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論文

Experimental study on debris bed characteristics for the sedimentation behavior of solid particles used as simulant debris

Shamsuzzaman, M.*; 堀江 達郎*; 浮池 亮太*; 神山 基紀*; 森岡 徹*; 松元 達也*; 守田 幸路*; 田上 浩孝; 鈴木 徹*; 飛田 吉春

Annals of Nuclear Energy, 111, p.474 - 486, 2018/01

 被引用回数:2 パーセンタイル:16.17(Nuclear Science & Technology)

Particle bed characteristics are experimentally investigated for the sedimentation and subsequent bed formation of solid particles, related to the coolability aspects in core-disruptive accidents. Presently a series of experiments with gravity driven discharge of solid particles into a quiescent water pool was performed to evaluate bed formation characteristic in the course of particle sedimentation. We evaluated the effects of the crucial factors: nozzle diameter, particle density, particle diameter and nozzle height on four key quantitative parameters of bed shape: mound dimple area, mound dimple volume, repose angle and mound height to illustrate the role of the crucial factors on forming the particle bed shape. The investigated crucial factors exhibit a significant role that diversifies the particle bed formation process. Based on the data obtained in the experimental observations, we developed an empirical correlation to compare the predicted results with the experimental bed heights. The proposed empirical correlation can reasonably demonstrate the general trend of the experimental bed height. This correlation could be useful to assess the particle bed elevation, and to identify the governing parameters.

論文

Sedimentation behavior of mixed solid particles

Sheikh, Md. A. R.*; Son, E.*; 神山 基紀*; 森岡 徹*; 松元 達也*; 守田 幸路*; 松場 賢一; 神山 健司; 鈴木 徹*

Journal of Nuclear Science and Technology, 55(6), p.623 - 633, 2018/01

 パーセンタイル:100(Nuclear Science & Technology)

高速炉の炉心損傷事故時に形成される燃料デブリの堆積高さは、燃料デブリの冷却性及び臨界特性に影響する重要な要因の一つである。本研究では、燃料デブリの堆積挙動に関する実験データベースを構築するため、燃料デブリを模擬した特性(粒子径,密度,球形度等)の異なる固体粒子(アルミナ,スティール)の混合粒子を水プール中へ落下・堆積させる実験を行い、粒子ベッドの堆積高さを測定するとともに、均質粒子及び混合粒子から成るデブリベッドの堆積高さを予測する実験相関式を構築した。構築した実験相関式は粒子ベッドの堆積高さの測定結果と良く一致することを確認した。

論文

Numerical simulation of solid-particle sedimentation behavior using a multi-fluid model coupled with DEM

河田 凌*; 大原 陽平*; Sheikh, Md. A. R.*; Liu, X.*; 松元 達也*; 守田 幸路*; Guo, L.*; 神山 健司; 鈴木 徹

Proceedings of 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) (USB Flash Drive), 14 Pages, 2017/09

Numerical simulations of various thermal-hydraulic phenomena with multiphase and multicomponent flows in postulated core disruptive accidents (CDAs) are regarded as particular difficulties in the safety analysis of liquid-metal cooled reactors. In a material relocation phase of CDAs, core debris may settle on the core-support structure and/or in the lower inlet plenum of the reactor vessel and then form the debris bed. In particular, the shape of debris bed is crucial for the relocation of molten core and heat-removal capability of the debris bed as well as re-criticality. In the present study, a hybrid numerical simulation method, which couples the multi-fluid model of the 3D fast reactor safety analysis code SIMMER-IV with the discrete element method (DEM), was applied to analyze sedimentation and bed formation behaviors of core debris. In the present study, 3D simulations were performed for a series of particle sedimentation experiments with gravity driven discharge of solid particles into a quiescent cylindrical water pool. The present simulation predicts the sedimentation behavior of mixed particles with different density or particle size as well as homogeneous particles. The simulation results on bed shapes and particle distribution in the bed agree well with the experimental ones. They demonstrate the fundamental applicability of the present hybrid method to solid-particle sedimentation and bed formation simulations.

論文

Experimental database for bed formation behaviors of solid particles

Sheikh, M. A. R.*; Son, E.*; 神山 基紀*; 森岡 徹*; 松元 達也*; 守田 幸路*; 松場 賢一; 神山 健司; 鈴木 徹

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 10 Pages, 2016/11

ナトリウム冷却高速炉の炉心損傷事故における再配置過程では、微粒化デブリによる堆積ベッド形成挙動がデブリベッド冷却による炉容器内事故終息の観点で重要である。本研究では、粒子堆積ベッド形成挙動に関する実験データベースを構築するため、微粒化デブリを模擬した固体粒子を円筒型の水プール中へ重力落下によって放出させ、粒子堆積ベッドの形状及び高さを測定する実験を行った。本実験では、材質及びサイズの異なる3種類(アルミナ,ジルコニア,スティール)の球形・非球形粒子を用い、これらのパラメータが粒子ベッドの堆積形状に及ぼす影響を調べるとともに、その結果に基づき粒子ベッドの堆積高さを予測する整理式を実験データベースとして開発した。開発した整理式は、本実験で把握された重要パラメータに対する堆積ベッド高さの変化傾向をよく再現しており、広範な適用性を有していることが示された。

論文

Experimental investigation on characteristics of mixed particle debris in sedimentation and bed formation behavior

Sheikh, M. A. R.*; Son, E.*; 神山 基紀*; 森岡 徹*; 松元 達也*; 守田 幸路*; 松場 賢一; 神山 健司; 鈴木 徹

Proceedings of 11th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, Operation and Safety (NUTHOS-11) (USB Flash Drive), 12 Pages, 2016/10

高速炉の炉心損傷事故時に形成される燃料デブリの落下・堆積挙動を明らかにするため、燃料デブリを模擬した特性の異なる固体粒子(アルミナ、スティール)の混合粒子を水プール中へ落下・堆積させる粒子ベッド形成実験を行い、堆積デブリベッドの形状に対する主要パラメータの影響を検討した。本研究により、燃料デブリの落下・堆積に関する数値モデル及びシミュレーションコードの検証に有効な実験データ及び知見が得られた。

論文

Development of the evaluation methodology for the material relocation behavior in the core disruptive accident of sodium-cooled fast reactors

飛田 吉春; 神山 健司; 田上 浩孝; 松場 賢一; 鈴木 徹; 磯崎 三喜男; 山野 秀将; 守田 幸路*; Guo, L.*; Zhang, B.*

Journal of Nuclear Science and Technology, 53(5), p.698 - 706, 2016/05

AA2015-0794.pdf:2.46MB

 被引用回数:3 パーセンタイル:42.29(Nuclear Science & Technology)

炉心損傷事故(CDA)の炉内格納(IVR)はナトリウム冷却高速炉(SFR)の安全特性向上において極めて重要である。SFRのCDAにおいては、溶融炉心物質が炉容器の下部プレナムへ再配置し、構造物へ重大な熱的影響を及ぼし、炉容器の溶融貫通に至る可能性がある。この再配置過程の評価を可能とし、SFRのCDAではIVRで終息することが最も確からしいことを示すため、SFRのCDAにおける物質再配置挙動の評価手法を開発する研究計画が実施された。この計画では、炉心領域からの溶融物質流出挙動の解析手法、溶融炉心物質のナトリウムプール中への侵入挙動、デブリベッド挙動のシミュレーション手法を開発した。

報告書

概要調査段階における設計・性能評価手法の高度化,3; NUMO-JAEA共同研究報告書(2013年度)(共同研究)

柴田 雅博; 澤田 淳; 舘 幸男; 牧野 仁史; 若杉 圭一郎; 三ツ井 誠一郎; 北村 暁; 吉川 英樹; 小田 治恵; 石寺 孝充; et al.

JAEA-Research 2014-030, 457 Pages, 2015/03

JAEA-Research-2014-030.pdf:199.23MB

原子力機構(JAEA)がこれまで蓄積してきた技術やノウハウを、原子力発電環境整備機構(NUMO)が今後行う精密調査地区の選定等の処分事業に適用できるよう、実施主体の視点に沿って実用化を図っていくための具体的な考え方と進め方を策定すること等を目的として、2011年度よりJAEAとNUMOは以下の3つのテーマについて共同研究を進めている。(1)水理の観点からみた母岩の適性を評価する方法に関する検討: 水理地質構造モデル構築手法の事例調査に基づいて、得られた知見を評価ツリーとして整理し、モデルの不確実性やそれらの評価項目への影響等についての検討を行った。(2)シナリオの構築方法に関する検討: 状態設定手順を実務的な観点から、さらに見直すとともに、セメント影響とガラス溶解挙動について、知見の体系的な整理と不確実性の影響について解析的検討を行った。(3)核種移行パラメータの設定方法に関する検討: 母岩の分配係数を対象に、国内外の事例調査をもとに複数の設定手法を整理し、堆積岩及び花崗岩への適用を通じ妥当性や課題を確認した。溶解度について、溶解度制限固相の決定を含む設定手法を検討し、主要核種への適用を通じ妥当性や課題を確認した。

論文

An Investigation on debris bed self-leveling behavior with non-spherical particles

Cheng, S.; 田上 浩孝; 山野 秀将; 鈴木 徹; 飛田 吉春; 竹田 祥平*; 西 津平*; 錦戸 達也*; Zhang, B.*; 松元 達也*; et al.

Journal of Nuclear Science and Technology, 51(9), p.1096 - 1106, 2014/09

AA2013-0303.pdf:1.68MB

 被引用回数:13 パーセンタイル:12.31(Nuclear Science & Technology)

Studies on debris bed self-leveling behavior with non-spherical particles are crucial in the assessment of actual leveling behavior that could occur in core disruptive accident of sodium-cooled fast reactors. Although in our previous publications, a simple empirical model (based model), with its wide applicability confirmed over various experimental conditions, has been successfully advanced to predict the transient leveling behavior, up until now this model is restricted to calculations of debris bed of spherical particles. Focusing on this aspect, in this study a series of experiments using non-spherical particles was performed within a recently-developed comparatively larger-scale experimental facility. Based on the knowledge and data obtained, an extension scheme is suggested with the intention to extend the base model to cover the particle-shape influence. Through detailed analyses, it is found that by coupling this scheme, good agreement between experimental and predicted results can be achieved for both spherical and non-spherical particles given current range of experimental conditions.

論文

Experimental study and empirical model development for self-leveling behavior of debris bed using gas-injection

Cheng, S.; 田上 浩孝; 山野 秀将; 鈴木 徹; 飛田 吉春; 中村 裕也*; 竹田 祥平*; 西 津平*; Zhang, B.*; 松元 達也*; et al.

Mechanical Engineering Journal (Internet), 1(4), p.TEP0022_1 - TEP0022_16, 2014/08

To clarify the mechanisms underlying the debris-bed self-leveling behavior, several series of experiments were elaborately designed and conducted within a variety of conditions in recent years, under the collaboration between Japan Atomic Energy Agency (JAEA) and Kyushu University. The current contribution, including knowledge from both experimental analyses and empirical model development, is focused on a recently developed comparatively larger-scale experimental facility using gas-injection to simulate the coolant boiling. Based on the experimental observation and quantitative data obtained, influence of various experimental parameters, including gas flow rate ($$sim$$ 300 L/min), water depth (180 mm and 400 mm), bed volume (3 $$sim$$ 7 L), particle size (1 $$sim$$ 6 mm), particle density (beads of alumina, zirconia and stainless steel) along with particle shape (spherical and irregularly-shaped) on the leveling is checked and compared. As for the empirical model development, aside from a base model which is restricted to calculations of spherical particles, the status of potential considerations on how to cover more realistic conditions (esp. debris beds formed with non-spherical particles), is also presented and discussed.

論文

Neutron-sensitive ZnS/$$^{10}$$B$$_{2}$$O$$_{3}$$ ceramic scintillator detector as an alternative to a $$^{3}$$He-gas-based detector for a plutonium canister assay system

中村 龍也; 大図 章; 藤 健太郎; 坂佐井 馨; 鈴木 浩幸; 本田 克徳; 美留町 厚; 海老根 守澄; 山岸 秀志*; 高瀬 操; et al.

Nuclear Instruments and Methods in Physics Research A, 763, p.340 - 346, 2014/05

 被引用回数:2 パーセンタイル:72.96(Instruments & Instrumentation)

ヘリウム3ガス検出器の代替としてプルトニウム検認装置用に使用できるZnS/$$^{10}$$B$$_{2}$$O$$_{3}$$セラミックシンチレータ検出器を開発した。当該検出器はZnS/$$^{10}$$B$$_{2}$$O$$_{3}$$セラミックシンチレータを矩形状の光伝搬筐体内に対角配置しその両端に設置した光電子増倍管により中性子誘起の発光を収集するものでモジュラー構造を有する。有感面積30mm$$times$$250mmをもつプロトタイプ検出器を試作し、中性子感度21.7-23.4$$pm$$0.1cps$$/$$nv(熱中性子)、$$gamma$$線感度1.1-1.9$$pm$$0.2$$times$$10$$^{-7}$$($$^{137}$$Cs)、計数均一性$$<$$6%、温度計数-0.24$$pm$$0.05%/$$^{circ}$$C(20-50$$^{circ}$$C)の性能を確認した。

論文

A Position-sensitive tubular scintillator-based detector as an alternative to a $$^{3}$$He-gas-based detector for neutron-scattering instruments

中村 龍也; 片桐 政樹*; 藤 健太郎; 本田 克徳; 鈴木 浩幸; 海老根 守澄; 美留町 厚; 坂佐井 馨; 曽山 和彦

Nuclear Instruments and Methods in Physics Research A, 741, p.42 - 46, 2014/03

 被引用回数:5 パーセンタイル:43.1(Instruments & Instrumentation)

ヘリウム3ガス検出器の代替として管形状を有する位置敏感型のシンチレータ中性子検出器を提案する。当該検出器の一要素はロールされたZnS/$$^{6}$$LiFによりコイル状の波長シフトファイバを挟み込んだ構造(SFCエレメント)を持ち、これを同一軸上に多数配置しアルミ管内に設置して1次元検出器が構成される。64エレメント、ピクセルサイズ22$$times$$20mmであるプロトタイプ機を製作し中性子検出原理、位置敏感性を実証することに成功した。

論文

A Scintillator-based detector with sub-100-$$mu$$m spatial resolution comprising a fibre-optic taper with wavelength-shifting fibre readout for time-of-flight neutron imaging

中村 龍也; 藤 健太郎; 川崎 卓郎; 本田 克徳; 鈴木 浩幸; 海老根 守澄; 美留町 厚; 坂佐井 馨; 曽山 和彦; 片桐 政樹*

Nuclear Instruments and Methods in Physics Research A, 737, p.176 - 183, 2014/02

 被引用回数:7 パーセンタイル:30.82(Instruments & Instrumentation)

A scintillator-based neutron-counting imaging detector with a sub-100-$$mu$$m spatial resolution was developed for energy-selective neutron imaging. The detector head of the detector comprised a thin ZnS/$$^{6}$$LiF scintillator screen, a fibre-optic taper and crossed wavelength-shifting (WLS) fibre arrays. The developed detector had a pixel size of 34 $$mu$$m $$times$$ 34 $$mu$$m, and exhibited spatial FWHM resolutions of 80 $$mu$$m and 61 $$mu$$m in the x and y directions, respectively. A small prototype detector demonstrated the capability of neutron imaging using Bragg edges of a Cu/Fe sample when using the pulsed-neutron source in the Materials and Life Science Experimental Facility at the Japan Proton Accelerator Research Complex.

論文

Evaluation of debris bed self-leveling behavior; A Simple empirical approach and its validations

Cheng, S.; 田上 浩孝; 山野 秀将; 鈴木 徹; 飛田 吉春; Zhang, B.*; 松元 達也*; 守田 幸路*

Annals of Nuclear Energy, 63, p.188 - 198, 2014/01

 被引用回数:21 パーセンタイル:4.37(Nuclear Science & Technology)

To clarify the mechanisms underlying the debris bed self-leveling behavior, several series of experiments were elaborately designed and conducted in recent years under the constructive collaboration between Japan Atomic Energy Agency (JAEA) and Kyushu University (Japan). Based on the experimental observations and quantitative data obtained from various conditions, a simple empirical approach to predict the self-leveling development depending on particle size, particle density and gas velocity was proposed. To confirm the rationality and wide applicability of this approach, over the past few years extensive efforts have been made by performing modeling investigations against a large number of experimental data covering various conditions (including difference in bubbling mode, bed geometry and range of experimental parameters). The present contribution synthesizes these efforts and gives detailed comparative analyses of the performed validations, thus, providing some insight for a better understanding of CDAs and improved verifications of computer models developed in advanced fast reactor safety analysis codes.

報告書

概要調査段階における設計・性能評価手法の高度化,2; NUMO-JAEA共同研究報告書(2012年度)(共同研究)

柴田 雅博; 澤田 淳; 舘 幸男; 早野 明; 牧野 仁史; 若杉 圭一郎; 三ツ井 誠一郎; 小田 治恵; 北村 暁; 大澤 英昭; et al.

JAEA-Research 2013-037, 455 Pages, 2013/12

JAEA-Research-2013-037.pdf:42.0MB

原子力機構(JAEA)及び原子力発電環境整備機構(NUMO)は、平成24年度に引き続き、JAEAがこれまで蓄積してきた技術やノウハウを、NUMOが今後行う精密調査地区の選定等の処分事業に直接適用できるよう、実施主体の視点に沿って実用化を図っていくことを目的として、概要調査段階における処分場の設計・性能評価に関連する主要な技術テーマについて検討した。(1)水理の観点からみた母岩の適性を評価する方法に関する検討については、平成24年度に引き続き、結晶質岩を対象とした地下水移行時間の評価ツリーを拡充するとともに、新たに堆積岩を対象とした評価ツリーを作成した。(2)シナリオの構築に関する検討については、平成24年度の状態設定手順を実務的な観点から見直し、緩衝材を対象として試行した。また、安全機能への不確実性の影響について解析的検討を行った。(3)核種移行パラメータの設定に関する検討については、母岩の分配係数を対象に、国内外の事例調査をもとに複数の条件変換手法を含む設定手法を整理し、堆積岩及び花崗岩への適用を通じ妥当性や課題を確認した。さらに、溶解度について、溶解度制限固相の決定を含む設定手法を検討し、主要核種への適用を通じ妥当性や課題を確認した。

論文

High-resolution crystal structure of copper amine oxidase from ${it Arthrobacter globiformis}$; Assignment of bound diatomic molecules as O$$_{2}$$

村川 武志*; 林 秀行*; 角南 智子; 栗原 和男; 玉田 太郎; 黒木 良太; 鈴木 守*; 谷澤 克行*; 岡島 俊英*

Acta Crystallographica Section D, 69(12), p.2483 - 2494, 2013/12

 被引用回数:8 パーセンタイル:35.2(Biochemical Research Methods)

アルスロバクター-グロビフォルミス由来銅アミン酸化酵素の結晶構造を抗凍結剤として低分子ポリエチレングリコール(LMW PEG; 平均分子量$$sim$$200)を用いて1.08${AA}$分解能で決定した。最終的な結晶構造学的$$R$$因子と$$R$$$$_{rm free}$$値は、それぞれ13.0%と15.0$$%$$であった。LMW PEGの幾つかの分子は、活性部位を含むタンパク質内部の空洞を占めており、それが分子全体の温度因子の著しい低下をもたらし、結果として、単量体分子量が約70,000と比較的大きなタンパク質にも拘わらず原子分解能の構造に至ったことがわかった。推定される全水素原子の約40%は、$$F$$$$_{rm o}$$-$$F$$$$_{rm c}$$差図中に明確な電子密度を持って観察され、複数のマイナーな配座異性体も多くの残基に対して同定された。また、翻訳後に誘導されたキノン補因子と銅原子を含む活性部位における異方的な変位の揺らぎを見積った。さらに、複数の二原子分子、恐らく分子性酸素がタンパク質と結合し、そのうちの一つは二量体界面の中央に位置する空洞から活性部位まで基質である二原子酸素のための進入経路として以前から提案されている領域に位置していた。

論文

A Methodological study extending an empirical model to predict self-leveling behavior of debris beds with non-spherical particles

Cheng, S.; 田上 浩孝; 山野 秀将; 鈴木 徹; 飛田 吉春; 中村 裕也*; Zhang, B.*; 松元 達也*; 守田 幸路*

Proceedings of International Conference on Power Engineering 2013 (ICOPE 2013) (USB Flash Drive), 6 Pages, 2013/10

In our previous publications, a simple empirical model, with its wide applicability confirmed over various experimental conditions, has been successfully proposed to predict the debris bed self-leveling behavior of spherical particles. Based on existing experimental knowledge obtained, in this study a methodological framework is developed with the purpose of extending its predicative capability for non-spherical particles. The proposed framework principally consists of two empirical terms - with one for correcting the terminal velocity of single non-spherical particles, which is the key parameter in our modeling, and the other for representing the additional particle-particle interactions caused by the shape-related parameters. Through the preliminary analyses, it was found that by linking the Geldart's method with our recently developed pressure-drop measurement facility, the terminal velocity of irregularly-shaped particles can be readily achieved, while for modeling the additional particle-particle interactions, based on the latest data available a parametric study is also conducted to identify the potential contributors.

論文

An Experimental investigation on self-leveling behavior of debris beds using gas-injection

Cheng, S.; 山野 秀将; 鈴木 徹; 飛田 吉春; 権代 陽嗣*; 中村 裕也*; Zhang, B.*; 松元 達也*; 守田 幸路*

Experimental Thermal and Fluid Science, 48, p.110 - 121, 2013/07

 被引用回数:13 パーセンタイル:29.21(Thermodynamics)

Although in the past, several experiments have been conducted to investigate the self-leveling behavior of debris beds, most of these were under comparatively lower gas velocities, the findings of which might be not directly applicable to actual reactor accident conditions. Current experiments were conducted using gas-injection in a large-scale cylindrical tank, in which nitrogen gas, water and different kinds of solid particles, simulate the fission gas, coolant and fuel debris, respectively. During experiments, to accomplish the bubble-based leveling as expected in reactor conditions, two experimental approaches, termed respectively as the gas pre-charge method and the pressure-adjustment method, have been attempted. Through elaborate comparisons and evaluations, it is found that compared to the gas pre-charge way the pressure-adjustment method can alleviate the liquid disturbance from bottom inlet pipelines more effectively. Further, based on experimental data using pressure-adjustment method, influence of particle size, particle density and gas flow rate on the leveling has been confirmed under current higher gas velocities. In addition, the liquid convection in the water pool, which is not evident within lower gas velocities, is observed to play an important role within current conditions, especially for experimental runs using larger-size but lower-density particles at rather higher gas flow rates.

論文

Recent knowledge from an experimental investigation on self-leveling behavior of debris bed

Cheng, S.; 山野 秀将; 鈴木 徹; 飛田 吉春; 中村 裕也*; 竹田 祥平*; 西 津平*; Zhang, B.*; 松元 達也*; 守田 幸路*

Proceedings of 21st International Conference on Nuclear Engineering (ICONE-21) (DVD-ROM), 8 Pages, 2013/07

To confirm the mechanisms of self-leveling behavior, several series of experiments were elaborately designed and performed in recent years under the constructive collaboration between Japan Atomic Energy Agency and Kyushu University. This paper summarizes the recent knowledge obtained from the newly developed large-scale experiments using gas-injection to simulate coolant boiling. Compared to previous investigations, it can cover a much wider range of gas velocities (presently up to a flow rate of around 300 L/min). The experiments were conducted in a cylindrical tank, in which water, nitrogen gas and different kinds of solid particles, simulate the coolant, vapor and fuel debris, respectively. Based on the quantitative data obtained, influence of various experimental parameters, including gas flow rate, water depth, particle size as well as particle density on the leveling was checked and compared. Moreover, with the help of dimensional analysis technique, a set of empirical correlations to predict the self-leveling development depending on particle size, particle density and gas injection velocity was proposed and validated over current conditions.

論文

Characteristics of self-leveling behavior of debris beds in a series of experiments

Cheng, S.; 山野 秀将; 鈴木 徹; 飛田 吉春; 中村 裕也*; Zhang, B.*; 松元 達也*; 守田 幸路*

Nuclear Engineering and Technology, 45(3), p.323 - 334, 2013/06

 被引用回数:22 パーセンタイル:5.42(Nuclear Science & Technology)

During a hypothetical core-disruptive accident (CDA) in a sodium-cooled fast reactor (SFR), degraded core materials can form conically-shaped debris beds over the core-support structure and/or in the lower inlet plenum of the reactor vessel from rapid quenching and fragmentation of core material pool. However, coolant boiling may lead ultimately to leveling of the debris bed that is crucial to the relocation of molten core and heat-removal capability of debris bed. To clarify the mechanisms underlying this self-leveling behavior, a great amount of experiments were performed within a variety of conditions in recent years under the constructive collaboration between Japan Atomic Energy Agency (JAEA) and Kyushu University (Japan). The present contribution synthesizes and gives detailed comparative analyses of those experiments. Effects of various experimental parameters that may have potential influence on the leveling process such as boiling mode (bottom-heated, depressurization boiling and gas injection), particle size, particle density, particle shape (spherical and non-spherical), boiling intensity (or gas flow rate), water depth along with column geometry, were investigated, thus, giving a large palette of favorable data for better understanding of CDAs and improved verifications of computer models developed in advanced fast reactor safety analysis codes.

論文

Empirical correlations for predicting the self-leveling behavior of debris bed

Cheng, S.; 山野 秀将; 鈴木 徹; 飛田 吉春; 中村 裕也*; Zhang, B.*; 松元 達也*; 守田 幸路*

Nuclear Science and Techniques, 24(1), p.010602_1 - 010602_10, 2013/02

Studies on the self-leveling behavior of debris bed are crucial for the assessment of core-disruptive accident (CDA) occurred in sodium-cooled fast reactors (SFR). To clarify this behavior over a wide range of gas velocities, a series of experiments was performed by injecting nitrogen gas uniformly from a pool bottom. Current experiments were conducted in a cylindrical tank, in which water, nitrogen gas and different kinds of solid particles, simulate the coolant, vapor (generated by coolant boiling) and fuel debris, respectively. Based on the quantitative data obtained (mainly the time variation of bed inclination angle), with the help of dimensional analysis technique, a set of empirical correlations to predict the self-leveling development depending on particle size, particle density and gas injection velocity was proposed and discussed. It was seen that good agreement could be obtained between the calculated and experimental values. Rationality of the correlations was further confirmed through detailed analyses of the effects of experimental parameters such as particle size, particle density, gas flow rate and boiling mode. In order to facilitate future analyses and simulations of CDAs in SFRs more efficiently, the obtained results in this work will be incorporated into advanced fast reactor safety analysis codes.

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