Use of burnup credit in criticality safety design analysis of spent fuel storage systems

In this paper the application of burnup credit to criticality safety design analysis of spent fuel storage systems is described. First of all 'burnup credit' and the different levels of burnup credit used in practice are defined. Then the national practices, ongoing activities and regulatory status of using burnup credit for spent fuel storage systems in different countries are described. Then the key steps and key parameters in burnup credit implementation are discussed. The estimation and validation of the spent fuel isotopic composition are described, the criticality calculation and validation are addressed, and the quantification and verification of the fuel to be loaded in a spent fuel storage system are discussed. (author)