PRD (power-reactivity-decrement) components of a homogeneous U10Zr-fueled 900 MWt LMR

The linear and Doppler feedback components of the regional contributions of the power-reactivity-decrement (PRD) for a representative 900 MWt homogeneous U10Zr-fueled sodium-cooled reactor are calculated. The PRD is the reactivity required to bring the reactor from zero-power hot-critical condition to a given power level. These components are further separated into power dependent and power-to-flow dependent parts. The values are compared with corresponding quantities calculated for the Experimental Breeder Reactor II (EBR-II). The implications of these comparisons upon inherent safety characteristics of metal-fueled sodium-cooled reactors are discussed. The effects of fuel axial restraint on feedback, resulting from possible fuel-clad interactions due to burnup are also calculated. The possible enhancement of desirable feedbacks by use of appropriately designed subassembly-duct bowing feedback characteristics is estimated.