A system and method for quickly cooling and de-pressurizing a boiler arrangement in the event of a plant power loss, a.k.a. a black plant condition. A steam discharge system injects steam from the steam/water circuit into the furnace, thereby both cooling components of the boiler arrangement and reducing pressure in the steam/water circuit. This reduces or eliminates the additional cost associated with providing extra capacity in a steam drum and/or an independently powered boiler water pump. The system and method is particularly useful for quickly cooling the U-beams of a circulating fluidized bed (CFB) boiler during a black plant condition. In application to boiler arrangements with a selective non-catalytic reduction (SNCR) system employing steam as a carrier for a NOx reducing agent, the steam discharge system advantageously uses the discharge nozzles of the SNCR system to inject the steam into the furnace.