Investigation of caesium retention by potassium nickel hexacyanoferrate (II) in different pH conditions and potential effect on the selection of storage matrix

Isabelle Martin (1) , Cédric Patapy (1) , Cedric Boher (2) , Martin Cyr (1)

1 LMDC - Laboratoire Matériaux et Durabilité des constructions
2 Orano Projets

The chemical stability and caesium retention properties of a nonstoichiometric compoundK2-xNix/2[NiFe(CN)6].nH2O (KNiFCN) was studied in different pH conditions. Different solutions with controlled pH were prepared. Leaching tests were done with chemical analysis of the solutions. The compound was characterized before and after exposure by chemical analysis, SEM-BSE, X-ray diffraction and infrared spectroscopy. The face-centered cubic (FCC) structure of KNiFCN without caesium was stable even in presence of 1 g/l HNO3 (pH equal 2) or NaOH (pH equal 13). In presence of caesium trapped on KNiFCN structure, it appears that the increase in caesium content change the KNiFCN structure, thus influencing the retention properties in KNiFCN according to the pH of the solution. The KNiFCN structure was decomposed when the NaOH concentration exceeds 1 g/l (pH equal 14), probably due to the hydrolysis of constitutional elements. A selection of cementitious matrix is the proposed to satisfy stability conditions of this compound.

Mots clés: Nuclear waste solution; pH value; Chemical stability; Potassium nickel hexacyanoferrate (II); Caesium (noticed Cs)

Domaines: Sciences de l'ingénieur [physics]; Génie civil

Isabelle Martin, Cédric Patapy, Cedric Boher, Martin Cyr. Investigation of caesium retention by potassium nickel hexacyanoferrate (II) in different pH conditions and potential effect on the selection of storage matrix. Journal of Nuclear Materials, 2019, 526, pp.151764. ⟨10.1016/j.jnucmat.2019.151764⟩. ⟨hal-02428595⟩