US3162528A

US3162528A - Production of uranium-carbon alloys

Info

Publication number: US3162528A
Application number: US53634A
Authority: US
Inventors: Williams Jack; Davis Charles Brian
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1959-09-08
Filing date: 1960-09-02
Publication date: 1964-12-22
Anticipated expiration: 1981-12-22

Description

United States Patent PRODUCTKON 0F URANIUM=CARBON ALLQYS Jack Williams, Ahingdon, and Charles Brian Davis,

Didcot, England, assignors to United Kingdom Atomic Energy Authority, London, England No Drawing. Fiied Sept. 2, 1960, Ser. No. 53,634 Claims priority, application Great Britain Sept. 8, 1959 3 Ciairns. (Cl. 7S122.7)

The invention relates to the production of uraniumcarbon alloys.

Methods of production of such alloys are described in United States Patent No. 2,569,225, British Patents Nos. 825,041 and 821,287.

A preferred method of producing such alloys is to heat a cold-compacted mixture of uranium and carbon powders, with or without an intermetallic compound of iron and uranium, to a temperature of 800 to 1125 C. to cause a solid-state reaction between the uranium and carbon.

We have now discovered, that the density of such alloys can be increased, and porosity decreased, by rapid heating of the cold-compacted mixture to a sintering temperature of 1000 to 1125 C., so that the heat generated by the exothermic reaction between the uranium and carbon is utilised in the sintering process. We have found that if the compact is plunged into a sintering furnace which is already at the sintering temperature, then the rate of heating is sufliciently fast to make use of this effect. If the compact is placed in a cold furnace, and the furnace is then heated up in the usual way, taking several hours to reach the sintering temperature, then the heat of reaction is dissipated. We have found that, using the method of this invention, the temperature of the compact rises above that of the sintering furnace and in fact rises above the melting point of uranium, so that a liquid phase reaction occurs which leads to the very high densities achieved. The actual temperature reached by the compact depends on the size of the compact but is within the range 1200-1450 C.

The uranium-carbon alloys which can be produced according to this invention may also include plutonium, which may replace part of the uranium in the starting mixture.

According to the invention, a method of producing a dense uranium-carbon alloy, which may also comprise plutonium, comprises cold-compacting a mixture of uranium powder and carbon powder and if desired plutonium powder, and then heating the said mixture to a sintering temperature by plunging it into a furnace heated to a temperature of 1000" C. to 1125 C., whereby the heat of reaction of the mixture causes its temperature to rise above the melting point of uranium.

We have found that the rate of rise of temperature of the compacted mixture when it is plunged into the furnace is very rapid and depends on the size of the compact. It is certainly greater than 100 C. per minute and may be as high as 500 C. per minute for small compacts.

The nature of the invention will be made more apparent by the following examples.

EXAMPLES I TO V Uranium powder of particle size to pass a 300 mesh British Standard test sieve was mixed with ultrafine graphite in proportions of 95.2% uranium powder to 4.8% graphite, by weight. Samples of this mixture were mixed with amounts of UFe varying from 0 to 15% by weight of the whole. The mixtures of uranium, graphite and UFe were then cold-compacted at 60 tons/sq. in. in tungsten carbide-lined dies to form compacts of various sizes. Each compact was placed in an alumina boat and passed rapidly into a vacuum furnace heated to 1100" 3,152,528 Patented Dec. 22,, 1964 "ice C. Each compact was estimated to reach a maximum temperature of 1200 C. to 1450 C. in less than 5 minutes. it was then heated at 1100 C. for 2 hours. The densities and porosities of the products are given in the following table, in which products of similar compositions, but sintered by placing each compact in an alumina boat in the cold furnace and then heating the furnace to 1100 C. at the rate of 300 C. per hour, with a half-hour degassing period at 550 C., are included for comparison.

Table I Weight percent of Density (gm./0C.)

whole Example UFeg 0 Fe Slow Rapid Theoretical heating heating EXAMPLES VI TO IX Similar mixtures to those of Examples I and IV were cold-pressed and sintered as before, except that the proportion of uranium powder was varied from 95.8 to 94.6% and that of graphite correspondingly from 4.2 to 5.4%. The results obtained are shown in the following table, in which products of similar compositions, but sintered by the slow heating method described in relation to, Examples I to V are included for comparison.

Table 11 Weight percent Density (gm/cc.) Weight of whole Example gerfctcfig 0 mixture G UFe Fe Slow Rapid Theoretical heating heating Tables I and II show that the density of the products is increased by the method of the invention, compared with sintering by slow heating.

We claim:

1. A method for producing a uranium-carbon alloy of high density and loW porosity comprising mixing a uranium metal powder and carbon powder with one another, cold compacting the mixture, passing the compacted mixture to a sintering zone maintained at the time of passing of the mixture at a temperature within the range of about 10001125 C., permitting the temperature of the compact in the sintering zone to rapidly rise for a short period of time solely as a result of the exothermic heat generated by the reaction of the mixture at a rate greater than about C. per minute to a temperature between about 1200-1450 C., and thereafter heating the mixture in said sintering zone at a temperature in the range of about 1000-1125 C. for a period of time suflicient t effect a complete sintering of the mixture.

2. A method in accordance with claim 1, wherein plutonium metal powder is mixed with the uranium and carbon.

=3 of the mixture at a temperaturewithin the rarigepf abput 10001125 C., permitting the temperature of the compact in the sintering zone to rapidly rise for a period of time not in excess of about 5 minutes solely as a result of the exotherriiic he'at efifat'ed by the reactionof the mixture at a rate greater than about 100 (3. per minute to a temperature between about 1200'1450 C., and thereafter heati 'rig the migrture in said ein'tering zone at a tempraturei'fi'the fa'rigeof about 1000 1125 C. for

a period of time sufficient to etfect a complete sintering of the mixture.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. A METHOD FOR PRODUCING A URANIUM-CARBON ALLOY OF HIGH DENSITY AND LOW POROSITY COMPRISING MIXING A URANIUM METAL POWDER AND CARBON POWDER WITH ONE ANOTHER, COLD COMPACTING THE MIXTURE, PASSING THE COMPACTED MIXTURE TO A SINTERING ZONE MAINTAINED AT THE TIME OF PASSING OF THE MIXTURE AT A TEMPERATURE WITHIN THE RANGE OF ABOUT 1000-1125*C., PERMITTING THE TEMPERATURE OF THE COMPACT IN THE SINTERING ZONE TO RAPIDLY RISE FOR A SHORT PERIOD OF TIME SOLELY AS A RESULT OF THE EXOTHERMIC HEAT GENERATED BY THE REACTION OF THE MIXTURE AT A RATE GREATER THAN ABOUT 100*C. PER MINUTE TO A TEMPERATURE BETWEEN ABOUT 1200-1450*C., AND THEREAFTER HEATING THE MIXTURE IN SAID SINTERING ZONE AT A TEMPERATURE IN THE RANGE OF ABOUT 1000-1125*C. FOR A PERIOD OF TIME SUFFICIENT TO EFFECT A COMPLETE SINTERING OF THE MIXTURE.