[en] The fundamental phenomena of reaction runaway of alkali metals were studied. Ignition of molten sodium metal was observed at 115degC and 120degC. The vapor layer ignited at 700degC. An orange emission was observed at the upper side of molten sodium metal liquid drop and moved to lower side at 1 mm/sec of velocity. After disappearing emission at 600degC, a propagation phenomenon of flame was observed. Asphalt solidification with sodium bicarbonate had large reaction activity and generated the oxidation-reduction exothermic reaction at about 132degC. If the above solidification is filled in drum can at 180degC, a fire explosion accident might result in thermal storage. (S.Y.)