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