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Nakajima, Kunihisa; Nishioka, Shunichiro*; Suzuki, Eriko; Osaka, Masahiko
Mechanical Engineering Journal (Internet), 7(3), p.19-00564_1 - 19-00564_14, 2020/06
A large amount of cesium (Cs) chemisorbed onto stainless steel is predicted to be present especially in the upper region of reactor pressure vessel (RPV) during light water reactor severe accident (LWR SA) and a chemisorption model was developed for estimation of such amounts of Cs for stainless steel type 304 (SS304). However, this existing chemisorption model cannot accurately reproduce experimental results. Therefore, in this study, a modified Cs chemisorption model which accounts for silicon content in SS304 and concentration of cesium hydroxide (CsOH) in gaseous phases was constructed by combining penetration theory for gas-liquid mass transfer with chemical reaction and mass action law for CsOH decomposition at interface between gaseous and solid phases. As a result, it was found that the modified model was able to reproduce the experimental data more accurately than the existing model.
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; Takase, Gaku; Imoto, Jumpei; Nishioka, Shunichiro; Miyahara, Naoya; Osaka, Masahiko
Journal of Nuclear Science and Technology, 57(3), p.291 - 300, 2020/03
Times Cited Count：10 Percentile：64.22(Nuclear Science & Technology)For the evaluation of transport behavior of control material boron in a severe accident of BWR from the viewpoint of chemical effects on cesium and iodine behavior, boron chemistry during transportation in the high temperature region above 400 K was experimentally investigated. The heating tests of boron oxide specimen were conducted using the dedicated experimental apparatus reproducing fission product release and transport in steam atmosphere. Released boron oxide vapor was deposited above 1,000 K by the condensation onto stainless steel. The boron deposits and/or vapors significantly reacted with stainless steel above 1,000 K and formed the stable iron-boron mixed oxide (FeO)BO
. These results indicate that released boron from degraded BWR control blade in a severe accident could remain in the high temperature region such as a Reactor Pressure Vessel. Based on these results, it can be said that the existence of boron deposits in the high temperature region would decrease the amount of transported cesium vapors from a Reactor Pressure Vessel due to possible formation of low volatile cesium borate compounds by the reaction of boron deposits with cesium vapors.
Nishioka, Shunichiro; Nakajima, Kunihisa; Suzuki, Eriko; Osaka, Masahiko
Journal of Nuclear Science and Technology, 56(11), p.988 - 995, 2019/11
Times Cited Count：14 Percentile：75.67(Nuclear Science & Technology)In order to contribute to improvement of Cs chemisorption model used in severe accident analysis codes, the influence of chemical factors (temperature, atmosphere, concentration of affecting chemical elements etc.) on the Cs chemisorption behaviour onto stainless steel was investigated experimentally. It was found that the surface reaction rate constant used in the current Cs-chemisorption model was influenced by not only temperature, as already known, but also atmosphere, cesium hydroxide (CsOH) concentration in the gas phase and silicon content in SS304. Such chemical factors should be considered for the construction of the improved Cs-chemisorption model. Another important finding is that the chemisorption behavior at lower temperatures, around 873 K, could differ from those above 1073 K. Namely, Cs-Fe-O compounds would form as the main Cs-chemisorbed compounds at 873 K while Cs-Si-Fe-O compounds at more than 1073 K.
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.
Nakajima, Kunihisa; Nishioka, Shunichiro; Suzuki, Eriko; Osaka, Masahiko
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05
Cesium chemisorption models were developed for estimation of amount of cesium chemisorbed onto stainless steel type 304 (SS304) during light water reactor severe accident. However, existing chemisorption models cannot accurately reproduce experimental results. In this study, a modified cesium chemisorption model was constructed based on a penetration theory for gas-liquid mass transfer with chemical reaction and was able to adequately describe effects on concentration of cesium hydroxide in gaseous phase and silicon content in SS304. It was found that the modified model can more accurately reproduce the experimental data than the existing model.
Suzuki, Eriko; Takase, Gaku; Nakajima, Kunihisa; Nishioka, Shunichiro; Hashimoto, Naoyuki*; Isobe, Shigehito*; Osaka, Masahiko
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
In order to acquire the knowledge of the Cs chemisorption behaviour in the lower temperature region, the Cs chemisorbed compounds and the surface reaction rates were investigated by conducting the Cs chemisorption tests onto stainless steel at 873 and 973 K. As a result, The cesium ferrate compounds were revealed to be formed at this temperatures. It was seen that the dependences of surface reaction rate constant on this temperature were different from that at the higher temperature region. This behaviour leads to the conclusion that the Cs chemisorption model in the low temperature region should be newly constructed.
Miradji, F.; Suzuki, Chikashi; Nishioka, Shunichiro; Suzuki, Eriko; Nakajima, Kunihisa; Osaka, Masahiko; Barrachin, M.*; Do, T. M. D.*; Murakami, Kenta*; Suzuki, Masahide*
Proceedings of 9th Conference on Severe Accident Research (ERMSAR 2019) (Internet), 21 Pages, 2019/03
Al
Kobayashi, Riki*; Kaneko, Koji; Saito, Kotaro*; Mignot, J.-M.*; Andr
, G.*; Robert, J.*; Wakimoto, Shuichi; Matsuda, Masaaki*; Chi, S.*; Haga, Yoshinori; et al.
Journal of the Physical Society of Japan, 83(10), p.104707_1 - 104707_5, 2014/10
Times Cited Count：17 Percentile：67.75(Physics, Multidisciplinary)Okuda, Shin*; Miyamoto, Kenji*; Fukuyama, Toshishige*; Nishioka, Shu*; Hatayama, Akiyoshi*; Fukano, Azusa*; Hanada, Masaya; Kojima, Atsushi
AIP Conference Proceedings 1515, p.107 - 113, 2013/02
Times Cited Count：9 Percentile：93.04(Physics, Applied)A meniscus of plasma-beam boundary in H
ion sources largely affects the extracted H ion beam optics. Recently it is shown that the beam halo is mainly caused by the meniscus, i.e. ion emissive surface, close to the plasma grid (PG) where its curvature is large. The purpose of this study is to clarify the effect of H surface production rate on plasma meniscus and beam halo formation with PIC (particle-in-cell) modeling. It is shown that the plasma meniscus and beam halo formation is strongly dependent on the amount of surface produced H ions.
150
C temperature rangeDo, Thi-Mai-Dung*; Nhut, V. L.*; Murakami, Kenta*; Suematsu, Hisayuki*; Nakajima, Kunihisa; Nishioka, Shunichiro; Suzuki, Eriko; Miradji, F.; Osaka, Masahiko
no journal, ,
The interaction between CsMoO with concrete within the temperature range of 600150C in Ar gas is studied. It seems that there is no reaction between CsMoO aerosol particles with concrete at these temperatures. However, because of the hygroscopic property, CsMoO aerosol particles change to the liquid phase and quickly diffused inside the concrete bulk.
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.
Al, 3Kobayashi, Riki; Kaneko, Koji; Wakimoto, Shuichi; Haga, Yoshinori; Matsuda, Tatsuma; Yamamoto, Etsuji; Robert, J.*; Mignot, J.-M.*; Andr, G.*; Matsuda, Masaaki*; et al.
no journal, ,
no abstracts in English
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.
Nishioka, Shunichiro; Takase, Gaku; Nakajima, Kunihisa; Suzuki, Eriko; Osaka, Masahiko
no journal, ,
The chemical/physical properties of Cs-chemisorbed deposit could change along with the progression of LWR severe accident (SA). In this study, the influence of temperature change on the properties of Cs-chemisorbed deposit was investigated experimentally. It was found that Cs-Fe-O compounds, which had been formed by chemisorption at 873 K, could transform into Cs-Si-(Fe)-O compounds at 1273 K.
CSuzuki, Eriko; Takase, Gaku; Nakajima, Kunihisa; Nishioka, Shunichiro; Osaka, Masahiko
no journal, ,
In order to estimate the cesium (Cs) distribution in the reactor pressure vessel under severe accident (SA), Cs chemisorption behaviour onto stainless steel have been investigated. In our previous study on Cs chemisorption behaviour at above 800C, it was found that the Cs silicate compounds were formed as Cs chemisorbed compounds. In this study, Cs chemisorption tests at lower temperatures around 600C were carried out to investigate the Cs chemisorbed compounds at lower temperatures. As a result, cesium ferrate compounds were formed and it was suggested that the chemical reaction at lower temperatures would be different from that at above 800C.
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.
Imoto, Jumpei; Nishioka, Shunichiro*; Nakajima, Kunihisa; Suzuki, Eriko; Osaka, Masahiko
no journal, ,
In the case of elution of chemisorbed Cs onto the reactor pressure vessel structure materials in the Fukushima Daiichi Nuclear Power Station due to wall condensation of steam, etc., this eluted Cs can be become one of the long-term source term through the aqueous phase. Therefore, in order to clarify this dissolution behavior, a dissolution test of Cs chemisorbed onto stainless steel in water at room temperature was performed up to 50 days. As a result, it was found that Cs chemisorbed on stainless steel continues to elute in trace amounts over long period of time in water. It was suggested that this can be one of the long-term source term.
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.
Nishioka, Shunichiro; Nakajima, Kunihisa; Suzuki, Eriko; Miradji, F.; Osaka, Masahiko
no journal, ,
In order to contribute to Cs distribution analysis in Fukushima Daiichi Nuclear Power Station reactors by using severe accident analysis code, the influence of chemical factors (temperature, atmosphere etc.) on the Cs chemisorption behaviour onto stainless steel was investigated experimentally. An improved Cs chemisorption model was then established considering the effect of chemical factors obtained by the experiment. The accuracy of the present model is greatly improved by 1 order of magnitude compared with that incorporated in the existing SA codes.
