1. Preliminary Study on Accelerator Based D-D Neutron Generator with Hydrocarbon Liquid Target
Jeong-Jeung Dang, Kyoung-Jae Chung, Y. S. Hwang *
Department of Nuclear Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea
Abstract
This study proposes a new concept of a beam-target type neutron generator (NG) based on deuteron-deuteron (D-D) fusion reaction. The conceptual design of the neutron generator introduces 10 MeV class accelerator to achieve high neutron yield and energy. Especially, the neutron yield on beam direction significantly increases, because not only a cross section of D-D fusion reaction steadily increases and is sustained up to 10 MeV, but also an anisotropy of the D-D fusion reaction is enhanced on the beam direction. In addition, 10 MeV beam energy allows that the D-D neutron energy reaches over 13 MeV which is similar value of deuteron-triton (D-T) fusion reaction. Furthermore, in order to increase the neutron yield, a cryogenically-cooled hydrocarbon liquid target is adopted. A proof-of-principle experiment for the liquid target was conducted in a vacuum.
Advantage of D-D neutron generator with 10 MeV beam
High yield and beam power efficiency
High neutron energy
Forward biased neutron flux
Introduction
FIG. 5. Forward flux and
forward flux/beam power
Why high yield and energy compact NG is required ?
Application [1,2]
- Neutron activation analysis
- Neutron radiography
- Nuclear data production
- Material irradiation test
- Transmutation
- Medical isotope production
Cryogenically Cooled Hydrocarbon Liquid Target
Neutron Yield of Hydrocarbon Liquid Target
Cryogenically cooled hydrocarbon liquid target
- Self-cooling and self healing
- Low energy loss rate
- Cryo-cooling for reduction of
vapor pressure
Comparison of neutron sources
Materials
Deuterium
concentration [#/cm3]
Triple point (liquid target)
Pressure [Pa]
Temp. [K]
TiD1.6
9.07 × 1022 -
D2O (s)
6.12 × 1022
C3D8 (liq.)
4.98 × 1022
1.7 × 10-4
85.5
C2D5OD (liq.)
6.18 × 1022
4.3 × 10-4
150
Neutron sources
Fission Reactor
Large accelerators
Compact neutron sources†
Spallation
IFMIF
Cf-252††
D-T
D-D
Neutron yield [n/s]
~ 1018
1017
2.3 x 109
~ 1010
~ 108
Neutron flux [n/cm2/s]
~ 1015
1016
1015
~ 106
~ 107
~ 105
Neutron energy [MeV]
thermal ~ 2
thermal
14 (peak)
2.3
14.1
2.45
Scale [m]
~ 101
~ 102
< 0.1
< 1
†. Neutron flux of compact
neutron source is the
flux at 10 cm away from
the source.
††. 1 mg
Table I: Physical properties of neutron emission target
High yield and high energy compact NG should be developed to extend the applications.
Numerical Study on Accelerator Based D-D Neutron Generator
Neutron Yield of Beam-Target
Neutron Generator [1]
Ib : Beam current
Ct : Hydrogen isotope concentration in target
Eb : Incident beam energy
dE/dx : Beam energy loss rate of target
εX: Stopping cross section of element X
Neutron Energy of Beam-Target Neutron Generator
θ : Neutron emission angle
FIG. 1. Fusion cross section and
stopping cross section of target materials
FIG. 6. Neutron yield of various target material.
FIG. 7. Energy loss rate and beam penetration
depth (effective target thickness) of
various target material.
Proof-of-Principle Experiment of Hydrocarbon Liquid Target
Operation Condition and Result of Cryogenically-cooled Liquid Target [3]
- Target temperature: 150 K
- Base pressure: < 1 x 10-3 Pa
- Flow rate: 265 Liters/min
- Flow speed: > 5.6 m/s
- Pressure: 6.7 x 10-2 Pa (Min.)
2.7 x 10-1 Pa (CW)
Assumption
- Target material: Titanium hydride (TiH1.6)
- 100% of D+ ion, 1 mA beam
‼ The pressure inside the neutron
generator should be maintained lower
than 10-1 ~ 10-3 Pa for stable operation [4].
FIG. 8. (a) Schematic view of liquid target
system. (b) Picture of liquid ethanol
target fabricated in vacuum
Conclusion
This study suggests new concept of the D-D neutron generator which can achieve the high neutron yield and energy without tritium. The highly accelerated beam up to 10 MeV will enhance not only the total neutron yield but also the forward yield and the neutron energy. Also, the hydrocarbon liquid target is expected to reduce the required beam current by its low energy loss rate, and treat the high energy beam by the self-cooling and healing function.
This study is useful to develop the intensive neutron generator which is applicable for the fusion material irradiation test as well as the neutron activation analysis, neutron radiography, medical application and so on.
FIG. 2. Neutron yield of D-D and D-T neutron
generator with 1 mA beam.
FIG. 3. Normalized neutron energy spectrum of
D-D NG according to beam energy.
Anisotropy and Forward Flux of Beam-Target Neutron Generator
- Anisotropy of flux: differential cross section, beam energy
- In practice, the neutron flux distribution biased the forward direction is efficient
for the neutron generator, because the neutron field behind the target is mainly utilized.
- Forward flux is defined as following:
Acknowledgement
This research was supported by National R&D Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT & Future Planning (No. 2014M1A7A1A )
Reference
[1] J. Csikai, CRC Handbook of Fast Neutron Generators, Vol. I, CRC Press, Boca Raton,
p. 25, 1987.
[2] S. G. Kim, Generation of isomeric cross sections and a study on D-T neutron application for
production of therapeutic radioisotopes, Ph. D. Thesis, Seoul national university, 2006
[3] Y. S. Hwang, et al., R&D on Neutron Generator for ITER Neutron Diagnostics, Final report,
Seoul National University, Ministry of Science, ICT and Future Planning, Korea, 2014.
[4] H. Nakamura, et al., Status of engineering design of liquid lithium target in IFMIF-EVEDA,
Fusion Engineering and Design, Vol. 84, p. 252, 2009.
Beam
Target
15o
FIG. 4. Normalized angular flux of D-D NG
KNS Spring Meeting, May , 2016, Jeju Korea
P07B30