining chain reaction occurred at the reprocessing area for metallic plutonium. The accident was caused by breaches in the codes and requirements for radiation safety, and it resulted in the injury of two people. This accident also ranked 4 on the INES scale.
On February 11, 1976, a container holding complex fluids generated in plutonium extraction procedures exploded at the facility. This accident was also caused by the errors of insufficiently qualified personnel. Large areas of the plant were destroyed, and the work shop areaalong with adjacent areas of the facility were contaminated. There were no injuries to the personnel, however. The accident was classified 3 on the INES scale.
Throughout the 40 years that Mayak Chemical Combine has been in operation, approximately 10 000 workers have suffered from some form of radiation sickness. Most of the illnesses occurred during the Combine's first years of production. Four thousand people have died due to radiation sickness; the average dose received by this group was 2 Sv.
Intrinsic to the reprocessing of plutonium is the release of radioactive isotopes to the air. Given the facility's yearly production capacity of 120 tonnes, it has been estimated that 24 TBq (660 Ci) of tritium (3H), 1.5 TBq (40 Ci) of 14C, and 30 000 TBq (810 000 Ci) of 85Kr are released to the air annually.
The operation of the different facilities at Mayak Chemical Combine has led to the generation of large amounts of radioactive waste. This is particularly true of the reprocessing plants and of the military production reactors. Much of the waste is high level liquid waste containing 99% of the fission products from spent nuclear fuel and about 10% of the total contents of neptunium. The accumulated waste at Mayak totals approximately 37 million TBq (1 GCi).
At the beginning of the 1990s, the annual production of long-lived radioactive waste was 3 million TBq (90 MCi), including 37 000 TBq (1 MCi) of medium level waste (MLW) and 222 TBq (6 KCi) of low level waste (LLW).
--------------------------------------------------------------------------- Category Liquid Waste Solid Waste* --------------------------------------------------------------------------- Low Level <3,7MBq/l (<10-5 Ci/l) <3 mikroSv/t (<0,3 mrem/t) Medium Level >3,7 MBq/l - 37 GBq/l (>10-5 Ci/l - 1 Ci/l) >3 - 100 mikroSv/t (>0,3 - 10 mrem/t) High Level >37 GBq/l (>1 Ci/l) >100 mirkoSv/t (>10 mrem/t) ---------------------------------------------------------------------------Table 4. Russian Classification of Radioactive Waste. * Measurements taken 10 cm from the surface
From 1949 until November, 1951, all liquid waste from reprocessing activities were discharged into the Techa River. (See section 1.3.1.). Since these discharges led to the contamination of large areas, the most highly radioactive waste was dumped into Lake Karachay instead. The waste was discharged directly into the lake until 1953 when a temporary storage facility was taken into use; however, low and medium level waste still continue to be dumped into the lake.
High level liquid waste from Mayak Chemical Combine's reprocessing activity is placed into approximately 100 different containers. There are 20 stainless steel tanks with single walls, each with a capacity of 300 m3. There are two buildings in which altogether 20 concrete containers have been built, each with a total volume of 1 100 m3. Sediments originating from the high level liquid waste are stored here. There are an additional 61 tanks where waste containing nitric acid and organic materials are stored. All liquid waste produced today is vitrified.
In 1991, the total radioactivity in the storage tanks was 30 million TBq (823 MCi).  The total volume is between 20 000 m3 and 30 000 m3.  Part of the stored high level waste has also been vitrified. In 1993, 2.5 million TBq (67 MCi) of stored waste was vitrified.
Due to routine discharges and the spreading of radioactive materials following accidents, large parts of the river system have been contaminated. Subsequently, in an effort to contain any further spreading of radioactive materials, a number of artificial reservoirs were built along the river Techa. These reservoirs hold large amounts of radioactivity.
The Techa River is 240 km long, and discharges into the river Iset at Dalmatovo. The Iset in turn discharges into the river Tobol in Tyumen county. The river system is approximately 1 000 km in length. The Tobol river joins with the river Irtysh which in turn flows into the river Ob. The Ob drains into the Kara Sea.
The first reservoir (Reservoir 3) was formed in 1951 by the building of a dam just below Lake Kyzyltash (Reservoir 2). Additional dams were built down the Techa River in the years 1956 (Reservoir 10), 1963 and 1964, as shown on the map. Altogether, Reservoirs 2, 3, 4, 10, and 11 form an area measuring 84 km2 and a volume of 394 million m3. The activity levels of 137Cs and 90Sr in these reservoirs have been measured at 7.141 TBq (193 kCi) altogether. A canal system has been built around the reservoir to prevent any further influx of water or flooding. The canal system on the left bank of the river was built in 1963, and the system on the right in 1972.
Over the course of time that the reservoirs have been in use, the water level in the river system has increased. Over the last 15 years, it has risen by 3 m, and now lies 30-40 cm below the maximum permitted level of 206.5 m. Should the water level continue to increase at its present rate, it will reach the maximum permitted level in 2-3 years.
Map 4: The water reservoirs
In 1951, Mayak Chemical Combine began to discharge its radioactive liquid waste into Lake Karachay (Reservoir 9), a closed water system. The practice of discharging all liquid waste into the lake, high level waste included, was continued until the end of 1953. Once the temporary storage facility for high level waste was opened in 1953, only medium and low level waste was then dumped into the lake. As of the present, Lake Karachay has an accumulated total of 4 400 PBq (120 MCi of long lived isotopes, 3 626 PBq (98 MCi) of 137Cs and 740 PBq (20 MCi) of 90Sr respectively.
The two radionuclides most commonly present in liquid waste from the reprocessing of plutonium and uranium are 90Sr and 137Cs, in roughly equal amounts. The relatively large fraction of caesium found in Lake Karachay is explained by the fact that much of the liquid waste was stored in steel tanks prior to its being discharged. The short-lived particles disintegrate, whereas the long- lived radionuclide 90Sr will sink to the bottom. This is not true however, of 137Cs which readily dissolves in the liquid waste and is discharged with it into Lake Karachay. The practice of dumping this waste into Lake Karachay has probably been in effect for many years. In 1990, it was stated that about 44 000 TBq/year (1.2 MCi/year) were dumped into the lake. In early 1995, the management of Mayak Chemical Combine announced that on an annual basis, the facility had dumped 16 000-20 000 m3 of medium level waste into Lake Karachay with a collected activity of 37 000 TBq (1 MCi).
When the evaporation of Lake Karachay in 1967 led to the contamination of large areas, measures were taken to prevent a reoccurrence. Firstly, from 1967- 1971, the open areas were filled with sand, and the stone dikes around the lake were reinforced. In the years 1978-1986, the lake was filled with hollow concrete blocks to prevent the sediments from shifting. The blocks are 1 m long and open at the top. They were lowered into the water and then filled with earth and stones. A total of 9 444 blocks have been filled in Lake Karachay totalling 1 272 m3 in volume. New dikes were built in the period from 1988-1990 to divide the lake. By the end of 1993, the area of Lake Karachay had been reduced to 15 ha.[ 76]
Photo 1: Lake Karatsjaj
The continued discharging of radioactive waste into Lake Karachay has also resulted in the contamination of the ground water. This ground water lies in a lens-shaped area of 10 km2, and is almost 100 m deep.  The pattern of contamination follows the flow of the ground water, and is spreading mostly in a north to north easterly direction towards Reservoirs 2 and 3. To the south, it drains towards the River Mishelyak. A total volume of over 5 million m3 of ground water is estimated to have been contaminated.  It has been affected down to a depth of 100 m, and activity levels have been measured at well over 185 TBq (5 000 Ci). The contaminants move at a speed of 84 m/year for 90Sr and 51 m/year for 60Co.
Staroe Boloto (Reservoir 17) is a closed water system that lies approximately 5 km north-east of Lake Karachay. It was formed by the building of an earthen dam in 1949 and has a volume of 35 000 m3 and a surface of 0.17 km2. It is still used as a discharge reservoir for medium level waste. By 1990, it had accumulated a total radioactivity of 74 000 TBq (2 MCi), mainly in the sediments.
-------------------------------------------------------------------------------- Reservoir Capacity Accumulation in Accumulation in Total No. (million m3) reservoir(Ci) sediments(Ci) Accumulation(Ci) -------------------------------------------------------------------------------- 2 83 2.000 18.000 20.000 3 0,75 2.600 15.400 18.000 4 4,1 1.700 4.200 6.000 6 17,5 2 300 300 9 0,4 8.400.000 110.000.000 120.000.000 10 76 50.000 60.000 110.000 11 217 24.000 15.000 39.000 17 0,8 45.000 2.000.000 2.000.000 Totalt 399,6 8.525.300 112.112.900 122.193.300 --------------------------------------------------------------------------------Table 5 Overview of the Reservoirs
Approximately 500 000 tonnes of solid waste have been produced from the Mayak facilities. About 25 000 tonnes of this are high level waste, 300 000 tonnes are medium level and 150 000 are low level.  In recent years, the production of solid radioactive waste has slowed; at the present time, between 2 and 2.5 tonnes/year are produced. The solid waste is buried at 227 different places. High level waste with a total activity of 481 000 TBq (13 MCi) is permanently stored in 24 underground structures.  Low level and medium level waste, with a collective activity of 1 110 TBq (30 kCi) is buried in 203 trenches, and the trenches are then covered by a layer of clay. Radioactive waste continues to be buried at 30 special sites.