The main characteristics of ru with vtgr. The use of high-temperature modular helium reactors for heat supply of energy-intensive industries Main technical characteristics

Russia and the United States are jointly developing a project nuclear power plant future. According to the developers, it will significantly surpass all previous systems in terms of safety, efficiency, and many other parameters. Despite the growth in the use solar panels, wind and wave energy, and other alternatives, we will not leave the "classical" energy in the coming decades. And here, perhaps, the most environmentally friendly is, oddly enough, nuclear energy.

Environmentalists constantly talk about the fact that thermal power plants poison the atmosphere with millions of tons of poisons and greenhouse gases. Hydroelectric power plants, or rather accompanying reservoirs, irreversibly change nature for many tens of kilometers around, affect the habitat of thousands of species, and exert enormous pressure on the earth's crust.

The new NPP scheme eliminates many of the old systems from its design. On the American side, the main participant in the project is General Atomics, and on the Russian side, the Experimental Design Bureau of Mechanical Engineering named after I.I. Afrikantov in Nizhny Novgorod, subordinate Federal agency for Atomic Energy of the Russian Federation.

And since experts see the future of nuclear energy in a new type of nuclear power plant, let's get to know how it will work.

This system is called Gas Turbine - Modular Helium Reactor (GT-MHR), and in Russian - “Gas Turbine - Modular Helium Reactor reactor" - GT-MGR. A large number of American and Russian institutions and organizations, as well as companies from France and Japan, are involved in the creation of a fundamentally new nuclear power plant.

The novelty of the project lies in two main postulates. A nuclear reactor cooled by gaseous helium and with inherent safety (that is, the stronger the heating, the weaker the reaction) and the shortest conversion of hot helium energy into electricity using a gas turbine of the so-called closed Brayton cycle. Since the capsules of the active substance are buried in the ground, there is no need to use additional equipment (pumps, turbines, surface pipes), which simplifies the installation of the station and reduces the cost of its construction and maintenance.

Everything is encapsulated. In this case, even the failure of the control system does not lead to fuel melting. Everything automatically damps and slowly cools down due to heat dissipation into the ground surrounding the station.

The fuel for the station is uranium oxide and carbide or plutonium oxide, made in the form of balls with a diameter of only 0.2 millimeters and covered with several layers of various heat-resistant ceramics. Highly reactive metals are “poured” into rods, which form an assembly, and so on. The physical (mass of the structure, reaction conditions) and geometrical parameters of the reactor are such (comparatively low energy density, for example) that in any event, even a complete loss of coolant, these balls will not melt.

The entire active zone is made of graphite - there are no metal structures at all, and the heat-resistant alloy is used only in the outermost case - the capsule. So even if all the plant personnel for some reason cannot start servicing the equipment, the temperature in the heart of the nuclear power plant will jump to a maximum of 1600 degrees Celsius, but the core will not melt. The reactor itself will begin to cool, giving off heat to the surrounding soil.

The operation of the station, as mentioned above, is based on gas turbine- modular helium reactor. GT-MGR is a graphite-gas reactor assembled in two modules: a high-temperature reactor unit and an energy conversion unit (PCU). The first contains the core and the reactor control and protection system (CPS), and the second includes: a gas turbine with a generator, a recuperator, refrigerators. Energy conversion - a closed single-loop Brayton cycle.

Both modules of the reactor plant are located in vertical reinforced concrete shafts below ground level. The main advantages of using this device are its high efficiency and the impossibility of destroying the core in the event of an accident. The disadvantage that developers highlight at the moment is low power. To replace one VVER-1000 unit, four GT-MGR units are required. This drawback is caused, on the one hand, by the use of a gas coolant that has a low heat capacity compared to water or sodium, and, on the other hand, by the low energy density of the core as a result of increased requirements to the safety of the reactor. But this seemingly insignificant, at first glance, feature casts doubt on the arguments about simplifying the design of NPPs with GT-MHR.

Doctor of technical sciences AND I. Stolyarevsky, Leading Researcher, National Research Center "Kurchatov Institute",
director of the KORTES Center, Moscow;
Ph.D. N.G. Kodochigov, chief designer, A.V. Vasyaev, head of department,
d.t.s. V.F. Golovko, Chief Specialist, M.E. Ganin, Lead Design Engineer,
OKBM Afrikantov OJSC, Nizhny Novgorod

1. Introduction

The growth of world demand for fuel and energy with the resource and environmental limitations of traditional energy makes it timely to prepare a new energy technology that can take on a significant part of the increase in energy needs, stabilizing the consumption of fossil fuels. The Energy Strategy of Russia for the period up to 2020 defines communal heat supply as the most socially significant and fuel-intensive sector of the economy. The demand for nuclear energy sources in the areas of power generation and domestic heat supply is due to the growing cost of fossil fuels and an increase in energy consumption. The key factors in the creation of nuclear power units are the high safety of power plants and their commercial attractiveness. “Strategy for the development of nuclear energy in Russia until 2030 and for the period up to 2050”, approved by the Government Russian Federation provides for the generation of heat by nuclear energy sources up to 30 million Gcal/year by 2020 with annual replacement of consumption up to 24 billion m 3 of gas. The creation and implementation of nuclear power plants in the heat supply sector will create new generating capacities and ensure savings in natural gas for export abroad, which is a factor of geopolitical significance.

However, even the large-scale introduction of nuclear energy into the field of electric generation and municipal heat supply does not solve the problem of the growing demand for motor fuel and industrial heat. The long-term scenario for the development of nuclear energy until 2050 provides for the replacement of fossil fuels not only in the public sector, but also in energy-intensive industries by expanding the scope of nuclear energy for the production of hydrogen, process heat, and synthetic fuel. The inevitability of the mass use of new energy technologies is determined by a qualitative change in environmental requirements in the energy sector and transport.

The potential for the introduction of nuclear energy in the "non-electric" sphere is determined by the volume of energy consumption of process heat by industry and is not inferior in scale to the electric power industry. In the field of manufacturing industries, the leaders in the consumption of thermal energy are chemical industry, oil refining, metallurgy (table 1).

Table 1. Heat consumption by manufacturing industries (2007)

Thus, the introduction of nuclear technologies in the heat supply of industrial processes is an urgent task that still needs to be solved.

Today, the only nuclear technology that is really capable of most fully solving the problem of replacing fossil fuels in industrial heat supply and transport is the technology of high-temperature modular helium reactors (MHR).

The benefits of MGR are determined by the following factors:

The possibility of heating the coolant at the exit from the core to a temperature of 1000 °C, which expands the scope nuclear energy not only for the production of electricity and municipal heat, but also for technological purposes, including the production of hydrogen;

Possibility of using various schemes of the power unit: with a gas turbine cycle, with a steam turbine cycle, with a circuit for transferring high-temperature heat to technological production;

The passive principle of residual heat removal, providing high level safety, including in case of complete loss of the primary coolant;

Ensuring the regime of non-proliferation of fissile materials, which is based on the properties of ceramic microfuels;

Low thermal effect on environment due to the possibility of implementing effective thermodynamic cycles for converting thermal energy into electricity (in the direct Brayton gas turbine cycle, the efficiency of energy conversion can reach 50% or more);

Possibility of combined generation of electricity and heat;

The minimum number of systems and components of the reactor plant (RP) and plant when using the gas turbine cycle in the primary circuit, creating prerequisites for reducing capital and operating costs;

Possibility of modular execution of the unit with a wide range of module power (from 200 to 600 MW) and variation of AC power by a set of modules;

2. Design solutions for energy sources for industrial heat supply

Based on predictive studies of the development and needs of the energy market, pre-conceptual studies of a prototype commercial MGR reactor plant with a unified modular helium reactor with a thermal power of ~200 MW and, based on it, a number of energy sources for various energy technological applications were carried out.

The design basis for these developments was the world experience in creating experimental facilities with a high-temperature gas-cooled reactor (HTGR), the experience in developing in Russia (more than 40 years) projects of reactor plants with HTGR of various power levels (from 100 to 1000 MW) and purposes.

The results of the development of the project of the GT-MGR reactor facility with a modular helium reactor, carried out within the framework of the Russian-American program, were also used.

As part of the study, several options for MHR for power engineering purposes were considered:

For the production of electricity and municipal heat supply, with the conversion of the thermal energy of the core into electrical energy in the direct gas turbine (GT) cycle of Brighton - MGR-100 GT;

For the production of electricity and hydrogen by high-temperature steam electrolysis (HEP) - MGR-100 VEP;

For the production of hydrogen by the method of steam reforming of methane (SCM) -
MGR-100 PKM;

For high temperature heating petrochemical production(NP) -MGR-100 NP.

Each version of the MGR-100 installation consists of energy and technological parts.

The energy part is maximally unified for all options and is a power unit that includes a reactor and, depending on the purpose, a gas turbine power conversion unit (PCU) designed for generating electricity, and (or) blocks of heat exchange equipment.

The technological part of the MGR-100, depending on the purpose, is either a process plant for the production of hydrogen or high-temperature heat supply circuits that supply heat to various technological processes.

The main criteria in the selection of technical solutions were to ensure high technical and economic indicators in terms of generating electricity and high-potential heat, minimizing the impact on service staff, the population and the environment, the exclusion of radioactive contamination of the technological product.

The energy source configuration is based on the following principles.

The power of the reactor and its design are universal for all variants of the energy source; only the parameters of the coolant differ. The choice of the RI power level (215 MW) was determined by:

the needs of the electric power industry and communal heat supply;

The needs of industrial enterprises in high- and medium-temperature heat supply technological processes;

Technological capabilities of domestic enterprises for the manufacture of the main equipment of the reactor plant, including housings.

The reactor is a modular reactor with an active zone consisting of hexagonal prismatic fuel assemblies, with a helium coolant, which has the properties of internal self-protection. Security is ensured through the use of passive principles of operation of systems. Residual heat release and accumulated heat are removed from the core through the reactor vessel to the reactor shaft cooling system and further into the atmosphere using natural physical processes of heat conduction, radiation, convection without exceeding the limits of safe fuel operation, including in accidents with a complete loss of primary coolant , in case of failure of all active means of circulation and power supply sources.

The coolant is circulated in the primary circuit loops by the main circulating gas blower (MCP) or compressors of the BPE turbomachine.

The layout of all MGR-100 variants under consideration is made taking into account the requirements for the safe operation of the reactor plant in all possible accidents at the NPP. Each reactor plant is located in the NPP main building, which consists of the ground part, which is the reactor maintenance and refueling building (central hall) and underground low-pressure containment (RI containment), located under the central hall.

The containment houses the power equipment of the reactor plant and the equipment of the main systems important to safety. The containment is made of monolithic reinforced concrete, airtight, with internal dimensions: diameter 35 m, height no more than 35 m, capable of withstanding the internal pressure of the medium up to 0.5 MPa in case of depressurization of the primary circuit of the reactor plant and/or pipelines of the secondary circuit. The containment provides optimal use of space and volume of premises, high compactness of equipment placement, facilitation of equipment replacement and fuel refueling operations, tightness with respect to adjacent premises of the NPP main building and the environment, heat removal to the ground in beyond design basis accidents.

The design of the primary circuit equipment has a block design. The main power equipment of the MGR-100 is located in a steel block of buildings, which consists of a vertical reactor vessel, one to three vertical vessels of the WPT and heat exchange equipment, and one to three horizontal connecting vessels connecting the vertical vessels into a single pressure vessel (Fig. 1). The main equipment housings are similar in size to the VVER reactor vessel. Special attention paid attention to minimizing the number of external pipelines of the primary circuit.

Fig.1. The layout of the reactor plants: a) MGR-100 GT; b) MGR-100 VEP; c) MGR‑100 PKM; d) MGR‑100 refinery

The energy source options for MGR-100 GT and MGR-100 VEP (Fig. 2.3) provide for the use of a unified gas turbine PET. The central place in the BPE is occupied by a turbomachine (TM), which is a vertical unit consisting of a turbocompressor (TC) and a generator, the rotors of which have different rotational speeds - 9000 rpm and 3000 rpm, respectively. Electromagnetic bearings are used as the main bearings. The generator is located outside the helium circulation loop in the air environment. WPT pre and intermediate coolers are placed around the TC. The heat exchanger is located in the upper part of the housing above the axis of the hot flue. Waste heat is removed from the primary circuit in the WPT precooler and aftercooler by the cooling water system and further to the atmospheric air in fan dry coolers. It is possible to consider the option of using waste heat for heating needs and hot water supply.

Heat exchanger units are designed to transfer thermal energy from the reactor to the consumer in energy technology production. Depending on the working environment, the type of process and the likelihood of radioactivity getting into the product of technological production and contamination of the equipment with radioactive products, a two- or three-loop RI scheme can be used.

Thus, in the NPP for the production of hydrogen by the method of high-temperature electrolysis of steam (MGR-100 VEP) and the method of steam reforming of methane (MGR-100 PKM), a two-circuit scheme is used. In these processes, the main component of the process medium is water vapor. The analysis performed shows that, with possible emergency situations with the depressurization of the steam generator or high-temperature heat exchanger, the effects of the ingress of hydrogen-containing products into the reactor are reliably regulated by the reactor control and protection systems.

The variant of the energy source for supplying heat to petrochemical production (MGR-100 NP) provides for a three-circuit thermal scheme. The transfer of heat from the reactor plant to the consumer is carried out through a high-temperature helium-helium intermediate heat exchanger and an intermediate helium circuit, and then to the NP network circuit. This solution limits the release of radioactivity into the network circuit, ensuring the radiation purity of the process product, as well as minimal contamination of the primary circuit with process impurities.

The main technical measures aimed at eliminating the potential danger of radioactivity getting into the product of technological production are the creation and maintenance of a guaranteed pressure drop (~0.5 MPa) directed towards the primary circuit, and for the MGR-100 NP version, also the introduction of an intermediate circuit. Operational helium leaks from the intermediate circuit to the primary circuit do not have a negative impact on the reactor plant.

2.1 Energy source MGR-100 GT for power generation and municipal heat supply

The power source MGR-100 GT is intended for the production of electricity in a direct gas turbine cycle. Heat waste heat of the gas turbine cycle (more than 100 °C) allows it to be used for hot water supply and heat supply. In the climatic conditions of Russia, such functionality is of great importance. Evidence of this is the data on the annual consumption of natural gas for the production of electricity and heat, which is ~ 135 and 200 billion m 3 , respectively.

MGR-100 GT can be operated in two modes: in the mode of electricity production only and in the combined mode of electricity generation and municipal heat supply due to waste heat recovery. Thus, in addition to a higher efficiency of electricity generation, MGR-100 GT provides a potential opportunity to obtain a heat utilization factor of about 99%.

When the plant is operating in combined mode, waste heat is removed to the heat carrier of the network circuit in network heat exchangers. In power-only mode, the grid loop is turned off and waste heat is removed to the outside air in fan dry coolers.

circuit diagram MGR-100 GT is shown in Fig. 2. The required temperature of the network water supplied to the consumer (150 ºС) is provided by reducing the flow rate and increasing the pressure in the WPT cooling water circuit. In order to prevent, in the combined mode, the helium temperature at the heat exchanger inlet from exceeding the permissible limits (600 °C), a bypass branch with a controlled helium bypass of the primary circuit was organized in addition to the heat exchanger on the HP side (from the HPC outlet to the heat exchanger outlet on the HP side).

Fig.2. Schematic diagram of MGR-100 GT

The main parameters of the MGR-100 GT in the mode of power generation and public heat supply are shown in Table 2. In the combined mode, the electric power of the plant will be 57 MW, and the thermal power removed by the network water will be 154 MW.

The cost of generated electricity, taking into account beneficial use waste heat for domestic heating purposes is almost halved compared to the option of operation in the mode of electricity generation only. At the same time, one should take into account economic effect from the exclusion of thermal emissions into the environment.

2.2 Energy sources MGR-100 VEP and MGR-100 PKM for hydrogen production

The transition to a hydrogen economy is based, among other things, on the creation of a technology for using HTGR energy in hydrogen production processes that have high thermodynamic and technical and economic efficiency. These processes, if possible, should exclude the consumption of fossil fuels, primarily oil and gas, which have limited reserves and are a valuable raw material for industry. These processes include the production of hydrogen from water using the following main methods: electrolysis, thermochemical decomposition, and high-temperature steam electrolysis. Their cost does not depend on the ever-increasing prices for oil and gas, in contrast, for example, to the production of hydrogen from methane. At the same time, for the first stage of the development of hydrogen energy, while still relatively low prices on gas, the processes of obtaining hydrogen from methane are considered. An analysis of the requirements for the efficiency of the production of consumed energy and the level of heat temperature allows us to formulate the requirements for HTGR as an energy source, the main of which are:

Production of high-potential heat up to 950 °С;

No contamination of hydrogen with radioactive substances or their acceptable low level;

Low cost of hydrogen production compared to traditional methods;

High level of security of the energy technology complex.

The following are considered as the main hydrogen production processes at the stage of conceptual development of MGR-100:

High temperature electrolysis of water;

Steam reforming of natural gas (methane).

circuit diagram MGR-100 VEP for the production of electricity and superheated steam of the required parameters in order to obtain hydrogen by high-temperature electrolysis is shown in Fig. 3.

The MGR-100 VEP variant is based on the RP configuration with a parallel arrangement of heat exchange loops in the primary circuit. One loop includes the reactor, the steam generating unit and the GCH. The other is the reactor and WPT. Thus, part of the thermal energy (~10%) generated in the reactor core is transferred to the PGB for the needs of hydrogen production, the rest is converted into WPT in electrical energy in a direct gas turbine cycle.

Rice. 3. Schematic diagram of MGR-100 VEP

The main parameters of the installation are given in Table 3. The temperature of helium at the outlet of the reactor is 850 °C, which does not exceed the corresponding temperature in the GT-MGR prototype reactor plant. The second circuit is designed to produce superheated steam in the steam generator (Fig. 4). Helium circulation in the PGB is carried out by the main circulation blower. Water is supplied and steam is removed through the SG cover. Superheated to the required parameters, steam is discharged through pipelines to a high-temperature electrolysis unit based on solid oxide electrochemical cells, in which water vapor decomposes into hydrogen and oxygen with the separation of these reagents. The WEP installation is supplied with electricity generated by the WPT generator.

circuit diagram MGR‑100 PKM for the generation of high-potential heat in order to obtain hydrogen by the method of steam reforming of methane is presented in Fig.5.

Steam reforming of methane is currently the main industrially mastered and adapted for the first stage of the introduction of hydrogen production technologies (together with HTGR) process. It is based on the existing world production of hydrogen. The combination of HTGR and PCM makes it possible to reduce the consumption of natural gas by about 40%, and, consequently, the costs required for the production of hydrogen. Economic efficiency implementation of PCM is determined by the price of gas and the temperature of the consumed heat. The required heating temperature of the gas-vapor mixture should not be lower than 800 C, and a further increase in temperature has practically no effect on the efficiency of the process.

Fig.5. Schematic diagram of MGR-100 PKM

Thermal energy is removed from the reactor to the working medium of the secondary circuit (vapor-gas mixture) in high-temperature heat exchangers (HTO), which are an integral part of the thermoconversion apparatus (TKA). The implementation of the conversion of methane (CH 4 +H 2 0 (steam) + heat→CO 2 +4H 2) occurs in the TKA according to a three-stage scheme. The vapor-gas mixture (steam - 83.5%, CH 4 - 16.5%) is fed sequentially in three stages - TKA1, TKA2 and TKA3. This determines the configuration of the heat transfer unit of the reactor plant. It consists of three separate high-temperature heat exchangers VTO 1, VTO 2, VTO 3 (Fig. 6), representing separate stages (sections) of the block. The location of the WTO sections along the primary coolant flow is parallel, along the gas-vapor mixture flow is sequential.

After TKA-3, the gas-vapor mixture (steam-55%, CH 4 , H 2 , CO, CO 2 - 45%) with a high hydrogen concentration sequentially passes the CO 2 and H 2 O purification unit and is sent to the hydrogen separation unit. return fraction and natural gas mixed with superheated steam and then sent to the TKA. The circulation of helium in the primary circuit is carried out by the GCH, the vapor-gas mixture is circulated by compressors.

The main parameters of the installation are given in Table 4. The helium temperature at the outlet of the reactor is 950 ºС.

Depending on the type of layout (loop or block) of the main equipment of the switchgear, the configuration of the heat transfer unit may be different. In a block arrangement, the main equipment of the reactor plant is connected using short pipes of the "pipe in pipe" type; it is advisable to include the MCH in the heat transfer unit as well.

2.3 Energy source MGR‑100 refinery for petrochemical production

MGR-100 refinery is designed to generate high-grade or medium-grade heat to meet the technological needs of petrochemical production (heating of network heat carriers), which will save about 14% of processed oil. The design base for it was developed in Russia in the 80s preliminary design a modular reactor with a core of spherical fuel rods and a helium outlet temperature of 750 °C. The project was focused on process heat generation based on the requirements of a typical refinery.

Fig.7. Schematic diagram of MGR-100 refinery

A schematic diagram of the MGR-100 refinery is shown in Fig.7. Helium circulation in the primary and secondary circuits is forced and is carried out by circulation blowers. The working medium of the network circuit is nitrite-nitrate salt. The main parameters of the installation are shown in Table 5.

The main consumers of refinery heat (~50% of the thermal power of the reactor) are tubular furnaces designed for thermal catalytic oil refining. According to the level of heating of petroleum products in furnaces, oil refining processes are divided into three types: low-temperature (up to 400 °C), medium-temperature (up to 550 °C) and high-temperature (up to 900 °C). The heat from the MGR-100 refinery is also used to cover the needs of the refinery in process steam (~35% of the thermal power of the reactor) and electricity (~15% of the thermal power of the reactor).

The heat transfer unit consists of an intermediate heat exchanger (PHE), GCH, internal metal structures (VKM).

PHE (Fig. 8) consists of a pipe system, a set of channels (37 pcs), collecting chambers of “hot” helium of the intermediate circuit, elements of their fastening and sealing. The main circulating gas blower is mounted in the lower part of the PHE body.

3 Issues of concern

Within the framework of the completed projects, a schematic configuration and a 3-D layout of installations were developed, the parameters of the circuits and characteristics of the main equipment were determined, a calculation justification of the main components of the structure, an analysis of operational and emergency modes were carried out, preliminary analysis cost of creation and construction of reactor facilities, stages and plans of R & D are determined. Most of the required R&D, including for the reactor, turbomachine and its components, recuperator, preliminary and intermediate coolers, VKM, is currently being carried out in the scope of technological developments of GT-MGR and MGR-T reactors.

The main issues requiring additional R&D are:

Development of manufacturability of high-temperature heat exchangers;

Justification of the safety of reactor facilities for hydrogen production;

Development of RP power control algorithms together with process control systems;

Carrying out attestation tests of heat-resistant metallic materials.

One of the main restrictions on increasing the helium temperature at the reactor outlet is the maximum allowable temperature for long-term operation of the VKM reactor. With an increase in the helium temperature at the core inlet to 600 °C, in order to achieve an acceptable temperature of the reactor vessel material (~350 °C), it is planned to refine the core design in terms of heat removal to the reactor vessel cooling system.

Serious requirements are imposed on gas ducts transporting a heated process medium with a temperature of up to 900 ° C, which should not decrease due to heat losses, since the efficiency of the process depends on the temperature level.

Hydrogen production is a potential source of explosion hazard. When analyzing the safety of MGR-100, accidents in the technological part of the plant or at industrial sites should be considered as initial events. In these accidents, the release of technological raw materials or processed products is possible. From a protective action point of view, the worst possible safety implications may be due to blast effects following the explosion of these products.

One of the safety criteria should be taken not to exceed the maximum release of explosive mixtures in technological production. The amount of release is determined by the allowable value of excess pressure in the front of the shock wave, adopted for the containment, systems and elements of the NPP.

When analyzing such accidents, one should consider both scenarios with the possibility of an explosion in the immediate vicinity of the reactor, and ensuring safety due to the spatial separation of the nuclear and technological parts.

4 Conclusion

The development of MHR technology in Russia from the very beginning was aimed at using nuclear energy not only for electricity generation, but also for industrial heat supply as an alternative to using fossil fuels.

The technology of modular HTGR, due to the unique properties of efficiency, safety and environmental friendliness, can provide an integrated energy supply with electricity, heat and fuel, including actual problem cost-effective hydrogen production.

HTGR-based low-capacity nuclear power plants, which are environmentally safe and require little construction and maintenance costs, can become important elements of the nuclear power infrastructure of the current century.

The design and experimental work completed to date on the variants of modular MGR-100 for various power engineering applications confirms the possibility of meeting the requirements for new generation reactor plants.

Development of HTGR power technology based on MGR-100 will significantly reduce total costs under the HTGR program and demonstrate the possibilities and benefits for the further commercialization of this technology.

Bibliography

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2. Energy strategy of Russia for the period up to 2030. Approved by the order of the Government of Russia dated November 13, 2009 No. 1715

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7. High temperature gas cooled reactor – source of energy for commercial production of hydrogen. Mitenkov F.M., Kodochigov N.G., Vasyaev A.V., Golovko V.F., Ponomarev-Stepnoy N.N., Kukharkin N.Ye., Stolyarevsky A.Ya. - Nuclear power, vol. 97, issue 6, December 2004, p. 432-446.

Russia and the United States are jointly developing a project for a nuclear power plant of the future. It will significantly surpass all previous systems in terms of safety, efficiency, and many other parameters. Nuclear power has not yet said its last word.

Despite the growth in the use of solar panels, wind and wave energy, and other alternatives, we will not get away from the “classical” energy in the coming decades. And here, perhaps, the most environmentally friendly is, oddly enough, nuclear energy.

Yes, recycling nuclear fuel is a difficult problem, but not at all hopeless. Read about some projects: real and already going, but more fantastic.

We will talk about the danger of accidents at nuclear power plants below. But if they do not exist - the nuclear power plant does not seem to exist - its emissions are zero.

But thermal power plants poison the atmosphere with millions of tons of poisons and greenhouse gases. And radioactive substances, too, by the way, which are contained, say, in coal and get into the chimney with the exhaust of the station.

Hydroelectric plants seem to be clean. But you can’t put them everywhere, and reservoirs, by the way, irreversibly change nature for many tens of kilometers around, affect the habitat of thousands of species, put enormous pressure on the earth’s crust (which is not very great in seismic zones).

Nuclear fusion? Yes, there are interesting options (not ITER), but this is for the future. And in the coming years, the circle seems to close - we will "burn" uranium. For example, in a super-nuclear power plant, developed jointly by Russia and the United States.

The new NPP scheme eliminates many of the old systems from its design. And since there are fewer nodes, the reliability is higher (illustration from the site gt-mhr.ga.com).

On the American side, the main participant in the project is General Atomics, and on the Russian side, the Experimental Design Bureau of Mechanical Engineering named after I. I. Afrikantov (OKBM) in Nizhny Novgorod, subordinate to the Federal Atomic Energy Agency of the Russian Federation.

Minatom and started cooperation with the Americans on this project back in 1993. And by now, a draft design of the reactor (and station) has been developed, and much more detailed developments have long been in full swing.

And since specialists see the future of nuclear energy in a new type of nuclear power plant, let's get to know how it will work.

This system is called Gas Turbine - Modular Helium Reactor (GT-MHR), and in Russian - "Gas Turbine - Modular Helium Reactor" - GT-MHR.

There are two main ideas here. A nuclear reactor cooled by gaseous helium and with inherent safety (that is, the stronger the heating, the weaker the reaction, simply based on the "physics" of the reactor, up to a natural shutdown, without any participation of the control system) and - the shortest conversion of hot helium energy into electricity - with the help of a gas turbine of the so-called closed Brayton cycle, with the placement of a turbogenerator and a reactor in closed capsules underground.

No extensive pipes, pumps, turbines, and masses of other pieces of iron above the surface. The design of a nuclear power plant is greatly simplified.

Dozens of systems disappear by magic. No intermediate phase-changing coolants (liquid-steam), no bulky heat exchangers, almost no way for a possible leakage of something radioactive.

Everything is encapsulated. In this case, even the failure of the control system does not lead to fuel melting. Everything automatically damps and slowly cools down due to heat dissipation into the ground surrounding the station.

The fuel for the station is uranium oxide and carbide or plutonium oxide, made in the form of balls with a diameter of only 0.2 millimeters and covered with several layers of various heat-resistant ceramics. Balls are “poured” into rods, which form an assembly, and so on.

The physical (mass of the structure, reaction conditions) and geometrical parameters of the reactor are such (comparatively low energy density, for example) that in any event, even a complete loss of coolant, these balls will not melt.

Yes, and the entire core is made of graphite - there are no metal structures here at all, and the heat-resistant alloy is used only in the outermost case - the capsule.

So even if all the station staff together “leave to drink beer”, nothing terrible will happen to the environment - the temperature in the heart of the nuclear power plant will jump to a maximum of 1600 degrees Celsius, but the core will not melt. The reactor itself will begin to cool, giving off heat to the surrounding soil.

Scheme of the "heart" of the station. On the left is a turbine with an electric generator and heat exchangers, on the right is a reactor (illustration from gt-mhr.ga.com).

The use of helium as a coolant promises a number of advantages. It is chemically inert and does not cause corrosion of components. It does not change its state of aggregation. It does not affect the neutron multiplication factor. Finally, it is convenient to direct it into the gas turbine.

It is encapsulated together with pumps and heat exchangers and rotates exclusively on axial and radial electromagnetic bearings - rolling bearings are provided as emergency ones.

Special mention must be made of heat exchangers. The helium that cools the reactor makes several “loops” in the turbine plant, giving its energy to the turbogenerator as much as possible. In addition, there is additional cooling of helium with water, but in the event of an accident, the system will do without it at all, the reactor will not melt.

The result of all these innovations is station efficiency- up to 50%, against 32% for existing nuclear power plants, plus - a much more complete production of nuclear fuel (which means less irradiated uranium and less high-level waste per megawatt-hour of energy received), simplicity of design, which means less cost of construction and easier control over work.

And, of course, safety. The Americans write that the GT-MGR is the first nuclear power plant in the world that will meet the first level of safety.

There are 4 of them, of which zero is the highest. 0 is fantastic. Nothing can ever happen here, and in general - no hazardous materials. The first level is the highest possible level. With it, nuclear power plants, in theory, do not require special safety systems, since the reactor itself has an internal, structurally predetermined "immunity" from any operator errors and technical damage.

The station in Chernobyl had, according to the Americans, the third (worst) level of safety, which means the criticality of the system to human errors or equipment failure. Now many operating stations have reached the level of safety "2".

OKBM writes that “The strategy for the development of nuclear energy in Russia provides for the construction of the GT-MGR head nuclear power plant and a fuel production unit for it at the Siberian Chemical Plant (Seversk, Tomsk Region) by 2010, and by 2012-2015 - the creation and commissioning the first four-module NPP GT-MGR.

Helium circulation diagram (illustration from gt-mhr.ga.com).

The Americans, in turn, provide interesting details: since the GT-MGR can consume not only uranium, but also weapons-grade plutonium, such nuclear power plants become an ideal device for its disposal, not only safe, but also profitable in a certain sense. For example, Seversk will (partially, of course) provide itself with electricity from "reduced" Russian warheads.

And plutonium, which will be unloaded from the reactor after "work", according to its parameters, is completely unpromising for hypothetical use in nuclear weapons, which is also good for world security.

But the United States is also interested in the project - the high thermal efficiency of the "helium reactor - closed gas turbine" link is a huge benefit, both in terms of economy and environmental safety.

It should be added that the thermal power of one such installation will be 600 megawatts, and the electric one - 285 megawatts.

The estimated service life of the GT-MHR is 60 years. Will they have time to develop industrial fusion reactors by that time, or will alternative energy become really mass?

Objectives of the GT-MGR project

• Creating a plant that meets the requirements of 21st century technology in terms of safety, competitiveness and minimization of environmental impact.
• Commissioning of the first GT-MGR unit no later than 2023 with minimization of R&D by using the accumulated world experience in HTGR technology.
• Use of the first and several subsequent units to burn excess weapons - grade plutonium .
• Creation of a base for the subsequent commercial application of this technology for the production of electricity and heat for domestic and industrial needs, including the production of hydrogen.

Design features

Fuel rods are microspheres of plutonium oxide, uranium oxide or nitride with a diameter of 0.2-0.5 mm in a multilayer shell of pyrolytic carbon and silicon carbide. In accordance with design calculations, such a microfuel element is capable of effectively retaining fission fragments both under normal operating conditions (1250 0 С) and under emergency conditions (1600 0 С).

Both modules of the reactor plant are located in vertical reinforced concrete shafts below ground level.

Main technical characteristics

Advantages

• High efficiency;
• Simplification of the design of nuclear power plants due to the modular design of the reactor;
• The use of fuel in the form of microparticles with a multilayer ceramic coating makes it possible to efficiently retain fission products at high burnup rates (up to 640 MW day/kg) and temperatures (up to 1600 °C);
• The use of an annular core with a low power density makes it possible to carry out the removal of residual heat from the reactor using natural air circulation methods;
• Multiple redundancy of control and protection systems;
• The use of helium as a coolant, a substance that is chemically inert and does not affect the balance of neutrons;
• The project also provides for the possibility of disposing of weapons - grade plutonium . One GT-MGR unit, consisting of four reactors, is capable of processing 34 tons of this substance during its operation. In accordance with the design documentation, such irradiated fuel can be disposed of without additional processing.

Flaws

• Low power. To replace one VVER-1000 unit, four GT-MGR units are required. This drawback is caused, on the one hand, by the use of a gas coolant, which has a low heat capacity compared to water or sodium, and, on the other hand, by the low energy intensity of the core as a result of meeting increased reactor safety requirements. This feature casts doubt on the arguments about simplifying the design of NPPs with GT-MHR;
• Education a large numberβ-active carbon 14 C , for which there are no acceptable methods of disposal, and the reserves accumulated during the operation of RBMK reactors are already quite large. When released into the environment, 14 C tends to accumulate in living organisms;
• Lack of an acceptable scheme for reprocessing and disposal of spent fuel. The processing of substances containing silicon is very difficult for chemical technology. Thus, once fuel enters the reactor, it will be permanently removed from the nuclear fuel cycle.
• Currently there is no completed industrial technology production of fuel elements from plutonium, which is associated with its extremely complex chemistry. Establishing such a production requires capital investments comparable or even exceeding investments in uranium processing in the history nuclear industry. Therefore, the statement about the use of GT-MHR for the disposal of weapons-grade plutonium looks rather doubtful. At the same time, it should also be taken into account that only about 400 tons of plutonium have been accumulated in the world, i.e., it can be enough for life cycle a total of 10 power units (4 reactors each).
• The use of helium as a coolant, because in the event of an accident associated with depressurization of the reactor, the entire coolant will inevitably be replaced by heavier air.

Main stages

• 1995-1997 - conceptual design.
• 2000-2002 - preliminary design.
• 2003-2005 - technical project.
• 2005-2008 - commissioning fuel production for the prototype module.
• 2009-2010 - commissioning of the GT-MGR prototype module.
• 2007-2011 - commissioning of fuel production for the 4-module power unit AS GT-MGR.
• 2012-2015 - commissioning of a 4-module power unit AS GT-MG

At the moment there are more detailed developments of the project.