PNNL

Abstract

Three new models were recently added to the US Nuclear Regulatory Commission transient fuel code, FRAPTRAN. A new thermal expansion model was added that better predicts fuel thermal expansion during a reactivity initiated accident (RIA). This model increases the ability of FRAPTRAN to predict measured cladding permanent hoop strains from RIA test rods. A new yield stress correlation was added that better models the yield stress at high temperature and high strain rate. A uniform elongation model was created and added to FRAPTRAN as a strain based failure limit. The FRAPTRAN failure predictions were compared to the measured failure times and enthalpies from several RIA tests. In addition, the FRAPTRAN calculated RIA failure thresholds for standard fuel designs were compared to several other RIA failure thresholds that have recently been published.