Ruthenium Nitrosyl Complexes in Radioactive Waste Solutions of Reprocessing Plants

Abstract

Ruthenium complexes [Radioactive v/aste solutions /Reprocessing / Nitrosyl complexes of ruthenium SummaiyThe content of neutral ruthenium nitrosyl nitrato complexes found in high-level wastes (HLW) is similar to that in pure nitric solutions. Solutions with a high salt content, such as feed-solution or concentrated HLW (HLWC), contain a higher percentage of neutral complexes. The introduction of nitrous gases into simulated HLWC causes a lasting change of the complex equilibria by formation of nitro and nitro-nitrato complexes. After 30 days storage at 60 °C, the composition of the solutions treated with nitrous gases is practically the same as in the simulated HLWC stored for 30 days at 60°C. As to the latter Solution, a storage of 7 days is sufficient for experiments on the volatility of ruthenium during vitrification.

Volatilization of Ruthenium, Caesium and Technetium from Nitrate Systems in Nuclear Fuel Processing and Waste Solidification

“…The chemical form of ruthenium in process solutions has been well characterized [1][2][3][4] as octahedral nitro and nitrato complexes of nitrosylruthenium Ru(NO)(III). A solution of these compounds in nitric acid was used as the starting material.…”

Effect of ozone on ruthenium species in alkaline medium – Part I: Oxidative dissolution of ruthenium dioxide hydrate

“…The chemistry of ruthenium is very complicated. After dissolution of nuclear spent fuel in nitric acid, ruthenium can be found in solution as ruthenium nitrosyl complexes [1][2][3][4][5] which can interfere during the separation of uranium and plutonium from the other fission products. Oxidation of these ruthenium complexes by nitric acid can generate RuO 4 [6], which volatilized in the gas phase accelerating the corrosion of process equipment, and can cover and contaminate a number of materials with a nonvolatile RuO 2 deposit [7].…”

Incidences des procédés d'épuration appliqués aux effluents industriels sur le comportement chimique du ruthénium 106 dans l'environnement marin. Cas des rejets de l'usine de retraitement des combustibles irradiés de La Hague

“…La spécificité de l'opération d'extraction U-Pu par la phase TBP -dodécane est cependant susceptible d'être contrariée par la présence de la structure trinitrato, RuNO(N0 3 ) 3 (H 2 0) 2 (Nikol'skii et Shmidt, d'après [3]). La substitution des ligands aquo du complexe trinitrato par deux molécules de TBP aboutit au complexe RuNO(N0 3 ) 3 (TBP) 2 soluble dans la phase contenant U et Pu (Zvyagintsev, d'après [3] et [5]). Selon Sato [25], les complexes du nitrosylruthénium les plus stables en milieux aqueux sont formés par substitution de ligands forts tels que NO*, NO + et NO2" aux groupements faibles nitrato et aquo.…”