Advanced CANDU Reactor Research Articles

Natural-convection studies for advanced CANDU reactor concepts

AECL is studying advanced reactor designs where natural convection is an important design feature in heat removal processes. The use of a flashing-driven, natural-circulation system to remove moderator heat is being considered. Experiments and code simulations have shown that a flashing-driven system is feasible at normal operating power, but is prone to flow instabilities at low powers. Vapor flashing at superheated conditions and the presence of nucleation sites were found to be important for stable operation over the whole power range. A development concept for CANDU® is to increase the primary coolant pressure and temperature to supercritical conditions. With a natural-convection-driven primary flow, the large variations in fluid properties near the critical point introduce the potential for flow instabilities. Analyses have shown that flow instabilities can occur under certain conditions. Experimental and analytical results on the flashing system are described. The experiments and initial analytical results for the supercritical concept are discussed.

Investigation of the Neutronic Potential of Moderated and Fast (D,T) Hybrid Blankets for Rejuvenation of CANDU Spent Fuel

AbstractThe potential of moderated and fast hybrid blankets is investigated for the rejuvenation of CANDU spent fuel. The moderated hybrid blanket has revealed poor neutronic performance and is not suitable for CANDU spent-fuel rejuvenation. The fast-fissioning hybrid blanket has excellent neutronic performance and is investigated to achieve different enrichment grades of fissile isotopes (EGFI) for three different applications:1. recycling in a conventional commercial CANDU reactor (EGFI = 0.71 to 0.9%)2. recycling in an advanced CANDU reactor concept with high burnup rate (EGFI = 1%)3. recycling in an advanced breeder with thorium fuel (EGFI > 1.5%)For fast-fissioning blankets, a rejuvenation period of up to 24 months is investigated by a plant factor of 75% under a first-wall (deuterium, tritium) fusion neutron current load of 1014 to 14 MeV·n/cm2·s, corresponding to 2.25 MW/m2.Rejuvenation periods of 6 to 12 months, 10 to 16 months, and 18 months, respectively, are evaluated for the above-mentioned re...

Creep and stress-rupture of high strength zirconium alloys

Zirconium-based alloys with small additions of tin, molybdenum, niobium and aluminum are being developed as candidate materials for high-strength pressure tubes in advanced CANDU reactors. The out-reactor creep and stress-rupture properties of 12 alloys based on these elements have been determined and correlated with their metallographic structures and substructures and thermomechanical histories. An alloy of composition Zr-3 wt% Sn-1 wt% Mo-1 wt% Nb was the best for high creep strength, low neutron capture cross section and reasonable corrosion resistance. Résumé Des alliages à base de zirconium et con tenant de faibles additions d'étain, de molybdéne, de niobium et d'aluminium sont en voie de développement comme matériaux à haute résistance pour des tubes de force pour le réacteur CANDU. Les propriétés de 12 de ces alliages ont été évaluées hors réacteur quant au fluage et à la rupture; des corrélations ont été établies entre ces propriétés et la structure métallographique, et les traitements thermomécaniques subis. Le meilleur alliage pour sa résistance au fluage, sa faible section de caputre des neutrons et sa résistance à la corrosion, a une composition de: Zr-3% Sn-1% Nb (% pondéral).