JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

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Measurement of Neutron Fluence in the Comparison
between TIARA and CYRIC High Energy
Neutron Facilities
T. Matsumoto a) , H. Harano a) , A. Masuda a) , Y. Unno a) , M. Hagiwara b) , T. Sanami b) ,
J. Nishiyama a) , Y. Shikaze c) , Y. Tanimura c) , M. Yoshizawa c) , M. Baba d) and K. Mizuhashi e)
a) National Metrology Institute of Japan, National Institute of Advanced Industrial Science and
Technology, b) High Energy Accelerator Research Organization,
c) Department of Radiation Protection, NSRI, JAEA, d) CYRIC, Tohoku University,
e) Department of Advanced Radiation Technology, TARRI, JAEA
Precise measurement for high energy neutrons is
important in studies on nuclear data, exposure in aircrafts,
neutron induced soft error rate in semiconductor devices and
the neutron dose estimation around large accelerator
facilities such as J-PARC. High energy neutron fields at
cyclotron facility TIARA and CYRIC are promising
candidate for reference fields in order to calibrate
measurement devices. However, each facility has different
characteristics for the neutron field and adopts different
methods for high energy neutron measurements. Therefore,
comparison studies are currently being conducted between
these two facilities.
In TIARA experiments, 45 MeV quasi-monoenergetic
neutrons were produced from the 7 Li(p,n) reaction. The
neutron fluence were measured with several neutron
detectors, 5" × 5" and 3" × 3" NE213 liquid scintillators 1) ,
proton recoil telescope (PRT) 2) and a spherical 3 He
proportional counter with a spherical moderator made of
polyethylene and lead 3) . In the measurements, we used a
transmission type plastic scintillator developed by JAEA as
a neutron monitor. The plastic scintillator was set in the
neutron flight path between the neutron source and the
detector. The results of the detector with the moderator
were extracted from detection efficiency and neutron
spectrum obtained from the TOF measurement with the
NE213. The lower energy limit in neutron spectrum
measured with the TOF method is determined by repetition
rate of the proton beam from the accelerator and the flight
path length. The spectral component below the limit needs
to be given by the extrapolation or another method of
measurement. In the experiments, we obtained the spectral
3
component below the limit with a He loaded
multi-moderator spectrometer (Bonner sphere spectrometer)
that was located 12.9 m away from the neutron source.
The moderators are composed of polyethylene, lead and
copper. Detection efficiency for each moderator of the
spectrometer is obtained from calculation with the MCNPX
simulation code and experimental results measured in
monoenergetic neutron fields with energy range from
100 keV to 15 MeV in AIST. Figure 1 shows low energy
component in the 45-MeV neutron field obtained with the
Bonner sphere spectrometer by means of an unfolding
method. Experimental results for peak neutron fluence in
JAEA-Review 2010-065
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the 45-MeV quasi monoenergetic neutron field obtained
with each detector are given in Table 1. The experimental
results for each detector were normalized with counts
observed with the plastic scintillator. The results are in good
agreement within 10 %.
The low energy component in the quasi monoenergetic
neutron field will be observed with other detectors such as a
sandwich spectrometer. We will also try to derive the
neutron fluence and to investigate the low energy
component for 60 or 75 MeV neutron field. Moreover, the
results for the 45 MeV neutrons will be compared with those
obtained at CYRIC.
References
1) M. Baba et al., Nucl. Instrum. Meth. Phys. Res. A 428
(1999) 454.
2) Y. Shikaze et al., Nucl. Instrum. Meth. Phys. Res. A 615
(2010) 211.
3) B. Wiegel and A. V. Alevra, Nucl. Instrum. Meth. Phys.
Res. A 476 (2002) 36.
Fluence(n/cm 2 /MeV/PL at 12.095 m)
10 0
10 -1
10 -2
10 -3
10
0 10 20 30 40 50
-4
Neutron Energy(MeV)
Fig. 1 Low energy component in the 45-MeV quasi
monoenergetic neutron field measured with the Bonner
sphere spectrometer.
Table 1 Peak neutron fluences (10 6 n/sr/PL) in the 45 MeV
quasi-monoenergetic neutron field derived from the two
3
NE213 detectors, PRT and the spherical He
proportional counter with the moderator made of
polyethylene and lead.
PRT 3" × 3"NE 5" × 5"NE
3 He
2.86 2.93 3.05 3.08