Submersion criticality safety of fast spectrum space reactors: Potential spectral shift absorbers

Temperature and burnup reactivities and operational lifetime for the submersion-subcritical, safe space (S∧4) reactor

“…In Case D in Table 1, 8.0 at.% europium-151 is added to the uranium nitride fuel, 2.0 mm pins of europium-151 sesquioxide are inserted in the interstices of the Mo-14%Re core block, and a 0.1 mm thick coating of europium-151 sesquioxide is applied to the outside surface of the reactor core. With europium-151, a particularly effective SSA (King and El-Genk, 2006a), Case D is the smallest and lightest S ∧ 4 reactor in the current analysis. Case E in Table 1 is that of the S ∧ 4 reactor with the highest fuel enrichment (94%) and 12.5 at.% gadolinium-155 in the uranium nitride fuel.…”

“…Iridium, is a more effective SSA than rhenium that can be placed directly in contract with the uranium nitride reactor fuel. Boron-10 is the most effective core coating SSA material (King and El-Genk, 2006a). In Case D in Table 1, 8.0 at.% europium-151 is added to the uranium nitride fuel, 2.0 mm pins of europium-151 sesquioxide are inserted in the interstices of the Mo-14%Re core block, and a 0.1 mm thick coating of europium-151 sesquioxide is applied to the outside surface of the reactor core.…”

Neutronic effects of rhenium, gadolinia and uranium dioxide addition to a tungsten based fast spectrum space reactor

“…All reactor geometries in this study were analyzed using the MCNP5 V1.40 Monte Carlo code operating in the kcode mode (King and El-Genk, 2005). The Monte Carlo method is a direct simulation of particle transport through a reactor geometry where a user specifies one or multiple start points for fission neutrons within the geometry.…”

“…This study uses the MCNP5 version 1.40 Monte Carlo computer code (King and El-Genk, 2005) with the ENDF/B-VII cross section database to investigate the neutronic effects of varying species loading on a pre-conceptual space reactor design.…”