DE3119641C2 - - Google Patents

Description

The invention relates to a ceramic building material with new tron absorbent properties, as a shielding mat rial of nuclear power plants can be used.

Ceramic building materials for the absorption of neutrons with low energy, so-called thermal neutrons known. Such ceramic building materials contain known ones Neutron absorbers with high neutron capture cross sections, such as compounds of boron, cadmium, samari um, europium or gadolinium.

Such ceramic building materials have the disadvantage that they neutrons with a higher energy content (above 1000 eV), so-called epithermal neutrons, practically not absorbed beers. But since the operation of nuclear power plants, however also when operating other systems in which high-energy Particles or rays occur, both thermal and epithermal neutrons also occur, one was already in the past forced protective walls and shields to construct that absorb both types of neutrons. A protective shield is currently used for this purpose, which contains a substance that the fast epithermi neutrons to a lower energy level.  

With a second protective shield, the so obtained thermal neutrons from known neutrons sorber, such as boron. You also have be already trying to use neutron absorbers for thermal neutrons to add a substance called the epithermal neutrons brakes.

As substances that slow down epithermal neutrons to them Can be absorbed by neutron absorbers for thermal neutrons it is known to make connections of water substance, such as water, paraffin or water-containing materials, such as cement, concrete, etc. Such substances are ever but only temperature-resistant to a limited extent. This is how coals fall apart Hydrogen, like paraffin, a little above 200 ° C if you are not already distilled off. Distilled water at 100 ° C, and also all mineral water containing minera Lien and building materials give their water up to 250 at the latest up to 300 ° C completely.

In addition, these substances are all more or less quickly and intensely through ionizing rays like her occur in a nuclear power plant, are split and thereby develop hydrogen that ver with oxygen mixes and gives explosive detonating gas.

GB-PS 8 78 465 describes a neutron absorbing Material made from pieces of a hydrogen-containing material than, like polyethylene, with boron carbide embedded therein stands and in a base material, such as water or mineral oil, is distributed. This material is not a ceramic building material and also does not absorb epithermal neutrons.

The object underlying the invention was therefore there rin to get building materials, even at elevated temperatures ren, as above 250 ° C, especially above 300 ° C, so absorb thermal as well as epithermal neutrons and therefore used as a uniform shielding material that can.  

The ceramic building materials according to the invention with neutrons absorbent properties that a thermal neutron absorbent base material and contain hydrogen characterized in that they act as hydrogen carriers in the Base material distributed 5 to 50 wt .-%, based on the Ge total weight of the building material, at least one hydride of Zircon, yttrium and / or at least one element of Sel contained earth. If necessary, they contain additional Lich binders and / or usual fillers and auxiliaries.

If we are talking about ceramic building materials, we can on the one hand it is plastic ceramic masses, like water-containing ramming masses, and on the other hand about shape succeed from such plastic masses in dried form act. Such moldings can, for example, wall stones, pipes or any shaped parts that are are dimensionally stable and normal strength requirements enough and can also be burned.

The mentioned hydrides of zircon, yttrium and the rare Soils are superbly capable of epithermal new slowing down, even at high temperatures half 300 ° C because they are stable at these temperatures or start slowly to decompose.

For example, non-stoichiometric zirconium begins hydride slowly under normal conditions only above 300 ° C, to release its hydrogen to a limited extent and there to form with metallic zircon. Under hydrogen pressure it is even possible that the zirconium oxide is still at 500 ° C contains the hydrogen bound. The same is true to say the hydride of yttrium.  

Preferred hydrides according to the invention are non-stoichiometric hydrides of zirconium and yttrium of the formula ZrH _x and YH _x , where x is between 1.3 and 2. The Zirkonhy dride are the most preferred.

Although under normal conditions zirconium hydride and yttrium hydride at about 550 ° C with the formation of metallic Zirconium or yttrium was almost completely decomposed Surprisingly found that in the invention ceramic building materials these hydrides up to 500 ° C and higher so stable that they have enough hydrogen included to adequately slow down epithermal neutrons sen.

The ceramic construction according to the invention expediently contains substances 5 to 30, preferably 10 to 25% by weight of the ge called hydrides of zircon, yttrium and / or rare earth den, based in each case on the total weight of the building material.

A ceramic material containing neutron absorbers for thermal neutrons is used as the thermal neutron absorbing base material. According to the invention, these are preferably boron, cadmium, europium, gadolinium or samarium compounds alone or in conjunction with conventional ceramic materials, such as alkaline earth metal oxides, silicon dioxide, aluminum oxide or zirconium oxide. Examples of such neutron absorbers for thermal neutrons contained in the base material are boron oxide, boron carbide, cadmium oxide, europium oxide, gadolinium oxide or samarium oxide and so-called boron frit. A well usable base material consists of a ceramic mass made of boron oxide and alkaline earth oxides and / or SiO ₂ .

Particularly useful basic materials in which the ge called hydrides are incorporated, the following moderately won. 40 to 50% by weight magnesium oxide the one with 50 to 60% by weight boron oxide and water plastic mass mixed in a kneader.

30 to 60% by weight of this mass is then 15 up to 30% by weight zircon sand and 20 to 40% by weight Alumina cement and sufficient water mixed. After drying, the mass contains about 3 to 8 Ge % by weight boron. It can be used directly as ramming mass applies or worked up to a granulate and then further used according to the invention, d. H. with the above Hydrides are mixed.

Unless the base material sets as such and stable moldings or sufficiently stable linings gene or the like, it is appropriate in Kera Add micromasses conventional binders, such as wise water glass.

A method for producing kerami according to the invention shear building materials consists of the granulated raw materials to mix dry, then with a to mix mineral binders and then the Mixture in the desired form at elevated temperature, how to dry between 100 and 300 ° C, whereby mechani cal strength is achieved.  

Europium, gadolinium or samarium hydride can both as epithermal neutron absorbing material as also as thermal neutron absorbing material in Base material can be used. For example, euros piumhydride alone or in a mixture with other substances, such as Silica or alumina, by mixing with what serglas to the ceramic building materials according to the invention are processed.

The ceramic building materials according to the invention have the front partly that they are epithermal due to the hydride content Neutrons brake and in the thermal neutron absorber absorb the base material. this function practice them even at relatively high temperatures, such as up to 500 ° C, and are the first high-temperature plant substances for the complete absorption of neutrons via the entire energy range.

As mentioned, they can be used as plastic ramming compounds Obtain dried or fired ceramic moldings and be used.

The following examples are provided for further explanation the invention.

example 1

75 g boron carbide, 25 g zircon hydride and 50 g alumina melt cement was dry mixed together. Then was a plasticizer, based on the total amount of the above ingredients, from 7% tylose, 16% what  water, 2% paraffin oil and 2% oleic acid added. The whole was further mixed for 15 minutes by sieving a pressed granulate is produced, from which molded articles are then ge pressed and dried. These were at 350 ° C dries and partly baked at 500 ° C. You got stable ceramic stones with good mechanical resistance and excellent neutron absorption at temperatures up to at least 500 ° C.

Example 2

For the production of granules from magnesium oxide and Boric acid was 43% by weight magnesium oxide and 57 Ge % by weight boric acid in a kneader for 5 minutes mixed together. Then 18% water was added, the whole thing was further mixed for 15 minutes, dried, Fired and granulated at 1260 ° C.

25 g of zircon hydride and 125 g of alumina cement were added to 225 g of this fired granulate, and the whole was mixed dry. Then 90 cm ^{3 of} water were added and mixed with the other ingredients. The mass was shaken into shape and dried at room temperature.

Example 3

43% by weight were used to produce a ramming mass Magnesium oxide and 57% by weight boric acid with 20% by weight, based on these solids, water in a kneader mixed what was left to stand overnight through Sieved 2.5 mm sieve and allowed to dry.  

500 g of this mixture was dry mixed with 100 g of zircon sand and 300 g of molten alumina cement, then 270 cm ^{3 of} water was added and the mixture was mixed again for 15 minutes. In the dried state, the mass contained about 4.9% by weight of boron and had a spatial weight of 1.80.

225 g of this moist ramming mass were mixed with 25 g of zirconium hydride, ZrH _x , where x was between 1.5 and 2, and 125 g of alumina cement. The plastic mass obtained in this way was used directly as ramming mass.

Example 4

225 g of the tamped mass used in Example 3 were with 25 g of zirconium hydride, 125 g of HB acid putty and 125 g Mixed water glass, pressed into moldings and dried net.

Example 5

50 g boron carbide, 50 g yttrium hydride and 50 g alumina melt cement was dry mixed together and so then processed into moldings as in Example 1.

Example 6

225 g of the ramming mass mentioned in Example 3 were thoroughly mixed with 25 g of yttrium hydride YH _x , where x was between 1.3 and 2, and 125 g of molten alumina cement. The mixture was used as such as a ramming paste.

Claims (8)

1. Ceramic building material with neutron absorbing properties, which contains a thermal neutron absorbing base material and hydrogen, characterized in that it is distributed as a hydrogen carrier in the basic material 5 to 50 wt .-%, based on the total weight of the building material, at least contains a hydride of zirconium, yttrium and / or at least one element of rare earths. 2. Ceramic building material according to claim 1, characterized in that it contains zirconium hydride of the general formula ZrH _x or yttrium hydride of the general formula YH _x , wherein x is between 1.3 and 2. 3. Ceramic building material according to claim 1 or 2, characterized ge indicates that it contains the hydride in an amount of 5 to 30, preferably 10 to 25 wt .-%, based on the Ge total weight of the building material. 4. Ceramic building material according to claim 1 to 3, characterized ge indicates that it absorbs as thermal neutrons basic material contains a ceramic material, the at least one boron, cadmium, europium, gadolinium and / or samarium compound. 5. Ceramic building material according to claim 4, characterized records that it acts as a thermal neutron absorbing Base material is a ceramic mass made of boron oxide and earth contains alkali oxides and / or silicon dioxide. 6. Ceramic building material according to claim 1 to 3, characterized ge indicates that it absorbs as thermal neutrons base material is a ceramic material from 12 to 30 wt .-% magnesium oxide, 15 to 36 wt .-% boron oxide or Boric acid, 15 to 30 wt% zircon sand, 20 to 40 wt% Alumina cement, based on the base material, and enough water for a workable consistency holds. 7. Ceramic building material according to claim 1 to 6, characterized ge indicates that it contains water glass as a binder. 8. Use of a ceramic building material according to claim 1 to 7 as shielding of nuclear power plants.