148 lines
10 KiB
Plaintext
148 lines
10 KiB
Plaintext
|
|
|||
|
|
Fallout Fundamentals
|
|||
|
|
Fallout consists of dust particles that have been coated with radioactive
|
|||
|
|
by-products from atomic explosions. This occurs when the nuclear or atomic
|
|||
|
|
blast is a ground rather than air-burst (air-burst meaning that the fireball
|
|||
|
|
is far enough from the earth's surface that there is no ground material
|
|||
|
|
uptake into the high temperature portion of the mushroom cloud). In an air-
|
|||
|
|
burst the bomb products condensate into such very small particles that they are
|
|||
|
|
aloft for such a long time that they are mostly non-radioactive by the time
|
|||
|
|
they come down, typically months or years. The fission process gives off
|
|||
|
|
hundreds of different radioactive elements and isotopes. Also, a certian
|
|||
|
|
portion of the fission mass does not fission. The fussion portion of nuclear
|
|||
|
|
bombs is clean and gives off only helium, the atomic bomb trigger (fission)
|
|||
|
|
which starts the nuclear bomb (fussion) is the portion of the bomb that leaves
|
|||
|
|
radioactive by-products.
|
|||
|
|
These by-products can be classified by their characteristics. One
|
|||
|
|
characteristic is half-life. The half-life is the length of time it takes for
|
|||
|
|
an element to give off one-half of its total radioactivity. This would also be
|
|||
|
|
the length of time required for a given amount to change to one-half the
|
|||
|
|
radioactive level, in other words if something was giving off radiation that
|
|||
|
|
would yield 3 Rads/hours, after one half-life it would give off 1.5 Rads/hour.
|
|||
|
|
An unstable isotope only emits radioactivity when one atom decays to
|
|||
|
|
another isotope or element (which may or not be stable, stable being non-
|
|||
|
|
radioactive). Therefore the portions of the element that are not in the
|
|||
|
|
process of decaying are not giving off any radioactivity. If you have
|
|||
|
|
"X" number of atoms of a radioactive element, "X/2" of those atoms will give
|
|||
|
|
off their radioactivity in the half-life period and become a different element
|
|||
|
|
or isotope. If an element has a half-life of 1 day, a given amount of it will
|
|||
|
|
give off 1/2 of its total radiation during the 1st day, 1/4 during the second
|
|||
|
|
day, 1/8 the 3rd day, 1/16th the 4th, 1/32 the 5th, 1/64 the 6th, 1/128th the
|
|||
|
|
7th, et cetra. If you have a short half-life like Iodine 131 of 8, days most
|
|||
|
|
of the radioactivity (99+%) will be emitted in two months. In a long half-
|
|||
|
|
life element like plutonium 239 with a 24,400 year half-life, 1,000,000 atoms
|
|||
|
|
would in 24,400 years give of 1/2 of their radioactivity leaving 500,000 atoms
|
|||
|
|
of plutonium 239 at the end of those 24,400 years. 500,000 decays over 24,400
|
|||
|
|
years equals approx. 21 decays per one year.
|
|||
|
|
Another characteristic is the type of radiation given off, Alpha, Beta, or
|
|||
|
|
Gamma radiation. Neutron radiation is only given off by the actual blast
|
|||
|
|
itself and is not given off by the fallout itself. Only neutron radiation
|
|||
|
|
can MAKE something that is not radioactive become radioactive. This is why
|
|||
|
|
fallout can not cause something (like food inside a can) to become radioactive.
|
|||
|
|
Alpha, beta, and gamma radiation can NOT make anything become radioactive.
|
|||
|
|
Alpha radiation (helium nucleus, 2 protrons and 2 neutrons), like from
|
|||
|
|
plutonium, can be shielded with one layer of Cellophane or newspaper or several
|
|||
|
|
inches of air. Beta radiation (an electron) can be shielded by a layer of
|
|||
|
|
drywall, or several feet of air. Gamma radiation is electromagnetic radiation.
|
|||
|
|
Neutron radiation is a neutron and is about twice as hard to stop as Gamma.
|
|||
|
|
Gamma and neutron are harder to stop, you need several feet of dirt or
|
|||
|
|
concrete to absorb them. See below for specifics for stopping Gamma radiation.
|
|||
|
|
One factor that most people don't realize about fallout is how fast it
|
|||
|
|
decays. Fallout follows the t-1.2 law which states that for every sevenfold
|
|||
|
|
increase in time after detonation there is a tenfold drop in radiation output.
|
|||
|
|
Example, a reading of X level of radioactivity at Y hours after detonation
|
|||
|
|
would indicate a level of radioactivity of .1X at 7Y hours after detonation.
|
|||
|
|
This is accurate for 2,500 hours (14 weeks) following the explosion,
|
|||
|
|
thereafter the doserate is lower than t-1.2 would predict. Example, if a
|
|||
|
|
dose rate of 100 REM/hr was found at 1 hour after detonation(this assumes all
|
|||
|
|
significant fallout from the bomb has fallen, therefore starting with the
|
|||
|
|
seven hour point is probably more realistic) would be 10 REM/hr at 7 hours,
|
|||
|
|
1 REM/hr at 49 hours(2 days), .1 REM/hr at 343 hours(2 weeks), .01 REM/hr at
|
|||
|
|
2401 hours (14 weeks). A "survival safe" dose of radiation (this being defined
|
|||
|
|
as no short term effects or disability) is 3 to 12 Rads/day. This dose rate of
|
|||
|
|
3-12 Rads/day can only be taken to an accumulated dose of 150-200 rads if done
|
|||
|
|
day after day. This would occur (assume 6 Rads/day) in this example at 150
|
|||
|
|
hours for 24 hour exposure, or at 49 hours for a 6 hours per day outside of
|
|||
|
|
shelter. Note though that since the level of activity is decreasing the time
|
|||
|
|
spent outside every day would increase. If you increase the radiation by a
|
|||
|
|
factor of 10 for another example would be where you would have 1,000 Rem/hr at
|
|||
|
|
1 hr, 100 Rem/hr at 7 hrs., 1 Rem/hr at 343 hrs., .1 Rem/hr at 2401 hrs. The 24
|
|||
|
|
hour exposure would be at 1,000 hours(41 days) and 6 hour work day outside of
|
|||
|
|
shelter at 300 hours(12 days).
|
|||
|
|
For various levels of contamination a "no short term effects" dose of 6 Rads
|
|||
|
|
per day would be something like this: (for 80 col. printout)(measurements at
|
|||
|
|
boundries of the oval shaped pattern)
|
|||
|
|
|
|||
|
|
Hours from Dose rate Hours of "safe" work outside per day, medical effect
|
|||
|
|
explosion
|
|||
|
|
EXAMPLE A An area 10 miles wide by 30 miles downwind directly downwind
|
|||
|
|
from of a missle field that gets dozens of hits
|
|||
|
|
1 hr. 10,000 R/hr None, 100% dead at 6 minutes of exposure
|
|||
|
|
7 hrs. 1,000 R/hr None, 100% dead at 1 hour of exposure
|
|||
|
|
2 days 100 R/hr None, 50% dead within 3-4 hour continuous exposure
|
|||
|
|
2 weeks 10 R/hr 36 minutes. 50% dead for 2 day continuous exposure.
|
|||
|
|
14 wks(3 mo) 1 R/hr 6 hours/day. 50% dead for 1 month continuous exposure
|
|||
|
|
5% dead for 15 day continuous exposure, no medical care
|
|||
|
|
and no deaths for 1 week continuous exposure.
|
|||
|
|
EXAMPLE B An area 10 miles wide by 30 miles downwind of a single 1 MT
|
|||
|
|
ground burst
|
|||
|
|
1 hr 1,000 R/hr None, 100% dead at 1 hour of exposure
|
|||
|
|
7 hrs. 100 R/hr None, 50% dead within 7-8 hour of continuous exposure
|
|||
|
|
2 days 10 R/hr 36 minutes. 50% dead for 5 days of continuous exposure.
|
|||
|
|
2 week 1 R/hr 6 hours/day. 50% dead for 1 month continuous exposure.
|
|||
|
|
14 weeks 0.1 R/hr All day. 0% deaths from radiation hereafter.
|
|||
|
|
EXAMPLE C An area 12 miles wide by 95 miles downwind for a single 1 MT
|
|||
|
|
ground burst
|
|||
|
|
1 hr radiation has not arrived yet.
|
|||
|
|
7 hrs. 50 R/hr 12 minutes, 50% dead for 18 hour continuous exposure
|
|||
|
|
2 days 5 R/hr. 1 hour, 5% dead for 2 week continuous exposure
|
|||
|
|
2 weeks 0.5 R/hr 12 hours/day.
|
|||
|
|
14 weeks 0.05 R/hr Unlimited.
|
|||
|
|
The above three examples indicate conditions and exposures that would only
|
|||
|
|
be acceptable in wartime. In these examples the wind is continuous in
|
|||
|
|
direction and velocity. A real wind would not make such nice neat ovals. It
|
|||
|
|
should be noted that even in real wind conditions, marching perpendicular to
|
|||
|
|
the depositing wind will remove you from a individual fallout zone.
|
|||
|
|
|
|||
|
|
Here is an example of the levels of contamination from a single 1 MT ground
|
|||
|
|
burst with a 15 MPH wind
|
|||
|
|
Area downwind Arrival Accumulated total radiation dose Dose Rate in Rads/hr
|
|||
|
|
(boundries) time for at
|
|||
|
|
in miles fallout 1 week 4 weeks 15 weeks 100 yrs 7 hrs. 2 days(14 hrs)
|
|||
|
|
33 x 7 1.5 hrs 3000 R 3300 R 3600 R 4600 R 100 R/hr 10 R/hr
|
|||
|
|
95 x 12 5 hrs. 900 R 1200 R 1400 R 1700 R ~50 R/hr 5 R/hr
|
|||
|
|
160 x 18 10 hrs. 300 R 400 R 460 R 650 R not there yet 2 R/hr
|
|||
|
|
245 x 20 16 hrs 90 R 120 R 150 R 240 R not there yet 0.7 R/hr
|
|||
|
|
|
|||
|
|
For shelter from Gamma radiation the standard rule of thumb is 150 pounds of
|
|||
|
|
mass per square foot of cross section of shelter wall yields a PF, protection
|
|||
|
|
factor, of 40. This means if you had two shelters on a flat contaminated field
|
|||
|
|
with one having walls of one layer of cellophane and the other of walls and
|
|||
|
|
ceiling of something that had for its thickness 150 lbs/sq. ft.( note this
|
|||
|
|
would be a thickness of 2.5" of lead, 4" of steel, 12" of concrete, 18" of
|
|||
|
|
soil, 30" of water, 200' of air) you would recieve 1/40th the dose in the 150
|
|||
|
|
lb/sq.ft. walled shelter. This effect can be multiplied. If the sq. ft. cross
|
|||
|
|
section was 300 lbs. that would be 1/40th of 1/40th or 1/1,600th of the
|
|||
|
|
unprotected dose. Take for example a dose rate starting at 100 Rem/hr at 1
|
|||
|
|
hr.,10Rem/hr at 7 hrs.,1 Rem/hr at 49 hours, etc. If exposure started at 1
|
|||
|
|
hour the total dose would be 240 R in 1 day, 310 R in 1 week, 350 R in 4 weeks,
|
|||
|
|
390 R in 15 weeks. The same in a PF 40 shelter would be 6 R in 1 day, 7.7 R
|
|||
|
|
in 1 week, 8.7 R in 4 weeks. The difference would be 5% fatalities-most
|
|||
|
|
others suffering from nausea and taking about 1 month to recover without the
|
|||
|
|
protection versus 0% fatalities-0% sickness with protection of PF40 in this
|
|||
|
|
case.
|
|||
|
|
Another example with a dose rate starting at 1,000 Rem/hr at 1 hr., 100
|
|||
|
|
Rem/hr at 7 hrs., 10 Rem/hr at 49 hours, etc. If exposure started at 1 hour the
|
|||
|
|
total dose would be 2,400 R in 1 day, 3,100 R in 1 week, 3,500 R in 4 weeks,
|
|||
|
|
3,900 R in 15 weeks. This in a 40 PF shelter would be 60 R in 1 day, 77 R in a
|
|||
|
|
week, 87 R in 4 weeks. In a 1,600 PF shelter this would be 1.5 R in 1 day,
|
|||
|
|
about 2 R in 2 weeks, about 2.5 R in 15 weeks. The differences here would be -
|
|||
|
|
no protection = 100% fatalities in several hours - PF 40 = 0% fatalities, 25%
|
|||
|
|
suffer nausea(at the most) with total recovery in 7 days, - PF 1600 no effects.
|
|||
|
|
Please note that protection factor increases as a multiple. If 150 lbs/ft.
|
|||
|
|
sq. = a PF of 40(1/40th or 2.5%), 300 lbs/ft sq. = a PF of 1,600(1/1,600th or
|
|||
|
|
0.0625%), and 450 lbs/ft. sq. = a PF of 64,000(1/64,000th or 0.0015625%)
|
|||
|
|
|
|||
|
|
Typical Swiss domestic shelters have a PF of 16,000 to over 2,500,000.
|
|||
|
|
|
|||
|
|
|