Development of a steady-state single-channel model of the BAEC 3MWt TRIGA mark-II research reactor for thermal and hydrodynamic analysis

The Bangladesh Atomic Energy Commission (BAEC) operates the 3 MWt TRIGA MARK II research reactor (BTRR), the only research reactor in Bangladesh, located at the Atomic Energy Research Establishment (AERE) in Savar. Since its commissioning in 1986, the reactor has served multipurpose roles, including training, education, radioisotope production, and various research activities in neutron activation analysis, neutron scattering, and neutron radiography. This study focuses on the development and application of a single-channel model for the BTRR core, providing the capability to analyze the steady-state thermal and hydrodynamic behavior of the reactor under both forced convection and natural circulation cooling modes of operation. An iterative strategy was adopted with external coupling between Monte Carlo neutronics (OpenMC) and the developed single-channel model. The coupled approach captures the feedback between temperature-dependent cross-sections, control rod position, and reactor thermal behavior, enabling more accurate predictions of critical parameters. The model is used with multiple correlations developed by McAdams et al., Bernath, Labuntsov, Mirshak et al., Lund, and the 2006 Groeneveld look-up table (LUT), to determine critical heat flux (CHF) and departure from nucleate boiling ratio (DNBR) for the hottest channel at different power levels under operational conditions. The Bernath correlation, traditionally used for TRIGA reactors, provided conservative CHF estimates, while the 2006 Groeneveld LUT offered higher safety margins. Comparisons with other correlations highlighted variations in CHF predictions, emphasizing the need for a comprehensive approach using multiple correlations to enhance reactor performance and safety. This analysis shows verification of the model against previous code-based calculations and provides detailed insights into predicting critical thermal margins, including CHF and DNBR characteristics of the reactor. The developed model provides a basis for safety predictions and highlights the potential for enhancing reactor performance, including future upgrades to the BTRR core configuration.