Method of control of combustible gas within a nuclear container

Object: To dispense with recirculation gas in a reaction step for recombination of oxygen and hydrogen produced from decomposition of leaking water occurring due to such cause as breakage of the recirculation system duct by previously pouring non-combustible gas into the gas supplied to the reaction step. Structure: The concentration of oxygen and the concentration of hydrogen within the nuclear container are detected after an accident, and non-combustible gas is then supplied into the nuclear container by opening a non-combustible gas bomb valve according to the results of the detection such that hydrogen concentration within the container is always held below 4%. In this way, the quantity of oxygen reacted in a recombiner is reduced to below 2% without recirculating the gas. (Kamimura, M.)