Shell structure of the neutron-rich isotopes Co

Lokotko, T.*; Leblond, S.*; Lee, J.*; Doornenbal, P.*; Obertelli, A.*; Poves, A.*; Nowacki, F.*; Ogata, Kazuyuki*; Yoshida, Kazuki; Authelet, G.*; et al.

Physical Review C, 101(3), p.034314_1 - 034314_7, 2020/03

https://doi.org/10.1103/PhysRevC.101.034314

The structures of the neutron-rich Co isotopes were investigated via () knockout reactions at the Radioactive Isotope Beam Factory, RIKEN. Level schemes were reconstructed using the coincidence technique, with tentative spin-parity assignments based on the measured inclusive and exclusive cross sections. Comparison with shell-model calculations suggests coexistence of spherical and deformed shapes at low excitation energies in the Co isotopes.

Nagasaki sediments reveal that long-term fate of plutonium is controlled by select organic matter moieties

Lin, P.*; Xu, C.*; Kaplan, D. I.*; Chen, H.*; Yeager, C. M.*; Xing, W.*; Sun, L.*; Schwehr, K. A.*; Yamazaki, Hideo*; Kokubu, Yoko; et al.

Science of the Total Environment, 678, p.409 - 418, 2019/08

https://doi.org/10.1016/j.scitotenv.2019.04.375

Nagasaki sediments containing bomb-derived Pu provided a unique opportunity to explore the long term geochemical behavior of Pu. Through a combination of selective extractions and molecular characterization via electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry, we determined that 55 3% of the Pu was preferentially associated with more persistent organic matter compounds in Nagasaki sediments, particularly those natural organic matter (NOM) stabilized by Fe oxides. Other organic matter compounds served as a secondary sink of these Pu (31 2% on average), and less than 20% of the Pu was immobilized by inorganic mineral particles. While present long-term disposal and environmental remediation modeling assume that solubility limits and sorption to mineral surfaces control Pu subsurface mobility, our observations suggest that NOM undoubtedly plays an important role in sequestering Pu. Ignoring the role of NOM in controlling Pu fate and transport is not justified in most environmental systems.

Nuclear structure of Ni from the (,) reaction

Elekes, Z.*; Kripk, *; Sohler, D.*; Sieja, K.*; Ogata, Kazuyuki*; Yoshida, Kazuki; Doornenbal, P.*; Obertelli, A.*; Authelet, G.*; Baba, Hidetada*; et al.

Physical Review C, 99(1), p.014312_1 - 014312_7, 2019/01

https://doi.org/10.1103/PhysRevC.99.014312

The nuclear structure of the Ni nucleus was investigated by (,) reaction using a NaI(Tl) array to detect the deexciting prompt rays. A new transition with an energy of 2227 keV was identified by and coincidences. Our shell-model calculations using the Lenzi, Nowacki, Poves, and Sieja interaction produced good candidates for the experimental proton hole states in the observed energy region, and the theoretical cross sections showed good agreement with the experimental values. Although we could not assign all the experimental states to the theoretical ones unambiguously, the results are consistent with a reasonably large Z = 28 shell gap for nickel isotopes in accordance with previous studies.

Shell evolution beyond =28 and =50; Spectroscopy of Zn

Shand, C. M.*; Podolyk, Zs.*; Grska, M.*; Doornenbal, P.*; Obertelli, A.*; Nowacki, F.*; Otsuka, T.*; Sieja, K.*; Tostevin, J. A.*; Tsunoda, T.*; et al.

Physics Letters B, 773, p.492 - 497, 2017/10

https://doi.org/10.1016/j.physletb.2017.09.001

decay of unbound neutron-hole states in Sn

Vaquero, V.*; Jungclaus, A.*; Doornenbal, P.*; Wimmer, K.*; Gargano, A.*; Tostevin, J. A.*; Chen, S.*; Ncher, E.*; Sahin, E.*; Shiga, Yoshiaki*; et al.

Physical Review Letters, 118(20), p.202502_1 - 202502_5, 2017/05

https://doi.org/10.1103/PhysRevLett.118.202502

On-site background measurements for the J-PARC E56 experiment; A Search for the sterile neutrino at J-PARC MLF

Ajimura, Shuhei*; Bezerra, T. J. C.*; Chauveau, E.*; Enomoto, T.*; Furuta, Hisataka*; Harada, Masahide; Hasegawa, Shoichi; Hiraiwa, T.*; Igarashi, Yoichi*; Iwai, Eito*; et al.

Progress of Theoretical and Experimental Physics (Internet), 2015(6), p.063C01_1 - 063C01_19, 2015/06

https://doi.org/10.1093/ptep/ptv078

The J-PARC E56 experiment aims to search for sterile neutrinos at the J-PARC Materials and Life Science Experimental Facility (MLF). In order to examine the feasibility of the experiment, we measured the background rates of different detector candidate sites, which are located at the third floor of the MLF, using a detector consisting of plastic scintillators with a fiducial mass of 500 kg. The gammas and neutrons induced by the beam as well as the backgrounds from the cosmic rays were measured, and the results are described in this article.

Speciation of iodine isotopes inside and outside of a contaminant plume at the Savannah River Site

Schwehr, K. A.*; Otosaka, Shigeyoshi; Merchel, S.*; Kaplan, D. I.*; Zhang, S.*; Xu, C.*; Li, H.-P.*; Ho, Y.-F.*; Yeager, C. M.*; Santschi, P. H.*; et al.

Science of the Total Environment, 497-498, p.671 - 678, 2014/11

https://doi.org/10.1016/j.scitotenv.2014.07.006

A new, accurate and simple pH-dependent solvent extraction method combined with accelerator mass spectrometry (AMS) measurement for I/I isotopes and iodine speciation (iodide, iodate, and organo-I) quantification in liquids of any ionic strength has been developed. We then validated the AMS method for activity concentration measurements with a recently developed gas chromatography mass spectrometry method for I concentrations of 1 Bq/L or higher. This technique was applied to I-contaminated groundwater from the Savannah River Site, USA, and demonstrated changes of I and I concentrations and speciation along a pH, redox potential, and organic carbon gradient. The data suggest that I/I and species distribution is strongly pH dependent. The new method can now be applied to a wide range of chemically-diverse aquatic systems, including uncontaminated environments.

Collection of lanthanides and actinides from natural waters with conventional and nanoporous sorbents

Johnson, B. E.*; Santschi, P. H.*; Chuang, C.-Y.*; Otosaka, Shigeyoshi; Addleman, R. S.*; Douglas, M.*; Rutledge, R. D.*; Chouyyok, W.*; Davidson, J. D.*; Fryxell, G. E.*; et al.

Environmental Science & Technology, 46(20), p.11251 - 11258, 2012/11

https://doi.org/10.1021/es204192r

Effective collection of trace-level lanthanides and actinides is advantageous for recovery and recycling of valuable resources, environmental remediation, chemical separations, and in situ monitoring. Using isotopic tracers, we have evaluated a number of conventional and nanoporous sorbent materials for their ability to capture and remove selected lanthanides (Ce and Eu) and actinides (Th, Pa, U, and Np) from fresh and salt water systems. In general, the nanostructured materials demonstrated a higher level of performance and consistency. Nanoporous silica surface modified with 3,4-hydroxypyridinone provided excellent collection and consistency in both river water and seawater.

Sequestration and remobilization of radioiodine (I) by soil organic matter and possible consequences of the remedial action at Savannah River Site

Xu, C.*; Miller, E. J.*; Zhang, S.*; Li, H.-P.*; Ho, Y.-F.*; Schwehr, K. A.*; Kaplan, D. I.*; Otosaka, Shigeyoshi; Roberts, K. A.*; Brinkmeyer, R.*; et al.

Environmental Science & Technology, 45(23), p.9975 - 9983, 2011/12

https://doi.org/10.1021/es201343d

In order to investigate accumulation process of iodine-129 (I) in a contaminated F-Area groundwater plume of the US Savannah River Site, soil resuspension experiments simulating surface runoff and erosion events were conducted. Results showed that 7277% of the newly-introduced iodide was irreversibly sequestered into the organic-rich soil, while the rest was transformed into colloidal and dissolved organo-iodine by the soil. Laboratory iodination of the soil indicated a preferential incorporation of inorganic iodine into soil organic matter (SOM) at acidic pH (34), except for the iodination catalyzed by lactoperoxidase, which favors more alkaline conditions. From this result, we concluded that under very acidic conditions, abiotic iodination of SOM was predominant, while under less acidic conditions (pH 5), microbial enzymatically-assisted iodination took over.

Factors controlling mobility of I and I species in an acidic groundwater plume at the Savannah River Site

Otosaka, Shigeyoshi; Schwehr, K. A.*; Kaplan, D. I.*; Roberts, K. A.*; Zhang, S.*; Xu, C.*; Li, H.-P.*; Ho, Y.-F.*; Brinkmeyer, R.*; Yeager, C. M.*; et al.

Science of the Total Environment, 409(19), p.3857 - 3865, 2011/09

https://doi.org/10.1016/j.scitotenv.2011.05.018

Spatial distributions of concentrations and speciation of radioiodine (I) and stable iodine (I) in groundwater in the vicinity of the F-area seepage basin at the U.S. Department Energy of Savannah River Site were investigated. I concentration in groundwater was 8.6 Bq/L immediately downstream of the seepage basin (well FSB-95DR), and decreased with distance from the infiltration basin. I concentration decreased similarly to that of I. Although there was no potential I source in wastes in the basin, I also showed a similar gradient to that of I. High concentrations of I or I were not detected in groundwater collected from wells located outside of the mixed waste plume of this area. The high iodide concentrations in groundwater near the basin were presumed to be caused by dissolution of iodide from soil due to gradually increasing of pH values in the last decade.