Dear Editor:

I am an employee at a nuclear power plant. One of my jobs involves reporting generation data to the NRC. In the 2006 Operating Performance Rankings (EL&P, Nov. Dec. 2007), you noted that to be in the top 20 nuclear plants for generation, a plant must have 2,000 MW of capacity and multiple units. However, to be in the top 20 for capacity factor, the playing field is somewhat leveled. What capacity factor are you using? Is it Maximum Dependable Capacity or Design Electrical Rate as defined by the NRC or are you using some other calculation?

Skip Olsen
Constellation Energy


Tom Hewson, principal, Energy Ventures Analysis, and analyst on Performance Rankings report:

The EIA 906 data submitted by the operating companies for net power output and net capacity are used to develop the report’s nuclear plant rankings. These data were downloaded directly from DOE. In developing the 2006 rankings, we combined the monthly data reported separately for Units 1 and 2. These data showed the Calvert Cliffs station having a combined 2006 net generation of 13,830,411 MWh and a net demonstrated capacity (average of summer and winter) of 1,703 MW, giving an average station capacity factor of 92.74 percent. This performance places the station ranking at #26 for generation and #31 for capacity factor.

Had we not combined the multiple units by station, we would have had 104 reporting nuclear units and your unit #2 would have ranked as #21 in capacity factor using the reported average net generating capacities. (Several units have calculated capacity factors >100 percent, suggesting that many may not have updated their rated capacities or use permitted output capacities.) The individual components for the Calvert Cliffs station by unit contained in this DOE 906 database are as follows:

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Skip Olsen: Thanks, Tom, now I know where you are getting your generation. It seems like everyone uses a different reference point. Your generation values are not what is reported to the NRC, but what is used for DOE. This accounts for the difference in what you state we produced and what I have.

The DOE uses negative generation. If a unit is not producing power but continues to use power it results in negative generation, which for DOE and financial reasons is important. The NRC is concerned with power generation only. This makes sense from the view of reactor fuel usage and core life. Negative generation gives the appearance, math-wise, that you are putting fuel back in the reactor: produce 100 MW output, used 30 MW while shut down = net generation of 70 MW. However, for NRC, you produced 100 MW and had 0 generation while shut down, not -30 MW. It’s all a matter of reference.

CCNPP-1 did have a capacity factor (mdc) of >100% in 2005. We had a great 365 days with 1 minor outage (in hours not days).

My only negative feeling about your methodology is that you combine a site’s generation and average it out. We will probably never be in your ranking since we have a unit down each year for refueling, but at least now I know why we aren’t there!

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