DE1112303B - Silver alloys for nuclear reactor purposes - Google Patents

Description

The invention includes silver alloys for nuclear reactor purposes, in particular for control rods.

The materials to be used in nuclear reactor technology, for example for control rods, should largely satisfy the following conditions: The materials should have a high neutron capture cross-section possess, be sufficiently corrosion-resistant, be mechanically easy to process, no changes in their mechanical properties due to continued irradiation in the nuclear reactor suffer and, moreover, maintain the neutron absorbing property for as long as possible.

The materials previously known for these purposes only meet these conditions to a considerable extent to a limited extent. This is how the frequently used silver - cadmium - indium alloys show good corrosion properties and good radiation resistance, but the capture cross-section for Neutrons not particularly high. In addition, these known alloys lose their neutron absorbing properties quite fast.

About nuclear reactor materials with a higher neutron capture cross-section and to maintain the effectiveness of the absorber properties for a longer period of time than the silver-cadmium-indium alloys, the use of europium has also been suggested. Alloys of europium with titanium and zirconium are known. The maximum achievable europium content in these alloys was 0.5 percent by weight specified. This low europium content limits the use of such alloys for example Control rods very considerably.

Materials containing europium oxide, so-called cermets, are also available for use in nuclear reactors Purposes suggested. However, these have the disadvantage that they are not sufficiently resistant to radiation, since the Europium (III) oxide is reduced to europium (II) oxide under irradiation, whereby oxygen is released, which is, among other things, the cause of considerable damage. Europium (III) oxide also possesses in the form of Cermets have low mechanical stability and are particularly susceptible to corrosion due to their hygroscopic properties.

As a result of the difficult production and handling of the pure europium metal, which is in his Its properties are similar to that of calcium, but in its pure form it was not previously possible for use in nuclear reactors Purposes.

It has now surprisingly been found that silver alloys, consisting of 0.5 to 35%, preferably 2 to 20% europium, the remainder silver, particularly silver alloys
for nuclear regulatory purposes

Applicant:

W. C. Heraeus

Company with limited liability,
Hanau / M., Heraeusstr. 12/14

Dipl.-Chem. Dr. Richard Lesser, Hanau / M.,

and Dipl.-Ing. Edwin Erben, Hanau / M.,

have been named as inventors

these are suitable as a material for nuclear reactor purposes, in particular for control rods.

As a result of the large neutron capture cross-section of the europium, these ensure high europium contents of the silver alloys according to the invention have a high capture of neutrons. Also are the alloys are very corrosion-resistant and can be used up to a europium content of about 5 to 6% deform well, for example rolling; Fittings made of silver alloys with a higher Europium contents are expediently produced by casting. The use is particularly advantageous of the alloys mentioned due to the fact that they are also affected by continued irradiation in the nuclear reactor suffer no damage.

In addition, it has been shown that the properties of the silver alloys with a europium content can still be improved according to the invention, namely has from neutron absorbing Materials especially cadmium, which is present in amounts of 1 to 30%, preferably 5 to 15%, is added. The silver content of the alloys should not fall below 65% in these cases, as the europium-containing silver alloys according to the invention then the requirements to be made of them meet particularly well. In addition to the additional increase in the capture of neutrons, due to the neutron capture cross-section of the cadmium, mainly the mechanical properties of the alloys improved by this addition. So it could be established, among other things, that europium - containing silver - cadmium alloys

109 650/360

have significantly more favorable elongation values than silver-europium alloys with the same europium content, but without the addition of cadmium.

Both the silver-europium alloys and the europium-containing silver alloys are within the specified weight percent excellent corrosion resistance. They have a high absorbency for neutrons and are significantly longer in terms of neutron absorbing properties Time effective than the previously known nuclear reactor technical materials. This is particularly due to it attributed to the fact that europium-151, which is present with about 47% in the natural isotope mixture, can capture up to five neutrons without losing its absorber properties.

Due to the specified properties and advantages, the silver-europium alloys are suitable and also the europium-containing silver-cadmium alloys, especially for use as materials for nuclear reactor control rods.

Claims (3)

PATENT CLAIMS: 1. Silver alloys for nuclear reactor purposes, consisting of 0.5 to 35%, preferably 2 to 20% europium, the remainder silver. ίο 2. Silver alloys according to claim 1, characterized characterized in that they contain 1 to 30%, preferably 5 to 15% cadmium, wherein the silver content should not fall below 65% of the total alloys. 3. Use of the silver alloys according to claim 1 or 2 for the production of control rods for nuclear reactors.