This paper introduces a conceptual design of the Scalable Liquid Metal cooled small Modular (SLIMM) reactor developed at the University of New Mexico to generate 100 or 20 MWth for more than 5 or 26 years, respectively, without refueling. In-vessel natural circulation of liquid sodium cools the reactor core during nominal operation and after shutdown. The reactor has a negative temperature reactivity feedback, a fast neuron spectrum, redundant control and safety shutdown systems, and in-vessel helically coiled tubes heat exchanger. Fabricated, assembled and sealed at the factory, the SLIMM reactor ships to site by rail, barge or heavy trucks. It would be installed below ground and mounted onto seismic insulators. In addition to electricity generation, SLIMM reactor plant could provide process heat for industrial uses, district heating and/or seawater desalination, achieving total energy utilization in excess of 60%. Variable conductance liquid-metal (LM) and water heat pipes help cool the reactor's primary and guard vessels, respectively, during nominal operation and after shutdown. LM heat pipes transport thermal energy to thermoelectric modules that generate auxiliary electrical power for the plant's vital functions both during nominal operation and in the unlikely event of a total loss of onsite and offsite power. Natural circulation of atmospheric air cools the reactor guard vessel and passively removes decay heat following reactor shutdown due to a malfunction of the in-vessel heat exchanger.