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Journal Articles

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

Miwa, Shuhei; Miyahara, Naoya; Nakajima, Kunihisa; Nishioka, Shunichiro; Suzuki, Eriko; Horiguchi, Naoki; Liu, J.; Miradji, F.; Imoto, Jumpei; Mohamad, B. A.; 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$$_{2}$$ vapor species and solids of Cs$$_{2}$$Si$$_{4}$$O$$_{9}$$ and CsFeSiO$$_{4}$$. 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.

Journal Articles

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

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.

Journal Articles

Experimental study on Cs chemisorption behaviour onto stainless steel at around 873 K

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.

Journal Articles

Chemical trapping of Sr vapor species by Zircaloy cladding under a specific chemical condition

Mohamad, A.*; Nakajima, Kunihisa; Suzuki, Eriko; Miwa, Shuhei; Osaka, Masahiko; Oishi, Yuji*; Muta, Hiroaki*; Kurosaki, Ken*

Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05

In the accident of Fukushima Daiichi Nuclear Power Station, formation of a volatile SrCl$$_{2}$$ could have occurred by the sea-water injection into the core. This can cause the release of non-volatile group Sr from the fuel to induce chemical reactions with reactor structural materials, such as stainless steel and Zircaloy (Zry) cladding. Such reactions could cause the changes in distribution of Sr in the reactor. Chemical reactions between Sr species and Zry were therefore investigated experimentally. As the result, it can be said that Sr vapor species were chemically trapped right after the release from fuel. This trapping effect of Sr by Zry-cladding implies a possibility of preferable Sr retention in the oxide phase of debris.

Journal Articles

Synthesis and characterization of CeO$$_{2}$$-based simulated fuel containing CsI

Takamatsu, Yuki*; Ishii, Hiroto*; Oishi, Yuji*; Muta, Hiroaki*; Yamanaka, Shinsuke*; Suzuki, Eriko; Nakajima, Kunihisa; Miwa, Shuhei; Osaka, Masahiko; Kurosaki, Ken*

Nippon Genshiryoku Gakkai Wabun Rombunshi, 17(3/4), p.106 - 110, 2018/12

In order to establish the synthesis method of simulated fuel contacting Cesium (Cs) which is required for the evaluation of physical/chemical characteristics in fuel and release behavior of Cs, sintering tests of the cerium dioxide (CeO$$_{2}$$) based simulated fuels containing Cesium iodide (CsI) are performed by using spark plasma sintering (SPS) method. The sintered CeO$$_{2}$$ pellets with homogeneous distribution of several micro meter of CsI spherical precipitates were successfully obtained by optimizing SPS conditions.

Journal Articles

Effect of atmosphere on the vaporization behavior of CsFeSiO$$_{4}$$

Suzuki, Eriko; Nakajima, Kunihisa; Osaka, Masahiko

Progress in Nuclear Science and Technology (Internet), 5, p.165 - 167, 2018/11

In severe accident condition, CsFeSiO$$_{4}$$ could be formed by Cesium (Cs) chemisorption onto reactor structural materials. For evaluation of re-vaporization behavior, effect of atmosphere on the vaporization behavior of CsFeSiO$$_{4}$$ at high temperature was investigated by thermal gravimetric-differential thermal analyzer (TG-DTA) experiments. As a result, it was found that vaporization of CsFeSiO$$_{4}$$ in reducing atmosphere (Ar-5%H$$_{2}$$) started at relatively low temperature, about 800$$^{circ}$$C, compared with in atmosphere containing H$$_{2}$$O (Ar-5%H$$_{2}$$-5%H$$_{2}$$O). It was inferred that a possible chemical reaction for the weight loss at around 800$$^{circ}$$C would occurred by the decomposition of CsFeSiO$$_{4}$$ into volatile Cs vapor species under H$$_{2}$$.

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

Chemical form analysis of reaction products in Cs-adsorption on stainless steel by means of HAXPES and SEM/EDX

Kobata, Masaaki; Okane, Tetsuo; Nakajima, Kunihisa; Suzuki, Eriko; Owada, Kenji; Kobayashi, Keisuke*; Yamagami, Hiroshi; Osaka, Masahiko

Journal of Nuclear Materials, 498, p.387 - 394, 2018/01

 Times Cited Count:1 Percentile:38.14(Materials Science, Multidisciplinary)

In this study, for the understandings of Cesium (Cs) adsorption behavior on structure materials in severe accidents at a light water nuclear reactor, the chemical state of Cs and its distribution on the surface of SUS304 stainless steel (SS) with different Si concentration were investigated by hard X-ray photoelectron spectroscopy (HAXPES) and scanning electron microscope / energy dispersive X-ray spectroscopy (SEM/EDX). As a result, it was found that Cs is selectively adsorbed at the site where Si distributes with high concentration. CsFeSiO$$_{4}$$ is a dominant Cs products in the case of low Si content, mainly formed, while Cs$$_{2}$$Si$$_{2}$$O$$_{5}$$ and Cs$$_{2}$$Si$$_{4}$$O$$_{9}$$ are formed in addition to CsFeSiO$$_{4}$$ in the case of high Si content. The chemical forms of the Cs compounds produced in the adsorption process on the SS surface has a close correlation with the concentration and chemical states of Si originally included in SS.

Journal Articles

Results and progress of fundamental research on FP chemistry

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

Proceedings of 8th European Review Meeting on Severe Accident Research (ERMSAR 2017) (Internet), 11 Pages, 2017/05

Fundamental research on fission product (FP) chemistry is underway at Japan Atomic Energy Agency. The purpose is to establish a FP chemistry database in each region of a LWR under severe accident conditions. Improvement of FP chemical models based on this database is also an important task of the research. Research outputs are reflected to the research and development of decommissioning of Fukushima Daiichi Nuclear Power Station (1F) and the 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, - Establishment of a thermodynamic and thermophysical properties database for FP compounds, - Development of experimental and analytical techniques for the reproduction of FP behavior. In this paper, results and progress of the research are presented.

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

Development of completely Solenoidless tokamak operation in JT-60U

Ushigome, Masahiro*; Ide, Shunsuke; Ito, Satoshi*; Jotaki, Eriko*; Mitarai, Osamu*; Shiraiwa, Shunichi*; Suzuki, Takahiro; Takase, Yuichi*; Tanaka, Shigetoshi*; Fujita, Takaaki; et al.

Nuclear Fusion, 46(2), p.207 - 213, 2006/02

 Times Cited Count:11 Percentile:57.02(Physics, Fluids & Plasmas)

This papaer studies on tokamak plasma start-up completely without central solenoid (CS). On the JT-60 tokamak it is demonstrated that a completely CS-less Ip start-up to 100 kA was achieved even without any null-point by Electron cyclotron range of frequencies (ECRF) and outer PF coil current swing only. Necessary conditions (the EC power, the toroidal field etc.) were clarified. Moreover, it was succeded to maintain Ip = 260kA for 1 sec without CS by NB only. In addition Ip ramp-up by EC and NB only (without LHCD) from 215 to 310kA was achieved. In a high confinement reversed shear discharge, a result suggesting bootstrap over drive was obtained.

Journal Articles

Formation of advanced tokamak plasmas without the use of an ohmic-heating solenoid

Shiraiwa, Shunichi*; Ide, Shunsuke; Ito, Satoshi*; Mitarai, Osamu*; Naito, Osamu; Ozeki, Takahisa; Sakamoto, Yoshiteru; Suzuki, Takahiro; Takase, Yuichi*; Tanaka, Shigetoshi*; et al.

Physical Review Letters, 92(3), p.035001_1 - 035001_4, 2004/01

 Times Cited Count:39 Percentile:17.14(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Research activities on Tokamaks in Japan; JT-60U, JFT-2M and TRIAM-1M

Ninomiya, Hiromasa; Kitsunezaki, Akio; Shimizu, Masatsugu; Kuriyama, Masaaki; JT-60 Team; Kimura, Haruyuki; Kawashima, Hisato; Tsuzuki, Kazuhiro; Sato, Masayasu; Isei, Nobuaki; et al.

Fusion Science and Technology, 42(1), p.7 - 31, 2002/07

 Times Cited Count:12 Percentile:75.76(Nuclear Science & Technology)

In order to establish scientific basis for the sustainment of highly integrated performance required in the advanced steady-state operation, JT-60U has been optimizing the discharge control scenarios of improved confinement plasmas and expanding the operation regions. Promising results toward the steady-state tokamak were obtained. The detail of such results is reported. JFT-2M has performed advanced and basic research for the development of high performance tokamak plasma as well as the structural material for a fusion reactor. The toroidal ripple reduction with ferritic steel plates outside the vacuum vessel was successfully demonstrated. No adverse effects were observed in the pre-testing on compatibility between ferritic steel plates, covering ~20% of the inside wall of the vacuum vessel, and plasma. The results of TRIAM-1M is also reported.

Oral presentation

Influence of nitrite ion on oxidation of vanadium in nitric acid solution

Irisawa, Eriko; Ueno, Fumiyoshi; Abe, Hitoshi; Kumagai, Mikio*; Suzuki, Kazunori*; Hayashi, Shinichiro*

no journal, , 

no abstracts in English

Oral presentation

Relation between redox reaction of vanadium and nitrogen oxide in nitric acid solution

Irisawa, Eriko; Suzuki, Kazunori*; Kumagai, Mikio*; Kato, Chiaki; Ueno, Fumiyoshi; Abe, Hitoshi

no journal, , 

For the corrosion of stainless steels in the nitric acid solution containing oxidizing metallic ions, it is important factor that the relation between re-oxidation of metallic ions which is reduced with the corrosion reaction and the redox reaction of nitric acid. To make clear the effect of nitrogen oxides formed from nitric acid on oxidation behavior of tetravalent vanadium, changing of concentrations of nitrogen oxide discharged to gas phase from solution and nitrous acid in solution during oxidation reaction of vanadium were measured. The results showed that the nitrogen dioxide acted as oxidant on the oxidation reaction of vanadium.

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

Experimental studies on Cs chemisorption on reactor structural materials and their re-vaporization behavior

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

no journal, , 

In order to clarify the re-vaporization behavior of caesium (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

Chemical state of adsorbed Cesium under LWR severe accident studied by hard X-ray photoelectron spectroscopy

Kobata, Masaaki; Okane, Tetsuo; Kobayashi, Keisuke*; Owada, Kenji*; Nakajima, Kunihisa; Suzuki, Eriko; Osaka, Masahiko

no journal, , 

To understand the chemisorption behavior of Cesium (Cs) under an LWR severe accident, we have studied the Cs chemisorbed surfaces of the simulation samples (stainless steel) by hard X-ray photoelectron spectroscopy (HAXPES). It was found that the chemical states of Cs adsorbed on the sample surface were varied in dependence upon a silicon concentration of sample.

Oral presentation

Fundamental research on fission product chemistry, 5; On the release and transportation behavior of strontium under an LWR severe accident

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

no journal, , 

The effects of atmosphere on the release and transport behavior of strontium (Sr) in the light water reactor severe accident (SA) was discussed based on the results calculated by release model which can evaluate the influence of atmosphere and the chemical equilibrium calculation. Under the steam starvation atmosphere condition, there is possibility that non-volatile Sr in the steam atmosphere is significantly released from fuel, while the amount of transport into the primary containment vessel is suppressed.

Oral presentation

Fundamental research on fission product chemistry, 3; Effect of atmosphere on the vaporization behavior of CsFeSiO$$_{4}$$

Suzuki, Eriko; Nakajima, Kunihisa; Osaka, Masahiko

no journal, , 

In severe accident condition, CsFeSiO$$_{4}$$ could be formed by Cesium(Cs) chemisorption onto reactor structural materials. For evaluation of re-vaporization behavior, effect of atmosphere on the vaporization behavior of CsFeSiO$$_{4}$$ at high temperature was investigated by TG-DTA experiments. As a result, it was found that vaporization of CsFeSiO$$_{4}$$ in atmosphere containing H$$_{2}$$ was promoted more than those in air and in Ar(inert) atmosphere.

52 (Records 1-20 displayed on this page)