consistent with the observation that almost the entire activity on the surface of Rongelap was
found on the first inch of soil. Some simple leaching experiments were conducted with samples
of the soil from Rongelap and Uterik, but no conclusive results were obtained.
An intensive study was made concerning thehalf life of material obtained from a semi-
traile: that had been exposed to(@@4vd jandl@0mzicontamination. This rate of decay information was desired so that levels of contamination could be approximated upon arrival in the
United States. The sample indicated a half life of approximately 28 days. Task group personnel interested in complying with the Interstate Commerce shipping regulations foundthis in-
formation helpful.
5.5
CONCLUSIONS AND RECOMMENDATIONS
5.5.1
Conclusions
1. Present military and civilian instruments are still humidity sensitive during amphibious
operations.
2. Du Pont film packet 559 with modifications will be adequate.
3. Present commercial pocket dosimeters are inadequate for use at the Pacific Proving
Gruunds,
4. Present methods of exposure recording need to be studied and improved.
5. Lagoon contamination can be followed adequately by visual observation of the sediment
appearing in the lagoon and byutilization of a standard type survey meter.
6. The evaporation system of the ships for obtaining fresh water provides adequate means
for removing radioactive particulate material, at least for the concentrations encounteredin
Operation Castle,
5.5.2
Recommendations
1. Consideration should be given to the improvementof the air seal on the compartment
housing the high-megohm resistors and the electrometer tubes in the PDR-39. The high humidity at the Pacific Proving Grounds affects these components and causes the instrument to
become inoperative.
2. Study should be initiated in an effort to obtain increased low-range sensitivity, complete waterproofing, and improved emulsion stability for the Du Pont 559 film packet.
3. Study should be initiated in an effort to obtain reduced electrode leakage, stability under
rough handling, and easy decontamination of a pocket dosimeter suitable for use at the Pacific
Proving Grounds.
4. Study should be initiated to simplify the record method and to improve the reliability of
records maintained at the Pacific Proving Grounds.
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