The two RBMK reactors in Seversk in Siberia. (Same as Chernobyl)
The two RBMK reactors in Seversk in Siberia. (Same as Chernobyl)
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Map 5: The radioactive fallout after the accident in Seversk April 1993.
Measurements in mikroR/h.
Seversk is located in Siberia, approximately 15 km north-west of Tomsk and 3 000 km east of Moscow. It is one of Russia's closed cities, and until 1993, was known only by the name Tomsk-7 (a post office box number). Around the city is a buffer zone of 192 km2 closed in by triple barbed wire fences. The city is situated beside the River Tom, a tributary of the River Ob, and has a population of 107 000 . (See the map).
There are two roads that lead to Seversk, and both are guarded by military checkpoints. The main entrance is located at the south end of the enclosed area on the main road between Tomsk and Seversk. Here there are six gates where cars and residents on their way into the town are checked and cleared. Each of the city's residents has a special passport which must be shown at the checkpoints to the town. At the northern end of Seversk there is a smaller road with two gates. The town itself is easily visible from the Tom River which is openly accessible to anyone. Construction of the atomic facilities and Seversk itself began in 1949, and the Siberian Chemical Combine was founded in 1954. The nuclear reactors and production facilities are located 15 km west of the actual civic area in Seversk (56º27' N 84º47' E).
The Siberian Chemical Combine (Sibkhimkombinat) consists of five military production reactors, a chemical separation plant, a reprocessing facility for uranium and plutonium, a uranium enrichment plant, and storage facilities for radioactive waste. There is also a facility to store retired warheads. As of 1993, there were 15 000 employees at the Siberian Chemical Combine.
Originally there were five reactors at the Siberian Chemical Combine producing weapons grade material. Only one is still in use today. The first reactor (I-1) operated from November 20, 1955 until August 21, 1990; the second (I-2) from September 1958 to December 31, 1990, and the third, (AD-3), from July 14, 1961 to August 14, 1992. All three of the shut-down reactors are located at "Object-5". The two reactors that remain in operation, (AD-4 and AD-5) started up in 1965 and 1967, respectively, and these reactors are located at "Object-45", not far from the radiochemical plant. These two reactors are due to be shut down in 1995.
The first reactor (I-1) had an open cooling system; subsequently, its cooling water was discharged directly into the Chernilshikov River, a two kilometre long tributary of the River Tom. In 1990, gamma radiation was measured here that was higher then the natural background radiation. (See section 2.4.1.).
Of the five nuclear reactors at the Combine, all except the first one were "dual-purpose" reactors, that is, they produced heat and electricity as well as plutonium. Four of them were graphite-moderated, water-cooled reactors, sharing the same basic design as the RBMK reactors. The RBMK reactor is used at civilian power plants such as Chernobyl, Leningradskaya (Sosnovy Bor), and Ignalina.
Most of the production reactors probably had 2101 channels, and they were somewhat larger than the reactors used for the production of plutonium at Mayak. The five reactors at Seversk were cooled by water taken from the River Chernilshikov. All except the first one were equipped with closed circuit cooling systems whereby the heat from the primary loop is transferred to the secondary cooling loop by means of heat exchangers. This hot coolant is used to heat the city of Seversk, and part of it is transported via pipelines to heat houses in Tomsk. The reactors are also used to produce electricity for the two cities.
The chemical separation plant ("Object 15") at the Siberian Chemical Combine manufactures plutonium, mostly 239Pu. The facility was most probably first taken into use shortly after the first reactor became operational in 1956. There is a special train for the employees of this facility from Seversk to the plant.
Plutonium is manufactured by dissolving irradiated uranium fuel from nuclear reactors in a nitric acid solution once the cladding has been removed. The aqueous solution with the nitric acid contain fission product nitrates (mostly 137Cs and 90Sr, uranium nitrate and plutonium nitrate). This is scrubbed in an organic solvent consisting of tributyl phosphate and petroleum. In the first treatment, intensely radioactive fission products are separated from the rest of the solution containing uranium and plutonium. The next step in the procedure separates the uranium from the plutonium. Once the separation process has taken place, the remaining fission products are either stored or placed in a repository as liquid waste.
Besides manufacturing plutonium from the spent fuel of the reactors at Seversk, the chemical separation plant has also been reprocessing plutonium from the spent fuel of the five military production reactors at Mayak since 1978. This is because in that year, Mayak's own reprocessing facility was modified to be able to accept civilian fuel not only from power plants operating the VVER-440 reactors in particular, but also from civilian nuclear icebreakers, research reactors, and nuclear submarines. Irradiated fuel was therefore transported by train to Seversk for reprocessing until the last military reactor at Mayak was shut down in 1990. Today, only the fuel from the two remaining production reactors in Seversk is reprocessed.
The actual reprocessing of plutonium takes place at Plant 25. Here 239Pu from the reprocessing facility is separated from the spent nuclear fuel (isotope separation) and made into capsules for later use in nuclear warheads. The capsules are placed into containers which are stored at the plant prior to being sent to other facilities in Russia that assemble the warheads. Production facilities for the assembly of nuclear warheads for tactical and strategic nuclear weapons are located in four closed cities: Sverdlovsk-45, Zlatoust-36, Penza-19, and Arzamas-16.
Seversk also has a uranium enrichment facility. In January 1991, the Siberian Chemical Combine (SCC) signed a contract with the French company COGEMA (Compagnie Générale des Matières Nucléaires) such that SCC would accept uranium recovered from reprocessed French nuclear fuel and enrich it up to 4%. The contract is valid for 10 years and includes the enrichment of approximately 500 tonnes of uranium hexafluoride (UF6). The Siberian Chemical Combine would receive 50 million USD for the commission. While France does have a uranium enrichment facility of her own, she uses the enrichment facility at Seversk so as not to contaminate her own facility with the uranium isotopes 232U and 236U.
Over the course of the 30 years that the Siberian Chemical Combine has been in operation, the production of weapons grade plutonium and the enrichment of uranium have resulted in large amounts of radioactive waste. Solid and liquid waste are either stored or placed into permanent repositories at various sites within the enclosed areas of the Combine. There are 50 different storage areas within the borders of SCC to receive the solid and liquid waste generated by the plant's activities. The two forms of waste together have a total activity of 4.6 million TBq (125 MCi). There is also a great deal of liquid waste which has been either deposited down into sandy beds 320-460 m deep or else pumped into open holding pools.
The reprocessing of spent nuclear fuel leads to substantial amounts of liquid radioactive waste and the ensuing problems of disposal and storage. Liquid radioactive waste generated at the Siberian Chemical Combine is partially pumped into two open reservoirs (Reservoirs B1 and B2) and partially pumped down to a depth of 400 m.
There are two open reservoirs in Seversk for the purpose of receiving liquid waste: reservoirs B1 and B2. The area of the two pools is 75 000 m2 altogether. Approximately 150 000 m3 of liquid radioactive waste have been discharged into reservoir B1, and about 130 000 m3 into B2. The practice of discharging liquid waste into these two reservoirs began in the mid 1960s and was halted in 1982. The total activity in the reservoirs today is estimated to be 4.7 million TBq (126 MCi) of long-lived isotopes.
The area surrounding the reservoirs has not been enclosed, and increased levels of radioactivity have been detected in fauna such as moose and hare. Unsafe levels of radiation were detected in 38 individuals, of whom four adults and three children had to be hospitalised.
The problems associated with the levels of radioactivity present in these two reservoirs are similar to the situation at Lake Karachay near Ozersk. The reservoirs are very shallow, and in dry summers, parts of them may evaporate, thereby exposing radioactive particles lodged in the reservoir sediments. These particles may then be swept up and carried by the wind to contaminate the areas around Seversk. Indeed, such a scenario is a strong parallel to what actually did occur at Lake Karachay in 1967. (See Section 1.4.1).
To avoid such a scenario, work was begun in 1991 to cover over reservoir B2. During the winter months, sand is spread over the ice such that when the ice melts in the spring thaw, the radioactive particles are covered by a layer of sand. The goal is to fill in the entire reservoir with sand; however, the intensity of the radiation emitted from the reservoirs is such that specially modified dumping lorries are used where the driver's cab is shielded with iron so as to protect workers from harmful doses of radiation. As of today, half of reservoir B2 has been covered.
During the winter of 1994-1995, work was begun to cover reservoir B1 in the same manner. This project is expected to be completed during the course of 1999. When the two reservoirs are completely covered with sand, concrete or asphalt will then be laid over the entire area. Eighteen bore holes have been drilled around the two reservoirs to access and pump up the contaminated water. This water will then be transferred to an underground repository. However, it is unclear exactly how much of the liquid waste recovered from the reservoirs will be stored underground.
There is an underground repository for liquid radioactive waste 10-20 km away from the River Tom. This facility was taken into use in 1982, and thus far, 33-36 million m3 of liquid radioactive waste have been deposited into the sand layers. Low level waste is pumped down to a depth of 240-290 m, while high level waste is deposited at depths of 310- 340 m. This practice continues into the present, and the repository contains radioactive particles with a total activity of 40 million TBq (1.1 GCi) long-lived isotopes. Reflected in these figures are also several tens of kilograms of plutonium.
Over the course of the 30 years that the reprocessing facilities have been in use, 127 000 tonnes of solid radioactive waste have been stored underground. A large concrete bunker has also been built to store solid waste at the surface. Containers of solid radioactive materials from the respective production facilities in Seversk are transported to this bunker and hoisted up onto the roof. The contents of the containers are then emptied into the bunker through hatch doors. The empty containers are transported back to their originating points and re-used. The walls of the storage bunker are made of concrete 1.5 m thick, and the entire building approximates a three story apartment building in size. Certain parts of the roof have not been re-sealed; subsequently, doses of radiation at these openings have been measured at 56 mSv/hour (5.6 rem/hour).
The oldest reactor (I-1) in Seversk had an open cooling system; subsequently, the cooling water was contaminated with various radionuclides. This cooling water was released into a canal that flows into the River Chernilshikov, a tributary of the River Tom. Concrete has now been poured around the canal to ensure that the activity does not spread further. Following the shut-down of the first reactor in 1990, the news agency Tass reported that releases of radionuclides would thenceforth be halved.
Due to systematic discharges of contaminated cooling water, increased values for radioactivity are being detected in and around the two rivers. There are signs along the Chernilshikov River warning of high gamma radiation along the river banks. Measurements taken from the juncture where the Chernilshikov River joins the River Tom indicated that the level of gamma radiation was 300 µrads/hour in air and 400 µrads/hour in the water. The normal background for the area is between 10-20 µrads/hour. Gamma radiation in the air of 150 µrads/hour was detected near the river banks of the River Tom, about 2 km below the mouth of the Chernilshikov River. These measurements were taken in the summer of 1990, just before the first reactor was shut down.
Sediment samples taken from the Chernilshikov Channel at a depth of 5 cm indicated that there were 121 Bq/kg of 137 Cs, 4036 Bq/kg of 58Co, 18.564 Bq/kg of 51Cr, and 2.441 Bq/kg of 65Zn. The high levels of the activation products 58Co, 51Cr, and 65Zn indicate the presence of corrosion in one or more of the reactors. Concentrations of 239Pu measuring 3100 Bq/m2 have been detected on the right bank of the Tom River near the village of Chernilshikovo.
In years with dry summers, the water level in the river falls, and the water volume is low such that radioactive particles are rapidly adsorbed to the sediments and are not transported further downstream. At one small village at the juncture of the Chernilshikov Channel and the River Tom, a 239Pu concentration measuring 1200 Bq/m2 was measured in an area cultivated by the local residents for vegetable gardens and hayfields. There is now an ongoing discussion as to whether this village should be evacuated.
In the 1960s, the chemical separation plant produced 90 kilograms more plutonium than was indicated in the plant records. In 1967, as a means of covering over the discrepancy, the facility management decided to transfer the surplus plutonium out of storage to be reprocessed once more. As a result, 50- 60 kg of this plutonium was transported out as waste and discharged into the reservoirs (B1 and B2).
There have been 23 accidents or incidents at the Siberian Chemical Combine resulting in releases of radioactivity to the environment. A short description of the most significant accidents at SCC follows below:
On March 18, 1961, there was an explosion in an evaporator at a test- extraction facility. The explosion occurred as a result of a catalytic reaction between discharged organic fluid and concentrated azot oxide. Two people were killed in the accident (classified 4 on the INES scale).
In 1981, during the removal of fuel elements from one of the reactors, one of the fuel rods broke and fell onto the reactor. This could have led to an uncontrolled chain reaction if Victor V. Goldobin, one of the mechanical engineers present, had not intervened. Goldobin had been standing alongside the reactor when the accident occurred, and apprehending the criticality of the situation, he jumped out onto the reactor and kicked away the broken fuel rod. A chain reaction was averted, but Goldobin's foot was severely irradiated and had to be amputated.
In 1990, another operator lost both of his arms after carelessly placing three plutonium capsules in a container that was only intended to hold one. A chain reaction started because the three capsules exceeded the critical mass for plutonium.
The most serious accident to have taken place so far at SCC occurred on April 6, 1993, at 02:00 local time (06:00 GMT). A tank (No. 6102/1) containing a blend of paraffin and tributyl phosphate exploded, resulting in the involuntary release of uranium, plutonium, niobium, zirconium and ruthenium. The tank had a volume of 34.1 m3, and held 25 m3 of solution. The solution contained 8773 kg of uranium, and about 310 kg of plutonium. The total amount of radiation in the solution was approximately 20.7 TBq (559.3 Ci). The tank was located in a building at the chemical separation plant ("Object 15").
The explosion was so violent that the walls on two floors of the building collapsed. A fire broke out on the roof after the electrical system shorted. The release from the tank was estimated to be 4.3 TBq (115 Ci) of long-lived isotopes. Radioactive material spread to the north-east and fallout was detected over an area of 120 km3. (See map). Gamma radiation 20 times higher than the norm was measured in the area that received the most fallout. The personnel who assisted in putting out the flames received the maximum radiation dose of 2 mSv. The accident is ranked 4 on the INES scale.
In September 1994, Bellona detected gamma radiation two to three times higher than the natural background in the most seriously affected area at the highway east of Seversk, outside the fence surrounding the city. Signs have been erected to warn people against picking mushrooms and berries in the area.
The Russian Ministry of Atomic Energy (MinAtom) has decided to build the main storage facility for plutonium and the highly enriched uranium removed from nuclear warheads in Seversk. Over 10 000 Russian warheads have been or are in the process of being retired and dismantled to comply with the provisions of the START I and START II treaties between Russia and the United States. For the present, however, the retired warheads are stored in temporary storage facilities along with plutonium and highly enriched uranium from dismantled nuclear warheads. A large storage facility for uranium and plutonium with a capacity of 50 000 m2 will be built in Seversk. The facility will be built with economic assistance from the American Nunn-Lugar Fund which totals 600 million USD.
The new storage facility will be comprised of three parts: a central complex where shipments of uranium and plutonium to the facility will be handled by remote control; a second storage area capable of storing 45 000 containers of uranium and plutonium; and a third part which will expand the new facility's storage capacity by an additional 65 000 containers. With American economic and technical assistance, the storage facility could be ready in four years. It has not yet been determined what physical form the stored plutonium and uranium will take. Possibly the plutonium could be stored as it is or else transformed into plutonium oxide (PuO2).
No decision has been made on the eventual disposition of the enormous amounts of plutonium from the warheads. MinAtom hopes to use part of this plutonium as fuel for civilian power plants operating MOX and breeder reactors.
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Photo 2: The triple electric fence sorrounding the entire city has fallen
into disrepair
According to sources in the former KGB, there are 23 000 containers of 239Pu and highly enriched uranium stored in Seversk inside a building that offers no protection from outside sources of damage such as a plane crash, for example.
Security measures around Seversk have become considerably relaxed over the last few years. On the eastern side of the city, the triple electric fence surrounding the entire city has fallen into disrepair and many of the guard posts are unmanned. It is quite possible to get through the fence without being discovered, and one can even pass unnoticed through the main gate.
During the first six months of 1994, there were 65 incidents in Seversk whereby outsiders attempted to bribe the guards to gain entry to the city. Thirty five individuals were arrested as they tried to pass through the fence, another 24 were carrying false documents, and 21 people were caught with documents belonging to other individuals. Organised criminal groups in Tomsk have long been "smuggling" prostitutes into Seversk. The women have simply hidden in the crates of lorries that are never checked.