Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Nakajima, Kunihisa; Suzuki, Eriko; Osaka, Masahiko
no journal, ,
Severe accident (SA) analysis codes predicted that a large amount of cesium (Cs) chemisorbed onto stainless steel would be localized in the upper region of reactor pressure vessels (RPVs) in Fukushima Daiichi Nuclear Power Station because the RPV internals such as steam dryer and steam separator have large surface areas and would have experienced relatively high temperature. However, the current Cs chemisorption model incorporated into SA analysis codes cannot accurately reproduce experimental results such as temperature dependence. Therefore, JAEA has constructed an improved Cs chemisorption model validated above 1073 K where a Cs silicate was mainly formed as Cs-chemisorbed compound. On the other hand, recent study in JAEA indicated that the chemisorption rate was much higher than that expected from the improved model in a relatively low temperature region, around 873 K. Such an enhancement was suggested to be resulted from formation of a Cs ferrate. Thus, a lower temperature model validated in the temperature region where the main Cs-chemisorbed compound was a Cs ferrate was constructed. In this study, an overall correlation model combined the higher and the lower temperature models was developed by considering fraction of the Cs silicate and the Cs ferrate.
Imoto, Jumpei; Miwa, Shuhei; Miyahara, Naoya; Nakajima, Kunihisa; Nishioka, Shunichiro; Suzuki, Eriko; Horiguchi, Naoki; Liu, J.; Miradji, F.; Afiqa, B. M.; et al.
no journal, ,
Fission product (FP) chemistry database ECUME (Effective Chemistry database of fission products Under Multiphase rEaction) consists of three kinds of datasets: CRK (dataset for Chemical Reaction Kinetics), EM (Elemental Model set) and TD (ThermoDynamic dataset). The present ECUME is equipped with the CRK for the reaction of Cs-I-B-Mo-O-H system in gas phase, the EM for the Cs chemical reaction with stainless steel (SS) (Cs chemisorption onto SS) and the TD for CsBO
vapor species and solid CsSi
O
and CsFeSiO. The Cs chemisorption behavior model has successfully reproduced the effects of CsOH vapor concentration in gas phase and Si content in SS on the Cs chemisorption behavior which were not able to be considered by the existing model. The ECUME are expected to contribute to more accurate evaluation of FP distribution in Fukushima Daiichi Nuclear Power Station.
Nakayoshi, Akira; Jegou, C.*; De Windt, L.*; Perrin, S.*; Peuget, S.*; Washiya, Tadahiro
no journal, ,
Pshenichnikov, A.; Kurata, Masaki; Nagae, Yuji; Yamazaki, Saishun
no journal, ,
Pshenichnikov, A.; Kurata, Masaki; Nagae, Yuji; Yamazaki, Saishun
no journal, ,
Kurata, Masaki; Pham, V. H.; Nagae, Yuji
no journal, ,
Sato, Takumi; Oikawa, Katsunari*; Ueshima, Nobufumi*; Nagae, Yuji; Kurata, Masaki
no journal, ,
Macroscopic segregation of molten core components occurs with slow cooling rate in the accident of Fukushima Daiichi Nuclear Power Plants. In order to investigate these segregation behavior, the solidification model for numerical simulation has been developed. In this model, solidification and microscopic segregation of molten corium are simulated with the Scheil model and thermal properties calculated by Thermo-calc. In this study, the validation of macrosegregation analysis of this model were performed. As the preliminary analysis, the calculation results were compared with corium solidification experiments. It was proved that this model can estimate the tendencies of macrosegregation.
Kawakami, Kazuto*; Tanaka, Masahiro*; Shirasu, Noriko; Kurata, Masaki; Nagae, Yuji
no journal, ,
JAEA and NSTec develop a thermodynamic database for fuel debris and concrete based on iron and concrete system, which has been developed for analysis of steel making process. Ionic two-sublattice model and cell model are examined for thermodynamic models of liquid oxide used in SA analysis. The current state and issues of the database used the models will be discussed.
Yamashita, Susumu; Nagae, Yuji; Kurata, Masaki; Yoshida, Hiroyuki
no journal, ,
no abstracts in English
Kumagai, Yuta; Kusaka, Ryoji; Nakada, Masami; Akiyama, Daisuke*; Watanabe, Masayuki; Sasaki, Takayuki*; Sato, Nobuaki*; Kirishima, Akira*
no journal, ,
Since uranium (U) can take numerous chemical states depending on conditions to which it is exposed, the chemical behavior of fuel components is needed for fuel debris treatment generated by Fukushima Daiichi NPS accident. Therefore, understanding on the chemistry of the U materials is essential to estimate these materials' stabilities. One of the important chemical dynamics of uranium is oxidative dissolution of U(IV) materials. It is well known that under the action of ionizing radiation U(IV) oxide matrix of nuclear fuel is gradually oxidized to U(VI) that is fairly water-soluble as uranyl ion. Then, the dissolution of the matrix and the release of radionuclides take place by contact with water. Such chemical degradation may occur for the fuel debris in the Fukushima Daiichi NPS. Hence, we have been investigating the chemical stability of U materials which are anticipated to be included in the fuel debris. As a first step of the investigation, we applied spectroscopic analysis, namely Raman scattering and fluorescence microscopic spectroscopies and Fe-57 M
ssbauer spectroscopy for chemical characterization of a pyrochemical product prepared from U(IV) oxide and stainless steel. We have employed these spectroscopic techniques since they are applicable for surface analysis. This is a specific advantage for the investigation of chemical degradation of solid U materials.
U
O
Itakura, Mitsuhiro
no journal, ,
no abstracts in English