1000 supplied a mumber of portable G-M counter survey meters plus a large number of These instruments and their calibration are described in HASL-190, (2) Dietoalt gitBe Bikini This the largest island in the atoll is about 4 kilometers long and 0.8 kilometers wide. It is heavily overgrown with scrub vegetation, primarily scaevola. This vegetation is quite impenetrable having a height of about three meters. The former Bikini village site is located mid-island and a short distance inland along the lagoon shore, While somewhat overgrown, the village road was passable and the initial gamma and beta-gamma measurements, gamma spectra determination, and TLD emplacements were made here while other team menbars and workers cut the first trail across the island from the lagoon to the ocean shore. This trail, which took one whole day to complete, was known ae the O Transect. As to the level of monitoring effort, portable scintillation counter readings were made every 15 meters along the O Transect. Geiger counter readings were made and TLD's emplaced every 45 meters. At each location, four measurements of gamma and four of beta-gamma were made sround a point at a height of about | meter and again at ground level. These values were averaged to obtain the ganuma and beta-gamma level at one meter and at the surface for that location. Similar measurements at increments of 45 meters were made and TLD's emplaced along 640 meters of the village road, along the 869 meters of a second lagoon to ocean trail known as the 1 Transect, and along the much shorter North End and South End Transects. _ Tonization chamber and spectrometer measurement were made at locations on the 0 Transect and on the village road. Figure 2 shows a plot of the average of G-M counter gamma measurements made along the O Transect. The scintillation detector and spectrometer méssurements show a comparable picture, namely, low levels near the lagoon and ocean shores and higher levels in the interior. The dashed lines enclose most of the measurements. The levels along the 1 Transect show a similar pattern: The spectrometric results as developed by HASL staff indicated that the predominant gamma emitter in Bikini soil was 37Cs with lesser amounts of 700 600 500 400 External Radiation Measurement Results 300 , 200 ’ 100 imized and the TLD's would be emplaced for an exposure time of maximum duration. Segments of the shore party carried portable two-way radio equipment and there was a base station operator on duty in the ships communication room throughout the day. 12 Team members plus workers who cut trails through the heavy vegetation went ashore with their equipment in the early morning. Except for a mid-day rest period, work continued until dark, A daily log of each team members activity was prepared and the evening critique and planning session developed the schedule for the following day. In this way the impact of the time consuming and strenuous trail cutting operation was min- Figure 2. EXPOSURE RATE ON “O” TRANSECT GM COUNTER checked daily using a small button source. 800 + Field Operations The dase of operations for the team was the M.S. Militobi, a U.S. Trust Territory ship. Under the conditions for this survey, the monitoring instruments and equipment were transported repeatedly from the ship in small boats, through the surf on foot, and back again. The portable instruments were = 8 8 & IWYW-3LVY FYuNSOdX3 DISTANCE FROM LAGOON SHORE-METERS 900 TLD's.