Reactor physics code suite validation using station start-up data: an assessment of feasibility

The feasibility of using Canada Deuterium Uranium (CANDU) station warm-up measurements to validate Reactor Physics Industry Standard Toolset (RP-IST) predictions of combined coolant temperature, coolant density and fuel temperature induced reactivity effects was examined. The combined induced reactivity changes were quantified for several critical state transitions experienced during Heat Transport System (HTS) warm-up events at the Darlington Nuclear Generating Station (DNGS) in Ontario, Canada. The magnitude of reactivity insertion due to increased coolant temperature (and hence increased fuel temperature and decreased coolant density) was quantified by measuring the amount by which the liquid zone control system reactivity was altered by the Reactor Regulating System (RRS) to maintain criticality. The events were then simulated with the RP-IST code suite and the predictions compared with the measurements. The results revealed a random prediction uncertainty of approximately ± 7%; consistent with the results of similar independent validation exercises carried out in the ZED-2 experimental reactor at Atomic Energy of Canada Ltd (AECL). The results of this work therefore support the scalability of ZED-2 measurements to CANDU reactors and the feasibility of using station warm-up data in code suite validation exercises. (author)