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Journal Articles

Evaluation of light-element reactions in the resolved resonance region

Dimitriou, P.*; Chen, Z.*; deBoer, R. J.*; Hale, G.*; Kunieda, Satoshi; Leeb, H.*; Paris, M.*; Pigni, M. T.*; Srdinko, Th.*; Tamagno, P.*; et al.

EPJ Web of Conferences, 284, p.03002_1 - 03002_5, 2023/05

Charged-particle-induced reactions at low energies in the resolved resonance region are important for applications such as ion beam analysis of materials and management of the nuclear fuels. However, the evaluated nuclear data libraries maintained by national or international coordinated efforts (ENDF, JEFF, JENDL, CENDL) are to date, incomplete as far as charged-particle- induced reactions in the resolved resonance region are concerned. The IAEA Nuclear Data Section is coordinating an international effort to (i) verify that the existing R-matrix codes are consistent, (ii) evaluate charged-particle cross sections in the resolved resonance region, (iii) produce evaluated nuclear data files for further processing and finally (iv) disseminate the evaluated data through general purpose evaluated nuclear data libraries. We present the results of the effort made thus far on (1) verification of the available R-matrix codes, minimization methods and calculation of covariances, (2) the evaluation of the compound system $$^7$$Be*, and (3) improving $$(alpha,n)$$ reaction data for the applications.

Journal Articles

CIELO collaboration summary results; International evaluations of neutron reactions on uranium, plutonium, iron, oxygen and hydrogen

Chadwick, M. B.*; Capote, R.*; Trkov, A.*; Herman, M. W.*; Brown, D. A.*; Hale, G. M.*; Kahler, A. C.*; Talou, P.*; Plompen, A. J.*; Schillebeeckx, P.*; et al.

Nuclear Data Sheets, 148, p.189 - 213, 2018/02

 Times Cited Count:61 Percentile:98.12(Physics, Nuclear)

The CIELO collaboration has studied neutron cross sections on nuclides that significantly impact criticality in nuclear facilities - $$^{235}$$U, $$^{238}$$U, $$^{239}$$Pu, $$^{56}$$Fe, $$^{16}$$O and $$^{1}$$H - with the aim of improving the accuracy of the data and resolving previous discrepancies in our understanding. This multi-laboratory pilot project, coordinated via the OECD/NEA Working Party on Evaluation Cooperation (WPEC) Subgroup 40 with support also from the IAEA, has motivated experimental and theoretical work and led to suites of new evaluated libraries that accurately reflect measured data and also perform well in integral simulations of criticality. This report summarizes our results and outlines plans for the next phase of this collaboration.

Journal Articles

The CIELO collaboration; Progress in international evaluations of neutron reactions on Oxygen, Iron, Uranium and Plutonium

Chadwick, M. B.*; Capote, R.*; Trkov, A.*; Kahler, A. C.*; Herman, M. W.*; Brown, D. A.*; Hale, G. M.*; Pigni, M.*; Dunn, M.*; Leal, L.*; et al.

EPJ Web of Conferences, 146, p.02001_1 - 02001_9, 2017/09

 Times Cited Count:6 Percentile:95.25

The CIELO collaboration has studied neutron cross sections on nuclides ($$^{16}$$O, $$^{56}$$Fe, $$^{235,238}$$U and $$^{239}$$Pu) that significantly impact criticality in nuclear technologies with the aim of improving the accuracy of the data and resolving previous discrepancies in our understanding. This multi-laboratory pilot project, coordinated via the OECD/NEA Working Party on Evaluation Cooperation (WPEC) Subgroup 40 with support also from the IAEA, has motivated experimental and theoretical work and led to suites of new evaluated libraries that accurately reflect measured data and also perform well in integral simulations of criticality.

Journal Articles

Toward advancement of nuclear data research in the resonance region

Kunieda, Satoshi; Shibata, Keiichi; Fukahori, Tokio; Kawano, Toshihiko*; Paris, M.*; Hale, G.*

JAEA-Conf 2015-003, p.33 - 38, 2016/03

We present recent progress of nuclear data evaluation method in the resolved resonance range. Our multi-channel R-matrix code now includes photon-channel and computational capability of charged-particle elastic scattering. We also present the physical constraint from the theory in the analysis of experimental data. Example analysis results are shown for $$^8$$Be and $$^{17}$$O compound system. Finally, perspectives are discussed toward the advancement of nuclear data in the resonance region including those for medium-heavy nuclei.

Journal Articles

Covariance of neutron cross sections for $$^{16}$$O through R-matrix analysis

Kunieda, Satoshi; Kawano, Toshihiko*; Paris, M.*; Hale, G. M.*; Shibata, Keiichi; Fukahori, Tokio

Nuclear Data Sheets, 123, p.159 - 164, 2015/01

 Times Cited Count:5 Percentile:42.17(Physics, Nuclear)

The collision matrix in the R-matrix theory is unitary, hence theory brings strong constraints to behavior of the parameters. An unitarity-imposed R-matrix analysis is carried out for $$^{17}$$O system to evaluate $$^{16}$$O neutron cross-sections in the resolved resonance range. Covariance matrices are also estimated both for the cross-sections and angular distributions with a deterministic method. Present results mirror the nature in the theory as well as experimental information.

Journal Articles

Estimation of neutron cross-sections for $$^{16}$$O up to 5.2 MeV through R-matrix analysis

Kunieda, Satoshi; Kawano, Toshihiko*; Paris, M.*; Hale, G. M.*; Shibata, Keiichi; Fukahori, Tokio

NEA/NSC/DOC(2014)13 (Internet), p.33 - 39, 2014/07

There still remain differences among measured data, which makes the evaluated cross-sections uncertain, and which consequently affects some integral calculation. $$^{16}$$O is one of the important nuclei in the nuclear application, but such kinds of issues appears in elastic-scattering and (n,$$alpha$$) reaction cross-sections. Purpose of this study is to solve those issues as they are common concerns in the world. We present estimated cross sections and their covariance data which are "physically" constrained by the R-matrix theory. The differences between the estimated and the measured cross-sections will be also discussed.

Journal Articles

R-matrix analysis for n + $$^{16}$$O cross-sections up to E$$_{rm n}$$ = 6.0 MeV with covariances

Kunieda, Satoshi; Kawano, Toshihiko*; Paris, M.*; Hale, G. M.*; Shibata, Keiichi; Fukahori, Tokio

Nuclear Data Sheets, 118, p.250 - 253, 2014/04

 Times Cited Count:10 Percentile:62.99(Physics, Nuclear)

Oxygen is one of the most important materials in nuclear applications. However, there are big discrepancies among experimental and evaluated data in $$^{16}$$O($$n,alpha$$) cross section. Also, there are increasing demands for giving uncertainties in evaluated cross section to estimate the margin of integral calculations. We analyzed experimental cross sections with R-matrix theory, and estimated cross sections with their uncertainties. In this analysis, not only the neutron but also an inverse reactions were included. The systematic uncertainties were also considered for each measurement. The resulting cross sections and uncertainties mirror both experimental and theoretical knowledges.

Oral presentation

Development of R-matrix code and neutron cross sections for O-16 with covariance

Kunieda, Satoshi; Shibata, Keiichi; Fukahori, Tokio; Kawano, Toshihiko*; Paris, M.*; Hale, G. M.*

no journal, , 

Light nuclei are used as the moderator, coolant and reflector in the reactors. Also, they are main constituents of human body. Therefore it is important to evaluate neutron cross sections and their covariances for those nuclei for reactor engineering and radiotherapy. In this study, we developed a multichannel R-Matrix code to estimate the cross sections and covariances in the resonance region. The code also has functions for parameter search and covariance estimation from experimental cross sections. In the presentation, we will show main features of our R-matrix code and example results for O-16.

Oral presentation

Application of R-matrix theory to cross-section evaluation for light nuclei

Kunieda, Satoshi; Shibata, Keiichi; Fukahori, Tokio; Kawano, Toshihiko*; Paris, M.*; Hale, G. M.*

no journal, , 

The collision matrix calculated from the R-matrix theory is the unitary. Hence the theory brings physical constraints to the analysis of measured cross-sections. That means it may reduce some inconsistencies in the present experimental and evaluated data. The unitarity constraint analysis was carried out for the cross-section evaluation for O-16. We confirmed that the calculated differential cross-sections were also consistent with measured values.

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