IBR-2M NUCLEAR REACTOR

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Опубликовано в библиотеке: 2021-09-16
Источник: Science in Russia, №1, 2011, C.21-25

by Viktor AKSENOV, Dr. Sc. (Phys. & Math.), Research Supervisor, Frank Laboratory of Neuron Physics, Joint Institute for Nuclear Research (JINR), Dubna, Moscow, Russia

 

An interdisciplinary approach making it possible to view the world we live in at several levels simultaneously is a salient feature of 21st-century science. Giant experimental setups suit this purpose best of all. These are the sources of synchrotron radiation, free-electron lasers as well as the accelerators and reactors for generation of neutrons. The pulsing nuclear reactor IBR-2M will be completed this year at the Joint Institute for Nuclear Research. The first 4 casettes with fuel were installed in the reactor's active zone on December 17, 2010. There started a long phase of experiments. In September 2011 the facility will fully work experimentally. IBR-2M is Russia's only world class generator of neutrons used for studying the structure of matter and its properties, in creating functional materials, and in developing nano- and biomedical technologies.

 
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SOURCE OF NEUTRONS

 

The very idea was born in 1955 at the Obninsk-based Institute of Physics and Power Engineering just when the nuclear reactor building craze had its heyday. In those days all countries were dead set to obtain power generators or plants for production of radioactive substances–that was viewed as a hallmark of scientific-technical and economic might. The first impulse fast reactor IBR was created in 1960 by the team of the author of this idea Dmitry Blokhintsev, an eminent Soviet physicist and corresponding member of the national Academy of Sciences, who in 1956 became head of the newly established International Center for Nuclear Research at Dubna (reorganized latterly into JINR, or the Joint Institute for Nuclear Research)*. Niels Bohr, one of the fathers of the quantum theory (Nobel Prize, 1922) and elected foreign member to the Soviet Academy of Sciences in 1924, visited the Dubna Institute in 1962. He admired IBR, this wonder of the reactor engineering, a "blinking atom bomb", as Blokhintsev put it. Thereupon there were many efforts to materialize the IBR principle in high-power nuclear reactors. JINR physicists were the only ones to come on top: in 1984 a new reactor, IBR-2**, was put into service; thus Russia became the world's only country to suggest and realize the idea of impulse, or pulsing reactors. The basic units and fuel for this setup were supplied by the USSR Ministry of Medium Machine-Building.

 

IBR-2 had stayed in service for twenty years, up until 25 December 2006 when it was smothered since the service life of its essential components (core vessel, active section, control and protection system) had expired. Thus conserved, the reactor was upgraded for subsequent use, a process will be completed this year. Actually a new pulsing batch-operated reactor, IBR-2M, was created in just a few years on the same floorspace, largely thanks to the moral and financial support of the Ministry of Atomic Energy of the Russian Federation (that had succeeded the Ministry of Medium Machine-Building) and active involvement of its enterprises.

 

The upgraded reactor is remarkable for mechanical modulation of reactivity achieved with the aid of a mobile reflector. This 60 ton system is divided in two parts–the basic and the supplementary reflector. Its rotors, unlike those in IBR-2, are operating at different rates inversely to each other. When both reflectors are aligned near the fuel core, the reactor brings its power up to 1,500 MW and generates pulsating flow of thermal neutrons above 1016 n/cm2/s, which is comparable to that at two super-sources operating on proton accelerators, JMS (Japan) and SNS (USA), commissioned in 2007 and 2009, respectively. The mean capacity of the IBR-2M reactor is 2 MW, the pulse recurrence rate, 5 Hz. The duration of such pulses is a function of two factors–the life of fast neutrons, and the arrangement and the rate of the rotors. For the main mobile reflector the rotation rate is 2.5-fold as low (down to 600 rev./min). Yet owing to the opposing motion, the pulse length stays at 200 µs; simultaneously the reflector resource is up considerably (to 50,000 h).

 

See: A. Sissakian, "Dubna's Worldwide Glory", Science in Russia, No. 2, 2006.–Ed.

 

** See: V. Aksenov, "Pulsed Nuclear Reactor", Science in Russia, No. 6, 2002.–Ed.

 
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Shorthand of the IBR-2M active section: fuel tank with plutonium dioxide, and mobile reflector.

 

Generating a record-high flow of neutrons, IBR-2M is at the same time an economy and relatively low-cost generator. Its modernization bill totaled 40 mln rubles. Activation of the equipment and fuel burnup proceed but slowly thanks to the low average power. If the reactor is at work for 2,500 hours a year, the fuel consumption time and the mobile reflector life will be in the range of 20 to 25 years.

 

A flow of cold neutrons will be upped significantly for some of the extracted beams. This will be achieved using a cryogenic moderator, which is especially important for research studies in the nano and life sciences. The reactor's safety and operational reliability are on a par with up-to-date standards.

 

RESEARCH PROGRAM

 

Neutron methods of research (in diffraction, reflec-tometry, shape-elastic and low angular scattering) provide a wealth of information on the structure, magnetic characteristics and atomic dynamics of materials at the microscopic level. Unique characteristics, such as high resolution as well as compounds with light, magnetic atoms and isotopes, make these methods often the only possible ones for resolving a wide range of pressing basic and applied problems in condensed media physics.

 

The IBR-2M research program is first of all geared to studying the nano- and biosystems.* Studies of nano-structures of ferromagnetic and superconducting layers are set off as an independent area of research. Magnetically ordered, such structures can be used as improved elements in nanoelectronics. Our objective is to identify a correlation between nuclear and magnetic structures of spatial resolution down to 1 nm by the method of reflectometry for polarized neutrons.

 

In studying magnetic liquids and nanocomposites (polymers and granular systems including) a key part is played by the neutron scattering method that helps measure structural parameters of colloids, determine their stabilization mechanisms and other characteristics like interparticle interaction and clustering in different types of liquid and solid carriers, including biocompatible media. The results of these works are to be used for updating the available procedures of synthesis and for the development of new classes of magnetic colloids with preassigned properties.

 

Another trend is related to the mechanisms responsible for aggregation and stabilization of carbon nanopar-ticles in solutions of fullerenes** and nanodiamonds, and identification of a connection between the structures of systems under study and their physicochemical characteristics.

 

Also examined will be the supramolecular structure of polymers (one conditioned by different kinds of macro-molecular adjustment). Research scientists will likewise look into the functional characteristics of colloid and polymer nanodisperse materials alongside phasic transitions of surface-active substances (surfactants), and study the structural characteristics of new polymers good for technological uses.

 

The most promising works here are in the field of biology and biotechnology. They relate to investigations into the nanostructure and characteristics of lipid membranes and complexes, and the role of ceramides (which are

 

See: V. Aksenov, "Neutrons in Nanodiagnostics", Science in Russia, No. 4, 2010.–Ed.

 

** See: "Fullerenes", Science in Russia, No. 6, 2000.–Ed.

 
стр. 23

 

important cell membrane components) in the formation of diffuse characteristics of the matrix of the human epidermis (protective outer layer of the skin). Another area concerns unilayer vesicles, the basic tool of the cell responsible for metabolism and transport of medical drugs across the skin. A wide range of works deals with the structural and functional characteristics of biological macromolecules of protein, DNA and RNA.

 

In these two past centuries one has synthesized oxide materials of most unusual physical characteristics, such as high-temperature superconductivity and great magnetic resistance, combining magnetism and ferroelec-tricity; these materials are capable of transformation with the change of external conditions or environmental parameters. They depend on the specific characteristics of crystalline and magnetic structures where neutron diffractometry is effective for identification. This method as well as neutron spectroscopy is going to be in wide use at IBR-2M for studying new functional materials.

 

We have singled out materials science works into an independent area of research, namely in determining internal stresses in volumetric materials by the diffraction method. A high-precision deep-invasive technique, it allows neutrons to spot point defects, dislocations, interphasc boundaries, microcracks and pores. Such data are of the utmost importance in manufacturing devices for nuclear science and engineering, and in making corresponding parts and units for machines and mechanisms.

 

As to the earth sciences, we are planning experiments on neutronographic analysis of the texture of geological materials and in pinpointing the causes of rock instability under the effect of high temperatures and pressures, including phasic (polymorphous) transitions. These data will expand our knowledge of the geology of planets and processes occurring in earthquake sources.*

 

USER GROUP CENTER

 

The IBR-2M reactor is equipped with a set of 12 spectrometers allowing to make use of advantages offered by neutrons in structural studies. These are home-made products opening up new opportunities for modern setups. This is true above all of a high-resolution Fourier diffractometer designed at Dubna in 1992 in cooperation with the St. Petersburg-based Konstantinov Institute of Nuclear Physics and Finland's Center of Neutron Studies. It can interpret the crystalline structure down to four decimal places (0.0001) of atomic spacing, which is the limit for neutron diffraction. Taking this factor into consideration, we are working on a specialized Fourier diffractometer for studying internal stresses in materials. Incidentally, our experience has been adopted in a new neutron setup of the European Union, the European Spallation Source (ESS).

 

The IBR-2M modernization program will be carried on in 2011 as well. Three projects are now at the final stage. The first one deals with replacing the 110 m neutron-aided system for the spectrometers EPSILON, SCAT (both developed with active involvement of German physicists) and NERA (the idea suggested and realized by Polish colleagues). These projects are oriented to studying internal stresses in civil engineering struc-tures, materials and rocks (geology), and in learning

 

See: L. Doda et al., "Space Monitoring of Earthquake Forerunners", Science in Russia, No. 6, 2009.–Ed.

 
стр. 24

 

 

IBR-2M experimental hall has 14 neutron exit channels.

 

more about the atomic and molecular dynamics of complex systems and functional materials.

 

The second project relates to a new diffractometer, DN-6, is meant for studying the behavior of materials at high pressures (up to 50 GPa) and low temperatures (down to 10 K). Sapphire anvils will be used in it.

 

And the third project involves an original reflectome-ter, GRAINS, being realized by us in tight cooperation with physicists of Germany and Hungary, with the participation of the Scientific-Educational Center of Lomonosov Moscow State University. The need in such devices is high because of the great interest in nanosys-tems. Obtaining such kind of technology, we shall be able to explore free surfaces of liquid media in a gravitational field as well as phasic interfaces in the air-liquid, liquid-liquid, and liquid-solid body systems. Besides, GRAINS opens up avenues for investigating the magnetic qualities of liquids with the use of polarized neurons.

 

This reflectometer is a part of the unique nanodiag-nostics complex operating on the source of cold neutrons at IBR-2M working on a wavelength 0.4 nm, and this is what is needed for studying nanosystems. The component cryogenic moderator operating at low temperatures in the 20-40 К range on a radiation-stable material (a mixture of aromatic hydrocarbons) is provided with a new loading and operational technology to increase a flow of cold neutrons more than tenfold in four neutron exit channels. In addition to GRAINS, the complex includes still another three plants: REMUR, a reflectometer for polarized neutrons having the world's best parameters; REFLEX, meant for innovative techniques in neutron optics; and a spectrometer of low angular scattering of neutrons that we need so much (and yet cannot afford it for lack of wherewithal).

 

Giant setups like IBR-2M are to cater to a wide range of researchers at universities and colleges at home and abroad. To get the reactor to perform with good efficiency (2,500 hours a year on 14 neutron beams), we need about 30 mln rubles annually given that outside users are in for 70 percent of its operating time, a procedure adopted in world practice. Will this money be allotted, that is a big question.

 

And last but not least, such setups are a good experimental base for coaching research scientist. The JINR center has been doing its best in this regard.* Its research school is home to graduate and post-graduate students from countries associated with JINR, with the Chairs of Neutronography (Lomonosov Moscow University) and Neutron Physics (St. Petersburg Polytechnic) teaching our senior students. The Konstantinov Institute of Nuclear Physics is taking care of the required scientific and research base. We have prepared skilled research personnel both for the world's leading neutron centers and even for our home center at Dubna. In this sense the IBR-2M research program has a good future.

 

See: A. Sissakian, "Frame Projects–Breakthrough to Future", Science in Russia, No. 6, 2008.–Ed.


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© Viktor AKSENOV () Источник: Science in Russia, №1, 2011, C.21-25

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