Safety issues nearly killed the nuclear-energy industry, and the industry got the memo. New orders dried up and old ones were canceled after the 1979 near-meltdown at Three Mile Island. The 1986 Chernobyl disaster was the industry’s death-knell for a generation in the West.

New reactor designs, dubbed Generation III and Generation III+, are evolutions of the Gen II reactors built in the 1960s and ’70s, drawing upon the nuclear power industry’s years of operating experience and data. Safety—“passive” safety—is their chief selling point.

Passive systems use natural forces such as gravity for cooling-water flow and convection for air flow, for emergency response instead of active intervention by operators. Westinghouse’s 600-MW Advanced Passive AP600 pressurized-water reactor was the first approved by the Nuclear Regulatory Commission to use such features (see drawing). The AP600 was never built, but Westinghouse built on its concept to develop the AP1000 PWR, a 1,100-MW Gen III+ design now certified by NRC.

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Unlike the last generation of plants, many of which were custom-designed, Gen III reactors use a standard design for their plants. After completing a rigorous public review, NRC is to issue design certification for a standard reactor that can then be replicated on numerous sites with minimal review. Standardization includes generating capacity. AP1000’s nominal capacity is 1,100 MW; GE’s Gen III Advanced Boiling-Water Reactor (ABWR) is 1,350 MW; and its Gen III+ Economic Simplified Boiling-Water Reactor (ESBWR) is 1,500.

Gen III+ reactors have simplified designs, resulting in lower costs, vendors claim. Westinghouse says AP1000 requires 50% less building volume, 50% fewer valves, 80% fewer pipes, 35% fewer large pumps and 70% less control cable than today’s plants.

Modular design is a feature introduced with Gen III. “The construction techniques themselves are simpler,” says Jack Bailey, vice president of nuclear generation development and business support, for the federal Tennessee Valley Authority, Knoxville, Tenn. With modular construction, two 1,350-MW GE ABWRs were built in 39 months in Japan in 1996. Westinghouse claims its AP1000 can be built in three years.

The AP1000 is the first Gen III+ design to win NRC design certification, and about half of the owners proposing to apply for combined construction and operating licenses in the U.S. have selected it. GE is aiming for design certification for its ESBWR by 2009, and it has been selected for three U.S. sites. Areva Inc., Bethesda, Md., is pursuing certification for its Gen III+ PWR, the U.S. Evolutionary Power Reactor. It expects to apply by the end of 2007.