1.0 FRACTION OF TOTAL FLUX . / / Cs Cs . / 0.2 0.1 / / L j f / 2 4 6 8 10 12 16 20 24 28 DIAMETER d, (m) FIGURE 3-5. FRACTION OF THE TOTAL FLUX REACHING THE COLLIMATED DETECTOR ORIGINATING FROM A CIRCLE OF DIAMETER d DIRECTLY BELOW THE DETECTOR FOR A DETECTOR HEIGHT OF 7.4 m. the 60 keV gammaray of 155Eu, as discussed in Section 3.2.7. Data for 187Cs and 69Co were used to obtain external exposure rate values for use in the post-cleanup dose assessment. The selection of these particular isotopes for detailed analysis was based on previous data (see, for example, NVO-140) which indicated that the primary gamma-ray-emitting radionuclides at Enewetak were 2414 m, 137Cs and 89Co. Random visual inspection of the complete spectrum tended to support this assumption with the exception of Pearl, where measurable levels of barium-133 were detected. 99