ESTIMATED TRU CONTENT AND RECOMMENDED DISPOSITION OF YVONNE HIGH-GRADE SOIL/DEBRIS STORED IN HARDTACK STATION 1610 BUNKER DOE/ERSP TECH NOTE NO.14.0 DATED: 21 May 1979 AUTHORS: D. H. Denham, PNL N. R. Johnson, EIC Summary Based on recent grab sampling and evaluation of previously collected data, such as Field Radiological Support Team (FRST) hot-spot survey data, JTG Rad Con Division files, and DOE Tech Advisor notes, it is concluded that the material currently stored in the referenced bunker on Yvonne contains about 60 mCi (TRU). Mueh of this activity appears to be uniformly spread throughout the 400-plus plastic bags of collected soil /debris. The remaining activity, about 10 mCi, is contained within a few bags of soil or in discrete chunks which have been isolated in separate containers. These discrete chunks appear to be weathered metal fragments (possibly molten in the past) with or without concrete/soil attached. Because of the relatively small TRU content of this debris (tens of millicuries) compared to the estimated quantities already disposed of in the Cactus Crater (tens of curies), all of the material in the bunker (including the leaking 137Cs source) should be removed from the bunker and disposed of in the central portion of the Cactus Crater dome. Introduction and Background With the initiation of the Enewetak cleanup effort in the spring of 1977, a major concern was the possibility of finding particles of plutonium metal, especially on the island of Yvonne. All radiological survey efforts since 1971 have confirmed that the northern half of Yvonne is a heterogeneous conglomeration of radioactive debris, both on the surface and buried. The complexity of the radiological conditions on this section of the island was produced by several nuclear events, Most notably Quince, which failed to produce a fission yield resulting in the dispersal of the plutonium within the device by the high explosives. The rather detailed FIDLER survey late in 1972 (NVO-140) led to the isolation of milligram-size fragments of plutonium. However, no mention is made of whether these "hot particles" were gathered into a common area or whether they were disposed of in the lagoon or other "suitable" location. Soil Collection and Storage For a period of approximately one month (28 November through 23 December) in 1977 a group of the Air Force FRST were deployed with PG-2 survey meters to locate and bag up "hot spots" in the Fig/Quince area on Yvonne. Only those soil/debris areas yielding greater than 3000 cpm near the surface (on contact) were to be included. At each location thus defined, an initial reading (epm) was taken followed by alternate soil removal (in about one-ineh increments) and resurvey. In general, two soil layers were removed and put in a plastic bag at each location. If the count rate was below 3000 cpm after the first scoop of soil was removed, no further soil was removed. About 450 such locations were found with the initial or succeeding count rates ranging from slightly above 3000 cpm to upwards of 500,000 epm per location. At some point, probably in the spring of 1978, all of these bags were numbered and transported to the Hardtack Station 1610 bunker. Each of the plastic bags were tied shut and sequentially numbered by marking pen on a piece of masking tape. A list of the bag numbers and the location from which the samples came fe. sO many meters and direction from the applicable grid stakes) was made by the FRST. That list enumerated 437 bags, 35 of which were noted as torn when placed in the bunker. In addition to the above "record", Capt. Peter H. Meyers (Rad Con Division) prepared a memorandum for record entitled "Field Sample Survey" dated 29 May 1978. In that memorandum Capt. Meyers listed 9 samples which were radiologically evaluated by the Rad Con Division and also placed in the Hardtack bunker. Of these 9 samples, only the two "baby food jars" indicated beta-gamma_ radiation levels significantly above the ambient background. No external B-14-1