System 80
System 80 is a Generation II pressurized water reactor (PWR) nuclear power plant design developed by Combustion Engineering (CE), featuring a two-loop primary coolant system with vertical U-tube steam generators and a nominal thermal power output of 3,817 MWth per unit, yielding approximately 1,350 MWe electrical output.[1][2] Three System 80 reactors were constructed and remain operational at the Palo Verde Nuclear Generating Station near Tonopah, Arizona, forming the largest nuclear power facility in the United States by total capacity, with a combined net output exceeding 4,000 MWe.[3] The design emphasizes standardized components for improved constructability and safety, including enhanced emergency core cooling systems and containment structures capable of withstanding severe accidents.[4] Introduced in the 1970s as an evolution of earlier CE PWRs, System 80 incorporated empirical lessons from operational data to optimize reliability and efficiency, achieving high capacity factors at Palo Verde averaging over 90% in recent years.[5][6] It served as the foundation for the System 80+ advanced PWR variant, which introduced further improvements such as quadrupled emergency AC power capacity, digital instrumentation and control systems, and in-containment refueling water storage for severe accident mitigation, earning U.S. Nuclear Regulatory Commission design certification in 1997.[7][8] While no System 80+ units were ultimately built in the United States due to market conditions in the 1990s, the original System 80 design has demonstrated long-term operational stability without design-related incidents compromising public safety, contributing substantially to low-carbon electricity generation.[9][10]Design and Technology
Core Specifications
The System 80 pressurized water reactor (PWR) core operates at a nominal thermal power of 3800 MWt, delivering approximately 1300 MWe net electrical output per unit under design conditions.[11] This power level supports a four-loop primary coolant configuration, with light water serving as both moderator and coolant to maintain subcooled conditions and prevent boiling within the core.[12] The core houses 241 fuel assemblies arranged in a cylindrical lattice, optimized for uniform power distribution and efficient neutron economy.[13] Each assembly employs a 16×16 array of fuel rods, containing stacked uranium dioxide (UO₂) pellets enriched up to about 4-5 weight percent uranium-235, encased in Zircaloy-4 cladding for corrosion resistance and structural integrity.[14] Guide tubes within select assemblies accommodate control element assemblies (CEAs), which deploy boron carbide (B₄C) or similar absorbers for reactivity control, supplemented by soluble boron in the coolant for fine-tuning and shutdown margin.[15] Key geometric parameters include an active core height of 3.658 meters and an equivalent core diameter of 2.921 meters, yielding a height-to-diameter ratio conducive to axial power shaping and thermal-hydraulic stability.[16] These dimensions fit within a reactor vessel of approximately 12 meters in height and 4 meters in inner diameter, fabricated from low-alloy steel to withstand pressures up to 17.24 MPa (2500 psia).[17] The design emphasizes high burnup potential, with fuel residence times supporting 18-24 month cycles, while incorporating neutron reflectors to enhance fuel utilization and reduce peripheral power peaking.[12]| Parameter | Specification |
|---|---|
| Thermal power | 3800 MWt |
| Number of fuel assemblies | 241 |
| Fuel rod array | 16 × 16 |
| Active core height | 3.658 m |
| Equivalent core diameter | 2.921 m |
| Coolant inlet temperature | ~290°C |
| Coolant outlet temperature | ~325°C |