film is mailed to the Health and Safety Laboratory at the Commission's New York Operations Office, where it is ashed in a vacuum furnace and the radioactivity in the ashes is measured. Through production line techniques, it is possible for the laboratory to count 400 to 600 such samples per day.

Fall-out Measurements in Test Site Area

In the area surrounding the test site, monitors made measurements of external gamma radiation, of airborne radioactivity, and of radioactivity in water. The results were as follows:

External gamma radiation. The highest measurements of external gamma radiation experienced in populated areas off the test site during Operation TEAPOT are given in the table below. The exposure is expressed in units of "Effective Biological Dose," which represents the best estimate of radiation dosage in terms of its biological effects. In calculating the effective biological dose, account is taken of reduction in exposure as a result of weathering and shielding by walls and buildings.

The operational guide established by the test organization in terms of the effective biological dosage for exposure of the public to radiation was 3.9 roentgens in any one year. This limit was not exceeded at any community nor at any place where people were living.

Airborne radioactivity. Although past experience indicated that the concentration of radioactive fall-out materials in the air is of secondary importance to the external gamma radiation, the air monitoring program was continued. The highest concentration of radioactivity in the air following any one detonation was at Ely, Nev. This amounted to about 6/100 of a microcurie per cubic meter averaged over the 28 hours that the material was present in significant quantities. The highest concentrations in air, averaged for the entire series, occurred at Ely, Nev. and Alamo, Nev., where the total additional radiation doses to the lungs from inhaling fall-out material were estimated to be about equivalent to that expected from breathing air containing normal amounts of naturally radioactive materials, for a period of several days.

Radioactivity in water. The highest concentrations of radioactivity in water measured during the spring of 1955 are shown below.

Locality

Concentration (Microcuries per milliliter ertrapolated to 3 days after detonation)

1.4 x 10-4

Upper Pahranagat Lake, Nev.

Waterhole near State (Nevada) Highway 25.

Meadow Valley (Nevada) Wash.......

9.2 x 10-5

3.3 x 10-5

The highest concentration noted in the table is about of the operational guide-an amount that is still considered safe even it the water were to be stored and used as the sole source of supply for a lifetime.

Fall-out Measurements Across the Nation

The National Monitoring System consists of a network of stations which collect and measure fall-out over the entire United States. Fall-out levels at distances away from the test site have been low, and generally have not exceeded more than one milliroentgen per hour. The collection stations in the network do not provide information on immediate dose rates, as do the monitoring units operating in the test site area. However, the information collected has varied scitific uses. It is needed by the AEC to compute and record the overall accumulation of radioactivity in the Nation as a result of tests. It is needed by the photographic industry and by scientists conducting experiments with low-level radiation, since these activities can be affected by even a very slight increase over the normal background radiation. The data also are used by meteorologists to trace air masses and check predicted trajectories.

CUMULATIVE FALLOUT IN U.S. FROM BEGINNING OF WEAPONS TESTS TO 5/20/55 BETA ACTIVITY, MILLICURIES PER SQUARE MILE EXTRAPOLATED TO 1/1/56

More than 17,000 samples were processed by the Health and Safety Laboratory from mid-February to the end of May 1955 and analyzed to determine the overall distribution of fall-out resulting from the 1955 test series.

Since 1951, more than 200,000 samples have been processed to provide cumulative figures on fall-out in the United States resulting from all known tests conducted to date. The data are shown on the above map.

It will be noted that the figures vary from 22 millicuries per square mile in California to 260 millicuries per square mile in Colorado. In its natural composition, the upper foot of soil in the United States contains about 1,000 millicuries of radium per square mile.

Civil Effects Experiments

During the current test series, the Civil Effects Test Group under the test organization conducted extensive field experiments to obtain needed information for civil defense. This was the largest civil effects program ever undertaken during test operations. The program comprised 10 scientific and technical experiments broken down into 47 projects involving 160 separate tests. Agencies participating with the AEC included the Federal Civil Defense Administration;

the Department of Health, Education and Welfare; the Department of Agriculture; the Department of Commerce and the General Services Administration. Scientific and technical personnel actively engaged included a total of some 200 medical doctors, physicists, biologists, geneticists, veterinarians, chemists, architects, engineers and other specialists.

The experiments in the Civil Effects Test Group are described under the following categories:

1. The evaluation and documentation of radiological fall-out data: This included use of the radiation telemetering system as described in the Sixteenth Semiannual Report of the Commission (January-June, 1954). Airborne radioactivity and meteorological data were recorded through the use of land lines and radio links from points up to 350 miles distant to a central point at the test site headquarters. In addition, a number of automatic radiation measuring and recording devices was placed in populated areas out to 350 miles in potential fall-out locations. Data were collected of radioactivity deposited over other off-site and on-site areas by employing aerial survey techniques.

Utilizing the data from earlier tests, a study was set up to determine the function of distance as related to fall-out exposure. Five arcs were extended from the Nevada Test Site out to a distance of 160 miles. Rabbits were placed at several distances and radiation inhaled by the rabbits was measured.

A field exercise was held to train and orient on-site and off-site radiological personnel in monitoring procedures during atomic explosions. The groups participating in this training were drawn generally from State radiological organizations. The programs included monitoring techniques of radioactive fall-out with survey instruments, mobile laboratory equipment, light aircraft, evaluation of a number of commercially produced radiation detection instruments, and investigations of gamma radiation intensities in various parts of residences constructed for the tests in probable fall-out

areas.

2. Biological and medical experiments: In this category, investigations were made to evaluate the effects of nuclear explosions on foods and foodstuffs. Bulk staples, canned foods, meat and meat products, semi-perishable foods and frozen food packages were exposed to develop information on immediate and long-range radiation effects. This study will be supplemented by a 2-year feeding program, in which the exposed food will be fed to experimental animals. The results will be used to develop permissible limits of nuclear radiations in food used under emergency conditions, and for the commercial market in peacetime. Resistance of glass, metal, plastic,

wood, paper, and other packaging materials to radiation, thermal and blast effects was also tested.

A number of biomedical experiments were designed to evaluate current medical data on blast phenomena, and to verify laboratory experiments. In a related project, a pilot test was developed in which rats were trained to move in certain maze patterns. These animals were again tested after exposure to determine the effect of noise shock on the efficiency of the animals to perform their learned routines in the maze patterns.

Biomedical and engineering experiments were combined to determine the design of physically resistant and biologically acceptable shelters and structures. Another phase of this work involved the distribution and density of missiles from explosion effects. Missile traps made of cork and plastic materials were placed both inside and outside the shelters and residences to determine the size, number and velocity of fragments per unit area produced from explosions.

3. Materials, utilities, structural and functional design projects: Tests were planned to study nuclear effects on residential, commercial and industrial structures and materials, shelters, utilities, services and associated equipment, mobile housing and emergency vehicles. Construction entailed completion of 4 two-story and 6 one-story residences, 7 commercial and industrial structures, and a number of special projects involving certain structural components. There were 15 to 20 indoor-type and 9 to 12 outdoor-type home shelters designed to test protection from blast loadings. Other tests included electrical installations, communications equipment, such as a standard commercial 250-watt AM radio broadcasting station, underground and surface installations of natural liquified petroleum gas and representative types of large machine tools, as well as a wide variety of safes and other record storage equipment.

Analysis of the results of these experiments is in preparation, and will contribute significantly to the knowledge necessary to work safely with nuclear energy in peacetime, and to improve techniques employed for self-protection against enemy action in the event of

war.

RESEARCH INVESTIGATIONS

Results of current experimental work offer a certain measure of optimism, not possible a few years ago, on the possibility of protection against and recovery from radiation. However, vital problems of the effects of radiation on living things are still unsolved, and extensive research continues at the Commission's major laboratories and at the participating universities, hospitals, and other institutions.

Advanced methods and procedures employing radiation as a tool have helped to increase fundamental knowledge of the biological