Foreseen applications of nuclear fuel operating at lower temperatures than current reactors call for the description of specific phenomena occurring in this temperature range. Among these, athermal fission gas release is of particular interest since it is expected to dominate the overall fission gas behaviour at low temperatures. This holds particular significance for certain Small Modular Reactor designs and even for fast neutron reactors employing fuels with high thermal conductivity, such as nitride fuels. Additionally, its implications extend to normal irradiation conditions in light water reactors and to spent fuel storage conditions. In this work, an AIenhanced physics-based model of the athermal fission gas behaviour is presented, extending mechanistic models available in the open literature. The athermal release, defined as the fraction of gas vented from the fuel through its open porosity, is accounted for via the solution of the gas diffusion within the fuel grain, evaluating the fraction of the concentration gradient in the proximity of grain edges. The results of such computation are included in the SCIANTIX code thanks to a dedicated neural network, aimed at encapsulating the complex dependencies affecting the athermal release, whilst ensuring a computational time in line with fuel performance applications. Additionally, in the context of this analysis, semi-empirical models for solid fission products swelling and fuel densification are incorporated as well, providing a modelling suite for low-temperature conditions. The consistency of the model is tested with data available in the literature.

PAGANI Arianna;  PIZZOCRI Davide;  ZULLO Giovanni;  VAN UFFELEN Paul;  LUZZI Lelio; 

2026-06-03

ELSEVIER

JRC141097

1873-4820 (online),   

https://www.sciencedirect.com/science/article/pii/S0022311526003132?via%3Dihub,    https://publications.jrc.ec.europa.eu/repository/handle/JRC141097,   

10.1016/j.jnucmat.2026.156748 (online),