Abstract
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.
Highlights
The generation of electricity without carbon dioxide emission is one of main strategies against climate change, but the demand of electricity is increasing dramatically, in particular if we considered that the world population is increasing about 10% each ten years
The power uprate involve some problems associated with the increase of steam and feedwater flow, for instance the occupational doses is impacted, in particular in Boiling Water Reactors (BWRs) where occupational exposure is about 50% higher than a Pressurized Water Reactors (PWRs)
The higher contribution about 47.3% is from the extended power uprate and the lower one is from the measure uncertainty recapture power uprate. The result of these power uprates is a gain of approximately 20,492.2 MWt (Megawatts thermal) or 6,823.7 MWe (Megawatts electric) at existing plants and if we considered the applications under review the gain is 23,586.8 MWt or 7,863.2 MWe (Table 2)
Summary
The generation of electricity without carbon dioxide emission is one of main strategies against climate change, but the demand of electricity is increasing dramatically, in particular if we considered that the world population is increasing about 10% each ten years. There are many aspects to be considered in this kind of project in order to assure the safe operational of the nuclear installations and these are highly dependent of the regulation in each country (Lundgren and Riess, 2007) Both deterministic and probabilistic safety analyses are used to evaluate the impact of significant plant modifications such as power uprate. This provides a dampening effect on the acoustic energy input into the system Before replacing their steam dryers and installing ASB, Quad Cities Units 1 and 2 experienced repeated structural damage to their steam dryers and steam line components as a result of Extended Power Uprate (EPU) operation.
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