Neutronics and Transient Analysis of a Small Fast Reactor Cooled with Natural Circulation of Lead ELECTRA: European Lead Cooled Training Reactor

Sammanfattning: In this thesis, neutronics and some relevant transient analyses of the European Lead-Cooled Training Reactor (ELECTRA) are analyzed. ELECTRA is a low-power lead-cooled fast reactor intended for training purpose. The design concept aims for the total nominal power of 0.5 MWth to be fully removed by natural circulation of pure lead, eliminating the need for pumps. A very small compact core with (Pu0.4Zr0.6)N fuel, which relies on neutron reflector to achieve criticality, results in unique reflector dominant neutronic characters. Moreover, a very hard neutron spectrum due to the choice of the fuel and the coolant leads to nearly zero Doppler feedback, relatively small effective delayed neutron fraction as well as short prompt neutron reproduction time. Nevertheless, dynamic stability and safety performance during unprotected transient scenarios are shown to be inherently ensured by the other reactivity feedbacks including the negative coolant temperature. Furthermore, the nature of the natural circulation provides favorable conditions during the studied accident cases.