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Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*
JAEA-Review 2024-012, 122 Pages, 2024/09
JAEA-Review-2024-012.pdf:6.31MB
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 FY2022. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station (hereafter referred to "1F"), 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 FY2021, this report summarizes the research results of the "Challenge of novel hybrid-waste-solidification of mobile nuclei generated in Fukushima Nuclear Power Station and establishment of rational disposal concept and its safety assessment" conducted in FY2022. The present study aims to establish the rational waste disposal concept of a variety of wastes generated in 1F based on the hybrid-waste-solidification by the Hot Isostatic Press (HIP) method. The ceramics form with target elements, mainly iodine, which is difficult to immobilize, and Minor actinides such as Am, an alphaemitter and heat source, are HIPed with well-studied materials such as SUS and zircaloy, which make the long-term stability evaluation and safety assessment possible.
Nakashio, Nobuyuki*; Osugi, Takeshi; Kurosawa, Shigenobu; Ishikawa, Joji; Hemmi, Ko; Iketani, Shotaro; Yokobori, Tomohiko
JAEA-Technology 2022-016, 47 Pages, 2022/08
JAEA-Technology-2022-016.pdf:2.23MB
The Nuclear Science Research Institute (NSRI) of the Japan Atomic Energy Agency (JAEA) started operation of the Advanced Volume Reduction Facilities (AVWF) for production of waste packages for disposal of low-level radioactive solid wastes (LLW). To clarify the operating conditions for homogenization of non-metallic LLW, preliminary tests were carried out using the plasma melting furnace of the non-metal melting unit. The fluidity of molten waste influences homogenization conditions of solidified products. It was clarified that the viscosity, which is determined by the chemical composition and the melting temperature, influence the fluidity of molten waste greatly through previous literature review and the small-scale melting tests. In the preliminary tests, the simulated waste with a cold tracer loaded in 200 L drums were melted. Using the waste chemical components (basicity, iron oxide concentration) as an experimental parameter, the homogeneity of the chemical components of the solidified product was investigated and the homogenization conditions of melting tests were examined. The retention ratio of the tracer in the molten bath was also confirmed. The viscosity of the molten wastes was measured and the correlation with homogeneity was examined. In addition, the technical requirements that should be concerned in advance for future actual operation were discussed.
Nakanishi, Ryuzo; Oba, Hironori; Saeki, Morihisa; Wakaida, Ikuo; Tanabe, Rie*; Ito, Yoshiro*
Optics Express (Internet), 29(4), p.5205 - 5212, 2021/02
Times Cited Count：22 Percentile：87.40(Optics)Laser-induced breakdown spectroscopy (LIBS) combined with liquid jets was applied to the detection of trace sodium (Na) in aqueous solutions. The sensitivities of two types of liquid jets were compared: a liquid cylindrical jet with a diameter of 500 
m and a liquid sheet jet with a thickness of 20 m. Compared with the cylindrical jet, the liquid sheet jet effectively reduced the splash from the laser-irradiated surface and produced long-lived luminous plasma. The limit of detection (LOD) of Na was determined to be 0.57 g/L for the sheet jet and 10.5 g/L for the cylindrical jet. The LOD obtained for the sheet jet was comparable to those obtained for commercially available inductively coupled plasma emission spectrometers.
Takizuka, Tomonori; Hosokawa, Masanari*
Contributions to Plasma Physics, 46(7-9), p.698 - 703, 2006/09
Times Cited Count：16 Percentile：44.90(Physics, Fluids & Plasmas)Enhanced heat and particle fluxes to the divertor plates after an ELM crash in H-mode plasmas are the crucial issues for the tokamak reactor operation. Kinetic effect in the transient behaviour of SOL-divertor plasmas for this case is not yet well known. We investigate above problems with an advanced particle simulation code, PARASOL. Dependence of the particle and heat propagations on the collisionality is studied systematically. Effect of the particle recycling is also studied.
Kawashima, Hisato; Sengoku, Seio; Uehara, Kazuya; Tamai, Hiroshi; Shoji, Teruaki*; Ogawa, Hiroaki; Shibata, Takatoshi; Yamamoto, Masahiro*; Miura, Yukitoshi; Kusama, Yoshinori; et al.
Fusion Science and Technology, 49(2), p.168 - 186, 2006/02
Times Cited Count：3 Percentile：23.63(Nuclear Science & Technology)Experimental efforts on JFT-2M have been devoted to understand SOL/Divertor plasmas and to investigate power and particle controllability. Open divertor configuration was used for the first decade of JFT-2M started in 1984. We found out the SOL/Divertor plasma properties such as in/out asymmetry, heat and particle diffusivities, and SOL current at ELMs. Handling of power and particle was demonstrated by active control methods such as local pumping, edge ergodization, divertor biasing, and edge heating. For improvement of power and particle control capability of divertor, it was modified to closed configuration in 1995, which demonstrated the baffling effects with narrower divertor throat. Dense and cold divertor state (n
= 4
10
m
and T = 4 eV), compatible with the improved confinement modes (e.g. H-mode), was realized by strong gas puffing. Being related with the core confinement at H-mode, the edge plasma fluctuations were identified by an electrostatic probe. These are reviewed in this paper.
Haraga, Tomoko; Kameo, Yutaka; Nakashima, Mikio
Bunseki Kagaku, 55(1), p.51 - 54, 2006/01
Times Cited Count：4 Percentile：14.14(Chemistry, Analytical)A relatively large quantity of sample solutions have to be prepared for radiochemical analysis of solidified products yielded by plasma melting treatment of non-metallic radioactive wastes. In order to dissolve the solidified products sample rapidly, dissolution method with microwave heating devices was applied. In a conventional method only by external heating with various mixtures of acids (HNO
, HF, HClO
and H
SO), a 0.1 g amount of the sample was dissolved with difficulty. However, applying the microwave assisted dissolution method, a 1 g amount of the sample was completely dissolved in a shorter time. Thereby the time for dissolution procedures was shortened less than a one-tenth. The present dissolution method was successfully applied to the blast furnace slag as a reference material to determine main elements with good precision.
Kubo, Hirotaka; JT-60 Team
Plasma Science and Technology, 8(1), p.50 - 54, 2006/01
Times Cited Count：2 Percentile：6.80(Physics, Fluids & Plasmas)no abstracts in English
-ray spectrometry for the rapid radioactivity evaluation of solidified products prepared from radioactive wastesHaraga, Tomoko; Kameo, Yutaka; Hoshi, Akiko; Yonezawa, Chushiro*; Nakashima, Mikio
JAERI-Tech 2005-050, 35 Pages, 2005/09
JAERI-Tech-2005-050.pdf:1.35MB
Non-destructive -ray spectrometry has been examined as a simple and rapid radioactivity measurement technique for the solidified products prepared by plasma melting for low level radioactive miscellaneous wastes generated from nuclear facilities. The Compton background resulting from the coexisting radionuclides pose a problem in the usual -ray spectrometry which uses only a Ge detector. In order to reduce the background count and to measure the interested nuclide selectively, the coincidence and the anti-coincidence -ray spectrometry using the Ge-BGO detector system were examined. As a result of applying the anti-coincidence -ray spectrometry to a single -ray emitter 
Cs and the coincidence -ray spectrometry to multiple -ray emitter 
Eu under existence of 
Co, the detection limits of Cs and Eu in the sample, which contained Co, were reduced by a factor of about 6 and 1.5, respectively. It was confirmed that the present methods are useful for the -activity measurement of solidified products.
Asakura, Nobuyuki
Purazuma, Kaku Yugo Gakkai-Shi, 80(3), p.190 - 200, 2004/03
Understanding of the divertor and Scrape-off Layer (SOL) plasmas has been progressed during improvements of the compact- and closed-geometry tokamak divertors. Developments of new diagnostics viewing the SOL and upstream of the divertor target (with the finest spatial and/or time resolutions) have contributed to understand the physics mechanisms under large variations of the plasma along and perpendicular to the field lines. Four topics: (i) heat and particle transports upstream of the divertor plate, (ii) burst transport of heat and particles towards the divertor, (iii) SOL plasma flow, and (iv) plasma diffusion in SOL, were reviewed.
Takizuka, Tomonori; Hosokawa, Masanari*; Shimizu, Katsuhiro
Journal of Nuclear Materials, 313-316(1-3), p.1331 - 1334, 2003/03
Times Cited Count：15 Percentile：68.14(Materials Science, Multidisciplinary)In course of tokamak fusion research, particle and heat control is one of the most crucial issues. Helium ash exhaust and impurity retention in the divertor region owe to the plasma flow towards divertor plate. The localization of heat load on the plate depends on the flow pattern. Accordingly, particle and heat control can be achieved by the proper control of the flow in SOL and divertor plasmas. In this paper, the flow control is studied with two-dimensional particle simulations by PARASOL (PARticle Advanced simulation for SOL and divertor plasmas) code. Magnetic field configuration with separatrix like a tokamak divertor configuration is given. Hot particle source is put in the core plasma. Recycling cold particle source is located near the divertor plate. Particle source of gas puff in the SOL plasma is given for the flow control. Divertor biasing is available by changing the electrostatic potential on the plates. Effects of gas puff and biasing on the flow are studied. Controllability is evaluated from simulation results.
Ogawa, Hiroaki*; Kiuchi, Kiyoshi
JAERI-Research 2002-037, 48 Pages, 2002/12
JAERI-Research-2002-037.pdf:2.57MB
The difference in hydrogen permeation among candidate cladding materials such as 25Cr-35Ni stainless steel, Nb liner and reference materials such as 18Cr-8Ni SS, and Zr of Zircaloy base metal were evaluated by low energy plasma permeation simulated to hydrogen excited by heavy neutron irradiation. RF excitation source was arranged for the experimental apparatus in cooperating with temperature and bias control. Comparing with the thermodynamic gas driven permeation (GDP) in the same hydrogen pressure, the hydrogen permeation rate by the plasma driven permeation (PDP) was markedly accelerated at low to medium temperature range. The temperature dependency showed a knick at around 530K due to hydrogen-defect interactions. Comparing with Zr, Nb showed the high hydrogen solubility without the degradation by hydrate formation that is required to a getter material. The difference in PDP among candidates was analyzed with a new dissolution model for hydrogen.
Takizuka, Tomonori; Hojo, Hitoshi*; Hatori, Tadatsugu*
Purazuma, Kaku Yugo Gakkai-Shi, 78(9), p.857 - 912, 2002/09
Transport along field lines in magnetic confinement plasmas is reviewed. Collisionless and collisional-diffusive transports are discussed. Because of their fast transport, features of plasmas along field lines are apt to behave nonlocally. A nonlocal phenomenon of scrape-off layer (SOL) and divertor plasmas in a tokamak is introduced, whose asymmetry along field lines is induced by the thermoelectric instability related to the SOL current. A local phenomenon called MARFE can be brought by the strong radiation cooling. The "snake" with nonlocal feature along field lines but with local structure perpendicular to the field is observed in a tokamak core plasma. For mirror-confined plasmas, axial particle losses from the mirror ends, especially pitch-angle-sattering losses into the loss cone and nondiabatic losses due to the breakdown of adiabaticity of the magnetic moment, are also discussed in the relation to nonlocal axial transport.
; Takizuka, Tomonori; Hatayama, Akiyoshi*;
Journal of Nuclear Materials, 266-269, p.526 - 531, 1999/00
Times Cited Count：4 Percentile：34.39(Materials Science, Multidisciplinary)no abstracts in English
;
Therm. Sci. Eng., 7(1), p.21 - 30, 1999/00
no abstracts in English
; Takizuka, Tomonori; Hatayama, Akiyoshi*;
Journal of the Physical Society of Japan, 66(12), p.3815 - 3825, 1997/12
Times Cited Count：5 Percentile：47.26(Physics, Multidisciplinary)no abstracts in English
Yoda, Osamu; Miyashita, Atsumi; ; ; ;
Japanese Journal of Applied Physics, 32(SUPPL.32-2), p.255 - 257, 1993/00
no abstracts in English
Yoda, Osamu; Miyashita, Atsumi; ;
JAERI-M 92-173, 27 Pages, 1992/10
no abstracts in English
Takeda, Tatsuoki; Tani, Keiji; Tsunematsu, Toshihide; Kishimoto, Yasuaki; ; ;
Parallel Computing, 18, p.743 - 765, 1992/00
Times Cited Count：2 Percentile：47.40(Computer Science, Theory & Methods)no abstracts in English
Nishitani, Takeo; Takeuchi, Hiroshi; Barnes, C. W.*; Iguchi, Tetsuo*; Nagashima, Akira; Kondoh, Takashi; Sakasai, Akira; Itami, Kiyoshi; Tobita, Kenji; Nagashima, Keisuke; et al.
JAERI-M 91-176, 23 Pages, 1991/10
no abstracts in English
Yoda, Osamu; Miyashita, Atsumi; ; ;
Excimer Lasers and Applications III, p.463 - 466, 1991/00
no abstracts in English
