Abstract
Studsvik’s approach to spent nuclear fuel analyses combines isotopic concentrations and multi-group cross-sections, calculated by the CASMO5 or HELIOS2 lattice transport codes, with core irradiation history data from the SIMULATE5 reactor core simulator and tabulated isotopic decay data. These data sources are used and processed by the code SNF to predict spent nuclear fuel characteristics. Recent advances in the generation procedure for the SNF decay data are presented. The SNF decay data includes basic data, such as decay constants, atomic masses and nuclide transmutation chains; radiation emission spectra for photons from radioactive decay, alpha-n reactions, bremsstrahlung, and spontaneous fission, electrons and alpha particles from radioactive decay, and neutrons from radioactive decay, spontaneous fission, and alpha-n reactions; decay heat production; and electro-atomic interaction data for bremsstrahlung production. These data are compiled from fundamental (ENDF, ENSDF, TENDL) and processed (ESTAR) sources for nearly 3700 nuclides. A rigorous evaluation procedure of internal consistency checks and comparisons to measurements and benchmarks, and code-to-code verifications is performed at the individual isotope level and using integral characteristics on a fuel assembly level (e.g., decay heat, radioactivity, neutron and gamma sources). Significant challenges are presented by the scope and complexity of the data processing, a dearth of relevant detailed measurements, and reliance on theoretical models for some data.
Highlights
Several decay parameters needed for spent nuclear fuel analyses have been derived from data sources outside the evaluated nuclear data files
Recent advances in ENDF [1], ENSDF [2] and TENDL [3] created a basis for a straight forward procedure for compilation and evaluation of a complete set of decay data
The status of that first step is outlined in this paper along with a few issues encountered during the data evaluation and internal consistency checks
Summary
Several decay parameters needed for spent nuclear fuel analyses have been derived from data sources outside the evaluated nuclear data files. Recent advances in ENDF [1], ENSDF [2] and TENDL [3] created a basis for a straight forward procedure for compilation and evaluation of a complete set of decay data. Such an approach has the advantage of solely using publically available, widely used, well-maintained, well-documented, and regularly updatable databases as the foundation. This approach was adopted by Studsvik in the update of the decay data library of its code for spent fuel analyses, SNF [4]. The status of that first step is outlined in this paper along with a few issues encountered during the data evaluation and internal consistency checks
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