US2580360A

US2580360A - X-ray shield

Info

Publication number: US2580360A
Application number: US575569A
Authority: US
Inventors: Morrison Philip
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-01-31
Filing date: 1945-01-31
Publication date: 1951-12-25
Anticipated expiration: 1968-12-25

Description

P. MORRISON Dec. 25, i951 X-RAY SHIELD Filed Jan. 5l,

. INVENTOR. Plz zn Z 179 Morrison BY fwdm torne z/- Patented Dec. '25, Y1951 X-RAY SHIELD .Philip Morrison, Pittsburgh, Pa., assignor tothe United States of America as represented by the 'United States Atomic Energy Commission Application January 31, 194.5, .Serial No. .575,569

9 Claims. .(Cl. Z50-108) 4-My invention krelates to a shield that serves as `an efficient protection against X-rays, gamma rays and other penetrating radiations.

It is generally known that the heavier elements are more satisfactory as shields from X-rays,

gamma .rays and other` penetrating radiations,

than are the lighter elements, since the heavier elements can be used in thinner sections. Lead of suitable thickness has been usedY most widely for shielding operators and patients from the undesirable effects of such penetrating radiations. For high radiation intensities of penetrating rays, such asobtained from a cyclotron target, radium, or nuclear ssion, appreciable thicknesses of lead are required, forrexample, of the order of several inches, making the shields very expensive, heavy and difficult to handle. Although uranium is a heavy metal, its use as a shield from X-rays, gamma rays and other penetrating radiations has been avoided in the past, because of an undesirable characteristic of uranium, the metal being itself an emitter of alpha and beta rays.

An object of my invention is to provide a shield that is highly-efficient in preventing the transmission of X-rays, gamma rays and other penetratingradiations.

VAmore specific obj ect of my invention is to vnul-- lify the above-mentioned undesirable characteristic of uranium, namely, its own emission of alpha and beta rays, thus making uranium suitable as a shield for protection against X-rays, gamma rays and other penetrating radiations.

These and other objects will become more apparent from the following description.

The effectiveness of a metallic shield for protection against X-rays, or gamma rays of energy greater than 2 m. e. v., that is, its absorption coeiiicient, is proportional to Where Z is the atomic number of the element, P the density of the element and A the isotopic mass number of the element. The particular power of the factor Z is further dependent upon the particular X-ray energy and the absorption region. It can be determined mathematically that for two million electron volt radiations, corresponding to about 0.006 Angstrom, uranium is superior to lead as an absorber of X-rays. More specifically, for two million electron volt (2 m. e. v.) radiations, an equivalent shield of uranium is per cent thinner than a tungsten shield, and 45 per cent less thick than a shield of lead for the same absorption. Uranium is even more superior for radiations more penetrating,thatiagreater than enerf gies of 2 m. e. v. For frequencies somewhat less than the equivalent .of .2 m. e. v. radiation, uranium retains .an Vadvantage over lead lin Ashielding but :to a lesser vdegree in view .of .the ,applicationof the .expression for energies in the neighborhood of 1 m. e. v., that is, the expression'involves vthe first power of v'Z instead of Z2 asin the case for energies of;2'm.. e.v. andabove.

Inasmuch as uranium is itself an emitter of alpha and beta rays, its use as a shield for X-rays and the like has not'hitherto been considered.

have found, however, that the above-mentioned disadvantage can be rovercome `by coating the yuranium metal with a heavymetal pigment, such as, for example, red lead. This pigment coating effectively absorbs both the alpha and be'ta vradiations from the uranium. Thus, the combination of a surface coating of lead lwith a thick uranium absorber possesses outstanding advantages in the control of penetratingradiations such as X-rays andgamrna rays as Well as alphamore eicient than lead 'for radiation ireguencies.

corresponding, for example, to two million electron Volts (2 m. e. v.) energy, or more. Furthermore, I have eliminated the inherent disadvantage of uranium used as a shield material, because of its own emission of alpha and beta rays, by coating the uranium with a material that absorbs these self-generated radiations, such as, for example, lead.

For an illustration of an embodiment of the invention in accordance with the patent laws, reference is made to the attached drawing in which:

Figure l is a schematic plan View of a shield Wall made in accordance with the invention together with a radiation source; and

Figure 2 is a fragmentary cross-sectional view of the shield wall of Figure 1.

As illustrated in Figure 1, the shield wall 4 is employed to absorb and shield the radiations emanating from an X-ray or gamma ray source 6. As shown in Figure 2, the wall 4 consists of a sheet 8 of uranium, on the outer surface of which is a relatively thin layer I0 of another heavy material. such as lead in the form of a red-lead pigment.

It should be noted that the above-described embodiment of the use of uranium as a shield is merely illustrative and not limiting, insofar as my invention is concerned. Other modification will be readily suggested to those skilled in the art after having had the benefit of the teachings of my invention. YFor example, instead of using uranium metal as a shield, an alloy, or perhaps a compound, containing a large percentage of uranium, may be used instead. Furthermore, instead of painting the uranium surface with a heavy metal pigment, such as red lead, a thin sheet of. lead or other suitable absorbing material such as bismuth, may be used as a` 'surface sheet either adjacent to or separated from the uranium', for the purpose of absorbing alpha and beta rays. In short, any material having Ia relatively high absorption coeiiicient for alpha and beta rays may be used. For these reasons, my invention shouldvnot be limited except insofar as set forth in the following claims.

I claim:

1.fA shield for substantially preventing the transmission of X-rays, gamma rays and other penetrating radiations, comprising a uranium metal base and a coating of heavy metal on said base, said coating consisting of non-radioactive elements of a density at least equal to that of red lead.

2. A shield for substantially preventing the transmission of X-rays, gamma rays and other penetrating radiations, comprising a uranium containing base and a coating of heavy metal pigment on said base, said'coating consisting of nonradioactive elements of a density at least equal to that of red lead.

3. VA shield for substantially preventing the transmission of X-rays, gamma rays and other penetrating radiations comprising a sheet of uraniumtogether with a surface sheet of lead.

4. Al shield for substantially preventing the transmission of X-rays, gamma rays and other penetrating radiations comprising a sheet of uranium and a sheet of material having an absorption coeiicient for alpha and beta rays at least equal to that of red lead, said material consisting of non-radioactive elements.

5. A shield for substantially preventing the transmission of X-rays, gamma rays and other penetrating radiations, comprising a sheet of ura-V nium and a red lead pigment coated on the sur- 'face of said sheet.

6. In combination with a source for producing penetrating radiations, such as X-rays and gamma rays, a protective shield for absorbing said rays and preventing transmission thereof through said shield comprising a sheet of uranium together with a sheet of material having a relatively high absorption coefficient for alpha and beta rays emitted by said uranium sheet said material consisting of non-radioactive elements of a density at least equal to that of red lead.

7. In combination with a source for producing penetrating radiations, such as X-rays and gam.. ma rays, a protective shield for absorbing said rays and preventing transmission thereof through Said shield, comprising a sheet of uranium together with a sheet of heavy non-radioactive metal having an absorption coefficient for alpha and beta rays at least equal to that of red lead, said last-named sheet being furthermost from said source. v

8. In combination with a source for producing penetrating radiations, such as X-rays, and gamma rays, a protective shield for absorbing said rays and preventing transmission thereof through said shield, comprising a sheet of uranium and a coating of heavy non-radioactive metal pigment of a density at least equal to that of red lead on the surface of said uranium sheet to absorb alpha and beta rays emitted by said uranium sheet.

9. In combination With a source for producing penetrating radiations, such as X-rays and gamma rays, a protective shield for absorbing said rays and preventing transmission thereof through said shield comprising a sheet of uranium and a coating of red lead on the surface of said uranium sheet to absorb alpha and beta rays emitted by said uranium sheet.

PHILIP MORRISON.

REFERENCES lCITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,815,922 Lapof July 28, 1931 1,902,474 Ungelenk Mar. 21, 1933 1,918,996 Weger July 18, 1933 2,183,799 Dillehay et al. Dec. 19, 1939

Claims

1. A SHIELD FOR SUBSTANTIALLY PREVENTING THE TRANSMISSION OF X-RAYS, GAMMA RAYS AND OTHER PENETRATING RADIATIONS, COMPRISING A URANIUM METAL BASE AND A COATING OF HEAVY METAL ON SAID BASE, SAID COATING CONSISTING OF NON-RADIOACTIVE ELEMENTS OF A DENSITY AT LEAST EQUAL TO THAT OF RED LEAD.