Fort Calhoun Station is currently experiencing 3-5 MWth swings (peak-to-peak) in a one hour period to on our secondary calorimetric calculation. This last outage we replaced both S/Gs and refurbished our FW regulation valves.  Prior to this outage our swings were normally 1 MW over 4 hour period. We attempt to keep power at a corporate goal of 1498 MWth (1500 MWth is our rated power level). We do not see these swings on the NI or Delta-T power indications that follow the secondary calorimetric swings.

 

We have not implemented Appendix K using ultrasonic flow measurement for feedwater as of yet.

 

Our Question(s)

 

1) What are other plants goals/expectations for maintaining power level? (=/- MW or goal); How easy is it to maintain?

    Is there a band within which you operate? 

Wolf Creek's rated thermal power is 3565 MW.  Operations is expected to maintain the plant between 3563 and 3565, unless performing an evolution that could result in a positive reactivity addition.  It requires multiple small dilutions (or borations at BOC) during the day to stay in the band.  It is not difficult to maintain.   

2) How is your secondary calculation performed?  (Averaging Inputs, Instantaneous values, combination) Is it a module

    or program on you plant computer or is it an off-line routine? 

The secondary calorimetric is a live calculation performed by the plant computer and is used as the primary indication of reactor power.

The calorimetric currently calculates once per minute and uses 1-minute averages for all inputs.  We tried instantaneous calcs, but this caused power to fluctuate in a sinusoidal pattern (matching the sinusoidal oscillations of FW flow).  1-minute averages sufficiently dampen the FW reg valve oscillations. 

That said, the 1-minute points still have a lot of scatter, so the operators use the 10-minute and 1-hour moving averages to determine whether they are in the operating band.

3) Are your temperature and flow transmitters set specifically for this calculation? (dampening or bias settings) 

We have no special instrument dampening or filtering for calorimetric inputs. 

4) Are any of your control loops (Feedwater) used in the secondary calorimetric calculation? 

We use FW flow (venturi dps), FW temperature, SG Pressure as the main inputs. 

5) Have you had any issues related to power swings or related to your secondary calorimetric? 

Coming out of our last outage (Refuel 15, Fall of 2006) calorimetric power was fluctuating slightly more than in the previous cycle.  We initially suspected issues with the new Feed Reg Valve controllers (upgraded in R15) or issues with Feed reg valve movement.  It turned out to be a result of upper plenum anomaly fluctuations.  These cause fluctuations in Thots, Steam Flow and Feed flow.

This cycle our fluctuations in the 1-minute calorimetric point were about +/- 10 Mw about nominal power at BOC.  Last cycle, they were about +/-6 MW about nominal.