The Encapsulated Nuclear Heat Source (ENHS) is a Generation IV liquid metal-cooled Small Modular Reactor (SMR) concept. The power output is designed as a 50 MWe (electrical) / 125 MWth (thermal) fast neutron reactor and its primary coolant is Lead (Pb) or Lead-Bismuth Eutectic (Pb-Bi). Lead provides a very high boiling point and is chemically inert with air and water, drastically lowering the risk of high-pressure explosions.