NOVELTY - A reactor (A1) comprises a reactor chamber containing a catalyst bed adapted to produce reaction products containing hydrogen gas from a hydrogen-producing feedstock; and at least one hydrogen-selective, hydrogen-permeable gas separation module adapted to receive the reaction products from the catalyst bed and to separate the reaction products into a product stream comprising hydrogen and a byproduct stream.    USE - As reactor useful in the production of hydrogen, which is useful in hydrogen fuel cell (claimed).    ADVANTAGE - The reactor produces high purity hydrogen (i.e. purity of greater than 95%, preferably 99%) from hydrogen producing feedstock. The process is accomplished in one reactor, constantly removing pure hydrogen, and optionally using distributed combustion as a heat source, which provides great improvements in heat exchange efficiency and load-following capabilities to drive the steam reforming reaction. The hydrogen-selective gas separation module has thinner dense gas-selective membrane producing higher rates of gas flux, e.g. hydrogen flux, while durability (including reduced diffusion of substrate components), hydrogen permeation as well as selectivity are maintained or improved. Moreover, at bulk-hydrogen production scales, a multi-tubular (multiple distributed combustion tubes and/or multiple hydrogen selective and permeable membrane tubes) containing reactor provides the modularity needed. A producer can match the desired capacity by installing multiple reactor units of the specific design or having multiple distributed combustion tubes and/or multiple hydrogen selective and permeable membrane units in a large steam reformer. This is more cost-effective than either trying to scale up or down the existing large box furnace reactor designs or building several thousand single-tube reactors.    DETAILED DESCRIPTION - A reactor (A1) comprises a reactor chamber containing a catalyst bed adapted to produce reaction products containing hydrogen gas from a hydrogen-producing feedstock; and at least one hydrogen-selective, hydrogen-permeable gas separation module adapted to receive the reaction products from the catalyst bed and to separate the reaction products into a product stream comprising hydrogen and a byproduct stream. The gas separation module comprises a porous substrate, an intermediate porous metal layer overlying the porous substrate, and a hydrogen-selective membrane overlying the intermediate porous metal layer. INDEPENDENT CLAIMS are included for the following:    (1) a steam reforming process for the production of hydrogen involving reacting steam with a hydrogen-producing feedstock at 200 - 700degreesC and at a pressure of 0.1 - 20 MPa in a steam reforming reaction chamber containing a reforming catalyst to produce a mixture of hydrogen and carbon dioxide with a lesser amount of carbon monoxide; and separating hydrogen from the reaction chamber and from the carbon dioxide and the carbon monoxide with a hydrogen-selective, hydrogen-permeable gas separation module; and    (2) an integrated steam reforming reactor-hydrogen fuel cell comprising (A1), where the product stream containing hydrogen is delivered from the reactor to an anode compartment of a hydrogen fuel cell and the byproduct stream from the reactor is delivered to a cathode compartment of the hydrogen fuel cell.