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Kirishima, Akira*; Akiyama, Daisuke*; Sato, Nobuaki*; Sasaki, Takayuki*; Watanabe, Masayuki; Kumagai, Yuta; Kusaka, Ryoji
no journal, ,
In the 1F accident, it seems that the structural material and molten fuel react at high temperature to form fuel debris containing an alloy phase. In this study, simulated debris of such a system is synthesized, and structural evaluation, state analysis, and nuclide immersion test are conducted to evaluate its stability. In this presentation, the outline of the research project and the synthesis of simulated debris are reported.
-SS systemAkiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Sasaki, Takayuki*; Watanabe, Masayuki; Kumagai, Yuta; Kusaka, Ryoji
no journal, ,
Fuel debris is expected to be generated by pyrochemical reactions between the molten fuel and the reactor structural materials during the course of the 1F severe accident. For the retrieval of the fuel debris as well as the treatment and the disposal, estimating the debris characteristics is indispensable. Hence, we have synthesized simulated fuel debris form UO and stainless steel (SS) and analyzed the structure of the simulated fuel debris by XRD and SEM-EDX. In the UO-SS system, the simulated fuel debris synthesized under oxidative conditions contained uranium-iron multiple oxide in addition to simple oxides of uranium and iron. However, the formation of uranium-iron multiple oxide was not observed in the UO-Fe system. On the other hand, we found the formation of uranium-chromium multiple oxide in the simulated fuel debris prepared from UO and metal chromium. These results indicate that the multiple oxides are formed only in the presence of chromium.
-SS system; Irradiation or addition methodSasaki, Takayuki*; Kodama, Yuji*; Kobayashi, Taishi*; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Watanabe, Masayuki; Kumagai, Yuta; Kusaka, Ryoji
no journal, ,
Fuel debris generated in the 1F severe accident remains in direct contact with water and leaching of nuclides from the debris is anticipated to continue. Therefore, in order to comprehend the leaching behavior, we have investigated the leaching of fission-product (FP) elements. We employed two methods for the synthesis of simulated fuel debris containing FP elements, that is (1) irradiation method: generating radioactive FPs in the simulated debris by irradiation of thermal neutron and (2) addition method: adding stable isotopes of FP elements into the starting materials of the simulated debris. In the early stage of leaching to water, Cs dissolved from these simulated debris ahead of U. But Cs/U ratio in water decreased with time, suggesting that water-soluble elements at the surface promptly dissolved. Divalent elements, Ba and Sr, dissolved similarly to Cs, whereas the leaching of Nd and Eu proceeded concomitantly with the U dissolution.
-Zr-SS systemAkiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Sasaki, Takayuki*; Watanabe, Masayuki; Kumagai, Yuta; Kusaka, Ryoji
no journal, ,
The melted nuclear fuel on the 1F accident, reacted with structural materials. It is believed that the reacted nuclear fuel transformed to fuel debris including alloy phases. Therefore, it is important for the removal, the treatment and the disposal of fuel debris to predict the properties of their chemical stabilities. In this study, we synthesized simulated fuel debris including Zr and elements in stainless steel, analyzed structure and component by XRD and SEM-EDX, and evaluated dependency of heating temperature, heating period and atmospheric condition.
-SS systemSasaki, Takayuki*; Kodama, Yuji*; Tonna, Ryutaro*; Kobayashi, Taishi*; Kumagai, Yuta; Kusaka, Ryoji; Watanabe, Masayuki; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; et al.
no journal, ,
no abstracts in English
-Zr-SS system; Irradiation or addition methodSasaki, Takayuki*; Tonna, Ryutaro*; Kobayashi, Taishi*; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Watanabe, Masayuki; Kumagai, Yuta; Kusaka, Ryoji
no journal, ,
We synthesized simulated fuel debris which containing stainless steel and zirconium. The fission of Uranium by the irradiation of thermal neutron or non-radioactive elements was fed in the simulated fuel debris as fission products (FP), and the sample was immersed in pure water or artificial sea water. In this presentation, we would report the behavior of the solubility of the FP and the interpretation of its results.
-Zr-SS systemAkiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Sasaki, Takayuki*; Watanabe, Masayuki; Kumagai, Yuta; Kusaka, Ryoji
no journal, ,
In the accident at TEPCO's Fukushima Daiichi Nuclear Power Station, it is considered that the molten fuel reacted with zircaloy of the cladding tube and alloys containing iron as the main component, such as stainless steel, at high temperatures to generate fuel debris. For the removal, processing, and disposal of the debris in the future, it will be important to predict the properties of the debris. Therefore, in this study, simulated fuel debris containing Zr or ZrO and the constituent elements of stainless steel was prepared, and structural analysis was performed using XRD and SEM-EDX. We also evaluated the solid phase state after immersing the simulated debris in pure water or seawater.