Small Modular Reactor - STAR system's heat transfer design allows use of sealed "nuclear battery"

The single most unique feature of this concept is that the fission-generated heat is transferred from the primary coolant to the secondary coolant through the reactor vessel wall, completely eliminating through-vessel fluid or mechanical connections. This enables the reactor to remain sealed throughout its lifetime. The reactor module and the steam generator modules can be easily installed and replaced. The reactor core is designed to have long life without refueling operations. We shall refer to the combination of a reactor module that is not mechanically connected to other components of the power plant and of a long-life core as the Encapsulated Nuclear Heat Source (ENHS) or as a "nuclear battery". The ENHS opens new possibilities for the design, fabrication, construction, operation, maintenance and refueling of nuclear power plants. For example, the vendor manufactures and charges the nuclear battery in the factory, installs it in the "field," uses it as long as it can deliver the required power, and replaces it thereafter with another factory-manufactured nuclear battery.

[Source: DOE Nuclear Energy Research Initiative (NERI) Project Abstract, "STAR: The Secure Transportable Autonomous Reactor System, Encapsulated Fission Heat-Source", November 22, 1999]