Ex-core neutron detector response in a typical PWR nuclear power plantGoričanec, Tanja (Avtor) Snoj, Luka (Mentor) Kromar, Marjan (Komentor) PWRMCNPADVANTGMonte Carloneutron transportneutron detectorcontrol rod worthredistribution factorsNEKearthquakeFor safe and continuous operation of nuclear power plant, it is important to accurately control the reactivity. Reactivity in a typical pressurized water reactor is controlled by boric acid dissolved in the moderator, the control rods, and the burnable absorbers present in the core. The control rod reactivity worth is a safety related physical reactor parameter and can be determined by calculations and by measurements. One of the methods for measuring control rod worth is the rod insertion method, in which the change of neutron population is measured with a neutron detector positioned outside the reactor core during the continuous insertion of a control rod bank. As the control rod moves, the neutron and power distribution in the reactor core changes. This redistribution can alter the reading of the ex-core detectors, resulting in a nonlinear determination of the control rod reactivity worth. To evaluate the response of the ex-core detector and the redistributions due to the control rod movement, a detailed model of the reactor core geometry of the Krško nuclear power plant with the surrounding structures was developed as part of the dissertation. The developed models were used with state-of-the-art neutron transport methods and programs. The major part of this work deals with sensitivity analysis, verification and validation of the developed methods and models. The methods and models developed in this work were used to calculate the axial neutron flux and reaction rate redistribution factors and used them to analyse the rod insertion method measurements. The possibility to use intermediate-range detectors for rod insertion measurements is presented. Comparison with the boron dilution measurements confirmed good agreement in the control rod worth within 2 %. The obtained axial reaction rate redistribution factors and measurements with intermediate-range detectors can be used to update the analysis of the rod insertion method and to improve the determination of the control rod reactivity worth. The work presents a novelty in the neutron transport calculations of nuclear power plants and opens up a wide variety of possible implementations in the future.20232023-10-12 11:29:47Doktorsko delo/naloga151613VisID: 138355COBISS_ID: 168063747sl