Abstract
The discharge rod internal pressure (RIP) and cladding hoop stress (CHS) distributions are
quantified forWatts BarNuclearUnit 1 (WBN1) fuel rods by modeling core cycle design data, intercycle
assembly movements, operation data (including modeling significant trips and downpowers),
and as-built fuel enrichments and densities of each fuel rod in FRAPCON-3.5. An alternate model
for the amount of helium released from zirconium diboride (ZrB2) integral fuel burnable absorber
(IFBA) layers is derived and applied to FRAPCON output data to quantify the RIP and CHS for
these fuel rods. SCALE/Polaris is used to quantify fuel rod-specific spectral quantities and the
amount of gaseous fission products produced in the fuel for use in FRAPCON inputs. Fuel rods
with ZrB2 IFBA layers (i.e., IFBA rods) are determined to have RIP predictions that are elevated
when compared to fuel rod without IFBA layers (i.e., standard rods) despite the fact that IFBA
rods often have reduced fill pressures and annular fuel blankets. Cumulative distribution functions
(CDFs) are prepared from the distribution of RIP predictions for all standard and IFBA rods. The
provided CDFs allow for the determination of the portion of WBN1 fuel rods that exceed a specified
RIP limit. Lastly, improvements to the computational methodology of FRAPCON are proposed.
