
379
17
Inferred Production
Estimates
Fissile fuels are required for the operation of nuclear weapons. Although there are
s
ome
r
elatively
e
xotic
m
aterials
t
hat
ca
n
b
e
us
ed
f
or
t
his
p
urpose
(
e.g.,
233
U), the most
l
ikely
f
uels
f
or
w
eapons
a
pplications
a
re
P
u
a
nd
U
h
ighly
e
nriched
i
n
235
U (HEU
o
r
O
ralloy).
P
lutonium
a
nd
H
EU
w
ere
rst
p
roduced
i
n
t
he
1
940s
b
y
t
he
U
nited
S
tates
a
nd
t
he
S
oviet
U
nion
at
t
he
i
nception
o
f
t
heir
n
uclear
w
eapons
p
rograms
(
see
C
hapter
1
).
S
ince
t
hat
t
ime,
l
arge
q
uantities
o
f
b
oth
h
ave
b
een
p
roduced
i
n
m
any
c
ountries—including
s
ome
w
ithout
a
cknowledged
w
eapons
p
rograms.
P
lutonium
and HEU are difcult to produce, requiring