Research to Support Expansion of U.S. Regulatory Position on Burnup Credit for Transport and Storage Casks

In 1999, the United States Nuclear Regulatory Commission (U.S. NRC) initiated a research program
to support the development of technical bases and guidance that would facilitate the implementation of burnup
credit into licensing activities for transport and dry cask storage. This paper reviews the following major areas of
investigation: (1) specification of axial burnup profiles, (2) assumption on cooling time, (3) allowance for
assemblies with fixed and removable neutron absorbers, (4) the need for a burnup margin for fuel with initial
enrichments over 4 wt %, and (5) evaluation of experimental data. Recommendations resulting from the research
program are presented.