76
N-7
The whole-body
counter
measures
the quantity
and the energy
of
the gamma ray photons
that have been emitted
by cesium-137,
or other
In principle,
the
radionuclides,
and that
escape
from the body.
machine
is calibrated
by measuring
the escape
of gamma rays
from a
phantom which has been loaded
with the radionuclides
in question.
Obviously,
the whole-body
counter
comes closest
to giving
a direct
measurement
of the body-burden.
The collected
data obtained
with it
are presented
in Tables
N.7,
#l,
#2, and #3.
.
or
In the case of radionuclides
that
emit beta
rays
(strontium-90
alpha
particles
(transuranics),
whose range
in tissue
before
absorption
may be at most a centimeter
or so down to some
micrometers,
another
method must be used.
Recourse
is had to
The body
measuring
the daily
radionuclide
excretion
in the urine.
content
is then calculated
from knowledge
of the metabolism
of the
radionuclide
in question.
This method
is not as reliable
as
whole-body
counting.
Fortunately
in the present
case,
the detection
of strontium
and the transuranic
elements
is not as important
as the
detection
of cesium.
The dose can also
be calculated
from the diet.
The primary
obstacle
here is that
the diet
is very difficult
to ascertain
accurately,
and in addition
more assumptions
must be made regarding
the metabolism
of the radionuclide
than would be the case
above.
The Livermore
results
are based
on this
method.
Conversely,
knowing
the daily
urinary
output
of a radionuclide,
it is possible
to calculate
the daily
intake
by ingestion.
For
example,
based on the work of Jones
et al (1985),
Skrable
et al
(1987)
and Moss (1988),
Dr. E. T. Lessard
of the Brookhaven
Laboratory
has calculated
the factors
for plutonium-239
given
in
Table
N.4 # 4.
Uhen the daily
intake
is multiplied
by the factor,
the urinary
output
is obtained.
Conversely,
when the urinary
output
is known, dividing
it by the factor
will
predict
the daily
intake.
The dories and Moss alternatives
are offered;
at 20-30
years
on a
constant
diet,
they differ
by a factor
of 1.75.
I used the
Moss-based
factor
for
the calculations
used in the text,
Section
4.3,
because
it corrects
for earlier
errors
in the data base which
Jones
did not know about.
(Cont.)