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Nakashio, Nobuyuki*; Osugi, Takeshi; Kurosawa, Shigenobu; Ishikawa, Joji; Hemmi, Ko; Iketani, Shotaro; Yokobori, Tomohiko
JAEA-Technology 2022-016, 47 Pages, 2022/08
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.
Maruyama, Shuhei
Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) (Internet), 10 Pages, 2022/05
This paper proposes a new homogenization method, "Boundary Condition Free Homogenization (BCFH)". The traditional homogenization method separates the core calculation and the cell (assembly) calculation by assuming a specific boundary condition or a peripheral region in the cell calculation. Nevertheless, there are ambiguities and approximation in these assumptions, and they can also cause a decline in accuracy. BCFH aims to avoid these problems and improve the accuracy in the cell calculation such as homogenization. We imposed the conditions that the physical quantities in the cell related to the reaction rate preservation is preserved for any incoming partial current, during the homogenization. That is, the response matrices of cell average (or total) flux and outgoing partial current, to be the same form between heterogeneous and homogeneous system. As a result, homogenized parameters, such as cross-sections, superhomgenization factors, and discontinuity factors, are no longer dependent on a specific boundary condition. The new homogenized parameters obtained in this way are extended from the conventional vector form to the matrix form in BCFH. To investigate the performance of BCFH, numerical tests are done for the simplified models which originates in 750MW-class sodium-cooled fast reactor with MOX fuel core in Japan. It is found that BCFH is particularly effective in evaluating control rod reactivity worth and reaction rate distribution, compared to the traditional method. We conclude that the BCFH can be a promising homogenization concept for core neutronic analysis.
Takino, Kazuo; Sugino, Kazuteru; Oki, Shigeo
Annals of Nuclear Energy, 162, p.108454_1 - 108454_7, 2021/11
Times Cited Count:1 Percentile:10.00(Nuclear Science & Technology)Higuchi, Hidekazu; Momma, Toshiyuki; Nakashio, Nobuyuki; Kozawa, Kazushige; Tohei, Toshio; Sudo, Tomoyuki; Mitsuda, Motoyuki; Kurosawa, Shigenobu; Hemmi, Ko; Ishikawa, Joji; et al.
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10
The JAERI constructed the Advanced Volume Reduction Facilities(AVRF). The AVRF consists of the Waste Size Reduction and Storage Facilities(WSRSF) and the Waste Volume Reduction Facilities(WVRF). By operating the AVRF, it will be able to produce waste packages for final disposal and to reduce the amount of the low level solid wastes. Cutting installations for large wastes such as tanks in the WSRSF have been operating since June 1999. The wastes treated so far amount to 600 m and the volume reduction ratio is around 1/3. The waste volume reduction is carried out by a high-compaction process or melting processes in the WVRF. The metal wastes from research reactors are treated by the high-compaction process. The other wastes are treated by the melting processes that enable to estimate radioactivity levels easily by homogenization and get chemical and physical stability. The WVRF have been operating with non-radioactive wastes since February 2003 for the training and the homogeneity investigation in the melting processes. The operation with radioactive wastes will start in FY2005.
Oigawa, Hiroyuki; Osugi, Toshitaka; Ono, Akio; ;
JAERI-M 91-096, 39 Pages, 1991/06
no abstracts in English
Nakagawa, Masayuki;
JAERI 1294, 82 Pages, 1984/12
no abstracts in English