NOVELTY - An integrated steam reformer/combustor assembly (42), comprises housing (44, 58) defining two axially extending, concentric annular passages; first convoluted fin (46) located in first passage to direct feed mix, and coated with catalyst that induces desired reaction in feed mix; and second convoluted fin (50) located in second passage to direct combustor feed, and coated with catalyst that induces desired reaction in combustor feed.    USE - The integrated steam reformer/combustor assembly is used in fuel processing system that supplies steam/fuel feed mix to be reformed in assembly and combustor feed to be combusted in assembly (claimed). The fuel processing system is used for distributed hydrogen production.    ADVANTAGE - The fuel processing system incorporating the steam reformer/combustor assembly overcomes the heat transfer limitations of previous designs, and is thus capable of achieving a high level of hydrogen product efficiency without extremely high metal temperatures.    DETAILED DESCRIPTION - An integrated steam reformer/combustor assembly for use in fuel processing system that supplies steam/fuel feed mix to be reformed in assembly and combustor feed to be combusted in assembly, comprises:    (1) a housing defining first and second axially extending, concentric annular passages in heat transfer relation to each other, the first passage open at a first end to receive the feed mix into the first passage and open an opposite end to direct the feed mix from the first passage, the second passage is open at a location adjacent the opposite end to direct the combustor feed into the second passage and open at a location adjacent the first end to direct the combustor feed from the second passage;    (2) a first convoluted fin located in the first passage to direct the feed mix, the first convoluted fin coated with a catalyst that induces a desired reaction in the feed mix; and    (3) a second convoluted fin located in the second passage to direct the combustor feed, the second convoluted fin coated with a catalyst that induces a desired reaction in the combustor feed.    An INDEPENDENT CLAIM is also included for an integrated fuel processing unit, comprising:    (1) a housing;    (2) a steam/fuel feed mix supply in the housing;    (3) a combustor feed supply in the housing; and    (4) a steam reformer/combustor in the housing.    DESCRIPTION OF DRAWING(S) - The figure is a section view of an integrated fuel processing unit.    Pressure swing absorption (22)    Steam reformer/combustor assembly (42)    Housing (44, 58)    First convoluted fin (46)    Second convoluted fin (50)    Cylinders (80, 90)    Inside surfaces (100, 102)