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DOE OSTI2013

Nuclear Data Sheets for A = 89

The evaluated experimental data are presented for 14 known nuclides of mass 89 (Ge, As, Se, Br, Kr, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh). New data on high–spin excitations are available for {sup 89}Kr, {sup 89}Rb, {sup 89}Sr, {sup 89}Tc and {sup 89}Ru, including a superdeformed structure in {sup 89}Tc. Fluorescence studies in {sup 89}Y have revealed a large number of new levels in 7–11 MeV range. New two–neutron transfer data are available for {sup 89}Zr. New direct and precise measurement of atomic masses of {sup 89}Se, {sup 89}Br, 89{sup K}r, {sup 89}Rb, {sup 89}Mo and {sup 89}Tc have greatly improved the Q value landscape in this mass region. This work supersedes previous A=89 evaluation published in 1998Si31, and also the older ones 1989Si20, 1975Ko21, and M.W. Johns et al., Nuclear Data Tables A 8, 373 (1970). In spite of extensive experimental work on the isobaric nuclei of this mass chain several deficiencies remain. The identification of {sup 89}Rh isotope remains unconfirmed. The half–lives of ground states of {sup 89}Ge, {sup 89}As and {sup 89}Rh have not been measured, only the lower limits are estimated from time–of–flight in a reaction and experimental arrangement, where produced and identified. The decay schemes of {sup 89}Ge, {sup 89}As, {sup 89}Se, {sup 89}Ru and {sup 89}Rh are not known, and those for {sup 89}Tc and {sup 89}Mo are incomplete. High–lying (neutron unbound) levels in {sup 89}Kr, expected to be populated in the decay of {sup 89}Br, have not been investigated. The spins and parities for levels in {sup 89}Kr are largely unassigned, while for {sup 89}Tc and {sup 89}Ru, only few low–spin excitations are established. For {sup 89}Rb, little information is available for high–spin structures. Detailed gamma–ray data are available for {sup 88}Sr(n,γ){sup 89}Sr reaction, but most of these γ rays remain unassigned in a level scheme. Excited state data are nonexistent for {sup 89}Ge, {sup 89}As, {sup 89}Se, {sup 89}Br and {sup 89}Rh. The {sup 89}Y and {sup 89}Zr are the most extensively studied nuclei in A=89.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2017

Fission Product Yields from 232Th, 238U, and 235U Using 14 MeV Neutrons

Neutron-induced fission yield studies using deuterium-tritium fusion-produced 14 MeV neutrons have not yet directly measured fission yields from fission products with half-lives on the order of seconds (far from the line of nuclear stability). Fundamental data of this nature are important for improving and validating the current models of the nuclear fission process. Cyclic neutron activation analysis (CNAA) was performed on three actinide targets–thorium-oxide, depleted uranium metal, and highly enriched uranium metal–at the University of Michigan's Neutron Science Laboratory (UM-NSL) using a pneumatic system and Thermo-Scientific D711 accelerator-based fusion neutron generator. This was done to measure the fission yields of short-lived fission products and to examine the differences between the delayed fission product signatures of the three actinides. The measured data were compared against previously published results for 89Kr, -90, and -92 and 138Xe, -139, and -140. The average percent deviation of the measured values from the Evaluated Nuclear Data Files VII.1 (ENDF/B-VII.1) for thorium, depleted-uranium, and highly-enriched uranium were -10.2%, 4.5%, and -12.9%, respectively. In addition to the measurements of the six known fission products, 23 new fission yield measurements from 84As to 146La are presented.

Pierson, Bruce D.↗

DOE OSTI2017

Benchmarking of activation rate in special core in LR-0 reactor

The experiments focused on the determination of activation reaction rates of selected IRDFF materials activated in a well-defined special core assembled in the LR-0 reactor are presented in the paper. The used core is designed and verified for IRDFF library testing by reactivity characterization, fission rates distribution and also neutron spectra measurement at the center of the core. {sup 23}Na(n,2n), {sup 75}As(n,2n), {sup 89}Y(n,2n) and {sup 90}Zr(n,2n) reaction cross sections were measured in this special core. The presented neutron cross sections were derived from experimentally determined reaction rates of irradiated samples of NaF, As{sub 2}O{sub 3}, Y{sub 2}O{sub 3}, and ZrO{sub 2}. These reaction rates are derived from gamma activities of the activation products of studied activation reactions. Net Peak Areas (NPA) of photons accompanying decay were measured using a semiconductor High Purity Germanium (HPGe) detector. Despite the fact that mentioned reactions have a threshold above 10 MeV, where the neutron spectrum in the special LR-0 core is nearly undistinguishable from {sup 235}U prompt fission neutron spectrum, the measured integral cross sections averaged in LR-0 spectrum were corrected for spectral shift. The obtained values of {sup 235}U spectral average cross section are: (3.84 ± 0.19) μb for {sup 23}Na(n,2n); (0.320 ± 0.015) mb for {sup 75}As(n,2n); (0.171 ± 0.006) mb for {sup 89}Y(n,2n); (0.107 ± 0.005) mb for {sup 90}Zr(n,2n). (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗