the introduction of a neutron guide and a beam duct is requisite to lead the highenergy neutrons generated from the heavy metal target to the center of the core as
much as possible. In the uranium-loaded ADS experiments, the proton beam
parameters were 100 MeV energy, 0.01 nA intensity, 30 Hz pulsed frequency,
100 ns pulsed width, and 80-mm diameter spot size at the tungsten target (100 mm
diameter and 9 mm thick). The level of the neutron yield generated at the target was
around 1.0 Â 10
6 1/s by the injection of 100 MeV protons onto the tungsten target.
9.2.2 Thorium-Loaded ADS Benchmarks
In the ADS with 100 MeV protons (Fig. 9.3), the fuel rod was composed of a
thorium metal plate and a polyethylene (PE), graphite (Gr), or beryllium
(Be) moderator arranged in the A-core. Other components were selected from
HEU and natural uranium (NU; 2 Â 2 Â 1/8 in.) plates. The cores were composed
of Th-PE (Fig. 9.4), Th-Gr, Th-Be, Th-HEU-PE, and NU-PE, according to a
selection of moderator materials: PE, Gr, Be, HEU-PE, and NU-PE, respectively,
and spallation neutrons were generated outside the core after injection onto the
tungsten target. The thorium-loaded ADS experiments were conducted especially
to investigate the relative influence of different neutron profiles on capture reactions
of
232 Th and
238 U: the reaction of
238
U was taken as reference data for evaluating
the validity of
232 Th capture cross sections.
20 19 18 17 16 15 14 13 12 11 10
K
J
I
TP
H
G
TP TP TP TP TP
E
TP TP TP TP TP
D
TP TP TP TP TP
Tungsten target
B
TP TP TP TP TP
A
TP TP TP TP TP
Proton beams
A'
Thorium fuel
and polyethylene
Polyethylene
Indium wire position
3 He #1
3 He #2
3 He #3
Fig. 9.3 Top view of thorium-loaded ADS core with 100 MeV protons
84
C.H. Pyeon