Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21D—NUCLEAR POWER PLANT
  • G21D7/00—Arrangements for direct production of electric energy from fusion or fission reactions
  • G21D7/04—Arrangements for direct production of electric energy from fusion or fission reactions using thermoelectric elements or thermoionic converters
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin

Definitions

• the invention relates to a thermoelectric generator with a nuclear heat source according to the preamble of claim 1.
• a generator with the name “Romashka” in which the nuclear heat source is formed by a reactor in the form of a cylinder.
• the core of the reactor contains ceramic material.
• the generator has a cylindrical support for thermoelectric units, which surrounds the reactor at a defined distance. The heat transfer from the reactor to the carrier as well as the dissipation of the heat loss from the carrier takes place by radially outward heat radiation.
• the object of the invention is to improve this known device so that an exact control of the reactor is possible and the weight of the carrier is lighter.
• the solution to this problem is disclosed in claim 1.
• the high-temperature reactor which is made entirely of ceramic materials, has one on its surface. very high temperature and, as a result, can give sufficient power in the form of heat radiation to the outside.
• the cylindrical screen with the thermoelectric units absorbs the heat radiated from the high-temperature reactor, partially converts it into electrical current and radiates the heat loss to the outside.
• the outside temperature of the screen is approximately in the order of 700-900 ° K.
• the temperature difference from the inside to the outside of the screen must be about 400-600 ° K.
• a sufficiently high heat transfer from the surface of the high-temperature reactor to the inside of the screen requires temperatures in the order of 1400-1600 ° K.
• the highest material temperature in the screen is 1400 ° K.
• a temperature of 1730 ° K results for the surface of the reactor.
• temperatures of approx. 2400 ° K can be assumed. Such high temperatures make it necessary that all components of the reactor are made of ceramic materials.
• thermoelectric units Radiation damage to the thermoelectric units and the thermal insulation from fast neutrons occurs only to a very small extent, since it is in the nuclear heat source around a thermal core
• the fast neutron dose in the screen is so low that carbon fiber reinforced graphite can be used as screen material without hesitation.
• thermoelectric generator A higher power of the thermoelectric generator than the desired one can also achieve an increase in the screen surface. Taking into account all parameters of the temperature level and the development possibilities of the thermoelectric generators, it seems that an increase in output from 200 kW el to approx. 1000 kW el is possible without the size of the unit having to be increased significantly.
• FIG. 1 is a perspective view of the thermoelectric generator according to the invention
• FIG. 2 is a longitudinal section through this generator
• FIG. 5 shows a section along the line C-D of FIG. 3
• FIG. 6 shows a section of the screen with the thermoelectric units, greatly enlarged
• FIG. 7 shows the attachment of a thermoelectric unit to the screen.
• Figures 1 and 2 show a thermoelectric generator, which essentially has a cylindrical thermal high-temperature reactor 1, a carbon-fiber-reinforced graphite, also cylindrical screen 2 as a carrier for a large number of thermoelectric units 3 and two plates 4 and 5 made of thermally insulating material .
• the high-temperature reactor which has an output of 3 MWth, is arranged in the center of the screen 2, which surrounds it at a distance.
• the screen 2 is designed as a lattice-like scaffold construction, as will be explained later.
• the two plates 4 and 5 which are provided on the end faces of the high-temperature reactor 1, consist of magnesium oxide and carbon fiber-reinforced graphite, which serves as a carrier material. They also cover the annular space 6 between the high-temperature reactor 1 and screen 2.
• Each control and shutdown device 7 comprises a number of absorber rods 8 and the associated drives 9.
• the absorber rods 8 can be moved into and out of the core from the end faces of the high-temperature reactor 1. They consist of carbon fiber reinforced graphite, to which boron is added as a neutron absorber. In the example given here, about 20 absorber rods are required to switch the high-temperature reactor 1 on and off; only one of the absorber rods is shown in FIG. 2.
• the forehead surfaces and the surfaces which are contacted by the absorber rods 8 are provided with a surface treatment consisting of titanium carbide.
• the drives 9 of the absorber rods 8 are located above and below the high-temperature reactor 1, outside the plates 4 and 5, so that they are protected against the high temperatures of the high-temperature reactor 1.
• An electric motor is used as the driving force for the retraction and extension of the absorber rods 8, which enables the absorber rods 8 to be moved back and forth by approximately 4 m via a toothed rack and a pinion.
• the devices 7 are located on the end faces of the high-temperature reactor 1, since this arrangement allows the entire outer surface of the screen 2 to be used for heat transfer.
• the high-temperature reactor 1 has different fuel concentrations over its cross section as well as in the axial direction, namely that the fuel concentration lies on the lateral as well as on the upper and lower surface of the core by approximately 50 to 100? higher than the average fuel concentration. As a result, the otherwise existing reduction in performance is compensated for.
• the neutron flux is influenced relatively little by this choice of concentration; the performance division, on the other hand, can be set to an accuracy of approx. + - 30% deviation from the mean.
• the core of the high-temperature reactor 1 consists of a number of rod-shaped fuel elements 10, one of which is shown in FIGS. 3, 4 and 5.
• Carbon fiber reinforced graphite is used as the material for the fuel elements 10, in which fuel particles made of uranium oxide coated with zirconium carbide are embedded.
• Zirconium carbide has a sufficiently high melting point of approx. 3500 ° C. Given the low neutron dose required here and an assumed operating time of about 10 years, sufficient stability of the coated fuel particles is to be expected.
• the fuel elements 10 have a cylindrical cross section over most of their length; an end piece 12 with a hexagonal cross section is attached to this part 11 at the top and bottom.
• the end pieces 12 are larger than the cylindrical section 11, so that there are free gaps between the fuel elements 10 which are close together for the propagation of the heat radiation.
• the fuel elements 10 have a reflective coating 13 made of silicon carbide on part of their jacket, as can be seen in FIG. 5.
• the mirroring 13 causes a larger part of the heat radiation to escape through the free spaces.
• Each fuel assembly 10 has a central axial bore 14 and two further axial openings 15 for the insertion of two absorber rods 8.
• a support rod 16 is arranged in the bore 14, which consists of a material with a very low thermal expansion, preferably carbon fiber reinforced graphite.
• a clamping screw 17 which is also made of carbon fiber-reinforced graphite and is used to fix the fuel element on the support rod 16.
• a plurality of fuel assemblies 10 are arranged one below the other on a support rod 16, as can be seen from FIG. 3.
• An expansion gap 18 is left open between two fuel assemblies 10. Further expansion gaps are also present between fuel elements 10 arranged next to one another.
• the support rods 16 can be manufactured in such a way that their expansion is practically negligible when the temperature rises.
• the core of the high-temperature reactor 1 is constructed in such a way that the active core zone 19 has an annular cross-section, ie the central zone of the core remains free of fuel elements 10 and therefore free of power in order to cause an excessive temperature rise within the high-temperature reactor 1 to avoid.
• the maximum temperature inside the core is 2300 ° K.
• reflector elements 21 are arranged, which have the same shape as the fuel elements 10.
• burnable neutron lifts are provided in the reflector elements 21 and also in the fuel elements 10.
• the screen 2 which serves as a support for the thermoelectric units 3, is designed as a lattice-like framework construction. This is explained in more detail in FIGS.
• 6 shows one of the square grid meshes 22 of the scaffold structure, which is framed by webs 23.
• the webs 23 consist of carbon fiber reinforced graphite.
• One of the thermoelectric units 3 is inserted into each mesh 22.
• semiconductors 28 made of silicon germanium crystals with high p and n doping are used, which are attached to a metal plate 24.
• the metal plates 24 each represent the heat exchanger on the hot side of the thermoelectric unit in question.
• the metal plates 24 must be electrically insulated from the frame structure of the screen 2.
• the type of fastening shown in FIG. 7 is provided for fixing the metal plates 24 in the mesh mesh 22.
• Screws 25, which are arranged in such a way that ceramic shaped bodies 26 are located between the metal plates 24 and the lattice webs 23, serve as fastening means.
• the moldings are preferably made of magnesium or aluminum oxide.
• thermoelectric units 3 use high-temperature materials such as tungsten or niobium.
• the high-temperature reactor 1 described can be operated according to two concepts: in continuous operation or for a temporary use with a short running-in phase. For continuous operation, which requires careful design with combustible neutron poisons, the amount of fissile increases and is in the order of 100kg fissile for a reactor with an output of 3 MW th .
• the absorber rods 8 only serve to switch the reactor on by extending it and to switch it off again by retracting after the end of the operation. Because of the high temperature coefficient of the reactor and the relative insensitivity of the overall system to temperature fluctuations, in this mode of operation the burnable neutron poisons can achieve approximately the same output for a longer period of time, so that regulation with the absorber rods 8 is not necessary.
• the absorber rods 8 When the high-temperature reactor 1 is used temporarily, on the other hand, it is necessary to extend the absorber rods 8 in a time range of 10-100 seconds each.
• the temperature increase that occurs in this case is well tolerated by the core of the high-temperature reactor 1, since the strains are essentially absorbed by the support rods 16 made of carbon fiber-reinforced graphite and this material has practically no strain.
• the load with fuel is smaller for temporary use and is in the order of 80kg. In this case, the activation of the overall system is practically negligible. It is also advantageous that only a little burnable neutron poison is required.
• the volume of the core is approximately 25m 3 with a radius of the reactor of 1m and a height of 8m.
• the radius of the screen 2 is based on 1.8 m and its height 10 m.
• the thermal neutron flow in the core of reactor 1 is 10 13 n / cm 2 s, that in the screen 4x10 11 n / cm s.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Plasma & Fusion (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Monitoring And Testing Of Nuclear Reactors (AREA)

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Publications (1)

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• 1985
  • 1985-12-04 DE DE3542839A patent/DE3542839A1/de active Granted
• 1986
  • 1986-12-04 EP EP87900046A patent/EP0250496A1/de not_active Withdrawn
  • 1986-12-04 US US07/113,282 patent/US4830817A/en not_active Expired - Fee Related
  • 1986-12-04 WO PCT/DE1986/000496 patent/WO1987003733A1/de not_active Ceased

Non-Patent Citations (1)

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