180
C. H. Pyeon
4
5
6
7
8
9
10 11 12 13
14 15 16
17 18 19 20 21 22
23 24 25 26
A
G r G r G r G r
G r G r G r G r G r G r
G r G r G r
G r G r G r G r G r G r
G r G r G r G r
F
B
G r
Gr
D
G r
Gr
40
E
G r
Gr
G
G r
Gr
14
H
G r
p
p
p
p
p
p
p
p
p
p
p
G r
I
G r
p
p
p
p
p
p
p
p
p
p
p
G r
f
J
G r
p
p
p
p
p
p
p
p
p
p
p
G r
K
G r
p
p
F
F
F
F
F
p
p
G r
p
L
G r
p
p
p
F
F
f
F
F
p
p
p
G r
M G r
p
p
p
F
f
f
f
F
p
p
p
G r
O
G r
p
p
p
F
F
f
F
F
p
p
p
G r
Q
G r
p
p
F
F
F
F
F
p
p
G r
G r
R
G r
p
p
p
F
F
F
F
F
p
p
p
G r
T
G r
p
p
F
4 0 1 4 4 0
F
p
p
G r
U
G r
p
p
p
p
p
p
p
p
p
p
p
G r
V
G r
p
p
p
p
p
p
p
p
p
p
p
G r
W G r
p
p
p
p
p
p
p
p
p
p
p
G r
X
Gr
p
Gr Gr
Gr Gr Gr
Gr
p
p
Gr
Y
G r
G r
G r
G r
Z
G r
G r
G r
G r
Z' Gr Gr Gr Gr
Gr Gr Gr Gr Gr
Gr Gr Gr Gr Gr Gr
Gr Gr Gr Gr
Polyethylene reflector
Normal fuel (1/8"p60EUEU)
Partial fuel (1/8"p40EUEU)
Partial fuel (1/8"p14EUEU)
Neutron source (Am-Be)
Fission chamber
Uncompensated ionization chamber
Reference fuel (1/8"Al40p20EUEU)
Polyethylene moderator
Graphite
Aluminum sheath
Control rod
Safety rod
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. 7.3 Top view of the KUCA A-core in Bi sample reactivity worth experiments (Reference core)
(Ref. [3])
7.1.2 Experimental Settings
In the sample reactivity experiments, a test-zoned fuel region was arranged for
measuring the effects of substituting Al plates for Pb or Bi ones upon the criticality.
In the test zone, five test fuel assemblies were set around the core at positions (14,
M), (15, L), (15, M), (15, O) and (16, M), as shown in Figs. 7.1 and 7.3. The patterns
of sample reactivity experiments were ranging between three and five, as shown in
Fig. 7.5, substituting the reference fuel rods for Pb or Bi fuel rods. The test fuel rod
was the same as in the reference fuel rod substituting Al plates for Pb or Bi ones
shown in Fig. 7.6. The spectrum of experimental core at KUCA was compared with
that of LBE core [4] in the JAEA ADS model, as shown in Fig. 7.7. The experimental
core was a relatively hard spectrum one implemented in KUCA, though not to a fast
spectrum core in actual ADS. The substitution was conducted in a total of 40 unit
cells of the central region of fuel rods, such as changing Al plates in Figs. 7.2d and
7.4d into Pb and Bi ones in Figs. 7.6a, b, respectively. The sample reactivity caused
by the substitution was experimentally obtained through the difference between the
excess reactivities of Al reference core and Pb or Bi test core. In the experiments, the
critical state was adjusted by maintaining the control rods (C1, C2 and C3) in certain
positions shown in Tables 7.1 and 7.2; the excess reactivity was then deduced by the
difference between the critical and super-critical states in the core. The experimental
C. H. Pyeon
4
5
6
7
8
9
10 11 12 13
14 15 16
17 18 19 20 21 22
23 24 25 26
A
G r G r G r G r
G r G r G r G r G r G r
G r G r G r
G r G r G r G r G r G r
G r G r G r G r
F
B
G r
Gr
D
G r
Gr
40
E
G r
Gr
G
G r
Gr
14
H
G r
p
p
p
p
p
p
p
p
p
p
p
G r
I
G r
p
p
p
p
p
p
p
p
p
p
p
G r
f
J
G r
p
p
p
p
p
p
p
p
p
p
p
G r
K
G r
p
p
F
F
F
F
F
p
p
G r
p
L
G r
p
p
p
F
F
f
F
F
p
p
p
G r
M G r
p
p
p
F
f
f
f
F
p
p
p
G r
O
G r
p
p
p
F
F
f
F
F
p
p
p
G r
Q
G r
p
p
F
F
F
F
F
p
p
G r
G r
R
G r
p
p
p
F
F
F
F
F
p
p
p
G r
T
G r
p
p
F
4 0 1 4 4 0
F
p
p
G r
U
G r
p
p
p
p
p
p
p
p
p
p
p
G r
V
G r
p
p
p
p
p
p
p
p
p
p
p
G r
W G r
p
p
p
p
p
p
p
p
p
p
p
G r
X
Gr
p
Gr Gr
Gr Gr Gr
Gr
p
p
Gr
Y
G r
G r
G r
G r
Z
G r
G r
G r
G r
Z' Gr Gr Gr Gr
Gr Gr Gr Gr Gr
Gr Gr Gr Gr Gr Gr
Gr Gr Gr Gr
Polyethylene reflector
Normal fuel (1/8"p60EUEU)
Partial fuel (1/8"p40EUEU)
Partial fuel (1/8"p14EUEU)
Neutron source (Am-Be)
Fission chamber
Uncompensated ionization chamber
Reference fuel (1/8"Al40p20EUEU)
Polyethylene moderator
Graphite
Aluminum sheath
Control rod
Safety rod
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. 7.3 Top view of the KUCA A-core in Bi sample reactivity worth experiments (Reference core)
(Ref. [3])
7.1.2 Experimental Settings
In the sample reactivity experiments, a test-zoned fuel region was arranged for
measuring the effects of substituting Al plates for Pb or Bi ones upon the criticality.
In the test zone, five test fuel assemblies were set around the core at positions (14,
M), (15, L), (15, M), (15, O) and (16, M), as shown in Figs. 7.1 and 7.3. The patterns
of sample reactivity experiments were ranging between three and five, as shown in
Fig. 7.5, substituting the reference fuel rods for Pb or Bi fuel rods. The test fuel rod
was the same as in the reference fuel rod substituting Al plates for Pb or Bi ones
shown in Fig. 7.6. The spectrum of experimental core at KUCA was compared with
that of LBE core [4] in the JAEA ADS model, as shown in Fig. 7.7. The experimental
core was a relatively hard spectrum one implemented in KUCA, though not to a fast
spectrum core in actual ADS. The substitution was conducted in a total of 40 unit
cells of the central region of fuel rods, such as changing Al plates in Figs. 7.2d and
7.4d into Pb and Bi ones in Figs. 7.6a, b, respectively. The sample reactivity caused
by the substitution was experimentally obtained through the difference between the
excess reactivities of Al reference core and Pb or Bi test core. In the experiments, the
critical state was adjusted by maintaining the control rods (C1, C2 and C3) in certain
positions shown in Tables 7.1 and 7.2; the excess reactivity was then deduced by the
difference between the critical and super-critical states in the core. The experimental