American reactors upping capacity, lengthening life

01 February 2008

Improvements to the US reactor fleet have continued with approvals for power uprates at three nuclear units. Regulators have received a new application for reactor licence extension at a fourth, while another extension review is nearing completion.



The Nuclear Regulatory Commission (NRC) announced its approval of uprates at two boiling water reactors (BWRs) at the Susquehanna nuclear power plant in Pennsylvania that will increase the capacity of each by some 13%. The increase, from 1200 to 1300 MWe at each unit, will be achieved through the upgrading of plant systems and components. Operator PPL intends to complete the work on unit 1 in two stages during refuelling outages in spring 2008 and 2010, while the uprates at unit 2 are scheduled for completion in one step during refuelling in spring 2009.


The NRC has also approved a 1.6% uprate at the Crystal River nuclear power plant in Florida. The uprate, achieved through more accurate measuring of feedwater flow, will raise the capacity of the pressurized water reactor (PWR) from 838 to 850 MWe. Operator Progress Energy Florida intends to implement the uprate by the end of January.


Stretch and extend


The US Nuclear Regulatory Commission recognises three categories of power uprates:

  • 'Measurement uncertainty recapture' power uprates, such as that approved at Crystal River, involve implementing enhanced techniques for calculating reactor power and can typically increase reactor capacity by up to 2%
  • 'Stretch' power uprates, which usually involve changes to instrumentation settings but are within the design capacity of the plant and can typically add up to about 7% capacity 
  • 'Extended' power uprates, such as those approved at Susquehanna, which involve significant modifications to major plant equipment and can result in up to 20% capacity increases.

The Susquehanna decision brings the total number of uprates approved by the NRC since 1977 to 116, representing over 5000 MWe of added capacity.


Licence extensions


The Susquehanna units were connected to the grid in the early 1980s. In 2006, operator PPL submitted an application for a licence renewal for the plant. Since 2000, the Nuclear Regulatory Commission (NRC) has approved licence renewals for 48 nuclear power plants following exhaustive procedures including public meetings and thorough safety reviews. Most of the plants involved started up during the 1970s with 40-year operating licences. The 20-year licence extensions mean that any major refurbishments, such as replacement of steam generators, can be undertaken with confidence.


The NRC has also this week issued its final environmental impact statement on the proposed licence extension for Entergy's James A Fitzpatrick nuclear power plant in New York state, and says there are no environmental impacts that would preclude renewing the plant's licence for another 20 years of operation. The completion of the final environmental impact statement is one of the last hurdles before the NRC's final decision on whether to grant the extension, which is scheduled to be made in May. The BWR's current operating licence is due to expire in 2014.


The NRC is still considering other licence renewal applications. Earlier in January, the operators of Three Mile Island unit 1 formally submitted an application for a 20-year renewal of its operating licence, which currently is set to expire in 2014. Three Mile Island 1 is operated by Exelon subsidiary AmerGen.


According to its web site, NRC anticipates licence renewal applications from a further 5 sites by the end of 2008, with many more to follow – eventually 85 of the US fleet of 103 reactors are expected to apply for licence extensions.