Effects of nozzle orifice shape on jet breakup and splashing during liquid jet impact onto a horizontal plate

Sun, G.*; Zhan, Y.*; 大川 富雄*; 青柳 光裕; 内堀 昭寛; 岡野 靖

Experimental Thermal and Fluid Science, 151, p.111095_1 - 111095_15, 2024/02

https://doi.org/10.1016/j.expthermflusci.2023.111095

Experiments were carried out on the liquid jet ejected from oval nozzles to investigate the effects of nozzle orifice shape on jet behavior. At low and high liquid flow rates, the liquid jet behaved similarly to the circular jet in our previous studies; the jet breakup lengths and the size of the droplets formed after the jet breakup were expressed by similar dimensionless correlations as those for the circular jet. At the intermediate liquid flow rate, a bamboo leaf-like structure formed on the liquid jet dominated the jet breakup. The jet breakup lengths were therefore correlated using a theory for the surface tension-induced shape oscillation of elliptical fluid. These correlations enabled to estimate the liquid jet state at any distance from the nozzle. It was also confirmed that if the state of the liquid jet at the impact point is known, the splash rate and the size of the splashed droplets can be predicted satisfactorily using the available correlations based on the experimental data for the circular jet.

Numerical simulation technologies for safety evaluation in plant lifecycle optimization method, ARKADIA for advanced reactors

内堀 昭寛; 堂田 哲広; 青柳 光裕; 曽根原 正晃; 曽我部 丞司; 岡野 靖; 高田 孝*; 田中 正暁; 江沼 康弘; 若井 隆純; et al.

Nuclear Engineering and Design, 413, p.112492_1 - 112492_10, 2023/11

https://doi.org/10.1016/j.nucengdes.2023.112492

ナトリウム冷却高速炉に代表される革新炉に対し、安全性評価やそれに基づく設計最適化を自動で行うARKADIAを開発している。通常運転もしくは設計基準事象の範囲で設計最適化を行うARKADIA-Designについては、核特性-熱流動-炉心変形のマルチレベル連成解析手法等を中心技術として開発し、その基本的機能を確認した。シビアアクシデントまで含む範囲で安全性評価を行うARKADIA-Safetyの基盤技術として、炉内/炉外事象一貫解析手法の整備を進め、仮想的なシビアアクシデント事象を解析することで基本的機能を確認した。また、炉外事象に対する解析モデルの高度化、設計最適解の探索工程を合理化するAI技術の開発に着手した。

Experimental study on the breakup of liquid jet discharged from a nozzle with sudden contraction

Sun, G.*; 大川 富雄*; 青柳 光裕; 内堀 昭寛; 岡野 靖

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 8 Pages, 2023/05

ナトリウム冷却高速炉における冷却材漏えい時には、漏えいした液体ナトリウムの液跳ねが、ナトリウムの燃焼へ影響する。これまでの研究では、円形の破損孔を想定した実験を行い、液跳ね前の噴流の状態が液跳ね挙動へ影響することが分かっている。本研究では実機を模擬した急拡大ノズルを用いた実験を行い、噴流の状態を可視化した。可視化実験の結果、ジェット流速が一定以上の場合には、ジェットが安定状態に至るまではジェット崩壊が促進された。またジェットが不安定状態に遷移すると、流速を大幅に低下させない限り安定状態には戻らない結果であった。安定状態に遷移した後のジェット流は、同流量の不安定状態のものと比べて長い分裂長さであった。

Sodium fire collaborative study progress; CNWG fiscal year 2022

Louie, D. L. Y.*; 青柳 光裕

SAND2022-14235 (Internet), 29 Pages, 2022/10

https://doi.org/10.2172/1892376

本報告書は、米国サンディア国立研究所と原子力機構のナトリウム燃焼分野に係る2022年共同研究成果の報告書である。MELCORコードに導入されているナトリウムプール燃焼モデルと関連する解析の入力項目、プール燃焼モデルの改良についての説明が述べられている。改良モデルを含むプール燃焼モデルを評価するために、JAEAにより過去に実施されたF7-1およびF7-2ナトリウムプール燃焼実験に対してベンチマーク解析を実施し、解析結果の考察とともに更なるモデル改良の検討を行った。最後に、これまでの成果を踏まえた2023年度のMELCOR解析の方向性が述べられている。

Validation study of sodium pool fire modeling efforts in MELCOR and SPHINCS codes

Louie, D. L. Y.*; 青柳 光裕; 内堀 昭寛; 高田 孝; Luxat, D. L.*

Proceedings of Technical Meeting on State-of-the-art Thermal Hydraulics of Fast Reactors (Internet), 6 Pages, 2022/09

The paper describes progress of an international collaborative research in the area of SFR sodium fire modeling between the United States and Japan under the framework of the Civil Nuclear Energy Research and Development Working Group (CNWG). In this collaboration between Sandia National Laboratories (SNL) and Japan Atomic Energy Agency (JAEA), the validation basis for and modeling capabilities of sodium spray and pool fires in MELCOR of SNL and SPHINCS of JAEA are being enhanced. This study documents MELCOR and SPHINCS sodium pool fire model validation exercises against the JAEA's sodium pool fire experiments, F7-1 and F7-2. The proposed enhancement of the sodium pool fire models in MELCOR through addition of thermal hydraulic and sodium spreading models that enable a better representation of experimental results is also described.

水蒸気改質処理試験装置における主反応器耐火材の補修効果確認試験

木島 惇; 小山 勇人; 大和田 光宏; 萩原 正義; 青柳 義孝

JAEA-Technology 2022-012, 14 Pages, 2022/07

JAEA-Technology-2022-012.pdf:1.51MB

過去の技術開発過程において発生した大量の難処理性有機廃液の処理については、処理設備の腐食やフィルタの閉塞を引き起こす等の理由により焼却処理が適さないことから、それら廃液の処理技術として、平成17年度から水蒸気改質処理法とその処理装置の開発を実施している。処理装置の重要な構成要素である主反応器は内部が非常に高温となるため、主反応器外筒の内面に耐火材が施されているが、令和2年にこの耐火材の内表面全域に経年劣化によるひび割れや表層剥離を確認したため、令和3年度に主反応器全体を更新した。一方、この主反応器内面表層のひび割れや表層剥離について補修が可能であれば、今後主反応器全体を更新する必要は無くなると共に、これまで使用していた主反応器も廃棄することなく、補修を行った後、予備品として再使用できる。そこで、主反応器を更新する前に、劣化した耐火材表面を2種類の補修材候補を用いて補修し、実際の有機系廃棄物を模擬した試料の燃焼試験を実施し、それぞれの補修材の有効性を評価した。模擬燃焼試験後において、補修材候補のうち1種について剥落や剥離及びひび割れがなかったこと、補修材が脆化することなく、耐火材と強固に密着していたこと、補修箇所の主反応器外筒の表面温度が設計温度上限を超過しなかったことから、補修材を用いた主反応器の補修は十分可能であると結論付けた。

MELCOR validation study on sodium pool fire model with comparison to SPHINCS

Louie, D. L. Y.*; 青柳 光裕

Proceedings of International Topical Meetings on Advances in Thermal Hydraulics (ATH 2022) (Internet), p.316 - 329, 2022/06

This paper describes progress of an international collaborative research in SFR sodium fire modeling between the United States and Japan under the framework of the Civil Nuclear Energy Research and Development Working Group (CNWG). In this collaboration between Sandia National Laboratories (SNL) and Japan Atomic Energy Agency (JAEA), the validation basis for and modeling capabilities of sodium pool fires in MELCOR of SNL and SPHINCS of JAEA are being assessed. Additional model improvements for the sodium pool fire in MELCOR are discussed. The MELCOR results for the sodium pool fire model enhancement in MELCOR agreed well with the JAEA's F7 pool fire experiments and compared closely with SPHINCS.

Development of the sodium pool and floor concrete module for the integrated SFR safety analysis code, SPECTRA

青柳 光裕; 内堀 昭寛; 高田 孝

Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 13 Pages, 2022/03

The SPECTRA code has been developed as an integrated safety analysis tool for sodium-cooled fast reactors (SFRs). In this study, the capability of SPECTRA is enhanced by establishing a sodium pool and floor concrete module commonly used in individual physical modules. This paper describes the framework of modelling for the mass and heat transfer in the sodium pool and the floor concrete. Considering concrete ablation due to sodium and debris, bottom of the sodium pool changes during event progression. This change in material composition in certain position is modeled by volume and mass fraction of each component. A simple convection model for the pool is implemented to ensure the conservation of heat and mass. This model is tested through the verification analysis in comparison with the existing model. As the result, it is confirmed the behavior of pool spreading and concrete ablation can be simulated by this module correctly.

Droplet generation during spray impact onto a downward-facing solid surface

Zhan, Y.*; Sun, G.*; 大川 富雄*; 青柳 光裕; 高田 孝

Experimental Thermal and Fluid Science, 126, p.110402_1 - 110402_8, 2021/08

https://doi.org/10.1016/j.expthermflusci.2021.110402

Experiments were conducted to explore the droplet generation process when an ascending liquid spray impacts on a downward-facing solid surface. The droplets generated in the present experiments were classified into the two types: one is the splashing droplets generated by the impacts of droplets in spray and the other is the falling droplets produced from a liquid film formed on the solid surface. The falling droplets were further classified to the first falling droplets and the satellite droplets. It was found that the ratio of the splashing droplets increases with an increase in the impact Weber number. The size of the splashing droplets was in the same order with the impacting droplets in spray. On the other hand, the size of the falling droplets was inversely proportional to their order. Using the experimental data, dimensionless correlations were developed for the rates and sizes of the splashing and falling droplets.

Numerical modeling of radiation heat transfer from combusting droplets for a sodium fire analysis

青柳 光裕; 高田 孝; 宇埜 正美*

Nuclear Engineering and Design, 380, p.111258_1 - 111258_11, 2021/08

https://doi.org/10.1016/j.nucengdes.2021.111258

This study aims to model radiation heat transfer from combusting droplets numerically. In the modeling, radiation energy transport on the combusting area around a sodium droplet is formulated considering emission, absorption and scattering as interaction with surrounding gas radiation. Radiation energy from the combusting droplets is added to the source term of the radiation transport equation in the 6-flux gas radiation model for the multi-dimensional sodium fire analysis code AQUA-SF. Direct radiation heat transfer from combusting droplets can be simulated by this improved model. The improved model is tested through the verification analyses of single droplet combustion and the benchmark analysis on the upward sodium spray combustion experiment. The results of the test analyses show increase in heat transfer to the walls due to the droplet radiation. As the result, the sodium fire analysis becomes more reasonably by the improved model.