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論文

Evaluation of residual stress relaxation in a rolled joint by neutron diffraction

林 眞琴*; Root, J. H.*; Rogge, R. B.*; 徐 平光

Quantum Beam Science (Internet), 2(4), p.21_1 - 21_16, 2018/12

AA2018-0259.pdf:2.23MB

The rolled joint of pressure tube, consisting of three axial symmetric parts, modified SUS403 stainless steel, Zr-2.5Nb pressure tube and Inconel-718, has been examined by neutron diffraction for residual stresses. It was heat treated at 350$$^{circ}$$C for 30, 130 and 635 hours to simulate the thermal aging of the rolled joint over the lifetime of the advanced thermal reactor at 288$$^{circ}$$C for 1, 5 and 30 years. The crystal lattice strains at various locations in the rolled joint before and after the aging treatments were measured by neutron diffraction and the residual stress distribution in the rolled joint was evaluated by using the Kroner elastic model and the generalized Hooke's law. In the crimp region of the rolled joint, it was found that the aging treatment had weak effect on the residual stresses in the Inconel and the SUS403. In the non-aged Zr-2.5Nb, the highest residual stresses were found near its interface with the SUS430. In the Zr-2.5Nb in the crimp region near its interface with the SUS430, the average compressive axial stress was -440 MPa, having no evident change during the long-time aging. In the Zr-2.5Nb outside closest to the crimp region, the tensile axial and hoop stresses were relieved during the 30 hours aging. The hoop stresses in the crimp region evolved from an average tensile stress of 80 MPa to an average compressive stress of 230 MPa after the 635 hours aging, suggesting that the rolled joint had a good long-term sealing ability against the leakage of high temperature water.

論文

Type II shell evolution in $$A=70$$ isobars from the $$N geq 40$$ island of inversion

Morales, A. I.*; Benzoni, G.*; Watanabe, H.*; 角田 佑介*; Otsuka, T.*; 西村 俊二*; Browne, F.*; Daido, R.*; Doornenbal, P.*; Fang, Y.*; et al.

Physics Letters B, 765, p.328 - 333, 2017/02

 被引用回数:31 パーセンタイル:92.19(Astronomy & Astrophysics)

The level schemes of neutron-rich isotopes $$^{70}$$Co and $$^{70}$$Ni were populated in the $$beta$$ decay of $$^{70}$$Fe and studied using $$beta$$-delayed $$gamma$$-ray spectroscopy of the $$beta$$ decay, at the RIBF in RIKEN, Japan. The experimental results were compared to state-of-the-art shell-model calculations, and indicate a dominance of prolate deformation in the low-lying states, coexisting with spherical states. The $$beta$$ decay of the $$A=70$$ isobars is shown to progress in accordance to a new type of shell evolution, the so-called Type II, which involves many particle-hole excitations across energy gaps.

論文

Low-lying excitations in $$^{72}$$Ni

Morales, A. I.*; Benzoni, G.*; Watanabe, H.*; 西村 俊二*; Browne, F.*; Daido, R.*; Doornenbal, P.*; Fang, Y.*; Lorusso, G.*; Patel, Z.*; et al.

Physical Review C, 93(3), p.034328_1 - 034328_14, 2016/03

 被引用回数:25 パーセンタイル:85.51(Physics, Nuclear)

Low-lying excited states in $$^{72}$$Ni have been investigated at RIKEN by studying the $$beta$$ decay of $$^{72}$$Co to $$^{72}$$Ni. $$^{72}$$Co was separated with BigRIPS, implanted into the WaS3ABi Silicon array, and the $$gamma$$ ray measured using the EURICA $$gamma$$ spectrometer. From the analysis, 60 new $$gamma$$-ray transitions and 21 new levels in $$^{72}$$Ni were observed. The new experimental information is compared to shell-model calculations which include neutron excitation across the $$fpg$$ shell. The calculations reproduce rather well the observed states, implying that a clear understanding of these low-lying excitations has been achieved.

論文

Decay properties of $$^{68,69,70}$$Mn; Probing collectivity up to N=44 in Fe isotopic chain

Benzoni, G.*; Morales, A. I.*; Watanabe, H.*; 西村 俊二*; Coraggio, L.*; Itaco, N.*; Gargano, A.*; Browne, F.*; Daido, R.*; Doornenbal, P.*; et al.

Physics Letters B, 751, p.107 - 112, 2015/12

 被引用回数:20 パーセンタイル:78.31(Astronomy & Astrophysics)

The $$beta$$ decays of $$^{68,69,70}$$Mn have been measured at the RIBF facility at RIKEN using the EURICA $$gamma$$ spectrometer combined with an active stopper consisting of a stack of Si detectors. Half-lives and $$beta$$-delayed neutron emission probabilities have been extracted for these decays, together with first experimental information on excited states populated in $$^{69,70}$$Fe. The data indicate a continuously increasing deformation for Fe isotopes up to A=70, and interpreted to be due to the interplay between quadrupole correlation of specific neutron orbitals and the monopole component of the proton-neutron interaction.

論文

$$beta$$-decay half-lives of 110 neutron-rich nuclei across the $$N$$=82 shell gap; Implications for the mechanism and universality of the astrophysical $$r$$ process

Lorusso, G.*; 西村 俊二*; Xu, Z. Y.*; Jungclaus, A.*; Shimizu, Y.*; Simpson, G. S.*; S$"o$derstr$"o$m, P.-A.*; Watanabe, H.*; Browne, F.*; Doornenbal, P.*; et al.

Physical Review Letters, 114(19), p.192501_1 - 192501_7, 2015/05

 被引用回数:149 パーセンタイル:97.96(Physics, Multidisciplinary)

The $$beta$$-decay half-lives of 110 neutron-rich isotopes of the elements from Rb to Sn were measured at the RIBF Facility at RIKEN, Japan. The new data demonstrate the persistence of shell structure far from stability and have direct implications for the $$r$$-process calculations. In particular, the new half-lives have a global impact on the calculated $$r$$-process elemental abundances, and alleviate the underproduction of isotopes just above and below the A=130 peak, which in the past required the introduction of shell structure modifications. Reaction-network calculations based on the new data reinforce the notion that the r-process abundance pattern may result from the freeze-out of a (n,$$gamma$$)$$_leftarrow^{rightarrow}$$($$gamma$$,n) equilibrium.

論文

Monopole-driven shell evolution below the doubly magic nucleus $$^{132}$$Sn explored with the long-lived isomer in $$^{126}$$Pd

Watanabe, H.*; Lorusso, G.*; 西村 俊二*; Otsuka, T.*; Ogawa, K.*; Xu, Z. Y.*; 炭竃 聡之*; S$"o$derstr$"o$m, P.-A.*; Doornenbal, P.*; Li, Z.*; et al.

Physical Review Letters, 113(4), p.042502_1 - 042502_6, 2014/07

 被引用回数:24 パーセンタイル:77.04(Physics, Multidisciplinary)

A new isomer with a half-life of 23.0(8) ms has been identified in $$^{126}$$Pd at 2406 keV excitation. The proposed spin and parity configuration is 10$$^{+}$$, with maximally aligned configuration of two $$h$$$$_{11/2}$$ neutron hole. $$beta$$-decay from the long-lived isomer was also observed to populated excited states at high spins in $$^{126}$$Ag. The small energy difference between the 10$$^{+}$$ and 7$$^{-}$$ isomers in $$^{126}$$Pd was interpreted in the frame of the monopole shift of the 1$$h$$$$_{11/2}$$ neutron orbit. The effects of the monopole interaction on the evolution of single-neutron energies below $$^{132}$$Sn are discussed in terms of central and tensor forces.

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