Theoretical Foundations and Application of the Westcott Formalism in ko-Standardized Instrumental Neutron Activation Analysis at the Low-Enriched Uranium Nigeria Research Reactor-1 (LEU-NIRR-1)
DOI:
https://doi.org/10.33003/fjs-2025-0912-5690Keywords:
Westcott formalism, k_{0}-standardization, rumental neutron activation analysis, Neutron spectrum parameters, Theoretical foundations, HEU-to-LEU conversion, Non-1/v nuclidesAbstract
Instrumental neutron activation analysis (INAA) based on the -standardization method is a powerful multi-element technique whose accuracy depends on a sound theoretical treatment of neutron reaction rates and precise characterization of the irradiation facility. This study examines the theoretical foundations of the Westcott formalism and its integration with the -standardization method, with specific application to the Low-Enriched Uranium Nigeria Research Reactor-1 (LEU-NIRR-1). The work reviews the nuclear physics of neutron capture, contrasting the Høgdahl convention (valid for nuclides) with the Westcott formalism required for non- nuclides. Modified Westcott expressions incorporating the epithermal shape factor and neutron temperature are linked to the practical concentration equation. Reactor-physics aspects of LEU-NIRR-1 are examined, focusing on the 2018 HEU-to-LEU conversion. Experimental and computational determinations of the spectrum parameters and are reviewed for both cores. Results show only modest spectral hardening, with inner-channel values of and , and outer-channel values of and . These parameters, together with detector-efficiency calibration and true-coincidence summing corrections, enable reliable application of both Høgdahl and Westcott forms of the method. Advantages of the combined approach are weighed against limitations from nuclear-data uncertainties. Current research trends, including post-conversion validation and refinement of factors, are surveyed. The study demonstrates that LEU-NIRR-1 retains a stable, well-thermalised spectrum fully compatible with high-quality -INAA, providing a robust foundation for multi-element analysis and a reference for other converted Miniature Neutron Source Reactors.
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