Statistical Modeling for Reactor Thermal Power Optimization in Bruce Power Reactors
9th International Conference on CANDU® Maintenance - 2011 December 04-06


Presented at:
9th International Conference on CANDU® Maintenance
2011 December 04-06
Location:
Toronto, Canada
Session Title:
Fitness for Service Session C3

Authors:
Vinod Chugh (AMEC NSS)
Ovidiu Nainer (Bruce Power)
Paul Sermer (AMEC NSS)
Jun Stoklosa (Bruce Power)
Keith Weaver (AMEC NSS)
David Zobin (AMEC NSS)
  

Abstract

An accurate and reliable calculation of reactor thermal power is essential both to make sure that the reactor stays within the limits of the safety analyses, and that the thermal power stated in the license is not exceeded.  Uncertainty margins achieved at many plants around the world is as low as 0.5%FP, resulting in Measurement Uncertainty Recapture Uprates (MUR) of up to 1.5%FP.

However, for historical reasons, the uncertainty margin currently applied to CANDU plants is about 3%FP, and the reactor thermal power specified in the Power Reactor Operating License is equal to the design value, which is lower than the value in the Safety Analysis by the uncertainty margin. In order to recover some of the margin, a modified compliance approach is being proposed. Implementation of this approach will not only lead to more consistent compliance practices but will also allow increase in reactor power operating levels and result in increased revenue. A 0.5% power increase results in about $1.5M in additional annual revenue per unit, assuming 5 C/kWh and 90% capacity factor.

The compliance approach being developed is based on the application of a statistical model for the reactor thermal power to the data for Bruce Power units collected over a 5-year period, from 2006 until 2010. The model has been applied to the indicated power, heat balance and SORO data for Units 5 and 8, and model equations have been solved using Maximum Likelihood Estimation. Preliminary results indicate that when the set point is at 93%FP, with 95% confidence, the true reactor power is below 94.5%, or 1.5% less than the safety limit over the entire period of time. The approach is currently being developed for Bruce Power Units 6 and 7, as well proposed for  the other Ontario CANDU stations.

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