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   Periodicity: 4 times per year   Open access peer reviewed journal

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V. A. Babenko^1,2,*, V. M. Pavlovych¹, I. A. Khomych¹, V. I. Slisenko¹, V. V. Tryshyn¹, O. P. Volokh<sup>1

1</sup> Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kyiv, Ukraine
² Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Kyiv, Ukraine

^*Corresponding author. E-mail address: pet2@ukr.net

Abstract: We have analyzed the activities conducted at the WWR-M nuclear research reactor of the Institute for Nuclear Research, NAS of Ukraine, over the past five years, with a focus on nuclear safety and ongoing research efforts. In 2019-2022, preparatory work was carried out for the irradiation of surveillance specimens of nuclear power reactor vessel metals in the vertical channels of the WWR-M reactor, commissioned by National Nuclear Energy Generating Company (NNEC) "Energoatom". To support this effort, vertical channels for sample irradiation were designed and manufactured, and computational analyses were performed to determine the optimal core configuration, the optimal placement of channels within the core, neutron flux distributions, and the required irradiation time. The research presented here is based on computational modeling using the MCNP-4C code, with calculations performed to evaluate neutron fluxes, reactivity parameters, and nuclear safety margins. For each configuration, critical nuclear safety parameters were determined, including the reactivity margin, the control rod worth, the reactivity of the irradiated channels, and that of each fuel assembly. The analysis confirmed the feasibility of the proposed configuration and provided essential insights into optimizing neutron flux distributions and reactivity control. In early 2022, all reactor operations were halted, and the fuel was removed from the core and transferred to storage facilities. As a result, the need arose to improve the nuclear safety justification for the spent nuclear fuel storage facility, taking into account the actual arrangement of fuel assemblies. The present work examines reactor safety considerations and explores approaches to improving the justification of spent fuel storage. It also presents the results of a series of such calculations that were initiated and remain ongoing. Overall, our research contributes to current efforts in nuclear safety assessment and provides a foundation for future investigations in this field.

Keywords: WWR-M research reactor, fuel assembly, nuclear fuel, storage facility.

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