RIAR seeks leading research role30 June 1998
With seven operating reactors, the Research Institute of Atomic Reactors (RIAR), a closed city until very recently, has the facilities, the people, the economic potential, and the drive to become a leading international nuclear research centre.
Tucked away in the woods in central Russia’s “black earth” district, half way between Samara and Ulyanovsk, where Lenin was born, is the small country town of Dimitrovgrad. It serves the nearby Research Institute of Atomic Reactors (RIAR), one of the biggest of the former Soviet nuclear research centres, occupying an area of 17 km2. The Institute, founded in 1956 on the initiative of Academician I V Kurchatov, was a closed city until very recently. However, its dynamic director, Professor Valentin Ivanov, welcomed the lifting of restrictions at the institute and hopes to make it an international centre of excellence for nuclear research.
The institute has a staff of 5000 including over 500 scientists and its many unique facilities attract specialists from other institutes, including the Institute of Physics and Power Engineering in Obninsk, Moscow’s Kurchatov Institute, NIKIET and others. As well as a range of research reactors, the institute has materials science and radiochemical laboratories with well-equipped hot cells, and supporting facilities including experimental production units and a computer centre as well as a unique waste disposal system involving deep direct injection underground. While RIAR faces the same economic pressures as other Russian scientific centres, morale is generally high and serious wage arrears are avoided, partly as a result of a steady income from the sale of specialist radioisotopes and increasing international co-operation, although as Deputy Director Professor Oleg Skiba notes: “We always lack money”.
Ivanov is proud of what he describes as the institute’s “zoo of reactors”.
There were until recently eight different research and prototype power reactors, but one is now closed (see panel). The Institute’s huge materials science department, established in 1964, now comprises a complex of three buildings with a total of 51 hot cells and over 100 shielded boxes. The department conducts research on reactor metals, the physics and structure of reactors, the properties of metals, the use of transplutonium elements and general nuclear physics. Work includes identification and development of the most promising materials for fuel element casings and development of various types of nuclear fuel. Work is also under way to develop an effective technology for the production of transplutonium elements and to extend the range of their economic application.
A hot materials laboratory and various research reactors are used for these studies. The hot materials laboratory investigates all types of spent fuel assemblies. Its facilities comprise seven hot cells, two very large (see figure), a transport hall with a travelling bridge crane (up to 50000 kg load capacity) and a cooling pool to store fuel assemblies and elements. Special containers are used to transport them from the pool to the hot cells. In this laboratory irradiated fuel elements can be cut up and refabricated for further irradiation and study. It can cater for assembly up to 6 m long and weighing up to 800 kg. “We will deal with any type of assemblies and will welcome any contracts,” says Skiba. Some contract work has already been done and there are plans to undertake specific investigations for the UK, Finland (the Loviisa VVER plant), France (Fragema) and the US. But most work involves contracts with Russian nuclear power plants to investigate the safety of VVER-1000 and VVER-440 fuel. The spent fuel assemblies are brought to the plant mainly by a dedicated rail line using purpose built containers.
NOVEL REPROCESSING RECYCLE
At RIAR’s Radiochemistry Department, set up in 1965, work is well advanced on a relatively simple and safe method for making and reprocessing reactor fuel in a closed cycle. In special hot cells spent fuel is declad without the use of water (the cladding is melted) and the separated fuel goes immediately for dry processing (see panel).
“The technology could be installed on a reactor site, making possible the re-use of spent fuel in new assembles following reprocessing. This removes the need for the transport of radioactive materials between different facilities. As it is a short cycle, the need for storage of spent fuel is also reduced,” explains Ivanov. “It is a dry process, producing no liquid wastes, and solid wastes are minimal. Moreover the process is such that a certain level of impurities can be deliberately left in the fuel to make it useless for military purposes.”
RIAR has a pilot facility which has been producing fuel by this method for various types of reactor since 1961. The fuel can be uranium or MOX based. Fuel elements produced by this method for Russia’s fast breeders and research reactors achieve record burn up levels of over 26% and sometimes over 30%.
The main reason why the method has not been more widely applied inside Russia is the established position of the large facilities producing fuel by conventional methods and an infrastructure geared to reprocessing at a separate site. The method was originally designed to make MOX fuel for fast reactors, which were once seen as the key to the world’s energy problems. A large MOX plant was being built at the Mayak reprocessing facility in the Urals which would have had one conventional line and one for vibropacking. However, this project has been frozen. RIAR also installed a new hot cell line in 1986 to make fuel for larger fast reactors (BN-600s and future BN-800s) but this was also mothballed. However pilot scale production of experimental assemblies has continued. “We have tested thousands of rods for the BOR-60 containing a total of 500 kg of plutonium,” says Ivanov. A few experimental assemblies have also been made for VVERs and a demonstration programme is under way to show how easily minor actinides can be incorporated into fuel produced in this way.
Recently, interest in fast breeders has revived with the need to dispose of growing stockpiles of plutonium, and RIAR is now planning to build a new automated line for BOR-60 fuel. “In any case, the method has a lot of advantages,” insists Skiba. “It is much cheaper and safer than traditional methods.” Ivanov explains that because the technology excludes water there is little risk of corrosion. The method also reduces any risk of fire and volatility is very low. “The fuel is a crystallised product and is thousands of time safer,” he says. “When we cleaned the chamber the need for decontamination was minimal.”
RIAR has received inquiries about the process from various countries, including Japan and South Korea. BNFL has also expressed interest. “However, foreign customers generally prefer pelleted fuel because they know it works,” Ivanov admits. But even this need not be a problem. “Our engineering lines are so flexible that we could produce pelleted granulate if necessary,” he says.
Ivanov believes this technology could form the basis of small closed fuel cycles at each reactor site. Reactor fuel could be recycled several times with the same material being used again just a few months after it was removed from the core. This could remove the need for large regional or central facilities and for complex systems of transport. “Anyone just entering the nuclear field should use this technology,” he says. “It is twice as cheap. Unfortunately we in Russia missed the boat and a lot of money was spent developing pellet technology.”
|RIAR has seven operating reactors: SM-2/3, RBT-6, RBT-10/1, RBT-10/2, MIR, BOR-60 and VK-50. An eighth reactor – ARBUS is no longer operating. • SM-2/3. A thermal/fast neutron reactor commissioned in October 1961, SM-2/3 is used for irradiating samples of reactor materials and for studying their properties. It is also used to produce transuranic elements and for a range of studies in nuclear physics. It is the first reactor design to use a flow of thermal neutrons of high density in a slow-down cavity within a core which has a rigid neutron spectrum. The core comprises 28 fuel assemblies, each containing about one kilogram of uranium-235. The reactor has been upgraded several times. In 1965 the size of the core was increased to boost the rated power from 50 MW to 75 MW. In 1974 the heat-exchange equipment was rebuilt, further increasing capacity to 100 MW. In 1978 the reactor reached its limits, given its existing cooling circuits, with very high thermal loads in the core. The reactor was reconstructed in 1991/2 and recommissioned in January 1993 as the SM-3. Recent work includes tests on materials for VVER reactors. • RBT-6, RBT-10/1, RBT-10/2. The RBTs are pool-type thermal reactors. Spent fuel elements from SM-2/3 are used as fuel. The oldest reactor of this type, RBT-6 (6 MW), has been in service since October 1975. Recently a unique stand, “Korpus,” has been added to study materials in different neutron fluxes. Two reactors of the RBT-10 type (10 MW), located in the same water pool, began operating in December 1983 and December 1984. They have more cells in the core and a more efficient emergency control system as well as increased power. Recently RBT-10/2 has been used to investigate creep in VVER fuel element cladding materials. • MIR. A 100 MW thermal neutron heterogenous channel-type reactor designed for material testing, MIR began operation in December 1966. It is used for the first round of tests on fuel elements for nuclear plants. The core, about 1 m in diameter, is submerged in a pool under 9 m of water. The core comprises 48 fuel assemblies. The reactor has seven loop facilities which can be used to test fuel assemblies for power and research reactors which use water, gas or an organic coolant. In 1975 MIR was upgraded to change the configuration of the core and introduce other improvements. Recent work includes tests on the burn-up of VVER fuel. • BOR-60. BOR-60 was one of the world’s first liquid-metal-cooled (sodium) fast-neutron experimental reactor to be used as a nuclear power plant. It began operating in 1969. The 12 MW reactor was designed to test individual assemblies and whole complexes of equipment as well as control and measuring instruments to test their possible use in fast reactor power plants. Sodium-water steam generators are developed and tested. A large number of uranium and MOX fuel elements have already been tested. Tests on BOR-60 are generally used to improve operation of the BN-350 (Kazakhstan) and BN-600 (Beloyarsk) fast reactor power plants and for designing units of higher power. Recent efforts have concentrated on improving fast reactor fuel, including MOX. • VK-50. A 170 MW pilot power plant based on a tank-type boiling water reactor, VK-50 has been in service since October 1965. It is now used for both research work and electricity generation. Its core comprises 88 hexahedral fuel assemblies each containing 162 fuel rods. The VK-50 is used for investigating the operation and use of BWRs for heat-generating nuclear plants. The reactor was closed for brief periods in 1996 following two accidents. • ARBUS. ARBUS was an AST-1 heat-generating pilot nuclear plant using an organic coolant. In 1962 a crack developed in the reactor vessel causing a serious accident and the unit was rebuilt. It was restarted in November 1979 but is now closed. In the mid-1980s the Institute was developing plans to build an experimental high-temperature gas-cooled reactor, called Prima, in the Ulyanovsk region but after a 1989 referendum the project was suspended.|