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Journal Articles

Development of fission product chemistry database ECUME for the LWR severe accident

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$$_{2}$$ vapor species and solids of Cs$$_{2}$$Si$$_{4}$$O$$_{9}$$ and CsFeSiO$$_{4}$$ 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.

Journal Articles

Study on chemisorption model of cesium hydroxide onto stainless steel type 304

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.

Journal Articles

Cesium chemisorbed species onto stainless steel surfaces; An Atomistic scale study

Miradji, F.; Suzuki, Chikashi; Nakajima, Kunihisa; Osaka, Masahiko

Journal of Physics and Chemistry of Solids, 136, p.109168_1 - 109168_9, 2020/01

 Times Cited Count:2 Percentile:26.2(Chemistry, Multidisciplinary)

Journal Articles

An Experimental investigation of influencing chemical factors on Cs-chemisorption behavior onto stainless steel

Nishioka, Shunichiro; Nakajima, Kunihisa; Suzuki, Eriko; Osaka, Masahiko

Journal of Nuclear Science and Technology, 56(11), p.988 - 995, 2019/11

 Times Cited Count:9 Percentile:85.1(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.

Journal Articles

Modelling of cesium chemisorption under nuclear power plant severe accident conditions

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

Journal Articles

An Experimental investigation for atmospheric effects on Cs chemisorption onto stainless steel

Nakajima, Kunihisa; Suzuki, Eriko; Miyahara, Naoya; Osaka, Masahiko

Progress in Nuclear Science and Technology (Internet), 5, p.168 - 170, 2018/11

Chemical interaction between cesium (Cs) vapor and stainless steel (SS) surface known as chemisorption can cause a significant amount of Cs retention on the inner surfaces within the reactor pressure vessel during a light water reactor severe accident (SA). Although the chemisorption is known to be influenced with temperature and atmosphere, their dependancies are not yet fully understood. Therefore, the Cs chemisorption behaviours under mixed gases of steam and hydrogen were experimentally examined to contribute to a better understanding of the chemisorption behaviours under various atmospheres experienced during the SA at the Fukushima Daiichi Nuclear Power Station. As a result, it was found that the deposited amounts of Cs onto the SS in the steam-containing atmosphere were much higher than those in the no steam atmosphere. It was considered that Cs revaporization from a chemisorbed product was one of the reasons why the deposited amounts under the reducing atmosphere decreased.

Journal Articles

Prediction of chemical effects of Mo and B on the Cs chemisorption onto stainless steel

Di Lemma, F. G.; Yamashita, Shinichiro; Miwa, Shuhei; Nakajima, Kunihisa; Osaka, Masahiko

Energy Procedia, 127, p.29 - 34, 2017/09

 Times Cited Count:4 Percentile:94.14

Chemical effects of molybdenum (Mo) and boron (B), which were considered to form compounds with Cs, on the Cs chemisorption were predicted using a chemical equilibrium calculation. It is seen that Cs$$_{2}$$MoO$$_{4}$$ were formed in the chemisorbed compounds. On the other hand, little effects were observed for B. The results suggest that the effects of Mo should be considered for further experimental investigation.

Journal Articles

Experimental investigation of the influence of Mo contained in stainless steel on Cs chemisorption behavior

Di Lemma, F. G.; Nakajima, Kunihisa; Yamashita, Shinichiro; Osaka, Masahiko

Journal of Nuclear Materials, 484, p.174 - 182, 2017/02

 Times Cited Count:18 Percentile:91.08(Materials Science, Multidisciplinary)

Chemisorption phenomena can affect fission products retention in the nuclear reactor vessel during a Severe Accident (SA). This paper will describe the influence of molybdenum contained in type 316 stainless steel (SS) on Cs chemisorption. Our experiments showed the formation of Cs-Mo compounds in addition to CsFeSiO$$_{4}$$, observed previously on SS304. The results of high temperature stability tests on the deposits are also presented. These tests aimed at simulating the revaporization of FP from structural materials during a SA. From our results, it can be inferred that Cs-Mo deposits may revaporize, contributing as a delayed source to the radioactive release.

JAEA Reports

Results and progress of fundamental research on fission product chemistry; Progress report in 2015

Osaka, Masahiko; Miwa, Shuhei; Nakajima, Kunihisa; Di Lemma, F. G.*; Suzuki, Chikashi; Miyahara, Naoya; Kobata, Masaaki; Okane, Tetsuo; Suzuki, Eriko

JAEA-Review 2016-026, 32 Pages, 2016/12

JAEA-Review-2016-026.pdf:6.18MB

A fundamental research program on fission product (FP) chemistry has started since 2012 for the purpose of establishment of a FP chemistry database in each region of LWR under severe accident and improvement of FP chemical models based on the database. Research outputs are reflected as fundamental knowledge to both the research and development of decommissioning of Fukushima Daiichi Nuclear Power Station (1F) and enhancement of LWR safety. Four research items have thus been established considering the specific issues of 1F and the priority in the source term research area, as follows: effects of boron (B) release kinetics and thermal-hydraulic conditions on FP behavior, cesium (Cs) chemisorption and reactions with structural materials, enlargement of a thermodynamic and thermophysical properties database for FP compounds and development of experimental and analytical techniques for the reproduction of FP behavior and for direct measurement methods of chemical form of FP compounds. In this report, the research results and progress for the year 2015 are described. The main accomplishment was the installation of a reproductive test facility for FP release and transport behavior. Moreover, basic knowledge about the Cs chemisorption behavior was also obtained. In addition to the four research items, a further research item is being considered for deeper interpretation of FP behavior by the analysis of samples outside of the 1F units.

Journal Articles

Size dependence in adsorption on model surfaces

Erkoc, S.*; Bastug, T.*; Hirata, Masaru; Tachimori, Shoichi

Chemical Physics Letters, 321(3-4), p.321 - 327, 2000/04

 Times Cited Count:0 Percentile:0.01(Chemistry, Physical)

no abstracts in English

Journal Articles

Bonding, structure and magnetism of physisorbed and chemisorbed O$$_{2}$$ on Pt(III)

W.Wurth*; J.Stoehr*; P.Feulner*; X.Pan*; K.R.Bauchspiess*; Baba, Yuji; D.Menzel*

Physical Review Letters, 65(19), p.2426 - 2429, 1990/11

 Times Cited Count:217 Percentile:97.7(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Sorption mechanisms of tritium on the surface of borosilicate glass

Saeki, Masakatsu; Hirabayashi, Takakuni

Radiochimica Acta, 35, p.233 - 238, 1984/00

no abstracts in English

Oral presentation

On the chemisorption of Cs onto stainless steel structural material

Yamashita, Shinichiro; Miwa, Shuhei; Osaka, Masahiko; Nagase, Fumihisa

no journal, , 

Cesium (Cs) chemisorption behavior onto stainless steel (SS) structural materials under LWR severe accident conditions was investigated by means of a chemical equilibrium calculation. Two categories of compounds formed by the Cs-chemisorption onto the SS were identified by a literature review, i.e. Cs-Cr-O and Cs-Si-O system compounds. The chemical stability of Cs-including compounds was evaluated by a chemical equilibrium calculation as a function of oxygen potential. Results showed that Cs-Si-O compounds were stable under a wide range of oxygen potential, while Cs-Cr-O was formed under a limited range. It was also shown that B inclusion might suppress the formation of Cs-Si-O compounds by a formation of Cs-B-O vapor.

Oral presentation

Microstructural study of Cs-chemisorbed stainless steel

Di Lemma, F. G.; Yamashita, Shinichiro; Nakajima, Kunihisa; Miwa, Shuhei; Osaka, Masahiko; Nagase, Fumihisa

no journal, , 

This study will describe the surface analyses performed on stainless steel samples, which endured cesium corrosion under controlled laboratories conditions, aimed to simulate reactor accidents. The aim of this study was to obtain fundamental knowledge on the characteristics of the Cs-chemisorbed deposits and on the chemisorption mechanisms. The experiments showed that Cesium has high affinity with Silicon, and that the concentration of the formed compound decreased with increasing temperature.

Oral presentation

Cesium chemisorption behavior onto structural material under severe accident conditions, 5; Progress on microstructural analyses

Di Lemma, F. G.; Nakajima, Kunihisa; Yamashita, Shinichiro; Osaka, Masahiko; Nagase, Fumihisa

no journal, , 

This work will compare the microstructural results obtained from different Cs-chemisorbed stainless steel (SS) samples (SS304 and modified-SS316). The analyses showed that Cs-chemisorption was influenced by the presence of different minor elements in SS (such as Si and Mo), as the deposits on the different samples exhibited different properties.

Oral presentation

Experimental studies on Cs chemisorption on reactor structural materials and their behaviour at high temperature

Suzuki, Eriko; Di Lemma, F. G.; Nakajima, Kunihisa; Yamashita, Shinichiro; Osaka, Masahiko

no journal, , 

In order to clarify the re-vaporization behavior of cesium (Cs) chemisorbed compounds which formed onto reactor structural materials during Severe Accident (SA), Cs chemisorbed samples were reheated at 1000$$^{circ}$$C and then microstructural analysis of the chemisorbed samples was conducted. In the case of stainless steel containing Mo, Cs-Mo-O compounds were formed on surface, together with major Cs-Fe-Si-O compounds, and re-vaporized easier than Cs-Fe-Si-O compounds at 1000$$^{circ}$$C.

Oral presentation

FP chemistry in a high temperature region of LWR under a severe accident, 7; Surface analyses of Strontium compounds chemisorbed onto Stainless steel 304

Afiqa, B. M.; Nakajima, Kunihisa; Miwa, Shuhei; Osaka, Masahiko; Oishi, Yuji*; Muta, Hiroaki*; Kurosaki, Ken*; Yamanaka, Shinsuke*

no journal, , 

The release of Sr from fuel would be enhanced by the formation of volatile SrCl$$_{2}$$ in case of seawater injection into the core like as Fukushima Dai-ichi Nuclear Power Plant severe accidents. Since these volatile Sr vapor species can chemically react with stainless steel (SS) at high temperature, the chemisorption behavior is important in evaluating the Sr distribution in the reactor. Therefore, in order to verify the chemisorption behavior of SrCl$$_{2}$$ (generated by seawater injection) vapor species onto SS 304, chemical adsorption by the experiment was carried out and the compound formed on the SS 304 surface was analyzed. As a result, it was found a stable Sr/Si/O compound was formed on the surface of SS 304.

Oral presentation

Cesium chemisorption behavior onto stainless steel at temperatures higher than 1073 K

Nakajima, Kunihisa; Nishioka, Shunichiro; Suzuki, Eriko; Miradji, F.; Osaka, Masahiko

no journal, , 

Radioactive cesium (Cs) localized in the upper region of reactor pressure vessel (RPV) is one of the major concerns, especially in the case of the fuel debris retrieval accessing from top of the RPV. For estimation of amount of Cs chemisorbed onto structure materials, Cs chemisorption model is developed and incorporated into present severe accident codes. However, this chemisorption model cannot accurately reproduce experimental results. Therefore, this study elucidates essential factors influencing the Cs chemisorption behavior and construct the Cs chemisorption model considering these factors. It was found that this model can more accurately reproduce not only our experimental results but also the results used to construct the existing chemisorption model.

Oral presentation

Comparative study of Cs silicates properties between DFT calculation and experimental data

Miradji, F.; Suzuki, Eriko; Nishioka, Shunichiro; Suzuki, Chikashi; Nakajima, Kunihisa; Oishi, Yuji*; Muta, Hiroaki*; Kurosaki, Ken*; Do, Thi Mai Dung*; Osaka, Masahiko

no journal, , 

Oral presentation

Chemical interaction between Sr compounds and Zircaloy

Afiqa, B. M.; Nakajima, Kunihisa; Nishioka, Shunichiro; Miwa, Shuhei; Osaka, Masahiko

no journal, , 

In the accident of Fukushima Daiichi Nuclear Power Station, release of Sr from fuel would be enhanced by formation of volatile SrCl$$_{2}$$ and chemical reaction of Sr onto reactor structural material such as Zircaloy (Zry) would occur. Then, chemical interaction between Sr related compounds and Zry were investigated to elucidate such a chemical behavior. As a result, SrCl$$_{2}$$ vapor does not directly react with Zry at 1273 K.

Oral presentation

High temperature chemical reaction of strontium vapor species with Stainless steel

Afiqa, B. M.; Nakajima, Kunihisa; Miwa, Shuhei; Osaka, Masahiko; Oishi, Yuji*; Muta, Hiroaki*; Kurosaki, Ken*

no journal, , 

The release of strontium (Sr) from a fuel would be enhanced by the formation of volatile SrCl$$_{2}$$ in case of seawater injection into the core of Fukushima Dai-ichi Nuclear Power Plant. We investigated the chemisorption behavior of releasing SrCl$$_{2}$$ vapor onto type 304 stainless steel. It was observed that stable Sr-Si-O compounds were formed on the stainless steel surface.

21 (Records 1-20 displayed on this page)