Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Yamazaki, Saishun; Pshenichnikov, A.; Pham, V. H.; Nagae, Yuji; Kurata, Masaki; Tokushima, Kazuyuki*; Aomi, Masaki*; Sakamoto, Kan*
Proceedings of Annual Topical Meeting on Reactor Fuel Performance (TopFuel 2018) (Internet), 8 Pages, 2018/10
It is predictively evaluated that degradation of fuel assembly proceeded in a certain steam-starved condition at the early stage of a SA at 1F unit 2 (BWR). As for PWR fuel assembly, effective steam flow rate was properly indicated by normalizing to a unit of g-H
O/sec/rod which is used as an important parameter for evaluating fuel degradation progression. Due to the inhomogeneous configuration of BWR fuel assembly, the difference of Zry oxidation and hydrogen uptake between the inside and outside of the channel box cannot be properly evaluated by this normalization. Instead of g-HO/sec/rod, proper evaluation unit for BWR configuration is necessary. To accumulate Zry oxidation and hydrogen uptake data for steam-starved conditions, high temperature oxidation tests were performed using a simulated BWR fuel bundle sample. The use of equivalent diameter of the cross section of BWR fuel assembly was proposed for normalization of effective steam flow rate.
Yamashita, Susumu; Tokushima, Kazuyuki*; Kurata, Masaki; Yoshida, Hiroyuki
Mechanical Engineering Journal (Internet), 4(3), p.16-00567_1 - 16-00567_13, 2017/06
In order to precisely investigate molten core relocation behavior in severe accidents, we have been developing the detailed and phenomenological numerical simulation code named JUPITER for predicting the molten core behavior with melting and solidification based on computational fluid dynamics (CFD) including the three-dimensional multiphase thermal-hydraulic simulation models. In order to treat complicated core structures, e.g., boron carbide (absorber), stainless steel (control rod, fuel support structure, etc.), Zircaloy (channel box and fuel cladding) and to deal with complicated melt relocation behaviors, high accuracy, efficient, stable and robust numerical schemes are implemented. In this paper, in order to evaluate the validity and applicability of the JUPITER for actual core structures, we perform the preliminary melt relocation analysis in the control rod and fuel support piece and also verify the validity of the JUPITER regarding the melt relocation and solidification processes by the fundamental numerical problem and the experimental analysis. As a result, the preliminary analysis showed that multicomponent melt flow and its melt and solidification were stably worked in the melt relocation simulation. In the validation analysis, the numerical results were in the reasonably agreement with experimental results. Therefore, it was confirmed that the JUPITER has a potential to calculate the core melt relocation behavior in RPVs.
Shibata, Hiroki; Tokushima, Kazuyuki; Sakamoto, Kan*; Kurata, Masaki
Proceedings of Annual Topical Meeting on LWR Fuels with Enhanced Safety and Performance (TopFuel 2016) (USB Flash Drive), p.1033 - 1042, 2016/09
To understand the degradation process of control blade channel, control blade degradation tests using sim-materials were performed under various atmospheres with the temperature increase and temperature gradient conditions. In the steam atmosphere with a flow rate of 0.0125 g/s/rod, control blade, channel box, and fuel rods were degraded, especially at the upper part of the test piece, which was similar to that observed in argon atmosphere test. However, the observed degradation was rather different at a flow rate of 0.0417 g/s/rod. At the upper part of the test piece, only the control blade was degraded preferentially and did not react with channel box wall. In contrast, the eutectic reaction of S.S./B
C-melt and Zry occurred at the lower part. These observations suggested the existence of a threshold condition for the control rod degradation between 0.0125 and 0.0417 g/s/rod which is significantly affected by the thickness of the oxide layer on Zry.
Tokushima, Kazuyuki; Shirasu, Noriko; Hoshino, Kuniyoshi*; Ohara, Hiroshi*; Kurata, Masaki
Proceedings of Annual Topical Meeting on LWR Fuels with Enhanced Safety and Performance (TopFuel 2016) (USB Flash Drive), p.1055 - 1063, 2016/09
At the fuel assembly degradation stage in severe accidents, chemical features of the intermediate products are expected to be changed depending upon the accident progressions. These differences are originated from the differences in oxygen potential and temperature, and are highly important for evaluating the relocation and stratification progress of the fuel debris. Two types of sim-test with the different oxygen potentials were performed to investigate these tendencies. The chemical features of the intermediate materials used in the tests were determined from the observations for the control blade and channel box degradation in our previous study. The present results indicate that the U concentration in the metallic layer is largely varied depending upon the oxygen potential of the atmosphere. Also, when the BC-Fe alloy, as of a typical intermediate product, coexists with UO and Zr, the apparent red-ox reaction rate between UO and Zr are mitigated.
Yamashita, Susumu; Tokushima, Kazuyuki; Kurata, Masaki; Takase, Kazuyuki; Yoshida, Hiroyuki
Proceedings of 24th International Conference on Nuclear Engineering (ICONE-24) (DVD-ROM), 5 Pages, 2016/06
In order to precisely investigate molten core relocation behavior in the Fukushima Daiichi Nuclear Power Station, we have developed the detailed and phenomenological numerical simulation code named JUPITER for predicting the molten core behavior including solidification and relocation based on the three-dimensional multiphase thermal-hydraulic simulation models. At the moment, multicomponent analysis method which can be treated any number of component as a fluid or solid body, Zr-water reaction model and simple radiation heat transfer model were implemented and showed that multicomponent melt flow and its solidification were confirmed in the simplified core structure system. However, the validation of the JUPITER using high temperature molten material has not been performed yet. In this paper, in order to evaluate the validity of the JUPITER, especially, for high temperature melt relocation experiment, we compared between numerical and experimental results for that system. As a result, qualitatively reasonable result was obtained. And also we performed melt relocation simulation on actual core structures designed by three dimensional CAD (Computer-Aided Design) and then we estimated phenomena which might be actually occurred in SAs.
Yamashita, Susumu; Tokushima, Kazuyuki; Kurata, Masaki; Takase, Kazuyuki; Yoshida, Hiroyuki
Nihon Kikai Gakkai Dai-28-Kai Keisan Rikigaku Koenkai Rombunshu (CD-ROM), 3 Pages, 2015/10
no abstracts in English
Tokushima, Kazuyuki; Shibata, Hiroki; Kurata, Masaki; Sawada, Akihiko*; Sakamoto, Kan*
Annual Topical Meeting on Reactor Fuel Performance (TopFuel 2015), Conference Proceedings, Poster (Internet), p.478 - 485, 2015/00
Two type tests were performed to examine the prevention effect of the oxide layers to liquefaction interaction between Zircaloy and core component materials. The oxide layer of Zircaloy was clearly confirmed to prevent the liquefaction interaction under the temperature of melting point of stainless steel even if the oxide layer on Zircaloy of approximately 30 micro meters, which is thinner than it is predicted to be formed under typical accident condition. The oxide layers were able to be formed even in the region where the gas flow is significantly limited by narrow arrangement. Although the oxide layers at the inner position of upper end plug was hard to form, the prevention effect of the oxide layers was sufficiently observed. The axial variation of the thickness of the oxide layers was observed. It suggested that variation of partial pressure of HO should be considered to evaluate the growth rate of the oxide layers for detail.
Tanaka, Kosuke; Tokushima, Kazuyuki*; Kurosaki, Ken*; Oishi, Yuji*; Muta, Hiroaki*; Yamanaka, Shinsuke*
Journal of Nuclear Materials, 443(1-3), p.218 - 221, 2013/11
Times Cited Count：0 Percentile：0.01(Materials Science, Multidisciplinary)Polycrystalline specimens of barium uranate, BaUO, were prepared and several properties such as the thermal expansion coefficient, elastic moduli, thermal conductivity, and Debye temperature were evaluated.
-O ( = Mo or U) ternary compoundsTokushima, Kazuyuki*; Tanaka, Kosuke; Kurosaki, Ken*; Gima, Hiromichi*; Muta, Hiroaki*; Uno, Masayoshi*; Yamanaka, Shinsuke*
Materials Research Society Symposium Proceedings, Vol.1215, p.151 - 156, 2010/10
The thermal diffusivities of CsMoO and CsUO using samples fabricated by hot press and SPS techniques were measured by a laser flash method in the range from room temperature to 823 K for CsMoO and to 900 K for CsUO. The thermal conductivities of these cesium ternary oxides were quite low compared with UO and MOX fuel. This is consistent with previous findings. These results would be useful for evaluating the thermal performance of MOX fuels at the high burn-up region in the fast reactors.
Tanaka, Kosuke; Osaka, Masahiko; Kurosaki, Ken*; Tokushima, Kazuyuki*; Muta, Hiroaki*; Yamanaka, Shinsuke*; Uno, Masayoshi*
no journal, ,
In order to evaluate the performance of MA-containing MOX fuels up to high burn-up region, chemical forms of fission products were determined by using equilibrium calculation.
Tanaka, Kosuke; Sato, Isamu; Hirosawa, Takashi; Seki, Takayuki*; Kashimura, Naoki*; Kurosaki, Ken*; Tokushima, Kazuyuki*; Muta, Hiroaki*; Oishi, Yuji*; Yamanaka, Shinsuke*
no journal, ,
Complex uranium or plutonium oxides with alkaline-earth metals were prepared by using conventional powder metallurgy and its thermophysical properties were evaluated.
Yamashita, Susumu; Tokushima, Kazuyuki; Yoshida, Hiroyuki; Kurata, Masaki
no journal, ,
To simulate each process of the core melt progression in detail and contribute the improvement of severe accident analysis codes, we have performed the melt relocation experiments by using simplified fuel support pieces of the BWR. In addition, we are developing a numerical simulation code, JUPITER, to simulate the melt relocation in a fuel assembly scale. In this study, the JUPITER was applied to numerical simulations of the melt behavior of the complicated fuel support structures and the melt relocation experiment. As a result, the JUPITER is able to simulate melt relocation behavior in the complicated structures stably, and showed good agreement with the experimental results qualitatively. Therefore, it was confirmed that the JUPITER has potential to provide accurate understanding of the melt relocation behavior. In the near future, in order to simulate the more realistic behavior of the melt relocation, we will implement the eutectic reaction model to the JUPITER and also proceed the experimental analysis.
Shibata, Hiroki; Tokushima, Kazuyuki; Sakamoto, Kan*; Kurata, Masaki
no journal, ,
In this study, control blade degradation test under the conditions of axial temperature gradient and high temperature increase rate in Ar-atmosphere was performed as preliminary test in steam atmosphere to investigate the relocation of control blade melt and interaction with channel box under the conditions. It was found that the molten products redistribute to axial direction and interaction between S.S./B
C-melt and Zry-4 progresses significantly in the condition that a few micron oxide layer exists on Zry-4. Moreover, as preliminary test in steam atmosphere, reaction test between the materials of control blade and channel box was carried out to investigate the effect of oxide layer formed on the surface of Zry-4 in steam atmosphere. It was found that in the condition of supplying oxygen continuously, the liquefaction interaction between Zry and S.S./BC-melt is considered to be prevented.
Tokushima, Kazuyuki; Shirasu, Noriko; Hoshino, Kuniyoshi*; Ohara, Hiroshi*; Kurata, Masaki
no journal, ,
At the fuel assembly degradation stage in severe accidents, chemical features of the intermediate products are expected to be changed depending upon the accident progressions. These differences are originated from the differences in oxygen potential and temperature, and are highly important for evaluating the relocation and stratification progress of the fuel debris. Two types of sim-test with the different oxygen potentials were performed to investigate these tendencies. The chemical features of the intermediate materials used in the tests were determined from the observations for the control blade and channel box degradation in our previous study. The present results indicate that the U concentration in the metallic layer is largely varied depending upon the oxygen potential of the atmosphere. Also, when the BC-Fe alloy, as of a typical intermediate product, coexists with UO and Zr, the apparent red-ox reaction rate between UO and Zr are mitigated.
Yamazaki, Saishun; Pshenichnikov, A.; Nagae, Yuji; Kurata, Masaki; Sakamoto, Kan*; Tokushima, Kazuyuki*; Aomi, Masaki*
no journal, ,
no abstracts in English
