was not assumed for the core in this study, low sodium void reactivity is a
significant factor for sodium-cooled fast reactors.
Furthermore, the developed core design has the potential to achieve passive
safety features against unprotected events such as unprotected loss of flow (ULOF)
and unprotected transient overpower (UTOP) similar to a conventional metallic
fuel core because the basic core safety parameters, that is, average and peak linear
heat rates for lower fuel temperatures, the enhanced Doppler coefficient, and
low sodium void coefficient (negative sodium coefficient in whole core), were
maintained within the similar ranges of a conventional metallic fuel core
design [20].
Fig. 15.6 Fuel subassembly cross section
Table 15.4 Performance of the uranium-free TRU metallic core
Items
Value
Fuel composition
TRU-35%Zr/TRU-19%Zr
Inner core/outer core
TRU inventory (Pu/MA)
2.17 t at BOEC (1.89/0.28 t)
Burn-up reactivity swing
5.1 % dk/kk
0
Power density (average)
260 W/cc
Linear heat rate (average)
220 W/cm
TRU burning rate (Pu/MA)
260 kg/EFPY (230/30 kg/EFPY)
Doppler coefficient at EOEC
À3 Â 10
À3 Tdk/dT
Na void reactivity at EOEC
<0 %dk/kk
0
EOEC end of equilibrium cycle, EFPY effective full-power year
15 Development of Uranium-Free TRU Metallic Fuel Fast Reactor Core
165