Tritium-producing burnable absorber rods (TPBARs) are designed to produce tritium when irradiated in a pressurized water reactor (PWR), within a commercial fuel assembly. Within a TPBAR, annular ceramic pellets consisting of Lithium Aluminate LiAlO2 contain a given linear loading of Li-6, which undergoes neutron capture thus producing Tritium. Obtaining the proper Li-6 loading currently requires blending of powder prior to pellet manufacturing, or volume reduction of a higher lithium loading pellet to that of the desired loading.
This study demonstrates the neutronic performance of both inner and outer volume-reduced Li-6 pellets as comparable to that of a standard dimension, non-milled pellet by modelling 8,250 distinct fuel assembly lattices with Studsvik’s CASMO5. Conditions included are at reactor Hot Full Power (HFP), Hot Zero Power (HZP) and Cold Zero Power (CZP) for 4.80-8.0 U-235 w/o, 8-24 TPBARs, 0-200 IFBAs, and 29-50 mg/in Li-6.
Modeling these possible assembly designs results in a maximum TPBAR rod worth of 900 pcm. A maximum difference in rod worth of 127 pcm and a maximum pin power RMS difference of .0007 shows that volume reduction is a viable option for achieving desired lithium loading. Greatest rodworth and power differences occur between standard dimension non-milled and outer-volume-reduced Li-6 loading.
Revised: August 5, 2020 |
Published: July 31, 2019