73 lines
4.9 KiB
Plaintext
73 lines
4.9 KiB
Plaintext
|
|
Survival 101-Fallout Fundamentals
|
|
Courtesy Ken Seger's BBS
|
|
(314) 821-2815
|
|
|
|
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 particles condensate into such very small particles that they are aloft
|
|
for such a long time that they are most non-radioactive by the time they come
|
|
down. The fission process gives off dozens of different radioactive elements
|
|
and isotopes. 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
|
|
a given quanity of an element to give off one-half of its radioactivity. 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 decaying are not giving off
|
|
any radioactivity. If you have Avagadro's number of atoms (1 mole) of a radioactive element
|
|
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 like plutonium 239
|
|
of 24,400 years 1 mole the amount would be less than 4/1,00th of 1%.
|
|
Another characteristic is the type of radiation given off, Alpha, Beta, Gamma,
|
|
or neutron radiation. 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 say a layer of drywall, or several feet of air. Gamma radiation is
|
|
electromagnetic radiation. Neutron radiation is a neutron. Gamma and neutron
|
|
are harder to stop, you need several feet of dirt or concrete to absorb them.
|
|
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 since detonation there is a tenfold drop in radiation output.
|
|
This is accurate for 2,500 hours following the explosion, thereafter the dose
|
|
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 would occur (assume 6 Rads/day) in
|
|
this example at 150 hours for 24 hour exposure, or 49 hours for a 6 hours per
|
|
day outside of shelter. If you increase the radiation by a factor of 10 for
|
|
another example 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 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 protection
|
|
factor of 40. This means if you had two shelters on a flat contaminated field
|
|
one had 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 a dose.
|
|
Take for example a dose rate starting at 100 Rem/hr at 1 hr.,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. 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.
|
|
Another example with a dose rate starting at 1,000 Rem/hr at 1 hr., 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.
|
|
|
|
|
|
Downloaded from P-80 Systems....
|