Michael E. Mayfield, Director Division of Engineering April 24, 2006

1. Grid Reliability Michael E. Mayfield, Director Division of Engineering April 24, 2006

2. Grid Reliability • Why is a reliable offsite power supply important for nuclear power plants? • Protective devices will sense grid disturbances and, if necessary, isolate the nuclear power plant from the grid • Potential impact on core cooling • Preferred power supply for safety-related components

3. Annual Loss of Offsite Power Frequency(Power Operation) 0.25 0.20 0.15 (per reactor critical year) Occurrence Rate 0.10 0.05 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 0.00 Year Yearly 86-96 Trend 86-96 Upper Bound 86-96 Lower Bound 97-02 Trend 97-02 Upper Bound 97-02 Lower Bound

4. Annual Loss of Offsite Power Duration 1000.00 100.00 10.00 1.00 0.10 0.01 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Calendar Year 5% Lower Bound Trend 1986-96 95% Upper Bound Trend 1997-2003 Observed with Bounds 5% LowerBound 95% Upper Bound Duration (hrs.)

5. New Reactors • Majority of new reactor locations planned for south-eastern U.S. • Industry estimates that construction will be completed between 2015 and 2018 • Industry anticipates the addition of about 20,000 to 25,000 Megawatts of electricity to grid

6. Anticipated New Reactor Locations

7. Summary • Nuclear power plants rely on a reliable offsite power supply • NRC is continuing to: • Monitor grid reliability • Work with Federal Energy Regulatory Commission (FERC) and the North American Electric Reliability Council (NERC) • Work with Licensees