b'-20 Figure 1. Control Rod Worth vs. Burnup-30rth, (% delta-k/k) Control rod wo -40-50UO2-Zr-7.0 w/o-AICUO2-Zr-7.0w/o HfCR-60 UO2-Zr-4.95w/o AICUO2-Zr-7.0w/o HfB2CRUO2-Zr-7.0 w/o-HfO2-70 UO2-Zr-7.0 w/o-HfC-800 10 20 30 40 50 60 70Burn-up (GWd/t)Laboratory (BNL) in 2019 and anControl rod geometry were evalu-ongoing Nuclear Energy Universityated via scoping calculations withProject (NEUP) on accident toleranta detailed TRITON model of acontrol rods (ATCR) Westinghouse 17x17 fuel assembly. The standard AIC control rod Accomplishments: (24-rodlets) was replaced by selected There are a number of candidatehafnium-based control rods with: options for more robust controlHf, HfB 2 , HfO 2 , HfC. Control rod rods (higher temperature, reducedworths as a function of fuel burnup hydrogen generation, minimizeare shown in Figure 1 based on adverse chemical and mechanicalbranch calculation of rod-out/interactions) to complement fuelsrod-in, i.e., the control rod material with enhanced ATF. These includeremained at its initial composition.rare-earths (e.g., Re 2 O 3where Re=Gd,Based on these preliminary results Er, Dy, etc.), hafnium, etc. Theseonly HfB 2offers the desired increased have been considered in combina- reactivity worth, recognizing that tion with material other than thethe boron in the present analyses stainless steel currently used for theassumed natural boron. These sheath/cladding (e.g., SiC, FeCrAl)results suggest that hafnium-based as well as bare. In the presentcontrol rod material, other than HfB 2work, options based on hafnium asdo not provide the desired enhance a replacement for AIC in a stainlessreactivity worth for fuels with steel sheath in the standard PWRenrichment of 7 w/o.2022|AFC ACCOMPLISHMENTS 101'