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Journal Articles

Study on loss-of-cooling and loss-of-coolant accidents in spent fuel pool; Confirmation of fuel temperature calculation function with oxidation reaction in the SAMPSON code

Suzuki, Hiroaki*; Morita, Yoshihiro*; Naito, Masanori*; Nemoto, Yoshiyuki; Kaji, Yoshiyuki

Mechanical Engineering Journal (Internet), 7(3), p.19-00450_1 - 19-00450_17, 2020/06

In this study, the SAMPSON code was modified to evaluate severe accidents in a spent fuel pool (SFP). Air oxidation models based on oxidation data obtained on the Zircaroy-4 cladding (ANL model) and the Zircaroy-2 cladding (JAEA model) were included in the modified SAMPSON code. Experiments done by Sandia National Laboratory using simulated fuel assemblies equivalent to those of an actual BWR plant were analyzed by the modified SAMPSON code to confirm the functions for analysis of the severe SFP accidents. The rapid fuel rod temperature rise due to the Zr air oxidation reaction could be reasonably evaluated by the SAMPSON analysis. The SFP accident analyses were conducted with different initial water levels which were no water, water level at bottom of active fuel, and water level at half of active fuel. The present analysis showed that the earliest temperature rise of the fuel rod surface occurred when there was no water in the SFP and natural circulation of air became possible.

Journal Articles

Study on loss-of-cooling and loss-of-coolant accidents in spent fuel pool, 4; Investigation of fuel loading effects in BWR spent fuel rack

Tojo, Masayuki*; Kanazawa, Toru*; Nakashima, Kazuo*; Iwamoto, Tatsuya*; Kobayashi, Kensuke*; Goto, Daisuke*; Nemoto, Yoshiyuki; Kaji, Yoshiyuki

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 13 Pages, 2019/05

In this study, fuel loading effects in BWR spent fuel rack accidents are widely investigated using three-dimensional analysis methods from both nuclear and thermal hydraulics viewpoints, including: (a) Decay heat of spent fuel after discharge, (b) The maximum temperature of spent fuel cladding in the spent fuel rack depending on heat transfer phenomena, and (c) Criticality of the spent fuel rack after collapsing of the fuel due to a severe accidents in the BWR spent fuel pool (SFP).

Journal Articles

Creep damage evaluations for BWR lower head in severe accident

Katsuyama, Jinya; Yamaguchi, Yoshihito; Nemoto, Yoshiyuki; Kaji, Yoshiyuki; Osaka, Masahiko

Transactions of 24th International Conference on Structural Mechanics in Reactor Technology (SMiRT-24) (USB Flash Drive), 11 Pages, 2017/08

It is difficult to assess rupture behavior of the lower head of reactor pressure vessel in boiling-water-type nuclear power plants due to severe accident like Fukushima Daiichi because Boiling Water Reactor (BWR) lower heads have geometrically complicated structure with a lot of penetrations. Therefore, we have been developing an analysis method to predict time and location of RPV lower head rupture of BWRs considering creep damage mechanisms based on coupled analysis of three-dimensional Thermal-Hydraulics (TH) and thermal-elastic-plastic-creep analyses. In this study, we performed creep damage evaluations to investigate the effects of the debris depth and heat generation locations on failure behavior of lower head. From the analysis results, we discussed the outflow paths of the relocated molten core to the containment, and it was concluded that failure regions of BWR lower head are only the control rod guide tubes or stub tubes under simulated conditions.

Journal Articles

Investigation of Zircaloy-2 oxidation model for SFP accident analysis

Nemoto, Yoshiyuki; Kaji, Yoshiyuki; Ogawa, Chihiro; Kondo, Keietsu; Nakashima, Kazuo*; Kanazawa, Toru*; Tojo, Masayuki*

Journal of Nuclear Materials, 488, p.22 - 32, 2017/05

AA2016-0383.pdf:0.86MB

 Times Cited Count:1 Percentile:80.48(Materials Science, Multidisciplinary)

The authors previously conducted thermogravimetric analyses on zircaloy-2 in air. By using the thermogravimetric data, an oxidation model was constructed in this study so that it can be applied for the modeling of cladding degradation in spent fuel pool (SFP) severe accident condition. For its validation, oxidation tests of long cladding tube were conducted, and computational fluid dynamics analyses using the constructed oxidation model were proceeded to simulate the experiments. In the oxidation tests, high temperature thermal gradient along the cladding axis was applied and air flow rates in testing chamber were controlled to simulate hypothetical SFP accidents. The analytical outputs successfully reproduced the growth of oxide film and porous oxide layer on the claddings in oxidation tests, and validity of the oxidation model was proved. Influence of air flow rate for the oxidation behavior was thought negligible in the conditions investigated in this study.

Journal Articles

Oxidation behavior of fuel cladding tube in spent fuel pool accident condition

Nemoto, Yoshiyuki; Kaji, Yoshiyuki; Ogawa, Chihiro; Nakashima, Kazuo*; Tojo, Masayuki*

Zairyo To Kankyo, 66(5), p.180 - 187, 2017/05

In spent fuel pool (SFP) under loss-of-cooling or loss-of-coolant severe accident condition, the spent fuels will be exposed to air and heated by their own residual decay heat. Integrity of fuel cladding is crucial for SFP safety therefore study on cladding oxidation in air at high temperature is important. Zircaloy-2 (Zry2) and zircaloy-4 (Zry4) were applied for thermogravimetric analyses (TGA) in different temperatures and different air flow rates in this work. Oxidation rate increased with temperature. In range of air flow rate predicted in spent fuel lack during SFP accident, influence of flow rate was not clearly observed below 950$$^{circ}$$C for Zry2 and below 1050$$^{circ}$$C for Zry4. Over these temperature, oxidation rates appeared obviously higher in higher air flow rate, and this trend became clearer when temperature increased. Oxide layers were carefully examined after the oxidation tests and compared with the mass gain data in TGA to investigate detail of air oxidation process. The results revealed that mass gain data in the pre breakaway transition stage reflects growth of the dense oxide film on specimen surface, and in the post breakaway transition stage, it reflects growth of porous oxide layer beneath the breakaway cracking of the oxide film.

Journal Articles

Study on oxidation behavior of cladding for accident conditions in spent fuel pool

Nemoto, Yoshiyuki; Kaji, Yoshiyuki; Ogawa, Chihiro; Nakashima, Kazuo*; Tojo, Masayuki*; Goto, Daisuke*

Fushoku Boshoku Kyokai Dai-62-Kai Zairyo To Kankyo Toronkai Koenshu (CD-ROM), p.23 - 24, 2015/11

In order to clarify the air oxidation behavior of the cladding at high temperatures for study on improvement of safety for accident conditions in spent fuel pool, the oxidation tests for both small specimens under constant temperature conditions and long specimens under loss of coolant simulated temperature conditions were carried out, and the knowledge for influence of both temperature gradient and preoxide film on oxidation behavior of the cladding were obtained in this study.

Journal Articles

Accident measures of serious accidents

Tamaki, Hitoshi

Tekisuto "Kakunenryo Saikuru" (Internet), 3 Pages, 2014/12

Revised regulatory rule of nuclear facilities in Japan defines "Serious accident", and require accident measures for them to not only power reactors, but also fuel reprocessing and fabrication facilities. This document describes the basis of accident measures for Serious accident at nuclear fuel reprocessing and fabrication facilities, as a part of "Text of Nuclear Fuel Cycle".

JAEA Reports

None

JNC-TN4420 2000-009, 11 Pages, 2000/06

JNC-TN4420-2000-009.pdf:0.84MB

None

Journal Articles

Hot atom chemistry and severe accident of water cooled fission reactor

Saeki, Masakatsu

Handbook of Hot Atom Chemistry, p.637 - 646, 1992/00

no abstracts in English

Oral presentation

Study on improvement of safety for accident conditions in spent fuel pool, 2; Air oxidation behavior of the cladding

Nemoto, Yoshiyuki; Kaji, Yoshiyuki; Nakashima, Kazuo*; Tojo, Masayuki*; Goto, Daisuke*

no journal, , 

For the upgrading of the severe accident code aiming to analyze the coolant loss accident in spent fuel pool (SFP), it is required to model the air oxidation behavior of the cladding at high temperature. Authors proceeded air oxidation tests using small samples and long samples. For the long samples, temperature distribution simulating the SFP accident condition was given. The results were evaluated for the construction and validation of the air oxidation model. The results of the experiments and the outline of the program will be presented as well.

Oral presentation

Peer review on the safety requirements of the prototype fast breeder reactor "Monju", 3; Summary of international review

Tobita, Yoshiharu

no journal, , 

An advisory panel on Monju safety requirements issued a report on the safety requirements for the Prototype Fast Breeder Reactor "Monju" in the last July. The issued report was reviewed both by domestic and international experts on FBR safety. The result of international review is reported in this presentation.

Oral presentation

Peer review on the safety requirements for the prototype fast breeder reactor "Monju", 1; Overview of safety requirement and domestic/international review

Nakai, Ryodai

no journal, , 

An advisory panel on Monju safety requirements issued a report on the safety requirements for the Prototype Fast Breeder Reactor "Monju" in the last July. The issued report was reviewed both by domestic and international experts on FBR safety. The paper presents the outline of the report and its domestic and international review.

Oral presentation

Research program of thermal hydraulic behavior in containment vessel

Shibamoto, Yasuteru; Abe, Satoshi; Ishigaki, Masahiro; Yonomoto, Taisuke

no journal, , 

no abstracts in English

Oral presentation

Study on improvement of safety for accident conditions in spent fuel pool, 4; Loss of coolant accident analysis by MAAP code

Nishimura, Satoshi*; Satake, Masaaki*; Soga, Shota*; Nishi, Yoshihisa*; Kaji, Yoshiyuki; Nemoto, Yoshiyuki

no journal, , 

We conducted the transient analysis for the phenomenon of loss of coolant in Spent Fuel Pool by Severe Accident code MAAP version 5.03 and evaluated quantitatively the influence of initial water level and decay heat on failure time and hydrogen generation of fuel cladding.

Oral presentation

Study on improvement of safety for accident conditions in spent fuel pool, 5; Loss of coolant accident analysis by SAMPSON code

Morita, Yoshihiro*; Suzuki, Hiroaki*; Naito, Masanori*; Kaji, Yoshiyuki; Nemoto, Yoshiyuki

no journal, , 

We conducted the preliminary analysis for the phenomenon of loss of coolant in Spent Fuel Pool by MAAP code and reported the analytical results for temperature and relocation behavior of spent fuel channels.

Oral presentation

First experiments using the CIGMA facility on LWR containment thermal hydraulics

Shibamoto, Yasuteru; Abe, Satoshi; Ishigaki, Masahiro; Yonomoto, Taisuke

no journal, , 

no abstracts in English

Oral presentation

Oral presentation

Oral presentation

Study on In-Vessel Retention (IVR) of unprotected accident for fast reactor, 4; Assessment of transition phase in ULOF

Tobita, Yoshiharu; Suzuki, Toru; Tagami, Hirotaka

no journal, , 

The event progression in the transition phase of ULOF (Unprotected Loss of Flow), which is the representative event in ATWS (Anticipated Transient without Scram) of fast breeding reactor. The existing experimental knowledges on the important phenomena, which dominates the event progression, were adopted in the nominal case. The reactivity lowered with accordance to the fuel discharge through control rod guide tube and the event terminated without prompt criticality. If the uncertainty was considered in the analysis, the reactivity slightly exceeded the prompt criticality, but no mechanical energy was produced.

32 (Records 1-20 displayed on this page)