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論文

Radioactive particles from a range of past nuclear events; Challenges posed by highly varied structure and composition

Johansen, M. P.*; Child, D. P.*; Collins, R.*; Cook, M.*; Davis, J.*; Hotchkis, M. A. C.*; Howard, D. L.*; Howell, N.*; 池田 篤史; Young, E.*

Science of the Total Environment, 842, p.156755_1 - 156755_11, 2022/10

 被引用回数:3 パーセンタイル:45.99(Environmental Sciences)

While they have appeared only recently in earth's history, radioactive particles from anthropogenic sources are widespread in global environments and present radiological harm potentials to living organisms. Here we compare a varied set of particles from past nuclear fission and non-fission sources in Australia of highly diverse magnitudes, release modes, and environments. Numerous radioactive particles persist in soils 60 + years after their release events. Particles can be distinguished by their Ca/Fe and Si/Fe elemental ratios, which in this study range over orders of magnitude and reflect the materials available during their individual formation events. The particles from nuclear testing have dominant $$^{239+240}$$Pu activity concentrations, relative to $$^{90}$$Sr and $$^{137}$$Cs, which increases long-term radiological hazard from alpha emissions if inhaled or ingested, and contrasts with particles from nuclear power accidents (e.g., Fukushima). Internal fracturing is more prevalent than previously reported, and fracturing is greater in Ca-rich vs. Si-dominated matrices.

論文

Neutron-hole states in $$^{131}$$Sn and spin-orbit splitting in neutron-rich nuclei

Orlandi, R.; Pain, S. D.*; Ahn, S.*; Jungclaus, A.*; Schmitt, K. T.*; Bardayan, D. W.*; Catford, W. N.*; Chapman, R.*; Chipps, K. A.*; Cizewski, J. A.*; et al.

Physics Letters B, 785, p.615 - 620, 2018/10

 被引用回数:7 パーセンタイル:53.93(Astronomy & Astrophysics)

Low-lying neutron-hole states in $$^{131}$$Sn were populated via the $$^{132}$$Sn(d,t) reaction at Oak Ridge National Laboratory. The triton angular distributions were compared to DWBA calculations and revealed spectroscopic factors compatible with a single-hole nature of the states populated. The data permit to determine the spin-orbit splitting of the strongly bound $$d_{3/2}$$ and $$d_{5/2}$$ neutron orbits below the shell gap, which was compared to the splitting of the weakly bound 3$$p$$ and 2$$f$$ orbits above the gap. The comparison revealed a smaller energy splitting of the 3$$p$$ orbits. All splittings were reproduced using Woods-Saxon calculations, and the lower splitting of the 3$$p$$ orbits was explained to arise from the large radial extent of the wavefunction and small value of the amplitude at the surface. This result is important to understand at a fundamental level the spin-orbit interaction, and its effects on neutron-rich nuclei.

論文

Beta-delayed proton emission from $$^{20}$$Mg

Lund, M. V.*; Andreyev, A. N.; Borge, M. J. G.*; Cederk$"a$ll, J.*; De Witte, H.*; Fraile, L. M.*; Fynbo, H. O. U.*; Greenlees, P. T.*; Harkness-Brennan, L. J.*; Howard, A. M.*; et al.

European Physical Journal A, 52(10), p.304_1 - 304_14, 2016/10

 被引用回数:16 パーセンタイル:75.97(Physics, Nuclear)

Beta-delayed proton emission from $$^{20}$$Mg has been measured at ISOLDE, CERN, with the ISOLDE Decay Station setup including both charged-particle and $$gamma$$-ray detection capabilities. A total of 27 delayed proton branches were measured including seven so far unobserved. An updated decay scheme, including three new resonances above the proton separation energy in $$^{20}$$Na and more precise resonance energies, is presented. Beta-decay feeding to two resonances above the Isobaric Analogue State in $$^{20}$$Na is observed. This may allow studies of the 4032.9(2.4) keV resonance in $$^{19}$$Ne through the beta decay of $$^{20}$$Mg, which is important for the astrophysically relevant reaction $$^{15}$$O($$alpha$$,$$gamma$$)$$^{19}$$Ne. Beta-delayed protons were used to obtain a more precise value for the half-life of $$^{20}$$Mg, 91.4(1.0) ms.

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