Abstract: A sodium-sulfur battery comprising molten sodium as an active material for a minus pole and molten sulfur as an active material for a plus pole, the molten sodium and molten sulfur being partitioned from each other by a sodium ion-permeating solid electrolyte such as .beta.-alumina as a boundary is provided with a sodium storage tank communicated with the molten sodium in the battery cell, a draining mechanism for withdrawing the molten sodium, when desired, from the battery cell into the sodium storage tank, and a circulating mechanism for purifying and returning the sodium from the sodium storage tank to the battery cell as the molten sodium, sodium can be discarged urgently from the battery at an accident of direct contact between the sodium and sulfur, with the result of improved safety.

Abstract: A sodium-handling apparatus is disassembled and repaired by (1) contacting an inert gas with the sodium-contacting surfaces within the apparatus after discharge of sodium from the apparatus, thereby solidifying the deposited sodium, (2) flushing the inert gas with a reacting gas capable of reacting with sodium, capable of being dissolved in sodium and capable of forming a weak alkali therein, thereby forming a solid film of a neutral salt on surfaces of the deposited sodium by reaction of sodium with the reacting gas, (3) discharging the reacting gas from the apparatus, (4) disassembling and repairing the apparatus in the atmosphere, and then (5) continuing operation of the apparatus while the solid film is being retained on the surfaces of the apparatus.