Burnup credit (BUC) is a concept applied in the criticality safety analysis of spent nuclear fuel
in which credit or partial credit is taken for the reduced reactivity worth of the fuel due to both fissile
depletion and the buildup of actinides and fission products that act as net neutron absorbers.
Typically, a two-step process is applied in BUC analysis: first, depletion calculations are performed
to estimate the isotopic content of spent fuel based on its burnup history; second, three-dimensional

This paper provides a brief description of the United States Nuclear Regulatory Commission (NRC) and its regulatory process for the current nuclear fuel cycle for light water power reactors (LWRs). It focuses on the regulatory framework for the licensing of facilities in the fuel cycle. The first part of the paper provides an overview of the NRC and its regulatory program including a description of its organization, function, authority, and responsibilities.

The radionuclide characteristics of light-water-reactor (LWR) spent fuel play key roles in the design
and licensing activities for radioactive waste transportation systems, interim storage facilities, and the final
repository site. Several areas of analysis require detailed information concerning the time-dependent behavior
of radioactive nuclides including (1) neutron/gamma-ray sources for shielding studies, (2) fissile/absorber
concentrations for criticality safety determinations, (3) residual decay heat predictions for thermal