US2442617A

US2442617A - Carrier for radioactive material and improved method of making the same

Info

Publication number: US2442617A
Application number: US646144A
Authority: US
Inventors: Rosenblum Solomon
Original assignee: Canadian Radium and Uranium Corp
Current assignee: Canadian Radium and Uranium Corp
Priority date: 1942-10-31
Filing date: 1942-10-31
Publication date: 1948-06-01
Anticipated expiration: 1965-06-01

Description

June 1, 1948. 5 RQSENBLUM 2,442,617 CARRIER FOR RADIO-ACTIVE MATERIAL AND iMPROVED METHOD OF MAKING THE SAME Filed Oct. 51 1942 NEGATIVE l METAL flu METAL QMMVENTOR. BY MO CKr fl w/1A ATTORNEYS Patented June 1, 1943 CARRIER FOR RADIOACTIVE MATERIAL AND IMPROVED IMETHOD OF MAKING THE SAME Solomon Rosenblum, Princeton, N. 1., assignor to Cana dian Radium & Uranium Corporation,

New York, N. Y., a corporation of New York Application October 31, 1942, Serial No. 464,144

4 Claims.

My invention relates to a new and improved method of incorporating radio-active material into a carrier, and a new and improved impregnated carrier of radio-active material.

The principal objects of my invention are to incorporate radio-active material in a carrier which is made of relatively inert material, so that said carrier will be inert to acids and many other chemicals; to incorporate into a carrier, either pure radium, or a radium alloy or a radium compound or other radio-active material; to incorporate the radio-active material in a carrier which can be made of light-permeable or transparent material, such as glass; to concentrate the incorporated radio-active material at or adjacent one or more free or exposed surfaces of the carrier; and to provide a simple andimproved method for incorporating radio-active material in the carrier.

The improved article of manufacture is not limited to any method of making the same.

Other objects of the invention will be stated in the annexed description and drawing which illustrates a preferred embodiment thereof.

The drawing is a diagrammatic view which illustrates the method of incorporating the radioactive material into the carrier.

As an example, the carrier 3 is made of insulating material, whose resistance decreases with a rise in temperature. While the invention gen salts of silver and of thallium, and cuprous halogen salts. I can also use certain natural minerals, such as calcite and witherite. Calcite or calcspar is a common natural form of calcium carbonate, which is found in natural crystalline form. Witherite is a natural barium carbonate. The carrier may be of any size or shape.

The annexed drawing shows, as an example, a glass carrier 3, which may be of any shape. In the specific embodiment disclosed, the glass carrier 3 is in the form of a block which has parallel planar faces 3a and 31). However, the carrier 3 may be of any shape, including a hollow or solid cylinder. The drawing is not to scale, as it is wholly diagrammatic.

A solid layer 4 of the radio-active material is deposited upon the face 3a of the carrier 3. Said layer 4 may be an amalgam of the radioactive material.

As one example, the layer 4 may be a solid layer of radium bromide, which may contain some water, but is preferably wholly or substantially free from water. I can use radium chloride, radium nitrate, radium nitrite, radium perchlorate, etc. Whenever I refer to any substance or to other details, as part of a working example, the invention is not limited thereto.

. I prefer to use radium salts which are soluble is not limited to the use of a carrier which is made of glass, I prefer to use a carrier which is made of glass, because the electrical resistance of glass diminishes rapidly with an increase in its temperature. Indeed, glass behaves almost as an electrolyte, in that its resistance diminishes with a rise in temperature, especially when the glass softens or begins to soften or is close to the softening temperature.

While the invention includes the use of any type or composition of glass, I prefer to use a glass which has some conductivity at 20 C. I may use the type of heat-resistant glass, which is a borosilicate glass which contains substantially no metals of the magnesia-lime-zinc group and substantially no heavy metals. I can use the barium glasses. I can use the type of heat-resistant glass which begins to soften at about 600 0., especially if pressure is employed. I can use the type of glass which begins to soften under pressure at about 800 0.

Instead of glass, I can use other solid materials which have some degree of electrolytic conductivity in the solid state at suitable elevated temperature. For example, I can use the halo.

in water, such .as radium bromide and radium chloride, but the invention is not limited thereto. In order to form the layer 4, I can use either an aqueous solution of radium bromide, or I can use a solvent other than water. For example, I can use a solution of radium chloride in ethyl alcohol.

For example, in order to form the layer 4, I can use a solution of radium bromide in distilled watenin the proportion of one milligram of radium bromide in 0.5 cc. of distilled water. This solution is applied to the face 3a of the carrier 3. The solution may be applied to theentire face 3a, or to any selected part or parts thereof. The solution is applied, drop by drop,"

to the face 3a, or to any selected area or areas thereof. The carrier 3 is preferably heated to about 50 C., before applying said solution thereto. The solution may be confined in any suitable manner to the selected area or areas of the face 3a, until the solvent has evaporated. In order to evaporate the solvent rapidly, if said solvent is water, the carrier 3 may be heated to about C. after the solution .has been applied, thus evaporating the water and providing a very thin layer 4.

The carrier 3 is now located between the electrodes I and 2. These electrodes I and 2 may be made of any suitable conducting material. In the practical example whose details are stated herein, said electrodes I and 2 can be made of pure nickel.

The electrodes I and 2 are applied respectively to the outer face of the layer 4, and to the face 3b of the carrier 3, under suitable pressure, in order to secure good electrical contact. This pressure may be 500 grams per square centimeter, or more. as is desired.

If the carrier 3 is made of material which has The pressuremay be as high low conductivity at normal temperature,- .s aid carrier is heated to a suitable operating temperature in order to increase its conductivity, pref erably before the electrodes I and 2 are applied.

although the carrier 3 may be heated, to the.

operating temperature, either wholly or partially, after the electrodes I and 2 are applied. The carrier 3 is heated to a temperature of about 300 C.-800 0., depending upon the composition of the material of said carrier, if it is made of material which has low conductivity at normal temperature. v

In-using reat-resistant glass, at suitable opere ating temperature is about 500 C. to 600 C. At this operating temperature, the heat-resistant glass carrier 3 becomes sufficiently conductive so that current passes between the electrodes I and 2, through the solid layer 4 and through the carrier 3. Likewise, at said temperature of 500 C.. :600 C. the radio-active material can enter the carrier, to be incorporated in said car rier. The electrode I-is connected by a Wire 5 to the positive terminal of a suitable source of constant and direct current and the electrode 2 is connected by a wire 6 to the negative side of said source. The difference of voltage between the electrodes I and 2 can be between 500-1000 volts. The current through the layer 4 and the carrier 3 can be about one milliampere', although it may be greater or less.

I do not exclude the use of a carrier 3 which has sufficient conductivity at ordinary temperatures of about C., such as certain types of glass.

I prefer to use a constant unidirectional current. However, I can use other types of current, such as an intermittent-unidirectional current. I do not exclude the use of alternating current.

Under the action of the direct current to which-this working example is specifically directed, the radio-active material migrates from the layer 4 into the adjacent portion of the carrier 3. For most purposes, it is suflicient toincorporate a very small amount of the radioactive material into the carrier. In the practical example stated, the equivalent of about two milligrams of radium, as detected by radic activity measurement, is incorporated into the carrier 3 per square decimeter of the surface of the carrier.

If the carrier 3 is made of transparent glass,

it remains more or less transparent after the radio-active material has been incorporated therein. In the practical example above given, in which the operating temperature was 500- 600 C., the passage of a'curren-t of about one milliampere, under a voltage of about 500 volts, was continued for a period of about 30 minutes.

The radio-active material is sharply concentrated adjacent the face or wall 3a, which is a decided advantage in securing a maximum radio-active effect because the radiations, cs-

active material were exposed in a thin layer on said surface. Nevertheless, and as further stated herein, the incorporated radioactive material cannot be removed from the carrier, without removing the surface material of the carrier. Glass can block the alpha rays, but I prevent such blocking by incorporating radioactive material into the carrier, very close to an exposed face of the carrier.

The. test of the finished product is the application' of a solvent for the radio-active material, or subjecting the carrier 3 to some other treatment which would ordinarily'removeithe radio-active material, if it were not suitably-in:

corporated into the carrier 3. For example, after the radium has been suitably incorporated into the heat-resistant carrier 3, according to the practical example stated herein, the face 3a may be washed with water or acids, without removing any of the radium.

.By continuing the passage of the current, the

' radium or other radio-active-material is carried further into the carrier 3, away from the face 3a. The invention includes such extended passage of the current, although l'prefer'to concentrate the radioactive material in a selected volume of the carrier 3.

The impregnatedcarrier may be used for many purposes. The alpha or beta radiations vigor ously ionize the air adjacent the face 3a.; The

carrier 3 may therefore be used as a guide member over which a web of paper or cloth or the like can be guided, because the alpha or beta radiations will vigorously ionize the air, thus preventing the formation of static electricity which is frequently caused by friction. This'is particularly valuable in many industries, especially in rotogravure printing, in which the ink includes inflammable and volatile material. The face 3b can be fused or otherwise connected'to any suitable support or member. For example, the face 31) can be fused to the interior wall of a tube which. contains a gas or gases, in" which it is desired to ionize the gaseous filling. Said tube may be evacuated in order'to reduce the pressure therein to any desire low pressure. Said vacuum may be very high. For convenience, the

' erasable markings which are made with compositions which include a fluorescent, pigment or dye, such as calcium sulphide or rhodami ne 'B, so that said markings will be visible in darkness. These markings can be made on a separate carrier, which can be applied to said face or faces.

Impregnated carriers of various sizes and shapes are also very useful for many medical purposes.

Atypical heat-resistant glass consists of 30.5 Of SiOz, 11.9% 01 B203, 2% of A1203, 0.1% Of FezOs, 0.2% of (780, 0.2% of M90, 3.8% of NazO, 0.6% Of K20, and 0.7% Of AS203, but I can use other types of Pyrex glass or other glass.

At the temperature and pressure utilized, the glass is preferably at the softening temperature, or close to said temperature. At the operating temperature which may be as high as 800 C., as above mentioned, the radium salt may be fused or unfused. For example, radium bromide has a melting point of 728 C., and radium chloride has a melting point of about 1000 C. However, the original shape of the glass carrier is not changed by the incorporation of the radio-active material therein.

While no chemical combination is formed between the carrier and the radio-active material, the carrier is combined with the radio-active material, in the sense that said radio-active material is incorporated into the carrier.

I have described a preferred embodiment of my invention, but it is clear that numerous changes and omissions can be made without departing from its spirit.

I claim:

1. A method of incorporating radio-active material from an unfused radium salt into a non-metallic and unfused carrier whose electrical resistance diminishes with rise in temperature, said carrier being substantially free from radium, which consists in passing a current through said unfused radium salt and through said unfused carrier while said unfused salt contacts with said unfused carrier, said current 'being passed through said unfused radium salt and through said unfused carrier at a temperature which is sufilciently elevated and under a sufliciently high potential to pass a current through said unfused salt and said unfused carrier and to incorporate said radio-active material into said unfused carrier interiorly of the face of said unfused carrier which contacts with said unfused radium salt, said temperature and voltage and the period of said incorporation being selected so that said radio-active material is incorporated into said carrier so close to said face that the alpha particles which are emitted by said incorporated radio-active material pass out of said carrier; said carrier being glass, said temperature being substantially 300 C.-800 0., said current being unidirectional and its positive terminal being applied to said radium salt, and its negative terminal being applied to said carrier, and the voltage of said current being substantially 500-1000 volts.

2. A method according to claim 1, said current being substantially one milliampere.

3. A method according to claim 1, in which said radium salt is radium bromide.

4. A method according to claim 1, in which said radium salt is radium bromide, and said current is substantially one milliampere,

SOLOMON ROSENBLUM.

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

UNITED STATES PATENTS Number Name Date 821,655 Lieber May 29, 1906 1,210,731 Viol Jan, 2, 1917 1,644,370 Gaschler Oct, 4, 1927 1,832,607 Zworykin Nov. 17, 1931 2,198,733 Leibig Apr, 30, 1940 FOREIGN PATENTS Number Country Date 110,479 Australia May 9, 1940 278,347 Great Britain May 10, 1928 OTHER REFERENCES Zeitschrift fur Physikalische Chemie, vol. A173, pages 321-344, (1935).