Burnup-Dependent Neutron Spectrum Behaviour of a Pressurised Water Reactor Fuel Assembly

Journal article

Margulis, M. and Mweetwa, B. M. 2024. Burnup-Dependent Neutron Spectrum Behaviour of a Pressurised Water Reactor Fuel Assembly. Journal of Nuclear Engineering . 5 (1), pp. 44-56. https://doi.org/10.3390/jne5010004
AuthorsMargulis, M. and Mweetwa, B. M.

Understanding the behaviour of a neutron spectrum with burnup is important for describing various phenomena associated with reactor operation. The quest to understand the neutron spectrum comes with a lot of questions. One question that is usually asked by students is: Does the neutron spectrum harden or soften with burnup? Most textbooks used by students do not provide a definite answer to this question. This paper seeks to answer this question using a 3D model of a standard 17 × 17 pressurised water reactor fuel assembly. Two cases were studied using the Serpent Monte Carlo code: the first considered the fuel assembly with constant boron concentration (traditionally found in many published papers), and the second considered boron iteration (where the boron concentration was reduced with burnup). Neutron spectra for the two cases at beginning of life and end of life were compared for spectral shifts. In addition, thermal spectral indices were used to assess spectrum hardening or softening with burnup. Spectral shifts to lower energies were observed in the thermal region of the neutron spectrum, whereas the fast region experienced no spectral shift. There was an increase in thermal spectral indices indicating that the spectrum became soft with burnup.

Keywords absorption heating; spectrum hardening; diffusion cooling
JournalJournal of Nuclear Engineering
Journal citation5 (1), pp. 44-56
ISSN 2673-4362
Digital Object Identifier (DOI)https://doi.org/10.3390/jne5010004
Web address (URL)https://doi.org/10.3390/jne5010004
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Output statusPublished
Publication dates
Online29 Jan 2024
Publication process dates
Deposited11 Apr 2024
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License: CC BY 4.0
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