The Tennessee Valley Authority on Dec. 13 secured the reactor vessel head after loading 193 nuclear fuel assemblies into the 1,150-MW newly built unit at Watts Bar nuclear generating station in Spring City, Tenn. TVA will perform a series of low-power tests to determine if the unit operates as designed, says a spokesman. It is set for commercial operation next June. Watts Bar-2 received an operating license from the U.S. Nuclear Regulatory Commission in October and will become the first U.S. power reactor to begin commercial operation in two decades. The license follows three years of construction to complete the boiling-water reactor on which work had stopped in 1985, at 80% complete. The project cost doubled to more than $4 billion.