[en] Increased interest in development of nuclear power engineering, first of all in non-nuclear countries, puts an emphasis on the designing of small and medium nuclear power plants and determines the growth in nuclear technology export from countries with advanced nuclear industries. It accentuates the issue of reduction of the nuclear material proliferation risk, which was repeatedly raised on the national an international levels (materials of INPRO, GNEP, IAEA). There is no denying that the key factor in solving nonproliferation-related issues is, first of all, abidance by the international agreements and non-proliferation commitments. Nevertheless, main properties of reactor plants, their on-site operating conditions and employed fuel cycles can also contribute to reduction in nuclear material proliferation risks. This report summarizes High Temperature Gas Cooled Reactor (HTGR) designing principles used to reduce the risk of nuclear material proliferation, as well as results of nonproliferation features comparative analysis of being developed GT-MHR plants related to HTGR and PWR. Proliferation resistance characteristics were evaluated using the INPRO methodology modified by KAERI for application with the DUPIC fuel cycle (Direct use of PWR spent fuel in CANDU)

[en] Currently in a number of the countries the development of reactor designs for the following generation is being carried out. Among reactors of a new generation the direction of high-temperature gas cooled reactors (both thermal, and fast - GFR), in particular, is recognized. The purpose of the given work is research the opportunities of HTGRs with a hard neutron spectrum to increase the duration of reactor campaign due efficient neutrons usage at preservation of specific core power density, characteristic for HTGRs with a thermal neutron spectrum. The given purpose can be achieved at use fuel blocks with dense packing of coated particles in the fuel block volume. To solve the presented problem the variant of so-called 'return' fuel assembly is proposed where the coated fuel particles in fuel block matrix material occupy all volume of the block except for standard channels under the coolant. In this case the volume fractions of materials in prismatic type assembly will take approximately 19/31/50 %% accordingly for the coolant, fuel kernels and matrix including the coatings. As results of unit-cell calculations show the small rate of reactivity falling presumes to compensate the reactivity margin by control rods without burnable poison using. The core campaign is comparable with service life of power plant and can consists of 40 years. (authors)

[en] Information on advancements made in small transportable NPP with HTGR and gas-turbine cycles as the source of energy for supplying electricity and heat in remote regions is presented and the possibility of their development at the current stage is analyzed. This pertains especially to the remote regions of the Far North with extreme climatic conditions: ambient air temperature –50–35°C in the absence of water for dumping unused heat. The possibilities of developing a small transportable nuclear power plant based on schematic and structural engineering studies performed at OKBM Afrikantov with high-temperature gas-cooled reactor and different variants of energy conversion systems are analyzed.

[en] An analysis is presented of different methods of controlling the useful capacity of reactor units with hightemperature gas-cooled reactor and a gas-turbine system for converting energy on the basis of the Brayton cycle: by changing the pressure (mass) of the gas in the loop, the power of the reactor, and the temperature of the gas at the entry into the turbine by means of internal transfers of gas in the loop. The power dependences of the change in the basic parameters are obtained in the range from minimum to 100% in application to a reactor unit with thermal power 600 MW with a single-shaft turbomachine, which qualitatively, taking account of the lag of the processes in the reactor, can be extended to low-capacity units.

[en] A power-generating unit with the high-temperature helium reactor (GT-MHR) has a turbomachine (TM) that is intended for both conversion of coolant thermal energy into electric power in the direct gas-turbine cycle, and provision of helium circulation in the primary circuit. The vertically oriented TM is placed in the central area of the power conversion unit (PCU). TM consists of a turbo-compressor (TC) and a generator. Their rotors are joined with a diaphragm coupling and supported by electro-magnetic bearings (EMB). The complexity and novelty of the task of the full electromagnetic suspension system development requires thorough stepwise experimental work, from small-scale physical models to full-scale specimen. On this purpose, the following is planned within the framework of the GT-MHR Project: investigations of the 'flexible' rotor small-scale mockup with electro-magnetic bearings ('Mini-mockup' test facility); tests of the radial EMB; tests of the position sensors; tests of the TM rotor scale model; tests of the TM catcher bearings (CB) friction pairs; tests of the CB mockups; tests of EMB and CB pilot samples and investigation of the full-scale electromagnetic suspension system as a part of full-scale turbo-compressor tests. The rotor scale model (RSM) tests aim at investigation of dynamics of rotor supported by electromagnetic bearings to validate GT-MHR turbomachine serviceability. Like the full-scale turbomachine rotor, the RSM consist of two parts: the generator rotor model and the turbo-compressor rotor model that are joined with a coupling. Both flexible and rigid coupling options are tested. Each rotor is supported by one axial and two radial EMBs. The rotor is arranged vertically. The RSM rotor length is 10.54 m, and mass is 1171 kg. The designs of physical model elements, namely of the turbine, compressors, generator and exciter, are simplified and performed with account of rigid characteristics, which are identical to those of the full-scale turbomachine elements. (authors)

[en] The high-temperature gas-cooled reactor technology is the only nuclear technology capable of achieving coolant temperatures as high as 950 deg. C and at the same time ensuring safe and efficient production of both electricity and hydrogen. OKBM and GA started independent research in this area in the 1990's. In 1995, OKBM in cooperation with GA started development of the GT-MHR design which combines a safe modular reactor and a power conversion unit based on the high-efficiency Brayton cycle. The power conversion unit in the GT-MHR design has integral configuration, with vertical arrangement of the turbomachine consisting of a synchronous generator and a turbo-compressor. Active electromagnetic bearings are used as supports. In order to select optimal technical solutions, the effect of the following factors on the design was considered: vertical or horizontal arrangement, submerged or remote generator with oil bearings, and different turbomachine rotor speeds. Application of electromagnetic bearings and diaphragm coupling between the rotors, integral arrangement of the turbomachine inside the power conversion system vessel, and use of helium as coolant required performance of comprehensive analyses and experiments. For this purpose, the helium turbomachine technology demonstration program was developed and is currently being implemented. This technology demonstration program aims at validating the quantitative and qualitative characteristics of such turbomachine components as electromagnetic and catcher bearings, control system, computer codes, generator, diaphragm coupling, turbo-compressor, etc. At the concluding stage of the technology demonstration program, a full-scale turbo-compressor model will be tested at a helium test facility. The present paper lists the main parameters of the GT-MHR turbomachine and describes the status of experimental validation of its components. (authors)

[en] The paper deals with the issue of increasing efficiency of nuclear power plants with the modular high-temperature helium reactor (HTGR) and direct gas turbine cycle. It should be noted that only this combination can highlight the advantages of the HTGR, namely the ability to heat helium to about 1000 deg. C, in comparison with other reactor plants for electricity generation. The HTGR has never been used in the direct gas turbine cycle. At present, several designs of such commercial plants are at the stage of experimental validation of main technical features. In Russia, 'OKB Mechanical Engineering' together with 'General Atomics' (USA) are developing the GT-MHR project with the reactor power of 600 MW, reactor outlet helium temperature of 850 deg. C, and efficiency of about 45.2%; the South African Republic is developing the PBMR project with the reactor power of 400 MW, reactor outlet helium temperature of 900 deg. C, and efficiency of about 42%; and Japan is developing the GTHTR-300 project with the reactor power of 600 MW, reactor outlet helium temperature of 850 deg. C, and efficiency of about 45.6%. As it has been proven by technical and economic estimations, one of the most important factors for successful promotion of reactor designs is their net efficiency, which must be not lower than 47%. A significant advantage of a reactor plant with the HTGR and gas-turbine power conversion unit over the steam cycle is considerable simplification of the power unit layout and reduction of the required equipment and systems (no steam generators, no turbine hall including steam lines, condenser, deaerator, etc.), which makes the gas-turbine power conversion unit more compact and less costly in production, operation and maintenance. However, in spite of this advantage, it seems that in the projects currently being developed, the potential of the gas-turbine cycle and high-temperature reactor to more efficiently generate electricity is not fully used. For example, in modern reactor plants with highly recuperative steam cycle with supercritical heat parameters, the net efficiency of electricity generation reaches 50-55%. There are three methods of Brayton cycle carnotization: regeneration, helium cooldown during compression, and heat supply during expansion. These methods can be used both separately and in combination, which gives a total of seven complex heat flow diagrams. Besides, there are ways to increase helium temperature at the reactor inlet and outlet, to reduce hydraulic losses in the helium path, to increase the turbomachine (TM) rotation speed in order to improve the turbine and compressor efficiency, to reduce helium leaks in the circulation path, etc. The analysis of GT-MHR, PBMR and GTHTR-300 development experience allows identification of the main ways of increasing the efficiency by selecting optimal parameters and design solutions for the reactor and power conversion unit. The paper estimates the probability of reaching the maximum electricity generation efficiency in reactor plants with the HTGR and gas turbine cycle with account of the up-to-date development status of major reactor plant components (reactor, vessels, turbo-compressor (TC), generator, heat exchange equipment, and structural materials). (authors)

[en] The paper presents a description of benchmark cases, achieved results, analysis of possible reasons of differences of calculation results obtained by various neutronic codes. The comparative analysis is presented showing the benchmark-results obtained with reference and design codes by Russian specialists (WIMS-D, JAR-HTGR, UNK, MCU, MCNP5-MONTEBURNS1.0-ORIGEN2.0), by French specialists (AP0LL02, TRIP0LI4 codes), and by Korean specialists (HELIOS, MASTER, MCNP5 codes). The analysis of possible reasons for deviations was carried out, which was aimed at the decrease of uncertainties in calculated characteristics. This additional investigation was conducted with the use of 2D models of a fuel assembly cell and a reactor plane section. (authors)