NOVELTY - The improved system comprises an insulated hydrogen production reactor (1) comprising a reaction chamber and a separation chamber, an insulated oxygen production reactor (5) comprising two major sections, first reactants feeding and reaction section and a second products removal section, and a feeder inlet for solid copper oxychloride (CuOCuCl2) reactant particles in the first section and an oxygen gas outlet at the top of the reactor and an outlet for molten copper chloride (CuCl) in the second section of the reactor located at a position below the position of the feeder inlet.    USE - The improved system is useful for producing hydrogen gas from water decomposition using a thermochemical copper chloride cycle, where the hydrogen gas is useful for a fuel.    ADVANTAGE - The improved system is capable of reliably, safely, efficiently and economically producing hydrogen gas from water decomposition with low temperature and enhanced product yield.    DETAILED DESCRIPTION - The improved system comprises an insulated hydrogen production reactor (1) comprising a reaction chamber and a separation chamber, an insulated oxygen production reactor (5) comprising two major sections, first reactants feeding and reaction section and a second products removal section, a feeder inlet for solid copper oxychloride (CuOCuCl2) reactant particles in the first section and an oxygen gas outlet at the top of the reactor and an outlet for molten copper chloride (CuCl) in the second section of the reactor located at a position below the position of the feeder inlet for CuOCuCl2, and a molten salt bath of the reaction product CuCl maintained in the reactor to ensure high heat transfer rate and efficiency for the reaction. The reaction chamber has a hydrogen chloride gas inlet and a solid copper inlet. The insulated hydrogen production reactor has levels provided in the reaction chamber, where the number of levels is dependant on production scale and pressure drop. Each level comprises a perforated plate with associated filter media. The perforations of the plate and media have decreased size from top to bottom of the reaction chamber, and are sized to permit downward flow of the hydrogen gas, molten CuCl products and the hydrogen chloride gas reactant and to prevent entrainment of solid copper in the molten CuCl products. The separation chamber is located below the reaction chamber, has greater cross-section than the reaction chamber and comprises a first hydrogen removal and entrained copper removal zone and a second molten CuCl removal zone. The removal of the reaction products is controlled to decrease the amount of entrained copper in the molten CuCl. The first zone has outlets for removal of hydrogen gas and entrained copper particles with the second zone having an outlet for removal of molten CuCl. The CuCl cycle comprises reacting copper and dry hydrogen chloride (HCL) gas at a temperature of 450 degrees C to obtain hydrogen gas and molten CuCl salt, subjecting solid CuCl and HCl to electrolysis at a temperature of 70-90 degrees C to obtain copper and an aqueous slurry containing HCl and copper chloride (CuCl2), heating the aqueous slurry at a temperature of 375-450 degrees C to obtain solid CuCl2 and water/HCl vapors, heating the solid CuCl2 and water to obtain CuOCuCl2 and gaseous HCl, and heating the solid CuOCuCl2 at a temperature of 500-530 degrees C to obtain molten CuCl salt and oxygen gas. Each of the filter media comprise layers of packings of inert materials or comprise a copper aggregation, which provides some of the copper in the reaction. The packings are balls or cylinders or rings made of suitable material for the reaction conditions. The first section extends into the base of the reactor and supplies heat to the reactor for the reaction. The feeder inlet has an associated feeder, which comprises a hopper for the CuOCuCl2 particles, a screw to force the particles into the first section of the reactor, and a double shell structure for the feeder in which lower temperature oxygen produced from the reaction is allowed to flow through to ensure that the particles remain in solid form in the feeder and to prevent reverse flow of the reaction products into the feeder. The heat for the reactor is provided by a heating jacket, a secondary molten salt/steam flow from inside the reactor to a double shell surrounding the reactor, a secondary flow of molten CuCl salt from outside the reactor, or a flow of steam to the heating channel. The secondary molten salt/steam flow circulates in the heating channel of the reactor and flows out and to a molten salt heating reservoir and then back to the heating channel of the reactor. The molten CuCl is fed into a quenching tower, where steam generation and molten salt processing are conducted such that water at ambient temperature is exposed to molten CuCl to produce slurry of solid CuCl and steam. The quenching tower is insulated, and has an associated molten salt collector in which molten CuCl streams are collected together before fed into a top portion of the quenching tower, steam outlets provided in a top portion of the quenching tower, a slurry outlet provided in a base portion of the tower and a water make-up inlet provided in the quenching tower. The system further comprises a steam circulating and heating apparatus comprising a buffer and settlement tank. The tank permits the steam under pressure from the tower to be circulated to a steam chamber associated with a nozzle. The steam flows downwardly and spins in the steam chamber to produce turbulent steam splitting the downwardly flowing molten CuCl entering the quenching tower, which is sprayed or atomized. The steam extracts more heat from the molten CuCl. An excess quantity of reactants HCl and copper are used by heat produced in the system recovered without employing extra recovery steps. The excess amount of HCl is up to 8 times the stoichiometric value. The excess amount of copper is up to 2.5 times of the stoichiometric value. An INDEPENDENT CLAIM is included for a process for producing hydrogen gas from water decomposition using a thermochemical copper chloride cycle.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a system for operating a five-step closed copper chloride thermochemical cycle for the production of hydrogen gas from water decomposition.    Hydrogen production reactor (1)    Electrolysis reactor (2)    Drying cell (3)    Copper chloride hydrolysis reactor (4)    Oxygen production reactor (5)    Steam generation unit. (8)