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The Philippine Research Reactor-1 (PRR-1) will be revived as a subcritical assembly for training, education, and research (SATER) in the field of nuclear science and technology. SATER will utilize the existing slightly irradiated nuclear fuel rods that have been maintained in the PRR-1 facility for more than 30 years. A subcritical arrangement for the fuel rods was chosen considering the inherent safety of this configuration. In this paper, we calculate relevant reactor parameters that characterize different annular and hexagonal subcritical configurations of 44 PRR-1 fuel rods. These parameters include the neutron multiplication factor (), the effective delayed neutron fraction (), and the mean neutron generation time (), which are essential quantities to describe reactor behavior. Calculations were performed using the well-validated Monte Carlo radiation transport code MCNP5 v.1.6 together with the ENDF/BVII. 1 evaluated nuclear data library. The maximum value is at 4.0 cm pitch for the chosen annular arrangement, while the maximum value is at 4.3 cm pitch for the chosen hexagonal arrangement. For these configurations, the reactor kinetic parameters were and for the annular arrangement, while and for the hexagonal arrangement. Results demonstrate that with 44 fuel rods, different fuel arrangements remain subcritical with a subcriticality margin that is at least or maximum of 0.97. The key reactor performance characteristics determined in this study can aid in the analysis of transient behavior and safety assessment of subcritical core configurations with TRIGA fuel rods. Our results provide support in expanding the utilization options for irradiated TRIGA fuel rods, even for other TRIGA facilities. [ABSTRACT FROM AUTHOR]

A fast neutron mass removal cross sections (Σ R / ρ) database covering the elemental range of Z = 1 to 92 is generated for source neutron energy distributions based on 241Am–Be, 252Cf, and 235U. Monte Carlo simulations using ENDF/B-VIII.0 nuclear data were performed with the fast neutron removal theory's ideal spherical representation. The ENDF/B-VIII.0-based Σ R / ρ ′s derived were compared with values from the Oak Ridge National Laboratory's Lid Tank Shielding Facility (LTSF) experiments, values from software Phy-X/PSD and MRCsC, values obtained by an empirical model in Zoller, and values derived using the older ENDF/B-VII.0 nuclear data library. Subsequently, the generated Σ R / ρ ′s were evaluated for convergence under varying moderator thickness. Results indicate that the Σ R / ρ quantity for fission and (alpha, n) spectra is universal, with slight deviations for low Z elements. The Σ R / ρ values generated from ENDF/B-VIII.0 agreed with LTSF experiments with an average relative deviation of 8.58%. Moreover, using ENDF/B-VIII.0-based Σ R / ρ ′s, the derived fast neutron effective removal cross sections (Σ R 's) for several light compounds and dry concrete have better agreement on average with LTSF experiments compared with values derived from the available Σ R / ρ ′s in the literature. Significant differences were found for Σ R / ρ ′s that were generated with ENDF/B-VIII.0 as compared with the superseded ENDF/B-VII.0. Furthermore, ENDF/B-generated Σ R / ρ ′s through spherical model showed the expected convergence towards singular values at moderator thicknesses practical for fast neutron removal theory applications. Owing to the relatively high unavoidable uncertainties of the LTSF experimental Σ R / ρ ′s, the ENDF/B-VIII.0-based Σ R / ρ ′s present a new and potentially favorable database in Σ R general calculations for homogeneous multi-element materials for point-kernel shielding applications. • A Σ R / ρ database was produced using the latest ENDF/B via multi-layer sphere model. • Produced Σ R / ρ ′s led to calculated Σ R values close to LTSF experimental measurement. • All Σ R / ρ ′s for fission and (α,n) neutron source energy spectra were similar. • Differences were found in Σ R / ρ ′s produced using 7th and 8th versions of ENDF/B. • Convergence of Σ R / ρ ′s at increasing moderator thickness was demonstrated. [ABSTRACT FROM AUTHOR]