Table 4. Measured and Predicted Rate-of-Rise of Exposure Rate at Rongerik Atoll Time Post-Detonation, Hours 6.87 6.91 6.95 7.04 7.12 7.20 7.29 7.37 % Change During Half Hour Measured Exposure Rate mR hla 0.18 0.70 2.7 3.6 10.5 30 60 100 55,000 Peterson's Predicted Exposure Rate mR h~la 220 240 _ 270 330 400 480 — §80 700 320 8Multiple by 2.58 x 1077 to obtain C kg7! nv. C. Radioiodine Surface Activity Based on Archival Soil Analyses for 1297 1. The Archival Soil Sample Collection. Surface soil samples were removed from Rongelap, Utirik, and other atolls in the Marshall Islands during the period 1954 to 1974. They were taken at depths up to two inches. Samples were stored at the University of Washington's Applied Fisheries Laboratory. Soil samples tested for 297 were either midisland soils with humus, sandy soils from all parts of the island, black and white beach sands, grey powdery soils, randomly collected composites, or humus~seedy mixtures. Of the thousands of sam- ples stored at the University, several hundred were identified for neutron acti- vation analysis. Samples were packed and sent to Battelle Pacific Northwest Lab- oratory and analyzed by Brauer (Br80). Ze Analysis of Samples. ~125gp, 137¢g, 155Eu, and ©0Co. Soil samples were analyzed for 1277, 1297, ‘The methods for neutron activation analysis were described by Brauer (Br74) and Keisch (Ke65). lLIodine was separated from soils according to the method of Studier (St62). Once separated, the iodine was irradiated with neutrons in a nuclear reactor, purified to reduce levels of interfering nuclides, and assayed using gamma spectroscopy (Br80). For quality control, comparison samples containing known amounts of 51, 1272, and 1291 -10-