Was
it
ficiently mild, will have a minor
effect on the underlying material.
In the second case, an appreciable
thickness of the actual surface is
removed.
How Decontamination Works
Radioactive
contamination,
four sources. It may be caused by
the fission products formed in the
explosion of an atomic bomb; by
activity mduced from neutrons in
soil and water, and by the deliberate use of radioactive materials in radiological warfare as
particularly
poison
vicious
gas attack.
form
There
in-
some of the other vessels at Bikini
There are essentially three ways
whereby the hazard associated
with radioactive contamination
may be minimized:
1. Disposing completely of the material
by
deep
ground or at sea.
burial
in
were
decontaminated
claimed much sooner.
sonably safe level,
3. Attempting to remove the contaminant, that is, to decontami-
Except where radioactive solu-
tions, such as were present after
the underwater burst at Bikini,
soak into porous materials, such
as rope, textiles, unpainted or unvarnished wood, etc., or where
neutrons have penetrated and in-
nate the material,
These three procedures were
used in radioactive contamination
suffered by ships and their equip-
the
Bikini
re-
the operating personnel. Most of
the other target vessels were destroyed, not because decontamination was not feasible, but mainly
because they were damaged in
other ways and decontamination
would not have been economical.
the
radioactivity to decay to a rea-
in
and
Two submarines thus decontaminated were used soon afterward in
the Naval Reserve with no risk to
2. Keeping it at a distance for a
sufficient time to permit the
ment
represent a category intermediate
No decontamination of the In-
also is
an
Vessels Are Reclaimed
dependence was attempted because
the vessel was in a battered condition, and it seemed unlikely that
she could be returned to service
as an aircraft carrier. However,
the possibility that plutonium that
has escaped fission may act as a
contaminant representing
ternal hazard.
of the Atomic Energy Commission,
exceeded the limit of 0.3 r per
week adopted at the installations
of
underwater
(“Baker’') test,
At Bikini, the Independence, a
small aircraft carrier,
received
duced radioactivity to some depth,
the decontamination will be large-
ly restricted to the surfaces of materials, objects and structures. An
outstanding exception would, of
course, be the radioactive contamination of water supplies for drinking purposes.
such a large radiation dosage that,
had there been any one on the
hangar deck at the time, he would
have died from external radiation,
apart from the effects of the blast.
Yet two weeks after the detonation, the dosage rate was about
The problem of decontamination
is thus, to a considerable degree,
a problem of removing sufficient
of the surface material to reduce
three r (radiation dosage units)
per day, permitting short-time access. About a year later, the aver-
age dosage rate was only 0.3 r
per day. Three years after the
original contamination, the Inde-
Is not changed in any way by
chemical reaction. All that chemistry can do is to convert the
active isotope into a soluble compound, so that it can be detached
and washed off as a solution. Certain processes of decontamination,
It was difficult at that time to
find any areas on the ship in which
the radiation dosage would have
as
explained earlier, may come from
a
Use of Detergents
It should be understood that the
activity of a particular radioisotope
involving
the use of detergents,
between the chemical and physical.
The actual process of decontaminating material and equipment
can be resolved into two stages:
first, immediate emergency measures, to permit continued operation; and second, final more thorough decontamination cperations.
Although the degree of decontamination achieved by the initial
treatment may not be large, it at
least
reduces the physiological
hazard to an extent that will make
possible, probably with changing
personnel, an operation that other-
Wise would have been impractical.
A more complete decontamination
can then be carried out, if necessary or desirable, at a later time.
The decontamination of personne! who have come into contact
with radioactive material is, of
course,
a
primary
requirement.
tive material, but could
easily decontaminated.
Normally clothing will prevent access of the material to the skin.
When
contaminated,
clothing
should be removed and disposed of,
by burial, for example, in such a
pendence was in use at the San
Francisco Naval Shipyard, where
she housed the experimental! engineering group of the Naval Ra-
chemical and physical.
In the first case, the contamination is eliminated by making use
diological Defense Laboratory.
of chemical reagents which, if suf36
not
be
Properly covered foods should
undergo little or no contamination.
The same
would
be true
for
Bomb Results Compared
Following is a comparison of the effects of atomic and conven-
tional bombs. The Tokyo attack was the huge fire raid of March 9,
1945.
Final column covers other bombings.
Hiroshima
the activity to the extent that it
is no longer a hazard. The meth-
ods of surface removal may be
divided into two main categories,
manner as to prevent the spread of
the radioactivity into uncontaminated areas, like the interiors of
buildings.
A fair degree of decontamination
of the exposed skin can be achieved
by vigorous rubbing with soap and
water, paying particular attention
to the hair, nails, skin folds and
areas surrounding body openings,
with due care to avoid abrasion.
Certain synthetic detergents, of
which many are now on the market, soapless household cleansers,
have been found to be especially
effective.
In the event of serious radioactive contamination of a large part
of a city, steps would have to be
taken to make the locality habitabie within a reasonable time. Most
important would appear to be removal or coverage of loose material that might form dust that
would be inhaled or ingested with
food.
For paved streets, flushing, perhaps with the aid of detergents,
street cleaning or vacuum sweeping, if feasible, might be the first
steps.
Concrete, stone and brick buildings, if the contaminant is on the
surface, or has not penetrated too
deeply, perhaps would have to be
wet-sandblasted
and
reroofed.
Stucco buildings might have to be
removed. The same would well
apply to roofs, which would collect
considerable amounts of radioac-
.
Atomic
Bome
Nagasaki
Tokyo
Weapon
1,667 Tons
Atomic
Bomb
93 Attacks
1,129 Tons
TNT,
TNT
Incendiary incendiary
Population per square mile ............6. 39,000
65.000
130,000
wees
Killed and Missing ......
. 70,000
. 70,000
36,000
40.000
83,000
162,000
1.850
1.830
Casualties per square mile destroyed .. . 30,000
42,000
11,800
2,000
Square miles destroyed
Injured
4.7
....
Mortality per square mile destroyed.....15.000
a=
ve
1.8
20,000
15.8
5,200
1.8
1.000