UNF-ST&DARDS: A UNIQUE TOOL FOR SPENT NUCLEAR FUEL CHARACTERIZATION AND LONG-TERM FUEL DATABASE MANAGEMENT

The Used Nuclear Fuel-Storage, Transportation & Disposal Analysis Resource and
Data System (UNF-ST&DARDS) is being developed as a foundational resource for the
US Department of Energy (DOE) Office of Nuclear Energy to manage spent nuclear
fuel (SNF) data, along with several compatible analysis tools for time-dependent
characterization of SNF and related systems. UNF-ST&DARDS has the unparalleled
ability to track SNF through the entire back end of the fuel cycle—from the time the fuel
is discharged from a reactor through its disposal in a geological repository.
UNF-ST&DARDS interfaces with the SCALE code system for nuclear analysis and
COBRA-SFS for thermal analysis. This paper presents various capabilities of
UNF-ST&DARDS, including (1) storing and preserving SNF data for generations,
(2) automated characterization of time-dependent attributes, including assemblyspecific decay heat and isotopic content, as well as criticality, dose rate, and
temperature for dry storage systems, and (3) design-basis criticality, shielding, and
thermal analysis capabilities. This paper also describes a newly implemented dry
storage loading algorithm which ensures proper decay heat management in the spent
fuel pool (SFP) and prompt removal of fuel from the SFP after reactor shutdown. The
algorithm minimizes the time needed to age SNF on the storage pad, which may be
required before offsite transportation to meet transport cask design requirements.
Various applications of UNF-ST&DARDS data and analysis capabilities for
management of long-term storage, aging, and transportation are also reviewed*
.