radiographed with radioisotope "cameras" on ships, tanks, pipelines, and containment vessels. Such "radioeyes" also are used to tell whether the fuel in rockets meets the rigid requirements of uniformity so necessary for successful operation. Construction of a single ship often requires the radiographing of as many as 10,000 welds. The savings in rejects and

elimination of destructive tests for welds, casts, and other fabricated products, is significant. Even more important is the greatly reduced chance of failures and accidents. Another important factor is radiation beam inspection of rapidly moving packages, cans, sheet material, metal strip, and fluid products. Isotope gages have been developed to penetrate through or reflect from material to measure levels, content, thickness, or density of a number of kinds of products.

A broad scope of products now is controlled and improved by isotope gages. Since they permit products to be made much more uniform and of higher quality, the user or consumer benefits directly as well as indirectly through the assistance isotopes can give to improved efficiency and productivity to aid segments of the economy.

High intensity radiation is starting to receive its first routine uses, but its full development depends on considerable research. The intense radiation from large quantities of fission products may ultimately find use as a new industrial process reagent and create new products. Some types of grafted plastics, such as selective ion exchange membranes used in desalting sea water, can best be produced by irradiation.

Development of Radiation Instruments

Since the human senses cannot detect nuclear radiations except at extremely high levels, the development of systems of detection and measurement of radiation has been essential to development of the practical applications of radioisotopes. The design and manufacture of such instruments was the first branch of the private atomic energy industry established. Many instruments originally were designed

and manufactured in the Government's atomic laboratories, but immediately after the war the Commission supported development of commercial manufacture. Significant advances have been made by industry in the development of more stable and sensitive circuits for radioisotope measuring applications. By 1959 some 120 companies were manufacturing a variety of instruments, detectors, special components, and accessories.

Nuclear radiation detectors developed to date may be classified according to several types.

In pulse systems, the output of the detector consists of a series of signals, each of which represents the interaction of a nuclear particle or gamma ray with the detector. The wellknown Geiger counter is an example of a pulse detector. Another is the proportional counter which is able to identify different radioisotopes according to their characteristic radiations. Still another example is the scintillation counter which operates on the principle that when ionizing particles pass through certain crystals, liquids, or organic polymers, flashes of light (scintillations) are emitted. An electron multiplier phototube picks up the faint scintillations and amplifies the resulting pulses to be detected and identified by the measuring apparatus.

In non-pulse detection systems, the output is the average of the cumulative effects due to many interactions of radiation with the detector; no attempt is made to resolve the individual events. The current-producing ionization chamber is a good example; the output is proportional to the total ionization current produced within the detector. Another example is the photographic system. When a piece of film is exposed to radiation, the emulsion reacts in the same way as when struck by visible light. The amount of radiation can be estimated from darkening of the film. Colorimetric detection is another example. When radiation reacts with certain chemicals containing chlorine (i.e., trichlorethylene and water, or chloroform and water), hydrochloric acid is formed. This causes a change in color of certain dyes, and the degree of color change

produced is dependent upon the amount of radiation received.

Several other detector systems have been used for specialized problems. These include cloud chambers for laboratory studies, nucleartrack photographic emulsion plates, crystal conducting counters, chemical detectors, and colorimetric devices for detection of large doses of radiation. In addition, a number of systems have been designed to detect and measure neutrons. Most of these have used boron, lithium or cadmium, in conjunction with one of the detector types discussed (except colorimetric), to detect the secondary radiation resulting from neutron capture by these materials.

In the field of low level counting, university work on radiocarbon dating of archeological materials was important in early developments. Noteworthy in this field was the pioneering research on the screen wall counter by W. F. Libby at the Universities of California and Chicago. Libby's technique involved placement of the sample inside a counter that operated on the sensitive and simple Geiger principle.

In more recent years, some investigators have substituted acetylene gas synthesized from radiocarbon samples used in proportional counters for the screen wall counter. Other techniques are based on a variety of liquid scintillators that respond well to soft beta radiation when the sample is mixed with the liquid scintillators.

These developments in low-level counting are pointing a way for applying these techniques to industrial processing. Present-day instrumentation is suitable only for laboratory needs, and designs must be modified to meet the rigid requirements of industrial applications. Efforts toward development for low-level tracers in industrial processes are described in Chapter VII.

ISOTOPES DEVELOPMENT PROGRAM

Developments to date in applying radioisotopes and radiation to increasing human well being and to economic gains through progress in industry represent only the beginnings of

what can be accomplished. The contribution of this new tool to scientific work is broad and continuous, and the Commission through its research programs regularly supports agricultural, biological, medical, physical and chemical projects employing radioisotopes and radiation both through its national laboratories and through research contracts. The increasing potential for putting radioisotopes and radiation to work in industry for the public benefit has led to inauguration of a program to supplement private effort, and to accelerate achievement in this field. In May 1957, the Atomic Energy Commission accordingly laid the groundwork for an isotopes development program. In February 1958, the Commission authorized a $5 million budget for isotopes development activities, and in December of that year established the Office of Isotopes Development to carry out the program.

The Isotopes Development Program has the general purpose of attacking basic problems which are retarding more widespread use of radioisotopes and radiation. The program, in its early stages, is emphasizing short-term, exploratory development which demonstrates principles of application having broad interest and susceptible of extension to many elements of everyday life-applied agriculture, medicine, and industry. Full benefits from the new developments will be won only as private effort carries out the necessary engineering and other utilization studies required to extend the new technology into practical uses. On completion, results of all developmental work done under Commission sponsorship will be published promptly for use by all interested elements of the economy.

First, there is a need for fundamental techniques development studies to evolve more new fundamental methods, to determine reaction mechanics, and to devise new radiation measuring methods. Examples of this type of development involve neutron capture processes, prompt as well as decay radiations, positron annihilation processes, coincidence techniques, neutron scattering processes, etc., in addition to the better known procedures for using alpha, beta

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and gamma radiation. In the development of radiometric methods of analysis of nonradioactive components, the reactions must be analyzed and taken through technique development to determine such things as proper chemical forms for the radioactive elements, efficiency of conversion, and reaction rates.

Second, the industrial process radiation program is being directed toward developing the field of applied radiation in the United States.

The growth of the nuclear power industry is providing an accumulation of fission products that can be a valuable byproduct instead of an increasing storage problem. Useful applications of process high-intensity radiation now are only in the exploratory states. Eventually, use of radiation energy is expected to have national economic significance. To capitalize on the huge reservoir of radiation available from fission byproducts, the Commission has undertaken a series of contracts to survey potential uses of radiation in industry, and to study the technology and methods for efficient utilization in industrial processes.

Third, training in isotope technology is required to increase the numbers of research and industrial personnel acquainted with the technology of practical applications of isotopes and radiation. The Commission's training program

includes (a) development and establishment of courses to provide training in the characteristics of radioisotopes, their safe use, and general applications; (b) provision for intensive courses on particular areas of use; and, for industry, (c) seminars and symposia designed to increase management and professional knowledge of the contribution of radioisotopes.

Fourth, the Commission's production activities are being directed toward making available commercial quantities of isotopes at economic prices yet making it attractive for private enterprise to undertake producing the greater volumes of special radioisotopes that will be required for full-scale exploitation of this new tool.

Authorized contract projects. In addition to the work done at its national laboratories, amounting to about $800 thousand a year, and numerous contracts covering research in the agricultural, medical, and other scientific fields, the Commission has undertaken a program of 93 contract and grant projects totaling $3.76 million for work looking toward wider applications of radioisotopes and radiation, particularly in fields of public and industrial interest. These contracts and grants are listed in Appendix 3.

RADIOISOTOPE TECHNIQUES are applied to a wide range of problems in agricultural research, ranging from applied studies of immediate practical importance to abstruse basic investigations. Isotope techniques permit the solution of problems that cannot be approached in any other way; they often permit the solution of more routine problems faster and more cheaply than do conventional approaches. Isotopes have been of particular value in understanding the very complex biological-chemicalphysical processes of living creatures and plants which provide the basis of agriculture production.

PLANT STUDIES

The Commission supports basic studies on plant physiology and biochemistry, plant genetics and plant pathology. Generally speaking, this research aims at eventual agricultural benefits, but does not cover practical farming practice. Many thousands of studies in plant science have been published; this report describes only major areas of research.

Radiation Genetics of Plants

The production of improved agricultural and ornamental plant varieties requires many years of deliberate breeding and selection to obtain desired characteristics. The breeder needs a large pool of genetically variable source material for selective combination into a new variety. Ionizing radiation helps to provide this pool, since it produces rapidly a great variety of genetic changes in plant stocks.

Using radiation-altered stocks, abrupt improvements in resistance to disease have been

produced. Small improvements in yield or in maturation time of crops have been achieved. The synthesis of small, independent, but scattered changes into one new variety can give surprisingly good results. Favorable genetic changes make up, of course, only a tiny fraction of all the changes produced by radiation and the plant breeder still must accomplish patient and careful elimination and selection.

Irradiation of seeds used extensively in the United States has produced a number of promising mutations. Two new plant varieties obtained in this way have been formally released to plant breeders for practical agricultural use. One, the "Sanilac" bush navy bean, in several years of testing, out-produced the parent variety by approximately 30 percent per acre, and, in addition, required fewer days from planting to harvesting. The other is an improved variety of peanut released to commercial sources this year. The peanut has higher yield and greater disease resistance.

Ionizing radiation also is used to produce somatic mutations in plants such as fruit trees which can be propagated with cuttings or grafts. Another technique involves using radiation to fragment chromosomes-genetic materials in reproductive cells-to permit recombining genes or sections of chromosomes in desired crosses. This technique has been successfully used in introducing genes for leaf rust resistance into wheat.

Disease-resistant strains have been reported in experiments with wheat, oats, and flax. High-yield dwarf forms of cereal grasses have been observed which suffer less wind damage than do customary strains. Encouraging results are reported on attempts to use mutation to eliminate a factor toxic to livestock from

certain otherwise useful forage plants. Fruit trees grown in low levels of gamma radiation for several years and permitted to return to normal growth, are being analyzed for possible useful mutations.

Two beneficial mutations have been reported in such experiments on peach trees. One branch on a Fairhaven peach tree bears fruit which ripens approximately 10 days earlier than normal. A branch on a different tree ripens its fruit some 3 weeks later than normal. These two radiation-induced mutations may lead to increasing by more than a month the season over which the fresh fruit can be available.

Photosynthesis

One of the best known applications of radioactive tracers to biological problems has been to the study of photosynthesis. In some respects photosynthesis may be regarded as the single most important chemical reaction in the world since it is the life process of plants that ultimately provides the energy for almost every type of living organism. In the photosynthetic process, plants absorb electromagnetic energy (light) using the green pigment (chlorophyll) in the leaves. This energy is used for converting inorganic carbon dioxide and water into energy-containing food substances such as sugars and starch. All food consumed by humans comes initially from the photosynthetic reaction in green plants.

Photosynthesis has been studied for almost 200 years. Until 1945, however, about all that was known was that light energy absorbed by the cholorphyll was used to split water with the production of a reducing agent and an oxidizing agent, the latter finally producing the oxygen gas evolved in photosynthesis. The reducing power in some way was used to convert the inorganic carbon of carbon dioxide into organic materials, a process termed carbon dioxide fixation.

In 1945 reactor-produced radioactive carbon 14 became available as a tool for photosynthesis research. In the succeeding years, it per

mitted a major breakthrough in the study of carbon dioxide fixation. The general experimental approach is to give a photosynthesizing plant carbon dioxide in which part of the carbon is carbon 14. Samples of the plant are killed after various periods of time, an extract prepared, and the various chemical compounds in the extract separated by a process called paper chromatography. Any compound containing carbon 14 must have been derived from the carbon dioxide taken in by photosynthesis. In this way it has been possible to identify ultimately each of the steps involved in the fantastically complicated process by which carbon dioxide from the air is converted into the organic compounds of the plant.

The process by which water molecules are split up in photosynthesis is very poorly understood. There is no useful radioactive isotope of oxygen available. However, scientists at the University of California, Berkeley, have recently developed a technique for this work. Photosynthesis experiments are carried out using water containing heavy oxygen, oxygen 18, instead of ordinary oxygen 16. The compounds produced are separated by paper chromatography and then irradiated in a proton beam from a cyclotron. This converts the stable oxygen 18 into radioactive fluorine 18. Any radioactive compounds which appear must contain oxygen produced from the photosynthetic splitting of water. This new technique involving atomic energy offers an excellent chance of completing the story of photosynthesis.

Plant Metabolism

Metabolism is generally defined as the sum total of all the chemical reactions occurring in an organism. Thousands of scientific papers have been published in recent years describing research in which radioactive tracers have been used in the study of specific plant metabolic processes.

Recent studies indicate, for example, that the mechanisms involved in plant synthesis of certain fatty acids is considerably more compli