The decommissioned Boiling Nuclear Superheater
(BONUS) reactor, located northwest of Rincón, Puerto
Rico, was developed as a prototype nuclear power
plant to investigate the technical and economic feasibility
of the integral boiling-superheating concept. This
small-scale nuclear reactor produced saturated steam
in the central portion of the reactor core, superheated it
in four surrounding “superheater” sections of the same
core, and then used the superheated steam in a direct
loop to drive a turbine generator.
It was one of only two boiling-water superheater
reactors ever developed in the United States. The
reactor was designed to be large enough to evaluate
the major features of the integral boiling-superheating
concept realistically without the high construction and
operating costs associated with a large plant.
Construction of the began in 1960 through a
combined effort of the U.S. Atomic Energy Commission
and Puerto Rico Water Resources Authority.