Applicability confirmation experiment of DDSI method for quantification of plutonium in fuel debris

Mitsuboshi, Natsumi; Nagatani, Taketeru; Kosuge, Yoshihiro*; Suzuki, Risa; Okada, Toyofumi

Dai-44-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 4 Pages, 2023/11

This paper reports the applicability confirmation experiment of DDSI method for quantification of plutonium in fuel debris. We conducted passive neutron measurement for the samples which consist of un-irradiated MOX sample, Cf-252 neutron source, and B-10 neutron absorber to simulate the fuel debris. It was revealed that DDSI method has enough capability to evaluate the leakage multiplication of the sample with unknown amounts of fissile material and neutron absorbers.

Development of a method for the determination of plutonium in fuel debris by dual times neutron measurements

Nagatani, Taketeru; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Nakaguki, Sho; Nomi, Takayoshi; Okumura, Keisuke

Dai-43-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 3 Pages, 2022/11

Preliminary measurement of prompt gamma-ray from nuclear material for the classification of fuel debris and waste

Shiba, Tomooki; Kaburagi, Masaaki; Nomi, Takayoshi; Suzuki, Risa; Kosuge, Yoshihiro*; Nauchi, Yasushi*; Takada, Akira*; Nagatani, Taketeru; Okumura, Keisuke

Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 3 Pages, 2022/10

Characterization study of four candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station (Interim report)

Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Maeda, Makoto; Nauchi, Yasushi*; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Kureta, Masatoshi; Tomikawa, Hirofumi; Okumura, Keisuke; et al.

Proceedings of INMM 57th Annual Meeting (Internet), 10 Pages, 2016/07

Experimental studies of passive neutron measurement for fuel debris at Fukushima Daiichi Nuclear Power Plants

Nagatani, Taketeru; Shirato, Atsuhiko*; Kosuge, Yoshihiro*; Sato, Takashi*; Kawakubo, Yoko; Shiromo, Hideo; Asano, Takashi

Proceedings of INMM 56th Annual Meeting (Internet), 10 Pages, 2015/07

As one of the candidate material accountancy technologies for the fuel debris at Fukushima Daiichi Nuclear Power Plants (1F), we propose the application of a passive neutron technique. The applicability of the new concept to the fuel debris at 1F was evaluated by simulation and the results were presented at the last INMM annual meeting. As the next phase, we conducted experimental tests to confirm the validity of the simulation results. Because actual fuel debris or irradiated fuel cannot be handled at our facility due to a licensing limitation, un-irradiated MOX samples, neutron absorbers and Cf-252 sources were utilized as the best available material to imitate the property of the fuel debris and various configurations were measured using an Epithermal Neutron Multiplicity Counter. The fissile mass in the samples, neutron absorber mass surrounding the samples and intensity of Cf-252 source were varied to confirm the correlation between DDSI response and the leakage multiplication. Test results agreed well with the trend of the simulation results. This indicates that DDSI has sufficient capability to evaluate the leakage multiplication of a sample which includes an unknown amount of fissile material and neutron absorber such as the fuel debris at 1F. This paper provides experimental studies of passive neutron measurement based on the combination of DDSI technique and coincidence counting for fuel debris at 1F.

Monte Carlo N-Particle eXtended (MCNPX) simulation for passive neutron measurement of fuel debris at Fukushima Daiichi Nuclear Power Plants

Nagatani, Taketeru; Nakajima, Shinji; Kosuge, Yoshihiro*; Shiromo, Hideo; Asano, Takashi

Proceedings of INMM 55th Annual Meeting (Internet), 10 Pages, 2014/07

Meltdown of the reactor cores of Units 1-3 occurred at Fukushima Daiichi Nuclear Power Plants (1F). Fuel debris at 1F contains minor actinides and fission products and neutron absorber. These materials make it difficult to quantify fertile nuclear materials in fuel debris by the conventional passive neutron technique. We consider that DDSI and PNAR which focused on fissile material are promising techniques to quantify the nuclear materials in the fuel debris. A concept of application of these techniques to fuel debris measurement was investigated and presented at the last INMM annual meeting. In order to evaluate the applicability of these techniques to fuel debris measurement, we investigated the neutron behavior in the fuel debris by using MCNPX simulation code. Because property of fuel debris is not clear, source term data used were prepared by referring TMI data. This paper provides results of MCNPX simulation for fuel debris measurement at 1F with passive neutron techniques.

Improvement of diffraction efficiency of dielectric transmission gratings using anti-reflection coatings

Nagashima, Keisuke; Kosuge, Atsushi; Ochi, Yoshihiro; Tanaka, Momoko

Optics Express (Internet), 21(16), p.18640 - 18645, 2013/07

https://doi.org/10.1364/OE.21.018640

A novel method for increasing diffraction efficiency of transmission gratings is proposed. In this method, dielectric multilayers are inserted between a grating region and a substrate. These multilayers work as an anti-reflection coating for the transmission grating. It is presented that a grating with 1740 grooves/mm has the diffraction efficiency over 99% using this anti-reflection coating.

Development of a high-contrast, high beam-quality, high-intensity laser

Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki*; Shimomura, Takuya; Sasao, Hajime*; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Kondo, Shuji; Kanazawa, Shuhei; et al.

Reza Kenkyu, 38(9), p.669 - 675, 2010/09

https://ci.nii.ac.jp/naid/10026690779

This paper reviews the temporal contrast and spatial beam quality improvement techniques in a high intensity Ti:sapphire laser system that is based on chirped-pulse amplification (CPA). We describe a low gain optical parametric chirped-pulse amplification (OPCPA) preamplifier that uses high energy, clean pulse seeding and is shown to significantly improve the contrast to better than 10-10 relative to the peak of the main femtosecond pulse. We also report the use of a diffractive optical element for beam homogenization of a 100 J level Nd:glass green pump laser, achieving a flat-topped spatial profile with a filling factor near 80 %.

Development of high temporal and spatial quality, high intensity laser system

Kiriyama, Hiromitsu; Ochi, Yoshihiro; Mori, Michiaki; Tanaka, Momoko; Okada, Hajime; Kosuge, Atsushi; Yoshida, Fumiko; Shimomura, Takuya; Sasao, Hajime; Nakai, Yoshiki*; et al.

no journal, , 

We describe two specific high intensity laser systems that are being developed in our laboratory for many applications such as high field science and nonlinear optics. We report on an ultra-high intensity petawatt-class Ti:sapphire chirped-pulse amplification laser system that can produce a pulse energy of 18 J with 30 fs pulse duration for studying extremely high intensity laser matter interaction process and a small-scaled Yb:YAG chirped-pulse amplification laser system that can generate a pulse energy of 100 m J of 500 fs pulse duration for compact, high efficiency, high repetition system. We discuss the basic design aspects and present the results from our experimental investigations of these laser systems.

Development of high average power, femtosecond modelocked Yb:YAG laser

Kosuge, Atsushi; Ochi, Yoshihiro; Okada, Hajime; Tanaka, Momoko; Mori, Michiaki; Kiriyama, Hiromitsu; Nagashima, Keisuke

no journal, , 

Femtosecond laser source with high average power are attractive tools for industrial and scientific applications and its research and development are done all over the world. The thin disk laser which has a very thin disk gain medium solves the thermal problems occurring in conventional high power rod and slab lasers. In this presentation, we developed a high average power diode-pumped Yb:YAG thin disk oscillator. The thickness of the thin disk gain medium is 200 micrometers and it is mounted directly onto a heat sink and used in reflection. The heat flow is mainly one dimensional towards the heat sink, which significantly reduces thermal problems. We demonstrated the passively mode locked thin disk Yb:YAG laser using a saturable absorber mirror (SESAM) and a second harmonic nonlinear mirror (NLM) technique with a LBO crystal.