ENDF/B-VII.1 Decay Sublibrary

ENDF/B-VII.1 Decay Sublibrary Links

Overview of the ENDF/B-VII.1 decay sublibrary contents. Click for a larger view.

• Data files for the ENDF/B-VII.1 Decay Sublibrary
• Release notes for the ENDF/B-VII.1 Decay Sublibrary
• List of isotopes contained in the decay sublibrary

The ENDF/B-VII.1 sublibrary is based on decay data in the Evaluated Nuclear Structure Data File (ENSDF), translated into the ENDF-6 format. The data in ENSDF is continuously being updated and re-evaluated, with each mass chain revisited, on average, every 7 years. Thus, a significant amount of the data incorporated in ENDF/B-VII.0 has been re-evaluated in ENDF/B-VII.1. Included in the re-evaluation are 1927 new decay data sets published since the release of ENDF/B-VII.0. For nuclei located far from the valley of stability, often knowledge of a complete decay scheme is lacking. In these cases, basic information on the decay properties (T_1/2, Q value, decay modes) was taken from the latest version of the Nuclear Wallet Cards (2011). For 344 nuclei in the neutron-rich region with significant fission fragment yields, incomplete information on the decay is supplemented with state-of-the-art theoretical calculations from the Cascading Gamma Multiplicity (CGM) model.

The new ENDF/B-VII.1 decay sublibrary contains data for 3,817 materials, where each material corresponds to a ground state or long-lived isomeric level. In comparison, VI.8 covered 979 materials, while VII.0 and JEFF-3.1 contain 3838 and 3852 materials, respectively. The early version of the library, VI.8, was limited to materials relevant to applications, focusing on the actinides and fission fragments. The more recent libraries have expanded to include all known nuclei across the nuclear chart. The differences between the number of materials in VII.0, VII.1 and JEFF-3.1 correspond to the number of isomeric states included in the library. JEFF-3.1 and VII.0 cover all levels (ground state and isomeric) given in the 2003 NuBase evaluation. For VII.1, we adopted the general policy not to include isomers

1. with half-lives shorter than 1 ms
2. with IT as the sole decay mode and
3. were not in VI.8.

The 1^st stipulation stems from the consideration that one millisecond is the lower limit for a half-life in beta-decay. The 2^nd condition ensures that omission of any isomers does not alter the decay path. VII.1 contains all of the isomers in VI.8. The isomers absent in VII.1 compared with VII.0 are those with 100% IT decay and lifetimes <1 ms. We expect our policy on isomers preserves the physics output and keeps the time for a computer code to solve the differential equations for applications to a minimum.

We note that the ENDF/B-VII.1 decay sublibrary is slated to be included in the next release of the ORIGEN code included in the SCALE package (https://scale.ornl.gov).

We want to ensure that ENDF/B-VII.1 provides the best possible data to our users. If you find any issues/deficiencies, please note them on the decay sublibrary issue tracker.

• Q values updated using 2011 Audi mass evaluation
• Better treatment of atomic radiation using the Evaluated Atomic Data Library; new features include K-L, K-M, K-N, La, Lb, and Lg X-rays as well as a number of average Auger electrons.
• New decay modes added; double-beta decay, beta-delayed 2-neutron emission, and other complex decays.
• More accurate EEM and ELP values from new Total Absorption Gamma-ray Spectroscopy (TAGS) measurements; such data has recently helped resolve a discrepancy in calculations of ²³⁹Pu decay heat. See figure to right.
• In terms of beta minus decay alone, nearly 300 new, high precision measurements have been published since the release of VII.0 and are now included in VII.1.
• Modeling of post-fission beta-delayed neutron spectra greatly improved using results from the Cascading Gamma Multiplicity (CGM) model.
• Quality control, both automated (using NNDC checking codes CHECKR, FIZCON and PSYCHE) and comparisons with different libraries (VI.8, JEFF).