Abstract: The current invention discloses a method and apparatus for production of hot water or steam in a 4-pass firetube boiler. A waste heat stream is passed through the first and second passes of the boiler, and then routed into a furnace tube (which is the third pass of the boiler) to help suppress the flame temperature and NOx emissions from the burner. The flue gas from the third pass is then passed through the fourth pass of the boiler to transfer the heat energy to the water in the boiler.

Abstract: The plugs are used to close the main steam lines of a boiling-water reactor when the reactor is shut down for maintenance, testing and refueling. The plug utilizes an elongated rubber member which is compressed by axial compression in order to form a seal which will hold the plug in place despite the presence in the steam line of substantial isolation valve test pressures which might force the plug out. Preferably, plates covering portions of the rubber are used to provide a long-lasting solid surface to grip the inside wall of the pipe. A device is provided for the remote installation of the plug so as to minimize the exposure of workers to radioactivity in the reactor vessel. The installation device includes remotely controllable structure for compressing the rubber member of the plug. In one embodiment, the compression structure includes a set of impact wrenches for turning a nut on each of several bolts which are used to compress the rubber member of the plug.