Role of laves intermetallics in nuclear waste disposal1

Laves intermetallics (AB2 compounds) play an important role in the disposal of metallic waste resulting from the electrometallurgical treatment of spent nuclear fuel. These ZrFe2-type intermetallics incorporate and immobilize highly radioactive and long-lived constituents that are present in waste forms based on the stainless steel–zirconium (SS–Zr) alloys. This paper reviews the metallurgy of SS–Zr alloys with emphasis on Laves intermetallic behavior. Microscopy and diffraction studies have shown that all actinide elements and most fission product elements are present only in the ZrFe2-type intermetallics of a stainless steel–15 wt.% zirconium (SS–15Zr) waste form, whereas only molybdenum is incorporated in the ZrFe2-type intermetallics of a zirconium–8 wt.% stainless steel (Zr–8SS) alloy. Because of the importance of material durability to waste disposal, recent experiments have been aimed at determining the corrosion behavior of these intermetallics. Results from transmission electron microscopy of corrosion layers observed on the ZrFe2-type compounds are presented.