US2990274A - Uranium-titanium-niobium alloys - Google Patents

Description

United States Patent 2,990,274 URANIUM-TITANIUM-NIOBIUM ALLOYS Sherman Greenberg, Chicago, Ill., assignor to the United States of America as represented by the United Slates Atomic Energy Commission No Drawing. Filed June 16, 1958, Ser. No. 742,446 1 Claim. (Cl. 75-122.7)

The present invention is concerned with uranium-base alloys and more particularly relates to uranium-base alloys containing titanium and niobium.

Uranium is not resistant to corrosion; therefore one object of the present invention is to so improve the properties of uranium and uraniumrich alloys as to enhance the corrosion resistance thereof and render the same useful for various purposes for which uranium and uranium alloys now in use are not satisfactory or eiricient.

Still another object of this invention is to produce uranium-titanium-niobium alloys, which are useful as fuel elements in nuclear reactors, such as disclosed in U.S. Patent No. 2,708,656 to Fermi et al.

Other objects and advantages of the present invention will be apparent from the following description, taken in connection with the appended claim.

The present invention is directed to a ternary alloy of uranium, titanium and niobium, particularly one containing from about 2 /2 to 6 wt. percent titanium and about 1 to 2. wt. percent niobium. Our tests indicate that the optimum composition of the alloy for use in a nuclear reactor is about 3 wt. percent titanium and 1 /2 wt. percent niobium.

In Patent No. 2,743,174 it is shown that binary alloys of uranium and titanium are much more resistant to corrosive attack by water than is uranium alone. I have found that the addition of a relatively small amount of niobium to the binary alloy described in the patent improves greatly its resistance to corrosion and that the ternary alloy maintains its integrity many times longer than does an alloy containing no niobium.

The following chart illustrates the advantages obtained by the new alloys.

after an relapse of at least twice the time in which the binary alloy failed.

It is believed that the samples of ternary alloy remain intact because the niobium acted to prevent damage by corrosion product hydrogen, thereby preventing formation of cracks.

Below about 2 /2% titanium the alloy has appreciably poorer corrosion resistance than with a higher amount. Above 6% titanium the corrosion resistance is probably satisfactory, but the alloy becomes brittle and therefore unsuitable for use in a reactor. Optimum percentage of niobium is about 1 /2% niobium, although amounts ranging from 1 to 2% are operative to obtain the results desired.

The chart also shows that the alloy according to the present invention is much more resistant to corrosion than is the ternary alloy containing 5% zirconium and 1 /2% niobium, which is used in fuel elements for the Experimental Boiling Water Reactor at Argonne National Laboratory. Corrosion of that alloy was about 10 times greater than that of the ternary alloy containing titanium.

The chart also shows the heat treatment to which each alloy was subjected. A comparison between the results shown for the alloy according to my invention with several different heat treatments and the zirconium-containing alloy with about the same heat treatments indicates that my alloy is much less sensitive to heat treatment than is the zirconium-containing alloy. This statement also applies to the ternary alloy as compared to the binary alloy.

These new alloys may be conveniently prepared by melting together the required amounts of uranium, titanium and niobium in a suitable refractory crucible, as for example a graphite crucible. Melting should be in the absence of oxygen or moisture, as for example in v-acuo, and heating may be by inductive heating which facilitates mixing of the metals.

It will be understood that this invention is not to be limited to the details given herein, but that it may be modified within the scope of the appended claim.

What is claimed is:

An alloy which is resistant to corrosion by water at Temp., 1 Corrosion Composition 0. Time rate. mg./ Remarks cmfl/day U- 3% Ti 1 260 Sample failed in 10 to 20 Sample failed by cracking.

l-2 wee s. U3% Ti 2 260 Sample broken into several pieces. U%% Ti-1%% Nb 1 150 In view of result, no test was made at 260 C. 150 15.7 days 0 I I LT-3% Til} Nb 1 260 Tests continuing 1 Sample in excellent condition at after 40 days. this time. U-3% Tl-1%% Nb 2 260 Tests continuing 1 Do.

after 5 days. U3% Ti- 136% Nb 5 260 Tests continuing 10 Sample in excellent condition.

after 22 days. 150 10.4 days 0 U6% Tl1%% Nb 1 260 1.7 days 80 Test sample was beginning to crack when test was discontinued. U5% Zr1%% Nb 1 200 One month 10 to 15 sampletihcrnmbling after about one mon U5% Zr-l%% Nb 2 260 Two months 6 Cracking atnld chipping after about one mon U5% Zr1} Nb 4 260 Up to 14 days"..- 17-30 Clifikillg develops in from 5 to 14 ays.

1 Quenched from 1000 C.

1 Quenched from 1000 0.; aged 400 C.2 hours. quenched from 750 C.

4 Quenched from 725-750 0.

260 C. containing 3 weight percent titanium and 1 /2 weight percent niobium, the remainder being uranium, which alloy has been quenched from a temperature from 750 C. to 1000" C.

(References on following page) A comparison between the results shown for the binary alloy and the 3% titanium ternary alloy at 260 C. indicates at once the great advantage of the ternary alloy. The corrosion rate is reduced to a tenth of that of the binary alloy and the sample is still in good condition 2,990,274 3 V 4 References Cited in the file of this patent OTHER REFERENCES UNI BMI-971 Corrosion Evaluation of Binary Uranium A1- TED STATES PATENTS loys in Water at 100 C., U.S. AEC, Oak Ridge, Tenn.,

2,743,174 Keeler et at 24, 1956 December 1954, pages 17-20. (Copy in Scientific Li- 2,888,343 McGeary et a1 May 26, 1959 5 bury) WAPD-PWR-PMM-601, Document pu-bl. by Atomic FOREIGN PATENTS Energy Comm., February 1, 1956, page 10. Copy in 537,159 Canada Feb. 12, 1957 I 75/122.7.