Calculation, measurement and sensitivity analysis of kinetic parameters of Tehran Research Reactor

Abstract

Effective delayed neutron fraction β eff and neutron generation time Λ are important factors in reactor physics calculation and transient analysis. In the first stage of this research, these kinetic parameters have been calculated for two states of Tehran Research Reactor (TRR), i.e. cold (fuel, clad and coolant temperatures equal to 20 °C) and hot (fuel, clad and coolant temperatures of 65, 49 and 44 °C, respectively) states using MTR_PC code. In the second stage, these parameters have been measured with an experimental method based on Inhour equation. For the cold state, calculated β eff and Λ by MTR_PC code are 0.008315 and 30.190 μs, respectively. In the hot state, these parameters being 0.008303 and 33.828 μs, respectively. The measured β eff and Λ for the cold state (reactor power in the range of 100–200 W) being 0.008088 and 32.001 μs, respectively. The calculated and measured values are in good agreement. Relative percent errors are about 2.8% for β eff and 5.7% for Λ which are smaller than the other reported results. In the third stage of the research, variations of β eff and Λ vs. fuel enrichment are investigated in cold and hot states. Comparative analysis shows that both β eff and Λ increase as fuel enrichment decreases. However, the variation rate of β eff is not the same in the two conditions. β eff in the hot state is larger than that calculated in the cold state when fuel enrichment is more than 83.91%, while the situation is vice versa for the enrichments smaller than the aforementioned value. Calculated neutron generation time shows normal behavior for all different fuel enrichments. All variables involved in kinetic parameters calculations (i.e., neutron fission cross section, fuel enrichment, etc.) are investigated theoretically to evaluate the results of calculations in cold and hot states. Variations of β eff and Λ with fuel burnup are also studied.