NOVELTY - Reactor (400) for removal of carbon monoxide (CO) from reformate stream, comprises: (i) housing; and (ii) flow path within housing and configured to bifurcate reformate stream into permeate branch and retentate branch. Flowpath comprises: (a) a shift subreactor to convert some CO resident in reformate stream into hydrogen and carbon dioxide; (b) gaseous diffusion membrane subreactor; and methanation subreactor(s).    USE - The reactor is used for the removal of carbon monoxide from a reformate stream. It is also used for a fuel processing system for a proton exchange membrane fuel cell, for a power production system, or for fuel purification system for a vehicle (claimed).    ADVANTAGE - The concentration of carbon monoxide in the reformate is reduced to very low levels while simultaneously minimizing the weight, cost, complexity and space occupied by the fuel processing components.    DETAILED DESCRIPTION - Reactor for the removal of carbon monoxide from a reformate stream, comprises:    (a) housing; and    (b) flow path within the housing and configured to bifurcate the reformate stream into a permeate branch and a retentate branch.    The flowpath comprises:    (1) a shift subreactor to convert some carbon monoxide resident in the reformate stream into hydrogen and carbon dioxide;    (2) gaseous diffusion membrane subreactor in fluid communication with the shift subreactor, and configured to allow a hydrogen-rich portion of the reformate stream to pass through and into the permeate branch; and    (3) methanation subreactor(s) in downstream fluid communication with the gaseous diffusion membrane subreactor, and configured to further purify the hydrogen-rich portion of the reformate stream in the permeate branch.    An INDEPENDENT CLAIM is also included for a method of delivering fuel to a fuel cell system, comprising:    (A) configuring a fuel supply to include a fuel source, oxygen source and reformer configured to evaporate a mixture of fuel and oxygen from the fuel and oxygen sources;    (B) configuring a reactor for the removal of carbon monoxide from a reformate stream produced by the fuel supply;    (C) introducing fuel from the fuel source to oxygen from the oxygen source to create a fuel-oxygen mixture;    (D) evaporating the fuel-oxygen mixture such that the reformate stream is produced;    (E) purifying the reformate stream in the reactor; and    (F) transporting the hydrogen-rich portion of the reformate stream in the permeate branch to the fuel cell.    DESCRIPTION OF DRAWING(S) - The figure shows a block diagram of a mobile fuel cell system, including a fuel processing sub-system.    Fuel supply (100)    Oxygen supply (200)    Reformer (300)    Reactor (400)    Fuel cell (500)