448 Nuclear Forensic Analysis
Although the relative concentrations of Np and Pu do not provide a conclusive
s
ignature,
t
he
r
eprocessing
o
f
s
pent
f
uel
b
y
me
ans
o
f
s
olvent
e
xtraction
w
ith
t
ributyl
p
hosphate
(
TBP)
(
the
P
UREX
p
rocess)
p
rovides
a
n
e
fcient
r
ecovery
o
f
P
u
a
nd
a
g
ood
d
econtamination
f
rom
ssion
p
roducts,
b
ut
l
eaves
N
p
w
ith
t
he
U
.
R
esidual
T
BP
w
as
i
dentied
i
n
o
rganic-rich
s
amples
c
ollected
at
t
he
P
aducah
s
ite.
I
t
w
ould
have been interesting to look for long-lived
129
I or
99
Tc in the site-inspection samples,
b
oth
o
f
w
hich
h
ave
uorides
t
hat
a
re
v
olatile
u
nder
t
he
s
ame
c
onditions
a
s
i
s
U
F
6
a
nd
w
hose
c
ontamination
l
evels
m
ight
p
rovide
f
urther
c
lues
t
o
t
he
r
eprocessing
t
echnique.
The
237
Np and residual Pu comprised a very small mass