NUCLEAR-DEBRIS FORMATION
31
1074
PHOTONS/SEC PER 10* FISSIONS
1075
1076
1077
1078
1079
107!
107"!
TT
—
107 !2
|
it
rc
10738
|
|
Pe My
ttt
rH
0.0
0.5
1.0
1.5
i
u
eed
2.0
2.5
PHOTON ENERGY, MEV
Fig. 12—-Gamma-photon
spectra from fission
ete
3.0
3.5
4.0
products at various
times after **U fission produced by athermonuclear neutron spectrum.
The relative contributions of the important gamma-emitting nuclides to the total dose-rate have been plotted vs. time in Fig. 14. It is
interesting to note that from a few days onward muchof the dose rate
at any given time can be accounted for in terms of two or three nuclides and that volatilely behaving mass chains contribute prominently
to the dose rate. The dose-rate contributions given here pertain, of
course, to unfractionated debris. Since many of the hard emitters (e.g.,
cesium and iodine isotopes) are subject to fractionation, the relative
dose-rate contributions will be greatly modified in the case of fractionated debris.