Numerical and experimental study of control rods effects on neutronic power in TRR

Power of nuclear reactors are measured through different methods. Neutron Detectors are usually used for online power monitoring of nuclear reactors. The measured power by neutronic detectors is affected by the positions of control rods (CRs) in the core. The main contribution of this research is to investigate the effect of the CRs position on power monitoring in Tehran Research Reactor (TRR) from experimental and simulation aspects. The MTR_PC package is used to evaluate the effect of partial insertion of the CRs on the power calibration at the operating core of the TRR. The maximum impact of CRs position on the NDs response is about 25% during a cycle. Results of the thermal power calibration experiment are used to investigate the CRs effect on power calibration. In the first experiment, the results of two thermal power calibrations, with the same monitoring power 2 MW at the different configurations of CRs, are compared. Experimental investigation illustrates 9.5% changes in the real thermal power of TRR, while simulation predicts about 11%. In the second experiment, the power of TRR is increased to 5 MW and the thermal power calibration has been repeated in the new position of CRs and its result is compared with 5 MW. Both of the experiment and modeling results predict a similar effect of CRs on power calibration. •The main contribution of this research is to investigate the effect of the CRs position on power monitoring in TRR.•The best location for ND installation determined with calculations.•The experiment results verified the simulation results in both cases of CRs swapping and movement.•The relations between reactor power, control rods position and worth of control rods, has been shown in one figure.