or, in still more abbreviated form, ³²S_{n,p}³²P. Phosphorus-32 atoms do
not emit gamma rays upon disintegration and so are not detected in
standard whole body counters. Attempts are being made, however, to adapt
some whole body counters to pick up the secondary radiations, called
bremsstrahlung, that occur when the high-energy beta particles that are
emitted by phosphorus-32 collide with other atoms.
[Illustration: Figure 14 _Whole body counter record of evidence that a
cyclotron worker has picked up higher-than-average quantities of
radioactive zinc-65. Note how the graph shows peaks at specific energy
levels identifying the radionuclides._]
[Illustration: Figure 15 _Graphic evidence that a radioactive gas
accidentally inhaled by a worker at an experimental reactor contained 3
radioactive isotopes of iodine._]
[Illustration: Figure 16 _The number of 1.38-Mev gamma rays emitted by
sodium-24 in the body of a reactor accident victim indicates he received
about 900 rads of neutron irradiation._]
_Figures 14 through 16 illustrate the kind of data that whole body
counters provide to help physicians care for people involved in
accidents._
Similarly, neutron bombardment of natural sodium (²³Na) atoms in the
body produces sodium-24. This reaction is written: ²³Na(n, gamma
ray)²⁴Na. The 1.38-Mev gamma rays emitted by sodium-24 are detected
effectively by whole body counters. Since a given neutron dose converts
a known proportion of ²³Na atoms to ²⁴Na, it is possible to determine
how much neutron exposure a worker has received by obtaining his body
count of radioactive sodium.
Crystal type counters also were used in an interesting special case of
excessive radiation exposure. Seven natives of the Marshall Islands were
examined by the whole body counter at the Argonne National Laboratory in
1957. Another whole body counter, mounted in a Navy amphibious landing
ship, was taken to Rongelap Atoll in the Marshalls several times to
check on the health of all the residents of the atoll. These people had
accumulated zinc-65 in their bodies as a result of contamination of
crabs and other food items by fallout from the March 1954 atomic bomb
tests at the Pacific Proving Ground. Although normal radioactive decay
progressively reduced the total amount of radioactivity in the area, the
Marshallese still were carrying this nuclide in their bodies after
several years. (See _Atoms, Nature, and Man_, another booklet in this
series, for a more complete report of this study.)