Extension of FRAPCON-xt to hydride radial reorientation in dry storage

The dry storage of spent fuel may foster the radial reorientation of hydrides formed in the cladding. This mechanism reduces the material ductility, being a key aspect to assess the cladding integrity. The present work extends the predictive capabilities of FRAPCON-xt (CIEMATs extension to dry storage of the FRAPCON code) to the hydride radial reorientation within the cladding. The validation against experimental data shows the importance of taking into account the modelling uncertainty to explain the errors found. The new version of FRAPCON-xt has been applied to scenarios of 20 years of dry storage of spent fuel, both under realistic conditions of irradiation and dry storage temperature (50 GWd/tU and maximum temperature of 350 degrees C, respectively) and accounting for regulatory limits (62 GWd/tU and 400 degrees C). The predictions obtained (uncertainties included) allow concluding that realistic scenarios prevent the formation of radial hydrides, whereas limiting conditions would not allow ruling it out. (C) 2020 Elsevier Ltd. All rights reserved.