Refine your search:     
Report No.
 - 
Search Results: Records 1-18 displayed on this page of 18
  • 1

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

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:2 Percentile:69.68

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

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.

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:15 Percentile:90.26(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

Boron effects on fission product behavior under severe accident conditions

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

Proceedings of Annual Topical Meeting on LWR Fuels with Enhanced Safety and Performance (TopFuel 2016) (USB Flash Drive), p.861 - 868, 2016/09

The basic studies have been performed for the evaluation of boron (B) release from the degraded BWR control rod material and its effect on cesium (Cs) and iodine (I) chemistry during a severe accident. The B effect on Cs and I chemistry was evaluated by thermal equilibrium calculation considering the change in B release behavior under the degradation of BWR control rod material. Results shows that The generation of gaseous iodine as well as CsBO$$_{2}$$ could be suppressed under a steam-starvation atmosphere because of a lower B release fraction owing to the possible formation of stable iron Fe-B alloys. In response to this prediction result, the basic experiments and analyses are underway. The B release behavior from the boron carbide/stainless steel/Zircaloy reaction products, the thermochemical properties and phase states of complex Cs-B-O compounds are being studied. For the validation of all these evaluation results, reproductive test for FP release and transport will be performed.

Journal Articles

Surface analyses of cesium hydroxide chemisorbed onto type 304 stainless steel

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

Nuclear Engineering and Design, 305, p.411 - 420, 2016/08

 Times Cited Count:18 Percentile:91.61(Nuclear Science & Technology)

Chemisorption is of main importance during a Severe Accident (SA) at a light water reactor, as it can influence fission products retention in the reactor vessel. Information on the distribution, composition and properties of such deposits can influence the decommissioning practice after a SA. Moreover such information can enhance the description of the chemisorption models applied in SA codes, consequently improving the source term assessment. This paper will present the results obtained from CsOH chemisorption experiments onto type 304 stainless steel samples, used as simulants of reactor structural materials. The samples post-analyses showed that CsOH will absorb onto the surface, reacting preferentially with Si impurities and forming a newly detected compound, CsFeSiO$$_{4}$$. From our results, it can be inferred that Si content in structural materials can determine the amount of radioactive Cs deposited onto the reactor vessel after a SA.

JAEA Reports

Boron release kinetics from mixed melts of boron carbide, stainless steel and Zircaloy; A Literature review on the behavior of control rod materials under severe accidents

Di Lemma, F. G.; Miwa, Shuhei; Osaka, Masahiko

JAEA-Review 2016-007, 27 Pages, 2016/03

JAEA-Review-2016-007.pdf:1.88MB

During a nuclear power plant Severe Accident, complex boron melts can be formed, due to interaction of the control rods with the cladding materials. These can affect ultimately the source term assessment. This review will describe the results of previous studies on boron carbide/stainless steel/Zircaloy (B$$_{4}$$C/SS/Zry) melts, which will finally provide guidance for the needs of future experiments. This review showed that models for the behavior of complex B$$_{4}$$C/SS/Zry melts are limited, and unsuccessful in simulating core degradation, thus the improvement of the database for B$$_{4}$$C/SS/Zry melts is needed. Our experimental plan aims in providing thermodynamics and kinetics models for such melts, with the final aim of improving boron modelling in SA codes analysis and of understanding its effect on fission products behavior.

Oral presentation

Fundamental research on fission product chemistry under a severe accident

Miwa, Shuhei; Nakajima, Kunihisa; Di Lemma, F. G.; Suzuki, Chikashi; Yamashita, Shinichiro; Okane, Tetsuo; Takai, Toshihide; Takada, Juntaro; Furukawa, Tomohiro; Osaka, Masahiko

no journal, , 

JAEA conducts a fundamental research on fission product (FP) chemistry to construct the database of FP chemistry at each stage of nuclear power plants and improve FP chemistry models which will be reflected to the improvement of FP release and transport models. Main target of FP elements are Cs and I, and the evaluation of FP and B release kinetics, development of direct measurement technique of FP chemical form, the evaluation of Cs chemisorption behavior to SS, upgrading the thermodynamic database are carried out with focuses on Mo and BWR control material, boron carbide (B$$_{4}$$C).

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

Fission products chemisorption mechanism following severe accidents; A Separate effect study on CsOH reaction with stainless steel

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

no journal, , 

Fission products chemisorption on reactor structural materials is an important phenomenon to be considered following an accident, as it can lead to retention of fission products in the containment, affecting the radioactive release to the environment and reactor decommissioning. The knowledge acquired from this study could help improve the models for cesium(Cs) chemisorption and could be applied to evaluate the distribution and properties of Cs deposits in the Fukushima-Daiichi Nuclear Power Plant, providing guidance for its decommissioning. Our studies were performed vaporizing CsOH over stainless steel samples, varying experimental parameters, such as temperature (800-1000$$^{circ}$$C) and atmosphere (H$$_{2}$$/Ar, H$$_{2}$$/H$$_{2}$$O/Ar). Sample surfaces were analyzed by SEM/EDX, XRD to evaluate the deposit microstructure and chemical composition. The EDX characterization results demonstrate a congruent distribution between Cs and Si, and the XRD patterns indicate the formed Cs compound as CsFeSiO$$_{4}$$. These results show the importance of the presence of impurities in stainless steel, affecting the formation of stable Cs deposits.

Oral presentation

Investigation of cesium chemisorption behavior on the stainless steel surface

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

no journal, , 

Knowledge of accurate Cs-deposition properties is essential to evaluate radiation dose of workers at the Fukushima Daiichi Nuclear Power Plants (1F-NPPs), encountered during retrieval of fuel debris from the radioactive Cs deposits onto structural materials and equipments in the RPV and PCV. The Cs chemisorption tests were performed to investigate its behavior on stainless steels. As the results, we observed that Cs congruently distributes with silicon (Si), which agrees with previous studies. But the results of the XRD and EDS analyses suggest that the reaction product is not Cs$$_{2}$$Si$$_{4}$$O$$_{9}$$ but a new proposed compound CsFeSiO$$_{4}$$. Further, it was suggested from our XRD analysis and leaching test that the amounts of the Cs deposit at 800$$^{circ}$$C were higher than those of the Cs deposit at 1000$$^{circ}$$C, though the previous studies indicated the reaction rate increased monotonously up to 1000$$^{circ}$$C.

Oral presentation

Behavior of fission products in Fukushima Daiichi NPP under severe accidents overview of FP behavior under accidents and approaches toward advanced source term analysis, 4; Fundamental aspects of FP behavior and challenge toward further research subjects

Osaka, Masahiko; Miwa, Shuhei; Nakajima, Kunihisa; Di Lemma, F. G.; Suzuki, Chikashi; Nagase, Fumihisa

no journal, , 

Chemical behavior of fission product (FP) are of crucial importance for the improvement of FP release and transport behavior under the severe accident. Fundamental research on FP sorption behavior and evaluation of FP chemical composition in the reactor are introduced.

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

Oral presentation

Synthesis of CeO$$_{2}$$ based simulated fuel containing CsI to evaluate the release behavior of Cs and I

Takamatsu, Yuki*; Kurosaki, Ken*; Ishii, Hiroto*; Osaka, Masahiko; Nakajima, Kunihisa; Miwa, Shuhei; Di Lemma, F. G.; Oishi, Yuji*; Muta, Hiroaki*; Yamanaka, Shinsuke*

no journal, , 

We performed spark plasma sintering tests of the cerium dioxide (CeO$$_{2}$$)-based simulated fuel containing cesium iodide (CsI) for the establishment of synthesis technology of simulated fuel containing volatile fission product (FP) such as cesium (Cs) and iodine (I) which is required for the data acquisition on the FP release behavior. We could successfully fabricate the simulated fuel containing CsI, which had homogeneous distribution of CsI compound, by the spark plasma sintering at lower temperature and in shorter time.

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

Fundamental research on fission product chemistry, 1; Evaluation of oxidation and vaporization behavior of Boron compound formed in molten control rod blade

Imoto, Jumpei; Di Lemma, F. G.*; Miwa, Shuhei; Takano, Masahide; Osaka, Masahiko

no journal, , 

In order to investigate the Boron (B) release behavior from a Fe-B compounds formed in the melt of BWR control blade under a severe accident, a thermal analysis on a synthesized Fe-B sample was performed to evaluate the oxidation and vaporization behavior. It was found that the oxidation rate of the Fe-B compound was several magnitude of order lower than that of B$$_{4}$$C. This result support the previous report that the vaporization of B through the main release path of the oxidation product B$$_{2}$$O$$_{3}$$ is suppressed by the formation of Fe-B-O compounds in the case of Fe-B compounds.

18 (Records 1-18 displayed on this page)
  • 1