AEC Atomic Proving Ground Yucca Flat, Nevada
March 17, 1953 3
FEDERAL CIVIL DEFENSE ADMINISTRATION
GOVERNMENT DOCUMENTS TUTT LIBRARY
COLORADO COLLEGE COLORADO SPRINGS, CO 80903
PHOTOGRAPHS used for illustrations in this booklet may be obtained in 8 by 10 glossy reproductions from the Superin- tendent of Documents, Washington 25, D. C. Photographs are not available from the Federal Civil Defense Administration.
Use order blank on last page of booklet.
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l The house at Main and Elm Streets. Two typical colonial two-story center hall frame dwellings were placed at 3,500 and 7,500 feet from the bomb tower. They were identical, except for roof shingles and exterior finish. The near house had cement-asbestos shingles and a whitewashed exterior, including shutters. The far house had asphalt shingles with a single coat of white primer paint and a single coat of flat gray primer paint on shutters. {FCDA—Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
i
On March 17, 1953, more than 600 Civil Defense observers and representatives of the Nation's infor- mation media witnessed an atomic explosion at the Atornic Energy Commission's Nevada Proving Ground. Some news and radiomen called the event Operation Doorstep.” ‘The name was appropriate, since the purpose of the program was to show the people of America what might be expected if an atomic burst took place over the doorsteps of our major cities.
“Operation Doorstep” was a combined Atomic Energy Commission, Department of Defense, and Fed- eral Civil Defense Administration program, under the direction of a Joint Task Group made up of personnel of the three agencies.
The atomic explosion selected for the operation was one in which the Federal Civil Defense Administration had a limited test program. The program had three major projects: (1) Exposure of two typical American homes to atomic blast in order to determine what would happen to the homes, to test the effectiveness of simple basement shelters; (2) exposure of eight outdoor home-type shelters, in a joint project with AEG, to test the structural strength of such shelters; and (3) exposure of a variety of typical passenger cars to determine the amount of protection afforded to passengers, and the effect on the mechanical operation of the cars.
Both the observer and technical programs were in- cidental to the main purpose of the atomic detonation, which was to test an experimental nuclear device. It 1s important to note that the explosion was part of
the AEC developmental series. It would have taken place whether or not Civil Defense and the Depart- ment of Defense had participated.
“Operation Doorstep” marked the first time Civil Defense observers were allowed to witness a technical test program. The arrangement was made with the knowledge that it involved a certain amount of risk: that some observers might jump to conclusions, and that their conclusions might be wrong. However, the value to the Nation in demonstrating the effects of an atomic explosion on American homes and cars was so great it was believed the risk was warranted. Actually, These
were mostly in regard to radiation hazard. ‘The facts
very few persons reached wrong conclusions.
are contained in the preliminary report, starting on page 12.
An important angle of "Operation Doorstep" which has not rcceived sufficient stress 1s the participation of industry. Without the cooperation of a number of business associations and concerns thc program would have been far more limited in scope. For example, the test of passenger cars was made possible by the loan of vehicles by major manufacturers through the Auto- mobile Manufacturers’ Association and by public- spirited automobile dealers and dealers’ associations. Technical evaluation of the program was provided by a special committee of the Society of Automotive Engi- Gas and oil for the cars were donated by the Standard Oil Company of California.
NCES.
Mannequins for the houses and shelters were loaned by the L. A. Darling Co. and transported to and from Las Vegas by North American Van Lines. The Atlas Trucking Co. of Las Vegas not only donated hauling service from Las Vegas to the Proving Ground but provided some items of furniture. Clothing for the mannequins was obtained from the J. C. Penney Co. through the National Retail Dry Goods Association.
Even with industry cooperation, however, the tech- nical program was limited in the results which could be obtained. For example, there were no funds avail-
able for fully instrumenting the home shelters. Hence, conclusions reached were limited to the effect of blast on the shelters themselves with no evaluation of the effects of blast within the shelters.
Also we have been asked why we chose only a single type of dwelling for the test. Again, the reason was a financial one. No funds were available for additional houses of different types. FCDA has had for over a year a comprehensive program for testing a variety of typical American homes, including masonry dwell- ings of various kinds, other types of frame dwellings, and the “row house” type of structure. This test was designed by a leading frm of engineers under contract with FCDA, and was approved by the American In- stitute of Architects. In selecting the houses for “Op- eration Doorstep," FCDA chose a typical kind which could be built with the funds available. It was neces- sary to test at least two in order to determine the effect of the blast at different ranges, but since there were only two, we could not risk setting them on fire. Every possible precaution was taken to prevent this, and the houses did not burn. But because of this fact, we are not able to state how much fire hazard there would be in a house fully equipped with utilities.
FCDA expects to continue its test program in the future. Only by a continuing program of this kind can we provide information needed by the public and State and local Civil Defense organizations.
Unknown Factors
In evaluating the results of any test, two important things must be kept in mind. We make tests with an atomic weapon of known size and power, and our test items are placed at known distances from ground zero. But in translating the test results into what would hap- pen in case of atomic attack on our cities, we do not know the size and power of the enemy weapons which might be used against us. We do not know where those bombs would fall in our cities—i. e., what their ground zeros would be.
What Civil Defense and the public needs are general conclusions which will apply in the majority of cases under the principle of the “calculated risk” which 1s basic to all realistic Civil Defense planning.
Thus, when Civil Defense recommends a home shel- ter design, we are saying in effect: “Since no one knows where ground zero would be, the chances are that you would not be within the total destruction area of an atomic burst over your city. ‘Therefore, this home shelter should give you good protection from blast, heat, and radiation. It probably would save the lives of yourself and your family in areas where persons with less protection might be badly hurt or killed.”
With these things in mind, FCDA learned on March 17th that the shelters which were tested can withstand We learned that with such shelters, the chances for survival under atomic attack
blast, heat, and radiation.
are greatly increased. The reasons for this conclusion are given in detail in the report which follows.
FCDA owes a particular debt of gratitude to the Atomic Energy Commission and its Test Organization for the excellent cooperation and assistance which have made the Civil Defense test programs possible. The observer program of “Operation Doorstep” was made possible by the combined efforts of the Atomic Energy Commission, the AEC Test organization, the Department of Defense, the Las Vegas-Clark County Civil Defense organization, and the FCDA Atomic Test Operations Staff headed by Harold L. Goodwin.
It now remains for each of us to apply the lessons learned in “Operation Doorstep” toward greater fam- ily Civil Defense preparedness
WW
VAL PETERSON Administrator Federal Civil Defense Administration
X-19
This mannequin can only stay in the position in which he was placed, staring through the window at coming disaster. A real occupant of this house could
prepare—and survive. (FCDA—Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.]
OPERATION DOORSTEP
a Preliminary Report by the
Federal Civil Defense Administration
On March 17, 1953, the Federal Civil Defense Administration, in cooperation with the Atomic Energy Commission, conducted a demonstration and limited technical tests of typical American dwellings, home-type shelters, passenger vehicles, and devices for locating the air zero of an atomic burst. The tests were conducted at the AEC Nevada Proving Ground as a part of the AEC developmental series. The burst was from a 300-foot bomb tower and had a yield equivalent to about 15,000 tons of TNT. (For con- venience, the term bomb tower is used, although the detonation was of an experimental test device.)
There has been much comment that this 15,000-ton burst was “undersized” ... “a baby bomb." Such comment is unrealistic. The house which was almost entirely destroyed by this 15,000-ton burst at 3,500 feet, would have suffered the same blast damage from a 20,000-ton Hiroshima-size burst had it been located only 350 feet farther from ground zero.
OBJECTIVES
FCDA test program objectives were as follows:
1. Two identical frame houses, two-story, with base- ment, were erected in Yucca Flat to determine the general effect of atomic blast on certain typical Ameri- can houses, and to determine the effectiveness of in- expensive wooden basement shelters.
A detailed engineering report on the behavior of each of the test houses will be published later in the year. The present observations are preliminary and informal.
Because of lack of funds, the houses contained no utilities such as electric wiring, plumbing, heating, or gas piping. The interiors were plastered but not painted. The wood trim, doors, and floors were also left unfinished.
The test was necessarily designed to indicate the structural effects of blast only. Precautions were taken to prevent the houses from burning, since fire would have made difficult, or prevented, post-shot
evaluation of structural failure. To help in the pre- vention of fire, both houses were given white exterior finishes, and windows facing the explosion were equipped with aluminum finish metal venetian blinds. The purpose was to reflect as much thermal energy as possible. The house nearer the tower was roofed with light gray cement-asbestos shingles. The house at the farther range had light gray asphalt shingles.
The nearer house was 3,500 feet from the tower at a range calculated to give a pressure of about seven pounds per square inch above normal atmospheric pressure. The farther house was at 7,500 feet, where the overpressure was expected to be about two pounds per square inch.
The houses were sparsely furnished with Govern- ment surplus furniture. Store mannequins, provided at no cost to the Government by the L. A. Darling Company of Bronson, Michigan, were placed in the rooms and the basement shelters.
Each basement included one lean-to type shelter and one corner room shelter. The lean-to, simplest and least expensive design, used about $40 worth of materials. The corner room shelter used about $95 worth,
The lean-to was built of 2- by 6-inch joists, spaced 5 inches center to center, covered with 1-inch sheath- ing, sloping from the basement floor to the foundation wall, facing the dtrection of the blast. The corner room was a 6-foot cube, with 2- by 6-inch wall and roof studs, spaced 8 inches center to center, covered with r-inch sheathing.
Instrumentation was by film badges, to determine the penetration of gamma radiation into the base- ments. About roo badges were used in each base- ment. ‘They were placed at regular intervals in order Some badges were in the shelters. The Atomic Energy Commission provided automatic motion picture pho-
to give measurements at a number of points.
tography in order to provide sequence-collapse photo- graphs.
LSM-16
The "'lean-to" shelter. Can be built for about $40 worth of material by most home handymen. It offers good shelter, but because of pos- sible fire hazards a basement- exit type is better. (FCDA— Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
CSM-15
A "corner room" box-fype basement shelter. Each base- ment of the test dwellings was equipped with one of these. Families in both houses would have survived the atomic explosion in the shelters, although later fire could have placed them in new danger. [FCDA—Oper- ation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.]
CSA-1
A mannequin family waits for the atomic burst in a basement shelter 7,500 feet from ground zero. The shelter, a box made of heavy timbers,
is known as a "corner room." [FCDA-——Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.]
SS
LSM-16
The "lean-to" shelter. Can be built for about $40 worth of material by most home handymen. It offers good shelter, but because of pos- sible fire hazards a basement- exit type is better. (FCDA— Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
CSM-15
A "corner room" box-type basement shelter. Each base- ment of the test dwellings was equipped with one of these. Families in both houses would have survived the atomic explosion in the shelters, although later fire could have placed them in new danger. [FCDA-—Oper- ation Doorstep—Yucca Fiat, Nev., Mar. 17, 1953.)
CSA-1
A mannequin family waits for the atomic burst in a basement shelter 7,500 feet from ground zero. The shelter, a box made of heavy timbers, is known as a "corner room."
(FCDA—Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
SM-17
A basement-exit type shelter, of reinforced concrefe. Can also be made of cinder or cement block with reinforced slab roof. Best, because it would allow occupants ło get out in case of fire, or damaged utilities. This type showed no damage only 1,250 feet from ground zero. (FCDA — Operation Doorstep— Yucca Flat, Nev., Mar. 17, 1953.)
SM-18 Covered-trench type shelter, of © cinder block with concrete slab roof. One of these showed no signs of damage only 1,450 feet from ground zero. (FCDA— Operation Doorstep — Yucca Flat, Nev., Mar. 17, 1953.1
Both houses were equipped with wooden shutters. The exterior of the house nearer the tower was white- washed, including doors, windows, and shutters. T'he farther house was given a single coat of flat white paint, except for the shutters which were painted gray. During the tour by press and Civil Defense repre- sentatives two days before the shot, some of the shut- ters were closed by cameramen in order to give better interior lighting conditions. Some visitors left with the impression that the test was to be conducted with certain shutters closed. This was not the case. All shutters were opened before the shot.
2. Eight underground backyard type shelters were tested to determine their resistance to blast at various pressures, and to check the amount of protection afforded occupants from gamma radiation.
With the exception of the basement corner room, these shelters are based on original designs prepared by the Lehigh University Institute of Research under contract with FCDA.
The shelter, nearest the blast was a basement-exit type, of reinforced concrete, with open entrance. It was located 1,250 feet from the bomb tower, at an expected overpressure of 45 pounds per square inch.
Next in line, at 1,450 feet, 30 pounds per square inch overpressure, was a covered-trench type shelter made of cinder block with a reinforced-concrete roof slab and open entrance.
A cluster of five shelters was located at 1,800 feet, at an expected overpressure of 20 pounds per square inch. ‘These shelters were as follows:
(a) Covered-trench type, cinder block with con- crete roof slab, open entrance.
(5) Covered-trench type, cinder block with wooden roof, open entrance.
(c) Covered-trench type, cinder block with con- crete roof slab, closed entrance.
(d) Basement-exit type, cinder block with concrete roof slab, open entrance.
(e) Five-foot inside diameter concrete pipe, closed entrance.
An eighth shelter, covered-trench type, cinder block with concrete roof, open entrance, was located at 3,500 feet next to the first house. The materials for this shelter cost about $180.
Shelters (a), (b), and (d) were complete with open stair entrances. Shelters (c) and (e) were closed with solid covers of 2 by 4 timbers, on edge, and were reached through access shafts. The shafts were for project personnel access only; they were not normal entrances, and were not for test purposes. The shelter at 1,450 feet had 4 feet 6 inches of earth cover. All other shelters had three feet of earth cover.
257423 0—53——2
In the covered-trench type of underground shelter, the cinder-block walls were 8 inches thick, of hollow blocks filled with concrete which was reinforced with Va-Inch steel rods set 16 inches apart. The roof slab was 4¥g inches thick, reinforced with %-inch rods 4 inches apart, spanning 4 feet between the walls. In the underground basement-exit, the cinder-block walls and roof slab were the same construction as the covered trenches, but the span between walls was 3 feet. In the basement-exit nearer to the burst, the construction was all reinforced concrete. The walls and roof were 6 inches thick, reinforced with 34-inch rods 4 inches apart, roof span between walls 3 feet. In one of the covered trenches the roof was wood: 2- by 6-inch rafters, 4 inches center to center, covered with r-inch sheathing, span 4 feet. The sewer pipe, 5 feet inside diameter, had a thickness of 4V5 inches.
The shelter designs will be available to the public in the near future through local civil defense offices in an official FCDA manual for those who wish to build shelters in their own basements or backyards.
Film badges for the detection of gamma radiation and fusion strips for the detection of excessive tem- perature increases were placed in the shelters. Lack of funds prevented instrumentation of the shelter in- teriors for air pressure, mannequin motion, and wall
and roof displacement.
Store mannequins were placed in shelters at each range. The mannequins at 1,250, 1,450, and 1,800 feet were weighted with sand, the weight being con- fined to their legs. An exception was a mannequin simulating a small boy in the shelter at 1,250 feet. This one was not weighted, since its mass approxi- mated that of a child of the same age.
3. A variety of typical passenger cars was tested. These ranged in age from 1936 to 1953 models. All major makes were represented. In addition, three mail trucks belonging to the Post Office Department were exposed at three ranges.
The vehicles test was not completed until early in May. Evaluation of results will be made in a separate report. However, because of the number of com- munications received by FCDA and AEC, it should again be emphasized that cars tested by FCDA were not the property of the U.S. Government. They were donated for the test by the dealers and manufacturers of America. FCDA has returned the test cars to their owners.
4. Four types of air zero locaters were given an initial test. These are devices for locating the air zero of an atomic burst by means of thermal radiation. ‘The immediate location of the burst is of primary im- portance to those who plan to relieve the stricken area. The project will not be completed until the end of the current test series.
SM-17
A basement-exit type shelter, of reinforced concrete. Can also be made of cinder or cement block with reinforced slab roof. Best, because it would allow occupants to get out in case of fire, or damaged utilities. This type showed no damage only 1,250 feet from ground zero. (FCDA — Operation Doorstep— Yucca Flat, Nev., Mar. 17, 1953.)
SM-18
Covered-trench type shelter, of cinder block with concrete slab roof. One of these showed no signs of damage only 1,450 feet from ground zero. {FCDA—
Operation Doorstep — Yucca Flat, Nev., Mar. 17, 1953.1
P
Both houses were equipped with wooden shutters. The exterior of the house nearer the tower was white- washed, including doors, windows, and shutters. The farther house was given a single coat of flat white paint, except for the shutters which were painted gray. During the tour by press and Civil Defense repre- sentatives two days before the shot, some of the shut- ters were closed by cameramen in order to give better interior lighting conditions. Some visitors left with the impression that the test was to be conducted with certain shutters closed. This was not the case. All shutters were opened before the shot.
2. Eight underground backyard type shelters were tested to determine their resistance to blast at various pressures, and to check the amount of protection afforded occupants from gamma radiation.
With the exception of the basement corner room, these shelters are based on original designs prepared by the Lehigh University Institute of Research under contract with FCDA.
The shelter, nearest the blast was a basement-exit type, of reinforced concrete, with open entrance. It was located 1,250 feet from the bomb tower, at an expected overpressure of 45 pounds per square inch.
Next in line, at 1,450 feet, 30 pounds per square inch overpressure, was a covered-trench type shelter made of cinder block with a reinforced-concrete roof slab and open entrance.
A cluster of five shelters was located at 1,800 feet, at an expected overpressure of 20 pounds per square inch. These shelters were as follows:
(a) Covered-trench type, cinder block with con- crete roof slab, open entrance.
(b) Covered-trench type, cinder block with wooden roof, open entrance.
(c) Covered-trench type, cinder block with con- crete roof slab, closed entrance.
(d) Basement-exit type, cinder block with concrete roof slab, open entrance.
(e) Five-foot inside diameter concrete pipe, closed entrance.
An eighth shelter, covered-trench type, cinder block with concrete roof, open entrance, was located at 3,500 feet next to the first house. The materials for this shelter cost about $180.
Shelters (a), (b), and (d) were complete with open stair entrances. Shelters (c) and (e) were closed with solid covers of 2 by 4 timbers, on edge, and were reached through access shafts. The shafts were for project personnel access only; they were not normal entrances, and were not for test purposes. The shelter at 1,450 feet had 4 feet 6 inches of earth cover. All other shelters had three feet of earth cover.
257423 0—53——2
In the covered-trench type of underground shelter, the cinder-block walls were 8 inches thick, of hollow blocks filled with concrete which was reinforced with L5 -inch steel rods set 16 inches apart. The roof slab was 4V» inches thick, reinforced with 34-inch rods 4 inches apart, spanning 4 feet between the walls. In the underground basement-exit, the cinder-block walls and roof slab were the same construction as the covered trenches, but the span between walls was 3 feet. In the basement-exit nearer to the burst, the construction was all reinforced concrete. The walls and roof were 6 inches thick, reinforced with -inch rods 4 inches apart, roof span between walls 3 feet. In one of the covered trenches the roof was wood: 2- by 6-inch rafters, 4 inches center to center, covered with 1-inch sheathing, span 4 feet. The sewer pipe, 5 feet inside diameter, had a thickness of 4% inches.
The shelter designs will be available to the public in the near future through local civil defense offices in an official FCDA manual for those who wish to build shelters in their own basements or backyards.
Film badges for the detection of gamma radiation and fusion strips for the detection of excessive tem- perature increases were placed in the shelters. Lack of funds prevented instrumentation of the shelter in- teriors for air pressure, mannequin motion, and wall
and roof displacement.
Store mannequins were placed in shelters at each range. The mannequins at 1,250, 1,450, and 1,800 feet were weighted with sand, the weight being con- fined to their legs. An exception was a mannequin simulating a small boy in the shelter at 1,250 feet. This one was not weighted, since its mass approxi- mated that of a child of the same age.
3. A variety of typical passenger cars was tested. These ranged in age from 1936 to 1953 models, All major makes were represented. In addition, three mail trucks belonging to the Post Office Department were exposed at three ranges.
The vehicles test was not completed until early in May. Evaluation of results will be made in a separate report. However, because of the number of com- munications received by FCDA and AEG, it should again be emphasized that cars tested by FCDA were not the property of the U.S. Government. They were donated for the test by the dealers and manufacturers of America. FCDA has returned the test cars to their owners.
4. Four types of air zero locaters were given an initial test. These are devices for locating the air zero of an atomic burst by means of thermal radiation. The immediate location of the burst is of primary im- portance to those who plan to relieve the stricken area. The project will not be completed until the end of the current test series.
imu.
S Ue Somer =
X-13
Car 50, behind House No. | at 3,500 feet. awaited the blast.
17, 1953.1
In this car a mannequin driver (FCDA—Operation Doorstep—Yucca Flat, Nev., Mar.
! BWU-1 A 15 KT atom bomb explodes in "Operation Doorstep.” [FCDA—Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
RESULTS
BLAST EFFECT ON HOUSES
FCDA engineers expected that the house at 3,500 feet would collapse and that the house at 7,500 feet would sustain some damage. By placing a house in a location where collapse was expected, it would be possible to test the protective value of the basement shelters. Since no dwellings of this type had ever been exposed to atomic blast until the March 17th shot, the degree of damage to the far house could not be accu- rately predicted.
As shown dramatically by published sequence pho- tos, the near house collapsed as expected. The first story was completely demolished and the second story,
which was very badly damaged, dropped down on the first floor debris. The roof was blown into several sections.
The rear section of the roof was blown into the backyard. The upper half of the front part of the roof was turned upside down in the front yard while the lower part landed at some distance from the house to the rear. The gable end walls were blown apart and outward. The chimney was broken into several large masses and landed outward from the house at about a 45° angle to the rear.
BWU-2
At the instant of explosion a blinding flash lights up House No. 1. {FCDA — Operation Doorstep — Yucca Flat, Nev., Mar. 17, 1953.)
BWU-3
Solid black smoke colored by charred wood, curling upward. There is no flame. (FCDA—Operation Door- step—Yucca Flat, Nev., Mar. 17, 1953.1
BWU-4
The smoke from the char is almost gone before the blast wave hits. (FCDA-—Opera- tion Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
BWU-5 The blast wave strikes. (FCDA
—Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.1]
BWU-6
The front begins to disinte- grate and the roof is being ripped back. The air is filled with debris. [(FCDA—Opera- tion Doorstep—Yucca Fiat, Nev., Mar. 17, 1953.]
BWU-7 Down it goes . . . in 23/3 {FCDA—Operation Doorstep — Yucca Flat, Nev., Mar. 17, 1953.)
seconds!
The basement walls suffered some damage above grade, mostly in the rear. The front basement wall was pushed in slightly, but was not cracked except near the ends. ‘The first floor wood girders were pushed back and the supporting pipe columns inclined to the rear.
After the blast, entry to the basement was made by test personnel at the front of the house through the gap between the first-floor framing and the basement wall. Although the living room and kitchen areas had broken through into the basement, the rest of the area was comparatively clear. Neither basement shelter suffered any damage worth noting. Mannequins in the shelters were not moved or harmed. On the other hand, mannequins in the first-floor rooms were badly damaged and some were so trapped by debris that they could not be readily removed.
The house was go~95 percent destroyed. No por- tion of the house except parts of the basement walls could have been used again.
The dwelling at 7,500 feet remained standing, al- though it was badly damaged. The most apparent damage to this building was the destruction of doors
and windows, including sash and frames. The front
door disintegrated into its component parts and the doorknobs and lockset were found halfway up the stairs to the second floor. The dining room-kitchen door also disintegrated and one part of it was hurled into the plaster of the rear kitchen wall.
Principal damage to the first-floor system consisted of broken joists. Most breakage originated at knots in the lower edges of the timbers. Some studs were cracked in the front of the house. The floor Joists were 2 by 8 inches, spaced 16 inches between centers, with a span of 12 feet. The front wall studs were 2 by 4 inches spaced 16 inches apart.
The second floor system suffered no apparent dam- age, but plaster and windows of the second story were severely damaged. Damage to the roof consisted mainly of broken rafters in the front section. All rafters except one were broken on the front side. The roof was sprung slightly at the ridge. No rafters were broken on back side of the roof. The rafters were 2 by 6 inches, spaced 16 inches between centers, with a span about 14 feet from front wall to ridge.
15
16
1 HA-T1
House No. 1, from the camera tower from which the dramatic collapse pic- fures were taken. The Post Office truck to the left, although it lost all windows and suffered body damage, was driven away later, as was the car in the rear of the house. Entry to the basement was made through the corner at lower center. {FCDA—Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
CAR-14
Car 50, after the blast. Top severely dished, some windows broken, hood blown open. The mannequin driver had a crushed head. But the car was
driven away a short time later. (FCDA—Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
17
1 HA-9
The front of the house 3,500 feet from ground zero after the blast. Black- ened boards were charred by the heat flash, but the char averaged little more than 1/16th of an inch. The house did not catch fire. Seen here is the second floor; the first floor was totally destroyed. The doorstep marks the position of the lean-to shelter in the basement. {FCDA—Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
The basement showed no damage except to win- dows and the basement door and frame. The shelters were intact. Mannequins in the shelters were undis- turbed.
Mannequins in dining and living rooms were thrown about considerably. Only one of the mannequins in the group appeared undisturbed. Heads of the man- nequins were generally pockmarked and clothing was cut by flying glass. Some mannequins had evidence of more serious injury, such as holes the size of a quar- ter. Tiny pieces of glass remained in the plaster of some mannequin heads.
With windows and door openings covered and minor shoring in the basement, the house would have been habitable under emergency conditions. Restoration of the house to its original condition would have been costly.
BLAST EFFECT ON SHELTERS
'The basement-exit type reinforced-concrete shelter at 1,250 feet showed no damage whatever. The weighted dummy in this shelter was broken in half, but the child mannequin, although thrown to the floor, was not marked or damaged in any way.
The covered-trench shelter at 1,450 feet was un- damaged. The mannequin inside was not disturbed.
The covered-trench shelter with concrete roof at 1,800 feet was undamaged. The mannequin inside was not disturbed.
The covered-trench shelter with wooden roof showed a break in one wall, but the exact cause is at present undetermined. Therefore, this shelter should be omitted from the evaluation of results.
The remaining shelters at 1,800 feet and the shelter at 3,500 feet showed no damage of any kind, even though two had closed entrances. The purpose of the closed entrances was to keep out the blast in order to test the shelter roof under external overpressure only. In the open shelters the outside pressure on the roof was balanced by the inside pressure as the blast struck. The two closed shelters, at 1,800 feet, were exposed to an outside overpressure of 20 pounds per square inch.
RESCUE OPERATIONS
The need for trained Civil Defense rescue teams and rescue operations following an atomic bombing was shown by the entrapment of the mannequins in the house 3,500 feet from the bomb-tower. The manne- quins, which had been placed in a family group in the living room of the house, were partially or com- pletely buried under debris.
While it appears obvious that, had they been human beings, they would have been severely injured or killed, it would nevertheless have been necessary to effect rescue. This could best have been accomplished by working in the open from the top, removing consid- erable debris and lifting the mannequins out.
The mannequins which were seated around the table in the dining room of the house were entrapped in such a manner that rescue would have beeri much more difficult. Large sections of the second story of the house completely covered the area in which they were entrapped. To secure access to the mannequins from above, it would have been necessary to remove these large sections of the house or to dismantle them piece by piece. A better method might have been to rescue this group from the basement area since the first floor system had been broken through and there was an opening into the basement through which some of the mannequins were visible, although they were en- trapped in the debris. To effect rescue from the base- ment it would have been necessary for the rescue team to provide some temporary shoring around the opening through the floor and under the girders of the first floor system to prevent collapse of the wreckage upon them- selves. By tearing apart the wreckage of the first floor system, it would have been possible to obtain access to all of the mannequins.
THERMAL EFFECT
The visible effects on the house 3,500 feet from the burst were recorded by an automatic camera installed by AEC. The film has been run in slow motion and examined frame by frame.
The light and heat radiated by the burst arrived at the same instant. The glare immediately lighted the house for the camera. The thermal radiation striking into the front of the house required a fraction of a second to show any effect.
Then, a solid black “smoke,” colored by charred wood, burst out of the cross-slats of the wooden shut- ters which were folded back against the walls. Else- where the heavy boards of the front walls still showed no effect. At a later instant, the whole front of the house began to ooze the “smoke.” A solid black layer rolled up the front of the house and hid it momentar- ily. The adjacent air was otherwise evidently at rest. The blast was still on the way from the burst.
Before the blast arrived, the smoke ceased. Evi- dently the thermal radiation dropped off before the delivery of heat was sufficient to start a self-sustaining flame.
19
20
1 HA-10
The unprepared mannequin family caught by the atomic blast in the living room of the house at 3,500 feet. No pictures could be taken of the dining room group in this house; they were completely buried in debris. Survivors
would have needed the services of a CD rescue team. By contrast, manne- quins in the basement shelters of this house were undamaged. {FCDA— Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
^
LSA-2
3,500 feet from ground zero. The house overhead is totally destroyed, some of it has fallen into the basement, but the mannequin in the lean-to shelter is undisturbed. The photo was taken from ground level, looking into the
basement through the gap between the basement wall and the broken floor timbers. (FCDA-—Operation Doorstep-—Yucca Flat, Nev., Mar. 17, 1953.)
21
22
BA-3
In an upper bedroom of the house 7,500 feet from ground zero broken window frames, damaged plaster and overturned furniture mark the trail of the atomic blast. The mannequin on the bed was undisturbed, except for loss
of bed clothes. {FCDA—Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
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—MÀà eet —rt dom 2t n mmm Sabe Doct ERE tacere
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2 HA-12 House No. 2, af 7,500 feet, after the blast. Although only damage te win- dows can be seen in this photo, interior damage was extensive. [FCDA— Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
DRB-4
A silent dinner party in progress in the dining room of the house at 7,500 feet from ground zero—soon to be abruptly ended by the atomic blast. (FCDA—Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
24
DRA-5
Dinner's end. This party group was caught unprepared in the dining room of the house at 7,500 feet. {FCDA—Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
25
L4
ES
| LRB-6
| Family scene, mannequin style, before the blast. This group is in the living room of the house 7,500 feet from ground zero. (FCDA—Operation Door- step—Yucca Flat, Nev., Mar. 17, 1953.]
26
LRA-7
The family group in the living room of the 7,500-foot house after the blast. While some mannequins look comparatively undisturbed all showed marks from flying glass. The upright male mannequin had plaster chipped from both eyes. The little girl was severely marked around the forehead. (FCDA—Operation Doorstep—Yucca Flat, Nev., Mar. 17, 1953.)
27
The blast did not blow any fire out. Before it arrived, the thermal effects had plainly run tbeir course. For a split second, the house clearly presented a charred front, without either flame or smoke. Then the blast wave arrived.
The house did not burn!
A great deal of misunderstanding has arisen con- cerning the use of venetian blinds. The blinds placed in windows facing the blast in both houses were ordi- nary commercial metal type, aluminum finish with plastic tapes. They were not expected to withstand the blast. Their sole purpose was to keep thermal energy from entering the house through the windows and possibly setting fire to the furniture. They per- formed as expected. There were no signs of thermal effect inside either house. A few seconds after the thermal energy had spent itself against the blinds, the blast struck the windows, taking out glass, sashes and frames, and all venetian blinds. The venetian blinds had been expected to blow apart under blast pressure. Instead of being blown into separate slats, they were rolled up in tangled masses. Of course, anyone ex- posed in living or dining rooms might have been struck by the venetian blinds, but they would also have been struck by glass and other missiles.
RADIATION
When any atomic device is detonated, there are two radiation phases. At the instant of detonation and for slightly over a minute thereafter, radiation is emitted. "This is termed "initial radiation. It consists of both radiant energy and components of atoms.
Meanwhile, the burst rises, carrying with it parti- cles of radioactive matter. Some of these are products resulting from the fission, others are particles of un- fissioned material. Still others are particles of the tower on which the device was detonated, or, in case of an air burst, of the casing and mechanism. In a low burst, some material from the ground is made radioactive by neutron bombardment and sucked up into the column. As the prevailing wind moves the bomb cloud, the particles drift to the ground. These particles constitute “fall-out” and are responsible for most of the "residual" radioactivity. The radiations they emit are generally of the same nature as those thrown off by the burst itself during the initial phase.
Since the detonation of March 17 was from a 300- foot steel tower, considerable fall-out was expected. What was not expected, however, was that an unfavor- able wind would dump the fall-out precisely on the line of the FCDA test structures and cars.
28
The particles of radioactive material fell to earth in a relatively narrow path with the FCDA base line at its center. Elsewhere in the area the level of radio- activity was not excessive, and personnel of various classified projects conducted during the shot were able to move in and out of the area in a manner normal to such tests.
Along the FCDA line, however, levels were high in comparison with the maximum levels permitted by the Test Organization.
The AEC Test Organization and the Atomic Energy program have established general rules on the maxi- mum amount of radiation to which a person can be exposed. ‘These levels are designed to protect per- sonnel who work continually with radiation and are known as industrial safety levels.
FCDA is in complete agreement with the AEC levels, as they apply to normal activity. However, in case of disaster the situation is altered and Civil De- fense teams may accept much higher exposures if necessary, in order to perform rescue, first aid, and other Civil Defense duties.
A short time after the shot, a team of five men went into the FCDA area to inspect the residence at 7,500 feet. They remained in the area long enough to determine whether or not the dwelling would be struc- Their radiation dosage was only one-third of the total dosage allowed
turally safe for observers to inspect.
by the Test Organization. In other words, had rescue or other Civil Defense work been necessary, this team could have remained three times as long without even exceeding permissible industrial levels.
In an emergency, teams could have worked in the area for several hours without consideration of replac- ing them with fresh teams.
In addition to the technical program personnel who entered the area on the first day when levels were highest, personnel of the radiological safety group also entered in order to make surveys of the contamination levels.
During the first day, winds shifted the contaminated material and kept levels high enough so that the Test Organization could not allow observers to inspect the FCDA structures. The time involved in moving over 600 persons through the contaminated area might have resulted in some persons exceeding the allowable While this is sometimes warranted in the case of technical personnel, it is not warranted in the case of visitors.
However, the observers were taken down a road paralleling the FCDA test line in order to observe the houses from a closer range. The observers rode and walked to the 10-milliroentgen-per-hour line.
dosages.
Beyond the ro-milliroentgen-per-hour hne, according to Test Organization rules, protective clothing must be worn. This protective clothing is not intended to prevent exposure of the wearer to radiation. It does prevent him from getting his own clothes contami- nated by radioactive dust. It would not be convenient either to program personnel or the Test Organization to send personal clothing to the radiological safety laundry.
Most observers who went to the 1o-milliroentgen- per-hour line did not notice that they were actually closer to ground zero than the farther FCDA residence. Had there been anything to inspect, the tour could have been taken almost anywhere in the area except to FCDA structures line and the ground zero area itself,
Although technical teams went into the FCDA area for limited periods on the first day, the FCDA team scheduled to recover film badges was not able to operate on schedule because the amount of time involved in recevery would have required exposure of the team beyond maximum allowable dosage. This was unfortunate, since gamma radiation badges pro- vided almost the sole instrumentation for the Civil Defense test items. The badges were intended to measure initial gamma radiation from the burst, since this radiation always occurs and high readings from fall-out were not expected. The badges did, of course, measure initial gamma except where they were fully protected. Then fall-out dropped into the area and some contaminated dust blew into shelters and resi- dences. The badges also recorded gamma radiation from the fall-out. By the time badges could be recov- ered, they had also been exposed to about 30 hours of residual activity.
To aid in interpretation, the FCDA recovery team measured the intensity of radiation in a number of places, both inside and outside the structures. Read- ings by survey meter inside the basements of the dwellings and inside the outdoor shelters averaged one-tenth of those outside.
Results of the portion of the test concerned with radiation are as follows:
1. While the contamination of the FCDA area was inconvenient for both observers and program person- nel, it would not have seriously hampered Civil Defense disaster operations in a real emergency.
2. Persons in the first- and second-floor rooms of the near house would have received a severe dose of initial radiation from the burst. This dose would have been sufficient to cause serious radiation sickness with the probability of death in some cases. Persons
in the basement shelters of the near house would have been almost completely protected from the initial radiation. However, had persons taking shelter in the basement been forced to remain for the 30-hour period before the badges were recovered, an unlikely contingency, some cases of radiation sickness from exposure to residual radiation might have resulted with recovery expected in most cases.
3. Persons in the first- and second-floor rooms of the house at 7,500 feet would not have received enough initial radiation to be of consequence. Persons in the basement should have received no initial dosage, and even 30 hours’ exposure to residual activity should not have seriously endangered them.
4. Persons in any of the outdoor shelters would have received good protection from initial radiation, but some probably would have become casualties from residual radiation over a 30-hour period.
It is important to remember that the protection from initial radiation afforded by both outdoor and basement shelters is provided by the thickness of earth cover and other dense materials which the radiation must penetrate. The greater the thickness, the greater the protection.
Since the March 17th burst was from a 300-foot tower, radiation along the slant line from the burst to the occupant of a shelter would have to go through a much greater thickness of earth cover than would have been the case in a high air burst. ‘Therefore, in select- ing a shelter and a location for it, the greatest possible thickness of earth cover or other dense material is desirable between the occupants and the probable direction of a burst.
CONCLUSIONS
Persons on the first or second floors of the house at 3,500 feet would have been critically mjured by glass and debris, if not killed. Their exposure to radiation would probably have produced illness or fatalities.
On the other hand, persons in the basement shelters of this house would have been protected from debris and harmful initial radiation and, although the shel- ters were not instrumented for measuring increases in air pressure, it is believed that pressures would not have been significant insofar as their harmful effect upon the body is concerned.
29
Persons on the first and second floors of the house at 7,500 feet would have sustained injuries ranging from minor to critical, with most injuries caused by flying glass and other objects. ‘There was some evi- dence of direct blast damage to the mannequins, but radiation would not have produced casualties.
In both cases ıt must be remembered that there was no fire. Since the houses were not equipped with utilities and were protected from direct ignition by the thermal energy of the explosion, no conclusions should be drawn about fire which might have resulted under normal conditions.
In all probability, persons in the basement shelters of the house at 7,500 feet would have escaped un- harmed even in case of fire, especially had they been provided with a proper type of fire extinguisher.
The question of immediate escape from the base- ment of the house at 3,500 feet is much more doubtful. While the normal basement exit was blocked by debris, there was a sufficient gap between the first-floor fram- ing and the basement wall to allow for escape; FCDA technical personnel went in and out by this route after the shot. But in case of fire the gap might or might not have been blocked by flames. Otherwise, escape probably could have been made by persons in normal health, even though getting out through the gap re- quired some exertion. Aged or ill people would have required assistance.
RECOMMENDATIONS
BASEMENT SHELTERS
(a) Basement shelters of the types tested should
provide reasonable safety for occupants from blast and
falling debris when such shelters are in frame dwell- ings. No final conclusions should be drawn con-
cerning the safety provided by such shelters ir dwellings of brick or block, since the way in whic! such houses react to blast is quite different. It 1 believed, however, that the basement shelters are ade quate for a 2-story house of any normal type of con struction. When properly placed in an undergrounc basement, good shielding from radiation is provided
(b) Because of the hazard of fire, whether fron initial thermal energy or damage to live utilities, ar underground shelter which is open to the basemen and has another opening outside the house, althougl more expensive, is to be preferred where practicable Such a shelter is the underground basement-exit type tested separately as part of the outdoor shelte program.
BACKYARD UNDERGROUND SHELTERS
Backyard underground shelters of the type testec should provide greater protection than the base ment lean-to and the basement-corner room shelter: because they are of a stronger construction. Also, be- cause of their location away from the house, there 1 less likelihood that the shelter exits would be blocked an important consideration in case of fire.
All shelter designs tested are believed to be adequate to withstand blast overpressures of at least 20 pound per square inch. Reinforced-concrete basement-exi shelters of the type tested should withstand overpres sures up to 45 pounds per square inch.
Since it was not possible to instrument for a1 pressures inside the shelters, no conclusions shoulc be drawn as to the safety of occupants in the high pressure regions closer to the burst. However, it i believed that persons in the shelter at 3,500 feet woul have been unharmed.
There was no evidence that temperatures increasec significantly inside any shelters.
The shelters would provide good protection fron initial radiation.
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