Investigating the effect of supports on reinforced concrete slab subjected to oblique missile impact

Kang, Z.; Okuda, Yukihiko; Nishida, Akemi; Tsubota, Haruji; Ito, Masaharu; Li, Y.

Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 9 Pages, 2024/11

https://doi.org/10.1115/ICONE31-135948

Most studies conducted till now on local damage of reinforced concrete (RC) slab structures subjected to missile impact are about normal impact, while few research related to oblique impact can be found. The objective of this study is to carry out impact tests under different impact conditions including oblique impacts, to confirm the different impact behaviors of the RC slab structure, to develop an analysis method by investigating the test results and analytical conditions, and to validate the analysis method through comparison with the test results. This study focuses on the effect of the stiffness of the supports for oblique impact on the reaction forces of RC slab. Until now, static loading tests were conducted to confirm the stiffnesses of the supporting parts that supported the RC specimen during oblique impact tests. Based on the obtained load-displacement relationships, and so on, the stiffnesses of the supporting parts are estimated.

Study on heat transfer behavior of a rectangular particle bed with volumetric heating

Wen, J.*; Kamada, Yuto*; Yokoyama, Kosei*; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*; Imaizumi, Yuya; Tagami, Hirotaka; Matsuba, Kenichi; Kamiyama, Kenji

Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 8 Pages, 2024/11

https://doi.org/10.1115/ICONE31-134313

Droplet evaporation characteristics on high-temperature porous surfaces for cooling fuel debris

Yuki, Kohei*; Horiguchi, Naoki; Yoshida, Hiroyuki; Yuki, Kazuhisa*

Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 4 Pages, 2024/11

https://doi.org/10.1115/ICONE31-135281

Fuel debris in the Fukushima Nuclear Power Station is cooled under immersion condition. However, in the event of an unexpected decrease in water level, coolant contacts high-temperature fuel debris having porous structure. In this event, although fuel debris needs to be cooled rapidly, thermal behavior at liquid-solid contact, such as capillary phenomenon, remains unclear. In this paper, as basic research, we evaluate droplet evaporation characteristics after contact with metal porous media with small pores less than 1 mm. In experiment, to obtain life time curve of a droplet, bronze or stainless steel porous media having 1, 40, or 100 m pore diameter are utilized. Experimental results show that Leidenfrost phenomenon is suppressed on the porous surfaces because generated vapor can be discharged from the pores. Further, for bronze porous media, capillary phenomenon is observed as the temperature of the porous media increase because of generation of oxide film having fine structure. On the other hand, due to low wettability of stainless steel porous media, capillary phenomenon does not occur, and the droplet was not sucked and spread into pore. This indicates that rapid cooling by the capillary phenomenon can not be expected if fuel debris has the same characteristics as the stainless steel porous media.

Study on sodium extraction and transport at Monju

Isobe, Yuta; Tanigaki, Takanori; Tone, Kohei; Joboji, Yuya; Matsui, Kazuaki; Obata, Ikuhito

Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 8 Pages, 2024/11

The prototype fast breeder reactor Monju is a loop-type, sodium-cooled nuclear reactor in Japan. Monju transitioned; to decommissioning in 2018, and the first phase of decommissioning was completed in FY2022 by unloading all the fuel assemblies from the reactor core and Ex-vessel storage tank (EVST) to spent fuel pool. In FY2023, Monju has moved to the second phase of decommissioning, and currently we are working to unload neutron shields and other core elements from the reactor core and EVST to spent fuel pool, and to dismantle water and steam system such as turbine generator, condensers, feed water heaters, etc. Monju has a primary sodium system that cools the reactor core and fuel, and a secondary sodium system that transfers heat. Sodium in the primary system is radioactive, but sodium in the secondary system is non-radioactive. We plan to extract non-radioactive sodium first, so we are first considering this in advance. At present, we have decided on the sodium extraction area where the ISO tank for extraction of non-radioactive sodium will be installed. In addition, we also considered the route for transferring sodium from the existing tanks to the ISO tanks. New piping for these operations will be added, and the sodium will be extracted using existing gas systems and electromagnetic pumps. We will take appropriate measures to sodium leakage and continue to consider safe and rational extraction and transportation methods.

Effects of magnetic ordering on the ground-state energy of plutonium dioxide; A Study using adiabatic connection fluctuation-dissipation theory

Nakamura, Hiroki; Machida, Masahiko

Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 5 Pages, 2024/11

https://doi.org/10.1115/ICONE31-134660

Efficiency and safety improvements in nuclear fuel development demand a comprehensive understanding of the thermal properties of PuO. Because of difficulty of experiments at high temperatures, they have been supplemented by numerical simulations, such as density functional theory (DFT). While DFT struggles to replicate the nonmagnetic insulating ground state of PuO, DFT+U can reproduce nonmagnetic insulating state. However, the obtained state remains less stable than magnetic states and is not the ground state. Adiabatic connection fluctuation-dissipation theory (ACFDT) is expected to be a promising solution, addressing higher-order correlations and exact exchange energies. In this study, we evaluate the ground state energy using ACFDT and find that the nonmagnetic state can be the ground state. This result successfully reproduces the observed nonmagnetic ground state of PuO and has the potential to improve predictions of the thermal properties of nuclear fuel materials.

A Study on analysis of actual data in "Fugen" decommissioning

Koda, Yuya; Nakamura, Yasuyuki; Iguchi, Yukihiro*; Yanagihara, Satoshi*

Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 10 Pages, 2024/11

https://doi.org/10.1115/ICONE31-135953

"Fugen" has been proceeding with decommissioning work since receiving approval for the decommissioning plan in 2008, and is currently in the second step of dismantling the reactor peripheral equipment. In decommissioning, project management is important to select strategies and optimize processes, waste, safety, costs, etc. In Japan, it is expected that decommissioning work for nuclear facilities will become more serious in the future, and the knowledge and project management data obtained from the decommissioning work carried out at "Fugen" to date will be useful for planning. Since the dismantling and removal of the main turbine equipment and the peripheral equipment in preparation for the reactors have been completed so far, the actual data has been organized and analyzed and compiled into unit work coefficients. The project management data, collected during the decommissioning work carried out at "Fugen" is organized and calculated as a unit work coefficient.

Experimental study on the coolability of molten core materials discharged into a depth- and volume-limited sodium plenum

Matsuba, Kenichi; Kato, Shinya; Kamiyama, Kenji; Akaev, A. S.*; Vurim, A. D.*; Baklanov, V. V.*

Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 7 Pages, 2024/11

During a severe accident in sodium-cooled fast reactors, molten core materials could be discharged from the core region toward the lower sodium region of the reactor vessel through coolant channels, such as control rod guide tubes. Typical SFRs have a sodium plenum with limited depth and volume, such as the core inlet plenum located under the core region. Therefore, it is important to evaluate the coolability of molten core materials discharged into a depth- and volume-limited sodium plenum. In the present study, to deepen the understanding on the coolability of molten core materials discharged into such a sodium plenum, conditions under which molten core materials form solidified fragments were discussed based on an experiment discharging a molten fuel simulant (molten Al2O3) into a test vessel filled with liquid sodium.