US3039000A - Radiation shield structures and their production - Google Patents

Description

United States Patent ce 3,039,000 RADIATION SHIELD STRUCTURES AND THEIR PRODUCTION Richard Kielfer and Karl Sedlatschek, Reutte, Tirol, 5 Austria, assignors to Schwarzkopf Development Corporation, New York, N.Y., a corporation of Maryland 7 .No' Drawing. Filed Sept. 6, 1957, Ser. No. 682,294

1 '4 Claims. (Cl. 250108) This invention relates to radiation shields of the type required for intercepting radiation from radioactive substances, X-ray, and the like radiation sources, including isotope containers.

In the past, lead and a solid solution of tungsten, copper and nickel have been principally used as radiation shields for intercepting radiation of such radiation sources.

The present invention is based on the discovery that a solid solution or alloy of tungsten and uranium of a composition containing essentially 50% to 95% tungsten and 5% to 50% of uranium or uranium-rich alloys, provides an ideal radiation shield for such radiation sources. As used herein in the specification and claims, all proportions are given by weight.

The desired alloys or solid solutions of tungsten and uranium, or uranium alloys, may be provided in a variety of ways. As an example, powder particles of tungsten are compacted, and the tungsten powder compact is infiltrated with molten uranium or a molten uranium alloy, by melting an infiltrant body of uranium or uranium alloy While it is in contact with the porous tungsten compact, and heating the contacting parts until the uranium content difiuses and forms a solid solution with the tungsten content. The heating and infiltration of the compact and the uranium or uranium alloy is carried on in an oxidatiomsuppressing space such as either under vacuum or under an atmosphere of noble gas such as argon or helium. The tungsten powder compact may be sintered before subjecting it to infiltration and diliusion with the uranium or uranium alloy infiltrant.

Alternatively, the desired shield may be produced out of a mixture of powder particles of tungsten and powder particles of uranium or uranium alloy, by compacting the properly proportioned mixture of such different metal particles and heating the compact to a temperature at ,7

which the uranium or uranium alloy content of the compact forms a liquid phase which fills all the pores of the compact, and its tungsten and uranium contents diffuse or form a solid solution with each other.

Such infiltrated and diffused or compacted and diffused compacts of 50% to 95% tungsten and 5% to 50% uranium, exhibit a density of about 19, and they may be readily machined by standard metal shaping machines such as millers, lathes, drills, grinders, polishers, and the like.

Below are given specific examples of desirable radiation shield bodies of the invention:

Example 1 Powder particles of tungsten are compacted in a die cavity having the shape of the desired shield structure, such as a shield container, to provide a compact having 40% porosity, or the pores of which form 40% of itsv volume. An infiltrant body of uranium is brought in contact with the tungsten compact, and the composite aggregate so formed is placed in an infiltrating furnace the space of which is maintained under vacuum until the compact and the infiltrant are heated within 50 C. to 100 C. above the melting temperature of the uranium infiltrant so as to cause it to melt and infiltrate into the pores of the compact; The infiltrating compact is maintained in such furnace space at the raised infiltrating tempera- 3,039,fi00 Patented June 12, 1962 is thus obtained a shield body consisting of tungstenuranium alloy containing approximately 60% tungsten and 40% uranium. Example 2 Powder particles of tungsten are compacted in a suitable die into a cylindrical compact which is then sintered at 1000 C. to yield a sintered tungsten compact, the pores of which constitute 12% of its volume. An infiltrant body of uranium having a volume corresponding to the pores of the tungsten compact is placed in contact with the tungsten compact. The compact with the infiltrant in contact therewith is heated in a furnace under vacuum to above the melting temperature of the infiltrant, thereby melting the infiltrant and causing it to infiltrate all the pores of the tungsten compact. The infiltrated compact is kept in the furnace under vacuum until all the tungsten and uranium content of the compact diffuse and form a solid solution with each other. The resulting shield body consists of an alloy containing tungsten and 10% uranium.

Example 3 There are prepared powder particles of a uraniumaluminum alloy containing 90% uranium and 10% aluminum. A mixture of 80% of tungsten powder particles and 20% of such uranium-aluminum alloy particles is then compacted in the die cavity of a suitable die to provide a compact of the desired shape. The resulting shaped compact is then heated in a furnace under an atmosphere of noble gas such as argon, maintained below atmospheric pressure, until all the different metal contents of the compact diffuse and go into solid solution with each other. The resulting body consists of a tungsten-uranium-aluminum alloy, containing about 80% tungsten, 18% uranium and 2% aluminum.

Bodies similar to those described above may be made with uranium alloys containing as an alloying metal up to 10% aluminum.

The new radiation shield bodies of the invention described above are not only efiective as shields for intercepting radiation from radioactive sources, but they are also desirable for other applications. Thus, the fiact that they may be readily machined, makes it possible to use such bodies in applications requiring heavy metal bodies, such as balancing weights, fly weights, and the like.

The features and principles underlying the invention described above in connection with specific exemplifications will suggest to those skilled in the art many other modifications thereof. It is accordingly desired that the appended claims shall not be limited to any specific features or details shown and described in connection with the exemplifications thereof.

We claim:

1. In combination with a body containing a source of nuclear radiation, a radiation shield surrounding said body for intercepting radiation from said body, comprising a shaped shield structure having 100% density and consisting essentially of 50% to tungsten alloyed with 50% to 5% uranium, said shield structure consisting of a sintered skeleton of powder particles formed of the tungsten content of said body, and an infiltrant metal consisting of uranium filling all the pores of said skeleton, the infiltrated skeleton having been heated to cause a substantial amount of the tungsten and infiltrant metal of the body to diffuse into and form a solid solution with each other.

2. In combination with a body containing a source of nuclear radiation, a radiation shield surrounding said body for intercepting radiation therefrom comprising a shaped shield structure having 100% density and consisting essentially of 80% to 95% tungsten alloyed with 20% to 5% of uranium, said shield structure consisting of a :sintered porous skeleton of powder particles consisting essentiallyof tungsten and an infiltrant metal consisting principally of uranium filling all the pores of said sintered skeleton, the uranium-infiltrated skeleton having been heated to cause a substantial amount of the infiltrant metal to diffuse into and form a solid solution with the tungsten of said skeleton.

3. The combination as claimed in claim ,2, the uranium of said infiltrant containing up to 10% of aluminum.

4. The combination as claimed in claim 2, all of said infiltrant metal consisting essentially of uranium.

References Cited in the file of this patent UNITED STATES PATENTS Maiden May 22, 1928 Reinhardt Sept. 20, 1932 Kochring Oct. 19, 1937 Henzel et a1. May 10, 1949 Kurtz May 31, 1949 Morrison Dec. 25, 1951 Swift Oct. 12, 1954 Rough et a1. Feb. 21, 1956 Keeler et al. Apr. 24, 19 56 Tittle Nov. 6, 1956

Claims (1)

1. IN COMBINATAION WITH A BODY CONTAINING A SOURCE OF NUCLEAR RADIATAION, A RADIATION SHIELD SURROUNDING SAID BODY FOR INTERCEPTING RADIATION FROM SAID BODY, COMPRISING A SHAPED SHIELD STRUCTURE HAVING 100% DENSITY AND CONSISTING ESSENTIALLY OF 50% TO 95% TUNGSTEN ALLOYED WITH 50% TO 5% URANIUM, SAID SHIELD STRAUCTURAE CONSISTING OF A SINTERED SKELETON OF POWDER PARATICLES FORMED OF THE TUNGSTEN CONTENT OF SAID BODY, AND AN INFILTRAANT METAL CONSISTING OF URANIUM FILLING ALL THE PORAES OF SAID SKELETON THE INFILTRATED SKELETON HAVING BENN HEATED TO CAUSE A SUBSTANTIAL AMOUNT OF THE TUNGSTEN AND INFILTRAANT METAL OF THE BODY TO DIFFUSE INTO AND FORM A SOLID SOLUTION WITH EACH OTHER.