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Mizukoshi, Tomoaki,Watanabe, Kenichi,Yamazaki, Atsushi,Uritan, Akira,Iguchi, Tetsuo,Ogata, Tomohiro,Muramatsu, Takashi The Korean Association for Radiation Protection 2016 방사선방어학회지 Vol.41 No.3
Background: In order to measure neutron energy spectra, the conventional Bonner Sphere Spectrometers (BSS) are widely used. In this spectrometer, several measurements with different size Bonner spheres are required. Operators should, therefore, place these spheres in several times to a measurement point where radiation dose might be relatively high. In order to reduce this effort, novel neutron energy spectrometer using an onion-like single Bonner sphere was proposed in our group. This Bonner sphere has multiple sensitive spherical shell layers in the single sphere. In this spectrometer, a band-shaped thermal neutron detection medium, which consists of a LiF-ZnS mixed powder scintillator sheet and a wavelength-shifting (WLS) fiber readout, was looped to each sphere at equal angular intervals. Amount of LiF neutron converter is reduced near polar region, where the band-shaped detectors are concentrated, in order to uniform the directional sensitivity. The LiF-ZnS mixed powder has an advantage of extremely high light yield. However, since it is opaque, scintillation photons cannot be collect uniformly. This type of detector shows no characteristic shape in the pulse height spectrum. Subsequently, it is difficult to set the pulse height discrimination level. This issue causes sensitivity fluctuation due to gain instability of photodetectors and/or electric modules. Materials and Methods: In order to solve this problem, we propose to replace the LiF-ZnS mixed powder into a flexible and Transparent RUbber SheeT type $LiCaAlF_6$ (TRUST LiCAF) scintillator. TRUST LiCAF scintillator can show a peak shape corresponding to neutron absorption events in the pulse height spectrum. Results and Discussion: We fabricated the prototype detector with five sensitive layers using TRUST LiCAF scintillator and conducted basic experiments to evaluate the directional uniformity of the sensitivity. Conclusion: The fabricated detector shows excellent directional uniformity of the neutron sensitivity.
Hirata, Yuho,Watanabe, Kenichi,Uritani, Akira,Yamazaki, Atsushi,Koba, Yusuke,Matsufuji, Naruhiro The Korean Association for Radiation Protection 2016 방사선방어학회지 Vol.41 No.3
Background: We are developing a small size dosimeter for dose estimation in particle therapies. The developed dosimeter is an optical fiber based dosimeter mounting an radiation induced luminescence material, such as an OSL or a scintillator, at a tip. These materials generally suffer from the quenching effect under high LET particle irradiation. Materials and Methods: We fabricated two types of the small size dosimeters. They used an OSL material Eu:BaFBr and a BGO scintillator. Carbon ions were irradiated into the fabricated dosimeters at Heavy Ion Medical Accelerator in Chiba (HIMAC). The small size dosimeters were set behind the water equivalent acrylic phantom. Bragg peak was observed by changing the phantom thickness. An ion chamber was also placed near the small size dosimeters as a reference. Results and Discussion: Eu:BaFBr and BGO dosimeters showed a Bragg peak at the same thickness as the ion chamber. Under high LET particle irradiation, the response of the luminescence-based small size dosimeters deteriorated compared with that of the ion chamber due to the quenching effect. We confirmed the luminescence efficiency of Eu:BaFBr and BGO decrease with the LET. The reduction coefficient of luminescence efficiency was different between the BGO and the Eu:BaFBr. The LET can be determined from the luminescence ratio between Eu:BaFBr and BGO, and the dosimeter response can be corrected. Conclusion: We evaluated the LET dependence of the luminescence efficiency of the BGO and Eu:BaFBr as the quenching effect. We propose and discuss the correction of the quenching effect using the signal intensity ratio of the both materials. Although the correction precision is not sufficient, feasibility of the proposed correction method is proved through basic experiments.
Development of Metal Recovery Process for Municipal Incineration Bottom Ash (MIBA)
Kuroki, Ryota,Ohya, Hitoshi,Ishida, Kazumasa,Yamazaki, Kenichi The Korean Institute of Resources Recycling 2019 資源 리싸이클링 Vol.28 No.3
The utilization of incineration ash from municipal waste must be promoted to solve the social problem on the shortage of final disposal site. In this research, metals should be recovered to avoid the damage of the crushing machine during the utilization of incineration ash in cement industry. In fact, incineration bottom ash from municipal waste contains iron in 3-5%. Nonferrous metal and stainless steel in 1% is also included. The research and development on the physical recovery process was performed not only to remove the metals but also to recover high grade products. Metals were separated from incineration ash in Maruya Co. Ltd.. In fact, iron scrap recovered by magnetic separation can be selled. After that, mixed metal was separated from incineration ash using screen. In this research, mixed metal tried to divided copper, aluminum, brass and stainless steel using drum type magnetic separation, eddy current separation and high magnetic separation. As a result, recovered iron had an 80% for the grade. Aluminum was recovered by eddy current separation without copper and brass.
Next Generation HVAC System for Office Buildings
Yasuo Takagi,Kenzo Yonezawa,Nobutaka Nishimura,Yuuichi Hanada,Kenichi Yamazaki 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
The new air-conditioning control method for the energy saving of buildings is proposed. The method ismainly focused on the compatibility of energy savings and comfort. The energy saving is achieved through the optimal operation of HVAC (Heating, Ventilating and air-conditioning) system, manipulating the supplying airflow temperatures to the rooms, room temperatures and the humidity. The comfort is kept by the index (PMV: Predicted Mean Vote) that comprises temperature, humidity, radiation temperature, wind velocity and so on. In order to find the HVAC system operation conditions that satisfy the comfort and energy saving at the same time, very large-scale nonlinear programming with nonlinear constraints must be solved on real time basis. To make the programming of the system practical, the driving function loaded onto a control computer is introduced. The function is made by the spline-interpolation to achieve calculation stable and adaptation to various HVAC operation modes.