ABSTRACT
The bomb debris from surface, land and water shots at Operation
CASTLE was studied to determine the physical, chemical, and radio-~
chemical characteristics,
The fallout from the surface land shots consisted chiefly of
irregular white particles 25 » to 2 mm in diameter. They were derived
from coral and had the redioactivity concentrated near their surfaces,
About 5 per cent of the activity in the solid fallout was water soluble;
95 per cent dissolved in dilute acetic acid.
The fallout from the
surface water shots was invisible both in the air and after it had
deposited, It was collected on special filters and on a film by electroatatic precipitation, The filters and film and their autoradiographs
were studied microscopically. These studies showed that the fallout
consisted of microscopic solid crystals and small droplets, The autoradiographs indicated the presence on the filters of many particles
which were invisible under the microscope, The major part of the radioactivity was associated with crystalline aggregates and droplets up to
about 2 mm in diameter.
Water dissolved from 60 to 90 per cent of the
radionuclides from this type of fallout,
Fallout and cloud samples from land and water shots were analyzed
chemically for major constituents and trace elements including many of
the radionuclides. Coral and sea water contributed the major constituents, bomb products being present in trace concentrations, Radicchemical
analysis showed the valley of the fission product yield curve was about
20 times higher and the heavy wing at mass 156 about 6 times higher than
the yield curve from thermal neutrons on 0235,
The important induced
radionuclides were 0239-Np239, 0237, and 0240, The presence of these
had a marked effect on the decay curves and energy spectra especially
at intermediate times after detonation. The neptunium was distributed
between oxidation states; iodine occurred princivally as iodide,
The information obtained from these studies has aided in (a) an
understanding of the mechanism of formation of the fallout, (b) assess-
ing the radiological situation in fallout areas, (c) synthesizing simu-
lants for laboratory studies, and (d) interpreting data obtained in proof
tests of countermeasures for ships.