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April 20, 1956
lerril Eisenbud, Director
Health and Safety Laboratory
Ira B. Whitney, Assistant Chief
Analytical Branch, Health and Safety Laboratory
ZINC-65
IN SEA WATER
SYMBOL: HSA: IBW
The effect of short-lived radionuclides induced in soil or sea
water might have considerable effect upon aerial monitoring with-
in a few days of time sero.
Also, if certain long-lived nuclides
Were produced, and if these wereconcentrated by marine life, then
detectable quantities would be found in fish.
Therefore, a series
of calculations were made to determine the level of induced radionuclides in sea water.
The calculations are based on two assumptions. First, it is
assumed that the explosion takes place in an infinite medium.
Under these conditions there is an expanding sphere of neutrons
which are thermalized rapidly.
Secondly, it is assumed that one neutron per fission is available
for production of (n¥) or other reactions in the sea water. Although this assumption may not be rigorously accurate, it can be
used as a basis for calculations. Since 1.38 X 10°3 fissions are
produced per KT of fission yield, it is assumed that this number
of neutrons is available for nuclear reactions in sea water (or
other substances). Using this value, one mole of neutrons will
be available from 4.22 KT of fission yield.
The curies of radioactivity due to impurities in sea water can be
calculated using the following formula:
fo =
where:
A, =
Non'g-!
Ene 3.7 X 1010)
curies at t = 0
No = 6,02 X 1023 neutrons
n't = number of atoms of impurity/ml
o' =
ne =
A
I0023bb
atomic cross section of element
sumaation of number of atoms of each element times
its cross sections (including stable to stable
reactions )
= decay constant of nuclide in atoms/second
.