Nuclear Data Sheets最新文献

The absolute γ-ray branching ratios (emission probabilities) for 19 prominent peaks in the α decay of ²³³U are reported with energies ranging from 97 to 366 keV. The branching ratios were obtained from α-γ coincidence measurements, normalized to the α singles. The high-purity ²³³U material ($>99.98\text{\%}$) was separated from its decay products before preparation of a 4.74-$\text{mg}/{\text{cm}}^2$ uranyl nitrate foil with a 6-mm diameter. This is the first report on the absolute normalization of the branching ratios since 1984 and it is the only measure by α-γ coincidences, where the $\alpha \text{-}\gamma /\alpha$ ratio removes several potential systematic biases. Overall, the results are consistent with the adopted literature and they validate the quantities most relevant to the non-destructive assay of fissile ²³³U material, which is relevant to the thorium fuel cycle and associated safeguards.

The Fusion Evaluated Nuclear Data Library (FENDL) is a comprehensive and validated collection of nuclear cross section data coordinated by the International Atomic Energy Agency (IAEA) Nuclear Data Section (NDS). FENDL assembles the best nuclear data for fusion applications selected from available nuclear data libraries and has been under development for decades. FENDL contains sub-libraries for incident neutron, proton, and deuteron cross sections including general purpose and activation files used for particle transport and nuclide inventory calculations.

In this work, we describe the history, selection of evaluations for the various sub-libraries (neutron, proton, deuteron) with the focus on transport and reactor dosimetry applications, the processing of the nuclear data for application codes (e.g. MCNP), and the development of the TENDL-2017 library which is the currently recommended activation library for FENDL. We briefly describe the IAEA IRDFF library as the recommended library for dosimetry fusion applications. We also present work on validation of the neutron sub-library using a variety of fusion relevant computational and experimental benchmarks using the MCNP transport code and ACE-formatted cross section libraries. A variety of cross section libraries are used for the validation work including FENDL-2.1, FENDL-3.1d, FENDL-3.2, ENDF/B-VIII.0, and JEFF-3.2 with the emphasis on the FENDL libraries.

The results of the validation using computational benchmarks showed generally good agreement among the tested neutron cross section libraries for neutron flux, nuclear heating, and primary displacement damage (dpa). Gas production (H/He) in structural materials showed substantial differences to the reference FENDL-2.1 library. The results of the experimental validation showed that the performance of FENDL-3.2b is at least as good and in most cases better than FENDL-2.1.

Future work will consider improved evaluations developed by the International Nuclear Data Evaluation Network (INDEN) for materials such as O, Cu, W, Li, B, and F. Additionally, work will need to be done to investigate differences in gas production in structural materials. Covariance matrices will need to be developed or updated as availability of consistent and comprehensive uncertainty information will be needed as fusion technology and facility construction matures. Finally, additional validation work for high energy neutrons, protons and deuterons, as well as validation work for the activation library will be needed.

Surrogate reactions are a powerful tool to access neutron-induced reaction cross sections of short-lived nuclei. However, to infer neutron-induced reaction cross sections from measured deexcitation probabilities requires a consistent and rigorous theoretical framework describing both charged-particle and neutron-induced reactions. This work presents the first practical application of the new approach developed in O. Bouland, Phys. Rev. C 100, 064611 (2019) to Pu fissile isotopes, ^{237,238,240,242,244}Pu*. Average neutron-induced reaction cross sections and deexcitation probabilities measured in surrogate reactions are simultaneously analyzed with an efficient Monte Carlo $R$-matrix-extended theory algorithm using a unique set of nuclear-structure parameters to describe both observables. Fission probabilities allow one to estimate fission-barrier heights, not otherwise accessible in fissile isotopes. The theoretical framework is here extended to model 'giant' resonance structures observed in the fission probabilities of some nuclides. A careful study of the impact of the uncertainties on nuclear parameters and on the populated compound system angular distribution has been carried out. This study raises questions on the normalization of some fission probabilities measured in the 70's in ($t,p$) reactions, that could not have been pointed out without the use of the here-presented complex technique. This finding is especially important for the peculiar ²⁴⁰Pu* system. In addition, our study reveals for the ²³⁷Pu* compound system a 10 to 30 % too high value of the only-performed low-energy neutron-induced fission cross section measurement (Gerasimov et al., JINR-E–3-97-213 (1997)) and, subsequently of the evaluated fission cross section below 50 keV for the ²³⁶Pu.

Evaluated data are presented for 11 known $A=222$ nuclides (Bi, Po, At, Rn, Fr, Ra, Ac, Th, Pa, U, and Np), and relevant J^π and T_1/2 data for $A=226$ nuclei decaying by α-decay to $A=222$ nuclei. For ²²²Bi, only the isotopic identification is established with no measurement of its half-life. For ²²²Po, ²²²At, ²²²Fr, ²²²U, and ²²²Np, data are available only for the ground states, with static magnetic dipole and electric quadrupole moments, and charge radius measurements for the ²²²Fr ground state. For ²²²Ac and ²²²Pa, two low-lying levels are known from ²²⁶Pa α decay, and ²²⁶Np decay, respectively, but with no information about J^π assignments and γ decays of these levels. For ²²²Pa, a long-lived isomeric state is known, decaying dominantly by α decay. ²²²Rn, ²²²Ra, and ²²²Th have been investigated in detail, the low-spin states by α decay and the high-spin studies of ground-state and octupole bands by in-beam γ-ray studies for all the three nuclei, as well as by Coulomb excitation for ²²²Rn and ²²²Ra. Low-spin levels in ²²²Ra have been investigated also through the ${\beta }^{-}$ decay of ²²²Fr. Half-lives of the excited states are known for 7 levels in ²²²Rn, 12 levels in ²²²Ra, and 3 levels in ²²²Th. Octupole deformations, with the presence of alternating-parity bands up to (16⁺) and (${21}^{-}$) in ²²²Rn, (20⁺) and (${19}^{-}$) in ²²²Ra, and (26⁺) and (${25}^{-}$) in ²²²Th, and with interband E1 transitions, have been established in these three nuclei. The present evaluation supersedes the previous $A=222$ ENSDF evaluations: (2011Si24), (1996El01), (1987El06) and (1977To14).

Evaluated nuclear structure and decay data for all nuclei with mass number $A=200$ (²⁰⁰Os, ²⁰⁰Ir, ²⁰⁰Pt, ²⁰⁰Au, ²⁰⁰Hg, ²⁰⁰Tl, ²⁰⁰Pb, ²⁰⁰Bi, ²⁰⁰Po, ²⁰⁰At, ²⁰⁰Rn, and ²⁰⁰Fr), are presented. All available experimental data are compiled and evaluated, and best values for level and γ-ray energies, quantum numbers, lifetimes, γ-ray intensities and transition probabilities, as well as other nuclear properties, are recommended. Inconsistencies and discrepancies that exist in the literature are discussed. A number of computer codes (https://www-nds.iaea.org/public/ensdf_pgm/) developed by members of the NSDD network were used during the evaluation process. This work supersedes the earlier evaluation by F.G. Kondev and S. Lalkovski (2007Ko42), published in Nuclear Data Sheets 108, 1471 (2007).

Experimental nuclear spectroscopic data are compiled and evaluated for 17 known nuclides of mass 167 (Sm, Eu, Gd, Tb, Dy, Ho, Er Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt), 23 years after the previous full evaluation by 2000Ba65. Detailed information is presented for each reaction and decay experiment. Combining all the available data, recommended values are provided for energies, spins and parities, and half-lives of levels, with energies, branching ratios and multipolarities of γ radiations, and characteristics of β and α radiations in radioactive decays. The α decays of A=171 nuclei to A=167 daughters are included in this work, while for α decays of A=167 nuclei to A=163 daughters, consult Nuclear Data Sheets (2010Re03) or the ENSDF database for A=163. ¹⁶⁷Er, ¹⁶⁷Tm, ¹⁶⁷Yb, ¹⁶⁷Lu and ¹⁶⁷Ta are among the most extensively studied nuclides via decay and high-spin gamma-ray spectroscopy measurements, followed by ¹⁶⁷Ho, ¹⁶⁷Hf, ¹⁶⁷W, and ¹⁶⁷Os. Information for excited states in ¹⁶⁷Dy, ¹⁶⁷Re, and ¹⁶⁷Ir are limited; no excited states have yet been identified in ¹⁶⁷Sm, ¹⁶⁷Eu, ¹⁶⁷Gd, ¹⁶⁷Tb and ¹⁶⁷Pt, with the ground-state half-life of ¹⁶⁷Sm remaining unknown. This work supersedes the earlier evaluation of A=167 nuclei by 2000Ba65.