NOVELTY - A reactor vessel has reaction chamber(s) and coolant chamber(s), and reactor plate(s) with two opposing faces. The first face defines a portion of reaction chamber and the second face defines a portion of coolant chamber. The reaction chamber receives the hydride solution and contacts at least a portion of the hydride solution with a catalyst. The coolant chamber receives a coolant flow.    USE - The reactor vessel is used for generating hydrogen from a hydride solution by contacting a catalyst with the hydride solution, providing a coolant flow proximate to the hydride solution, and controlling the temperature and/or flow rate of the coolant flow (claimed). It can be used for hydrogen consuming devices such as fuel cells, engines and turbines.    ADVANTAGE - The reactor provides improved thermal management of the hydride solution and more uniform contact between catalyst and hydride solution. It also provides improved scalability, reaction temperature control and load following ability. The reactor can provide a better control of the reaction rate and more uniform heat transfer and use of catalyst. It is simple to manufacture and assemble, and easy to scale up.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) the reactor plate; and    (2) a system for generating hydrogen from a hydride solution in presence of a catalyst, comprising the reactor vessel (110, 120), a solution supply mechanism for delivering the hydride solution to the reaction chamber (119, 124), and a coolant supply mechanism for delivering a coolant flow to the coolant chamber (121, 126). The coolant supply mechanism controls the flow rate and/or the temperature of the coolant flow through the coolant chamber, thus improving control of the temperature of the hydride solution in the reaction chamber.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of a reactor vessel.    Reactor vessel (110, 120)    First reactor plate face (115)    Second face (117)    Reaction chamber (119, 124)    Coolant chamber (121, 126)    Reactor plate (200, 200a)    Coolant channels (245)