Effect of water-fuel ratio and nuclear fuel type on neutronic characteristics of three petal-shaped fuel pressurized water reactors

• LMDI-CF value formula proposed with k ∞ and four-factor contribution analyzed. • ( 232 Th+ 233 U)O 2 + AlSi has a k ∞ of 1.31228, the highest among the five fuels. • The maximum effective full power days of U-50Zr is the largest, reaching 2100 days. • Increased water-fuel ratio enhances average conversion rate and effective full power days of three petal-shaped fuel PWR. Three petal-shaped fuel rods are new fuel elements. They have great advantages in reactor heat transfer. Thus this paper designs a three petal-shaped fuel reactor with DAG-OpenMC. It also explores water fuel ratio ( V H 2 O / V F ) and fuel types. The fuel types include ( 238 U+ 239 Pu) O 2 + AlSi, ( 232 Th+ 233 U) O 2 + AlSi, ( 232 Th+ 235 U) O 2 + AlSi, ( 235 U+ 238 U) O 2 + AlSi and U-50Zr. The results show that lower V H 2 O / V F increases k ∞ and EFPD through raising fission reaction rate. It also improves ACR through enhancing (n,γ) reaction rate. In addition, when V H 2 O / V F decreases from 2.127 to 1.385, the absolute value of Fuel Temperature Coefficient increases by 6.39%∼57.28%. This further enhances negative reactivity of TPFR. For different fuels, ( 232 Th+ 233 U)O 2 + AlSi, ( 238 U+ 239 Pu)O 2 + AlSi and U-50Zr all have high k ∞ , while ( 232 Th+ 233 U)O 2 + AlSi shows poor breeding performance. Its ACR is minimum at 0.23. ( 238 U+ 239 Pu)O 2 + AlSi has short lifetime. Its EFPD is only 840 days. For U-50Zr, k ∞ can reach up to 1.20403. EFPD can reach up to 2100 days. It ensures breeding capability. It greatly increases TPFR operation time. In summary, U-50Zr is used as fuel and water-fuel ratio is reduced appropriately. This greatly improves the safety and operation time of TPFR.