Hydrogen release reaction from sodium hydride with different sample quantities

土井 大輔

Proceedings of 29th International Conference on Nuclear Engineering (ICONE 29) (Internet), 7 Pages, 2022/08

https://doi.org/10.1115/ICONE29-91847

In sodium-cooled fast reactors (SFRs), hydrogen is a major nonmetallic impurity in the coolant during normal operation. A higher hydrogen concentration than the gas-liquid equilibrium had been transiently detected in the gas space of the actual SFR plant. However, the chemical reactions that caused hydrogen generation, which involve several sodium compounds, have not been identified. Furthermore, the thermal behavior of these hydrogen release reactions has not been thoroughly investigated. In this study, the hydrogen release behavior of sodium hydride, which could be involved in all of these reactions, was clarified by two experimental methods dealing with different sample quantities. In the thermal analysis with a semi-micro sample of about 1mmol, the hydrogen generation was demonstrated by mass spectrometry as the sample mass decreased, suggesting thermal decomposition. A monomodal hydrogen release curve similar to the thermal analysis result was obtained in the heating experiment with a macro amount sample of about 1mol. These experimental results showed consistent activation energies within the standard error. Therefore, it was elucidated that the ideal reaction behavior obtained by thermal analysis could be sufficiently extrapolated to the reaction behavior occurring in a larger amount of sample. These findings provide fundamental insights into the thermal decomposition of sodium hydride and are indispensable for analyzing hydrogen release behavior in other hydrogen release reactions involving sodium hydride.

Visualizing an ignition process of hydrogen jets containing sodium mist by high-speed imaging

土井 大輔; 清野 裕; 宮原 信哉*; 宇埜 正美*

Journal of Nuclear Science and Technology, 56(6), p.521 - 532, 2019/06

https://doi.org/10.1080/00223131.2019.1599743

In severe accident scenarios for sodium-cooled fast reactors, it is desirable to gradually consume hydrogen generated by various ex-vessel phenomena without posting a challenge to containment integrity. An effective means is combustion of hydrogen jets containing sodium vapor and mist, but previous studies have been limited to determining ignition thresholds experimentally. The aim of this study was to visualize the ignition process in detail to investigate the ignition mechanism of hydrogen-sodium mixed jets. The ignition experiments of the hydrogen jet containing sodium mist were carried out under a condition of little turbulence. The ignition process was measured with an optical measurement system comprised of a high-speed camera and an image intensifier, and a spatial distribution of luminance was analyzed by image processing. Detail observation revealed that sodium mist particles burned as scattering sparks inside the jet and that hydrogen ignited around the mist particles. Additionally, the experimental results and a simple heat balance calculation indicated that the combustion heat of sodium mist particles could ignite the hydrogen as the heterogeneous ignition source in the fuel temperature range where the mist particle formation was promoted.

An Experimental study on natural circulation decay heat removal system for a loop type fast reactor

小野 綾子; 上出 英樹; 小林 順; 堂田 哲広; 渡辺 収*

Journal of Nuclear Science and Technology, 53(9), p.1385 - 1396, 2016/09

https://doi.org/10.1080/00223131.2015.1121844

自然循環方式崩壊熱除去系は全電源喪失時の高速炉における受動的安全性として重要である。日本で設計がすすめられているループ型高速炉の崩壊熱除去系は、DRACSおよびPRACSより構成される。自然循環状態のプラント内熱流動現象を把握することは信頼性の高い完全自然循環方式崩壊熱除去系を開発するために必要である。本研究では、プラントにおける自然循環を考慮した熱流動現象を理解するためにプラント過渡応答試験施設を用いたナトリウム試験を実施した。スクラム過渡を模擬したナトリウム試験はPRACSが自然循環条件でスムーズに起動すること、スクラム後に模擬炉心が安定に冷却されることを示した。さらに、ループの圧力損失係数を変化させた実験からは外乱事象に対するPRACSのロバスト性を示した。

IAEA NAPRO Coordinated Research Project; Physical properties of sodium

Passerini, S.*; Carardi, C.*; Grandy, C.*; Azpitarte, O. E.*; Chocron, M.*; Japas, M. L.*; Bubelis, E.*; Perez-Martin, S.*; Jayaraj, S.*; Roelofs, F.*; et al.

Proceedings of 2015 International Congress on Advances in Nuclear Power Plants (ICAPP 2015) (CD-ROM), p.780 - 790, 2015/05

The IAEA recently established a CRP on "Sodium properties and safe operation of experimental facilities in support of the development and deployment of Sodium Cooled Fast Reactors - NAPRO", to be carried out in the period 2013 - 2017. The first phase of the CRP is focused on the collection and assessment of sodium properties, and it will lead to a consistent property data set which will be published in the form of a handbook. This work is carried out by the 11 participating organizations from 10 Member States through the review and evaluation of the existing available data, the identification of the data gaps and the development of recommendations for experimental programmes to support closing these data gaps. A specific work package (WP 1.1), under the leadership of Argonne National Laboratory, is focused on the analysis of physical properties of sodium: thermodynamic properties and transport properties. The expected outcome includes the improved understanding of the availability, accuracy and range of applications of sodium properties centered on fast reactors and other technological applications. The implemented methodology for WP 1.1 is described and so the properties included in WP 1.1 and their classification. Major findings to date related to WP 1.1 are presented in this work, including detailed analysis of two selected properties.

FCAを使った金属燃料及び酸化物燃料高速炉模擬体系におけるナトリウムボイド反応度価値の測定と解析

大井川 宏之; 飯島 進

JAERI-Research 95-007, 93 Pages, 1995/02

JAERI-Research-95-007.pdf:2.7MB

高速炉のナトリウムボイド係数の予測精度向上に資することを目的として、FCAを使った金属燃料高速炉模擬体系XVI-1及びXVI-2、並びに、酸化物燃料高速炉模擬体系XVII-1の3集合体においてナトリウムボイド反応度価値を測定した。測定結果をJENDL-2、JENDL-3.1及びJENDL-3.2を用いて計算と比較し、ナトリウムボイド反応度価値を構成する非漏洩項及び漏洩項それぞれについて計算精度を評価した。

FCA VI-1集合体によるNaボイド実験とその解析; FCAによる高速原型炉模擬実験報告

白方 敬章; 三田 敏男*; 後藤 義則*; 黒井 英雄; 弘田 実彌

JAERI-M 9931, 41 Pages, 1982/02

JAERI-M-9931.pdf:1.34MB

高速原型炉「もんじゅ」の外側炉心の組成を模擬したFCA Vl-1集合体において各種のNa void効果、具体的にはチャンネル閉塞効果、軸方向分布、中心Void効果、広領域Void効果等を測定した。一方AGLIライブラリー、JAERI-Fastセット等を用いて測定結果の解析を行った。その結果、中心Na Void効果の問題点か明らかになり、中心Void効果の解析のためには詳細群の取り扱いが必要であること、Naの3KeVの共鳴の断面積の大きさが重要な役割を演じていること、そしてAGLI/0およびAGLI/1ライブラリーのNaの断面積には問題が残されていることが明らかになった。

Experimental Study of LMFBR Heterogeneous Core at FCA

中野 正文; 飯島 進; 白方 敬章; 弘田 実彌

JAERI-M 8117, 18 Pages, 1979/03

JAERI-M-8117.pdf:0.66MB

非均質高速炉心の核特性評価に関する基礎研究としてFcAVII-3集合体により一連の実験を行った。実験体系は炉心中心に盤状の内部ブランケット(IB)を入れた単純形状の円筒炉心であり、IBの組成や厚みを変えて、臨界性、Naポイド効果、サンプル反応度価値、反応率分布等を系統的に測定した。IB中心から炉心中央までのNaポイド効果は、IB内のUPu原子数密度の増加とともに減少する傾向が観測されたが、その変化はIBの組成にはあまり敏感ではない。IBの厚さが20cmから40cmに増すと炉心領域のNaポイド効果は約35%の減少を示した。IB厚さ30cmのFcAVII-3-1集合体について、JAERI-Fast VersionII、拡散近似による解析を行い測定値と比較した。計算値は低エネルギに感度の高いU(n,f)、U(n,)等をIBで過少評価する。Puサンプル反応度価値の計算値は炉心領域の測定値をよく再現できない。Naポイド効果のC/E値はIBと炉心の境界で20%以上の不連続性を示した。