Modeling the Performance of High Burnup Thoria and Urania PWR Fuel
Modeling the Performance of High Burnup Thoria and Urania PWR Fuel

Author: Yun Long

Publisher:

Published: 2002

Total Pages: 217

ISBN-13:

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(Cont.) However, the gas diffusion coefficient in thoria was adjusted to a lower level to account for the smaller observed gas release fraction in the thoria-based fuel. To model accelerated fission gas release at high burnup properly, a new athermal fission gas release model was developed. Other modifications include the thoria fuel properties, fission gas production rate, and the corrosion model to treat advanced cladding materials. The modified version of FRAPCON-3 was calibrated using the measured fission gas release data from the Light Water Breeder Reactor (LWBR) program. Using the new model to calculate the gas release in typical PWR hot pins gives data that indicate that the ThO2-UO2 fuel will have considerably lower fission gas release beyond a burnup of 50 MWd/kgHM. Investigation of the fuel response to an RIA included: (1) reviewing industry simulation tests to understand the mechanisms involved, (2) modifying FRAP-T6 code to simulate the RIA tests and investigate the key contributors to fuel failure (thermal expansion, gaseous swelling, cladding burst stress), and (3) assessing thoria and urania performance during RIA event in typical LWR situations. ThO2-UO2 fuel has been found to have better performance than U02 fuel under RIA event conditions due to its lower thermal expansion and a flatter power distribution in the fuel pellet (less power and less fission gas in the rim region). Overall, thoria has been found to have better performance than urania in both normal and off-normal conditions. However, calculations using the modified FRAPCON-3 ...

Uncertainty and Sensitivity Analysis of Fission Gas Behavior in Engineering-scale Fuel Modeling
Uncertainty and Sensitivity Analysis of Fission Gas Behavior in Engineering-scale Fuel Modeling

Author:

Publisher:

Published: 2014

Total Pages: 11

ISBN-13:

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The role of uncertainties in fission gas behavior calculations as part of engineering-scale nuclear fuel modeling is investigated using the BISON fuel performance code and a recently implemented physics-based model for the coupled fission gas release and swelling. Through the integration of BISON with the DAKOTA software, a sensitivity analysis of the results to selected model parameters is carried out based on UO2 single-pellet simulations covering different power regimes. The parameters are varied within ranges representative of the relative uncertainties and consistent with the information from the open literature. The study leads to an initial quantitative assessment of the uncertainty in fission gas behavior modeling with the parameter characterization presently available. Also, the relative importance of the single parameters is evaluated. Moreover, a sensitivity analysis is carried out based on simulations of a fuel rod irradiation experiment, pointing out a significant impact of the considered uncertainties on the calculated fission gas release and cladding diametral strain. The results of the study indicate that the commonly accepted deviation between calculated and measured fission gas release by a factor of 2 approximately corresponds to the inherent modeling uncertainty at high fission gas release. Nevertheless, higher deviations may be expected for values around 10% and lower. Implications are discussed in terms of directions of research for the improved modeling of fission gas behavior for engineering purposes.