Potential of 231Pa for gas cooled long-life core

Feasibility study of the long-life core loaded With Pa-231, Which has very large capture cross-section, has been performed in the pebble bed-type gas cooled reactor. The results of infinite cell burn-up calculations show that Pa-231 has attractive potential to reduce the initial excess-reactivity and to be effectively converted to fissile nuclides U-232 and successively U-233 with the burn-up. These characteristics enable the reactor to sustain nuclear reactions for a longer time. Based on the optimization of the fuel composition and the moderator to fuel ratio, it is found that the high fuel burn-up of about 700 GWd/t is achievable in consideration of the material restriction of coated fuel particles, Safety studies show negative temperature coefficients during the irradiation.