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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：56.80(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.
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*; 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.
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.
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.
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; 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.
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.
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.
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.
Karasawa, Hidetoshi; Okada, Hidetoshi*; Hidaka, Akihide*
no journal, ,
In order to contribute to "contributing to the improvement of source term prediction technology", which is one of the objectives of this committee, meeting materials of the "Study Group on Analysis of the Accident at TEPCO's Fukushima Daiichi Nuclear Power Station" conducted by the Nuclear Regulation Authority have been surveyed. Among them, meeting materials related to three areas were examined. (1) Contamination of the piping system for emergency gas treatment systems and their formation mechanisms, (2) Radiation levels on the operation floor and near the shield plugs and the presence of cesium between the shield plugs, and (3) Dose distribution in the building. As a result of the survey, the following issues were identified. Project 1: Evaluation of vent gas radiation dose, Project 2: Contamination mechanism of bent lines, Project 3: Confirmation of PCV leak pathways. In the future, these issues will be examined and evaluated by working groups, and the progress and results of activities will be summarized in a technical report to help improve the FP emission model.
Karasawa, Hidetoshi; Miwa, Shuhei; Suzuki, Eriko; Nakajima, Kunihisa; Kino, Chiaki*
no journal, ,
Temperature effects of chemisorption of CsOH vapor generated at about 1000K on SUS were examined using TeRRa test apparatus with temperature gradient tube from 1273K to 473K. The chemisorption amounts were measured using IPS after dissolving test coupons. These results were calculated using the SA code, SAMPSON. For the test analysis, the thermal hydraulic analysis (THA) module and the FP transport analysis (FPTA) module were used. The FPTA could calculated the chemisorption amount within the experimental error range using the gas temperature calculated by the THA module. So the temperature dependency of the chemisorption model used in the calculation was validated.
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.
Uchida, Shunsuke; Osaka, Masahiko; Karasawa, Hidetoshi; Kino, Chiaki*
no journal, ,
The Cs amounts in the major partial zone of the D/W and S/C of Units 1-3 have been evaluated by applying the BEP with the previously reported dose rate conversion factors. As a result of comparing the BEP results with those of the FEP based on the SA analysis code, the conclusions are summarized as follows. The measured dose rate for A and B detectors of D/W CAMS for Unit 1 showed the different patterns, which could be clearly explained by applying local wash-out effects. The Cs amounts in the D/W bottom regions for Units 1-3 could be evaluated by the BEP. The Cs amounts obtained with the BEP in the D/W bottom region and S/C for Unit 1 were consistent to those with the FEP. The Cs amounts obtained with the BEP in the D/W bottom regions for Units 2 and 3 were more than 10 times as large as those with the FEP.
