Nuclear Science and Engineering / Volume 152 / Number 3 / March 2006 / Pages 306-313
Current burnable absorbers such as boron carbide placed in the control rod guide tubes of fresh fuel assemblies create a water displacement penalty at end of cycle (EOC) that reduces the overall maximum cycle length of the reactor. Other burnable absorbers such as gadolinium-oxide mixed in the fuel do not create the water displacement penalty but create a lower centerline melt temperature for the fresh fuel and reduce the overall enrichment for the assembly. This research proposes using a transuranic (TRU) isotope with a relatively high absorption cross section such as 240Pu to reduce excess criticality within the reactor at beginning of cycle. The added benefit of using this TRU isotope over a standard burnable absorber is that when it absorbs a neutron it no longer negatively affects the criticality of the reactor, and it will transmutate into a fissile material that will add to the overall criticality of the reactor at EOC.