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Journal Articles

Study of recent sodium pool fire model improvements for MELCOR code

Aoyagi, Mitsuhiro; Louie, D. L. Y.*; Uchibori, Akihiro; Takata, Takashi; Luxat, D.*

Proceedings of 28th International Conference on Nuclear Engineering; Nuclear Energy the Future Zero Carbon Power (ICONE 28) (Internet), 10 Pages, 2021/08

Journal Articles

Study of sodium pool fire model improvement in MELCOR for SFR

Louie, D. L. Y.*; Aoyagi, Mitsuhiro

Transactions of the American Nuclear Society, 124(1), p.824 - 827, 2021/06

The Sodium Chemistry (NAC) package in MELCOR has been developed to enhance application to sodium cooled fast reactors. Based on the recommendations in the previous study through the benchmark analyses of the F7-1 pool fire experiment, this study aims to improve the MELCOR models capturing the oxide layer effect, sodium pool spreading and pool-pan heat transfer, respectively. Each of these models enable a better characterization of the all the processes of relevance to sodium pool fires as observed during the F7-1 test. The MELCOR sodium pool fire enhancement has demonstrated the importance of the improved models.

Journal Articles

Sodium fire collaborative study progress; CNWG fiscal year 2020

Louie, D. L. Y.*; Aoyagi, Mitsuhiro

SAND2021-0136 (Internet), 53 Pages, 2021/01

This report discusses the progress on the collaboration between Sandia National Laboratories (SNL) and Japan Atomic Energy Agency (JAEA) on the sodium fire research in fiscal year 2020. First, the current sodium pool fire model in MELCOR is discussed. The associated sodium fire input requirements are also presented. These input requirements are flexible enough to permit further model development via control functions to enhance the current model without modifying the source code. The theoretical pool fire model improvement developed at SNL is discussed. A control function model has been developed from this improvement. Then, the validation study of the sodium pool fire model in MELCOR is described. To validate this pool fire model with the enhancement, a JAEA F7-1 sodium pool fire experiment is used. The results of the calculation are discussed as well as suggestions for further model improvement. Finally, recommendations are made for new MELCOR simulations for next fiscal year, 2021.

Journal Articles

Sodium fire analysis using a sodium chemistry package in MELCOR

Aoyagi, Mitsuhiro; Uchibori, Akihiro; Takata, Takashi; Louie, D. L. Y.*; Clark, A. J.*

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 6 Pages, 2020/08

The Sodium Chemistry (NAC) package in MELCOR has been developed to enhance application to sodium cooled fast reactors. The models in the NAC package have been assessed through benchmark analyses of the F7-1 pool fire experiment. This study assesses the capability of the pool fire model in MELCOR and provides recommendations for future model improvements. The MELCOR analysis yields lower values than the experimental data in pool combustion rate and pool, catch pan, and gas temperature during early time. The current heat transfer model for the catch pan is the primary cause of the difference. After sodium discharge stopping, the pool combustion rate and temperature become higher than experimental data. This is caused by absence of a model for pool fire suppression due to the oxide layer buildup on the pool surface. Based on these results, recommendations for future works are needed, such as heat transfer modification for the catch pan and consideration of the effects of the oxide layer.

Journal Articles

Numerical validation of AQUA-SF in SNL T3 sodium spray fire experiment

Sonehara, Masateru; Aoyagi, Mitsuhiro; Uchibori, Akihiro; Takata, Takashi; Ohshima, Hiroyuki; Clark, A. J.*; Louie, D. L. Y.*

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 4 Pages, 2020/08

In order to investigate the multi-dimensional effects of sodium combustion, a benchmark analysis of the SNL Surtsey spray combustion experiment (SNL T3 experiments) using AQUA-SF and SPHINCS is conducted in JAEA. As a best estimate analysis, the spray burning duration is adjusted in the computation in order to take into account the temporary suppression of the spray combustion observed in the experiment. Furthermore, droplet size of SPHINCS and AQUA-SF are optimized to represent the T3 experimental results. The best estimate of AQUA-SF results in the droplet diameter of 2.5 mm, which agrees quite well with the spatial temperature measurements, and the sodium droplet diameter measurement with a high speed camera.

Journal Articles

Sodium fire collaborative study progress; CNWG fiscal year 2019

Louie, D. L. Y.*; Uchibori, Akihiro

SAND2019-15043 (Internet), 35 Pages, 2019/12

This report describes the progress on the sodium fire research in fiscal year 2019 in the Civil Nuclear Energy Research and Development Working Group (CNWG). In this study, the validation study of the sodium pool fire model incorporated into the MELCOR code, which was originally developed for accident analysis in light water reactors, was carried out through the numerical analysis on the sodium pool fire experiment named F7-1. In this preliminary analysis, pool and atmosphere temperature went up to the same level with the measured results, while the unnatural behavior appeared in the latter half of the analysis. Based on this result, recommendations for improvement were made for a new analysis in next fiscal year, 2020.

Oral presentation

Development of the sodium fire module in integrated severe accident analysis code, SPECTRA; Code-to-code comparison with the MELCOR code through the benchmark analysis of the F7-1 pool fire test

Aoyagi, Mitsuhiro; Uchibori, Akihiro; Takata, Takashi; Louie, D. L. Y.*

no journal, , 

The SPECTRA code has been developed as an integrated simulation system for severe accident evaluation in a sodium cooled fast reactor. In this study, the sodium pool fire model of SPECTRA is accessed through the benchmark analysis of the F7-1 pool fire experiment. As well as the comparison with the experimental data, the SPECTRA result is also compared to the results of the MELCOR and SPHINCS codes. All the SPECTRA results well agree with the results of SPHINCS from which the pool fire model of SPECTRA is adapted. The comparisons with MELCOR and experiment show also reasonable agreements in the essential pool fire behavior. The principal difference is the combustion rare after sodium supply stopping especially in the comparison with the experiment. This affects smaller temperature decreasing of the pool, catch-pan, and gas in SPECTRA. Such differences should be investigated more in the future works.

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