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The priority for AMPX development for FY2024 has been to support processing the ENDF/B-VIII.1 library. This includes the development to support Thermal Neutron Scattering Library, GNDS-2.1 support and AMPX maintenance, and transport libraries for SCALE 7.0.0.
The ENDF/B-VIII.1 evaluation library has seen a great growth in the thermal neutron scattering sub-library. The SCALE code system has traditionally approached CE transport by assuming that the CE library on disk represented the fully expanded cumulative probability distributions, conditional on exiting angle and marginal on exiting energy. While this is a complete description of the data, it comes at the potential cost of large amounts of on-disk storage. This approach was strained by several TSL files in ENDF/B-VIII.1, such as graphite, which contained data for a large number of Bragg edges. In the fully expanded probability distributions, this was found to be a disproportionately large fraction of the SCALE CE library.
The neutron sources at Oak Ridge National Laboratory use a wide suite of sample environment equipment to deliver extreme conditions for a number of experiments. Much of this instrumentation focuses on extremes of temperature, such as cryostats, closed-cycle refrigerators in both low and high temperature configurations, and radiant heating furnaces. When the temperature is controlled across a large range, thermal deflection effects can notably move the sample and affect its alignment in the beam. Here, we combine these sample environments with neutron imaging and machine vision to determine the motion of a representative sample with respect to the neutron beam. We find vertical sample displacement on the order of 1–2 mm and horizontal displacement that varies from near-negligible to 1.2 mm. While these deflections are not relevant for some of the beamlines at the first target station at the spallation neutron source and the high flux isotope reactor, they will become critical for upcoming instrumentation at the second target station, as well as any instruments targeting sub-mm samples, as neutron sources and optics evolve to smaller and more focused beams. We discuss mitigation protocols and potential modifications to the environment to minimize the effect of misalignment due to thermal deflection.
Not provided.
Zirconium hydride (ZrHx) is a moderator material used in TRIGA and other reactors that may exist in multiple phases with varying stoichiometry, which include the δ phase and the ϵ phase. Current ENDF/B-VIII.0 ZrHx thermal scattering law (TSL) evaluations do not distinguish between phases. These sub-libraries were generated with the LEAPR module of NJOY using historic phonon spectra derived from a central force model and assume incoherent elastic scattering for both bound hydrogen and zirconium, which neglects the effects of crystal structures important for scattering from zirconium bound in ZrHx. In this work, the TSLs for hydrogen and zirconium bound in δ-ZrHx and ϵ-ZrH2 were generated from phonon spectra derived from modern ab initio lattice dynamics methods and ab initio molecular dynamics. Subsequently, TSLs for hydrogen and zirconium in ZrHx and ZrH2 were generated using the Full Law Analysis Scattering System Hub (FLASSH) code. The built-in generalized coherent elastic routine was used to generate the previously neglected elastic contribution from zirconium for this material. The present TSLs provide both a re-evaluation of the current ZrH sub-libraries and expansion of the set of TSLs available for the examination of neutrons in systems with zirconium hydride, permitting explicit treatment of δ and ϵ phases.
The alphas sublibrary aims to describe nuclear reactions between incident alpha particles and different nuclei. For ENDF/B-VIII.1, the LLNL ECPL evaluation for 6Li, and the JENDL-based NNL evaluations of 9 Be and 16,17 O were adopted. Also, there were minor fixes done to 4 He.
The atomic relaxation sublibrary aims to describe atomic binding energies. For ENDF/B-VIII.1 we adopted the EPICS2023 EADL evaluations.
The decay sublibrary aims to describe all known spontaneous decays and branching ratios for all nuclei across the nuclide chart. ENDF/B-VIII.1 remains unchanged from ENDF/B-VIII.0 for the decay sublibrary.
The deuterons sublibrary aims to describe nuclear reactions between incident deuteron particles and different nuclei. For ENDF/B-VIII.1, we adopted additions and corrections to the ENDF/B-VIII.0 d+t file, as well as new LANL evaluation updates for 3 He and 6 Li.
The electrons sublibrary aims to describe electron-atomic cross section data, corresponding to the interaction between electrons and the different atoms. For ENDF/B-VIII.1 we adopted the EPICS2023 EEDL evaluations.
The photonuclear sublibrary aims to describe nuclear reactions between incident gamma particles and different nuclei. For ENDF/B-VIII.1, we adopted around 200 evaluations from the IAEA Coordinated Research Project (CRP) on photonuclear data while, for a few select mission-critical materials, evaluations from ENDF/B-VIII.0 were maintained. Additionally, many fixes to many files were implemented. Finally, ENDF/B-VIII.1 includes a new photonuclear file, 242 Pu, which was adopted from JENDL-5.0.
The Helium-3 (Helions) sublibrary aims to describe nuclear reactions between incident 3 He particles and different nuclei. For ENDF/B-VIII.1, we adopted a new 4He evaluation from the INDEN collaboration and the LLNL ECPL evaluation for 7 Li.
The neutrons sublibrary aims to describe nuclear reactions between incident neutron particles and different nuclei. For ENDF/B-VIII.1, many neutron files were re-evaluated or received major changes. A new 239Pu evaluation was jointly-produced by IAEA, LANL, LLNL and ORNL bringing important updates to fission neutron multiplicity, Prompt Fission Neutron Spectrum, resonance and fast regions. Around one third of the new neutron evaluations were performed as part of the INDEN collaboration, including 16,18 O, 19 F, 28,29,30 Si, 63,65 Cu, 50,51,52,53,54 Cr, 55 Mn, 54,56,57 Fe, 139 La, 233,235,238 U, 240,241 Pu. Important non-INDEN evaluations include 234,236 U, 206,207,208 Pb, 181 Ta, 88 Sr, 140,142 Ce, Pt and Dy isotopes, and many others. Also, dosimetry reactions from IRDFF-II were adopted for many materials.
The neutron-induced fission yields (NFY) sublibray aims to describe fission yields in neutron-induced reactions. For ENDF/B-VIII.1, there were no new fission yields complete evaluations. However, an important fix the 241 Pu NFY file was implemented, solving a long-standing anomalous discontinuity issue accidentally introduced in ENDF/B-VI.2, decades ago. Additionally, many erroneously large uncertainties, present in NFY from ENDF/B-VIII.0, were corrected.
The photo-atomic sublibrary aims to describe atomic photon cross section data, corresponding to the interaction between photons and the different atoms. For ENDF/B-VIII.1 we adopted the EPICS2023 EPDL evaluations.
The protons sublibrary aims to describe nuclear reactions between incident proton particles and different nuclei. For ENDF/B-VIII.1, compared to ENDF/B-VIII.0, there were only evaluation updates for 4 He.
The spontaneous fission yields (SFY) sublibray aims to describe fission yields that happen spontaneous, without any incident particle. For ENDF/B-VIII.1, there were no new fission yields complete evaluations. However, many erroneously large uncertainties, present in both SFY from ENDF/B-VIII.0, were corrected.
The neutron standards sublibrary describes specific reaction cross sections, in a limited range, that are so well-known that they are used as ratios or references in other measurements. ENDF/B-VIII.1 remains unchanged from ENDF/B-VIII.0 for the neutron standards sublibrary