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 invention relates to a method for producing a coating for absorbing the neutrons formed during the nuclear reaction of radioactive materials.
• the invention also relates to a shielding element produced by the method.
• absorber elements are usually produced in the form of various types of shafts, canisters, pipes or a similar configuration which surround an object which emits neutrons and thereby shield it.
• the use of such absorber elements enables, for example, the compact storage of neutron-emitting elements, in particular fuel elements from nuclear power plants.
• a fuel assembly storage rack is known from EP 0 385 1 87 A1, in which absorber sheets form a number of shafts which enclose the fuel assemblies over their entire length.
• These absorber elements are shafts or pipes made of a neutron absorbing material, for example boron steel, a stainless steel with a boron content of 1 to 2%.
• boron steel for example boron steel
• stainless steel with a boron content of 1 to 2%.
• these absorber elements are extremely cost-intensive and the efficiency is limited due to the limited proportion of boron.
• the Boron content can be increased up to 8%, but the costs also increase by a factor of about 10, so that such pipes cannot be used economically.
• a composite absorber element which has a thin carrier film or a thin carrier plate on which a polymer matrix is applied, in which boron carbide particles are embedded.
• Glass fiber-reinforced polymer is preferably used as the material of the carrier film or the carrier plate.
• the boron carbide particles are evenly distributed on the surface of the polar matrix, with a boron concentration of up to 0.1 g / cm 2 .
• this absorber element has a thickness of up to 7 mm, is in the form of a film or sheet and is suspended between an inner wall and an outer wall. It is not clear from US Pat. No. 4,221,862 whether a homogeneous distribution of the boron carbide particles arranged on the surface of the polymer matrix is ensured over a long period, in particular with regard to possible abrasion on the surface.
• EP 0 01 6 252 A1 describes a method for producing a neutron-absorbing absorber element.
• boron carbide is applied to a substrate together with a metallic substance by means of plasma spraying, the boron carbide being incorporated into a matrix made of a metallic substance.
• the procedure is also carried out so that oxidation of the boron is avoided.
• the absorber element produced in this way is said to be stable with respect to a liquid medium, such as is present in a fuel pool.
• the thickness of the layer of metal and boron carbide applied by means of plasma spraying is at least 500 ⁇ m.
• the proportion of boron carbide is approximately 50% by volume.
• Aluminum, copper and stainless steel can be considered as the metallic substance, the substrate containing the same metallic substance as the sprayed-on layer.
• a relatively thick layer on boron carbide is required, in particular the thickness of the layer is 3 to 6 mm.
• boron steel The production of boron steel is extremely complex.
• the steel is melted and boron is enriched up to 1 0 -valence by means of complex processes and mixed with the melted steel.
• the result is a boron steel with 1.1 to 1.4% by weight boron.
• This steel is very difficult to machine, is extremely brittle and is difficult to weld.
• Shielding elements made from it have an extremely high weight with average absorption properties.
• inner storage containers, so-called baskets, made of boron steel are known for the intermediate storage of fuel elements, which have a weight of approximately 10 tons.
• the present invention is based on the object of specifying a method for producing a coating or shielding elements for absorbing the neutrons formed in the nuclear reaction of radioactive materials, which method is economical and simple to use and increases the effectiveness of the absorption , allows greater variability with regard to the base materials and shape of the shielding elements, and in particular the manufacture allows lighter shielding elements with at least the same absorption qualities.
• a method for producing a coating for absorbing the neutrons formed during the nuclear reaction of radioactive materials is proposed, at least part of a shielding element consisting of a base material being provided with a boron nickel layer on its surfaces intended for this in a boron-containing dispersion bath is, during the coating process at least occasionally a relative movement between the surface to be coated and the dispersion bath is generated.
• boron nickel layer in a dispersion bath with temporary relative movement between the surface to be coated and the dispersion bath brings very good results.
• the boron can be incorporated in the nickel matrix in orders of magnitude of> 20 vol.%, Even ⁇ 40 vol.%.
• the boron can be present as boron carbide (B 4 C) or, according to a particularly advantageous proposal of the invention, as boron in elementary form in the dispersion. When using elemental boron, much larger boron deposits can be achieved.
• the absorption layers are in the order of 350 to 500 ⁇ m, which is extremely thin.
• Inorganic base material for example steel, titanium, copper, nickel and the like, is advantageously used. Despite its organic character and thus its susceptibility to neutron radiation, it can be used as a base material Carbon fiber material can be considered. Carbon fiber material has the particular advantage that the absorption element can be produced by electroplating.
• the shielding element in the finished state or in individual parts. Due to the independence from the base material, very easily editable materials can be used. On the other hand, very complicated shapes of shielding elements, containers, baskets and the like can also be completely prefabricated and then coated according to the invention.
• the base material can be prefabricated as a finished part or individual part, so that finished shielding elements can be formed from the individual parts.
• the coating in the dispersion bath is either chemical or electrolytic.
• the relative movement between the surface to be coated and the dispersion bath can take place, for example, by moving the element to be coated in the dispersion bath.
• elements such as boron are such that it is practically not economically feasible to circulate or pump around the dispersion. Any circulation or Pumping unit would be worn out in no time.
• the relative movement is intended to ensure continued thorough mixing or repeated mixing of the dispersion, and on the other hand to direct the dispersion to the surface to be coated.
• the entire coating system can also be moved for the purpose of generating the relative movement. For example, it is conceivable to carry out the coating in a kind of drum.
• the surface to be coated is arranged in the dispersion bath facing upward.
• the surface to be coated is arranged in the dispersion bath in such a way that the particles in the dispersion sink to the surface due to gravity.
• This arrangement according to the invention in particular in combination with the temporary generation of a relative movement between the surface and the dispersion bath, favors excellent coating results.
• the coating process be carried out in a glass tub. This ensures that the dispersion bath is particularly clean.
• the invention provides an easy to carry out, economical and very effective method for producing shielding elements for neutron absorption, which in particular makes shielding elements independent of the base material that are considerably lighter than known shielding elements with comparable absorption effects.
• the invention also relates to shielding elements produced by the described method. These are characterized in that they have a boron / nickel coating with a proportion of boron in elemental form or boron carbide greater than 20% by volume or by 40% by volume.
• the layer thickness is 350 to 500 ⁇ m, the layer being formed on an inorganic base material such as steel, titanium, copper or the like.
• the training takes place chemically or electrolytically.
• the shielding element can have been coated in the finished form or can be composed of individual coated individual parts.

Landscapes

• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Metallurgy (AREA)
• Physics & Mathematics (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Chemically Coating (AREA)

Priority Applications (4)

Applications Claiming Priority (1)

Publications (1)

Family

ID=8166669

Family Applications (1)

Country Status (4)

Cited By (5)

Citations (3)

• 1997
  • 1997-06-24 EP EP97930391A patent/EP0996953B1/de not_active Expired - Lifetime
  • 1997-06-24 DE DE59712320T patent/DE59712320D1/de not_active Expired - Lifetime
  • 1997-06-24 CZ CZ19994539A patent/CZ291292B6/cs not_active IP Right Cessation
  • 1997-06-24 WO PCT/EP1997/003309 patent/WO1998059344A1/de active IP Right Grant

Patent Citations (3)

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