CHAPTER SEVEN: RADIOLOGICAL CONDITION OF ISLANDS Text by M. G. Barnes and J. J. Giacomini, Desert Research institute Illustrations by Graphie Arts Group, Holmes & Narver,Inc. 7.1 INTRODUCTION All of the islands discussed in this Chapter tend to change shape gradually as the wind and waves erode some areas and build up others. Parts of some islands are especially unstable, undergoing substantial alteration during local tropical storms. approximate high tide line as of the fall of 1972. The island outlines in this Chapter show the In those cases where significant changes in coastline have oceurred since then, the approximate spring 1978 high tide lines are also shown. The results of the 1972 soil, vegetation, and animal sampling were helpful in guiding sampling efforts during the cleanup. Summaries of the 1972 data are given in Tables 7-1, 7-2 and 7-3, and details of the 1972 sampling methods and results can be found in the Enewetak Radiological Survey (NVO~-140, 1973). Descriptions of the surface and subsurface soil sampling procedures used during the cleanup are in Sections 4.2 and 6.9 of this report. Information about the in situ measuring system (the IMP) and related procedures is in Section 3.2. Many of the island discussions reference Tech Notes which can all be found in Appendix B. Text for each island includes introductory sections labelled 'Background' and '1972 Survey Results". Material for these sections was obtained largely from the Enewetak Fact Book (NVO-214, 1982) which was compiled for field use during the summer of 1977, and found to be an invaluable aid during the entire cleanup period. The 'Background' sections contain reference to "H + 1 hour exposure rate," and a ranking based on this value. This is a technique devised by Lynch and Gudiksen, originally published in NVO-140, pp. 81-83, as a crude effort to estimate the relative amount of fallout deposited on each island. They normalized early time radiation readings to H + 1 hour values and summed contributions from all nuclear tests on the atoll to arrive at a "total H + 1 hour exposure rate received" value for each island. The stated value is not relevant to the present radiological condition of any island. For the purpose of reporting the radiological condition, the islands are grouped first according to radiological history, then according to geographic location. All of the nuclear events which Significantly affected any island took place on or north of island Yvonne. The islands south of Yvonne are discussed in Section 7.2, "Southern Islands." Islands west of Irene are discussed in Section 7.3, "Northwest Islands." Islands which were not the site of a nuclear test, and which lie between Janet and Yvonne, are discussed in Section 7.4, "Northeast Islands." Islands used as sites for nuclear tests, and requiring some soil removal, are discussed in Section 7.5, "Soil Removal Islands." The reports in Section 7.2 discuss the background and history of the southern islands, and summarize the 1972 and cleanup sampling results. None of these islands required soil excision (except for one very small area on Elmer) or large-scale sampling efforts during the cleanup. Sections 7.3 and 7.4 give the same background and summary information about the northwest and northeast islands. These sections also include maps of each island with soil and IMP sampling locations, isopleth maps showing the surface TRU characterization, and a discussion of activities during the cleanup. There are two important aspects of these discussions that should be noted. The first deals with the usage of final IMP data versus original IMP data and a reference to Tech Note 23. Following the completion of the project, a decision was made to collect more data concerning characteristics of the Enewetak soil. This additional information resulted in a change in the IMP conversion factor which in turn affected the 241Am numbers. Cleanup decisions were based on data calculated using the original conversion factor, thus, original data are used in describing what actually occurred 203