Construction started on January 1, 1960. The CVTR was built to test the concept of a heavy water moderated and cooled pressurized tube reactor for civilian power. It was the first US heavy water power reactor. It was operated by the Carolinas Virginia Nuclear Power Associates, which was a consortium of the following utilities: Carolina Power & Light Company, Duke Power Company, South Carolina Electric & Gas Company (SCE&G), and Virginia Electric and Power Company
Design of the CVTR began around 1955. CVTR had a thermal output of about 65 MWth and a gross electrical output of 19 MW. Westinghouse Atomic Power Division was responsible for the design of the nuclear systems while Stone and Webster Engineering designed the remainder of the plant.
The reactor consisted of 36 vertical U-tube fuel channels in a moderator tank which was 10 feet in diameter and 16 feet tall. Each leg of the U-tube contained one fuel assembly made up of 19 fuel rods. The reactor used enriched uranium; 12 of the tubes contained fuel enriched to 1.5% U-235 and 24 tubes contained fuel enriched to 2% U-235.
During power operation, heavy water was circulated by primary pumps through the U-tubes containing the fuel assemblies which heated the water. The heated water then flowed through an inverted U-tube steam generator where the heat was transferred to the secondary side light water which turned to steam. The steam flowed to an oil-fired superheater which increased the steam quality before the steam entered the turbine which spun the electrical generator. After passing through the steam generator, the primary loop water was pumped back to the reactor by the primary pumps to repeat the cycle. The primary loop heavy water was pressurized to ensure that the heavy water remained liquid and did not flash to steam at any point in the loop.
The U-shaped pressure tubes containing the fuel were thermally isolated from the hot fuel assembly by two circular thermal baffle tubes around the fuel assembly. This allowed the pressure tubes to operate at low temperatures, essentially that of the moderator tank which was maintained about 155 degrees F and close to atmospheric pressure. The moderator tank contained heavy water which moderated the fission process during operation of the reactor.