Equilibrium cycle analysis of a gas cooled fast reactor with the EQL3D procedure

Advanced fast reactors of the fourth generation should be capable to breed their own fuel from 238U feed and to recycle the actinides from their own spent fuel. This recycling or virtually the closure of fuel cycle converges to equilibrium fuel cycle and has impact on the safety. The goals of this study are i) to apply an equilibrium cycle procedure EQL3D to the Gas cooled Fast Reactor - GFR, ii) to simulate and confirm the GFR capability for closed fuel cycle, and iii) to evaluate the safety parameters of the equilibrium cycle. Equilibrium cycle method for considering the homogeneous recycling of actinides is a known approach. However, in EQL3D the equilibrium method is newly applied for hexagonal-z 3D core geometry and 33 energy-groups neutron-flux calculation. This geometry enables to characterise the equilibrium cycle for complex reloading patterns within a multi-batch cycle. Three reloading patterns within a three-batch cycle with four different feeds were compared for given GFR core geometry. The GFR capability for closed cycle was partially proved. Nevertheless, negative impact of the closed cycle on reactor safety was confirmed and quantified. The GFR core with closed cycle could serve after prospective optimization as a sustainable and clean energy source. (authors)