JAEA-Conf 2011-002 - 日本原子力研究開発機構

water only case (Fig.4.), however the number of photon is drastically reduced to less than 10 5 level, and the
maximum energy is also decreased to the 10MeV from 14MeV.
In Fig.7, the case of the water layer of 0.75m, the iron layer of 0.25m and the concrete layer of 2.0m at
the same detector position is indicated. While the numbers of neutron and photon fall below the 10 1 -order
level, the photon energy extends to 8MeV. The maximum neutron energy is less than 5MeV, to be covered
by the specification of selected neutron monitor.
Flux [1/cm 2 /MeV/source]
10 5
10 4
10 3
10 2
10 1
no. = 5, reg = 10 -5
0 5 10 15 20
Energy [MeV]
Figure 6: Water & Iron
(M1 is water, r1=0.755m and M2 is iron,
r2=1.005m, without M3)
neutron
photon
JAEA-Conf 2011-002
no.=5, reg=10 -5
Figure 7: Water & Iron & Concrete
(M1 is water, r1=0.755m, M2 is iron,
r2=1.005m and M3 is concrete, r3=3.005m)
4. Conclusion
For an iron layer, the energy reductions of photon are evaluated by using PHITS code. In the case of
"water: 0.75m, iron: 0.25m, concrete: 2.0m", the numbers of neutron and photon fall below the 10 1 -order
level, and the photon energy range extends to 8MeV. This range exceeds the detectable limit of monitors,
and it is not enough for required shielding of gamma-ray. On the other hand, the neutron energy range, of
which maximum is less than 5MeV, is covered by the specification of detectors. However, dozens of
neutrons are counted at the outside of concrete, and it is not completely zero. For both neutron and
gamma-ray, therefore, an improvement of shielding components is furthermore necessary.
In the next step, the improved shielding components, a realistic model using beam dump structure and
the position with a degree of leaning for concrete wall in the accelerator vault will be used, and their energy
reduction including Air will be evaluated.
References
[1] IFMIF-CDA Team (Ed.) M. Martone, ENEA Frascati Report, RT/ERG/FUS/96/17 (1996).
[2] T. Kondo et al., J.of Nuc. Mater., 258-263,47(1998).
[3] T. E. Shannon et.all., J. of Nucl. Mater., 106(1998)
[4] A. Mosnier et al., MOPEC056, Proceedings of 1st International Particle Accelerator Conference (2010)
[5] H. Takahashi et al., P4-94, Symposium on Fusion Technology 2010, Porto, Portugal,
[6] N. Shigyo et.al., Proc. Int. Conf. on Nucler Data for Science and Technology 2010, will be published.
Flux [1/cm 2 /MeV/source]
10 1
0 5 10 15 20
Energy [MeV]
neutron
photon