The Yongbyon reactor in North Korea represents a significant global security threat because of its potential for plutonium production, which can be utilized in nuclear weapons. The nuclear tests conducted at the Yongbyon research reactor from 2006 to 2017 highlight the necessity for accurate assessments of its plutonium production capabilities. This study estimated the plutonium production potential of the Yongbyon reactor to be ~51 kg, based on its operational history and analysis using the Monte Carlo code for advanced reactor design (McCARD) code. Sensitivity analysis indicates that the most critical variable for predicting plutonium production capacity is the integrated thermal power release data from the reactor. Factors such as the temperature of fuel and coolant, and the number of neutron samples in the McCARD have a negligible impact (less than 1%) on the estimates of plutonium production. Regardless of how diverse the history of thermal power is, or what value the maximum power reaches (20 or 25 MWt), the integrated thermal energy consistently determines the amount of plutonium produced, emphasizing its significance in the analysis.