The main parameters of the proton beams were 100 MeV energy, 0.3 nA
intensity, 20 Hz pulsed frequency, 100 ns pulsed width, and 40-mm-diameter spot
size at the tungsten target (50 mm diameter and 9 mm thick). The level of the
neutron yield generated at the target was around 1.0 Â 10
7 1/s by the injection of
100 MeV protons onto the tungsten target.
Prompt and delayed neutron behavior was monitored by placing three
3 He
detectors (20 mm diameter and 300 mm long) at three locations. Throughout the
time evolution of the prompt and delayed neutrons, the prompt neutron decay
constant was deduced by least-squares fitting to an exponential function over the
optimal duration. Subcriticality was deduced by the extrapolated area ratio method
[13] on the basis of prompt and delayed neutron behaviors. For 100 MeV protons,
neutron detectors (
3 He detectors: #1, #2, and #3) were set at three locations.
9.3 Results and Discussion
9.3.1 Uranium-Loaded ADS Experiments
9.3.1.1 Static Experiments
Thermal neutron flux distribution was estimated through the horizontal measurement of the
115 In(n, γ)
116m In reaction rate distribution by the foil activation method
using an indium (In) wire 1.0 mm in diameter. The wire was set in an aluminum
guide tube, from the tungsten target to the center of the fuel region [from the
position of (13, 14 – A) to that of (13, 14 – P) (Fig. 9.1)], at the middle height of the
fuel assembly. The experimental and numerical results of the reaction rates were
normalized using an In foil (20 Â 20 Â 2 mm) emitted by
115 In(n, n
0 )
115m In at the
target. In this static experiment, the subcritical state (0.77 % Δk/k) was also attained
Polyethylene (PE)
(590.55 mm)
Polyethylene (PE)
(622.30 mm)
Al plate (20.00mm)
Reflector 610.55 mm
(Lower)
Fuel 254.08 mm
(Unit cell 16 times)
Reflector 622.30 mm
(Upper)
Unit cell
(15.88 mm)
1/8”Th (1/8”NU)
(3.18 mm)
1/2”PE (1/2”Gr; 1/2”Be)
(12.70) mm
Fig. 9.4 Side view of Th-PE fuel assembly (TP) in thorium-loaded ADS core in Fig. 9.3
9 Accelerator-Driven System (ADS) Study in Kyoto University Research Reactor. . .
85
intensity, 20 Hz pulsed frequency, 100 ns pulsed width, and 40-mm-diameter spot
size at the tungsten target (50 mm diameter and 9 mm thick). The level of the
neutron yield generated at the target was around 1.0 Â 10
7 1/s by the injection of
100 MeV protons onto the tungsten target.
Prompt and delayed neutron behavior was monitored by placing three
3 He
detectors (20 mm diameter and 300 mm long) at three locations. Throughout the
time evolution of the prompt and delayed neutrons, the prompt neutron decay
constant was deduced by least-squares fitting to an exponential function over the
optimal duration. Subcriticality was deduced by the extrapolated area ratio method
[13] on the basis of prompt and delayed neutron behaviors. For 100 MeV protons,
neutron detectors (
3 He detectors: #1, #2, and #3) were set at three locations.
9.3 Results and Discussion
9.3.1 Uranium-Loaded ADS Experiments
9.3.1.1 Static Experiments
Thermal neutron flux distribution was estimated through the horizontal measurement of the
115 In(n, γ)
116m In reaction rate distribution by the foil activation method
using an indium (In) wire 1.0 mm in diameter. The wire was set in an aluminum
guide tube, from the tungsten target to the center of the fuel region [from the
position of (13, 14 – A) to that of (13, 14 – P) (Fig. 9.1)], at the middle height of the
fuel assembly. The experimental and numerical results of the reaction rates were
normalized using an In foil (20 Â 20 Â 2 mm) emitted by
115 In(n, n
0 )
115m In at the
target. In this static experiment, the subcritical state (0.77 % Δk/k) was also attained
Polyethylene (PE)
(590.55 mm)
Polyethylene (PE)
(622.30 mm)
Al plate (20.00mm)
Reflector 610.55 mm
(Lower)
Fuel 254.08 mm
(Unit cell 16 times)
Reflector 622.30 mm
(Upper)
Unit cell
(15.88 mm)
1/8”Th (1/8”NU)
(3.18 mm)
1/2”PE (1/2”Gr; 1/2”Be)
(12.70) mm
Fig. 9.4 Side view of Th-PE fuel assembly (TP) in thorium-loaded ADS core in Fig. 9.3
9 Accelerator-Driven System (ADS) Study in Kyoto University Research Reactor. . .
85