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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]

The mass attenuation coefficient (MAC), effective atomic number (Zeff), and effective electron density (Neff) values of soils in mangrove forests across the Philippine islands were investigated. In addition, ENDF/B-VI.8 cross-section data library was used for interpolating Zeff and Neff values. Photon energies considered in this study ranged from 59.5-1332 keV. MAC values were obtained using MCNP5 and PHITS Monte Carlo (MC) simulations and were found to be in good agreement with XCOM and values in literature. Results for Zeff were in good agreement with values obtained using Phy-X/ZeXTRa program. Each shielding parameter was investigated as a function of SiO2 concentrations. [ABSTRACT FROM AUTHOR]

A multi-shell neutron spectrometer with indium foil detector (In-MuNS) was developed to evaluate intense neutron fields that are generated in medical accelerators. The response matrix of this new spectrometer was calculated from 1 meV to 100 MeV using MCNP5 v.1.6 with ENDF/B-VIII.0 nuclear data. An experiment with a252Cf source with known emission rate was performed to validate the computational model of the spectrometer. This included detailed modelling of the irradiation room to evaluate the room-scattered field. The contribution of scattered neutrons to the induced activity in the foil reached 30% for the smallest sphere configuration (diameter 5.0 cm). The quotient between the experimental and simulated foil activity remained satisfactorily constant (1.03 ± 0.04) as the sphere diameter varied, demonstrating the validity of the simulation model. In-MuNS proved to be a portable and compact alternative to conventional Bonner spheres. • A portable and flexible design for passive neutron spectrometry system is presented. • An indium-based multi-sphere neutron spectrometer (In-MuNS) was developed. • The In-MuNS computational model was validated using a252Cf source. • Scattered neutron in the validation experiment was analyzed. [ABSTRACT FROM AUTHOR]

A method for estimating source strength measurements of californium neutron sources is presented, based on the model of 252Cf, 250Cf, and 248Cm decay. This is combined with the Monte Carlo method (MCM) of propagating uncertainties. Californium sources were categorized into two types: Sort–A are those with most input quantities known while Sort–B are sources with only the mass at a certain reference date known. For Sort–A, the spread of all input quantities was estimated with Gaussian distribution and the deterministic 1st order GUM uncertainty propagation is applied to validate the MCM results. While, for Sort–B with inputs that have non-Gaussian distributions, only MCM is applied to evaluate uncertainties. Results show that for californium sources that are 25 y or older, a simple 252Cf decay correction is imprecise due to the contribution of 250Cf and 248Cm. The MCM was also shown to be a robust technique for uncertainty analysis that provides results for both Gaussian and non-Gaussian distributions. Moreover, the time-dependence of the contributors in the source strength and the corresponding uncertainties are presented. When exceedingly low uncertainties are not required, the calculation techniques presented in this work may serve as an alternative to actual measurements, which tend to be expensive. • A method of estimating neutron source strength was investigated. • Monte Carlo method in GUM supplement 1 was used for uncertainty propagation. • The consequences of the nuclear data uncertainties in literature were evaluated. • The consequence of an unknown isotopic impurity content was evaluated. • The consequences of unknown dates of isotopic analysis and Cm separation were evaluated. [ABSTRACT FROM AUTHOR]