From: Drs. Conant, Compton, and Urey
War Department
United States Engineer Office
Manhattan District
Oak Ridge Tennessee
October 30, 1943
[Declassified June 5, 1974]
1. Inclosed [sic] is a summary of the report written by Drs. James B. Conant, Chairman, A. H. Compton, and H. C. Urey, comprising a Subcommittee of the S-1 Executive Committee on the "Use of Radioactive Materials as a Military Weapon." It is recommended that a decision be obtained from competent authority authorizing additional work pertaining to the use of radioactive materials in order that this country may be ready to use such materials or be ready to defend itself against the use of such materials. The following program is recommended:
a. Immediate formation of a research and study group at the University of Chicago under supervision of the present Area Engineer. Assignment to this group of competent individuals now working on dust and liquid disseminating munitions and field testing of chemical warfare agents from the National Defense Research Council.
b. Assignment of a competent Chemical Warfare Service officer to the Chicago Area Engineer, who would become familiar with, and work on the problem under study by the University of Chicago. This officer should be experienced in the practical use of gas warfare.
c. The responsibility of the above organization would be:
(1) Develop radiation indicating instruments, expand present facilities of the Victoreen Company, and prepare a trial order for instruments with this company.
(2) Make theoretical studies pertaining to the methods, means and equipment for disseminating radioactive material as a weapon of warfare.
(3) Conduct field tests in isolated locations, such as Clinton Engineer Works or Sanford Engineer Works, using a non-radioactive tracer material.
(4) Prepare an instruction manual for the use of, or the defense against, radioactive weapons. This manual would be similar to that now used by the Chemical Warfare Service for gas warfare.
(2) As a gas warfare instrument the material would be ground into particles of microscopic size to form dust and smoke and distributed by a ground-fired projectile, land vehicles, or aerial bombs. In this form it would be inhaled by personnel. The amount necessary to cause death to a person inhaling the material is extremely small. It has been estimated that one millionth of a gram accumulating in a person's body would be fatal. There are no known methods of treatment for such a casualty
Two factors appear to increase the effectiveness of radioactive dust or smoke as a weapon. These are:
(1) It cannot be detected by the senses; (2) It can be distributed in a dust or smoke form so finely powdered that it will permeate a standard gas mask filter in quantities large enough to be extremely damaging. An off-setting factor in its effectiveness as a weapon is that in a dust or smoke form the material is so finely pulverized that it takes on the characteristic of a quickly dissipating gas and is therefore subject to all the factors (such as wind) working against maintenance of high concentrations for more than a few minutes over a given area.
c. Possible Use by the Enemy.
It is felt that radioactive warfare can be used by the Germans for the following purposes:
(1) To make evacuated areas uninhabitable.
(2) To contaminate small critical areas such as rail-road yards and airports.
(3) As a radioactive poison gas to create casualties among troops.
(4) Against large cities, to promote panic, and create causalities among civilian populations.
For use in cities, it is estimated that concentrations would have to be extremely high to offset the shielding effect of buildings Doctors Compton and Urey, two members of the Committee, felt that radioactive material may be used by the Germans against United Nations in the autumn of 1943. Dr. Conant apparently does not concur in this opinion.
d. Possible Use by the United States.
It is the recommendation of this Subcommittee that if military authorities feel that the United States should be ready to use radioactive weapons in case the enemy started it first, studies on the subject should be started immediately. The possible military uses of radioactive materials follow:
(1) As a Terrain Contaminant. To be used in this manner, the radioactive materials would be spread on the ground either from the air or from the ground if in enemy controlled territory. In order to deny terrain to either side except at the expense of exposing personnel to harmful radiations Estimates indicate that these materials could be produced by the Germans in such quantities that each four days two square miles of terrain could be contaminated to an average intensity of radiation three feet above ground level of one hundred roentgens per day. One day's exposure (100 roentgens to the whole body) would result in temporary incapacitation, a lesser period of exposure in incapacitation to a lesser degree and one week's exposure in death. Effects on a person would probably not be immediate, but would be delayed for days or perhaps weeks depending upon the amounts of exposure. Exposure to five to ten times the above described concentration would be incapacitating within one to two days and lethal two to five days later. Areas so contaminated by radioactive material would be dangerous until the slow natural decay of the material took place, which would take weeks and even months. On a hard smooth surface some decontamination could be accomplished by flushing with water, but for average terrain no decontaminating methods are known. No effective protective clothing for personnel seems possible of development.
(2) As a Gas Warfare Instrument. The material would be ground into particles of microscopic size and would be distributed in the form of a dust or smoke or dissolved in liquid, by ground-fired projectiles, land vehicles, airplanes, or aerial bombs. In this form, it would be inhaled by personnel. The amounts necessary to cause death to a person inhaling the material is extremely small. An infintesimal amount accumulating in a person's body would be fatal in a few day to weeks depending upon the amount absorbed and its radioactivity. There are no known effective methods of treatment for such a casualty. Areas so contaminated by radioactive dusts and smokes, would be dangerous as long as a high enough concentration of material could be maintained. In these forms, the materials take on the characteristics of a quickly dissipating gas and it is improbable that heavy concentrations could be maintained for more than a few minutes time over a given area. However, they can be stirred up as a fine dust from the terrain by winds, movement of vehicles or troops, etc. , and would remain a potential hazard for a long time. These materials may also be so disposed as to be taken into the body by ingestion instead of inhalation.. Reservoirs or wells would be contaminated or food poisoned with an effect similar to that resulting from inhalation of dust or smoke. Four days production could contaminate a million gallons of water to an extent that a quart drunk in one day would probably result in complete incapacitation or death in about a month's time.
B. From Internal Sources
RESPIRATORY TRACT: Dr. Wollan has estimated that an accumulation of 10-3 curies of high-energy beta-ray active material would produce an exposure of about 100 r/day to the lungs. Unfortunately, there is no experimental data bearing directly upon the deposition of f products nor on the action of the beta-rays on the bronchial and alveolar surfaces. Particles larger than 1μ[micron]in size are likely to be deposited in nose, trachea or bronchi and then be brought up with mucus on the walls at the rate of 1/2 - 1 cm/min. Particles smaller than 1μ [micron] are more likely to be deposited in the alveoli where they will either remain indefinitely or be absorbed into the lymphatics or blood. The probability of the deposition of dust particles anywhere in the respiratory tract depends upon respiratory rate, particle size, chemical and physical nature, and the concentration in the atmosphere. Hence the probability of f products causing lung damage depends on all of these factors. While only fragmentary information is available, it is felt that the injury would be manifest as bronchial irritation coming on in from a few hours to a few days, depending on the dose. It would not be immediately incapacitating except with doses in the neighborhood of 400 or more r [roentgens] per day. The most serious effect would be permanent long damage appearing months later from the persistent irradiation of retained particles, even at low daily rates. It would seem that chemical gases could accomplish more and do it more quickly so far as the skin surfaces and lungs are concerned. The beta emitters would have more permanent effects -- starting months after exposure.
GASTRO-INTESTINAL TRACT: Beta emitting f [fission] products could get into the gastro-intestinal tract from polluted water, or food, or air. From the air, they would get onto the mucus of the nose, throat, bronchi, etc., and be swallowed. The effects would be local irritation just as in the bronchi and exposures of the same amount would be required. The stomach, caecum, and rectum, where contents remain for longer periods than elsewhere would be most likely to be affected. It is conceivable that ulcers and perforations of the gut followed by death could be produced, even without any general effects from the radiation.
BLOOD STREAM AND TISSUES: Beta and gamma emitting fission products may be absorbed from the lungs or G-I tract into the blood and so distributed throughout the body.
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DOCUMENT E [1943]
This document consists of 3 page
Copy of 5, Series A.
USE OF RADIOACTIVE MATERIAL AS A MILITARY WEAPON
Summarized from a report written by Doctors James
B. Conant, Chairman, A. H. Compton, and II. C. Urey,
comprising the Subcommittee of the S-1 Executive Committee.
a. Availability of Radioactive Material.
In the near future it should be possible to
produce in the United States quantities of radioactive
material at a rate equivalent in radioactive effect to one
ton of radium every four days. This material is
approximately one hundred thousand times more active than
radius. Consequently, a four-day production quantity would
weigh about twenty grams in a pure state, or not more than
one hundred pounds when mixed with a suitable chemical
carrier.
There is no way of estimating definitely what
the Germans are doing in producing such material. Very likely
they are further advanced in their production schedule but
probably will not be able to produce in quantities that are
expected to be available in the United States.
b. Use of Radioactive Material in Warfare.
(1) As a terrain contaminating material, the
radioactive product would be spread on the ground
and would affect personnel by means of intensive
rays similar to those produced by powerful X-ray
machines. It is estimated that if a four days'
production quantity (the equivalent of one tone of
radium) were evenly spread over two square miles
of average open terrain, one day's exposure to a
human being would result in temporary
incapacitation, and one week's exposure would
result in death. Effects on a person would not be
immediate, but would be delayed for days or
perhaps weeks. Five to ten times the above
described concentration would be lethal after one
day's exposure.
Areas so contaminated by radioactive material
would be dangerous until decay of the material
took place, perhaps for weeks or months. On a
hard surface some decontamination could be
accomplished by flushing with water, but for
average terrain no decontamination methods are
known. Further, no effective protective clothing
for personnel has been developed, which would
nullify the effects of the radioactive materials. (2) As a gas warfare instrument the material would be ground into particles of microscopic size to form dust and smoke and distributed by a ground-fired projectile, land vehicles, or aerial bombs. In this form it would be inhaled by personnel. The amount necessary to cause death to a person inhaling the material is extremely small. It has been estimated that one millionth at a gram accumulating in a person's body would be fatal. There are no known methods of treatment for such a casualty. Two factors appear to increase the effectiveness of radioactive dust or smoke as a weapon. These are: (1) It cannot be detected by the senses; (2) It can be distributed in a dust or smoke form so finely powdered that it will permeate a standard gas mask filter in quantities large enough to be extremely damaging. An off-setting factor in its effectiveness as a weapon is that in a dust or smog torn the material is so finely pulverized than it takes on the characteristic of a quickly dissipating gas and is therefore subject to all the factors (such as wind) working against maintenance of high concentrations for more than a few minutes over a given area. c. Possible Use by the Enemy. It is felt that radioactive warfare may be used by the Germans for the following purposes: (1) To make evacuated areas uninhabitable. (2) To contaminate small critical areas such as railroad yards and airports. (3) As a radioactive poison gas to create casualties among troops. (4) Against large cities, to promote panic, and create casualties among civilian populations. For use in cities, it is estimated that concentrations would have to be extremely high to offset the shielding effect of buildings. Doctors Compton and Urey, two members of the Committee, felt that radioactive material may be used by the Germans against United Nations in the autumn of 1943. Dr. Conant apparently does not concur in this opinion. d. Possible Use by the United States. It is the recommendation of this Subcommittee that if military authorities feel that the United States should be ready to use radioactive weapons in case the enemy started it first, studies on the subject should be started immediately. From consideration of the possible effects and uses of radioactive material in warfare, it is evident that considerable experimentation with actual field trials would be necessary to determine the optimum conditions under which radioactive dusts could be disseminated with lung contamination or ground contamination. Such tests could be very readily carried out by using very small, amounts of radioactive material (tracer amounts) and studying the concentrations in the air or on the ground by means of sensitive physical instruments which are now readily available. These studies could be carried out best by a group containing some men who are familiar with the particular project which is planning to produce this radioactive material, and others drawn from the National Defense Research Council, who are working on the developments of munitions and dissemination of dust and liquids, and still others from the NDRC who are familiar with the testing of chemical warfare agents. e. Defensive Methods Proposed for the United States. The Subcommittee feels that from a defensive point of view, one can consider it unlikely (the Chairman of the Subcommittee, Dr. Conant, feels that it is extremely unlikely) that a radioactive weapon will be used against the Continental United States. They further believe that if such a weapon here used against a populated industrial city, such as London, an automatic alarm would be provided by virtue of the fact that a concentration of material sufficient to cause serious damage to any portion of the population in a few hours, would also fog all photographic films and give strange effects in various pieces of equipment in the scientific establishments of the city. If the material came down from the air as a cloud of dust, it would also probably produce strange effects in the radar equipment. The eventuality of enemy use of radioactive material to render evacuated areas uninhabitable seems to the Subcommittee sufficiently great to warrant the issuance of special instructions to at least one officer in each Division of any Army which might be faced with such an eventuality. Such an officer should be familiar with the ways of detecting and understand the reading of certain instruments which would give the effective radiation, and should be prepared to advise on the movement of troops in such a way as to avoid bore than a passing exposure to high radiation. it would also be of great importance to see that the troops were equipped with the proper type of gas masks and that these masks were put on immediately so that dust could be kept out of the lungs. It is the recommendation of the Subcommittee that a special committee composed of Dr. Stafford Warren and Dr. R. S. Stone be asked to prepare a report on both the use of detectors in the field and instructions which might be issued to a divisional officer, explaining under what conditions troops might be moved through various areas and what methods of decontamination could be tried under certain special circumstances. In short, this special committee should prepare a manual outlining a doctrine somewhat similar to that which already exists for the use of gas officers, and it is suggested that either a divisional gas officer or some special officer attached to the Corps or Army Headquarters be charged with the responsibility for these defensive measures. Such officer, or officers, would need to have instruments available and be given authority to traverse all areas which previously had been occupied by the enemy.
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