W A S H I N G T O N NEWS BUREAU
jliPOTOMAC POSTSCRIPTS ROBERT G. GIBBS, Associate Editor
AECs domestic shipments of radioactive and stable isotopes now reaching 50,000 mark total n p t i E rapidly increasing number of ap•*• plications of radiation detection instruments has caused this industry to grow by leaps and bounds. From 1946, w h e n t h e industry first reached significant size, until 1952, the number of employees has increased steadily and now totals over 2400. T h e dollar volume of sales has risen to $20 million a year. Concurrent with this growth has b e e n a steady increase in the n u m b e r of radioisotopes shipped by the Atomic Energy Commission to users all over t h e United States and its territories. As of June 1, A E C h a d m a d e almost 37,000 shipments of radioisotopes. A compilation by AEC shows that there were 29 companies engaged in manufacturing radiation detection instruments last year. Although over half h a d annual sales of less than $200,000, six h a d sales running from $ 1 million to $4 million. Five years ago t h e principal outlet of this industry was the AEC and its contractors. Increased use in other fields has lowered A E C purchases from 5 9 % to 2 7 % of t h e total output. Isotope Shipments Approach 50,000. From t h e time AEC began shipping isotopes in August 1946, 47,101 shipments of radioactive and stable isotopes have been sent out to various users. Over 10,000 have been sent in the past 11 months alone. These are sent from the Oak Ridge National Laboratory. Almost half of t h e radioisotopes consist of iodine-131, while deuterium oxide (heavy w a t e r ) is t h e leading stable isotope. T h e table shows the n u m b e r s of isotopes shipped from t h e time the program began through Nay 30. Many Varied Uses. A n AEC compilation of location and type of users of isotopes shows that these substances are used in all 48 states as well a s the District of Columbia, Alaska, Hawaii, Puerto Rico, a n d Panama. T h e major use of isotopes is in industrial firms. Almost 800 firms now use either the radioisotopes or stable isotopes in their operations. Medical institutions and physicians m a k e u p the second largest group, followed b y colleges and universities, federal and state laboratories, a n d foundations and institutes. As of May 30 there were 1623 users of radioisotopes and 312 w h o w e r e using stable isotopes. Many Foreign Shipments. Foreign shipments of radioactive isotopes h a v e now approached t h e 200O mark. As of t h e end of M a y shipments had b e e n m a d e to 44 nations all over the world. T h e first 10, 3348
in the order of decreasing number, are Canada, Denmark, Sweden, Japan, Brazil, Belgium, England, Australia, Argentina, a n d Cuba. Over one third of all shipments consisted of phosphorus-32. T h e other major isotopes shipped, in order of decreasing numbers, were iodine-131; carbon-14; cobalt-60; iron-55 and -59; sulfur-35; calcium-45; and strontium-89 and -90. Other isotopes account for less t h a n 1 0 % of total shipments. All isotopes s h i p p e d abroad were radioactive. No stable ones h a v e been sent.
J 1 1 1 1 1 1 1 j 1 1 1 1 1 I 1 1 1 1
I s o t o p e Shipments' 1 Radioactive iodine-131 phosphorous-32 carbon-14 sodium-24 sulfur-35 goId-198, 199 calcium-45 iron-55, 59 cobalt-60 potassium-42 strontium-89, 90 other subtotal Stable deuterium oxide (heavy water) deuterium ( hydrogen-2 ) boron-10, 11 helium oxygen-18 electromagnetic concentrated argon-38 subtotal
14,302 9,955 1,575 1,378 742 1,198 489 479 724 587 303 4,807 36,539
622 630 176 27 241 696 3 2,395
1 Shipments to A E C installations 1 radioactive 6,619 stable 1,548 1 Grakid total 47,101 a From Aug. 2 , 1946, to May 30, 1953 1 Diversified
Industrial
Applications.
Accurate measurements of the thickness of a coating laid over a base m e t a l a r e possible through use of a backscatter-type radioisotope gage. T h e measurement is effected by directing a b e a m of electrons to the surface of t h e base metal and measuring t h e intensity of the reflected b e a m . Similar readings are m a d e of t h e coated surface. T h e intensity of the reflected electrons is dependent on the atomic n u m bers of t h e coating compared to that of t h e base metal a n d the thickness of t h e coating. The advantage of the system, in addiCHEMICAL
tion to its accuracy, is t h a t there i s n o mechanical contact with t h e material b e ing measured. T h e b e t a radiation from strontium-yttrium-90 is commonly u s e d for this purpose. Typical applications a r e tin or zinc on steel; paper, r u b b e r , o r plastic sheet on steel calendering rolls; a n d lacquer on tin plate. Radioactive iodine-131 is u s e d to d e t e c t leaks in water lines. I t has t h e advantages of a short half-life a n d thus n o residual activity. I t also eliminates t h e need of tearing up floors to find t h e leaks. T h e s e properties are of great value in the m a i n tenance of industrial heat transfer a n d other similar equipment. Rapid, accurate measurements may b e made of wear o n cutting tools b y h a v i n g t h e tips of the tools irradiated in a n u clear reactor a n d measuring t h e activity of the chips cut b y t h e tool. Tungsten-185 is the radioactive isotope involved. O n e interesting side development involved i n t h e studies of t h e tools and cutting fluids was t h e discovery of organo-metallic compound formation under the conditions of high local temperatures and pressures e n countered during cutting operations. Determination of t h e completeness of mixing is often a relatively slow process involving various analytical techniques. T o shorten this procedure and t o save effort expended in overmixing, short-life radioisotopes a r e used. Manganese-54, with a half life of 5.8 days, has been used for this purpose in t h e mixing of a p i g ment and vehicle to form p a i n t . A host pf other applications are also known. Radioactive iron-59, for example, is usee! in friction a n d lubrication studies. T h e w e a i i n g down rate of firebrick, such as is used inside the steel shells of furnaces containing molten metal, m a y be d e t e r mined by sealing cobalt-60 pellets in t h e walls of t h e furnace when t h e y are built. As t h e furnace brick wears, t h e intensity of t h e radiation varies a n d furnishes a basis for determining t h e a m o u n t of wear. A related application concerns a determination of the rate of corrosion in pipelines and pressure vessels, thus warning of incipient failures. Cobalt-60 is also used to indicate heights of liquids in tanks a n d to control t h e level t o a very close tolerance. T h i s same isotope finds uses in radiography testing, as it provides for nondestructive testing u n der a variety of conditions. Tagging of catalyst beads with zirconium-95, which h a s a half life of 6 5 days, makes it possible to determine t h e circulation time of catalyst in cracking plants. High temperatures a n d pressures and a closed system make other measurement methods difficult. Antimony-124, which has a 60-day halflife, is used t o determine t h e interface between different petroleum products when they are transported in pipelines. T h e secondary (gamma) radiation properties of different geologic strata differ enough so that qualitative changes in t h e various strata in oil-wells m a y be determined. A fast neutron source is u s e d - a s the primary radiation source. AND
ENGINEERING
NEWS
