picture.
In almost all cases no direct accurate quantitative data for
man are available.
Animal data, occasional accidents involving human
exposure, theory, and opinion constitute the basic data for setting
standards and estimating the degree of hazard for various levels of
exposure to radiation.
The fact that the fall-out radiation field is
a decaying field which for local fall-out is rapid at first and then
slows down, has important biological implications.
This makes the time
of entry into the field as well as duration of stay necessary parameters
to consider in computing biological recovery factors.
Each of the parameters involved in human hazard will be discussed
in order to arrive at a quantitative scheme for assessing the isolated
characteristic, e.g., lethality.
Deviations from this ‘standardized
scheme due to particular aspects of any single situation will be dis-
cussed.
This basic standard wili constitute a reference and may be
used as a point of departure for other situations.
For some of the
parameters of interest sufficient data are not available.
In fact,
even in assessing lethal expectation, the scheme is subject to limitations but represents the best data available at this time.
Lethality Expectation for Total Body Irradiation. The assessment of acute, i.e. within 30 days, lethality expectation due to
exposure to radiation in a fall-out area involves several complex
phenomena, both physical and biological.
At present a simplified
approach seems likely to yield the best general picture.
Variations in
the physical decay factor, the gt? law, are likely to be small and
will not be considered.
For the biological factors involved, quantita-
tive constants which are admittedly somewhat tenuous will be applied
and used without considering variations from the values commonly employed.
The basic curve for predicting lethality due to instantaneous
total body ganma radiation is given in Figure 12.17
17
Until the CASTLE
Mitchell, H.H., A General Approach to the Problem of Estimating
Personnel Dosage on Atom Bonbed Targets, The RAND Corporation,
RM-1149, 1953, SECRET.
63