DE1812347A1 - Uranium-silicon alloy nuclear fuel element - Google Patents

Description

IG / scn

November 19, 1968

ATOI-IIC ENSIiGY OF CAITADA LIIJITED,

150 Kent Street, City of Ottawa, Province of Ontario, Canada

Uranium-silicon alloy nuclear fuel element.

The invention relates to a nuclear fuel element having a of uranium metal alloyed with about two to 7 »3 percent by weight silicon and having a void for the purpose of increasing it the corrosion resistance of its alloy heat-treated Core, which is encompassed by a jacket made of a known corrosion-resistant zirconium alloy according to patent application P 15 89 458. 3.

For uranium-alloyed nuclear fuel elements for nuclear power reactors Difficulties arise because the highly alloyed with uranium, exposed to the highly heated water as a coolant Alloys have only a low corrosion resistance. In view of this low corrosion resistance In the aqueous medium, any flaw in the protective jacket surrounding the uranium alloy leads to sworn and undesirable Disruptions.

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In order to reduce these disadvantages, alloys with a composition approaching the delta phase U Si are already available from Uran-Siliciumie-gärä-Hasig known the one lower Corrosion rate. However, these alloys show insufficient volume stability during irradiation, since the disorder in the regular delta phase and / or the breakout of gaseous fission products can lead to volume increases that endanger the operation.

According to the main application P 15 89 ^ 58 · 3 is already proposed It has been found that the nuclear fuel element alloyed one of uranium metal with about 2 to 7/3 weight percent silicon and a void that is heat-treated to increase the corrosion resistance of an alloy Has core which is surrounded by a jacket made of a known corrosion-resistant zirconium alloy and the empty space is about 3-15 percent by volume of the uranium alloy.

The invention aims a Vesfoesserung and further development of the main application, It is in a surprising way proposed to use nuclear fuel elements at each of which the void space of the core up to 25 percent by volume of the uranium alloy, with 25 percent by volume themselves are expressly included. By such a Formation of the central core simplifies the manufacture, the scope of the nuclear fuel elements enlarged.

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A further embodiment of the invention is surprising Provide that the void is preferably 15 percent by volume of the uranium alloy · is. This is an improvement as well as further training compared to the main application achieved because there the tolumen area only up to 15 percent by volume without this value include yourself. This forms the value specified in the main application as a borderline case that has not yet been achieved according to the invention the preferred embodiment for the production of the nuclear fuel element, just as a difference to the main registration.

Another embodiment of the invention provides that the fuel elements provided with a central void can be supplemented by a cover or shut-off component such as a plug »pin or the like made of U« Si, with this component is fused, welded or soldered to the core in order to seal the central empty space in the core. This is advantageous in that if the shell or the end face in the complete nuclear fuel element is damaged, the entry of the water into the relative hot fuel core prevents "

Another embodiment of the invention provides that instead of a central empty space in the core of the fuel element, a plurality of individual spaces, in particular evenly distributed and / or pore-like spaces, is or are present, with these amount to 3-15 percent by volume of the uranium alloy

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like rooms serve the same purpose as the central one Empty space in which they absorb or compensate for the expansion of the element. This, in turn, is advantageous in that than in the case of a defective jacket the water does not go into the relatively hot fuel core can penetrate and a steep Corrosion is avoided »

In addition to a single void or evenly distributed pore-like individual spaces, the invention proposes to provide an analogous combination of these two proposals, that is, a uranium-silicon alloy core with evenly distributed porous voids and a more extensive void. In this embodiment of the invention, where a combination of the distributed pore-like spaces and the single extensive void is used, the total volume is about 3 - 25 fo * based on the volume of the uranium-silicon alloy core.

Furthermore, according to the invention, exemplary methods for Manufacture or combine the individual parts of the nuclear fuel element suggested;

Example 1 - Individual manufacture of the elements that the

Work step procurement of the sliding seat follows »

At | s of the uranium-silicon alloy becomes a rod-shaped component poured, which contains the central empty space and then the rod or the like is at a temperature in the range of 750 - 900 C,

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preferably heat treated at about 800 C to give the alloy to transfer peritectoidally into the delta phase (u_Si). the the exact temperature of the heat treatment depends on the trace elements present in the alloy. This procedure can depending on the first cast shape of the alloy and the degree of completeness of the application required transformation, in a time interval of 2 to 300 hours, regularly finished after about 72 hours will. Then the rod is machined, such as by grinding, to the final ^ for the core of the fuel element Brought intended dimensions and the fuel assembly produced in that the core with a sliding fit in the protective jacket is introduced.

Example 2 - A process similar to Example 1 differs from this in that the uranium-silicon alloy is poured into an ingot or the like, instead of a rod with a central empty space. After the heat treatment at about 800 C, as has been carried out in Example 1, the ingot is at a temperature which is less than the pearl tectoid temperature is 930 C, to one with a central empty space provided rod or the like. Extruded. The temperature falls below 930 C, by one opposite to prevent a specific workflow that would destroy the delta color in the alloy. As well as earlier the rod is then brought to its final dimensions by machining or grinding and that is what you get Nuclear fuel element by placing the machined rod or the

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• m 6 -

Core is inserted with a sliding fit in the protective jacket.

Example 3 - A procedure similar to Example 2 is used, except that the order of the working hole center Heat treatment and extrusion is reversed. So the uranium-silicon alloy is cast as an ingot and then extruded into a rod having a central void. The rod is then heat-treated at about 800 G, as in Example 1, in order to convert the alloy peritectoidally into the delta phase U_Si. Then the rod is up its final dimensions intended for the core, brought by machining or grinding and then "the core is inserted into the protective jacket with a sliding fit, so that the nuclear fuel element is formed.

Example k - This method contains the first working steps given in Example 2, ie the uranium-silicon alloy is cast as an ingot and then the ingot is heat-treated at about 800.degree. C. as in Example 1. The heat-treated ingot is then coextruded within the zirconium alloy shell or jacket at a temperature below 930 G »so that a nuclear fuel element with a core of uranium-silicon in delta phase U_S ± is obtained, which has a central empty space and then with the Sheath made of zirconium alloy is clad, or "is melted onto this or the like"

Example 5 - A method similar to that of Example k _t

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with the exception that the work steps heat treatment and! coextrusion are reversed in the order} d. The uranium-silicon alloy is cast as an ingot and then coextruded within a zirconium alloy shell to form a nuclear fuel element in which the core has a central void, and then it is clad with the zirconium alloy shell The nuclear fuel element thus combined is then subjected to a heat treatment at about 800 C ₁ as indicated in Example 1 in order to convert the uranium-silicon alloy core into the delta phase TJ “Si.

Example 6 - The uranium-silicon layer becomes a rod Cast with evenly distributed pore-like individual spaces, which make up a total of 3-25 percent by volume of the rod * This rod or the like can be made by adding a suitable inert gas such as helium to the molten charge is introduced. This can be done by blowing or the like. The gas into the melting alloy. If the When the alloy solidifies, the gas is enclosed in it in the form of spherical closed pores (pore-shaped individual spaces). According to the invention it is proposed that the fusible alloy, in particular at I5OO Cj of the atmosphere of the inert gas, which regularly absorbs enough gas to achieve the desired porosity during the To achieve solidification.

Another embodiment of the invention provides that the

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Gas is introduced into the molten alloy by introducing a gas generating liquid or solid into the hollow mold in which the core is formed. Metallic magnesium is preferably used for this. When bringing the gas generating ^one liquid or solid with the molten alloy in contact, the gas is formed and released and penetrates the alloy and is again in the alloy during solidification in generally spherical closed pore spaces enclosed DAJ ^ n the rod is heat-treated according to example 1 at about 800 C in order to convert the alloy peritectoidally into the delta *

phase U ₀ Si to transfer «Then the rod is through mechani- J

see machining or grinding to its final dimensions Brought as the core of a fuel element and the element is in turn created by the fact that the core in the protective jacket is introduced with a sliding fit.

For the nuclear fuel elements according to this invention found that one has an output of more than 10,000 megawatt-days per ton of uranium without the inside diameter exceeding $ 1.

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Claims (1)

IG / s eh. November 19 »1968 ATOMIC ENERGY OF CANADA LIMITED Claims 1. Nuclear fuel element with a uranium metal with about two to 7> 3 percent by weight of silicon alloyed and having a void, in order to increase the corrosion resistance its alloy heat-treated core, which is covered by a shell made of a known corrosion-resistant zirconium alloy is included according to patent application P 15 89 4 ^ 8. 3 » characterized in that the void is up to 25 percent by volume of the uranium alloy. 2. Nuclear fuel element according to claim 1, characterized in that that the void is in particular 15 percent by volume of the uranium alloy. 3. Nuclear fuel element according to claim 1 or 2, characterized in that that there is one made of uranium-silicon alloy Cover or shut-off component such as a plug, pin or the like. Has fused to the core ends or the like, and closes the empty space. k. Nuclear fuel element according to claim 1, characterized 109824/0514 draws that the empty space consists of a meiuc number of individual spaces, in particular consists of evenly distributed and / or pore-like spaces. 5 Process for the manufacture of a nuclear fuel element with a hollow uranium-silicon alloy core in the Delta phase U "Si, according to one of claims 1-4, characterized in that that a rod-shaped component with a central empty space was cast from the uranium-silicon alloy then this component is at around 750-900 C in heat-treated for a time interval of two to three hundred hours is to transform the alloy peritectoidally into the delta phase to, then this component to predetermined Dimensions machined and the rod-shaped component inserted with a sliding fit into the protective jacket will. 6 »Process for the manufacture of a nuclear fuel element according to any one of claims 1-4, wherein the element is a hollow, uranium-silicon alloy in the delta phase U "Si existing core, characterized in that the uranium-silicon alloy is initially a bar-shaped component is cast, this component is then between about 750 - 900 ° C is subjected to a heat treatment in the time interval of 2 - 300 hours, and the alloy peritectoidally into the To transfer Deltaphaae, then this component at a temperature below 930 C in a, a central empty space having rod is extruded, then the rod me- 109824/0514 mechanically processed and inserted into a protective jacket with a sliding fit, 7.Verfahren for the production of a nuclear fuel element according to any one of claims 1-4, wherein the nuclear fuel element with a hollow core made of Tlran-silicon alloy ¹ in the delta phase U_Si is made, "first cast an ingot-shaped component from the uranium-silicon alloy and then this component about 750 - 900 ° C in the interval of 2 - 300 hours is subjected to a heat treatment in order to convert the alloy peritectoidally into the delta phase, characterized in that the ingot-shaped or the like «component within a corrosion-resistant, made of an alloy jacket at a below 930 C lying temperature is coextruded, so that a U_Si core is formed with a central empty space and that the core is fused to this alloy jacket or the like. " 8. A method for producing a nuclear fuel element according to one of claims 1 - k, with a hollow core made of uranium-silicon alloy in the delta phase U "Si, wherein the uranium-silicon alloy is cast in the form of a bar-like component, characterized in that first of all Bar-like component is extruded into a rod or the like with a central empty space, then the rod is heat-treated at about 750 to 900 ° C in a time interval of 2 - 300 hours in order to convert the alloy peritectoidally into the t delta phase, then the rod on predetermined 109824 / 05U measurements mechanically, processed and in the protective jacket with Slip fit is introduced. 9. A method for manufacturing a nuclear fuel element according to any one of claims 1-4, with a hollow core from uranium-silicon alloy inBeltaphase, U _"Si: wherein first a bar-like component is cast from the uranium-silicon alloy, characterized in that the bar-like member is coextruded within a corrosion-resistant alloy shell to form a U "Si core with a central void, the core being firmly bonded to the alloy shell, after which the nuclear fuel element is at a temperature of about 750 to 900 C in a time interval of 2-300 hours is heat-treated to convert the uranium-silicon alloy core peritectoidally into the delta phase. 10. The method according to any one of the preceding claims, characterized in that in addition a cover or shut-off component U Si is preferably fused, soldered or the like to the ends of the rod, in order to fill the empty space, in particular to close the middle empty space. 11. A method for producing a nuclear fuel element with a core made of uranium-silicon alloy in delta phase, U "Si according to claim k, characterized in that the uranium-silicon alloy is first cast into a rod or the like. The evenly distributed individual spaces 109824/0514 or pore-like individual spaces from a total of 3 to 25 $ des Rod volume has that then the rod at about 750-900 C • in the time interval of 2 - 300 hours of heat treatment · is subjected to peritectoidally transform the alloy into the delta phase, then the rod to predetermined dimensions mechanically processed and inserted into the protective jacket with sliding fit » 12. The method according to claim 11, characterized in that the preferably equally distributed pore-like or porous Spaces by introducing an inert gas into the uranium-silicon alloy is achieved in the molten state. 13 · Method according to claim 12, characterized in that the gas is blown into the molten alloy. lh. Process according to Claim 12, characterized in that the molten alloy is exposed to the gas atmosphere and the gas is introduced into the alloy in this way. 15 · The method according to claim 12, 13, 14, characterized in that that helium is used as Gaa. 16. The method according to claim 15, characterized in that the evenly spaced break rooms through introduction at least one substance generating the gas can be formed in the uranium-silicon alloy melt. 109824/0 5U 17 · method according to claim 16, characterized in that metallic magnesium is used as the gas generating substance. 109824/0514