ee
§.1
Introduction
Fo.towine A Neueirandetonation in the spring
of 1954, a Jurge group of people were containinated with fission products. Tn addinon toa
sublethal external eamma radiation exposure
and beta irradiation of (he skin, delectable
amounts of radionuclides were deposited internally, It has heen assumed that in all situationsresuiting from a contaminating event, the
“tio ofexternal to internal dose would be exceedingly high, Iowever, a detailed ‘study of
the internal contamination in the exposed
human population and in animals was made to
determine the kind and dewree of internal
deposition. Three general problems were investigated: (1) The determination of the con-
tribution of the internal contamination to the
acute radiation svndrome observed; (2) The
possibility of long term effects, and (3) The
qualitative and quantitative nature of. the internal contamination produced by exposure of
individuals to mixed fission products. There
Was no Hrevious situation in which humanbe-
Ings Were exposed {o an environment contaminated with mined” fission products. -Concurrent studies were undertaken by the Japanese,
however, on radioactive materials to which a
small group of Japanese fishermen, near RongeJap at the time of the detonation, were exposed.
The report of the extensive investigations
undertaken on the ashes by the Japanese have
been published (4).
Evaluation of the internal contamination of
the human beings was made by a study of the
radioelements excreted: As very little infornation is presently available concerning the
ratio of excreted radioelements to the anrount |
deposited in the borly, it was necessary to base
the evaluation on data ubtained from animals
which had been contaminated in the same
event. Detailed studies of anima) tissues and
animal excreta then provided dita on which
estinuites of the human body burden were based.
5.2
General Nature of Internal
Radiation Toxicity
Tuk Nature Orthe radiation hazard frominternally deposited fission products can best be
understood in terms of the biophysical behavior
of the radionuclides.
_
Fission products entering the body through
inhalation ur ingestion concentrate in various
tissues and act as sources of internal radiation.
The ability of a radionuclide to enter the blood
strenm is determined byits solubility, chemical
properties and physical state. The radioelements formed in fission are predominantly oxides which have a limited solubility in bady
fluids. On this basis, only a few of the radioelements can becomeavailible to the body.
However, the amount which can produce injurions effects when deposited within the body
is minute because of the close proximity of the
ixotape to the tissues it irradiates, and because
the isotope continues to irradiate these Ussues’
until it is removed by biological turnover oris
rendered harmless by radioactive decay. The
effects of radiation frum internally deposited
emitfers are the same as those from external
radiation. ‘The disGngunishing feature of in-.
ternal radiation, however, is its long contiauing
nature.
.
Radioactive isotopes follow the same metabolic processes in the body as the naturally:
occurring inactive isotopes of the same element
and of chemically similar elements. Thus
strontium and bariwn, which are analogous
chemically to calcium, are deposited in the calcifying 1 ssneof the bone. Although nearly two
hundred radioisotopes are produced in the hssion process, only a few are potential chronic
Internal radiation hazards. These fission products, which are listed jn ‘Fable 5.1, constitute a
high percentage of the fission yield, and localize
chiefly in bene.
The “bone-seekers” have, in
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