Tritium production pathways are well-established for large pressurized water reactors (PWRs). Integrated small reactors (ISRs), however, operate without soluble boron reactivity control and use no chemical additives (e.g., lithium hydroxide) for pH adjustment, necessitating dedicated analysis of their tritium sources.

This study aims to identify tritium production pathways in ISRs, establish a computational model for quantifying tritium source terms, and propose design optimizations to minimize tritium generation.

A theoretical model was established by solving differential equations for tritium production and removal based on identified neutron activation reaction mechanisms. Key parameters included neutron flux and nuclear cross-sections derived from Monte Carlo simulations of the ISR core. Validation was performed against normalized operational tritium release data from boiling water reactors (BWRs) with analogous B₄C control rods and Sb-Be neutron sources, considering thermal power and load factors.

The annual tritium production in ISR primary coolant is 1.81 TBq. The primary contributors are neutron-activated products from Sb-Be and B₄C material, accounting for 46% and 51% of the total production, respectively. Analysis of tritium discharge data from operational BWRs validates the conservatism of the theoretical results.

Optimizing secondary neutron sources (canceling Sb-Be or using double-encapsulated cladding) and replacing B₄C control rods with non-tritium-producing absorbers (e.g., Ag-In-Cd or hafnium) could reduce ISR tritium production significantly. These measures are technically feasible based on PWRs operational experience and are recommended for ISR design enhancements. Future work will refine release fractions of control rods using plant-specific operational data.