mec/m! at 12 hours after Shots 2 and 3, respectively. The instrument used was sensitive
to 107° mc/m!if the background gammafield was less than 0.5 r/hr.
Weatherside filter samples counted at 10 days after the shot yielded values of about
2 x 10° counts/min/ft® of air drawn through them. This value represents an average
over the time from the start of fallout till shutdown of the filters approximately 19 hours
after detonation.
:
Time , Hours
The standard ventilating system operating at 1,000 ft?/min resulted in an activity concentration in the cubicle which was a factor of 1 x 10™ to 2 x 10™ lower than that above
or
o8
oe
iy
a
B& Steet , inches”
412
ss
ue
Figure 6.3 Apparent absorption coefficient » as a function of time.
decks. Changing the flow rate had no appreciable effect, but the Naval Research Laboratory (NRL; preciprotron or Army Chemical Center (ACC) paperfilters were approxi-
mately 95-percent effective in further reducing the activity.
During recovery and decontamination operations, the airborne activity concentration
was almost always less than 0.1 mc/m*. Respirators were worn by personnel operating
a Tennant resurfacing machine principally for protection from flying chips.
6.2.5 Radiation Surveys. The radiation condition aboard an unmanned ship was first
estimated from data telemetered from a fixed gamma-detector station. A second orderof-magnitude estimate was derived by multiplying a reading made from aboard the recovery tug by a calculated factor. For purpose of scientific experiments and personneldosage prediction, more-accurate surveys were utilized. The ships were mnarked at
approximately 900 points on the interior and exterior. The surveys were performed at
these locations by groups of previously inexperienced Navy enlisted men. Surveys in-
cluded readings of gammadoserate at 3 feet, beta surface readings, directional gamma83