The US government on Friday approved the Watts Bar nuclear power plant to commence operations at the Tennessee Valley Authority (TVA) – after 19 years of efforts and an investment of $4.5 billion.

The operating license for Unit 2 of TVA was granted for the Gen II plant to start producing power before the end of this year; but then, the US stopped constructing Gen II nuclear reactors in the early 1990s.

The TVA started constructing two pressurized water reactors (PWRs) in 1973. Unit 1 was completed in 1996 and construction that was ongoing on Unit 2 was stopped in 1998 when it was 80% near completion due to information that demands for the power was on the decline.

Constructions started again on Unit 2 in 2007, and with the latest approval given to it, nuclear fuel can be loaded into it and testing can begin as soon as possible. The ultimate aim of the TVA is to generate 1,180 megawatts of power through it before the end of 2015.

The Unit 1 is already operational, even though it is also a Gen II four-loop pressurized water reactor just like the Unit 2, both were built by Westinghouse. Gen II reactors are different from modern Gen III reactors because the latter provides better safety, increased efficiency, and its design is much simpler and reliable.

Must Read: Fed approves Watts Bar nuclear plant in Tennessee after 20 years & $4.5 bn investment

“For example, four reactors based on the more modern Gen III design, known as AP1000, are currently being built in the U.S. Compared to a Westinghouse Gen II PWR, the AP1000 contains 50 percent fewer safety-related valves, 35 percent fewer pumps, 80 percent less safety-related piping, 85 percent less control cabling, and 45 percent less seismic building volume,” said the TVA.

Considering the advanced safety features of the newer generation reactor, its AP1000 reactors should be about 100 times as safe as existing plants. In the case of any accident, the AP1000 will shut itself down within 72 hours without electric power or any human operations. And a small amount of water is needed to keep the reactor stable after the machine shuts down.