The advancement of materials research for the nuclear industry is growing as energy demand increases [1],[2]. As a result, new materials are being explored to improve the efficiency of nuclear applications. Molybdenum has been studied for decades as an alloying element due to its low thermal neutron absorption cross-section and high strength under nuclear reactor temperature conditions [3],[4]. A critical reactor condition is understanding how fuel rods behave during the fission reaction of UO2 pellets [5],[6] and, consequently, how heat transfer occurs in this process. To understand these key characteristics, a study was conducted on the criticality of a fuel rod clad with Zircaloy doped with molybdenum nanoparticles [7],[8] using MCNP code simulations. Simulations of the fuel element were performed with a 3.2%, 2.5%, and 1.9% UO2 enrichment distribution based on a hypothetical PWR reactor model [6]. A hypothetical fuel element for a hypothetical PWR reactor was simulated using the MCNP5 software. The element consisted of 25 fuel rods with UO2 pellets with three enrichment zones (3.2%, 2.5%, and 1.9%), as shown in Figure 1, and a height of 3.6 m. The kcode was used in the simulation to calculate the criticality of the simulated fuel. 10,000 neutrons per cycle and a total of 100 cycles were used, with 50 of them being passive. To achieve the objective of the work, the first simulation was performed with pure Zircaloy-4, and this result was considered as the reference standard criticality for the fuel element. The second simulation was performed with this alloy doped with 10% molybdenum.The result obtained for the effective multiplication factor (kef f ) with the coated rod under study was equal to kef f = 1.314503 ± 0.0007, which when compared to the reference value without doping kef f = 1.39207 ± 0.00072, a relative percentage deviation of approximately |δ| ≈ 5.57% is obtained. Doping Zircaloy with molybdenum nanoparticles does not significantly alter neutron production. This enables the improvement of the alloy without loss of energy production efficiency. The results of the simulations indicate that the doping of Zircaloy with molybdenum nanoparticles does not significantly alter the neutron production of the fuel rod. This is an important finding, as it suggests that the addition of molybdenum nanoparticles can improve the properties of the Zircaloy alloy without sacrificing its efficiency in terms of energy production. The relative percentage deviation of |δ| ≈ 5.57% between the kef f values for the doped and undoped rods is considered to be small. This suggests that the doping of Zircaloy with molybdenum nanoparticles does not have a significant impact on the criticality of the fuel rod. Overall, the results of this study suggest that the doping of Zircaloy with molybdenum nanoparticles is a promising approach for improving the properties of the alloy without sacrificing its efficiency in terms of energy production. Further research is needed to confirm these findings and to explore the potential benefits of molybdenum doping in more detail.