Izvestiya vuzov. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

Neutron Thermal Scattering Models’ Impact on RBMK Dewatering Effect Calculations

3/27/2026 2026 - #01 Modelling processes at nuclear facilities

Andrianova O.N. Ivanov I.E. Varfolomeeva V.A. Druzhinin V.E.

DOI: https://doi.org/10.26583/npe.2026.1.09

UDC: 621.039.5

The paper investigates the dewatering effect of RBMK in finite lattices with the uranium-erbium fuel, focusing on the sensitivity of calculations to the erbium first-resonance area which is considered from 0.1 eV to 1 eV. The impact of neutron thermal scattering models in water and graphite on forming neutron spectra is discussed. In addition, the update of thermalization models in international nuclear data libraries is considered. The data on the laws of thermal scattering in condensed matter have been updated in foreign libraries of evaluated nuclear data, while earlier models of neutron thermalization sometimes continue to be used in Russian libraries and programs. The MCU code has a specialized module for preparing data on thermal neutron scattering on bound atoms and a library of phonon spectra. The article compares modern models from the ENDF/B-VIII.1 library with the MCU code’s ones and their influence on the calculation of the dewatering effect of the RBMK infinite fuel grid is estimated. The calculations were performed using the MCNP code, and the data on thermal neutron scattering were obtained using the NJOY2016 program and the LEAPR module. The results of test calculations showed that taking into account chemical bonds and changes in the graphite crystal attice during irradiation leads to an increase in reactivity to 1–2 βeff for fresh fuel at temperatures below 400°K. For operating conditions with a burn out depth above 16 MW day/kg the differences in the thermalization models are leveled and their impact on the dewatering effect is reduced to 0.1–0.2 βeff.

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RBMK dewatering effect uranium-erbium fuel free gas model scattering by bound nuclei neutron thermalization

Link for citing the article: Andrianova O.N., Ivanov I.E., Varfolomeeva V.A., Druzhinin V.E. Neutron Thermal Scattering Models’ Impact on RBMK Dewatering Effect Calculations. Izvestiya vuzov. Yadernaya Energetika. 2026, no. 1, pp. 110-121; DOI: https://doi.org/10.26583/npe.2026.1.09 (in Russian).

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