102 Nuclear Forensic Analysis
mixed throughout the cascade. An important signature is thereby generated for forensic
a
nalysis:
a
s
t
he
235
U composition of the incompatible streams is optimized to give the
b
est
p
erformance
o
f
t
he
o
verall
c
ascade,
t
he
r
esult
i
s
a n
onoptimum
d
istribution
o
f
t
he
c
ompositions
o
f
t
he
o
ther
i
sotopes
o
f
U
.
F
or
e
xample,
i
n
a
n
i
deal
c
ascade,
234
U will actu-
ally
b
e
e
nriched
(
relative
t
o
i
ts
s
tarting
c
omposition)
t
o
a m
uch
g
reater
e
xtent
t
han
w
ill
235
U, since its relative stage separation factor is q
234
= (352/348)
1/2
= 1.00573, compared
t
o
q
235
= 1.00429 for
235
U. In reality, the relative enrichment of the two isotopes in US
m
aterial
i
s
a
pproximately
u
nity,
o
nly
s
lightly
f
avoring
234
U, and is characteristic of the
c
asc ...