72
WORLDWIDE EFFECTS OF ATOMIC WEAPONS
both simple and possible to calculate from the available data of Eisenbud what
fraction of the Sc*” from MIKE will have fallen out after 30 years if the presentrate
of fallout continues unchanged. This would still seem to be a pessimistic assumption, and it is likely to give a number considerably less than 100 per cent. For
low-yield bombs, the 100 per cent assumption is probably not unduly pessimistic.
5. Concerning assumption (4), experiments such as that of Dr. Larson, but
conducted with Sr" rather than Sr*", are clearly desirable. General opinion seems
APPENDIX I
by you, namely, to assay the Sr®° content in bones of various animals including
humans, and particularly in sewage and feces, at the present time to pet more
reliable data.”
CALCULATIONS ON ASSUMPTIONS OF H. A. BETHE
The basic assumptionis
to be that Sr°° would not remain exchangeable evenif it is so originally,
"6. Concerning (c), it seemed to me that we should disregard the old data
indicating about 30 parts of Sr per 1000 parts of Ca in soil. But that we might
reasonably use the new data which give about three atoms of Sr per 1000 of Ca.
This would still indicate an advantage factor of 10 for the incorporation of Sr into
of uniform body radiation of gamma-rays. I believe that the accepted principle is
correct according to which neutrons are much more dangerous than gamma-rays per
unit energy. If this is teue, then also beta-rays must be much less dangerous than
(2)..=(8)
Ca
or
the bone as compared to Ca, and thus would increase the allowable fission yteld by
a factor of 10.
"7. Concerning (d@), I believe that the international tolerance of one microcurie
of Sris really inconsistent both with the accepted tolerance of Ra and with that
73
( <)
Ca
body
Ca
aol
_ (e)
body —
Ca
soll.
Of
so \
(Sr )eorr = (Ca) sors (= )
body
alpha-rays. I further believe that it is really correct to make a direct comparison of
With 1 yc of Sr®° fixed in the bone, we have
over the bone. With these assumptions, onc gets a tolerance dose of 10 microcurics
Sr
5 x 10-3
(© Yoo ~~ gga= FTO,
a0
39
assuming that 1 cm? of topsoil weighs 30 gm, giving a content of 30 mg ofcal-
beta-rays with gamma-rays provided the beta-emitter is really uniformly distributed
of Sr? when distributed uniformly over the bone. This follows both from the
accepted Ra tolerance and from the accepted gamma-ray tolerance. Of course, this
number is entirely consistent with an assumed one microcurie if the latter is concentrated near the more sensitive parts of the bone, as it would probably be for an
adult who has been exposed to Sr only for a few months or years. However, in
this case the average bone of this adult will contain a lower concentration of
Sr”
compared to total Ca than the food which the person has consumed recently. This
factor of uncertainty is eliminated when we talk about the level of Stin the food
and in those parts of the bone which have been recently laid down. It seems to me
entirely reasonable and safe to accept the 10 microcurie tolerance in connection with
the calculations of c.ABRIEL.
.
"8. Concerning (e), nothing but renewed investigation of the chemical com-
position of soils can help. If there is less Ca, the allowable number of megatons
will be reduced proportionally. Concerning (f), Larson’s experiments seem to
1:
‘
Terre wath
ju 14
ee
f
do Ghllim,
"9. If the ratio of Sr’? to Ca in animal bones, etc., is equalto that of the soil
from which the food is derived, or less, as it seems to be, then the application of
bone mealfertilizer will not change the ratio unfavorably.
“10. I think it és very essential to go through with the investigation proposed
cium, and assuming 2(¢) in the previous section.
The required amount of Srin soil to bring that soil to tolerance capability is
1.5 1O™ gm Sr’/cm? = 4 mg Sr**/mi?. The area of the earth being 2 X 108
mi?, the total requirement for tolerance is then 800 kg of Sr®°, which represents a
fission encrgy of 800 MT.?
PROJECT SUNSHINE FORMULA
The energy release in megatons from fission bombs that would be required to
bring the population of the earth to any given level T of Sr deposited in the
skeleton, if the individuals grew from birth to maturity in an environment con-
CamMmated Untormy produced, can be expressed by the following.
(No decay of Sr°° is assumed and the Sr®° is assumed to be 100 per cent available
for incorporation in the biological sequence from soil to man.)
Let
MT = the number of megatonsoffission energy released,