[en] A technique for the weld-sealing of lids in containers for Pu²³⁸O₂ used as a heat source cell in cardiac pacemakers is in the first stage of development. This stage includes the manufacture of the welding box by the TIG method, tests with containers of stainless steel and pure tantalum and the development of optimal conditions for sealing the inner containers made of Ta/10% W. The control during all the staaes is also discussed. (author)

No abstract available

[en] Dilute U-Ga alloys display a variety of metastable structures at room temperature. The addition of 1.5 at.% Ga and rapid cooling from the β-U or the γ-U phase region allow the retention at room temperature of the β-U structure. At the ambient, β-U is metastable and undergoes a shear-like isothermal transformation into α', a distorted α-U-like structure. This transformation is accompanied by severe surface deformation effects. The α'-U structure, with the same composition as the β-U solid solution from which it was formed, decomposes after an aging treatment into a two-phase structure consisting of virtually gallium-free α-U and the intermetallic compound U₃Ga₅. The higher the gallium content of the initial alloy, the more sluggish the martensitic transformation into the α' structure. At a higher gallium content and slower cooling rates, U₃Ga₅ Widemanstatten platelets are formed while the adjacent, gallium-depleted matrix reverts to the α-U structure. (orig.)