Analysis of Power Uprate in Nuclear Power Plants

The three main strategies used by the utilities in order to obtain more benefits from the nuclear installations focused on electricity production and in order to satisfy their demand without carbon dioxide emissions are: (1) Power uprate, (2) plant life management and (3) plant life extension. Alone in the United States, the Nuclear Regulatory Commission has approved more than 140 Nuclear Power Plant (NPP) power uprates since 1977, which represent the equivalent of five new Nuclear Power Plants (NPPs). While in the rest of the world the NPP uprates represent the equivalent of two new NPP. This study is a compilation of the power uprate experience in the whole world and a discussion about important problems detected due to this process in Light Water Reactors (LWR), specifically for Boiling Water Reactors (BWR). The power uprate involves the reanalysis of many topics in order to assure that the safety operational margins are kept. The new radiological consequences, structural integrity of the systems, vibrations, core heat balance and thermal-hydraulics behavior under transient and accident conditions, are some of the aspects to be considered during power uprate processes. As special case the Laguna Verde Power Nuclear Power Plant (LVNPP) Extended Power Uprate (EPU) is presented, whose experience indicated that the steam dryer loads are crucial for uprates in BWR´s.