Experimental study of neutronic parameters in Tehran research reactor mixed-core

• Extensive neutronic analysis of Tehran research reactor mixed-core has been done.
• Worth of all SRs measured experimentally with stable positive period method.
• Thermal power calibration was done by calorimetric method.
• The experimental value of power defect compared with calculation value in both mixed and reference cores.
• Thermal neutron flux measured experimentally in IR-BOX positions.

In this work, general characteristics of a typical mixed core, including HEU & LEU fuel is studied. The study is performed in the Tehran research reactor (TRR). In this study the neutronic parameters, reactivity feedback coefficients and kinetic parameters are investigated. The reference core designated for such study is the equilibrium core (No. 61) with an average bun-up of 27% & 36% for SFE's & CFE's, respectively. The MTR_PC package is used for neutronic analysis. In this research, experimental and computational results for the reference and mixed core are compared. Meantime, the obtained values for neutronic parameters are mostly below the adopted safety criteria and they are in good agreement with the experimental results. However βeff and ℓp are a little bit higher in the mixed core with respect to the reference core, but in practice, these small changes will not cause substantial impacts on the dynamic behaviour of the reactor core. The absolute values of the fuel temperature, moderator density and void coefficients of reactivity, are less in the mixed core and only the moderator temperature coefficient is higher. The calculated values of power defect, based on the reactivity coefficients; in both core configurations are in good agreement with the experimental values.