The calculation of reactivity differences represents a fundamental concept in nuclear reactor physics and in the validation of neutronic codes. When assessing or validating a code’s accuracy, the comparison is not made directly between the effective multiplication factors (Kₑff), but rather between their corresponding reactivity differences. In this paper, a comparative analysis of the reactivity difference was conducted for a single fuel pin cell of the APR1400 benchmark under various conditions of fuel temperature, uranium enrichment, and boron concentration, resulting in a total of 45 test cases. The simulations were performed using the deterministic code DRAGON5 and the Monte Carlo code OpenMC. The results demonstrate the accuracy, robustness, and efficiency of DRAGON5 in predicting reactivity across a wide range of conditions, confirming its reliability for neutronic analysis. Furthermore, an excellent agreement was observed between the deterministic results of DRAGON5 and the stochastic calculations of OpenMC, validating the consistency and predictive capability of both codes for APR1400 benchmark applications. • A systematic evaluation of reactivity differences for the APR1400 single pin-cell benchmark. • Forty-five test cases analyzed under varying fuel temperatures, enrichments, and boron levels. • Deterministic DRAGON5 and Monte Carlo OpenMC codes compared for reactivity prediction. • DRAGON5 demonstrates good accuracy, robustness, and computational efficiency for reactivity predictions within the investigated conditions. • Overall good agreement is observed between DRAGON5 and OpenMC, with small discrepancies attributable to methodological differences, nuclear data treatment, and Monte Carlo statistical uncertainties.
KIDARI et al. (Wed,) studied this question.