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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

Development of evaluation method for aerosol particle deposition in a reactor building based on CFD

Horiguchi, Naoki; Miyahara, Naoya; Uesawa, Shinichiro; Yoshida, Hiroyuki; Osaka, Masahiko

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05

For source term evaluation from reactor buildings (RBs) in LWR severe accidents, we have launched to develop an evaluation method of FP aerosol particle deposition onto surfaces of internal structures in an RB based on computational fluid dynamics (CFD). This paper describes development of a CFD simulation tool as the base part of the evaluation method. A preliminary simulation for a representative RB under a representative flow condition was conducted to confirm the tool performance by roughly grasping the deposition behaviors of FP aerosol particle and decontamination factor (DF) in the RB. Calculation results showed that most of aerosol particles were deposited along with gas flow formed by the internal structures in the RB, demonstrating the advantageous feature of the present CFD tool. The DFs from 4 to 14 were obtained with increase of the particle diameters from 0.1 to 10 $$mu$$m as expected in terms of the particle movement equation.

Journal Articles

Observation of aerosol particle behavior near gas-liquid interface

Uesawa, Shinichiro; Miyahara, Naoya; Horiguchi, Naoki; Yoshida, Hiroyuki; Osaka, Masahiko

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 5 Pages, 2019/05

Journal Articles

Chemical reaction kinetics dataset of Cs-I-B-Mo-O-H system for evaluation of fission product chemistry under LWR severe accident conditions

Miyahara, Naoya; Miwa, Shuhei; Horiguchi, Naoki; Sato, Isamu*; Osaka, Masahiko

Journal of Nuclear Science and Technology, 56(2), p.228 - 240, 2019/02

 Percentile:100(Nuclear Science & Technology)

In order to improve LWR source term under severe accident conditions, the first version of a fission product (FP) chemistry database named "ECUME" was developed. The ECUME is intended to include major chemical reactions and their effective kinetic constants for representative SA sequences. It is expected that the ECUME can serve as a fundamental basis from which FP chemical models in the SA analysis codes can be elaborated. The implemented chemical reactions in the first version were those for representative gas species in Cs-I-B-Mo-O-H system. The chemical reaction kinetic constants were evaluated from either literature data or calculated values using ab-initio calculations. The sample chemical reaction calculation using the presently constructed dataset showed meaningful kinetics effects at 1000 K. Comparison of the chemical equilibrium compositions by using the dataset with those by chemical equilibrium calculations has shown rather good consistency for the representative Cs-I-B-Mo-O-H species. From these results, it was concluded that the present dataset should be useful to evaluate FP chemistry in Cs-I-B-Mo-O-H system under LWA SA conditions.

Journal Articles

Development of numerical simulation method for small particles behavior in two-phase flow by combining interface and Lagrangian particle tracking methods

Yoshida, Hiroyuki; Uesawa, Shinichiro; Horiguchi, Naoki; Miyahara, Naoya; Ose, Yasuo*

Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 6 Pages, 2018/11

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

Development of numerical simulation method for capturing behavior of aerosol particles on gas-liquid interface based on interface tracking method

Yoshida, Hiroyuki; Uesawa, Shinichiro; Horiguchi, Naoki; Miyahara, Naoya; Ose, Yasuo*

Dai-23-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (USB Flash Drive), 5 Pages, 2018/06

no abstracts in English

Journal Articles

Observation of capturing behavior of aerosol particles on gas-liquid interface

Uesawa, Shinichiro; Horiguchi, Naoki; Miyahara, Naoya; Yoshida, Hiroyuki

Dai-23-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (USB Flash Drive), 5 Pages, 2018/06

no abstracts in English

Journal Articles

Development of experimental and analytical technologies for fission product chemistry under LWR severe accident condition

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

Proceedings of 2017 Water Reactor Fuel Performance Meeting (WRFPM 2017) (USB Flash Drive), 9 Pages, 2017/09

This paper presents the development of a reproductive experimental setup for FP release and transport and an analysis tool considering chemical reaction kinetics for the construction of the FP chemistry database. The performance test of the reproductive experimental setup TeRRa using CsI compounds show that TeRRa can reproduce well a FP chemistry-related behavior such as aerosol formation, growth and deposition behavior. An analytical tool has been developed based on the commercial ANSYS-FLUENT code. Some additional models was added to evaluate detailed FP chemistry during release and transport in this study. A test analysis simulating the CsI heating test in steam atmosphere was carried out to demonstrate the performance of the improved code. The result shows the appropriateness of the additional models.

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.

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, 1; Basic performance of the reproductive test facility of fission product release and transport (TeRRa)

Miyahara, Naoya; Miwa, Shuhei; Takada, Juntaro; Osaka, Masahiko

no journal, , 

A test facility for the reproduction of fission poroduct release and transport under a severe accident condition has been developed. It was confirmed that not only deposited but also airborne materials in the farnace of this facility under temperature condition of severe accident (1000 - 400 K at reactor coolant system) can be subjected to various analyses by measuring aerosol size distribution of airborne CsI aerosol.

Oral presentation

Results and progress of fundamental research on FP chemistry

Osaka, Masahiko; Nakajima, Kunihisa; Miwa, Shuhei; Miyahara, Naoya; Suzuki, Eriko; Suzuki, Chikashi; Horiguchi, Naoki; Imoto, Jumpei; Liu, J.; Nishioka, Shunichiro; et al.

no journal, , 

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.

Oral presentation

Fundamental research on fission product chemistry, 3; Effect of chemical reaction kinetics on the chemical forms of iodine and cesium vapor species

Horiguchi, Naoki; Miyahara, Naoya; Miwa, Shuhei; Osaka, Masahiko

no journal, , 

To evaluate chemical behavior of Iodine and Cesium at reactor cooling system in Boron containing environment derived from BWR control materials, a chemical analysis considering chemical reaction kinetic was conducted. Analytical results were compared with those by a chemical equilibrium calculation. It was found that mole fractions of main Cesium compound CsBO$$_{2}$$ were different between those calculated with and without chemical reaction kinetics in a lower temperature condition. This result indicates the necessity of consideration of the chemical reaction kinetic model for the evaluation of the chemical behavior of Iodine and Cesium.

Oral presentation

Fundamental research on fission product chemistry, 2; Evaluation of oxidation and vaporization behavior of ruthenium and molybdenum alloys in a nuclear fuel

Liu, J.; Miyahara, Naoya; Miwa, Shuhei; Takano, Masahide; Osaka, Masahiko

no journal, , 

For a more accurate evaluation of Ru and Mo release behavior from their alloys formed in a nuclear fuel under severe accident conditions, Ru and Mo oxidation and vaporization behaviors were investigated by thermogravimetric-differential thermal analysis (TG-DTA). The results show the oxidation and vaporization rates of Mo powders are much higher than that of Ru powders. The vaporization rates of Ru powders are controlled by the equilibrium RuO$$_{3}$$ vapor pressure.

Oral presentation

Fundamental research on fission product chemistry, 4; Evaluation of Boron chemical behavior during transport in reactor coolant system

Miwa, Shuhei; Miyahara, Naoya; Horiguchi, Naoki; Imoto, Jumpei; Nakajima, Kunihisa; Osaka, Masahiko

no journal, , 

The chemical behavior of boron compounds such as chemical reaction and condensation during their transport in a reactor coolant system under severe accident conditions was estimated considering effects of Boron release kinetics from control blade melts and atmosphere for evaluation of boron effects on the cesium and iodine chemistry. The most of boron is transported as boric acid to the lower temperature region of a reactor coolant system in steam atmosphere. On the other hand, the release of boron from control blade is suppressed in steam-starvation atmosphere due to the formation of stable iron borate, and the chemical forms of boron during transport becomes boron oxide and cesium borate, which lead to a suppression of transport to the lower temperature region due to their condensation at higher temperature.

Oral presentation

Development of the evaluation method for the aerosol deposition amounts in the containment vessel and the reactor building, 1; Effect of surface materials on the aerosol deposition behavior

Miyahara, Naoya; Suzuki, Eriko; Uesawa, Shinichiro; Sato, Isamu*; Matsuura, Haruaki*; Hagura, Naoto*; Koshigoe, Hiroki*; Osaka, Masahiko

no journal, , 

We have started the fundamental research on detailed aerosol deposition phenomena at the walls of containment vessel and reactor building to develop a reasonable evaluation model of aerosol deposition amount which have a large influence on release amount to the environment. In this study, an aerosol deposition test onto various materials was conducted to investigate the physical and chemical phenomena related to aerosol deposition. As a result, important phenomena such as aerosol penetration into concrete pore were observed, which should be considered in the aerosol deposition model.

Oral presentation

FP chemistry in a high temperature region of LWR under a severe accident, 1; Boron transport behavior in a reactor coolant system

Miwa, Shuhei; Imoto, Jumpei; Miyahara, Naoya; Osaka, Masahiko

no journal, , 

BWR control material, boron, would influence the transport behavior of fission product (FP) such as cesium in a reactor coolant system under LWR severe accident. Thus the boron transport behavior was experimentally investigated by using Test bench for FP release and transport (TeRRa). The analysis results of deposits show that changes in weight of tube increase above 900 K and around 700 K, which would be attributed to chemical reaction with stainless steel and condensation of boron vapor onto stainless tubes, respectively. From these results, it is concluded that the released boron vapor would react with stainless steel and condense in the temperature range of reactor coolant system.

Oral presentation

FP chemistry in a high temperature region of LWR under a severe accident, 6; Improvement of ruthenium release model from a nuclear fuel under a LWR severe accident

Liu, J.; Miyahara, Naoya; Miwa, Shuhei; Takano, Masahide; Osaka, Masahiko

no journal, , 

To improve the ruthenium (Ru) release model from a nuclear fuel in a severe accident, we investigated the oxidation and vaporization behaviors of Ru from Mo$$_{0.231}$$Ru$$_{0.558}$$Pd$$_{0.088}$$Rh$$_{0.123}$$ alloy powders, and derived the activity coefficient of Ru in Ru$$_{0.725}$$Pd$$_{0.115}$$Rh$$_{0.160}$$ alloy as 1.19.

41 (Records 1-20 displayed on this page)