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JAEA Reports

Influence of fuel assembly loading pattern and fuel burnups upon leakage neutron flux spectra from light water reactor core (Joint research)

Kojima, Kensuke; Okumura, Keisuke; Kosako, Kazuaki*; Torii, Kazutaka*

JAEA-Research 2015-019, 90 Pages, 2016/01

JAEA-Research-2015-019.pdf:1.95MB

At the decommissioning of light water reactors (LWRs), it is important to evaluate an amount of radioactivity in the ex-core structures such as a reactor containment vessel, radiation shieldings, and so on. It is thought that the leakage neutron spectra in these radioactivation regions, which strongly affect the induced radioactivity, would be changed by different reactor core configurations such as fuel assembly loading pattern and fuel burnups. This study was intended to evaluate these effects. For the purpose, firstly, partial neutron currents on the core surfaces were calculated for some core configurations. Then, the leakage neutron flux spectra in major radioactivation regions were calculated based on the provided currents. Finally, influence of the core configurations upon the neutron flux spectra was evaluated. As a result, it has been found that the influence is small on the spectrum shapes of neutron fluxes. However, it is necessary to pay attention to the facts that intensities of the leakage neutron fluxes are changed by the configurations and that intensities and spectrum shapes of the leakage neutron fluxes are changed depending on the angular direction around the core.

Journal Articles

Ground-state configuration of the $$N=157$$ nucleus $$^{259}$$No

Asai, Masato; Tsukada, Kazuaki; Sakama, Minoru*; Haba, Hiromitsu*; Ichikawa, Takatoshi*; Ishii, Yasuo; Toyoshima, Atsushi; Ishii, Tetsuro; Nishinaka, Ichiro; Nagame, Yuichiro; et al.

Physical Review C, 87(1), p.014332_1 - 014332_6, 2013/01

 Times Cited Count:6 Percentile:45.91(Physics, Nuclear)

The spin-parity and neutron configuration of the ground state of $$^{259}$$No have been identified through $$alpha$$-decay spectroscopy. The $$^{259}$$No is the nucleus with the largest neutron number whose spin-parities and single-particle configurations have ever been identified. The neutron 9/2$$^{+}$$[615] configuration was assigned to the ground state of $$^{259}$$No as well as to the 231.4 keV level in $$^{255}$$Fm. This allowed us to establish energy spacings and order of the neutron single-particle orbitals in such heaviest nuclear region. The appearance of the 9/2$$^{+}$$[615] ground state at $$N$$=157 implies that the order of the neutron orbitals between the $$N$$=152 and 162 deformed shell gaps should change considerably with increasing neutron number.

Journal Articles

Neutron one-quasiparticle states in $$^{251}$$Fm$$_{151}$$ populated via the $$alpha$$ decay of $$^{255}$$No

Asai, Masato; Tsukada, Kazuaki; Haba, Hiromitsu*; Ishii, Yasuo; Ichikawa, Takatoshi*; Toyoshima, Atsushi; Ishii, Tetsuro; Nagame, Yuichiro; Nishinaka, Ichiro; Kojima, Yasuaki*; et al.

Physical Review C, 83(1), p.014315_1 - 014315_12, 2011/01

 Times Cited Count:20 Percentile:76.66(Physics, Nuclear)

Excited states in $$^{251}$$Fm populated via the $$alpha$$ decay of $$^{255}$$No are studied in detail through $$alpha$$-$$gamma$$ coincidence and $$alpha$$ fine structure measurements. Spin-parities and neutron configurations of the excited states in $$^{251}$$Fm as well as the ground state of $$^{255}$$No are definitely identified on the basis of deduced internal conversion coefficients, lifetimes of $$gamma$$ transitions, rotational-band energies built on one-quasiparticle states, and hindrance factors of $$alpha$$ transitions. It is found that the excitation energy of the 1/2$$^{+}$$[620] state in $$N$$=151 isotones increases with the atomic number, especially at $$Z$$$$ge$$100, while that of the 1/2$$^{+}$$[631] state decreases at $$Z$$=100. Energy systematics of the one-quasiparticle states in the $$N$$=151 isotones are discussed in terms of the evolution of nuclear deformation involving the hexadecapole and hexacontatetrapole deformations.

Journal Articles

$$Q_{beta}$$ measurements of $$^{158,159}$$Pm, $$^{159,161}$$Sm, $$^{160-165}$$Eu, $$^{163}$$Gd and $$^{166}$$Tb using a total absorption BGO detector

Hayashi, Hiroaki*; Akita, Yukinori*; Suematsu, Osamu*; Shibata, Michihiro*; Asai, Masato; Sato, Tetsuya; Ichikawa, Shinichi; Nishinaka, Ichiro; Nagame, Yuichiro; Osa, Akihiko; et al.

European Physical Journal A, 34(4), p.363 - 370, 2007/12

 Times Cited Count:16 Percentile:72.38(Physics, Nuclear)

$$Q_{beta}$$ values of $$^{160-165}$$Eu and $$^{163}$$Gd were measured for the first time using a total absorption BGO detector, and the data of $$^{158,159}$$Pm, $$^{159,161}$$Sm, and $$^{166}$$Tb obtained previously were reanalyzed. These nuclei were produced by the proton-induced fission of $$^{238}$$U at the JAEA-Tokai tandem accelerator facility, and separated from the reaction products using an on-line isotope separator. The deduced mass excesses and two-neutron separation energies were compared with those of atomic mass evaluations and theoretical predictions.

Journal Articles

$$alpha$$ decay of $$^{238}$$Cm and the new isotope $$^{237}$$Cm

Asai, Masato; Tsukada, Kazuaki; Ichikawa, Shinichi; Sakama, Minoru*; Haba, Hiromitsu*; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi*; Kojima, Yasuaki*; Oura, Yasuji*; et al.

Physical Review C, 73(6), p.067301_1 - 067301_4, 2006/06

 Times Cited Count:21 Percentile:77.09(Physics, Nuclear)

no abstracts in English

Journal Articles

$$beta$$-decay half-lives of new neutron-rich rare-earth isotopes $$^{159}$$Pm, $$^{162}$$Sm, and $$^{166}$$Gd

Ichikawa, Shinichi; Asai, Masato; Tsukada, Kazuaki; Haba, Hiromitsu*; Nagame, Yuichiro; Shibata, Michihiro*; Sakama, Minoru*; Kojima, Yasuaki*

Physical Review C, 71(6), p.067302_1 - 067302_4, 2005/06

 Times Cited Count:18 Percentile:75.05(Physics, Nuclear)

The new neutron-rich raer-earth isotopes $$^{159}$$Pm, $$^{162}$$Sm, and $$^{166}$$Gd produced in the proton-induced fission of 238U were identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport sysetm. The half-lives of $$^{159}$$Pm, $$^{162}$$Sm, and $$^{166}$$Gd were determined to be 1.5$$pm$$0.2s, 2.4$$pm$$0.5s, and 4.8$$pm$$1.0s, respectively. The partial decay scheme of $$^{166}$$Gd wes constructed for $$gamma$$-$$gamma$$ coincidence data. The improved half-life values of 25.6$$pm$$2.2s wes obtained for the previously identified isotope $$^{166}$$Tb. The half-lives measured in the present study are in good agreement with the theoretical predictions calculated by the second generation of the gross theory with the atomic masses evaluated by the Audei and Wapstra.

Journal Articles

Proton-neutron configurations in $$^{236g,m}$$Am and its EC-decay daughter $$^{236}$$Pu

Asai, Masato; Sakama, Minoru*; Tsukada, Kazuaki; Ichikawa, Shinichi; Haba, Hiromitsu*; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi*; Kojima, Yasuaki*; Oura, Yasuji*; et al.

European Physical Journal A, 23(3), p.395 - 400, 2005/02

 Times Cited Count:13 Percentile:64.99(Physics, Nuclear)

The EC decay of $$^{236}$$Am has been studied through $$gamma$$-ray spectroscopy. Two EC-decaying states have been found in $$^{236}$$Am with half-lives of 3.6 min and 2.9 min. In $$^{236}$$Pu, we have found the $$K^{pi}=0^{-}$$ octupole band and two-quasiparticle states one of which is a $$K$$ isomer with a 1.2 $$mu$$s half-life. The EC transitions from $$^{236g,m}$$Am to the two-quasiparticle states in $$^{236}$$Pu show small $$log ft$$ values of 4.8--5.3, which allowed us to assign proton-neutron configurations of $$^{236g,m}$$Am and the two-quasiparticle states.

Journal Articles

EC and $$alpha$$ decays of $$^{235}$$Am

Asai, Masato; Sakama, Minoru*; Tsukada, Kazuaki; Ichikawa, Shinichi; Haba, Hiromitsu*; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi*; Kojima, Yasuaki*; Oura, Yasuji*; et al.

European Physical Journal A, 22(3), p.411 - 416, 2004/12

 Times Cited Count:8 Percentile:48.95(Physics, Nuclear)

EC and $$alpha$$ decays of $$^{235}$$Am have been studied by means of $$gamma$$-ray spectroscopy. Excited states in $$^{235}$$Pu have been established for the first time, and tentative spin-parity and Nilsson assignments were given to these levels. The ground state of $$^{235}$$Am was evaluated to be the $$pi 5/2^{-}[523]$$ state from the experimental results. It was found that the $$pi 5/2^{-}[523]$$ state in $$^{231}$$Np is located at $$<$$15~keV, which allowed us to determine the $$Q_{alpha}$$ value of $$^{235}$$Am as 6569$$^{+27}_{-12}$$~keV, in combination with the measured $$alpha$$-particle energy.

Journal Articles

$$alpha$$-decays of neutron-deficient americium isotopes

Sakama, Minoru*; Asai, Masato; Tsukada, Kazuaki; Ichikawa, Shinichi; Nishinaka, Ichiro; Nagame, Yuichiro; Haba, Hiromitsu*; Goto, Shinichi*; Shibata, Michihiro*; Kawade, Kiyoshi*; et al.

Physical Review C, 69(1), p.014308_1 - 014308_11, 2004/01

 Times Cited Count:19 Percentile:72.32(Physics, Nuclear)

no abstracts in English

Journal Articles

$$gamma$$-ray spectroscopy for neutron-rich A$$approx$$160-170 nuclei; The $$beta^{-}$$ decay of $$^{159}$$Pm, $$^{160-162}$$Sm, $$^{162}$$Eu, $$^{164-166}$$Gd, and $$^{166-168}$$Tb

Asai, Masato; Ichikawa, Shinichi; Tsukada, Kazuaki; Osa, Akihiko; Nishinaka, Ichiro; Nagame, Yuichiro; Kojima, Yasuaki*; Shibata, Michihiro*

Fission and Properties of Neutron-Rich Nuclei; Proceedings of 3rd International Conference, p.227 - 232, 2003/10

Structure of neutron-rich A$$approx$$160-170 nuclei produced in the proton-induced fission has been studied through $$gamma$$-ray spectroscopy using an on-line isotope separator. $$beta^{-}$$ decays of $$^{159}$$Pm, $$^{161,162}$$Sm, and $$^{165,166}$$Gd have been observed for the first time, and their half-lives were determined. Excited states of their daughter nuclei were revealed. $$gamma$$ rays following the $$beta^{-}$$ decay of $$^{162}$$Eu and $$^{164}$$Gd have been also observed. The results suggest that the ground state of $$^{162}$$Eu would have a spin 5 or 6.

Journal Articles

Identification of the new isotope $$^{241}$$Bk

Asai, Masato; Tsukada, Kazuaki; Ichikawa, Shinichi; Sakama, Minoru*; Haba, Hiromitsu*; Nagame, Yuichiro; Nishinaka, Ichiro; Akiyama, Kazuhiko; Toyoshima, Atsushi; Kaneko, Tetsuya*; et al.

European Physical Journal A, 16(1), p.17 - 19, 2003/01

 Times Cited Count:8 Percentile:50.92(Physics, Nuclear)

The new isotope $$^{241}$$Bk has been identified for the first time using a gas-jet coupled on-line isotope separator at the JAERI tandem accelerator facility. Characteristic X rays and three $$gamma$$ transitions associated with the EC decay of $$^{241}$$Bk have been observed, and the half-life was determined to be 4.6 min. The half-life value and the observed $$gamma$$-ray energies and intensities can be consistently explained as a consequence of the allowed EC transition of $$pi 7/2^{+}[633]$$ $$rightarrow$$ $$nu 7/2^{+}[624]$$.

Journal Articles

Nuclear decay properties of the neutron-deficient actinides

Sakama, Minoru*; Tsukada, Kazuaki; Asai, Masato; Ichikawa, Shinichi; Haba, Hiromitsu; Goto, Shinichi*; Nishinaka, Ichiro; Nagame, Yuichiro; Oura, Yasuji*; Kojima, Yasuaki*; et al.

Journal of Nuclear Science and Technology, 39(Suppl.3), p.34 - 37, 2002/11

no abstracts in English

Journal Articles

Measurements of EC and weak $$alpha$$ decays of neutron-deficient transuranium isotopes

Asai, Masato; Sakama, Minoru; Tsukada, Kazuaki; Ichikawa, Shinichi; Haba, Hiromitsu; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi; Kojima, Yasuaki*; Oura, Yasuji*; et al.

Journal of Nuclear Science and Technology, 39(Suppl.2), p.474 - 477, 2002/08

Neutron-deficient americium and curium isotopes with half-lives $$leq$$10 min have been produced with the tandem accelerator, and their EC and weak $$alpha$$ decays have been successfully measured through an on-line isotope separation. Decay schemes of $$^{235,236}$$Am have been established, and proton-neutron configurations in the parent and daughter nuclei have been determined. Observed $$alpha$$ transitions in $$^{233,235}$$Am were found to be the favored transitions between the $$pi 5/2^{-}[523]$$ Nilsson states. Information on nuclear structure, deformation, and atomic masses in this region were obtained.

Journal Articles

Decay studies of neutron-deficient Am, Cm, and Bk nuclei using an on-line isotope separator

Asai, Masato; Sakama, Minoru*; Tsukada, Kazuaki; Ichikawa, Shinichi; Haba, Hiromitsu; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi*; Akiyama, Kazuhiko; Toyoshima, Atsushi; et al.

Journal of Nuclear and Radiochemical Sciences, 3(1), p.187 - 190, 2002/06

EC and $$alpha$$ decays of neutron-deficient americium, curium, and berkelium nuclei have been studied using the JAERI on-line isotope separator. Decay schemes of $$^{235, 236}$$Am have been established for the first time, and proton-neutron configurations in $$^{235, 236}$$Am and $$^{235, 236}$$Pu have been determined. $$alpha$$ transitions observed in $$^{233, 235}$$Am were found to be the favored transitions between the $$pi 5/2^{-}[523]$$ Nilsson states. $$Q_{alpha}$$ values of $$^{237, 238}$$Cm have been determined. Nuclear structure, deformation, and atomic masses for these nuclei were discussed.

Journal Articles

Performance of the multiple target He/PbI$$_{2}$$ aerosol jet system for mass separation of neutron-deficient actinide isotopes

Ichikawa, Shinichi; Tsukada, Kazuaki; Asai, Masato; Haba, Hiromitsu; Sakama, Minoru*; Kojima, Yasuaki*; Shibata, Michihiro*; Nagame, Yuichiro; Oura, Yasuji*; Kawade, Kiyoshi*

Nuclear Instruments and Methods in Physics Research B, 187(4), p.548 - 554, 2002/04

 Times Cited Count:14 Percentile:66.86(Instruments & Instrumentation)

no abstracts in English

Journal Articles

New isotope $$^{233}$$Am

Sakama, Minoru*; Tsukada, Kazuaki; Asai, Masato; Ichikawa, Shinichi; Haba, Hiromitsu; Goto, Shinichi*; Oura, Yasuji*; Nishinaka, Ichiro; Nagame, Yuichiro; Shibata, Michihiro*; et al.

European Physical Journal A, 9(3), p.303 - 306, 2000/11

 Times Cited Count:16 Percentile:65.41(Physics, Nuclear)

no abstracts in English

Journal Articles

Spectroscopic studies of mass-separated heavy nuclei

Asai, Masato; Sakama, Minoru*; Tsukada, Kazuaki; Ichikawa, Shinichi; Haba, Hiromitsu; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi*; Kojima, Yasuaki*; Oura, Yasuji*; et al.

AIP Conference Proceedings 561, p.358 - 367, 2000/09

no abstracts in English

Journal Articles

Decay studies of neutron-rich isotopes produced in proton-induced fission of actinides

Ichikawa, Shinichi; Asai, Masato*; Tsukada, Kazuaki; Nishinaka, Ichiro; Nagame, Yuichiro; Osa, Akihiko; Shibata, Michihiro*; Kawade, Kiyoshi*; Kojima, Yasuaki*; Sakama, Minoru*; et al.

Proceedings of 2nd International Conference on Fission and Neutron-rich Nuclei, p.203 - 205, 2000/03

no abstracts in English

Journal Articles

$$beta$$-decay half-lives of new neutron-rich isotopes of elements from Pm to Tb

Ichikawa, Shinichi; Asai, Masato*; Tsukada, Kazuaki; Osa, Akihiko; Sakama, Minoru*; Kojima, Yasuaki*; Shibata, M.*; Nishinaka, Ichiro; Nagame, Yuichiro; Oura, Yasutsugu*; et al.

AIP Conference Proceedings 495, p.103 - 106, 1999/12

no abstracts in English

Journal Articles

Recent studies of unstable nuclei far from stability with the on-line isotope separators of JAERI

Sekine, Toshiaki; Ichikawa, Shinichi; Osa, Akihiko; Koizumi, Mitsuo; Iimura, Hideki; Tsukada, Kazuaki; Nishinaka, Ichiro; Hatsukawa, Yuichi; Nagame, Yuichiro; Asai, Masato*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 239(1), p.127 - 131, 1999/00

 Times Cited Count:2 Percentile:21.63(Chemistry, Analytical)

no abstracts in English

37 (Records 1-20 displayed on this page)