Development of the Code GOLT for Performance Evaluation of Coated-Particles Fuel

The coated particles (CP) performance computer code GOLT (Russian abbreviation of Gas-Cooled Fuel) is under development at the A. A. Bochvar All-Russia Research Institute of Inorganic Materials. The main goal of the code is supporting development of fuel for the Gas-Turbine Modular Helium Reactor (GT-MHR). The first version GOLT-v1 has capable to calculate temperature distribution along particle radius, fuel kernel swelling, development of internal pressure under coating due to formation of gaseous fission products and CO, development of stresses and deformation in each coating layer. For TRISO-type particles special probabilistic failure model was developed. According to the failure model integrated probability of silicon carbide failure depends on probability of each dense pyrocarbon layer failure. Probabilistic version GOLT-v2 takes into account possibility of gap formation between buffer and inner dense pyrocarbon layer or between kernel and buffer that influences on maximal fuel temperature and stresses distribution in coating. More detail model of buffer performance at irradiation was developed and included in the code. List of probable coating failure mechanisms was extended. The ability of coating failure due to Kernel-Coating Mechanical Interaction (KCMI) as well as model of failure due to kernel migration was added. Thermo-dynamical code ASTRA is used in some tasks as supporting tool for calculating internal pressure and chemical interaction between SiC coating and fission products and CO. The version GOLT-v3 has accumulated all capabilities of previous versions and included Monte-Carlo analysis for estimation of fraction of failed particles with account of statistical dispersion of structural, materials and operating parameters. In the paper short description of capabilities of last versions of the code is presented. Main attention is putted to results of development version GOLT-v2a for evaluation fuel performance during accidents.