Establishing a LOCA Fuel Safety Evaluation Methodology for Assessment of Advanced Technology Fuel Performance Using FRAPTRAN-TE-1.5

Abstract

To aid its Member States in the development and performance assessment of Accident Tolerant and Advanced Technology Fuels (ATFs), the International Atomic Energy Agency (IAEA) initiated a Coordinated Research Project (CRP) on Testing and Simulation for ATFs (ATF-TS) in 2021. Tractebel has participated in this IAEA CRP, with the goal of developing a best estimate plus uncertainty (BEPU) hot rod LOCA fuel safety evaluation methodology for assessing the performance of ATF with Cr-coated cladding under Loss-of-Coolant Accident (LOCA) conditions. This methodology was based on the hot rod thermal hydraulic boundary conditions computed by the system thermal hydraulic code TRACE for a large-break LOCA of a typical Pressurized Water Reactor (PWR), and a modified fuel rod code FRAPTRAN-TE-1.5. The original FRAPTRAN-1.5 code was improved by incorporating a high-temperature creep model and a burst model, crucial for simulating Cr-coated cladding ballooning and burst during LOCA. The updated FRAPTRAN-TE-1.5 code was utilized to simulate selected LOCA burst tests with Cr-coated Optimized ZIRLO cladding, conducted within the ATF-TS CRP, to calibrate the creep model parameters and quantify the associated uncertainties. The updated FRAPTRAN-TE-1.5 code was subsequently used to predict the expected behaviors of the integral single rod LOCA tests performed at the Halden reactor (IFA-650.9 and IFA-650.10) with uncoated and Cr-coated cladding, for the purpose of validating the models. Lastly, the updated FRAPTRAN-TE-1.5 code was employed to develop a BEPU hot rod FSEM based on the hot rod thermal hydraulic boundary conditions for the reference fuel rod and to predict the expected behavior of the ATF with Cr-coated cladding for the PWR large-break LOCA scenario, in comparison with the behavior of the reference fuel rod with un-coated cladding. This paper presents the developed hot rod LOCA fuel safety evaluation methodology and its application to assess the performance of the ATF with micro-cell fuel pellet and Cr-coated cladding.