~~ It will be used during the "digging yr method which would serve this purpose. phase" of Cleanup. When these rough analyses indicate that the Cleanup ofa site iscomplete, however, the more accurate laboratory analyses will be made for confirmation that soil removal may terminate. . 5. oe The AEC ‘Survey reported a weak correlation between the amount of americium in Enewetak soil and the amount of Pu; namely, the Am-241/Pu-239+ 240 activity ratio ranged between about 0.1 and 0.5. Americium-241 is relat~ively easy to detect quantitatively since it is a gamma emitter--some gammas will penetrate a soil sample thereby making the separation of Am from the soil _matrix unnecessary. Thus, if techniques become available to predict an acceptable ratio of Am-241/Pu-239+240 at any specific location, then Pu concentration might be promptly inferred from a laboratory determination of the Am-241 concentration in soil samples. Moreover, if the Pu-239+240 and Am-241 depth distributions also can be adequately predicted, then the Pu concentration may be inferred by an in situ measurement of the Am-241 activity as described in References 8 and 9. These indirect methods may be availab to support Cleanup; however, for planning purposes, the principal analytical methods will be Pu alpha radiation counting, either with or without chemical.. o . .eh er GA lvl 2 Catan etek tee EE OP bo ves ee olin a separation. Are ca az. Bas Tacs oc. Cr yed cr og aet# eS wr piace "os d mot = 7 FS -C. . PROCEDURES tk note Troag J8 10%3 cin T.. Tavern vt gad UDase soy nd a The specific locations from which samples will be taken in highconcentration regions will be determined by the requirements of the automatic contouring program which is emploved, As is often the case, more than one set of sanples will be needed before acceptable concentration contours _evolve. The locations to be sampled in subsequent sampling rounds will be indicated by the contouring results achieved from earlier rounds. Engineer— ing and operations considerations will also play a part in determining how and where samples must be selected; e.g., the bounds of a region woyjd not ._ be refined better than the minimum capability of the earth-moving equipment to be used in the region. For the low-concentration regions, however,Sample locations will be selected on a random basis as was done by the AEC Survey, ep since these data are to be collected merely toconfirm the absence of any significant Pu contaminated soil, and not to structure concentration contours. The exact locations (horizontal coordinates and elevations) from which samples are removed will be determined _by engineer surveyors. wets i boars “2. 2 BES co £ hag NAL L. ottee _— ype a3 Sate ey tl. aeeeat SagET eeTea 4 Samples will be removed from the surface by means of a "Cookie cutter” type tool which will permit removing top soil to a depth of 5m within a rectangular area 10 cm by 10 cm. The 5-cm depth is a compromise e ~ .. .. dimension between the thinner (near-surface) samples preferred by persons who consider the prime Pu hazard to be that of resuspension by natural ' phenomena; e.g., wind, rain, animal movement, etc., and the thicker samples <. 1, preferred by those who fear resuspension by mechanical means such as might accompany the plowing of a site for agricultural purposes. .Moreover, the 5-cm depth dimension is conservative since the AEC Survey found that most profiles diminish with depth and Pu concentration frequently peaks slightly : r . fae ‘ae hes tr ’ ’ 1 Le 9 cee - -3 a : 7 Ag hae keuw we! . . 4 Re“ bet eyfon Pe Ta, ; ~ . "He ETyet: vaiMo bes sae a 4 . ae 9 te pm aceee .le meen. , tos? we . otee