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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：0 Percentile：0.01(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 CsSi
O
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.
ray irradiation on the corrosion of stainless steel in supercritical waterNakahara, Yukio; Karasawa, Hidetoshi*; Yamamoto, Masahiro; Kiuchi, Kiyoshi; Katsumura, Yosuke*
no journal, ,
A supercritical water-cooled nuclear reactor (SCWR) has been under review as one of advanced reactors. Corrosion tests of several types of stainless steel in supercritical water (25MPa, 400
500C) were executed under ray irradiation in order to clarify the effect of ray on the corrosion. The results of the tests shows that the corrosion of stainless steel was progressed by the growth and degradation of surface oxide film, the dependence of the parabolic rate law constant on temperature can be fit with Arrhenius' equation, ray irradiation changed the property of surface oxide film.
ray irradiation on surface film structures of stainless steels created in super critical water environmentYamamoto, Masahiro; Nakahara, Yukio; Karasawa, Hidetoshi*; Katsumura, Yosuke*
no journal, ,
Super critical water cooling reactor (SCWR), which has higher energy efficiency than existent reactor, has been planned and examined. To realize the SCWR system, it is important to ensure the reliabilities of the materials used in the super critical condition. Some types of stainless steels were immersed in super critical water with -ray irradiated condition. After the test, the surface films of stainless steels were analyzed. It was found that hematite (FeO
) was formed on the surface of oxide film with -ray irradiation. Contrastingly, complex oxide including Cr and Ni was formed on the surface without -ray irradiation.
-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 (FeO) 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.
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.
Kino, Chiaki*; Karasawa, Hidetoshi*; Uchida, Shunsuke*; Nishioka, Shunichiro; Osaka, Masahiko
no journal, ,
Analysis of the long-term transport behavior of fission products (FP) is important for decommissioning of Fukushima-Daiichi Nuclear Power Station, "Decommissioning analysis code" which can analyze thermal-hydraulic and FP behavior for 10 years after the severe accident has been developed based on SAMPSON code. As the results of test analysis for 2 months after SA, Cs concentration in the wet-well (W/W) decreased slower than that in the case of consideration only with treatment of contaminated water. This result indicates a possible long-term contribution of accumulated Cs in W/W as the Cs contamination source.
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.
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.
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.
Suzuki, Eriko; Nakajima, Kunihisa; Nishioka, Shunichiro*; Miwa, Shuhei; Horiguchi, Naoki; Imoto, Jumpei; Liu, J.; Karasawa, Hidetoshi; Osaka, Masahiko
no journal, ,
The elemental model set (EM) of ECUME consists of improved models which can be directly incorporated into the present severe accident analysis codes. The models of EM has advantages in considering various chemical conditions. The improved model for cesium (Cs) chemisorption has successfully reproduced the effects of Cs vapor concentration in gas phase and silicon content in stainless steel on the Cs chemisorption behavior. This improved model can contribute to more accurate estimation of Cs distribution in a high temperature area.
Nakajima, Kunihisa; Suzuki, Eriko; Nishioka, Shunichiro*; Miwa, Shuhei; Horiguchi, Naoki; Imoto, Jumpei; Liu, J.; Karasawa, Hidetoshi; Osaka, Masahiko
no journal, ,
Thermodynamic data of cesium compounds with boron and silicon are included in the thermodynamic dataset (TM) of ECUME. Chemical forms and fractions of cesium compounds formed in high temperature regions of nuclear reactors and revaporization amount of Cs chemisorbed onto stainless steel can be more accurately estimated by using the TM of ECUME. Incorporation of ECUME into severe accident analysis codes can cope with chemical behaviors of FPs influencing their release and transport behaviors and can be expected to improve source term estimations.
Uchida, Shunsuke*; Karasawa, Hidetoshi*; Kino, Chiaki*; Naito, Masanori*; Osaka, Masahiko
no journal, ,
Development of analysis code of FP behavior both for short and long terms after severe accident is conduced. A risk analysis method for workers' radiation and FP release is proposed based on the evaluation result for FP distribution during 10 years after the accident.
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.
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; 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.
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.
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.
