178
C. H. Pyeon
3
4
5
6
7
8
9
10 11 12 13
14 15 16
17 18 19 20 21 22
23 24 25 26 27
A
F
B
D
40
E
G
14
p
p
p
p
p
p
p
p
p
p
p
H
f
p
p
p
p
p
p
p
p
p
p
p
I
p
p
p
p
p
p
p
p
p
p
p
J
p
p
K
F
F
F
F
F
p
p
p
p
p
p
L
F
F
f
F
F
p
p
p
p
p
p
M
F
f
f
f
F
p
p
p
p
p
p
O
F
F
f
F
F
p
p
p
p
p
Q
F
F
F
F
F
p
p
p
p
p
R
F
F
F
F
F
p
p
p
p
p
T
F
4 0 1 4 4 0
F
p
p
p
p
p
p
p
p
p
p
p
p
p
U
p
p
p
p
p
p
p
p
p
p
p
V
p
p
p
p
p
p
p
p
p
p
p
W
p
p
p
p
p
p
p
p
p
X
Y
Z
Neutron source (Am-Be)
Fission chamber
Uncompensated ionization chamber
Polyethylene reflector
Aluminum sheath
Control rod
Safety rod
Partial fuel (1/8"p14EUEU)
Reference fuel (1/8"Al40p20EUEU)
Polyethylene moderator
Normal fuel (1/8"p60EUEU)
Partial fuel (1/8"p40EUEU)
UIC#6
N
N
FC
UIC
S
C
C2
S4
C3
S5
C1
S6
FC#3
FC#2
FC#1
UIC#4
UIC#5
Fig. 7.1 Top view of the KUCA A-core in sample reactivity experiments (Reference core) (Ref.
[1])
(conventional polyethylene) rods, and four different fuel assemblies: normal “F,”
partials “40” and “14,” and reference “f” fuel assemblies (Figs. 7.2a–d, respectively).
Normal fuel assembly “F” is composed of 60 unit cells, and upper and lower polyethylene blocks about 24
and 21
long, respectively, in an aluminum (Al) sheath. For
the normal and partial fuel assemblies, a unit cell in the fuel region is composed of
a highly enriched uranium (HEU) fuel plate 1/16
thick and polyethylene plate 1/8
thick. The numerals 40 and 14 correspond to the number of fuel plates in the partial
fuel assembly used for reaching the criticality mass. The reference fuel assembly “f”
is composed of 40 unit cells with an HEU fuel plate 1/16
thick and Al plate 1/16
thick, 20 unit cells of HEU and the polyethylene plate as in the normal fuel assembly,
as shown in Fig. 7.2d.
7.1.1.2 Bismuth Sample Reactivity Worth
The bismuth (Bi) sample reactivity worth experiments [3] were carried out in the
A-core (Fig. 7.3), which has polyethylene moderator and reflector rods, and four
different fuel assemblies, including HEU, polyethylene moderator (p), polyethylene
reflector (PE), graphite (Gr) and Al plate: normal “F,” partials “40” and “14” and test
“f” (Figs. 7.4a–d, respectively).
C. H. Pyeon
3
4
5
6
7
8
9
10 11 12 13
14 15 16
17 18 19 20 21 22
23 24 25 26 27
A
F
B
D
40
E
G
14
p
p
p
p
p
p
p
p
p
p
p
H
f
p
p
p
p
p
p
p
p
p
p
p
I
p
p
p
p
p
p
p
p
p
p
p
J
p
p
K
F
F
F
F
F
p
p
p
p
p
p
L
F
F
f
F
F
p
p
p
p
p
p
M
F
f
f
f
F
p
p
p
p
p
p
O
F
F
f
F
F
p
p
p
p
p
Q
F
F
F
F
F
p
p
p
p
p
R
F
F
F
F
F
p
p
p
p
p
T
F
4 0 1 4 4 0
F
p
p
p
p
p
p
p
p
p
p
p
p
p
U
p
p
p
p
p
p
p
p
p
p
p
V
p
p
p
p
p
p
p
p
p
p
p
W
p
p
p
p
p
p
p
p
p
X
Y
Z
Neutron source (Am-Be)
Fission chamber
Uncompensated ionization chamber
Polyethylene reflector
Aluminum sheath
Control rod
Safety rod
Partial fuel (1/8"p14EUEU)
Reference fuel (1/8"Al40p20EUEU)
Polyethylene moderator
Normal fuel (1/8"p60EUEU)
Partial fuel (1/8"p40EUEU)
UIC#6
N
N
FC
UIC
S
C
C2
S4
C3
S5
C1
S6
FC#3
FC#2
FC#1
UIC#4
UIC#5
Fig. 7.1 Top view of the KUCA A-core in sample reactivity experiments (Reference core) (Ref.
[1])
(conventional polyethylene) rods, and four different fuel assemblies: normal “F,”
partials “40” and “14,” and reference “f” fuel assemblies (Figs. 7.2a–d, respectively).
Normal fuel assembly “F” is composed of 60 unit cells, and upper and lower polyethylene blocks about 24
and 21
long, respectively, in an aluminum (Al) sheath. For
the normal and partial fuel assemblies, a unit cell in the fuel region is composed of
a highly enriched uranium (HEU) fuel plate 1/16
thick and polyethylene plate 1/8
thick. The numerals 40 and 14 correspond to the number of fuel plates in the partial
fuel assembly used for reaching the criticality mass. The reference fuel assembly “f”
is composed of 40 unit cells with an HEU fuel plate 1/16
thick and Al plate 1/16
thick, 20 unit cells of HEU and the polyethylene plate as in the normal fuel assembly,
as shown in Fig. 7.2d.
7.1.1.2 Bismuth Sample Reactivity Worth
The bismuth (Bi) sample reactivity worth experiments [3] were carried out in the
A-core (Fig. 7.3), which has polyethylene moderator and reflector rods, and four
different fuel assemblies, including HEU, polyethylene moderator (p), polyethylene
reflector (PE), graphite (Gr) and Al plate: normal “F,” partials “40” and “14” and test
“f” (Figs. 7.4a–d, respectively).