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Development of Non-Destructive Methods Adapted forIntegrity Test of Next Generation Nuclear Fuels at KURRI-LINAC

Y. Takahashi, J. Hori, T. Sano, D. Ito, H, Unesaki,
K. Nakajima and Y. Kiyanagi1
Research Reactor Institute, Kyoto University
1

Nagoya University

RESULTS: The measured TOF spectrum using 10B anddummy samples is shown in Fig. 2. The horizontal axis isneutron energy and the vertical axis is neutron flux per
unit of time, unit of area and unit of average beam current.
The values over 10 eV are distorted by the gamma flasheffect from the neutron source. It was found that thegamma shield to reduce the effect is important for themeasurement of epi-thermal neutrons. From the results
under 10 eV region, the neutron flux was 1.9 × 102[n/cm2/s] per 1 mA in average beam current. Note that thevalue of the neutron flux is slightly overestimated because the detection efficiency for 662 keV gamma-rays
from 137Cs standard source was used instead of that for
448 keV from 10B capture gamma-rays. In the case of themaximum power of KURRI-LINAC which is 6 kW, it
was found the maximum neutron flux can be obtained 3.8
× 104 [n/cm2/s] at 12 m beam line with the present neutron source system.
Neutron intensity (n/energy bin/cm2/s/mA)

INTRODUCTION: Fast reactor system with transuranium (TRU) fuels containing minor-actinides (MAs) is
one of attractive options for the incineration of high-level
radioactive wastes. In order to develop the integrity
evaluation methods of the fuels for safety operation of thefast reactor system, the N-DeMAIN (Development ofNon-destructive Methods Adapted for Integrity Test of
Next Generation Nuclear Fuels) project has been started
from 2014. In the project, the identification and quantification of nuclide in the fuels will be conducted by theneutron resonance transmission analysis (NRTA). Moreover, the determination of temperature distribution in thefuels based on the Doppler-broadening and neutron imaging are planned. KURRI-LINAC is used for the project
because it is the only pulsed neutron facility where nuclear materials can be utilized in Japan. To achieve these
purposes, The KURRI-LINAC neutron source should beimproved and modified for the high quality neutron beam
regarding neutron flux, time resolution and spatial resolution. Based on numerical analyses, the neutron source
system, especially moderator, reflector and collimator,
was newly designed and it was installed at KURRI-LINAC as shown in Fig.1. Then, the characteristic of
the neutron source system was investigated.

covered by lead (50mm thick) for reducig backgroundgamma-rays. The operating conditions of the accelerator
were as follows: average beam current was 16.3 mA, frequency was 50 Hz and pulse width was 100 ns. The polyethylene was used as a moderator and its size was 15 cm
square and 5 cm thick which was designed to increase theepi-thermal neutron flux. The collimator in the beam line
was arranged in tapered shape using several polyethylene
tubes containing boron which have 5, 10 and 15 cm hole,respectively. The size of outlet side of the neutron beamis 5 cm in diameter.

Fig.1 New neutron source installed in KURRI-LINAC

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Neutron spectrum

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Neutron energy ( eV )Fig.2 The result of TOF spectrum
EXPERIMENTS: Neutron spectrum was obtained bythe Time-of-flight (TOF) method at 12 m beam line atKURRI-LINAC where the capture gamma-rays from 10B
and dummy samples were measured. The samples wereset at the 135 degree with respect to the incident electron
beam and 12.7 m distance from the target. Two BGO
scintillators (2 in. diam. × 2 in. length) were used formeasuring capture gamma-rays and arranged at 80 mmfrom the samples. The effective area of the detectors was

ACKNOWLEDGEMENT: The authors would like tothank Ms. Harada of Nagoya University for her contribution of the numerical analysis and valuable discussion.
Present study includes the result of “Development of
Non-Destructive Methods Adapted for Integrity test ofNext generation nuclear fuels” entrusted to the Kyoto
University by the Ministry of Education, Culture, Sports,
Science and Technology of Japan (MEXT).

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