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/MOX fuel oxidation under severe light water reactor accident conditionsLiu, J.; Miwa, Shuhei; Karasawa, Hidetoshi; Osaka, Masahiko
Nuclear Materials and Energy (Internet), 37, p.101532_1 - 101532_5, 2023/12
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Katsumura, Kosuke*; Takagi, Junichi*; Hosomi, Kenji*; Miyahara, Naoya*; Koma, Yoshikazu; Imoto, Jumpei; Karasawa, Hidetoshi; Miwa, Shuhei; Shiotsu, Hiroyuki; Hidaka, Akihide*; et al.
Nihon Genshiryoku Gakkai-Shi ATOMO
, 65(11), p.674 - 679, 2023/11
no abstracts in English
Miwa, Shuhei; Karasawa, Hidetoshi; Nakajima, Kunihisa; Kino, Chiaki*; Suzuki, Eriko; Imoto, Jumpei
JAEA-Data/Code 2021-022, 32 Pages, 2023/01
JAEA-Data-Code-2021-022.pdf:1.41MBJAEA-Data-Code-2021-022(errata).pdf:0.17MB
The improved model for cesium (Cs) chemisorption onto stainless steel (SS) in the fission product (FP) chemistry database named ECUME was incorporated into the severe accident (SA) analysis code SAMPSON for the more accurate estimation of Cs distribution within nuclear reactor vessels in the TEPCO's Fukushima Daiichi Nuclear Power Station (1F). The SAMPSON with the improved model was verified based on the analysis results reproducing the experimental results which were subjected to the modeling of Cs chemisorption behavior. Then, the experiment in the facility with the temperature gradient tube to simulate SA conditions such as temperature decrease and aerosol formation was analyzed to confirm availability of the improved model to the analysis of Cs chemisorption onto SS. The SAMPSON with the improved model successfully reproduced the experimental results, which indicates that the improved model and the analytical method such as setting a method of node-junction, models of aerosol formation and the calculation method of saturated CsOH vapor pressure can be applicable to the analysis of Cs chemisorption behavior. As the information on water-solubility of Cs deposits was also prerequisite to estimate the Cs distribution in the 1F because Cs can be transported through aqueous phase after the SA, the water-solubility of chemisorbed Cs compounds was investigated. The chemisorbed compounds on SS304 have been identified to CsFeO at 873 K to 973 K with higher water-solubility, CsFeSiO
at 973 K to 1273 K and CsSiO
at 1073 K to 1273 K with lower water-solubility. From these results, the water-solubility of chemisorbed Cs compounds can be estimated according to the SA analysis conditions such as temperature in the reactor and the CsOH concentration affecting the amount of chemisorbed Cs.
Uchida, Shunsuke; Karasawa, Hidetoshi; Kino, Chiaki*; Pellegrini, M.*; Naito, Masanori*; Osaka, Masahiko
Nuclear Engineering and Design, 380, p.111256_1 - 111256_19, 2021/08
Times Cited Count：6 Percentile：55.57(Nuclear Science & Technology)It is essential to grasp the long-term distributions of FP as well as fuel debris all over the Fukushima Daiichi Nuclear Power Plant (1F) for safe completion of its decommissioning projects. The fuel debris is going to be removed from the plant under the severe conditions of FP being scattered during major decommissioning work, and then, the decommissioning projects are going to be terminated by storing safely the removed debris as recovered fertile materials or as materials for final radioactive disposal. In order to determine the FP distribution in the plant for the long period from the accident occurrence to the termination of the plant decommissioning, procedures for analyzing multi-term FP behaviors were proposed. The proposed procedures should be improved by applying the FP data measured in the plant and validated based on the feedback data. Then, the accuracy-improved procedures should be applied to estimate FP distribution during each period of the decommissioning projects.
Miwa, Shuhei; Nakajima, Kunihisa; Miyahara, Naoya; Nishioka, Shunichiro; Suzuki, Eriko; Horiguchi, Naoki; Liu, J.; Miradji, F.; Imoto, Jumpei; Afiqa, B. M.; et al.
Mechanical Engineering Journal (Internet), 7(3), p.19-00537_1 - 19-00537_11, 2020/06
We constructed the fission product (FP) chemistry database named ECUME for LWR severe accident. This version of ECUME is equipped with dataset of the chemical reactions and their kinetics constants for the reactions of cesium(Cs)-iodine(I)-boron(B)-molybdenum(Mo)-oxygen(O)-hydrogen(H) system in gas phase, the elemental model for the high temperature chemical reaction of Cs with stainless steel applied as the structural material in a reactor, and thermodynamic data for CsBO vapor species and solids of CsSiO and CsFeSiO for these chemical reactions. The ECUME will provide estimation of Cs distribution due to the evaluation of effects of interaction with BWR control material B and stainless steel on Cs behavior in the Fukushima Daiichi Nuclear Power Station.
Miwa, Shuhei; Miyahara, Naoya; Nakajima, Kunihisa; Nishioka, Shunichiro; Suzuki, Eriko; Horiguchi, Naoki; Liu, J.; Miradji, F.; Imoto, Jumpei; Afiqa, B. M.; et al.
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05
We constructed the first version of fission product (FP) chemistry database named ECUME for LWR severe accident. The first version of ECUME is equipped with dataset of the chemical reactions and their kinetics constants for the reactions of cesium(Cs)-iodine(I)-boron(B)-molybdenum(Mo)-oxygen(O)-hydrogen(H) system in gas phase, the elemental model for the high temperature chemical reaction of Cs with stainless steel, and thermodynamic data for CsBO vapor species and solids of CsSiO and CsFeSiO. The ECUME will provide more accurate estimation of Cs distribution due to the evaluation of effects of interaction with BWR control material B and stainless steel on Cs behavior in the Fukushima Daiichi Nuclear Power Station.
-ray irradiation on the high temperature oxidation of austenitic stainless steel in supercritical waterNakahara, Yukio; Yamamoto, Masahiro; Karasawa, Hidetoshi*; Kiuchi, Kiyoshi; Katsumura, Yosuke*
Proceedings of 16th Pacific Basin Nuclear Conference (PBNC-16) (CD-ROM), 6 Pages, 2008/10
Three types of commercial-grade austenitic stainless steel, Type 304L, Type 316L, and Type 310S, were immersed in deaerated supercritical water (SCW) of 25 MPa, 550 
C with -ray irradiation for 1000 hours in total. Absorbed dose rates in SCW are estimated at 5-15 kGy h
. High temperature oxidation experiments resulted in the formation of two-layer oxide film in which the outer layer is porous iron oxide and the inner layer is dense iron-chromium-nickel oxide. Rate constants of parabolic rate law in net weight gains of Type 304L SS and Type 310S SS are decreased as the -ray exposure rate is increased. The net weight gain of -ray irradiated Type 316L SS is sharply fluctuating and decreasing, because the flaking of the outer layer occurred. Hematite is formed in the outer layer on all irradiated samples of examined alloys. The concentration of chromium on the surface is increased by -ray irradiation. A chromium-rich part in the inner layer accompanying a nickel-rich part in the metal is formed along to the oxide/metal interface of -ray irradiated Type 304L SS, non-irradiated and -ray irradiated Type 316L SS.
Miwa, Shuhei; Horiguchi, Naoki; Miyahara, Naoya*; Nakajima, Kunihisa; Suzuki, Eriko; Imoto, Jumpei; Liu, J.; Karasawa, Hidetoshi; Osaka, Masahiko
no journal, ,
We developed the fission product chemistry database named ECUME (
ffective 
hemistry database of fission products 
nder 
ultiphase raction) for the LWR severe accident. The dataset for chemical reaction kinetics of ECUME consists of main chemical reactions and their effective chemical reaction kinetic constants. This dataset has the advantages in kinetics evaluation of the effects of molybdenum and BWR control material boron on cesium and iodine chemistry. This can improve prediction accuracy of chemical forms and their fraction in lower temperature region such as a primary containment vessel and a reactor building.
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 CsSiO 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.
-ray irradiation on the high temperature oxidation of stainless steel in supercritical waterNakahara, Yukio; Yamamoto, Masahiro; Kato, Chiaki; Kiuchi, Kiyoshi; Karasawa, Hidetoshi*; Katsumura, Yosuke*
no journal, ,
Corrosion experiments of stainless steel (SS) in supercritical water (SCW) have done with a flowing SCW loop including a -ray irradiated autoclave. Three types of commercial-grade austenitic SS, Type 304L, Type 316L, and Type 310S, were examined. The condition of SCW was adjusted to the core environment of a SCW reactor system. Test samples of the SS were immersed in deaerated pure SCW (25 MPa, 550 C). Feed water was circulated at a flow rate of 4 L h. Absorbed dose rates near the surface of the test samples in SCW were estimated at 5-15 kGy h. The time dependence of net weight gains followed parabolic rate law except -ray irradiated Type 316L SS. The net weight gains of -ray irradiated Type 304L SS and Type 310S SS were larger than those of the non-irradiated. Rate constants of parabolic rate law in net weight gains of Type 304L SS and Type 310S SS were decreased as the -ray exposure rate was increased. The net weight gain of -ray irradiated Type 316L SS was fluctuating and decreasing widely, because the exfoliation of the surface oxide occurred. On the surface of all the samples, the formation of two-layer oxide film in which the outer layer was porous iron oxide and the inner layer was dense iron-chromium-nickel oxide occurred. Iron oxide in the outer layer was magnetite (Fe
O) with non-irradiated samples. Hematite (
-FeO) was additionally formed in the outer layer with -ray irradiated samples. A chromium-rich part in the inner layer was formed along to the oxide/metal interface of -ray irradiated Type 304L SS.
Liu, J.; Nakajima, Kunihisa; Miwa, Shuhei; Karasawa, Hidetoshi; Osaka, Masahiko
no journal, ,
Uchida, Shunsuke; Osaka, Masahiko; Karasawa, Hidetoshi; Kino, Chiaki*
no journal, ,
Dose rate conversion factors have been calculated to obtain the dose rate at CAMS detector locations from major FP species in the major partial zone of the D/W and S/C. Based on backward analysis with the conversion factors, the 
Cs amounts in the S/C were evaluated. From the evaluation, two points were concluded. (1) Transfer rate of cesium from the D/W to the S/C for Unit 1 was 2 times larger than that for Unit 3. (2) Transfer of cesium from the S/C water phase to gas phase, especially the S/C wall, was larger than that expected and the deposited cesium was transferred into water phase gradually. Transfer of cesium for Unit 3 was not observed. It was supposed that the differences in cesium transfers for both units might be mainly from cesium chemical forms, while differences in transfer rate from water phase to gas phase was not well explained yet.
Karasawa, Hidetoshi; Kino, Chiaki*; Suzuki, Eriko; Nakajima, Kunihisa; Miwa, Shuhei; Osaka, Masahiko
no journal, ,
The chemisorption velocities of CsOH vapor on stainless steels were examined experimentally by the Cs chemisorption test apparatus named CREST. Using obtained adsorption velocities, the amounts of CsOH vapors chemisorbed on SS walls of the steam separator and the steam dryer were evaluated using the SA code of SAMPSON under SA conditions in Fukushima Daiichi Nuclear Power Plants.
Miyahara, Naoya*; Karasawa, Hidetoshi; Imoto, Jumpei
no journal, ,
We report the issues obtained from the fundamental research in JAEA/CLADS from among the activities for extracting issues related to FP behavior for improvement of decommissioning work efficiency and source-term under the Research Committee on Fission Product Behavior Related to Decommissioning Work of Fukushima Daiichi NPP at AESJ.
Kino, Chiaki*; Karasawa, Hidetoshi*; Uchida, Shunsuke*; Nishioka, Shunichiro; Osaka, Masahiko
no journal, ,
To evaluate the remigration behavior of FP through the aqueous phase in FDNPS for a long term, an analysis methodology of contaminated water was developed based on SAMPSON code. The test analysis result for cesium concentration in the contaminated water in FDNPS unit 1 for 1 year, with the consideration of cesium release from the fuel debris to the aqueous phase had a good agreement with the actual measured cesium concentration.
Osaka, Masahiko; Miwa, Shuhei; Nakajima, Kunihisa; Suzuki, Chikashi; Karasawa, Hidetoshi
no journal, ,
Study on FP chemistry is introduced. Application of the computational science to the FP chemistry study is given.
Kino, Chiaki*; Karasawa, Hidetoshi*; Uchida, Shunsuke*; Naito, Masanori*; Osaka, Masahiko
no journal, ,
FP distribution in 1F was phenomenologically evaluated in views of accident scenario. Possible retention of chemisorbed Cs in the separator etc. was implied.
Karasawa, Hidetoshi*; Uchida, Shunsuke*; Kino, Chiaki*; Naito, Masanori*; Osaka, Masahiko
no journal, ,
FPs that can have impact on the fuel-debris retrieval are selected and amount and radioactivities are evaluated based on FP distribution inside containment predicted by SA analysis code.
Karasawa, Hidetoshi; Miwa, Shuhei; Kino, Chiaki*
no journal, ,
Oversaturated vapors released in a core in SAs change to monomers which produce clusters due to homogeneous or heterogeneous nucleation. In a primary system, clusters coagulate each other to grow particle sizes. Effects of the nucleation and coagulation on deposition of FP aerosols in the primary system were examined by the Phebus FPT1 analysis using the SAMPSON code.
Mizokami, Shinya; Osaka, Masahiko; Ito, Kenichi*; Karasawa, Hidetoshi*; Honda, Takeshi*
no journal, ,
Overview of the activity conducted in the project (Upgrading level of grasping state inside reactor) by cesium chemistry team will be introduced as a start point of the series presentation.
