Consider now the question of residual low level radiation from
one war acting on succeeding generations, causing a new equilibrium for
mutation rate.
On the basis of residual activity present, according
to the Hunter-Ballou tables, the only significant background gamma
radiation after 20 years will be contributed by the’ element cesium-137,
with a 37 year half-life, which decays to barium-137, with a 2.5 minute
half-life, which emits a 0.7 mev gamma ray.
Only gamma radiation is
considered since practically no beta radiation will reach the germinal
cells.
It is of interest to calculate the amount of fission yield
which would have to be released in order to double the natural background radiation dose-rate due to the uniform distribution of artificial
radioactive materials at some future time, e.g., 20 years. Assume:
1. Beckground radiation = 0.0125x10"> r/nr = 0.3 m/2h hours.
2.
Cesium-137 is the long-lived isotope with a strong gamma
which will be the main contributor to increasing the background.
70
curies of cesium-157 are formed per KT fission yield.
3.
Area of earth = ex10° square miles.
4,
One megacurie of cesium-137 per square mile will give a
radiation dose of 4 r/hr at three feet above ground.
5.
Thus :
Uniform world-wide distribution of the isotope.
a- 70 curies of cestum-197 _ 5.52107! curies cesim-137/
3
exl0”
b.
square miles
I, = te.
mi>fer
This is the equation for radioactive
decay for a single isotope in which
I.
t
= 0.0125x107> r/hr
I = radiation dose rate due to cesivum~-137 at H+l hour
eA 0.69 for t = 20 years...
I= se
°
et
95°