-— 7h wr 137¢s contributed 76° to 78 percent Of these three isotopes 695 and 1256p, of the total exposure rate and 60¢0 and 125s, each contributed about 10 to 12 percent. These resuits were in agreemenc with gamma field estimates derived from soil sampling data. Also identified at levels tog, low to significantly contribute to the total exposure fate were 155Eu, Eu, 24lam, and possibly 106gh, Table 1 tat ar Gamma Radiation Rates in Bikini Atoll . mR/hr fi The TLD results on the O Transect showed the same trend as in Figure 72, although these values are slightly higher on the average. Table Ll shows a summary of the range of exposure rates on Bikini, the levels applicable to various locations, and the major contributor to the gamma radiation levels. Bikini vegetation clearing experiment a planting coconut trees and other food plants could have some effect on population exposures if radionuclides in plants contribute significantly to the external radiation field, A vegetation clearing experiment was planned and conducted on Bikini. The area chosen for the experiment was near the center of the istand. The dense vegetation at this location, mainly scaevola, was about three meters high, At a point marked by a stake a complete set of spectro- Island Center “OBO. pos ’ Eneu “o_o 002-.010 omens 137 ¢5 Nam -O10~ .330 600, 13Tes Outer Edge -O10- .030 N.E. Corner -110-.330 ; . Rojkere, Eonjebi oole.020 "006-010 was cleared to 3 meters, 6 meters, and 9 meters radius. Eneman 001-257 These measurements were repeated as a circular area Bikdrin, Lele The radiation levels At the request of the Trust Territory District Agriculturist, vegetation The amount of vegetation removed from this smalt The results of the experiment indicate that clearing vegetation has little immediate effect on total exposure rate, However, subsequent weathering of the same as before. “p03 +030 1010-235 Lukoj oJ . Eneu is the second largest island in the atoll. It containa many buildings and several steel towers and is less heavily overgrown with scrub vegetation There was easy access to the interior of the island and a road along the lagoon shore was quite visible. Portable instrument measurements were made along this road and along a path parallel to the ocean shore on the other side of the island. Spectrometer and ionization chamber measurements were made at two places on the lagoon side of the island. along the Lagoon road to remain about two weeks. 060-.200 ° Jelete Oroken .060-.130 .015-.045 Bokdrolul Bokbata Aomen-Iroi,) Complex: -020- .050 -010-,030 .010~ .035 Bokaetoktok Enew than Bikini. -003-.235 East Enidrik West Enidrik ; Aomen Lomilik ; a Odrik, Iroij * 60¢ 1 ; .005-.020 .020- .330 -O10-.040 TLD's were placed *No soil satple or field spectra measurements. o» Rh 020+ 057) Enidrik area was very large amounting to almost 2,500 kilograms. 0 . oe ero West, Eneman These results give an indication of potential cleared areas and termination of cycling of radionuclides through scrub plants could lead to lower radiation levels. The cleared area was resurveyed two weeks later upon return to Bikini. The radiation Level was found to be about "00 7s East Eneman removed during the vegetation clearing experiment was separated as to type, agricultural productivity. , -003-.010 Bokantuak, Tomelan, Aerokoj, Aerokojlol weighed, and data recorded. 7 .O15-.150 meter, ionization chamber, and portable instrument measurements were made bechanged very little as the area was cleared, 137¢s 0-080 . Aeroko, -Eneman Complex: fore any clearing began. . "Ooon obo Island Center The planned clearing of scrub vegetation on Bikini to make space for Contributors .OL0-.120 Hot Spots greater ter. Range Weathered Areas Close-to-Share A separate value is not given for the beta-gamma measure- = - Bikini ’ ments since even at ground level the gamma and beta-gamma values were essential ly the same. One exception was an area near the mid-point of the 1 Traneect where the beta-gamma levels were consistently higher but not significantly ‘ Ma jor Exposure Rate island 1255) ” ; 6%0, 125, 102m», B00, 1253.) l ; , Oemn * * * 60%o, 137f¢s * 60cq, 1255, *