CANDU-6 Operation Simulations Using Accident Tolerant Cladding Candidates

The 3D DRAGON-DONJON capabilities are exploited to simulate CANDU-6 (Canada Deuterium Uranium) core follow-up with alternate cladding materials. Aluminium-based alloys (FeCrAl and APMT), nickel based alloys (304SS and 310SS) and silicon carbide (SiC) are compared with Zircaloy-II. High thermal captures in aluminium and nickel-based systems imply U-235 enrichment, which results in a lower breeding ratio and a 1.1 ppm to a 1.4 ppm higher boron concentration than the current CANDU-6 reactor. Natural enrichment is preserved for SiC system, while providing a 3.4 mk increase in core reactivity with boron poisoning conditions similar to the reference CANDU bundle. The enriched systems' spectral hardenings result in a 246 kW lower channel power. Throughout the cycle, the new ATF operation compliances are compared to the CANDU-6 license limits. The liquid zone controllers and adjusters effects on power flattening are investigated. An 8-bundle shift on power refueling scheme based on the CANDU channel age model is implemented and tested. The cores' dynamic responses to a loss of regulation control event and to an instantaneous or gradual recovery of reactivity regulation devices are also studied. By uniformly perturbing the core global and bundle local parameters, new reactivity coefficients are determined and cores' responses are compared over a large spectrum of moderate and severe accident scenarios. (C) 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).