Core concept study on plutonium burning fast reactor (II)

Yamaoka, Mitsuaki*; not registered; Kawashima, Masatoshi*; Fujita, Reiko*

To enhance plutonium burning capability in fast reactors, one of the effective means is to use materials other than uranium for dilution of plutonium. A feasibility study was made to build a 600MWe-class core concept within the do-main of sodium-cooled fast reactors. The analysis covered core static and transient characteristics, including fuel material surveys. The candidate fuels were chosen as plutonium oxide with diluen materials, such as AlO and BeO, to keep the Doppler coefficients negative large enough, condisering the TOP-type transisnts results from the FY1993 study. Core nuclear analysis showed that use of fuel without uranium considerably increases burnup swing and power mismatch between fresh and burnt fuels, aiming at the long cycle length as the 600MWe MOX core design. The core characteristics under ULOF- and UTOP-transients were compared with those in the 600MWe-MOX core. The study showed that the 9-month cycle core burned 59% fissile plutonium with negative sodium void worth (-1 $) under the plant condition for sodium inlet 390 C-deg. and the outlet temperature 510 C-deg. This study revealed that core neutronic feasibility has shown for such an innovative core concept with selecting appropriate diluent fuel materials combining core specifications. This means that sodium-cooled fast reactor has additional larger flexibility associated with plutonium utilization in the future.