Fission heated subassembly for sodium boiling experiments in EBR-II

Localized coolant boiling in a liquid metal fast breeder reactor (LMFBR) may be the first indication of a partial coolant blockage in a subassembly. The potential for such an incident to develop into an accident disrupting the reactor core attracts the development of an instrumentation system capable of detecting local coolant boiling. A requisite for the development of such a system is a thorough understanding of the characteristics of the boiling and the signals (neutronic and acoustic) generated. This knowledge may best be obtained by conducting prototypical in-reactor experiments in which local coolant boiling is generated downstream of a simulated blockage. A conceptual design of a 37 pin, fission-heated subassembly containing a central blockage is presented. The subassembly is designed to operate in Experimental Breeder Reactor II (EBR-II).