Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F1/00—Shielding characterised by the composition of the materials
  • G21F1/02—Selection of uniform shielding materials
  • G21F1/08—Metals; Alloys; Cermets, i.e. sintered mixtures of ceramics and metals

Definitions

• the present invention relates to a nuclear radiation absorber.
• the best known are cadmium, samarium, europium, boron and gadolinium.
• Cadmium has the disadvantage of being a very toxic product and of having a very low melting temperature (321 ° C) and a boiling temperature (765 ° C).
• the sanarium and europium have practically not given rise to industrial development because of their too high price.
• boron which is used in different forms: elemental boron, borides, boron carbide, boric acid, etc.
• this material has very poor mechanical properties and must be strongly diluted in a metallic matrix such as aluminum.
• nium for example, in order to acquire the qualities necessary to be able to take the form required by each type of absorber. But thus, its absorbency is greatly reduced and must be compensated by an increase in the volume of material used which, ultimately, significantly increases the price of the absorber.
• the material obtained is a composite product, the production of which requires the use of very elaborate manufacturing processes if it is desired to obtain a regular dispersion of the boron in the aluminum matrix and avoid heterogeneity of absorption capacity.
• Gadolinium and its oxide have already been used for many years in various nuclear installations where, mixed with the fuel, they act as moderators. However, their application to the manufacture of radiation absorbers poses problems.
• the oxide generally available in powder form, it must be mixed with other products using very complex technologies and its very poor mechanical properties make its application when producing absorbers of complex shape. , both delicate and expensive. In addition, this oxide has poor thermal conductivity and its absorption capacity is relatively reduced compared to that of elementary gadolinium.
• gadolinium has the highest capture cross section of all known absorbers in the slow neutron spectrum.
• its section for thermal neutrons with energy 10 ⁇ 2 eV is 100 times larger.
• fast neutrons its efficiency is as good as that of boron.
• This absorber is characterized in that it consists of an alloy of gadolinium with an aluminum chosen from the group comprising pure aluminum, alloyed aluminum, pure or alloyed aluminum containing a dispersed phase.
• the aluminum used can be pure either because it has been refined by any means such as three-layer electrolysis or fractional crystallization or simply as it is collected at the outlet of the electrolysis tanks with its usual impurities such as iron and silicon.
• this aluminum can also be a conventional alloy such as those designated by the numbers 1000, 5000 and 6000 in the standards of the Aluminum Association, which makes it possible to reinforce the mechanical properties of the absorbers obtained, or else an aluminum alloy with at least one other metal also having absorbent qualities such as cadmium, samarium, europium, lithium, hafnium, tantalum, the latter alloys can also be obtained from alloys of types 1000, 5000 and 6000.
• aluminum, alloyed or not may contain a dispersed phase such as carbon fibers or the like intended to reinforce the mechanical strength of the absorbers, or alternatively, combined or not with these fibers, a radiation absorbing product such as, for example for example, boron and its derivatives which can represent up to 30% of the mass of aluminum used.
• a dispersed phase such as carbon fibers or the like intended to reinforce the mechanical strength of the absorbers, or alternatively, combined or not with these fibers, a radiation absorbing product such as, for example for example, boron and its derivatives which can represent up to 30% of the mass of aluminum used.
• the gadolinium-aluminum alloys thus produced allow, due to their good mechanical properties, to be easily transformed into absorbers of any shape by at least one of the manufacturing processes chosen from molding, whether in sand, in shell, under low or high pressure, hot or cold rolling, extrusion and forging.
• the aluminum matrix gives finished products excellent thermal conductivity (from 120 to 180 W / m ° K2 depending on the aluminum matrix chosen), thus allowing the heat created by absorption to be quickly dissipated towards external cooling systems.
• the starting point of melting of the Al-Gd alloys tested is very high, in most cases greater than 620 ° C; this characteristic allows the neutron barriers thus manufactured to easily withstand the heating caused by the absorption of neutrons or other radiation.
• the atomic mass of Gd being very high (156.9 g), the ⁇ and X rays in particular are strongly absorbed.
• Corrosion resistance in general, is not or little affected by the presence of gadolinium, and the corrosion properties are close to those of the aluminum matrices used. Alloys of the 1000, 5000 and 6000 series exhibit excellent corrosion resistance against atmospheric agents or in a marine atmosphere. This behavior can be further improved by appropriate surface treatments (anodization, alodine, paint, plastic coatings ).
• the mechanical characteristics are high and depend on the aluminum matrix chosen.
• the mechanical properties vary with the gadolinium content; Table II gives results obtained on cast alloys, one with a Gd content of 12% by weight, the other with a weight percentage of 25%.
• Table III presents the results obtained on alloys rolled to 11% Gd by weight.
• the level of resistance and elastic limit can be greatly increased to reach the following values:
• compositions of ternary, quaternary, quinary alloys, etc., comprising gadolinium could give values much higher than these.
• the applications of this invention are multiple and touch all the fields where a problem of absorption of radiation arises (neutrons, ⁇ rays, X rays, that these fields are military or civil.
• Examples of applications include: baskets for transporting and storing nuclear waste, pool racks for storing fuel elements from nuclear reactors, shielding decontamination installations, shielding military vehicles , atomic shelters, nuclear reactor components, the shielding of control devices using radiation or radioactive sources, etc. This list cannot in any way be limiting.

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• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Metallurgy (AREA)
• Physics & Mathematics (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Absorbent Articles And Supports Therefor (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Materials For Medical Uses (AREA)
• Buildings Adapted To Withstand Abnormal External Influences (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)

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• 1985
  • 1985-07-11 FR FR8510983A patent/FR2584852B1/fr not_active Expired
• 1986
  • 1986-07-09 AT AT86420187T patent/ATE40763T1/de not_active IP Right Cessation
  • 1986-07-09 DE DE8686420187T patent/DE3662078D1/de not_active Expired
  • 1986-07-09 NZ NZ216802A patent/NZ216802A/xx unknown
  • 1986-07-09 GR GR861792A patent/GR861792B/el unknown
  • 1986-07-09 EP EP86420187A patent/EP0211779B1/de not_active Expired
  • 1986-07-10 DK DK327786A patent/DK327786A/da not_active Application Discontinuation
  • 1986-07-10 CA CA000513519A patent/CA1268031A/fr not_active Expired - Fee Related
  • 1986-07-10 PT PT82958A patent/PT82958B/pt not_active IP Right Cessation
  • 1986-07-10 ES ES8600232A patent/ES2001015A6/es not_active Expired
  • 1986-07-10 FI FI862902A patent/FI85923C/fi not_active IP Right Cessation
  • 1986-07-10 JP JP61162924A patent/JPS6270799A/ja active Pending
  • 1986-07-10 ZA ZA865168A patent/ZA865168B/xx unknown
  • 1986-07-10 NO NO862793A patent/NO169035C/no unknown
  • 1986-07-10 KR KR1019860005558A patent/KR910007461B1/ko not_active IP Right Cessation
  • 1986-07-10 AU AU60048/86A patent/AU580177B2/en not_active Ceased
  • 1986-07-10 IE IE185186A patent/IE58952B1/en not_active IP Right Cessation
  • 1986-07-10 BR BR8603239A patent/BR8603239A/pt unknown
  • 1986-07-10 IL IL79385A patent/IL79385A0/xx not_active IP Right Cessation

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