Power uprates in nuclear power generating stations

Since 1970, the electric utilities have been using power uprates to increase the power output of their nuclear power plants as a cost-effective method of adding generating capacity. The cost of the modifications for power uprates is less than constructing new fossil plants. National Electric Institute (NEI) said that the power uprates were equivalent to adding a large power plant to the electrical grid, at a fraction of the cost of building a new reactor. The President's speech in February 2003, noted that the nation's 103 nuclear power plants are by far the largest electricity source that does not pollute the air. From 1977 to May 2003, the US Nuclear Regulatory Commission (NRC) has approved 101 power uprates, resulting in an increase of approximately 12448 MWt or 4149 MWe. The three types of power uprates are measurement uncertainty recapture power uprate (up to 2%); stretch power uprate (2-7%) and extended power uprate (7-20%). For each power uprate, with the production of additional MWe by the generator, there is depletion of MVAR. This means that by improving the power factor MWe production is increased but the production of MVAR is reduced which is a concern with the power uprates. To compensate for the depletion of MVAR with the power uprates, the licensees can install the capacitor banks; increase the generator's MVA either by raising the hydrogen pressure or by rewiring the stator winding and upgrading stator cooling system; install advanced excitation control system; install power system stabilizer or control of MVAR by the Independent System Operator/Regional Transmission Organization. This paper discusses the theory, importance of power uprate and methods of achieving it.