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論文

Status of the uncertainty quantification for severe accident sequences of different NPP-designs in the frame of the H-2020 project MUSA

Brumm, S.*; Gabrielli, F.*; Sanchez-Espinoza, V.*; Groudev, P.*; Ou, P.*; Zhang, W.*; Malkhasyan, A.*; Bocanegra, R.*; Herranz, L. E.*; Berda$"i$, M.*; et al.

Proceedings of 10th European Review Meeting on Severe Accident Research (ERMSAR 2022) (Internet), 13 Pages, 2022/05

The current HORIZON-2020 project on "Management and Uncertainties of Severe Accidents (MUSA)" aims at applying Uncertainty Quantification (UQ) in the modeling of Severe Accidents (SA), particularly in predicting the radiological source term of mitigated and unmitigated accident scenarios. Within its application part, the project is devoted to the uncertainty quantification of different severe accident codes when predicting the radiological source term of selected severe accident sequences of different nuclear power plant designs, e.g. PWR, VVER, and BWR. Key steps for this investigation are, (a) the selection of severe accident sequences for each reactor design, (b) the development of a reference input model for the specific design and SA-code, (c) the selection of a list of uncertain model parameters to be investigated, (d) the choice of an UQ-tool e.g. DAKOTA, SUSA, URANIE, etc., (e) the definition of the figures of merit for the UA-analysis, (f) the performance of the simulations with the SA-codes, and, (g) the statistical evaluation of the results using the capabilities, i.e. methods and tools offered by the UQ-tools. This paper describes the project status of the UQ of different SA codes for the selected SA sequences, and the technical challenges and lessons learnt from the preparatory and exploratory investigations performed.

論文

Electromagnetic properties of low-lying states in neutron-deficient Hg isotopes; Coulomb excitation of $$^{182}$$Hg, $$^{184}$$Hg, $$^{186}$$Hg and $$^{188}$$Hg

Wrzosek-Lipska, K.*; Rezynkina, K.*; Bree, N.*; Zieli$'n$ska, M.*; Gaffney, L. P.*; Petts, A.*; Andreyev, A. N.; Bastin, B.*; Bender, M.*; Blazhev, A.*; et al.

European Physical Journal A, 55(8), p.130_1 - 130_23, 2019/08

 被引用回数:9 パーセンタイル:80.1(Physics, Nuclear)

The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass $$^{182-188}$$Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 0$$^{+}_{1,2}$$, 2$$^{+}_{1,2}$$, and 4$$^{+}_{1}$$ states was observed in all nuclei under study. Reduced $$E2$$ matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.

論文

Hydrogen at zinc vacancy of ZnO; An EPR and ESEEM study

Son, N. T.*; 磯谷 順一*; Ivanov, I. G.*; 大島 武; Janz$'e$n, E.*

AIP Conference Proceedings 1583, p.341 - 344, 2014/02

Defect centers in zinc oxide (ZnO) were investigated using electron paramagnetic resonance (EPR) techniques. Un-doped ZnO samples were irradiated with 2MeV electrons with fluence ranges between 2 and 4$$times$$10$$^{18}$$ /cm$$^{2}$$ at room temperature. As a result of EPR measurements, the spectrum, labeled S1, with small-splitting doublet accompanied by weak satellites was observed. The obtained structure is shown to be the hyperfine structure because of the dipolar interaction between an unpaired electron spin and a nuclear spin of hydrogen (H). The presence of H atom in S1 was confirmed from the observation of the nuclear Zeeman frequency of H in electron spin echo envelope modulation experiments. Considering the observed spin-Hamiltonian parameters, S1 was identified to be the partly H-passivated Zn vacancy, V$$_{Zn}$$$$^{-}$$H$$^{+}$$, with the H$$^{+}$$ ion making a short O-H bond with only one nearest O neighbor of V$$_{Zn}$$ in the basal plane, being off the substitutional site, while the unpaired electron spin, by which the observed EPR signal increased, was localized on the p orbital of another O neighbor also in the basal plane.

論文

Magnetic resonance studies of defects in electron-irradiated ZnO substrates

Son, N. T.*; Ivanov, I. G.*; Kuznetsov, A. Yu.*; Svensson, B. G.*; Zhao, Q. X.*; Willander, M.*; 森下 憲雄; 大島 武; 伊藤 久義; 磯谷 順一*; et al.

Physica B; Condensed Matter, 401-402, p.507 - 510, 2007/12

 被引用回数:3 パーセンタイル:18.6(Physics, Condensed Matter)

酸化亜鉛(ZnO)中の欠陥の挙動を解明するために、3又は6MeV電子線照射を行ったZnOの光検知磁気共鳴(ODMR)評価を行った。その結果、浅いドナー及びZu空孔に起因するシグナルに加え、スピン1/2を有する幾つかのシグナルが観測され、このうち、LU3及びLU4とラベル付けされたシグナルがキャリアの再結合中心として働くことが判明した。また、400$$^{circ}$$Cまでの熱処理後もLU3,LU4は安定に存在することも併せて明らかとなった。

口頭

Deep levels in electron irradiated semi-insulating 4H-SiC; Electronic, optical and structural observation

中根 浩貴*; 加藤 正史*; 市村 正也*; 大島 武; Ivanov, I. G.*; Trinh, X. T.*; Son, N. T.*; Janz$'e$n, E.*

no journal, , 

Deep level defects in Silicon Carbide (SiC) were studied using photo-induced current transient spectroscopy (PICTS), electron paramagnetic resonance (EPR) and photoluminescence (PL). Deep levels were introduced into high-purity semi insulating 4H-SiC samples by 2 MeV-electron irradiation. After the electron irradiation, the samples were annealed between 200 and 1000 $$^{circ}$$C. In the samples annealed at 400 $$^{circ}$$C or higher temperatures, we observed six different peaks from PICTS measurements. We labeled these peaks as a, b, c, d, e and f. As a result of the dependence of the peak heights on annealing temperature, the heights of all peaks increase monotonically with annealing temperature. In our previous report, we observed peaks labeled as A and B, which were speculated to be related to C$$_{Si}$$V$$_{C}$$ and the EI4 center identified by EPR. Peak temperatures and annealing behavior of peaks A and B are similar to those of peaks d and f, respectively, while other peaks a, b, c and e were not observed in our previous studies. The PL peaks at 433 and 442 nm were observed in all the studied samples, whereas peaks at 428 and 429 nm were observed in the samples annealed above 200 $$^{circ}$$C, and a peak at 427 nm was observed in samples annealed above 400 $$^{circ}$$C. Considering the annealing temperature dependence of the PICTS and PL peaks, the PL peak at 427 nm may correspond to either one of PICTS peaks a, b, d, e, and f.

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