the Berkeley accelerators or for rebombardment in the pile for making heavier elements.

Several new isotopes of einsteinium and fermium have been discovered at Berkeley by bombarding berkelium 249 and californium 249 and 252 with alpha particles from the 60-inch cyclotron. Among the isotopes produced by this method in the einsteinium group were the isotopes 249, 250, 251 and 252 and in the fermium group, the isotopes 250 and 252. Californium 244, berkelium 247 and 248, and mendelevium 256 also were discovered.

Knolls Atomic Power Laboratory under a joint program with Atomic Energy of Canada, Limited, has carried on studies of highly irradiated plutonium samples. Einsteinium and fermium have been found in the samples, as well as lighter transuranic elements.

Fluorescence in the actinide group of elements was observed for the first time by the nuclear chemistry group at Berkeley. Fluorescence has long been known in the lanthanide group, and it was disturbing that this phenomenon had not hitherto been observed in the actinide elements, since theory tended to correlate the characteristics of these two groups of elements.

METALLURGY

Studies of Metal Defects

Lattice irregularities. Studies have been conducted at the Atomics International laboratories of North American Aviation in an attempt to describe and identify the kinds of disruption introduced into a metallic lattice by irradiation.

Studies have developed techniques using electron irradiations that permit introducing only the simplest lattice irregularities, namely single atoms knocked from their normal lattice sites into poistions between other atoms in their normal lattice sites. By knowing exactly what imperfections are caused, experimenters can subsequently identify their behavior in more complex situations. In this way it has been possible to work-harden a specimen mechanically and then irradiate it with approximately 1 million volt electrons and cause a partial recovery of the work-hardening, i. e., the irradiation softens the metal. This is assumed to be accomplished by the introduction of a nonequilibrium concentration of lattice vacancies. This observation is in contrast to the usual behavior under irradiation where the changes are most often found to be similar to additional work-hardening.

In another approach, researchers described the very complex disruptions in the structure of metals that occur during the stopping of fission fragments or other very energetic massive particles. The

particular question for which a description is sought is the configuration of the atoms in the neighborhood of the energetic particle after it has come to rest. There are currently two theories concerning this arrangement and several experiments are under way in an attempt to decide between these alternates.

Plastic deformation. Single crystals of metals deform under application of stress by mechanisms generally referred to as "slip" and "twinning". Both mechanisms involve atomic movements on specific planes and in specific directions in the crystal lattice. The type of planes on which slipping or twinning occurs, their abundance or multiplicity in the crystal, and the critical stresses necessary to initiate these processes, all have a bearing on the plastic deformability of the metal and on the manner in which the grains align themselves in such operations as rolling, extruding, etc.

A study of these deformational processes in alpha-uranium single crystals at Argonne National Laboratory indicated a considerably more complex situation than generally found in more common metals. of higher crystal symmetry. Under compression at room temperature no less than two slip systems and three twinning systems have been identified; still others are known to exist. Some of the twinning systems discovered are not usually found in metal crystals.

Basic Studies in Liquid Metal Fuel Program

One of the most important metallurgical problems in the Liquid Metal Fuel Reactor Program is selecting a material for the reactor vessel, piping, and heat exchanger. Since low chromium steels have been widely used in the boiler and oil industries, they appeared attractive for this use.

Experiments at Brookhaven National Laboratory in which these steels were tested in contact with circulating uranium-bismuth liquid fuel have shown that in the hotter sections of the circulating systems constituents of the steels were dissolved in the liquid metal and then were deposited in the cooler regions. The result was that circulation was stopped by the formation of metallic plugs in the piping. However, if 200 to 250 parts per million of zirconium were dissolved in the liquid metal, the transfer of material was very markedly reduced.

Investigators believe that the zirconium is adsorbed on the surface of the steel, and that nitrogen, an impurity in the steel, diffuses to this surface and reacts with the zirconium to form the very stable compound, zirconium nitride. Apparently, this layer acts as a barrier against further dissolution of the constituents of the steels.

This explanation has been checked by studies in the mercury system. It has long been known that additions of titanium to mercury in mercury boiler plants reduced the corrosion of steels by the hot mercury, but the reason was not known. An X-ray study of the surfaces of steels in contact with mercury containing titanium has shown the presence of titanium nitride and titanium carbide. The discovery suggests that in this liquid too, the reduction in corrosion is due to the formation of a barrier layer.

If this method of reducing the corrosion of steels by the uraniumbismuth fuel system proves to be adequate, an inexpensive material will be available for construction of components of the uraniumbismuth liquid metal fuel reactor.

Other Studies

Radiation damage to graphite. The detailed mechanism of the effects of neutron irradiation on graphite has been under investigation for a number of years in several commercial laboratories, but, due to the great complexity of the observed data, no consistent model for this process has been formulated until recently. Low temperature irradiation and annealing experiments performed during the past year have provided the necessary additional data to outline a definite mechanism. This model, discussed in a paper prepared jointly by investigators from the Argonne National Laboratory and the Atomics International Division of North American Aviation, and given at the International Conference on Peaceful Uses of Atomic Energy in Geneva, August 1955, was semiquantitative for low to moderate neutron irradiations, but only qualitative for very heavy neutron doses.

High purity uranium metal. Basic metallurgical studies require a much higher purity of uranium than is generally used in reactors. In order to provide this degree of purity, scientists at Argonne National Laboratory developed an electrolytic refining process and melting procedure that produces metal with a total impurity content of about 40 parts per million. The metal is now being produced at Argonne National Laboratory in sufficient quantities to satisfy the needs of various researchers in the United States in addition to several requests from European laboratories.

Scientists at Argonne have used this material in developing a unique process for preparing single crystals of alpha uranium. These crystals are being used for such basic studies, as on self-diffusion, irradiation damage, and plastic deformation.

Biology and Medicine

During the last 6 months new methods were developed for using atomic energy products and techniques to treat cancers, the effects of radiation upon living creatures were further determined, and studies of methods of waste disposal yielded promising new knowledge. The examples of research findings reported here came from only a few of the projects which are under way in national laboratories and at Commission-sponsored projects in universities, colleges, hospitals, and other research institutions.

A contract was signed for construction of a research hospital, to include a medical nuclear reactor, at Brookhaven National Laboratory. The Commission helped assure safety and health protection at this spring's weapons tests in the Pacific. It has continued its strong and detailed assistance to the Federal Civil Defense Administration, has kept its informative material in this field up to date, and is helping to provide local civilian defense groups with training tools.

BROOKHAVEN NATIONAL LABORATORY MEDICAL RESEARCH CENTER

A contract for construction of a new Medical Research Center at Brookhaven National Laboratory, Upton, Long Island, N. Y., was awarded in June to the Malan Construction Corp., Long Island City. Total cost of the Medical Research Center including a medical reactor will be approximately $6.4 million. The one-story Medical Center will cover a gross area of 118,000 square feet and will house a 48-bed research hospital, an industrial medical branch, and research departments in medical physics, pathology, microbiology, biochemistry and physiology.

The Brookhaven medical reactor, the first designed exclusively for medical research and treatment, will incorporate unique features to insure wider medical application of neutrons, flexibility of treatment, and availability of special short-lived radioisotopes. The medical reactor will be housed in a steel, gas-tight building, 60 feet in diameter and 54 feet high, covering a gross area of 6,000 square feet.

Completion of construction of the Medical Research Center is scheduled for 1958.

CANCER RESEARCH PROGRAMS

At the Argonne Cancer Research Hospital, Chicago, Ill., several lines of approach have been used in cancer therapy.

Yttrium 90 pellets developed initially at the Argonne National Laboratory, Lemont, Ill., have been surgically implanted to irradiate

and destroy the pituitary gland in animals and humans suffering from cancers that have been transported from their original sites to other parts of the body.

Radioactive cesium has been used to treat tumors by sewing through the tumor mass with extremely thin tubing through which the cesium is flowed. Numerous problems in measuring the radiation dose have been encountered but are slowly being overcome.

The production, localization, and the effects of antibodies formed specifically against tumor cells, are being studied by means of radioisotopes. The aim is to learn whether and how these substances could be used for successful therapy, and also to learn more about the immunochemical similarities among tumors of different origin. It was recently shown that tumor antibodies, tagged with radioiodine, were localized to a greater extent by cancer cells than by normal cells. The cancerous growth was not retarded, however. Another observation was that animals fasted after injection had localized more of the antibody in the tumor cells than had animals fed normally. Oxygen uptake in treated tumor cells was greater than in untreated tumor cells. The high energy sources for cancer therapy-the cobalt 60 teletherapy unit and the Van de Graaff generator-are continually being altered and refined for more effective application. Radiations produced by them are being used routinely to treat patients with primary or secondary cancers.

A beam-bending device also is being constructed for use with the 60 million electron volt linear accelerator which will allow more precise radiation of tumors in humans.

The nature of the capacity to resist leukemia, a cancer of the blood, is being studied in several strains of mice. It is hoped that the results of these investigations will explain the protective action afforded by the reticuloendothelial system (blood cells in the liver, lungs, bone marrow, etc.) against this disease and will throw light upon factors involved in blood formation.

Animals whose pituitaries have been excised have been used for investigating the plasma factors that control red blood cell formation. A plasma fraction has been prepared which appears to contain these factors, and emphasis is being given to investigating their physiological behavior as well as their isolation.

At Brookhaven National Laboratory the general problem of the application of short-lived radioactive isotopes to diagnosis, therapy, and the study of biological effects of radiation on whole cells and small regions within cells is under study. Primary interest is given to radioactive isotopes which are ingested by, or injected into, patients and thereby become what have been termed "internal emitters." The short-lived isotopes presently used in the program have radiological half-lives ranging from approximately 20 minutes to a few hours.