Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
  • G21C3/42—Selection of substances for use as reactor fuel
  • G21C3/58—Solid reactor fuel Pellets made of fissile material
  • G21C3/62—Ceramic fuel
  • G21C3/626—Coated fuel particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/006—Coating of the granules without description of the process or the device by which the granules are obtained
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
  • G21C3/42—Selection of substances for use as reactor fuel
  • G21C3/58—Solid reactor fuel Pellets made of fissile material
  • G21C3/62—Ceramic fuel
  • G21C3/64—Ceramic dispersion fuel, e.g. cermet
• • 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
  • Y02E30/30—Nuclear fission reactors

Definitions

• ABSTRACT OF THE DISCLOSURE Particles are coated by tumbling in a drum with powder grains of a bindertreated coating material.
• the binder is softened by contacting the powder grains with a binder solvent as the grains enter the drum, so that the particles acquire an outer coating of the grains by a snowballing effect.
• the coating allows of the coated particles being formed into compacts by pressing and heating to set the binder, without the need for adding further filler or matrix material.
• This invention relates to a method of treating particles.
• the invention is particularly applicable to methods of forming nuclear fuel bodies which consist of a dispersion of particles containing nuclear fuel in a matrix.
• Several methods of making these fuel bodies have been proposed hitherto. For instance it has been proposed to mix the fuel particles (each enclosed in a fission product retaining coating) with a carbonaceous powder material and a binder and to press the mixture in a die whilst heating to polymerise the binder.
• Another method has been to fill in the spaces between a loose mass of particles by depositing carbon pyrolytically from the gas phase.
• a third method, and one with which the invention is directly concerned is that of applying an outer coating to the particles thick enough to allow a batch of particles so coated to be moulded under pressure in the green state.
• the advantage of the last mentioned method is that the difficulties which arise in trying to mix dense fuel particles with light powdered graphite are avoided, the total amount of carbon in the finished compact can be closely controlled and a considerable uniformity of distribution of particles can be easily achieved.
• a method of treating particles resides in tumbling the particles in a drum into which powder grains which have been previously treated with a binder are introduced, and softening the binder by contacting the grains with a solvent for the binder as the grains enter the drum such that the particles acquire an outer coating of the powder grain by a snowballing effect.
• a process for forming compacts containing nuclear fuel particles dispersed in a matrix material resides in applying to each of the particles an outer layer of matrix forming material by a method which resides in providing a supply of matrix forming material in powder form whose grains have been treated with a binder, tumbling the particles in a drum into which the powder grains of the matrix forming material are introduced as a free flowing powder, contacting the powder grains as they enter the drum with a mist of a volatile solvent for the binder, such that the particles acquire an outer coating of the powder grains by a snowballing effect, terminating the tumbling after the required amount of matrix forming material has been introduced and then forming a batch or mass of the particles so coated into compacts by pressing and heating to set the binder.
• the particles are heated in vacuum to evaporate any solvent remaining after they are removed from the drum and prior to heating in the press.
• the particles used in the process may have been precoated with a fission product retaining layer or layers before being tumbled with matrix forming material. Alternatively or additionally the whole compact may be enclosed in a fission product retaining coating layer or container.
• the matrix forming material is preferably a carbonaceous material such as graphite and the nuclear fuel particles may be carbides of nuclear fuel metals, pre-coated with a fission product retaining layer of pyrolytic carbon.
• a 2,000 kilogram batch of calcined petroleum coke (Shell H- reformer residue) was crushed, sieved to yield the particle size below 251 microns. The crushed coke was then micronised and the fraction below 50 microns was graphitised at 2600 C., the course fraction being reground.
• the graphitised grains represented a 1500 kg. yield and these were mixed with a phenol formaldehyde resin dissolved insolvent. After mixing for half an hour, the material was removed from the mixer, the solvent having dried off. The product was then reduced to crumbs and sieved to select the particle fraction below 76 microns. The final yield which constituted the matrix forming material was 1100 kilograms, having a tap density of 1.16 grams/cc. This material was used to form compacts in the manner now described.
• a batch of nuclear fuel particles pro-coated with pyrolytic carbon as a fission product retaining layer was placed in a rotary drum mounted for rotation on an axis which is inclined at a small angle to the horizontal and having one open end for the introduction of process materials.
• the drum was rotated on its axis at a speed of about 30 r.p.m.
• a supply of graphite grains of matrix forming material and a supply of binder solvent methylated spirit were mounted above the drum.
• Suitable feed pipes were arranged to communicate the supply of grains and solvent with the interior of the drum, the pipes terminating within the drum at adjacent positions so that the grains and a mist of the solvent contacted one another after these material had left their feed pipes and before they impinged on the drum surface.
• a rate of solvent injection of 10 cc. per hour was found adequate where the graphite grain-s were introduced at 600 grams per hour through an orifice 2 millimetres in diameter.
• the tumbling and graphite introduction was maintained for about four hours and then stopped, by which time some 2,500 grams of graphite grains had been gathered up by the 500 grams of particles.
• the particles were then removed from the drum and placed in a furnace where they were heated in vacuum up to 50 C. for half an hour to evaporate any solvent remaining.
• the particles which had been easily handable without fear of crushing or disintegration since they were removed from the drum, were then divided into batches suitable for forming compacts.
• the matrix forming material is a free flowing powder whose grains have been treated with and carry a binder, and said solvent is a volatile solvent for the binder.
• a method as claimed in claim 2 including the step of forming a selected mass of the fuel particles so coated into compacts by pressing and heating to set the binder.
• a method of forming compacts containing nuclear fuel particles dispersed in a matrix material comprising applying to each of the particles an outer layer of matrix forming material by a method which comprises providing a supply of matrix forming material in powder form whose grains have been treated with and carry a binder, tumbling the fuel particles in a drum into which the powder grains of the matrix forming material is introduced as a free flowing powder, contacting the powder grains as they enter the drum with a mist of a volatile solvent for the binder, such that the particles acquire an outer coating of the powder grains by a snowballing effect, terminating the tumbling after the required amount of matrix forming material has been introduced and then forming a selected mass of the patricles so coated into compacts by pressing and heating to set the binder.
• a method of coating nuclear fuel particles which resides in mixing the grains of a matrix forming material with a binder dissolved in a solvent, drying off the solvent, reducing the resultant cake to crumbs, sieving the crumbs to select a powder fraction below a given size, introducing the fuel particles to be coated into a revolving drum, introducing the powder into the revolving drum, tumbling the fuel particles to be coated in the drum and contacting the binder-treated powder grains of coating material with a binder solvent mist immediately before they enter the drum so that they become susceptible to adhering to and coating the fuel particles tumbled in the drum, thus forming coated fuel particles which can be formed into compacts by pressing and heating without the need for further filler or matrix material.
• a method of forming compacts containing particles of a first ceramic material dispersed in a second ceramic matrix material comprising applying to each of the particles of the first ceramic material an outer layer of the second ceramic matrix forming material by a method which comprises providing a supply of the second matrix forming material in powder form whose grains have been treated with and carry a binder, tumbling the particles of the first ceramic material in a drum into which the powder grains of the matrix forming material are introduced as a free flowing powder, contacting the powder grains as they enter the drum with a mist of a volatile solvent for the binder, such that the particles of the first ceramic material acquire an outer coating of the powder grains by a snowballing effect, terminating the tumbling after the required amount of matrix forming material has been introduced and then forming a selected mass of the particles so coated into compacts by pressing and heating to set the binder.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Ceramic Engineering (AREA)
• High Energy & Nuclear Physics (AREA)
• Plasma & Fusion (AREA)
• General Engineering & Computer Science (AREA)
• Dispersion Chemistry (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Carbon And Carbon Compounds (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)
• Glanulating (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=10433390

Family Applications (1)

Country Status (8)

Cited By (8)

Families Citing this family (1)

• 0
  • US US3344211D patent/US3344211A/en not_active Expired - Lifetime
• 1964
  • 1964-10-30 GB GB44460/64A patent/GB1081447A/en not_active Expired
• 1965
  • 1965-10-15 AT AT937165A patent/AT263959B/de active
  • 1965-10-20 DE DE1571445A patent/DE1571445C3/de not_active Expired
  • 1965-10-22 SE SE13715/65A patent/SE316247B/xx unknown
  • 1965-10-26 BE BE671420D patent/BE671420A/xx unknown
  • 1965-10-27 CH CH1500065A patent/CH430896A/de unknown
  • 1965-10-29 NL NL6514057A patent/NL6514057A/xx unknown

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