that the fallout particles originated as calcium carbonate (coral)
which was converted to calcium oxide by the heat of the detonation.
This rapidly changed to calcium hydroxide with the formation of a
very thin layer of calcium carbonate on the outer surfaces. Particles
were influenced by a sea water environment which caused the formation
of an insoluble shell of magnesium hydroxide, surrounded by calcium
carbonate. On the interior of the shell, weliedeveloped hydrated
calcium sulfate crystals (gypsum) were formed. This leaching effect,
by causing partial solution and reprecipitation of the soluble
calcium compounds, was felt to account. for the adherence of the
particles, As indicated above, experimental evidence supports the
view that ion exchange is primarily responsible for the adherence of
the contamination at CASTLE, However, the role of ion =xchange in the
wet contamination-decontamination behavior of materials will require
further exploration before its implications are fully understood,
Appreciable differences in initial contamination levels existed
among the various panel surfaces with no evident correlation to
surface properties. Vertical surfaces facing upwind became equally
or more highly contaminated than pitched or horizontal surfaces,
probably due to the combined action of wind currents and tenacious
contaminant.
A possible explanation for this phenomenon is that deposition
of wet contaminant was irfluenced by wind currents which tended to -
impact the contaminant onto surfaces normal to the wind,
Although
this effect was most pronounced on shipboard contaminated panels
following Shots 2 and
wnere ship speed into the wind and ship
structural georetries may increase the impact, the contamination
of panels on the stationary barge following Shot 6 exhibited similar
relationships. The effect of slope panels used during Shot 6 were
all of the same material and had similar contamination characteristics, The construction material panels were placed at the same
mounting slopes as practiced in building construction. No direct
comparison of identical surfaces at different slopes can be made with
these panels, but it is important to ccmpare the contamination of
materials at the slopes as they are encountered in actual buildings.
The experinental decontamination work was done in a sequence of
operations and only qualitative comparisons between decontamination
methods can be made.
If a less efficient method were applied after |
a more efficient one, it is believed that only negligible removal
would result. The selection of the sequence of the different
decontamination metheds was predicated on laboratory tests as
suggested in reference’.
The basic physical parameters which appear to affect resistance
to wet or slurry forms of contamination and/or ease of decontamination
are impermeability to moisture, non-absorptivity, and hardness,
Results illustrating the effects of these parameters are presented as
part of Table 4.6.
Smoothness of surface did not appear to be as
important for wet and slurry forms of contaminant as it was for the
dry form found at JANGLE.
Scrubbing followed by flushing seems to have been the most
effective and economical of the reclamation techniques employed. Furthermore, the addition of a detergent increased the effectiveness
39
CONFIDENTIAL— RESTRICTED DATA