Ядерна фізика та енергетика Nuclear Physics and Atomic Energy   ISSN: 1818-331X (Print), 2074-0565 (Online)   Publisher: Institute for Nuclear Research of the National Academy of Sciences of Ukraine   Languages: Ukrainian, English, Russian   Periodicity: 4 times per year   Open access peer reviewed journal

Full text (ru)

Abstract: Fuel rods linear power rate is one of the most important indicators of safety and operating reliability of VVER fuel. The article describes the evolution of implementation of in-core monitoring system (ICMS) power distribution control function for VVER core. It is shown that requirements for the data and accuracy of determining the power distribution have significantly increased in comparison with the first VVER projects. This work presents results of MCNP numerical simulations of the signal formation in the Self-Powered Neutron Detector (SPND), which is resulted from the activation of emitter’s nuclei under the neutron irradiation. It has been demonstrated that the main contribution (~75 %) to the SPND signal provide fuel rods of fuel assembly in which SPND is located, and the fuel rods of adjacent fuel assemblies contribute ~25 %. Also, the height-dependent contribution of fuel rod to SPND signal was determined. The simulation results allow calculation of the geometric factor, which determines the contribution of fuel elements to SPND signal, taking into account not only six closest fuel rods, as implemented in the ICMS now, but few adjacent rows of fuel rods. This approach will improve the accuracy of the geometric factor calculation. The obtained results indicate the need to consider the effect of the spectral characteristics of neutron field on the SPND signal.

Keywords: linear power rate, reconstruction of power distribution, self-powered neutron detector, activation of rhodium emitter, burning of rhodium emitter.

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