A system and method for regulating steam pressure. The system includes a steam source, a reformer, and a pressure regulator. The reformer includes an inlet that is in fluid communication with a steam source, and an outlet that provides a supply of hydrogen gas. The pressure regulator includes a valve body, a valve movable between first and second positions, and an actuator. The valve body defines an internal flow passage between first and second ports. The first port is in fluid communication with the inlet of the reformer. The first position of the valve substantially prevents steam communication through the internal flow passage, and the second position of the valve permits generally unrestricted steam communication through the internal flow passage. The actuator includes an actuator body that defines a chamber, a movable actuator wall that divides the chamber into first and second chamber spaces, and a shaft that couples the movable actuator wall to the valve.