A secondary, high temperature electrochemical cell especially adapted for lithium alloy negative electrodes, transition metal chalcogenide positive electrodes and alkali metal halide or alkaline earth metal halide electrolyte is disclosed. The cell is held within an elongated cylindrical container in which one of the active materials is filled around the outside surfaces of a pluraity of perforate tubular current collectors along the length of the container. Each of the current collector tubes contain a concentric atubular layer of electrically insulative ceramic as an interelectrode separator. The active material of opposite polarity in elongated pin shape is positioned longitudinally within the separator layer. A second electrically conductive tube with perforate walls can be swagged or otherwise bonded to the outer surface of the pin as a current cllector and the electrically insulative ceramic layer can be coated or otherwise layered onto the outer surface of this second current collector. Alternatively, the central pin electrode can include an axial core as a current collector.

A reusable system is described for removably attaching the upper end of a nuclear reactor duct tube to the lower end of a nuclear reactor fuel assembly handling socket. A transition ring, fixed to the duct tube's upper end, has an interior-threaded section with a first locking hole segment. An adaptor ring, fixed to the handling socket's lower end has an outside-threaded section with a second locking hole segment. The inside and outside threaded sections match and can be joined so that the first and second locking hole segments can be aligned to form a locking hole. A locking ring, with a locking pin, slides over the adaptor ring so that the locking pin fits in the locking hole. A swage lock or a cantilever finger lock is formed from the locking cup collar to fit in a matching groove in the locking ring to prevent the locking ring's locking pin from backing out of the locking hole.