The AP1000 Is NRC-Certified
Although no new nuclear plants have been ordered in the U.S. in 30 years, the major designers and manufacturers of these plants have continued to improve and refine designs, building several evolutions of successful designs in foreign countries. Westinghouse submitted the Standard Design Certification Application for its AP1000 reactor design on March 28, 2002. The NRC issued a final rule in the Federal Register certifying the Generation III+ design on January 27, 2006, and it remains the only Generation III+ reactor certified to date. Additionally, the European Utility Requirements organization certified that the AP1000 can be deployed in Europe. China is currently building multiple AP1000 reactors; its first unit is scheduled to be online by 2013.
The AP1000 has been designed to make use of modern, modular construction techniques (Figure 5). The design incorporates vendor-designed skids, equipment packages, and large multi-ton structural modules, as shown in Table 2. Welding and fabrication activities are performed in a factory environment, which improves working conditions and scheduling flexibility while reducing the special tools and equipment needed on-site. Furthermore, modularization allows construction tasks that were traditionally performed in sequence to be completed in parallel, thus reducing capital costs and shortening construction schedules to approximately 36 months from the pouring of first concrete to the loading of fuel.
5. Inherently safe design. The inherent passive safety of the AP1000 derives from its modular construction design, which has fewer pumps and valves than the typical plant operating in the U.S. today. This increases reliability and reduces maintenance and operating costs. Source: Westinghouse
Principal Building Structures
The AP1000 plant is arranged with five principal structures — nuclear island, turbine building, annex building, diesel generator building, and radwaste building — each on its own base mat (Figure 6).
6. Reduced construction required. The AP1000 plant arrangement consists of five principal building structures: the nuclear island, the turbine building, the annex building, the diesel generator building, and the radwaste building. Source: Westinghouse
The nuclear island consists of a free-standing steel containment building, a concrete shield building, and an auxiliary building. These are the only Seismic Category I structures required with the AP1000 design. The foundation for the nuclear island is an integral base mat that supports these buildings.
The safety-related equipment designed to perform accident mitigation functions is located on the nuclear island. Therefore, the nuclear island structures are designed to withstand the effects of natural phenomena such as hurricanes, floods, tornados, tsunamis, and earthquakes, as well as the effects of postulated internal events such as fires and flooding, without loss of capability to perform safety functions.
To preclude adverse interactions, the plant arrangement provides for separation between safety-related and non-safety-related systems and equipment. This separation is provided by partitioning an area with concrete walls and provides confidence that the safety design functions can be performed. The remaining nonseismic structures do not contain any safety-related equipment.
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