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Collaborative Laboratories for Advanced Decommissioning Science; Nagoya University*
JAEA-Review 2021-033, 55 Pages, 2021/12
JAEA-Review-2021-033.pdf:2.9MB
The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2020. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2019, this report summarizes the research results of the "Measurement methods for the radioactive source distribution inside reactor buildings using a one-dimensional optical fiber radiation sensor" conducted in FY2020. We are developing a one-dimensional optical fiber radiation sensor that can estimate the radioactive source distribution "along lines" instead of "at points". To improve the conventional time-of-flight optical fiber radiation sensor for the application under high dose rate environment, basic evaluation tests were conducted using various optical fibers with different diameters and materials.
Nakamura, Tatsuya; Kawasaki, Takuro; To, Kentaro; Harjo, S.; Sakasai, Kaoru; Aizawa, Kazuya
JPS Conference Proceedings (Internet), 33, p.011097_1 - 011097_6, 2021/03
A large area, two-dimensional scintillation neutron detector was developed for Takumi diffractometer in the J-PARC MLF. The detector is made based on a scintillator/wavelength shifting fiber technology. The detector has a neutron-sensitive area of 32 
32 cm with a pixel size of 5 5 mm, which is about 1.5-fold larger than the SENJU detector TAKUMI is one of the neutron diffractometers in the MLF dedicated to use for engineering material research. The developed detector array adds new capabilities to the instrument to measure two-dimensional data collection at the back-scattering angles with a better time-of-flight resolution.
Collaborative Laboratories for Advanced Decommissioning Science; Nagoya University*
JAEA-Review 2020-063, 44 Pages, 2021/01
JAEA-Review-2020-063.pdf:2.55MB
JAEA/CLADS had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project in FY2019. Among the adopted proposals in FY2019, this report summarizes the research results of the "Measurement methods for the radioactive source distribution inside reactor buildings using a one-dimensional optical fiber radiation sensor" conducted in FY2019.
Nakamura, Tatsuya; To, Kentaro; Ebine, Masumi; Birumachi, Atsushi; Sakasai, Kaoru
Proceedings of 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC 2019), Vol.1, p.735 - 736, 2020/08
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)A large area, position-sensitive scintillation neutron detector was developed for upgrading the SENJU, time-of-flight Laue single crystal neutron diffractometer, in J-PARC MLF. The detector has a neutron-sensitive area of 512 512 mm with a pixel size of 4 4 mm. The detector was developed for upgrading of the SENJU instrument. The large area detector is to be installed below the vacuum tank to enlarge a covering solid angle. A 
Li:ZnS (Ag) scintillator and wavelength-shifting fiber technologies are employed. Each fiber channel is read out individually with photon counting mode. The electronics boards are implemented at the backside of the detector, enabling the detector depth as short as 20 cm. The detector exhibited a detection efficiency of 45% for thermal neutron. No degradation in fiber position and in neutron sensitivity has been observed over one year after production. In this paper, detector design and detector performances are presented.
Nakamura, Tatsuya; To, Kentaro; Tsutsui, Noriaki; Ebine, Masumi; Birumachi, Atsushi; Sakasai, Kaoru
Journal of Instrumentation (Internet), 12(12), p.C12025_1 - C12025_9, 2017/12
Times Cited Count：4 Percentile：18.20(Instruments & Instrumentation)A high-spatial-resolution, large-area position-sensitive scintillation-based neutron detector module has been developed for a new time-of-flight Laue single-crystal diffractometer to be constructed at J-PARC MLF. A first prototype detector implementing commercial Li:ZnS screens was produced based on a scintillator/wavelength-shifting fibre technology. The detector exhibited a spatial resolution of 2.5 mm with a neutron-sensitive area of 320 320 mm
. We report on an initial evaluation of the detector performance, including its spatial resolution, detection efficiency and long-term background measurement, and also provide a brief description of a new neutron instrument.
Tanimura, Yoshihiko; Saegusa, Jun; Yoshizawa, Michio; Yoshida, Makoto
Nuclear Instruments and Methods in Physics Research A, 547(2-3), p.592 - 600, 2005/08
Times Cited Count：11 Percentile：60.71(Instruments & Instrumentation)The moderator structure of a neutron spectrometer was optimized with a Monte Carlo code of MCNP-4B. The spectrometer consists of a cylindrical moderator and a position-sensitive thermal neutron detector. It can obtain an energy spectrum from thermal neutron distribution along the cylindrical axis of the moderator. The structure of the moderator was improved by putting a low hydrogen density material in the front of a high hydrogen density one and inserting a neutron absorber which eliminated thermal neutrons diffusing in the moderator. These improvements make energy resolution of the spectrometer better especially for the low energy neutrons from a few tens to 100 keV. The designed spectrometer can be applied to the measurement of energy spectrum over a neutron energy range from a few keV to 20 MeV.
Nakamura, Tatsuya; To, Kentaro; Kawasaki, Takuro; Kiyanagi, Ryoji; Ohara, Takashi; Koizumi, Tomokatsu; Ebine, Masumi; Sakasai, Kaoru
no journal, ,
Position-sensitive scintillation neutron detectors developed using wavelength-shifting (WLS) fiber read out in the Materials and Life Science Experimental Facility of the Japanese Proton Accelerator Research Complex (J-PARC MLF) are briefly reviewed. Several tens of two-dimensional scintillator / WLS fiber detectors have been developed for the single crystal diffractometers. They are implemented to the beam lines of BL03 and BL18. The scintillator / WLS fiber read out technology has many advantages over conventional clear fiber coupled detectors, such as its simple detector structure, flexibility to a pixel size design, and manufacturing cost. In this paper, several examples of the WLS fiber detectors developed at J-PARC MLF are presented together with a recent detector development for the additional detector bank of the BL18. Moreover, a possibility to produce a larger area detector with this technology will be discussed.
Nakamura, Tatsuya; To, Kentaro; Kiyanagi, Ryoji; Ohara, Takashi; Hosoya, Takaaki; Sakasai, Kaoru
no journal, ,
Detector performances of large area two-dimensional neutron detectors produced for upgrade of SENJU diffractometer at Materials and Life science experimental Facility at J-PARC have been evaluated. The detectors are developed based on a Li:ZnS(Ag) scintillator and wavelength-shifting fiber technology. The prototype detector has a neutron-sensitive area of 512 768 mm, which is six-fold of the original detector installed in the SENJU. The prototype detector exhibited a detection efficiency of 40-50% for 2-
space neutrons and 
Co gamma-ray sensitivity of ~10
. 9 detector modules have been produced for the planned SENJU upgrade. The produced detectors exhibited similar detector efficiencies and gamma-ray sensitivities to that of the prototype detector. Neutron counts of these detectors with a 
Cf source varied within 5% to the average. The experimental results of the prototype and the produced beamline detectors are presented.
