The amount or extent of expositions as a result of hot smelt from a pulp mill recovery boiler impacting cool liquid in a dissolving tank is reduced more effectively by regulating the smelt flow via a restrictor assembly. The restrictor assembly may be positioned to permit the smelt to flow, unrestricted, from the recovery boiler to the dissolving tank, or the restrictor assembly may be positioned so as to fully or partially block the smelt flow from the boiler to the dissolving tank. In some embodiments, a source of cooling fluid may be coupled to the restrictor assembly so as to assist in cooling parts of the restrictor assembly when hot smelt is in contact with the assembly.