ATOMIC TEST EFFECTS
IN THE
NEVADA
TEST SITE REGION
UNITED STATES
ATOMIC ENERGY COMMISSION
JANUARY 1955
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CAMP MERCURY, NEVADA February, 1955
A MESSAGE TO PEOPLE WHO LIVE You are in a very real sense active participants in the Nation's atomic test program. You have been close observers of tests which have contributed greatly to building the defenses of our own country and of the free world. Nevada tests have helped us come a long way in a few, short years and have been a vital factor in maintaining the peace of the world. They also provide important data for use in planning civil defense measures to protect our people in event of enemy attack. Same of you have been inconvenienced by our test operations. At times some of you have been exposed to potential risk from flash, blast, or fall-out. You have accepted the inconvenience or the risk without fuss, without alarm, and without panic. Your cooperation has helped achieve an unusual record of safety. In a world in which free people have no atomic monopoly, we must keep our atomic strength at peak level. Time is a key factor in this task and Nevada tests help us "buy" precious time. That is why we must hold new tests in Nevada. I want you to know that in the forthcoming series, as has been true in the past, each shot is justified by national and international security need and that none will be fired unless there is adequate assurance of public safety. We are grateful for your continued cooperation and your understanding.
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TABLE OF CONTENTS
- Foreword
- The Record of Past Tests
- The Spring 1955 Series
- The Flash of Light
- The Sound or Blast
- Fallout from the Atomic Cloud
- Location of Radiation Monitors
- Prospectors and Miners
- Tests and the Weather
- Claims for Test-Caused Damage
- Where to Get General Information
- Appendix
The Record of Past Tests
Thirty-one atomic fission weapons, weapon prototypes, or experimental devices were fired in Nevada from January 1951 to January 1955. All were relatively small in explosive power. They ranged from less than one kiloton up to considerably less than 100 kilotons. (A kiloton is equal to 1,000 tons of TNT.)
The forces released by test detonations in Nevada are very small compared to the tremendous forces released by the large fission and hydrogen weapons tested in the Pacific. So-called "H-bombs" are not tested in Nevada. Our large fission bombs, the President has said, are more than 25 times as powerful as the weapons with which the atomic age dawned (or approximately 500 kilotons) and hydrogen weapons are in the range of millions of tons of TNT equivalent (or in megatons).
Despite their relatively low yield, Nevada tests have clearly demonstrated their value to all national atomic weapons programs. Because of them we now have big bombs, and smaller ones too; in fact, a whole family of weapons. Because of them our Armed Forces are stronger and our Civil Defense better prepared.
Each Nevada test has successfully added to scientific
knowledge needed for development and for use of atomic
weapons, and needed to
strengthen our defense against
enemy weapons.
Staging of some tests in Nevada, instead of carrying out all of them in the distant Pacific, also resulted in major savings in time, the most important factor, and in manpower, and money.
An unusual safety record has been set. No one inside Nevada test site has been injured as a result of the 31 test detonations. No one outside the test site in the nearby region of potential exposure has been hurt.
There were instances of property damage from blast, such as broken
windows. Some cattle and horses grazing within a few miles of the
detonations suffered skin deep radiation burns, but the damage had no
effect on their breeding value nor the beef quality of the cattle.
THE SPRING 1955 TEST SERIES
The new series, scheduled to begin in mid-February, will conform generally with the pattern of the Spring 1953 series in Nevada.
Those who live near the test site know that experience in each series and technical developments of one kind or another have brought improved controls and procedures for each series. During almost two years since the last continental series, past experience has been minutely studied and certain engineering and technical improvements have been found practical.
Any atomic detonation, even though small enough to be fired in Nevada, involves powerful forces. The low level of public exposure to the off-site effects of Nevada detonations has been made possible by very close attention to a variety of on-site and off-site procedures.
It has been found possible, by studying past experience and through new technical developments, to improve several of these procedures. Taken together, these changes add up to a considerable improvement, and are expected to provide not only continued assurance of public safety but also to reduce public exposure to a minimum.
The key operating improvements include: Improved forecasting of wind speed and directions; improved methods of predicting blast and fall-out intensity and location; reducing fall-out by means such as yield limitations under various conditions and by using higher towers; and intensified off-site radiological safety operations.
For example, in the past test towers were not taller than 300 feet. It has now been found practical to use 500-foot towers and at least four of that height will be used in the 1955 tests solely to reduce fall-out on the nearby region. The higher towers will keep the fireballs further from the ground, decreasing the formation of relatively heavy radioactive particles, which tend to fall-out near the site of detonation. Towers of 300 feet and less will be used only for lower yield shots.
More stringent requirements have been established for weather conditions which will be accepted for a detonation, particularly with regard to wind speed and direction. As a result there may be more postponements, particularly last minute postponements.
No shot in the forthcoming series will exceed the yield of shots in the Spring 1953 series in Nevada.
There will, however, always remain a possibility of off-site effects from flash, blast, and radioactive fall-out. The potential exposure of the public will be low and it can be reduced still further by continued public cooperation.
Much of the remainder of this booklet is devoted to defining the off-site effects and the exposure you may be asked to accept, to tell you of the Test Organization's constant efforts to protect the public, and to help you avoid or reduce any exposure.
THE FLASH OF LIGHT
Exposure to Flash
If you look directly into the sun or at a photographer's flash bulb, you get black spots in front of your eyes and you can't see for a few seconds or a few minutes. If you were much closer to the sun or if you used binoculars, greater eye damage might result. Common sense precautions will protect your eyes from the bright flash of an atomic test.
On-site the thermal (heat) waves which accompany flash can injure eye tissues and cause permanent eye damage if the eye looks directly at the fireball. This is also true in the air immediately above the test site. At shot time all personnel on or above the test site wear extremely dark glasses or turn away; binoculars are prohibited; and road traffic is halted.
Off-site the flash can cause "black spots", so that momentarily you can't see, or it can startle you. This startling, or dazzling, effect can be experienced at night for hundreds of miles. The greatest caution needs to be used by drivers of vehicles or the pilots or aircraft who might easily have an accident if momentarily unable to see, or if they were simply startled.
The brightness of the light striking your eyes depends, of course, on whether it is day or night, whether there is direct line of sight to the fireball, on distance, on atmospheric conditions, and to some extent on the power of a detonation.
A majority of Nevada shots must be in the predawn hours of darkness and will require public precautions against flash.
Past Experience With Flash
No instance of serious eye damage has been reported, on-site or off-site. Observers on mountain peaks, who did not wear dark glasses, have reported temporary blind spots.
For persons outside the nearby area, flash is only an interesting phenomenon. The flash has been seen in Las Vegas in daytime. Predawn shots have been seen in Kalispell (Mont.), in West Texas, and on the Pacific Coast.
Off-Site Warnings and Procedures for Flash
Casual or commercial air flight above the test site is prohibited. The CAA will try to stop air traffic within the surrounding area up to 80 miles (because of flash, radiation, and air traffic congestion).
Some shots--because of time of day, very low yield, or their positioning--will not require off-site precautions. If precautions are indicated, the test management will announce the approximate time of the shot and recommend precautions. These may include the following:
Day or predawn shots: Do not use binoculars or rifle scopes or other optical systems to look toward the test site at shot time. Do not look toward the test site at shot time unless you are wearing dark sunglasses.
Daytime shots: If the fireball will be visible on highways within a radius of up to 60 miles, a general warning will be issued and insofar as possible those driving toward the test site will be warned of time of shot and advised to stop and face away.
Predawn shots: If fireball will be visible on direct line to highways within a 60-mile radius drivers going toward the test site will be warned to stop at shot time. Persons in parked cars, or observers elsewhere, will be advised to look the other way or to wear two pairs of darkest variety sun glasses.
If a shot is postponed every effort will be made by radio and highway patrol to advise you so that you may proceed, or may know if it will be fired at a later time.
THE SOUND OR BLAST
The Phenomenon of Blast
Shock waves go out in all directions from the detonation. Some strike the earth and are dissipated. Some bounce back to earth from various atmospheric layers. If they reach earth at an inhabited point they may be felt or heard.
Waves curved back to earth by the ionosphere, which is an atmospheric layer over 50 miles above the earth, have been recorded on very sensitive instruments 100 or more miles from the target area. There is no evidence that they have been heard at that distance or have caused any damage.
The ozonosphere, a layer 20 to 35 miles above the earth, bends waves
back at distances from 60 to 150 miles. Usual ozonosphere wind
directions cause these waves to reach St. George and Cedar City,
Utah, in winter and Bishop, Calif., in summer. Every shot fired in
Nevada has been heard either in St. George or Bishop, or both. The
slowly oscillating, ozonosphere-borne waves can be as strong as
others which break windows and still cause no damage. The sound is
similar to distant thunder without sharp cracks or bangs.
Waves propagated through the troposphere (up to 6 miles high) cause sharp cracks and bangs in the nearby site region. Off-site damage to buildings or windows within 100 miles has resulted only from waves in the troposphere. The strength of waves hitting in the nearby region depends on temperature and wind structure of the atmosphere, on shot altitude, and on yield. Shot altitude and weather dictate where the shock will strike. Wind direction causes directional variation in blast. If the weather creates a sharp focus in the atmosphere, blast intensity at a particular point may be severe.
Inasmuch as there is a possibility of jarring blast,
which can break windows, on any Nevada shot, the effect
should be anticipated for every shot and precautions
taken throughout the nearby region.
Past Experience With Blast
Light damage to structures and broken windows have resulted up to 100 miles, most of this having been in the first series on a line from the test site through Las Vegas and Henderson. Only very light damage has been reported within 100 to 200 miles. Blast has been heard but has not caused damage at greater distances, including Los Angeles, Calif., and Albuquerque, N. Mex.
Off-Site Warnings and Procedures for Blast
The Test Organization has a major safety program for anticipating where blast may strike. One item is the firing of high explosive shots prior to the nuclear test, with the blast being recorded on sensitive instruments in communities around the proving ground. If the weather remains constant these provide a good indication of where blast will strike, but if the atmosphere changes only slightly the blast may vary by miles. If strong blast is indicated for any community, the shot may be postponed.
When a possibility of light damage to any community is indicated, the community is warned to open windows and doors to equalize pressure.
The warning procedure, coming as it usually must only a few minutes before shot time and usually in predawn hours when people are asleep, is not fully effective.
The most effective precaution is for you in the nearby region to anticipate blast from every shot and to take simple measures such as opening windows and doors. Persons driving or sitting in automobiles should open the car windows. Another simple precaution is not to stay near large glass windows at shot time.
The scheduled date of each shot, and usually its scheduled hour, will be announced.
FALL-OUT FROM THE ATOMIC CLOUD
We cannot see, feel, nor hear radiation and consequently it is more difficult for the public to understand than are light and sound waves from Nevada tests. In order to help you comprehend the phenomenon of radioactive fall-out, we have appended to this booklet a discussion of natural radiation, of how we measure radiation, of how it affects people, and of the very wide difference between the levels of exposure experienced in the test site region and the levels which can cause sickness. The appendix includes a discussion of the guide which will be used by the Test Organization in its efforts to hold any public exposure to a minimum.
In our discussion here of radiation fall-out, please understand that we are not talking about high yield A-bombs or H-bombs tested elsewhere. We are not discussing radiation from enemy bombs designed to do the most damage possible. We are talking only about low-yield tests, conducted under controlled conditions at the Nevada Test Site.
The Atomic Cloud
At the instant of detonation, very powerful radiation is released in the firing area very close to the burst. This instantaneous radiation is not detectable outside the firing area, and certainly is not experienced outside the test site.
As the fireball rises and forms the atomic cloud, dirt and debris are sucked up, become radioactive, and immediately start falling. As the cloud rises, it expands, begins losing its radioactivity by decaying, and floats away, the heavier particles falling to earth.
The heaviest fall-out of radioactive particles is in the firing area. The area of quite heavy fall-out may extend several miles from ground zero, but it has not extended outside the controlled area of the Las Vegas Bombing and Gunnery Range. This is one reason why people are kept away from the test site and the bombing range.
As the cloud moves on, it becomes dispersed and usually within a few hours is no longer visible, having spread into an air mass. With each minute, its radioactivity loses strength.
Even though the cloud becomes invisible, it can be traced by the trail it leaves in the air and on the ground beneath it. This trail is of lightly-radioactive particles which fall from the cloud and can be detected and measured by highly sensitive instruments. The path of fall-out is narrow at the test site and in the nearby region, widens to hundreds of miles as it moves on, and tends eventually to be distributed uniformly over the earth's surface. It does not constitute a serious hazard to any living thing outside the test site.
Fall-Out Experience in Past Tests
As you know, the Test Organization uses various procedures to record promptly the actual fall-out in the region near the test site so that any needed action can be taken to reduce exposure and so that you may be told the level of exposure you may have experienced if you were under the cloud's path.
Fixed recording stations, mobile teams with recording instruments, low-flying aircraft which measure ground-level radiation, and planes which track the atomic air mass are all used. Thousands of reports are made.
These reports have shown that, under the controls used in Nevada, there has been no significant fall-out anywhere in the nearby region as a result of aerial bursts in which the fireball did not touch the ground. Fall-out levels have been very low--only slightly more than normal radiation which you experience day in and day out wherever you may live. (See appendix.)
The reports have shown that with low tower, surface, or underground shots--where the fireball touches the ground--there has been heavier fall-out. As the AEC has reported, no person in the nearby region has been exposed to hazardous amounts of radiation, even from this heavier fall-out, and no crops or water supplies have been made hazardous to health. Fall-out of significance to animals has been experienced only close to the site of the detonation.
If highly radioactive fall-out particles are deposited on or very near the surface of the skin, such as on clothes or hair, and stay there for an appreciable period of time, beta radiation can cause hair loss, skin discoloration and burns. Beta burns are similar to burns produced by heat, except that they appear only after one or two weeks and heal slowly and more imperfectly. Beta particles can barely penetrate the skin and produce no other damage to the body. The only beta burns recorded from Nevada tests have been on the skin of some cattle and horses grazing within a few miles of the firing area. At greater distances, there is very little likelihood of beta burns. However, simple precautionary measures may be taken to reduce exposure. These include thorough washing of exposed areas as soon as possible after fall-out has occurred, and other measures to remove the particles, such as brushing or changing clothes.
Experience has also shown that the cloud, even though its radiation decreases rapidly, contains greater than background radiation levels for some hours. The obvious answer is to prevent aircraft flight through the cloud until it has further cooled and dissipated.
Fall-out of very minute intensity can interfere temporarily with a few industrial and research enterprises in almost any part of the Nation. Interference in normal operations may occur in the uranium prospecting and mining business, in industrial and commercial processes where there are radiation controls, in the photographic industry, in low-level-radiation research, etc. Action is taken to help avoid or reduce such interference through announcements of tests.
There has been considerable public discussion in recent months concerning the effect of radiation on the body's germ cells. Changes in the units of heredity in the germ cells, which eventually may appear as new or different characteristics in offspring, occur spontaneously under normal and natural conditions in all kinds of animals and plants. Normal radiation background is one factor in this process. Higher levels of exposure to radiation can affect the process. Radiation exposure to the population in the United States from fall-out generally has been less than the exposure received from natural background sources. On the basis of experiments and observations it appears that--over a number of generations--radiation from fall-out from Nevada tests would have no greater effect on the human heredity process in the United States than would natural radiation in those parts of the Nation where normal levels are high.
Controls, Warnings and Procedures
Related to Radiation Fall-out
Every practical control and procedure is followed by the Test Organization to keep off-site fall-out at a minimum level.
Obviously, it is essential to forecast in advance where the cloud will go, where the radiation will fall off-site, and how much it will measure.
Weather is a major item. Procedures have been improved to provide a much clearer picture of what the wind directions and speeds will be following the shot. A shot will not be fired under conditions which are not stable enough to make accurate forecasting possible. As noted, this may cause many postponements while satisfactory weather is awaited.
Additional limitations have been placed on the yield of shots to be fired under various circumstances. For instance, some shots will be fired from 500-foot towers solely to decrease the amount of radioactive fall-out off-site.
Every effort will be continued to warn people away from the test site and the bombing range.
Helicopter and light aircraft sweeps of predicted fall-out areas near the test site will be made before a shot and any persons found there will be warned to leave. Like sweeps will be made following the shot. Stockmen will be advised if there are indications their stock has been exposed.
The U. S. Public Health Service, whose members have participated in past off-site monitoring, will station representatives for the duration of the series in various communities east, northeast, and north of the site--the most frequent direction of fallout. Their work will be supplemented by mobile teams from the AEC and its laboratories. Low level aircraft sweeps to check the regions of ground fallout will be continued.
If you are in an area exposed to fall-out, you will be so advised by
our radiation monitors. If there is any probability that exposure to
fall-out will approach our very conservative exposure guides, you
will be advised what to do. As has happened at St. George and Lincoln
Mine, you might be advised to stay indoors for a few hours until the
fall-out loses its strength. If you have been outdoors during the
fall-out you might be advised to bathe, wash your hair, dust your
clothes, shake off your shoes, etc. If the fall-out is across a
highway, traffic might be halted temporarily.
Your best action is not to be worried about fall-out. If you are in
fall-out area, you will be advised. If our radiation monitors advise
precautionary action, do what they say. Please bear in mind that it
is extremely unlikely that there will be fall-out above the expected
low levels on any occupied community. If you think that maybe you
have been in fall-out, or if you have other questions, get in touch
with our monitors or with the Test Organization. Your questions will
be answered.
LOCATION OF RADIATION MONITORS
The locations of the radiation monitoring stations in the test site region are shown on a map inside the back cover. The whole region has been divided into zones, each of which has one or more headquarters locations. At each headquarters there is a zone commander from the U. S. Public Health Service. He directs fellow USPHS employees in the field as they monitor fall-out beneath the atomic cloud. Field monitors can be shifted from one zone to another as required. All monitors are supervised by the Test Organization.
Should you have any questions about fall-out during the test series, you may contact the "Test Organization Monitor" for your community or zone. Public officials or the telephone operator can direct you to his location in the community. The exact location of each will be made known when the station is established in mid-February.
| Headquarters | Zone area |
| Camp Mercury | Indian Springs, Lathrop Wells, to Beatty. |
| Tonopah | North from Beatty to above Tonopah. |
| Lincoln Mine | Groom and Lincoln Mines, and Sharp's. |
| Ely | Currant to Ely and south to Lincoln County line. |
| Alamo | Sunnyside, Hiko, Crystal Springs, Alamo, south to Clark County line. |
| Pioche | Cave Valley, Atlanta, Monarch, Ursine, Pioche, east to Utah line. |
| Caliente | Panaca, Crestline, Acoma, Delamar, Caliente, Elgin, south to Clark County line. |
| Glendale | Moapa, Glendale, Mesquite, Overton. |
| Las Vegas | West to California line and Mount Charleston area; north to Dry Lake; east to Frazier's Well and Peach Springs in Arizona; south beyond Goodsprings and Nelson. |
| Washington County, Utah. | Littlesfield north to Iron County line, east beyond Springdale, south to Short Creek. |
| Iron County, Utah | Follows county lines. |
| Beaver, Utah | Millard and Beaver Counties. |
PROSPECTORS AND MINERS
Many persons in Nevada, Utah, Arizona, and nearby
California have Geiger counters these days. We can
expect many reports that "Geiger counters were going
crazy here today." Reports like this may worry
people unnecessarily. Don't let them bother you.
Geiger counters are supposed to find radiation of very low intensity. They register only as high as 20 milliroentgens per hour. (See appendix.) A Geiger counter can go completely off-scale in fall-out which is far from hazardous--although fall-out might make prospecting difficult for a few days. If the fall-out is heavy enough to be of any significance, our monitors will be in the area and will tell you what is happening.
Numerous mines in our general area produce uranium. Their ventilation
systems may draw much air--and fall-out--into the mines. Levels of
radiation from fall-out in the mines may well exceed the levels
established for normal, day-to-day operations--and still be far from
hazardous. You will appreciate that levels in a mine day after day
must be lower, first because miners are exposed to these levels every
working day, and secondly, because higher levels would throw off the
sensitive measuring instruments used in the mines. Again, if fall-out
levels are significant, our monitors will be in the area.
TESTS AND THE WEATHER
Quite by chance, some unusual weather accompanied Nevada tests during the spring of 1953. Lacking anything else to blame, some people thought the tests caused the bad weather.
You have lived next door to the test site long enough to know that weather is very important to us. We sometimes wait for days and days until the right weather comes along so that we can fire a shot. We don't create weather; we use it as it goes by.
Sometimes this means that we use a very small streak of good conditions which comes in between periods of strong winds. In such a case, strong winds will of course follow a shot.
For example, people in Las Vegas have noted during the day after an early morning test that a wind storm moved in from the northwest, seemingly from the test site. They haven't always realized that the same storm was moving toward them across California at shot time, and the Test Organization was taking advantage of the calmer period before the storm in order to control test effects. To a Tonopah resident, the sequence would have been different as he could have seen the early morning flash in the southeast, then watched the clouds move in from the northwest.
The U. S. Weather Bureau experts, and those in our Armed Forces, have reviewed all of the facts during the last year and a half and they have found no indication at all that Nevada tests change the weather anywhere in any respect.
REPORTING TEST-CAUSED DAMAGE
Since the first Nevada test series, the ABC has contracted with the
General Adjustment Bureau to receive and to investigate claims for
damages arising from test operations. An office is maintained in Las
Vegas, Nev.
The Bureau's investigative teams are supplemented by engineers, architects, veterinarians, or others in the area from which the claim originates. The investigation is thorough, in order to determine whether or not the claimed loss actually resulted from a test detonation. If found to be justified, settlement is relatively prompt.
Almost all of the claims made as a result of tests have asserted
damage from the blast effect, and a large majority of these were from
the Las Vegas area as a result of the first two test series.
GENERAL INFORMATION
The Test Organization has an Information Office at 1235 South Main Street, Las Vegas, telephone Las Vegas 6350; and an Information Office at Camp Mercury, Nev., telephone Camp Mercury 1.
APPENDIX
GUIDES TO UNDERSTANDING FALL-OUT
Radiation Is Nothing New
Very few of us can explain electricity, although we have learned to live with it and to use it. Even fewer can explain nuclear radiation. It is little understood by most of us, something we can't see, feel, or hear.
And yet, radiation is nothing new. Since the beginning of time, mankind has been bombarded by radiation from outer space and from the ground beneath him. Cosmic rays rain down from space upon each of us every second of our lives. We are also constantly exposed to radiation from uranium, radium, and other elements in the earth itself. The sum total of this radiation is known as background level and evidently man's body has learned to live with it.
Our bodies also contain radioactive materials, taken in with the food we eat and the water we drink. An AEC scientist illustrates his talks with an interesting experiment, in which the solid residue from a single sample of body fluid makes a geiger counter jump like a piece of uranium ore would.
We willingly expose ourselves to much heavier radiation when we undergo diagnostic X-rays.
So, radiation is not new to our lives. In this atomic age we are living on a more familiar basis with it. It is important that we try to understand it, accept it, and use it. It is also important that we respect its powers, so that we will be guided by knowledge and not be blinded by fear of the unknown.
How Radiation Is Measured
Radiation is undetectable by the senses. Its effects can be measured with instruments, however, just as heat is measured by a thermometer. Various sensitive devices--a geiger counter is one--have been developed for this purpose.
In order to understand the subject, we need a quantitative measure
for radiation, just as we use a quart for liquids, a volt for
electricity, or a horsepower for our automobile engines.
Various units are used by the experts in measuring radiation. The basic unit used by the Test Organization and the one we use here is a roentgen (abbreviation: "r"), named for the discoverer of X-rays.
Most of the fallout reports in the Nevada region use the term
"milliroentgen." This is simply one-thousandth of a roentgen. Ten
milliroentgen (or, "mr") are one-hundredth of a roentgen; 500 mr are
only one-half roentgen.
What Radiation Does to People
Uncontrolled radiation, like uncontrolled fire or carelessly used electricity, can be very dangerous.
It does different things to people depending upon what kind it is and upon the amount to which a person is exposed. As we have said, all of us are exposed to some natural radiation all the time and so far as anybody can tell it does no harm. But, overexposure to radiation can cause injury.
Similarly, the sun will give you a pleasant suntan, but if you are overexposed it can burn the skin and make you quite sick.
Overexposure to any kind of nuclear radiation causes injury by damaging the tiny living cells of which our bodies are composed so that they cannot do their normal work in the body. The amount of overexposure to radiation determines the amount of damage caused. We become ill from radiation only if too many cells are damaged or destroyed at one time, or are destroyed continuously in certain organs of the body over a long period of time.
Recovery of people injured by overexposure to radiation depends, as in the case of accidents, burns, or sickness, on the kind of injury and its severity. Many people who were severely injured by bomb radiation in Japan during World War II apparently made good recoveries. The important fact about radiation is that it takes quite a bit of overexposure to cause illness. Only when overexposures are very heavy is recovery problematical.
The Range From Harmless to Serious Exposures
As we have seen, all of us are exposed constantly to natural radiation, which in some cases equals eight-tenths of one roentgen a year.
The body may safely receive considerably greater doses of radiation because the effects are repaired almost as rapidly as they are produced. Over a period of many years, a human may safely receive in small doses a total amount of radiation which would cause fatal illness if administered to his whole body within a period of a few minutes.
A dose of three-tenths roentgen per week has been accepted by both national and international groups of experts as the maximum dose rate which may be delivered to the whole body for an indefinite period of years without hazard. This does not mean that three-tenths roentgen is the largest exposure which may be incurred in one week without hazard. Occasional exposures well above this figure will have no detectable bodily effect.
The lowest dose, received in a brief period, which will produce detectable effects in the body is about 25 r. and for many individuals will be 50 r. This 25 r.-50 r. range is generally considered an overexposure. Radiation sickness follows exposure somewhere in the 75 r.-100 r. range, with nausea and vomiting occasionally found as low as 100 r. Serious illness, from which people will recover with proper attention--will result at the 200 r. level. Exposure to 400 r. in a brief period will probably kill 50 percent of all persons exposed.
Workers in the atomic energy program are governed by the three-tenths roentgen per week guide. Scientists and other participants in Nevada use a guide of 3.9 r. in 13 weeks, although they quite often are exposed to higher doses--because they must go into firing areas after a detonation.
Radiation exposure of the public is, however, different from that which atomic workers voluntarily accept. It is involuntary. The numbers of people involved may become large, and there is no discrimination as to age or occupational relationship. The population includes pregnant women, young children, and many persons in the active child bearing age. Exposure which the public should be asked to accept involuntarily should be--and is--lower than that atomic workers accept voluntarily.
For this reason, the Atomic Energy Commission has established a much lower guide for future Nevada test operations. It is essentially one-fourth the guide used for atomic test workers. The standard to be used will be 3.9 r. in 1 year, instead of a like total in 13 weeks.
327321°--55
U. S. GOVERNMENT PRINTING OFFICE: 1955
Production Notes
This document was produced by scanning the original source document with a Canon CanoScan 4200F flatbed scanner. Text was recognised with ScanSoft OmniPage SE 2.0 and manually proofread and corrected. Images were scanned separately using the same scanner and postprocessed with The Gimp on Linux. Special thanks to Bill Walker who obtained this historic document and made it available for this project.
The mushroom cloud picture which appears after the table of contents is not identified in the original document. It is a photograph of the Upshot-Knothole Encore test, detonated at 08:30 local time on 8 May 1953 in Area 5 of the Nevada Test Site. This was a weapons effect test of a Mk-6D gravity bomb airdropped from a B-50 bomber at 19,000 feet and detonated at 2,423 feet above ground level, yielding 27 kt.
Web edition by John WalkerOctober 2005
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