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論文

Thorium oxide dissolution in HNO$$_{3}$$-HF mixture; Kinetics and mechanism

Simonnet, M.; Barr$'e$, N.*; Drot, R.*; Le Naour, C.*; Sladkov, V.*; Delpech, S.*

Radiochimica Acta, 107(4), p.289 - 297, 2019/04

 パーセンタイル:100(Chemistry, Inorganic & Nuclear)

This paper is an attempt to find out thorium oxide dissolution mechanism in HNO$$_{3}$$-HF mixture. In a previous paper, several parameters effects on thorium oxide dissolution have been described, with specific focus on hydrofluoric acid effect, which can lead to an increase of the dissolution rate if present in small amount, but precipitates as ThF$$_{4}$$ at higher content. Based on this previous study, experimental data were fitted using several dissolution models in order to find out the best one. Finally, a revisited model based on literature and considering the ThF$$_{4}$$ formation was proposed. It describes the main steps of dissolution and is able to fit the experimental data for a wide range of solution compositions. This point is crucial since it allows considering an extrapolation of the established model to not-yet-studied conditions.

論文

蓄熱用溶融塩と腐食

古川 和男; 沼田 博雄*

防食技術, 29(4), p.185 - 195, 1980/00

蓄熱材として溶融塩は、(1)容積当りの熱容量が大きいこと,(2)化学的に安定であること,(3)低蒸気圧であることなどから、太陽熱利用などに注目されてきている。溶融塩組成としては無限の選択があるといえるが、物性値に関する予測は比較的容易であり、選択に困難はないといえる。最も理解されていないのは、容器材料との共存性である。その原理的な面はかならずしも不明確ではないが、過去の特殊な経験事実に頼りすぎて誤解されている面があり、それを整理し必要な精製操作を明かにしつつ次の諸溶融塩の腐食特性を解説した。(1)フッ化物,(2)塩化物,(3)水酸化物,(4)硝酸塩・亜硝酸塩,(5)炭酸塩。また、腐食モニターに関する新しい研究成果をも紹介した。この開発および質量移行現象の解明などが、特に重点的に研究すべき項目であることも指摘した。

論文

The Extraction of americium and europium nitrates by tri-n-octyl phosphine oxide in toluene

石森 富太郎; 藤野 威男; C.T.Rhee*

日本原子力学会誌, 4(12), p.837 - 844, 1962/00

抄録なし

口頭

Effect of phosphate modification on incorporation of caesium nitrate by calcium aluminate cement

入澤 啓太; Mcgahan, M.*; 目黒 義弘; 木下 肇*

no journal, , 

Calcium aluminate cement modified with phosphate (CAP) has been studied as one of the alternative cementitious matrices for the encapsulation of nuclear wastes, especially those containing reactive metals. Our previous study indicated a potential advantage in phosphate modification of this system for incorporation of CsNO$$_{3}$$. $$^{137}$$Cs is one of the key radioactive nuclides which causes the majority of the radioactivity in the earlier age of nuclear wastes, yet difficult to incorporate into cement systems due to the mobile nature of an alkaline element. The present study investigates the compositional effects on the CAP system, focusing on the effects of phosphate on the incorporation of CsNO$$_{3}$$. The CAP samples were prepared by mixing calcium aluminate cement (CAC) with the aqueous solution of sodium polyphosphate and CsNO$$_{3}$$. In order to keep the weight % of CsNO$$_{3}$$ constant in the prepared samples, the total weight of the matrix forming reagents (CAC and phosphate) were kept constant, as well as that of water. Only the balance between CAC and phosphate was changed to study the compositional effects. All samples were cured up to 28 days in a sealed container under ambient condition.

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