11 VALUES OF (uCi/m) /(mR/hr) From information given in Glasstone and Dolan (G177, pp. 390, 394), one can deduce the value of approximately 90 (uCi/m) /(mR/hr) at 24 hours postshot 1 m above 1 kt of unfractionated, unshielded fission products spread uniformly over a1 km 2 plane surface. The relevant calculation was repeated for the debris from the five shots listed in Table 1, incorporating the latest values of the correction factors, (Be80) uc i/m@ to mR/hr. The results gave an average value of 126 + 3 (wCi/m?)/(mR/hr) at 24 hr postshot 1 m above unfractionated, unshielded fission products spread uniformly over an infinite plane surface. This new value is considerably more accurate and precise than the one deduced from the information given in Glasstone and Dolan (G177, pp. 390, 394). The marked differences ‘in neutron spectra and fissioning species of these five shots affect this quantity very little, because the vast majority of the external gamma-ray exposure is due to the fission products at the peaks of the distribution curve. The yields of these nuclides change little with changing fissioning nuclides and neutron spectra. Values of (uC i/m2) /(mR/hr) were measured from the fallout of 13 tower shots and 3 balloon shots (Bas8, La66, Ra54). The values for the tower shots were calculated with the assumption that only half of the refractory elements were present. This assumption lowers the value of (uC i/m2) /(mR/hr) by about 7%. The debris from the balloon shots was assumed to be unfractionated. Surface roughness effects were 2 simulated by a relaxation length of 0.16 g/cm’. shown in Table 2. The results are