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天野 宰; 芝田 陵大; 佐藤 義治; 山崎 勝幸; 白茂 英雄; 中村 仁宣
Proceedings of INMM & ESARDA Joint Annual Meeting 2023 (Internet), 6 Pages, 2023/05
日本では、原子力事業者に核セキュリティ文化の醸成活動を義務付けられてからおよそ10年が経過した。この間、世界の原子力情勢は大きく変化し、法令遵守や核セキュリティ文化を重視する姿勢がますます重要になっている。原子力機構では、法令遵守及び核セキュリティ文化醸成活動方針を理事長が定め、その方針に基づいて、本部及び全国6か所の拠点で様々な活動が行われている。最終的には、これらの活動結果について、毎年評価し、改善を行ってきている。事例研究は、核セキュリティ上のリスクに対する感受性、法律の正しい理解等、法令遵守や核セキュリティ文化醸成のためのスキルを身につけることができる活動の一つである。事例研究の手順は、危険余地トレーニング(KYT)の手法を参考に作成した。KYTは、参加者(グループ)が4つの質問を通じて、事例への対応方法を議論するトレーニングである。まず、参加者には、核セキュリティ上のリスクがある想定事例のイラストと説明文が与えられる。その後、グループ内で4つの設問に従い、ディスカッションを行う。このグループディスカッションを通じて、参加者は核セキュリティのリスクを効果的に認識することができる。2022年度の事例研究では、核セキュリティ担当者、警備員、一般職員等、参加者の役割に応じて自由に事例を選択できるように23事例を用意した。事例研究の実施後、有効性評価のため、参加者に対し、アンケートへの記入を求めた。アンケートの結果、事例研究は核セキュリティリスクに対する感度の向上と法律の正しい理解につながることが示された。全体として、事例研究結果より、JAEAの取り組みは核セキュリティ文化の維持・向上させるのに十分であることを示唆していた。
天野 宰; 佐藤 義治; 芝田 陵大; 山崎 勝幸; 白茂 英雄; 中村 仁宣
第43回日本核物質管理学会年次大会会議論文集(インターネット), 4 Pages, 2022/11
核セキュリティの法令遵守及び文化醸成活動が導入され10年が経過した。国内外の情勢に変化もある中、組織全体において、法令遵守及び核セキュリティを重視する姿勢の維持は、核セキュリティ上必要不可欠である。原子力機構では、組織全体で、評価改善を行いつつ、種々の活動を効果的に実施している。特に、教育と意識付けを両立したeラーニング、気付きを題材とした事例研究、及び内部監査は、これらの維持に効果的と考えられる。
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 (
300 L/min), water depth (180 mm and 400 mm), bed volume (3 7 L), particle size (1 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.
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.
市川 行和*; 高木 秀一*; 中村 義春*; 今井 誠*; 佐々木 明
プラズマ・核融合学会誌, 89(9), p.600 - 610, 2013/09
IAEAにおける原子分子データのCoordinated Research Projectにおける、原子分子データの検証やコード比較の活動のひとつとして、nLTE(non local thermodynamic equilibrium)コード比較ワークショップについて紹介する。原子分子データを、核融合のような基礎科学や、EUV光源のような産業応用に用いる際には、衝突輻射モデルによって、状態の占有密度や輻射損失を評価することが重要である。高Z多価イオンの原子過程は複雑で、モデルの実験による検証が困難だったことで、従来、計算結果には不確定性があったが、衝突輻射モデルの研究者が集まり、決められたテスト問題を実行して結果を比較する当該ワークショップを実施したことにより、Wプラズマの価数の温度変化等を正確に計算できるようになった。
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：18 パーセンタイル：61.83(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.
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.
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：38 パーセンタイル：93.87(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.
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.
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*
Proceedings of 8th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-8) (USB Flash Drive), 10 Pages, 2012/12
Studies on self-leveling behavior of debris bed are crucial for the assessment of core-disruptive accident (CDA) occurred in sodium-cooled fast reactors (SFR). Although in the past, several experiments have been conducted to investigate this behavior, most of these were under comparatively lower gas velocities, the findings of which might be not directly applicable to actual reactor accident conditions. To further clarify this behavior, a series of experiments has been performed by percolating nitrogen gas uniformly from pool bottom. Current experiments were conducted in a 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 alleviate the liquid disturbance from the bottom inlet pipelines, within the upper region of the test tank a condition of comparatively lower pressure was created. It is found that in this way the bubble-based leveling as expected in actual reactor accident conditions can be achieved effectively throughout the whole experimental process. Further, based on the quantitative data obtained, influence of various experimental parameters, including gas flow rate (up to 300 L/min), water height (180 mm, 400 mm), particle size (2 6 mm), particle density as well as column geometry on the leveling was checked and compared. Current work provides fundamental data for better understanding and improved estimation of CDAs in SFRs.
Cheng, S.*; 甲斐 貴之*; 権代 陽嗣*; 中村 裕也*; 浮池 亮太*; Zhang, B.*; 松元 達也*; 守田 幸路*; 山野 秀将; 田上 浩孝; et al.
Proceedings of 4th International Symposium on Heat Transfer and Energy Conservation (CD-ROM), 5 Pages, 2012/01
There is a possibility of the formation of conically-shaped debris bed over the core-support structure and/or in the lower inlet plenum of the reactor vessel, postulates core disruptive accident (CDA) in a sodium-cooled fast reactor (SFR). However, coolant boiling may lead ultimately to leveling of the debris bed. In this study, nitrogen gas was used to clarify this behavior percolating uniformly through particle beds. Wide ranges of experimental parameters were used. Based on the experimental data, a simple empirical approach was suggested to evaluate the transient variation in the bed inclination angle during the leveling. Validation of this approach was confirmed through analyses of the effects of experimental parameters, while its applicability to extended conditions (different initial inclination angles) was further validated by several typical experimental cases.
坂中 章悟*; 明本 光生*; 青戸 智浩*; 荒川 大*; 浅岡 聖二*; 榎本 収志*; 福田 茂樹*; 古川 和朗*; 古屋 貴章*; 芳賀 開一*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05
日本においてERL型放射光源を共同研究チームで提案している。電子銃,超伝導加速空洞などの要素技術開発を進めている。また、ERL技術の実証のためのコンパクトERLの建設も進めている。これら日本におけるERL技術開発の現状について報告する。
中村 裕也*; 権代 陽嗣*; Cheng, S.*; 竹田 祥平*; Zhang, B.*; 松元 達也*; 守田 幸路*; 山野 秀将; 田上 浩孝; 鈴木 徹; et al.
no journal, ,
高速炉炉心損傷事故時の崩壊熱除去過程におけるデブリベッドの運動挙動を明らかにするため、固体粒子ベッド底面からの気相吹き込みによって冷却材沸騰を模擬した試験研究を実施し、比較的大きな気相流量条件下でのセルフレべレリング特性について基礎的な知見を得た。
今橋 淳史; 中村 圭佑; 渡邊 裕貴; 並木 篤; 高橋 芳晴*; 衣川 信之*
no journal, ,
近年、様々な分野にてウェアラブル端末を用いた無線通信方式の機器開発及びその実用化が活発となっている。これを放射線作業管理に応用することで、リアルタイムの線量情報や作業場所に関する情報の取得が可能となり、より安全で効率的な放射線作業管理が期待される。そこで本研究では、再処理施設におけるセル内放射線作業の作業管理の高度化を目的として、無線通信機能を有する線量計及びメガネ型表示端末を組み合わせた放射線作業管理システムの現場適用性評価を行った。
加藤 徹也*; 中村 勤也*; 坂村 義治*; 岩井 孝; 荒井 康夫
no journal, ,
原子力機構と電中研では、高速実験炉「常陽」を用いて被覆管最高温度650
Cを達成する金属燃料の高温照射試験の準備を進めている。本報告は、照射試験用金属燃料の原料となるU-Pu合金の調製と射出鋳造法を用いたU-Pu-Zr合金スラグの製造試験に関するものである。U-Pu合金は、U-Pu混合酸化物ペレットをLiCl-Li
O浴塩中で電解還元することにより調製する。電解還元後のペレットの断面観察によりほぼ全量のU-Puを還元できることを確認した。U-Pu合金に付着した浴塩を減圧下で1000Cに加熱することにより蒸留除去した後、射出鋳造に適したインゴットとした。射出鋳造試験では、U-8.5wt%Pu-10.0wt%Zrの組成の合金スラグを製造した。得られた合金スラグの表面は滑らかであり、成分組成は全長に渡り均質であった。
