TACO3 - a best-estimate fuel pin thermal analysis code

Economics, limited facilities for spent fuel storage, and efficient utilization of current resources are incentives for extending the discharge burnup limits of nuclear fuel. Extended burnup operation, however, causes abnormal changes in fuel rods. These changes prompted the development of the TACO3 computer code. TACO3 is a best-estimate fuel pin thermal analysis code that was written to provide accurate predictions of fuel pin behavior from the beginning of life through extended burnups. The TACO3 model development effort was divided into three main categories: material, primary, and secondary models. A complete set of best-estimate fuel and cladding material relations was developed in the material model activity. The primary models are defined as those models that significantly affect the fuel temperature predictions while the secondary models have the greatest impact at extended burnups. In this paper, the authors discuss the TACO3 development in these areas and demonstrate the accuracy obtained in benchmark calculations.