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Journal Articles

Improvement of plant reliability based on combining of prediction and inspection of crack growth due to intergranular stress corrosion cracking

Uchida, Shunsuke; Chimi, Yasuhiro; Kasahara, Shigeki; Hanawa, Satoshi; Okada, Hidetoshi*; Naito, Masanori*; Kojima, Masayoshi*; Kikura, Hiroshige*; Lister, D. H.*

Nuclear Engineering and Design, 341, p.112 - 123, 2019/01

 Times Cited Count:5 Percentile:49.54(Nuclear Science & Technology)

Improvement of plant reliability based on reliability-centered-maintenance (RCM) is going to be undertaken in NPPs. RCM is supported by risk-based maintenance (RBM). The combination of prediction and inspection is one of the key issues to promote RBM. Early prediction of IGSCC occurrence and its propagation should be confirmed throughout the entire plant systems which should be accomplished by inspections at the target locations followed by timely application of suitable countermeasures. From the inspections, accumulated data will be applied to confirm the accuracy of the code, to tune some uncertainties of the key data for prediction, and then, to increase their accuracy. The synergetic effects of prediction and inspection on application of effective and suitable countermeasures are expected. In the paper, the procedures for the combination of prediction and inspection are introduced.

Journal Articles

Stability and synthesis of superheavy elements; Fighting the battle against fission - Example of $$^{254}$$No

Lopez-Martens, A.*; Henning, G.*; Khoo, T. L.*; Seweryniak, D.*; Alcorta, M.*; Asai, Masato; Back, B. B.*; Bertone, P. F.*; Boilley, D.*; Carpenter, M. P.*; et al.

EPJ Web of Conferences, 131, p.03001_1 - 03001_6, 2016/12

 Times Cited Count:1 Percentile:44

Fission barrier height and its angular-momentum dependence have been measured for the first time in the nucleus with the atomic number greater than 100. The entry distribution method, which can determine the excitation energy at which fission starts to dominate the decay process, was applied to $$^{254}$$No. The fission barrier of $$^{254}$$No was found to be 6.6 MeV at zero spin, indicating that the $$^{254}$$No is strongly stabilized by the nuclear shell effects.

Journal Articles

Population and decay of a $$K^{pi}$$ = 8$$^{-}$$ two-quasineutron isomer in $$^{244}$$Pu

Hota, S.*; Tandel, S.*; Chowdhury, P.*; Ahmad, I.*; Carpenter, M. P.*; Chiara, C. J.*; Greene, J. P.*; Hoffman, C. R.*; Jackson, E. G.*; Janssens, R. V. F.*; et al.

Physical Review C, 94(2), p.021303_1 - 021303_5, 2016/08

 Times Cited Count:6 Percentile:44.68(Physics, Nuclear)

The decay of a $$K^{pi}$$ = 8$$^{-}$$ isomer in $$^{244}$$Pu and the collective band structure populating the isomer are studied using deep inelastic excitations with $$^{47}$$Ti and $$^{208}$$Pb beams, respectively. Precise measurements of $$M1/E2$$ branching ratios in the band confirm a clean 9/2$$^-$$[734]$$_{nu}$$$$otimes$$7/2$$^+$$[624]$$_{nu}$$ for the isomer, validating the systematics of K$$^{pi}$$ = 8$$^{-}$$ two-quasineutron isomers observed in even-$$Z$$, $$N$$ = 150 isotones. These isomers around the deformed shell gap at $$N$$ = 152 provide critical benchmarks for theoretical predictions of single-particle energies in this gateway region to superheavy nuclei.

Journal Articles

Corrosion of structural materials and electrochemistry in high-temperature water; Relationships among water chemistry, corrosion, oxide film and electrochemical corrosion potential

Uchida, Shunsuke; Hanawa, Satoshi; Kysela, J.*; Lister, D. H.*

Power Plant Chemistry, 18(1), p.6 - 17, 2016/01

In order to establish reliable NPP operation, each plant requires its own unique optimal water chemistry control based on careful consideration of its system, materials and operational history. Electrochemistry is one of key issues that determine corrosion related problems, e.g., FAC. Based on the relationships among ECP, metal surface conditions and exposure time, a model to evaluate ECP and corrosion rate of steel was developed by coupling an electrochemical model and an oxide layer growth model. Major conclusions are as follows. (1) The effects of water chemistry improvement and mass transfer coefficients due to local flow velocity on FAC wall thinning rate and ECP could be evaluated with the proposed model. (2) The effects of H$$_{2}$$O$$_{2}$$ and O$$_{2}$$ concentrations on ECP were evaluated with the model. Exposure time dependent ECPs were also explained as the effects of oxide film growth on the specimens. (3) Decreases in ECP due to neutron exposure were explained by radiation-induced diffusion in the oxide layers.

Journal Articles

Fission barrier of superheavy nuclei and persistence of shell effects at high spin; Cases of $$^{254}$$No and $$^{220}$$Th

Henning, G.*; Khoo, T. L.*; Lopez-Martens, A.*; Seweryniak, D.*; Alcorta, M.*; Asai, Masato; Back, B. B.*; Bertone, P. F.*; Boilley, D.*; Carpenter, M. P.*; et al.

Physical Review Letters, 113(26), p.262505_1 - 262505_6, 2014/12

 Times Cited Count:34 Percentile:83.26(Physics, Multidisciplinary)

Fission barrier heights of a shell-stabilized superheavy nucleus $$^{254}$$No have been determined as a function of spin up to 19$$hbar$$ through the measured distribution of entry points of $$gamma$$ deexcitations in the excitation energy vs. spin plane. The fission barrier height of $$^{254}$$No was determined to be 6.0 MeV at spin 15$$hbar$$, and 6.6 MeV at spin 0$$hbar$$ by extrapolation. This demonstrates that the shell effect actually enlarges the fission barrier in such heavy nuclei and keeps the barrier high even at high spin.

Journal Articles

Exploring the stability of super heavy elements; First measurement of the fission barrier of $$^{254}$$No

Henning, G.*; Lopez-Martens, A.*; Khoo, T. L.*; Seweryniak, D.*; Alcorta, M.*; Asai, Masato; Back, B. B.*; Bertone, P. F.*; Boilley, D.*; Carpenter, M. P.*; et al.

EPJ Web of Conferences, 66, p.02046_1 - 02046_8, 2014/03

 Times Cited Count:3 Percentile:70.01

Fission barrier heights of $$^{254}$$No have been determined through the entry distribution method. The entry distribution is the initial distribution of excitation energy and spin from which the $$gamma$$ deexcitation starts in the fusion-evaporation reaction. The initial distribution is extracted from measured $$gamma$$-ray multiplicity and total $$gamma$$-ray energy. This paper describes the details of the entry distribution method, and reports the first determination of the fission barrier heights of $$^{254}$$No, which is the heaviest nucleus whose fission barrier has been measured.

Journal Articles

Evidence for rigid triaxial deformation at low energy in $$^{76}$$Ge

Toh, Yosuke; Chiara, C. J.*; McCutchan, E. A.*; Walters, W. B.*; Janssens, R. V. F.*; Carpenter, M. P.*; Zhu, S.*; Broda, R.*; Fornal, B.*; Kay, B. P.*; et al.

Physical Review C, 87(4), p.041304_1 - 041304_5, 2013/04

 Times Cited Count:76 Percentile:96.86(Physics, Nuclear)

Excited states of $$^{76}$$Ge have been investigated via the $$^{76}$$Ge + $$^{238}$$U reaction with $$E(^{76}$$Ge$$)=530$$ MeV by use of in-beam $$gamma$$-ray spectroscopy using the $$gamma$$ sphere array. The $$gamma$$ band was extended considerably and one new band was identified. Comparisons of the $$gamma$$ band with collective- and shell-model calculations suggest that $$^{76}$$Ge may be a rare example of a nucleus exhibiting rigid triaxial deformation in the low-lying states.

Journal Articles

Actuator and diagnostic requirements of the ITER plasma control system

Snipes, J. A.*; Beltran, D.*; Casper, T.*; Gribov, Y.*; Isayama, Akihiko; Lister, J.*; Simrock, S.*; Vayakis, G.*; Winter, A.*; Yang, Y.*; et al.

Fusion Engineering and Design, 87(12), p.1900 - 1906, 2012/12

 Times Cited Count:25 Percentile:86.06(Nuclear Science & Technology)

no abstracts in English

Journal Articles

High-spin spectrum of $$^{24}$$Mg studied through multiple angular correlations

Diffenderfer, E. S.*; Baby, L. T.*; Santiago-Gonzalez, D.*; Ahsan, N.*; Rojas, A.*; Volya, A.*; Wiedenh$"o$ver, I.*; Wuosmaa, A. H.*; Carpenter, M. P.*; Janssens, R. V. F.*; et al.

Physical Review C, 85(3), p.034311_1 - 034311_17, 2012/03

 Times Cited Count:7 Percentile:41.42(Physics, Nuclear)

no abstracts in English

Journal Articles

Search for a 2-quasiparticle high-$$K$$ isomer in $$^{256}$$Rf

Robinson, A. P.*; Khoo, T. L.*; Seweryniak, D.*; Ahmad, I.*; Asai, Masato; Back, B. B.*; Carpenter, M. P.*; Chowdhury, P.*; Davids, C. N.*; Greene, J.*; et al.

Physical Review C, 83(6), p.064311_1 - 064311_7, 2011/06

 Times Cited Count:32 Percentile:84.92(Physics, Nuclear)

We have identified an isomer with a half-life of 17 $$mu$$s in $$^{256}$$Rf through a calorimetric conversion electron measurement tagged with implanted $$^{256}$$Rf nuclei using the fragment mass analyzer at Argonne National Laboratory. The low population yield for this isomer suggests that this isomer should not be a 2-quasiparticle high-$$K$$ isomer which is typically observed in the N = 152 isotones, but should be a 4-quasiparticle one. Possible reasons of the non-observation of a 2-quasiparticle isomer are this isomer decays by fission with a half-life similar to that of the ground state of $$^{256}$$Rf. Another possibility, that there is no 2-quasiparticle isomer at all, would imply an abrupt termination of axially symmetric deformed shape at Z=104.

Journal Articles

Cross-shell excitations near the "island of inversion"; Structure of $$^{30}$$Mg

Daecon, A. N.*; Smith, J. F.*; Freeman, S. J.*; Janssens, R. V. F.*; Carpenter, M. P.*; Hadinia, B.*; Hoffman, C. R.*; Kay, B. P.*; Lauritsen, T.*; Lister, C. J.*; et al.

Physical Review C, 82(3), p.034305_1 - 034305_7, 2010/09

 Times Cited Count:21 Percentile:77.49(Physics, Nuclear)

no abstracts in English

Journal Articles

Bridging the nuclear structure gap between stable and super heavy nuclei

Seweryniak, D.*; Khoo, T. L.*; Ahmad, I.*; Kondev, F. G.*; Robinson, A.*; Tandel, S. K.*; Asai, Masato; Back, B. B.*; Carpenter, M. P.*; Chowdhury, P.*; et al.

Nuclear Physics A, 834(1-4), p.357c - 361c, 2010/03

 Times Cited Count:7 Percentile:47.92(Physics, Nuclear)

Experimental data on single-particle energies in nuclei around Z=100 and N=152 play an important role to test validity of theoretical predictions for shell structure of superheavy nuclei. We found high-K two-quasiparticle isomers in $$^{252}$$No and $$^{254}$$No, and evaluated energies of proton single-particle orbitals around Z=100. We also found a new high-K three quasiparticle isomer in $$^{257}$$Rf. Energies of neutron single-particle orbitals were also evaluated from experimental data of the $$alpha$$ decay of $$^{257}$$Rf. Comparisons between the present experimental data and various theoretical calculations for the proton single-particle orbitals indicate that the calculation by using the Woods-Saxon potential gives the best agreement with the data.

Journal Articles

Spectroscopy of $$^{257}$$Rf

Qian, J.*; Heinz, A.*; Khoo, T. L.*; Janssens, R. V. F.*; Peterson, D.*; Seweryniak, D.*; Ahmad, I.*; Asai, Masato; Back, B. B.*; Carpenter, M. P.*; et al.

Physical Review C, 79(6), p.064319_1 - 064319_13, 2009/06

 Times Cited Count:31 Percentile:84.06(Physics, Nuclear)

$$alpha$$-, $$gamma$$-, and conversion electron spectroscopy experiments for $$^{257}$$Rf have been performed using Fragment Mass Analyzer at Argonne National Laboratory. A new isomer with a half-life of 160 $$mu$$s has been discovered in $$^{257}$$Rf, and it is interpreted as a three-quasiparticle high-$$K$$ isomer. Neutron configurations of one-quasiparticle states in $$^{253}$$No, the $$alpha$$-decay daughter of $$^{257}$$Rf, have been assigned on the basis of $$alpha$$-decay hindrance factors. Excitation energies of the 1/2$$^{+}$$[620] states in $$N$$=151 isotones indicate that the deformed shell gap at $$N$$=152 increases with the atomic number.

Journal Articles

Plasma control systems relevant to ITER and fusion power plants

Kurihara, Kenichi; Lister, J. B.*; Humphreys, D. A.*; Ferron, J. R.*; Treutterer, W.*; Sartori, F.*; Felton, R.*; Br$'e$mond, S.*; Moreau, P.*; JET-EFDA Contributors*

Fusion Engineering and Design, 83(7-9), p.959 - 970, 2008/12

 Times Cited Count:24 Percentile:81.61(Nuclear Science & Technology)

The existing large and medium-size tokamaks are expected to explore more advanced operation scenarios toward the ITER and a future power reactor. To specify one or more solutions to keep a steady-state plasma with high performance, and to avoid plasma instabilities almost completely, a plasma control system for ITER should have two important aspects: Technical inheritance of the currently-working functions, and flexible or adaptive structure. First, we make review on the system configuration and essential functions employed in each plasma control system from the viewpoint of hardware as well as software. Second, we survey ITER control system requirements for the current CODAC design. Third, flexible structure in the plasma control system should be discussed. Finally, on the basis of the above discussion, we would like to envisage a future plasma control system for ITER and a fusion power plant.

Journal Articles

$$K^{pi}=8^{-}$$ isomers and $$K^{pi}=2^{-}$$ octupole vibrations in $$N=150$$ shell-stabilized isotones

Robinson, A. P.*; Khoo, T. L.*; Ahmad, I.*; Tandel, S. K.*; Kondev, F. G.*; Nakatsukasa, Takashi*; Seweryniak, D.*; Asai, Masato; Back, B. B.*; Carpenter, M. P.*; et al.

Physical Review C, 78(3), p.034308_1 - 034308_6, 2008/09

 Times Cited Count:48 Percentile:90.59(Physics, Nuclear)

Isomers have been identified in $$^{246}$$Cm and $$^{252}$$No with quantum number $$K^{pi}=8^{-}$$, which decay through $$K^{pi}=2^{-}$$ rotational bands built on octupole vibrational states. For $$N=150$$ isotones with atomic number $$Z=94$$$$sim$$102, the $$K^{pi}=8^{-}$$ and 2$$^{-}$$ states have remarkably stable energies, indicating neutron excitations. An exception is a singular minimum in the 2$$^{-}$$ energy at $$^{246}$$Cm, due to the additional role of proton configurations.

Journal Articles

Progress in the ITER physics basis, 8; Plasma operation and control

Gribov, Y.*; Humphreys, D. A.*; Kajiwara, Ken*; Lazarus, E. A.*; Lister, J. B.*; Ozeki, Takahisa; Portone, A.*; Shimada, Michiya*; Sips, A. C. C.*; Wesley, J. C.*

Nuclear Fusion, 47(6), p.S385 - S403, 2007/06

 Times Cited Count:132 Percentile:97.49(Physics, Fluids & Plasmas)

This chapter describes the progress achieved in these areas in the tokamak experiments since the ITER Physics Basis (1999 Nucl. Fusion 39 2577) was written and the results of assessment of ITER to provide the plasma initiation and basic control. This chapter considers only plasma initiation and plasma basic control. The experiments on plasma initiation performed in DIII-D and JT-60U, as well as the theoretical studies performed for ITER, have demonstrated that, ITER can produce plasma initiation in a low toroidal electric field of 0.3V/m, if it is assisted by about 2MW of ECRF heating. The plasma basic control is described, which includes control of the plasma current, position and shape - the plasma magnetic control, as well as control of other plasma global parameters or their profiles - the plasma performance control.

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