NOVELTY - The high temperature electrolysis module comprises a sealed envelope (18) for containing water vapor including more than 1% of hydrogen or inert gas, a stack of elementary electrolytic cells of which each is formed of a cathode, an anode and an electrolyte interposed between the cathode and the anode, an interconnecting plate that is arranged between two adjacent elementary cells and is in electrical contact with an electrode of two elementary cells, a clamping unit (5), an electrically insulating part (50), and connectors. The interconnecting plate comprises a cathode compartment.    USE - The high temperature electrolysis module is useful in an ensemble (claimed) for electrolyzing water.    ADVANTAGE - The high temperature electrolysis module can be reliably and safely operated without the risk of leaks and efficiency losses, and exhibits good electrical conduction.    DETAILED DESCRIPTION - The high temperature electrolysis module comprises a sealed envelope (18) for containing water vapor including more than 1% of hydrogen or inert gas, a stack of elementary electrolytic cells of which each is formed of a cathode, an anode and an electrolyte interposed between the cathode and the anode, an interconnecting plate that is arranged between two adjacent elementary cells and is in electrical contact with an electrode of two elementary cells, a clamping unit (5), an electrically insulating part (50), and connectors. The interconnecting plate comprises a cathode compartment and an anode compartment for flowing gas to the cathode and the anode respectively. The electrolysis cell stack is housed in the sealed envelope. The sealed envelope is constituted of a housing comprising a bottom (180) and a lid. The stack of elementary electrolytic cells is assembled between two plates of which a lower plate is supported against the bottom of the housing by an electrical insulation. The clamping unit: is arranged partially between an upper plate and the cover of the housing; is adapted to provide a contact force determined by compression between the lower and upper plates of the cell stack and to apply a charge, by gravity, on the upper plate through bellows fixed with the lid of the housing; and comprises an additional plate having clearance fit mounted in the housing and directly contacted with the upper plate. The additional plate is adapted to be moved by the vapor from an external box through the lid for generating the clamping force between the lower and upper plates. The connectors are configured for allowing electrical connection to the electrolytic cell stack from the exterior of the housing.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic partial view of a high temperature electrolysis module.    Clamping unit (5)    Sealed envelope (18)    Fluidic connection (25)    Insulating part (50)    Bottom of housing. (180)