Emergency cooling system for blanket module of tokamak-based fusion neutron source

Abstract

FIELD: thermonuclear technology.SUBSTANCE: invention relates to an emergency cooling system for a blanket module of a thermonuclear neutron source based on a tokamak. The system consists of a water supply pipeline to the blanket module, a blanket module, a water discharge pipeline from the blanket module, a circulation pump and a steam generator, which form a circulation loop. The tokamak is installed in a water cryostat, consisting of two shells – internal and external. The blanket module is designed in the form of a vertically installed Field tube, consisting of two coaxial cylindrical bodies. The inner casing is filled with heat-generating elements cooled by a flow of water from the water supply pipeline of the standard cooling system, supplied from above into the space between the outer and inner casings. Water is also drained into the water drainage pipeline from above, which guarantees the presence of water in the module in the event of a rupture in the circulation circuit pipelines.EFFECT: long-term and reliable provision of emergency cooling of the blanket module in the event of an accident with a failure of the standard cooling system and the prevention of melting of the fuel elements in it.1 cl, 2 dwg, 1 tbl

Description

[0001] The invention relates to thermonuclear technology, namely to a system for emergency cooling of a blanket module of a thermonuclear neutron source based on a tokamak.

[0002] Reliable and safe operation of a tokamak-based fusion neutron source must be ensured at the design stage, as a tokamak-based fusion neutron source is a nuclear system containing fuel elements with radioactive isotopes that produce residual heat in blanket modules. Consequently, one of the main challenges encountered during blanket module design is ensuring its reliable cooling in the event of an accident involving failure of the standard cooling system and preventing melting of the fuel elements. It is assumed that the blanket module will be cooled by pressurized water.

[0003] Based on many years of operating experience of nuclear reactors cooled by pressurized water, the main reasons for failure of the standard cooling system of the blanket module can be:

[0004] - rupture of the coolant circulation circuit of the blanket module and its leakage (LOCA type accident);

[0005] - stop of the coolant circulation system pumps due to a long-term loss of power supply (LOFA type accident);

[0006] - failure of systems for removing thermal energy into the environment.

[0007] The design of a thermonuclear neutron source based on a tokamak, hereinafter referred to as “classical”, is described in A.B. Alekseev et al., ed. V.A. Glukhikh and G.L. Saksagansky, “Fundamentals of Designing Magnetic Thermonuclear Reactors”, St. Petersburg, Publishing House of the Polytechnic University, 2016, p. 37.

[0008] The elements of the "classical" design of a tokamak-based fusion neutron source include a toroidal vacuum chamber with inner and outer shells. The inner shell of the vacuum chamber encloses an internal cavity within which a vacuum is maintained. A first wall and a divertor are installed within the inner cavity, defining the volume containing the plasma. Blanket modules are installed between the first wall and the inner shell of the vacuum chamber. Toroidal and poloidal field coils are installed outside the vacuum chamber and generate a magnetic field that confines the plasma.

[0009] The blanket module has a housing, typically cylindrical, installed in the space between the first wall and the inner shell of the vacuum vessel. The blanket module housing contains fuel elements with feedstock for either fissile fuel production, tritium production from lithium-containing materials, or minor actinide transmutation. Fuel elements can generally have any shape. Cooling of the blanket module during normal reactor operation is achieved by pumping water through its housing using the standard cooling system. Water is supplied through a nozzle at one end of the blanket module to cool the fuel elements and is discharged through a nozzle at the other end.

[0010] In the event of failure of the standard cooling system, the blanket module is cooled by an emergency cooling system: water is supplied from a hydraulic tank, where it is under compressed gas pressure, directly into the blanket module body.

[0011] The blanket module design described above is called "straight-through." In the "classic" design of a thermonuclear neutron source, the blanket module is straight-through. In the event of a failure of the standard cooling system, the blanket module is cooled by an emergency cooling system: water is supplied from a hydraulic accumulator, where it is kept under compressed gas pressure, directly into the blanket module body.

[0012] A design concept for a tokamak with a "water" cryostat is known, proposed in the article by D.P. Ivanov, D.K. Kurbatov, A.Yu. Pashkov. "Analysis of Possible Accidents in the ITER Cryostat". Issues of Atomic Science and Technology, Thermonuclear Fusion Series, 1996, Issue 1, pp. 3-18. The "water" cryostat, which serves as biological protection, consists of two metal shells - an inner and an outer one. The inner shell has a cylindrical side part, to which a bottom and a round lid are welded. The outer shell also has a cylindrical side part and a round bottom welded to it. The space between the inner shell, the outer shell, and the lid forms the cryostat body volume, partially filled with water. A vacuum is maintained under the inner shell of the cryostat.

[0013] However, the disadvantage of this design scheme is that the water in the cryostat body volume is used only as biological protection.

[0014] A passive heat removal system for a WWER-type nuclear power plant is known, disclosed in document RU 2073920 C1, published 20.02.1997, which includes a first circulation circuit consisting of a reactor connected by pipelines to steam generators, which is enclosed in a protective shell made of two shells installed with a gap between them, and the gap between the shells is filled with water.

[0015] A disadvantage of the proposed design, according to the authors, is that water from the gap between the protective shells is used only to condense steam generated in the steam generators during a complete power outage of the nuclear power plant, when the pumps of the primary circulation circuit and the feed pumps of the steam generators are turned off, and is not used in a LOCA-type accident with loss of coolant in the primary circulation circuit.

[0016] In light of the above, the authors believe that a “water” cryostat can be used for emergency cooling of a blanket module, and the design scheme of the cryostat is close in a set of essential features to the claimed invention and is considered by the authors as a prototype of the claimed invention.

[0017] The technical problem that the claimed invention is aimed at solving is the impossibility of ensuring long-term and reliable cooling of the blanket module of a thermonuclear neutron source in the event of a LOCA-type accident.

[0018] The technical challenge was to create an emergency cooling system for the blanket module that would allow for emergency cooling of the blanket module over a long period of time without any active actions by personnel, which would help prevent the melting of the fuel elements in it.

[0019] The technical result consists in long-term and reliable provision of emergency cooling of the blanket module in the event of an accident with a failure of the standard cooling system and preventing the melting of fuel elements in it, thereby ensuring an increase in the safety of a tokamak-based thermonuclear neutron source in the event of a LOCA-type accident.

[0020] The stated problem is solved, and the technical result of the claimed invention is achieved, by means of an emergency cooling system for a blanket module of a tokamak-based thermonuclear neutron source, comprising a water supply pipeline to the blanket module, a blanket module, and a water drainage pipeline from the blanket module. The blanket module is installed inside the vacuum chamber of the thermonuclear neutron source, outside of which a cryostat is installed, having an internal vertical side wall and an internal upper horizontal wall, as well as an external vertical side wall and an external upper horizontal wall. The aforementioned walls of the cryostat form an internal volume of the cryostat, which is partially filled with water in such a way that an air cavity is formed above the water surface. The internal volume of the cryostat is connected by means of an emergency water supply pipeline of the cryostat to the water supply pipeline to the blanket module through the first check valve.The blanket module is designed as a vertically mounted heat exchanger consisting of two coaxial tubes, thus forming an outer and an inner tube. The outer tube is closed at its lower end and forms the outer casing of the blanket module, while the inner tube is open at its upper and lower ends and forms the inner casing of the blanket module. A lower grate is installed at the lower end of the inner tube, and an upper grate is installed at the upper end of the inner tube, holding spherical heat-generating elements within the inner casing of the blanket module. Furthermore, a first shut-off valve is installed on the water supply pipeline to the blanket module, and a second shut-off valve is installed on the water outlet pipeline from the blanket module. The water outlet pipeline from the blanket module is connected by a steam outlet pipeline to a steam discharge pipeline into the air cavity through a second check valve.

[0021] Thus, the combination of essential features of the claimed invention will ensure long-term cooling of the blanket module in the event of failure of the standard cooling system.

[0022] The "water" cryostat, hereinafter referred to simply as the cryostat, consists of two metal shells—an outer and an inner shell. Each shell has a vertical side wall to which the corresponding outer and inner horizontal walls are welded. The metal shells are mounted on a concrete foundation. The space between the inner shell, the outer shell, and the concrete foundation forms the cryostat's internal volume, which is partially filled with water. The upper portion of the cryostat's internal volume—under the upper horizontal wall of the cryostat's outer shell—is not filled with water and forms an air cavity at atmospheric pressure to compensate for the thermal expansion of the water. The air and water in the cryostat's internal volume are at room temperature.

[0023] The cryostat performs the following functions:

[0024] - serves as biological protection;

[0025] - ensures maintenance of vacuum under the inner shell;

[0026] - reduces heat flows to superconducting electromagnetic coils that have cryogenic temperatures.

[0027] In the normal operation mode of the tokamak-based thermonuclear neutron source, the standard cooling system operates, including a water circulation circuit consisting of a water supply pipeline to the blanket module, the blanket module itself, a water discharge pipeline from the blanket module, a circulation pump and a steam generator.

[0028] Water under pressure from the circulation circuit enters the blanket module body through the supply pipeline, cooling it and the spherical fuel elements within. A circulation pump provides water movement. From the blanket module body, the circulation pump delivers water through the return pipeline to the steam generator, where thermal energy is transferred to the secondary circuit water. The circulation circuit water then returns to the blanket module through the supply pipeline. Shut-off valves are installed on the return and supply pipes; they are open during normal operation. In the event of an emergency involving a rupture of any circulation circuit pipeline (LOCA type emergency) and the pressure in the circulation circuit pipelines drops below a certain value, called the trip point, the shut-off valves close. This is necessary for the successful operation of the blanket module's emergency cooling system.

[0029] In the event of an accident with loss of water from the circulation circuit and the cessation of cooling of the blanket module by the standard cooling system, water is supplied to it from the internal volume of the cryostat.

[0030] One of the distinguishing features of the present invention is that the blanket module is designed as a vertically mounted "Field tube." A "Field tube" is a heat exchanger consisting of two coaxial cylindrical tubes inserted one inside the other, thus forming an outer and inner tube. The outer tube is closed at the lower end (dead-end) and forms the outer casing. The inner tube is open at the upper and lower ends and forms the inner casing filled with spherical fuel elements. A lower grid is installed at the lower end of the inner tube, and an upper grid is installed at the upper end of the inner tube, which hold the spherical fuel elements in the inner casing of the blanket module. Spacers are installed in the inter-casing space between the inner and outer casings of the blanket module and maintain their relative position.

[0031] Water enters the blanket module's inlet, located at the top of the blanket module, and flows down the inter-case annular space. It turns at the dead-end end and then flows through the lower grid up the inner case, cooling the spherical fuel elements within. The water then passes through the upper grid and through the outlet, located at the top of the blanket module, into the blanket module's water drainage pipeline. Water supply and drainage are carried out from the upper end of the blanket module.

[0032] This design allows, in the event of a rupture in the circulation circuit pipelines and the leakage of water from them, to save a certain volume of water - in the blanket module. However, complete water loss is only possible if the outer casing of the blanket module ruptures.

[0033] In the event of a water loss from the circulation circuit and the module's cooling system being interrupted, cooling is provided by supplying water from the cryostat's internal volume to the module's housing. During the failure, the water is heated by residual heat generated in the fuel elements, then evaporates, and the vapor is released back into the cryostat's internal volume.

[0034] Brief description of drawings

[0035] The proposed invention is illustrated by figures 1 and 2, in which the following are designated by positions:

[0036] 1 - blanket module;

[0037] 2 - first wall;

[0038] 3 - vacuum chamber;

[0039] 4 - circulation pump;

[0040] 5 - supply pipeline;

[0041] 6 - inlet pipe;

[0042] 7 - outlet pipe;

[0043] 8 - outlet pipeline;

[0044] 9 - steam generator;

[0045] 10 - concrete base;

[0046] 11 - first shut-off valve;

[0047] 12 - second shut-off valve;

[0048] 13 - internal side vertical wall of the cryostat;

[0049] 14 - inner upper horizontal wall of the cryostat;

[0050] 15 - external side vertical wall of the cryostat;

[0051] 16 - outer upper horizontal wall of the cryostat;

[0052] 17 - metal structure;

[0053] 18 - cryostat water;

[0054] 19 - air cavity;

[0055] 20 - cryostat water surface;

[0056] 21 - cryostat emergency water supply pipeline;

[0057] 22 - first check valve;

[0058] 23 - steam outlet pipeline;

[0059] 24 - second check valve;

[0060] 25 - steam discharge pipeline;

[0061] 26 - heat exchanger for cooling cryostat water;

[0062] 27 - location of rupture in the supply pipeline;

[0063] 28 - outer casing of the blanket module;

[0064] 29 - inner body of the blanket module;

[0065] 30 - inter-body volume of the blanket module;

[0066] 31 - spacer fastening of blanket module housings;

[0067] 32 - lower grille;

[0068] 33 - spherical fuel element;

[0069] 34 - upper grille.

[0070] Figure 1 shows the standard cooling system of the blanket module (before the LOCA type accident), as well as the system for emergency cooling of the blanket module of the thermonuclear neutron source based on a tokamak using a cryostat with the discharge of steam back into it.

[0071] During normal operation of the tokamak-based thermonuclear neutron source, the standard cooling system operates, where the circulation pump 4 of the standard cooling system supplies circulation circuit water through the feed pipe 5 to the inlet pipe 6 of the blanket module and then to the blanket module 1. The blanket module 1 is installed in the space between the first wall 2 of the tokamak and the vacuum chamber 3. The movement of water in the blanket module body will be described below. Then, the circulation circuit water enters the outlet pipe 8 of the blanket module through the outlet pipe 7 connected to the branch pipe 8 and then to the steam generator 9. The first shut-off valve 11 is installed on the feed pipe 5. The second shut-off valve 12 is installed on the branch pipe 8.

[0072] The tokamak with the blanket module 1 is located inside the cryostat, wherein the tokamak and the cryostat are installed on a concrete base 10. The inner shell of the cryostat has an inner side vertical wall of the cryostat 13 and an inner upper horizontal wall of the cryostat 14, which are connected to each other by welding. The outer shell of the cryostat has an outer side vertical wall of the cryostat 15 and an outer upper horizontal wall of the cryostat 16, which are also connected to each other by welding. The outer and inner shells of the cryostat are connected by metal structures 17 for rigidity and strength. The inner and outer shells of the cryostat and its concrete base 10 limit the internal volume of the cryostat, which is partially filled with cryostat water 18 at ambient temperature.The portion of the cryostat's internal volume beneath the outer upper horizontal wall 16 is not filled with water and forms an air cavity 19 at atmospheric pressure to compensate for the thermal expansion of cryostat water 18. The cryostat's internal volume is filled with water prior to operation. During this time, air cavity 19 is exposed to the atmosphere, and atmospheric pressure is established within it. Before operation, air cavity 19 is sealed, maintaining atmospheric pressure within it. The boundary between cryostat water 18 and air cavity 19 is formed by the surface of cryostat water 20.

[0073] The emergency water supply pipeline of cryostat 21 is connected at one end to the internal volume of the cryostat below the water surface of cryostat 20, and its other end is connected to supply pipeline 5. A first check valve 22 is installed on the emergency water supply pipeline of cryostat 21. A steam discharge pipeline 23 of the emergency cooling system of the blanket module is connected to outlet pipeline 8, on which a second check valve 24 is installed, to which a steam discharge pipeline 25 is connected, the open end of which exits into the air cavity 19 above the water surface of cryostat 20. In normal operation mode, steam discharge pipeline 23 of the emergency cooling system of the blanket module is filled with water. A heat exchanger 26 is installed in the cryostat water for cooling the water of cryostat 18 in normal operation mode.

[0074] It is further assumed that in the event of an accident, a rupture of supply pipeline 5 will occur at the location of the rupture of supply pipeline 27.

[0075] Figure 2 shows a vertical section of a blanket module, which is made in the form of a vertically installed heat exchanger, consisting of two coaxial cylindrical tubes inserted into each other, thus forming an outer and an inner tube, wherein the outer tube is closed at the lower end (dead-end) and forms the outer casing of the blanket module 28, and the inner tube is open at the upper and lower ends and forms the inner casing of the blanket module 29, filled with spherical fuel elements 33. A lower grid 32 is installed at the lower end of the inner tube, and an upper grid 34 is installed at the upper end of the inner tube, which hold the spherical fuel elements 33 in the inner casing of the blanket module.

[0076] In the inter-body volume of the blanket module 30, several spacer fasteners of the blanket module 31 bodies are installed, supporting the relative positioning of the outer body of the blanket module 28 and the inner body of the blanket module 29. Each spacer fastener of the blanket module 31 bodies is designed as a cylindrical segment, the outer diameter of which coincides with the inner diameter of the outer body of the blanket module 28, and the inner diameter coincides with the outer diameter of the inner body of the blanket module 29. The height of the segment is 0.02-0.03 m, while the segments have the same length. Therefore, the spacer fasteners do not divide the inter-body volume of the blanket module 30 into separate compartments, and when water enters the inter-body volume of the blanket module 30 through the inlet pipe 6, it will be completely filled.

[0077] During both normal operation and emergency cooling of the blanket module, water flows through inlet pipe 6 of the blanket module into the inter-case volume of blanket module 30 (the direction of water flow is shown by arrows), then through lower grate 32 into the inner casing of blanket module 29, which is filled with spherical fuel elements 33, and cools them. Water then exits blanket module 1 through upper grate 34 and outlet pipe 7 of the blanket module into water discharge pipeline 8. The grates retain spherical fuel elements 33 in the inner casing of module 29, but do not impede the flow of water there.

[0078] Initial data and assumptions

[0079] The blanket module housings 1 have the following dimensions. The outer housing of the blanket module is 228 × 4 mm in diameter and 3 m in length; the inner housing of the blanket module is 210 × 5 mm in diameter and 2.9 m in length.

[0080] V BH- internal volume of the inner body of the blanket module - 9.5⋅10 -2 m 3 .

[0081] Volume of the part of the internal volume of the inner body of the blanket module filled with water:

[0082]

[0083] where m = 0.4 is the porosity of the spherical backfill of fuel elements.

[0084] Total water volume in the blanket module body:

[0085]

[0086] where

[0087] - inter-hull volume (minus the volume of spacer fasteners) - 4×10 -2 m 3 .

[0088] Water pressure at the inlet to the blanket module is 4 MPa.

[0089] Water temperature at the inlet of the blanket module

[0090] Water temperature at the outlet of the blanket module

[0091] - thermal power of the blanket module at the time of the accident.

[0092] - current thermal power of the blanket module at the moment

[0093] Cryostat parameters. The vertical side wall of both the inner and outer shells of the cryostat are cylindrical.

[0094] Total volume of the internal volume of the cryostat:

[0095]

[0096] where - the radius of the outer side vertical wall of the cryostat is 9 m.

[0097] - the radius of the inner side vertical wall of the cryostat is 7.5 m.

[0098] - the height of the outer side vertical wall of the cryostat is 20 m.

[0099] - the height of the inner side vertical wall of the cryostat is 18.5 m.

[0100] Air cavity volume:

[0101]

[0102] where - radius of the outer side vertical wall of the cryostat - 9 m;

[0103] - thickness of the air layer in the air cavity - 0.3 m.

[0104] We assume that 30% of the cryostat's internal volume is occupied by metal structures, penetrations, diagnostic equipment, etc., and 70% is filled with water. Let's introduce the concept of the water fill factor: Then the total volume of water in the internal volume of the cryostat is:

[0105]

[0106] The distance from the point where the emergency water supply pipeline leaves the cryostat (pos. 21) to the surface of the cryostat water (pos. 20) is h=9.7 m.

[0107] During normal operation, the water in cryostat 18 is heated by neutrons and gamma rays from the plasma. To maintain a stable water temperature of t0 = 20°C, a heat exchanger is used to cool the water in cryostat 26. Cryostat water mass:

[0108]

[0109] where

[0110] - cryostat water density - 1000 kg / m3 3 .

[0111] Maximum water flow through the emergency water supply pipeline of cryostat 21:

[0112]

[0113] where flow rate coefficient ~ 0.75;

[0114] - flow cross-section of the cryostat emergency water supply pipeline (with a pipeline diameter of 20 × 1.5 mm) - 2.27⋅10 -4 m 2 ;

[0115] g - acceleration due to gravity - 9.81 m / s 2 .

[0116] Characteristics of the standard module cooling system

[0117] Required water flow rate G0 when cooling the blanket module in normal operation mode:

[0118]

[0119] where

[0120] - heat capacity of water in a standard cooling system.

[0121] With the given parameters G0=22.2 kg / s, the feed pipeline (pos. 5) has a diameter of D=88×4 mm, the water velocity in it:

[0122]

[0123] where

[0124] - the density of water in the standard cooling system is 865 kg / m3 3 ;

[0125] - flow section of the supply pipeline - 0.005 m 2 .

[0126] With the given parameters w = 5.1 m / s, which is acceptable.

[0127] The system for emergency cooling of the blanket module of the thermonuclear neutron source will operate as follows. In the event of an accident with a rupture of the supply pipeline 5, at the point of rupture of the supply pipeline 27, water from the circulation circuit will begin to leak out with a drop in pressure in the circulation circuit, namely, in the water supply pipeline 5 to the blanket module and in the water outlet pipeline 8 from the blanket module, as well as in the steam outlet pipeline 23 of the emergency cooling system of the blanket module connected to the water outlet pipeline 8 from the blanket module, which is also filled with water, and the second check valve 24 is still closed. The flow of water from the circulation circuit into the inter-case volume of the blanket module 30 and into the inner case of the module 29 will decrease and then stop completely. Due to the proposed design of the blanket module, water cannot leak out of it completely, and the volume of water in it will be at least Under the influence of residual heat generation in the spherical fuel elements 33, the water in the circulation circuit in the blanket module will begin to boil, and the resulting steam and water from the supply pipeline 5 and the outlet pipeline 8 will exit through the rupture point of the supply pipeline 27. This is how the cooling of the spherical fuel elements will be carried out in the first period of time after the accident.

[0128] The water in the internal volume of the cryostat creates pressure in the cryostat emergency water supply pipeline 21 at the location where the first check valve 22 is installed (setpoint):

[0129]

[0130] where

[0131] - density of cryostat water, kg / m3 3 ;

[0132] - acceleration due to gravity, equal to 9.81 m / s 2 .

[0133] - the distance from the point where the emergency water supply pipeline leaves the cryostat to the surface of the cryostat water, equal to 9.7 m.

[0134] When the pressure in the water supply pipeline 5 becomes less than P уст , on the cryostat emergency water supply pipeline 21, the first check valve 22 will open, and on the water supply pipeline 5, the first shut-off valve 11 will close. At the same time, on the water outlet pipeline 8, the second shut-off valve 12 will close, and on the steam outlet pipeline 23 connected to the water outlet pipeline 8, the second check valve 24 will open. The cryostat water 18, under the action of gravity, will flow through the cryostat emergency water supply pipeline 21 into the supply pipeline 5, and then through the inlet pipe 6 into the inter-body volume of the blanket module 30, where it will mix with the water remaining after the accident in the blanket module 1, and will be heated under the action of the residual heat release in the spherical fuel elements 33 from the initial temperature t0 = 20 °C to the boiling temperature and evaporate. The temperature increase of the spherical fuel elements 33 in blanket module 1 will cease, since the energy of the residual heat release in the spherical fuel elements 33 will be spent on vaporization and removed by steam discharge.

[0135] As will be shown below, the mass of water entering the blanket module 1 through the cryostat emergency water supply pipeline 21 will always be greater than the mass of the generated steam, which is limited by the residual heat generation capacity in the spherical fuel elements 33, and the residual heat generation capacity in the spherical fuel elements 33 will continuously decrease. The blanket module 1 will be filled with water all the time, and when the cryostat water 18 enters the emergency water supply pipeline of the cryostat 21, the water will begin to fill the outlet pipeline 8 up to the closed second shut-off valve 12. The water level in the outlet pipeline 8 will rise and reach the steam outlet pipeline 23 of the blanket module emergency cooling system, fill it and through the second check valve 24 (which is open) begin to fill the steam discharge pipeline 25.The water level in steam discharge line 25 will rise until it reaches the surface of cryostat 20 (the law of communicating vessels). Water will then flow into blanket module 1 (to replace evaporated water) from both cryostat emergency water supply line 21 and steam discharge line 25, ensuring the presence of water in blanket module 1.

[0136] Steam bubbles formed during the boiling process of water in the blanket module 1 through the water outlet pipeline 8, the steam outlet of the emergency cooling system of the blanket module 23 and the steam discharge 25 enter the air cavity of the cryostat 19, where the steam condenses on the outer upper horizontal wall of the cryostat 16 and on the surface of the water of the cryostat 20.

[0137] Steam bubbles may enter the water of cryostat 18 through inlet pipe 6, supply pipe 5, and emergency water supply pipe 21 of cryostat. In this case, steam will condense in the water of cryostat 18. This mode is possible under two conditions: when water boils on the outer surface of the inner casing of blanket module 29 and the water flow velocity in the inter-casing volume of blanket module 30, inlet pipe 6, supply pipe 5, and emergency water supply pipe 21 of cryostat is low, and steam bubbles move against the water flow. In any case, all the steam generated in blanket module 1 will enter the water of cryostat 18, and the thermal energy released during steam condensation will be spent on heating the water of cryostat 18.

[0138] Cryostat water mass remains constant, but its temperature will increase due to heating by residual heat generation in the spherical heat-generating elements 33, provided that cooling of the cryostat water 18 via heat exchanger 26 is lost. Once the water in cryostat 18 boils, cooling of the blanket module by this method becomes impossible and ceases.

[0139] The feasibility of implementing the proposed method is confirmed by calculations, the results of which are given in Table 1.

[0140] After the accident at the rupture site of supply pipeline 27 and the cessation of the thermonuclear reaction, the residual heat power in the spherical fuel elements 33 Q(τ) of blanket module 1 rapidly decreases. Blanket module 1, designed for the production of fissile isotopes and containing U, is installed in the tokamak-based thermonuclear neutron source. 238 and Pu 239. The thermal power of blanket module 1 Q(τ) after the accident as a percentage of the power at the time of the accident τ = 0 - Q0= 5 MW depending on the time after the accident is given in Table 1, in column 1. The nominal thermal power of blanket module 1 Q(τ) in W after the accident depending on the time after the accident is given in Table 1, in column 2.

[0141] The accumulated energy E(τ) is of great importance—the total amount of thermal energy in J released from blanket module 1 during the residual heat release process by time t after the accident. It is defined as:

[0142]

[0143] The values ​​of E(τ) are given in Table 1, column 3. We further assume that all the accumulated energy E(τ) will go to heating and evaporation of water in cryostat 18, coming from the internal volume of the cryostat into blanket module 1.

[0144] Water consumption required to evaporate

[0145] to remove thermal power Q(τ), is defined as:

[0146]

[0147] where

[0148] - heat of vaporization of water 2.26⋅10 6 J / kg;

[0149] - heat capacity of cryostat water, J / (kg⋅K);

[0150] - thermal power of the blanket module at the moment τ, W.

[0151] Meanings are given in Table 1, column 4.

[0152] During the process of steam condensation in the water of cryostat 18 and subsequent cooling of the condensate to the temperature of the water of cryostat 18 by the moment thermal energy will be released, spent on its heating and evaporation:

[0153]

[0154] Assuming that all thermal energy E конд (τ) will go to heating the water of cryostat 18, at the moment the water temperature of cryostat 18 will be:

[0155]

[0156] where - transcript

[0157] - thermal energy released in the cryostat water during condensation of steam in it, J;

[0158] - mass of cryostat water, kg;

[0159] - heat capacity of cryostat water, J / (kg⋅K).

[0160] The values ​​of t(τ) are given in Table 1, column 5.

[0161] Dependence of quantities from time after the accident is given in Table 1.

[0162] Thus, the proposed system enables emergency cooling of the blanket module and prevents melting of the fuel elements within it for more than 60 days, i.e., the stated technical result is achieved. If cooling of the cryostat water via heat exchanger 26 is not lost, then cooling of the blanket module can continue indefinitely.

[0163] The main advantages of the proposed emergency cooling system are: the ability to cool the blanket module over a long period of time; the device for emergency cooling of the blanket module operates automatically and does not require operator intervention; water vapor generated during emergency cooling is not discharged into the atmosphere and does not pollute the environment.

[0164] The pipelines that supply water for further evaporation during emergency cooling of the blanket module have a significantly smaller diameter than the pipelines of the standard cooling system of the module, which is important given the limited volume inside the cryostat.

[0165] The amount of water required for emergency cooling of the blanket module is regulated automatically. As the module's thermal output decreases, the amount of steam generated and, accordingly, the amount of water entering and evaporating the module decreases. Water consumption for emergency cooling of the blanket module is reduced, and only the required amount is supplied at any given time.

[0166]

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